ECONOMIC ZOOLOGY
AND ENTOMOLOGY

KELLOGt AND DOANE

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BY THE SAME AUTHORS
BY VERNON LYMAN KELLOGG

ELEMENTARY ZOOLOGY

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THE ANIMALS AND MAN

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BY RENNIE WILBUR DOANE

INSECTS AND DISEASE

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ELEMENTARY TEXTBOOK OF

ECONOMIC ZOOLOGY

AND

ENTOMOLOGY

BY

VERNON LYMAN KELLOGG

PROFESSOR OF ENTOMOLOGY AND LECTURER IN BIONOMICS
IN STANFORD UNIVERSITY

AND

RENNIE WILBUR DOANE

ASSISTANT PROFESSOR OF ECONOMIC ENTOMOLOGY
IN STANFORD UNIVERSITY

NEW YORK
HENRY HOLT AND COMPANY

COPYRIGHT, 1915

BY
HENRY HOLT AND COMPANY

THE. MAPLE PRESS. Y O R K P A

PREFATORY NOTE

The point of view from which this book is written is explained
in its first chapter. For that matter it is indicated clearly by
the title. If the study of zoology is being neglected in schools
for the alleged reason that it is not a useful study, the neglect
is based on an unsound reason. For zoology is useful, and not
in one way alone, but in two ways; and both of these in addition
to its pedagogic value as a study which develops accurate per-
sonal observation and independent personal attainment of
conclusion.

Zoology is first of all useful in the way so often stressed by
Huxley, as a study that gives us a sounder basis for our own
life by showing the demands of Nature on animal life in general
and the kinds of responses to be made to these demands. In
other words it is quite specially a branch of science that can
help us largely as a guide to living in conformity to natural
laws. Zoology is also useful in a more obvious and commerci-
ally ratable way, by revealing the precise relation which many
animals bear to us in their attitude of friends to be cultivated,
or foes to be fought. Injurious insects, alone, cause this
country an annual loss of a billion dollars. A general knowl-
edge of insect life and an intelligent and vigorous application
of this knowledge can save the nation half this loss.

To the teacher intending to use this book as class guide there
is due a word of explanation. The authors have attempted to
make the book an introduction to general zoology as well as
to that specific phase of it called economic. The first chapters
are therefore of a nature to introduce pupils to general facts of
animal structure and life. They are arranged on the basis of ac-
cepted pedagogic principles. The later chapters, arranged on
a basis of animal classification, proceeding from the simpler to
the more highly developed groups, include not only general facts

vii

viii PREFATORY NOTE

pertaining to the groups treated, but introduce and give special
attention to the economic relations of various particular mem-
bers of the groups. Finally in still later chapters, segregated
in a separate section of the book, there is presented a sort of
encyclopedic treatment of a considerable body of facts wholly
economic in aspect. These chapters are to be used as reference
matter, collateral reading, and matter to suggest practical
work, rather than as material for recitation. Of the numerous
insect kinds treated in the chapters on injurious insects, only a
certain few will be found in any single region. Those few are
the ones intended for study by pupils in that region. The
study should be mostly field work.

We wish to thank Professor Harold Heath for his kindly
critical reading of much of the manuscript of the book. The
sources of such illustrations as are not original with us are
pointed out in the subscriptions to the figures. We owe thanks
to many friends in this connection.

V. L. K.
R. W. D.

STANFORD UNIVERSITY, CALIFORNIA,

December, 1914.

CONTENTS

PART I

CHAPTER PAGE

I. ANIMALS AND THE STUDY OF ANIMALS .... i

II. A STUDY OF 'THE FROG 4

III. A STUDY OF THE GRASSHOPPER 14

IV. A STUDY OF HYDRA 21

V. A STUDY OF AMCEBA 25

VI. THE ONE-CELLED ANIMALS 29

VII. ONE-CELLED AND MANY-CELLED ANIMALS ... 39

VIII. THE CLASSIFICATION OF ANIMALS 48

IX. SPONGES AND SPONGE FISHING 58

X. SEA-ANEMONES, JELLY-FISHES, CORALS AND CORAL

ISLANDS 63

XL LIVER-FLUKES, TAPE-WORMS, AND OTHER PARA-
SITIC FLAT-WORMS 69

XII. TRICHINAE, HOOKWORMS, FILARIA, AND OTHER

PARASITIC ROUND WORMS 79

XIII. STARFISHES, SEA-URCHINS, AND SEA-CUCUMBERS . 89

XIV. EARTHWORMS, LEECHES, AND OTHER SEGMENTED

WORMS 98

XV. CRAYFISH, LOBSTERS, CRABS, SHRIMPS, ETC. . . 106

XVI. SLIME SLUGS, MYRIAPODS AND INSECTS .... 123
XVII. CLASSIFICATION OF INSECTS, AND INSECT BENEFITS

AND INJURIES 153

XVIII. INSECTS (CONT'D) WASPS, ANTS, THE HONEY BEE

AND OTHER BEES 183

XIX. SCORPIONS, SPIDERS, MITES AND TICKS .... 206
XX. OYSTERS, CLAMS, MUSSELS, OTHER MOLLUSCS, AND

THE SHELLFISH INDUSTRIES 216

XXI. FISHES AND FISHERIES 237

XXII. TOADS, FROGS AND SALAMANDERS . . . . . 256

XXIII. SNAKES, LIZARDS, TURTLES, AND CROCODILES . . 260

XXIV. BIRDS. 273

XXV. MAMMALS 295

ix

CONTENTS

CHAPTER

XXVI. DOMESTICATED ANIMALS .
XXVII. ANIMAL LIFE AND EVOLUTION.

PAGE
321

335

PART II

XXVIII. PARASITIC PROTOZOA CAUSING DISEASES OF MAN

AND ANIMALS 349

XXIX. INSECTS AND DISEASE 367

XXX. OTHER INSECTS AFFECTING MAN AND DOMESTIC

ANIMALS 386

XXXI. CONTROLLING INSECT PESTS 403

XXXII. INSECTS INJURIOUS TO ORCHARD TREES. . . .421

XXXIII. INSECTS AFFECTING CITRUS FRUITS 450

XXXIV. INSECTS INJURIOUS TO VINEYARDS AND BERRIES . 462
XXXV. INSECTS INJURIOUS TO GARDEN TRUCK .... 475

XXXVI. INSECTS AFFECTING FIELD AND FORAGE CROPS. . 489

XXXVII. INSECTS INJURIOUS TO FOREST AND SHADE TREES. 506

ECONOMIC ZOOLOGY AND ENTOMOLOGY

PART I

CHAPTER I
ANIMALS, AND THE STUDY OF ANIMALS

Many books about animals begin with a definition of an
animal. As a matter of fact animals cannot be precisely
defined. At the bottom of the animal scale are many very
small, very simple creatures that are so like certain other very
small and very simple creatures which are usually classified as
plants, that one cannot state in precise words just what dis-
tinguishes the so-called animals from the so-called plants.
But the experience that everyone of us has from knowing
dogs, horses, birds and butterflies, and trees, bushes, flowers
and weeds, will serve to make us recognize the major and usual
distinctions between most animals and plants. The free
locomotion, the sense organs, nervous system and sensitive-
ness, the need of already living or once living substances for
food, the large intake of oxygen and out-pouring of carbon
dioxide of most animals, contrasted with the fixity, the lack of
sense organs and nervous system, the use of inorganic sub-
stances for food, and the large intake of carbon dioxide and out-
pouring of oxygen of most plants, are distinctions made familiar
by our common experiences.

This common observation and experience enables us, also,
to distinguish with practical certainty between all living and
all non-living things, although the modern study of biology is
moving along lines that make it more and more nearly impos-
sible to tell accurately in words just what distinguishes so-
called living or organic nature from so-called non-living or
inorganic nature. In fact almost the only remaining positive
criterion of living matter is the inevitable presence in it of
certain complex chemical compounds called proteins. These

2 ECONOMIC ZOOLOGY AND ENTOMOLOGY

are wholly wanting in inorganic matter. Practically none of
the other distinctions usually given will stand close scrutiny
and critical analysis.

A recent estimate by a reliable naturalist of the number of
known kinds of animals puts this number at 522,400. It is
quite certain that there are as many more not yet known. Of
these million living animal kinds each of us knows but few,
some of us very few indeed. And these few we usually know
most superficially; usually only their general external appear-
ance and a little about their habits. Yet this little that we
know about animals is sufficient to serve as an introduction to
the science of zoology, if we will think seriously of it and try
to arrange it in some orderly or classified way. That indeed
is what the whole science of zoology is; an orderly arrangement
of all the known facts about animals.

This arrangement usually begins by a grouping of the facts
under five principal heads. These are animal classification, or
systematic zoology; animal morphology, or structural zoology;
animal physiology, or functional zoology; animal embryology
and life-history, or developmental zoology; and animal rela-
tions to their environment, or ecological zoology. Animal
psychology or behavior is also sometimes made a special head
in the classifying of zoological facts, but it may better be
included in the subject of animal physiology.

No one elementary text-book can deal in a comprehensive
way with all of these phases of the study of animals. And yet
no one phase can be satisfactorily studied wholly by itself.
The classifying of animals into related groups depends upon a
knowledge of animal structure and development. To under-
stand animal structure one must know something of animal
physiology, and vice versa. Finally, to understand the relations
of animals to the world they live in, to the plants that serve
them as food and protection, to the other animals that they
associate with as friends or enemies, and to man, whose rela-
tions with them are much more complex and important than
we may, at first, think, it is absolutely necessary to know
something about all the other subjects of animal study.

This book, therefore, which is intended to guide students

ANIMALS, AND THE STUDY OF ANIMALS 3

who wish to learn about animals from the special point of view
of their interrelations with man, that is, their possible use and
hurtfulness and even danger to us, and our possible power to
develop this use and minimize this injury, will be found not
to neglect those other phases of animal study which are indi-
cated under the titles of classification, morphology, physiology,
and development.

But no text-book of zoology can really give the student the
knowledge he seeks. He must find out most of it for himself,
especially if he wants it to stick. A text-book based on the
experience of others is chiefly valuable for suggesting to him
how to work most effectively to get the knowledge for himself.
And the best students always find out things which are not in
books.

CHAPTER II
A STUDY OF THE FROG

Before beginning a discussion of the animal kingdom as a
whole, or of any of the important groups into which it is divided
a few animals representing different conditions of bodily
make-up may be studied. The student will then have some
definite, first-hand knowledge of the structure and organization
of animals.

FIG. i. A common western frog, Rana boyll.

A frog or a common garden toad, may be used as a type of a
vertebrate animal, that is, one with a backbone. Except
during the cold winter months frogs may usually be found
around ponds or along the banks of streams. In the spring
and early summer toads, too, are common around the water
where they are breeding. Later in the summer toads may
be found in almost any garden, where they can best be collected
at dusk.

4

A STUDY OF THE FROG 5

Whenever possible the whole class should join in collecting
the material in order that all may see the animal in its usual
haunts and study its habits there. Living specimens may be
kept in the laboratory for some weeks during which time many
interesting observations may be made. But in order to make
a closer study of the structure of the animal it must be killed.
This may be done by placing the frog in an air-tight jar or other
vessel with a piece of cotton or cloth that has been saturated
with chloroform or ether. The following description is written
for the frog, but it will serve also as a guide for the study of the
toad, as the two animals are alike in general structure.

External Structure. The body of the frog is divided into
two principal regions, the head and the trunk. In most verte-
brates there is a distinct neck between these two regions, but
in the frog they are closely united. The forelegs, or arms,
are well developed, but the hind legs are much longer and
stronger, enabling the animal to leap for considerable distances.
On the hands are four fingers or digits and a rudiment of a
thumb. The five toes on the hind legs are connected by a web.

The tough skin that covers the body is kept moist by the
secretions from many glands. The eyes are large, prominent
and protruding. When they are closed they are drawn back
into their orbits somewhat and covered mostly by the lower
eyelid, which is thin and freely movable. The upper eyelid is
thick and not capable of much movement. The tympanum,
the outer membrane of the auditory organ, is a smooth ellip-
tical membrane just back of each eye. When sound waves strike
the tympanum, causing it to vibrate, the vibrations are trans-
ferred to the inner ear by a minute rod, the columella, which
extends between the two. The nostrils are in front of the eyes
and above the mouth. The wide mouth extends from one
side of the head to the other. In the frog there are a few small
teeth on the upper jaw and in the roof of the mouth which serve
only to hold the prey. No such teeth are present in the toad.
The tongue is attached by its anterior end. The posterior
end is free and can be extended forward out of the mouth nearly
its full length for capturing insects. As the tongue is covered
with a mucous secretion the insects stick to it and are quickly

6 ECONOMIC ZOOLOGY AND ENTOMOLOGY

drawn into the mouth. In the roof of the mouth are two pairs
of openings. The anterior pair, the inner nares, are the in-
ternal openings to the nose; the posterior pair, just posterior
to the eyeballs, are the internal openings to the wide Eustachian
tubes which lead to the mouth from the chamber of the ear
behind the tympanum. At the posterior end of the mouth is
the opening of the esophagus through which the food passes
into the stomach. Just below the opening of the esophagus
is a perpendicular slit-like opening, the glottis. This opens into
the short larynx through which the air passes to the lungs.
The flaps just within this opening are the vocal cords.

Internal Structure. In making the dissection for the study
of the internal structure it is best to make the cut along the
ventral side from the anal opening, at the posterior end of the
body, to the angle of the lower jaw. The first cut should be
made only through the skin in order to expose some of the
muscles that control the movements of the body. The large
sheet of abdominal muscles covering the ventral side of the
frog consists of two sets, an outer and an inner layer. Poste-
riorly they are attached to the bony pelvic girdle which sup-
ports the hind legs. The size, position and points of attach-
ment of the heavy bundles of muscles that control the leg
movements should also be noted.

The incision may then be made through the body-wall, and
the sides fastened back to expose the internal organs. The
digestive system may be studied first. The esophagus, as
we have noted, leads from the opening at the back of the mouth
to the stomach. The stomach is somewhat crescent-shaped,
and lies mostly on the left side of the body. The anterior, or
cardiac, end is larger than the posterior, or pyloric, end where it
joins the small intestine. The small intestine is a long coiled
tube opening into the large intestine or rectum. The posterior
part of the rectum is known as the cloaca, for it also receives
the waste products from the bladder and kidneys. The ova
and spermatozoa also pass from the body through the cloaca.
The reddish-brown lobes of the liver are conspicuous. They
secrete the bile, which is an alkaline fluid that aids in digestion.
The gall-bladder, where the bile is stored, lies between the lobes

A STUDY OF THE FROG 7

of the liver and opens into the duodenum, the first part of the
small intestine, through the bile duct. The pinkish, many-
lobed pancreas lies between the duodenum and the stomach.
It also secretes a digestive fluid which is poured into the duo-
denum through the common bile duct. The food, which con-
sists chiefly of insects and worms, is first acted on by the fluid
secreted by the mucous layer of tissue lining the esophagus.
As it passes into the stomach the acid gastric juice that is
secreted by the walls of the stomach also acts upon it and
digests out some of the proteid matter. In the duodenum the
bile and the pancreatic juice act upon the fats and starches.
The food, thus digested and made available, is taken up by the
walls of the intestine and carried by the blood and lymph to
all parts of the body to build up new tissue and increase 1 he size
of the body, or to renew tissue which has been worn out by the
various activities of the animal. Some reserve food is stored
in the liver in a form that is available for use when necessary,
as during the winter while the frog is hibernating. Nutri-
ment is also stored in the large many-branched yellowish fat
bodies which are closely connected with the reproductive organs.

The lungs are thin-walled, sac-like bodies. The area of the
inner surface is increased by many folds which form minute
spaces, the alveoli, the walls of which are abundantly supplied
with blood capillaries. The waste carbon dioxide in the blood
is given off and the oxygen taken up through the thin walls of
these capillaries. The air passes through the nostrils or
external nares into a slightly enlarged chamber, the olfactory
chamber, thence through the posteror nares into the mouth.
The nostrils are then closed, the floor of the mouth is raised, and
the air is forced through the glottis into the short larynx and
into the lungs. The air is forced out from the lungs by the
contraction of the muscles of the body- wall. While respiration
is carried on chiefly by the lungs, the skin, particularly in the
frog, acts in the same capacity, the transfer of gases taking
place through the capillaries there as in the lungs.

The Circulatory System. The blood of the frog is a liquid
plasma which contains three kinds of corpuscles. The com-
paratively large, flattened, elliptical, red corpuscles are most

8 ECONOMIC ZOOLOGY AND ENTOMOLOGY

numerous and give the red color to the blood. They contain
a substance called hemoglobin, which takes up the oxygen in
the respiratory organs and carries it to the other tissues of the
body. The white corpuscles, or leucocytes, are amoeboid in
character, and are able to change their shape and move about
independently. It is their duty to take up and destroy any
small foreign objects such as bacteria, parasitic germs, bits of
broken-down tissue, or other particles that should be elimi-
nated. In this way they prevent the undue multiplication of
many disease germs that might prove most serious if they
attained to considerable numbers. The spindle-cells are cor-
puscles which may later develop into red corpuscles. Most
of the blood corpuscles are developed in the marrow of the
bones, although many of the white corpuscles are formed in
the spleen, which is a reddish, oval body lying above the ante-
rior end of the cloaca. The blood is contained in a system of
veins and arteries with a central pumping station, the heart,
which drives the blood out through the blood-vessels to all
parts of the body. With the aid of a microscope the blood may
plainly be seen circulating through the membrane between
a live frog's toes. Besides the red blood in the closed circu-
lation, there is a colorless lymph containing white corpuscles
occurring in many lymph spaces in various parts of the body.
The lymph is derived from the plasma of the blood and ulti-
mately flows back into the veins. The lymph spaces connect
with each other, and the large lymph hearts in the dorsal part
of the body cavity, by their pulsations, drive the blood into
two of the veins in the region of the heart.

The pear-shaped heart is enclosed in a delicate semi-trans-
parent sac, the pericardium. It is made up of the conical
muscular ventricle and the thinner-walled right and left auricles.
When the ventricle contracts, the blood is driven out through
the thick-walled truncus arteriosus, which soon divides. Each
of the divisions gives off three branches, the carotid arteries,
which supply the head, the systemic arteries, which pass around
the alimentary canal and unite above forming the dorsal aorta,
and the pulmonary arteries, which carry blood to the lungs and
the skin. The systemic arteries and the aorta give off branches

A STUDY OF THE FROG 9

which carry blood to the greater part of the body and to the
viscera. The pulmonary arteries, or pulmo- cutaneous arteries
as they are sometimes called, divide just before they reach
the lung, one branch passing out to the skin.

The arteries entering the lungs at once divide into smaller
and smaller vessels and finally into the small capillaries where,
as already said, the blood is purified by giving off its carbon
dioxide and taking up oxygen. The capillaries collect again
into larger and larger veins and the blood is returned from the
lung to the left auricle of the heart through the pulmonary
vein. All of the arteries that pass out to the various parts of
the body also divide into smaller and smaller vessels and into
capillaries which in turn unite to form veins. Some of the
veins carry blood through the kidneys, where urea and other
waste matter is taken out; others carry blood to the liver; but
all of the veins from the different parts of the body finally
unite into three large veins which open into the sinus venosus,
a thin-walled sac on the dorsal side of the heart. From the
sinus venosus the blood enters the right auricle. The right
auricle thus becomes filled with the impure blood, that is,
with blood that has given up its oxygen to the tissues in all
parts of the body and is carrying carbon dioxide as waste.
The left auricle, as we have seen, is filled with blood that has
just returned from the lungs and the skin, hence it is pure, that
is, it contains much oxygen and no carbon dioxide. The two
auricles contract simultaneously and send the blood into the
ventricle, that from the right auricle into the right side of the
ventricle, that from the left auricle into the left side. When
the ventricle contracts the impure blood in the right side is
forced out first and passes into the pulmonary arteries, and the
blood in the left side, which has already received its oxygen,
is sent out through the carotid and systemic arteries, carrying
its oxygen and nourishment to all parts of the body. A
longitudinal section through the heart and the beginnings of
the arteries will show the valves that keep the blood from
flowing back when the heart contracts.

The Excretory System. The reddish glandular kidneys lie
close to the dorsal body-wall. They are composed of connec-

io ECONOMIC ZOOLOGY AND ENTOMOLOGY

tive tissue in which are series of small tubules that take out
much of the waste material from the blood that flows through
the kidneys. This waste material, urea, passes from the kid-
neys through the ureters into the cloaca and collects in the
sac-like bladder, from which it is finally expelled through the
anus. The skin, liver and the walls of the intestines take some
part in excretion, but the kidneys are the principal excretory
organs. By the side of the kidneys are the yellowish adrenal
bodies.

In the region of the kidneys may be seen the reproductive
organs. In the female the ovaries, when filled with the small
black and white eggs, are very conspicuous. As these eggs
develop they break out into the body-cavity and find their way
into the open ends of the long convoluted oviducts. While
passing through the oviduct the eggs receive a coating of an
albuminous fluid which swells up when it reaches the water.
The eggs are collected in the posterior portion of the oviducts
and finally pass into the cloaca and out of the body. The
white ovoid testes of the male are attached to the ventral side
of the kidneys by folds of the peritoneum, which is a membrane
lining the abdominal wall. From each testis a number of
delicate tubes, called vasa deferentia, enter the kidney and be-
come connected with the urinary tubules. The spermatozoa
that are developed in the testes thus pass through the kidneys
and the ureters into the cloaca. The eggs are fertilized by the
spermatozoa which is poured over them while the female is
laying them.

The Skeleton. The bones making up the skeleton of the
frog may be considered in two groups: the axial skeleton made
up of the skidl and the vertebral column, and the appendicular
skeleton consisting of the bones of the fore and hind limbs and
the pectoral and pelvic girdles. The skull consists of the bones
forming the immovable upper jaw, the movable lower jaw, the
hyoid apparatus supporting the tongue, and a number of bones
joined together to form the narrow brain case. The vertebral
column is made up of nine vertebra followed by a slender bony
rod, the urostyle. Each vertebra consists of lateral transverse
processes and a firm central portion which surrounds the neural

A STUDY OF THE FROG

ii

palatine^
fronto-parietal../-?

k

pterygoid-j.A.

cervical vertebra
clavicle

, spheno-ethmoid
-maxillary

sacral

ilium -Y\,
urostyle

L-.cakaneum

tibio-fibula

astragalus
Fir,. 3. Skeleton of garden toad.

12 ECONOMIC ZOOLOGY AND ENTOMOLOGY

canal. The pectoral girdle, which supports the fore limbs
and protects the organs in the anterior part of the body, is
composed of several bony or cartilaginous pieces. The large
flat suprascapula lies above the vertebral column; the scapula,
clavicle and coracoid pass downward on either side and connect
with the sternal bones in the median line. The large humerus
of the arm is attached to the pectoral girdle between the scapula
and coracoid. The forearm consists of the fused radius and
ulna, the radio-ulna. The wrist contains six small carpal
bones. In the hand are the five basal metacarpal bones, and
beyond them the phalanges, two each in the second and third
digits and three in the fourth and fifth digits. The pelvic
girdle is shaped somewhat like the "wish-bone" in fowls, the
long bone, the ilium, on each side connecting with the trans-
verse process of the ninth vertebra. The bones of the hind
limb consist of the femur, tibia-fibula, four small tarsal bones,
the astragalus and cakaneum, the digital bones, consisting of
the metatarsals and the phalanges, and the small calcar, or
prehallux.

The Nervous System. -The nervous system can best be
dissected out in specimens that have been macerated in 20 per
cent, nitric acid for some time. The brain consists of the two
large fused olfactory lobes, the elongated cerebral hemispheres,
the rounded optic lobes, the small cerebellum and the long
medulla oblongata which gradually narrows into the spinal cord.
The optic chiasma, the infundibulum and the hypophysis are
on the ventral side. The spinal cord extends through the
neural canal in all the vertebrae and ends in the urostyle. The
brain and spinal cord give off many large nerves which branch
and subdivide and finally reach all the tissues of the body. The
s\m pathetic system consists of two principal nerve trunks, one
on each side of the vertebral column, and a series of nerves
which are distributed to the internal organs.

Life History and Habits. In the spring the frog lays her
eggs in masses in the water of ponds or ditches. The gelat-
inous substance which surrounds them soon swells so that the
egg-mass looks like a ball made up of little round bits of jelly
with black centers. The toad's eggs are similar to the frog's

A STUDY OF THE FROG 13

eggs, but are laid in strings instead of in masses. The young
tadpoles which hatch from these eggs look more like fish than
frogs. The body is long and ends in a long fin-like, flattened
tail. No legs are present, and the animal breathes by means
of two pairs of external gills. As the tadpoles grow and develop
first the hind legs and then the forelegs begin to appear, lungs
develop and the gills disappear, and the tail shortens and finally
disappears. The animal is now frog-like, though still very
small. Further growth is very slow and frogs are not really
adult, that is capable of producing young, until they are two
or three years old or older.

The tadpoles feed upon vegetable matter and minute ani-
mals that they find in the water. The adults feed principally
on insects and worms, the toads especially destroying many
insects during the warm summer nights. As most of these
insects are sure to be injurious to some of the garden crops the
toads are to be regarded as great friends of the horticulturist,
and every effort should be made to keep them in the garden.
As a result of a series of studies on the habits of the common
toad it has been estimated that a toad in a garden may be worth
nearly $20 in a single season. As they may live for ten years
or longer they are truly valuable assets of the gardener.

Toads and frogs have many enemies, among the most im-
portant of which are snakes and some of the shore birds. From
some of these enemies they have little or no protection save
their nocturnal habits and their ability to dive deep into the
water when alarmed. The milky fluid which is secreted by
ertain glands in the skin protects them from some animals which
might otherwise be important enemies. There is no founda-
tion for the belief that the toad will cause warts to appear on
the hands of a person handling it, nor for many of the other
curious superstitions concerning this perfectly harmless little
animal.

CHAPTER III
A STUDY OF THE GRASSHOPPER

As grasshoppers, or locusts, are among our most common
animals, one of these may be taken as a representative of the
great group of invertebrates, or animals without a backbone.

When collecting specimens for this study both winged and
wingless, or apparently wingless, individuals may be found.
This depends on the fact that when young grasshoppers issue
from the eggs they look much like the adults, but are without

FIG. 4. Three different stages of a locust, Mclanophis femur-minim;
a, just hatched, without wing-pads; b, a later stage showing wings begin-
ning to develop; c, adult, with fully developed wings.

wings, and the head and hind legs are often abnormally large.
As the insects pass through the successive stages of growth,
rudimentary wings appear. These increase in size from time
to time until the adult condition is reached.

Division of the Body into Regions. The body is divided
into three well-defined regions, the head with its eyes, antenna
(feelers) and mouth-parts, the thorax, which bears the two pairs
of wings and the three pairs of legs, and the abdomen, which

14

A STUDY OF THE GRASSHOPPER 15

is composed of a series of more or less similar body rings or
segments.

The Body-wall. Some parts of the skin or outer body-
wall are quite firm and horny in texture, others are more
parchment-like, and there are still other places in it, such as the
neck and between the segments of the legs, and the segments
of the abdomen, where the skin is soft and flexible. These
differences are due to the fact that a horny substance called
chitin is abundantly deposited in parts of the skin thus

antennae

compound
pronotum

femuv

tibia'''

tarsal segments

FIG. 5. The red-legged locust, Mdanoplus fcmur-rubnim, to show exter-
nal structure.

making it firm for the protection of the internal organs, and
for the attachment of muscles. Wherever motion or the bend-
ing of the body-wall is desirable, little or no chitin is deposited.
The chitinized portions of a segment are called sclerites. The
furrows or lines between the sclerites are called sutures.

The Head. Although the head is apparently a single seg-
ment, it is really composed of several body segments greatly
modified and firmly fused together, making a strong box which
contains what may, by analogy, be called the brain, and certain
other important organs. On each side of the head are the large

1 6 ECONOMIC ZOOLOGY AND ENTOMOLOGY

conspicuous compound eyes. These eyes are called compound
because they are made up of a great number of small eyes lying
very close together. Examined with a hand lens or the low
power of a microscope the compound eyes show a honeycomb-
like structure, each of the small hexagonal facets being the
external surface of a simple eye. In slight depressions just in
front of the eyes are the bases of the long, many-segmented
antenna. These antennae are sense organs and are used by
the locust for feeling and perhaps also for smelling. In many
other insects they are modified and plainly used for smelling
and also, in some, for hearing. In the middle of the front of
the head, a little lower than the bases of the antennae, is a small
transparent hemispherical simple eye or ocellus. Just above
the bases of the antennas and close to the compound eyes are
two other simple eyes. The structure and function of these
three ocelli as well as the structure of the compound eye is
discussed in Chapter XVI. On the lower side of the head are
the mouth-parts. The upper, broad, flap-like piece, the
labrum, covers a pair of black or brown, strongly chitinized,
toothed jaws, or mandibles. Back of the mandibles is a second
pair of jaw-like structures, the maxilla, each of which is
composed of several parts, and back of the maxillae is the labium
which is also composed of several pieces. Each maxilla
bears a slender feeler, or palpus, composed of five segments.
The labium bears a pair of similar palpi, which are, however,
only three-segmented. The mandibles and maxilla;, which are
the insect's jaws, move laterally, not vertically, as with most
animals. They are well adapted for tearing and crushing the
leaves or other plant tissue upon which the locust feeds. Some
other kinds of insects will be found to have these mouth-parts
curiously modified, enabling them to pierce the animal or
vegetable tissues on which they are feeding or to lap up or
suck up liquid substances.

The Thorax. The thorax is composed of three segments
which can be easily recognized by the appendages which they
bear. The first segment, the prothorax, is freely movable and
is covered by a large hood-shaped piece, the pronotum, which
also extends back over the next segment. The first pair of

A STUDY OF THE GRASSHOPPER 17

legs is attached to this segment. Between the forelegs there
is, on many species of grasshoppers, a short, blunt tubercle.
The second and third segments, the mesothorax and the
metathorax, are immovably fused, but their borders are indicated
by well-marked sutures. There is also on the side of each
segment a suture near the middle which divides the sides of the
segments into two sclerites. The mesothorax bears the second
pair of legs, which are similar to the first pair, and the first
pair of wings. The metathorax bears the large, third pair of
legs and the second pair of wings.

Each leg is composed of several successive parts or segments.
The segment nearest the body is sub-globular and is called the
coxa; the second segment is smaller than the coxa and is called
the trochanter; the third, the largest, is the femur; the fourth,
the tibia, is long and slender; the three short segments beyond
the tibia are called the tarsal segments. The terminal segment,
which is longer and more slender than the others, bears a pair
of claws, between which is a little pad, the puhillus. The
tibiae are armed with small spines, and the femora of the last
pair of legs are enormously developed, enabling the insect to
leap some distance. Just above the base of each of the middle
pair of legs is a small, slit-like opening, or spiracle, guarded by
two fleshy lips. These spiracles are the external openings of a
set of fine tubes forming the respiratory system, which as we
shall see, carries air to all parts of the body.

The front wings are long, narrow and parchment-like, with
branched and unbranched longitudinal veins and many short
cross-veins. The hind wings are triangular in outline, mem-
branous, and when at rest are folded like a fan. Some of the
veins at the base of each pair of wings are thickened and raised
or depressed in such a way that they set the wings to vibrating
rapidly when they are rubbed together. This produces the
crackling sound sometimes heard when grasshoppers are flying.
A somewhat similar sound is produced when the insect, at
rest, rubs the roughened inner surface of the hind femora
against the outer pair of wings.

Abdomen. The first segment of the abdomen has its upper,
or dorsal, and lower, or ventral, parts widely separated by the

1 8 ECONOMIC ZOOLOGY AND ENTOMOLOGY

cavities for the insertion of the hindmost legs. The ventral
part of this segment is dovetailed into the ventral part
of the metathorax and appears to be a part of it. In the
lower angle of the dorsal part there is on each side a
large opening, the external opening of the auditory
organ. The thin membranes within these openings are
the tympana. The crickets and katydids have similar
auditory organs situated in the tibiae of the front legs. Most
other insects are believed to have the sense of hearing
situated in the antennae. The second to the eighth abdominal
segments are ring-like and similar. Close to the anterior mar-
gin of each segment just above the lateral line is a small spiracle
similar to the one on the mesothorax but much smaller. The
first abdominal spiracles are on the first segment just in front
of the auditory organs. The terminal segments of the abdo-
men are different in the male and female. The female has at
the tip of its abdomen two pairs of strong, curved, pointed
pieces which compose the ovipositor, or egg-laying organ. By
alternately bringing together and separating the two pairs of
processes that form the ovipositor and at the same time push-
ing the abdomen into the ground the female is able to make a
deep hole in which she deposits her eggs. The end of the
abdomen of the male is rounded and has three short incon-
spicuous pieces on the dorsal surface.

INTERNAL ANATOMY

By carefully cutting away one side of the body-wall most of
the internal organs will be exposed. The alimentary canal
occupies the greater part of the body-cavity. Its different
divisions, such as the short esophagus leading from the mouth to
the much enlarged crop which extends through the thorax to
the stomach, may be easily distinguished. The stomach
extends to about the seventh segment of the abdomen and
ends in the large intestine. The small intestine is a short tube
running from the end of the large intestine to the anal opening
at the end of the body. The gastric c<zca are a series of pouch-
like organs which open at the union of the crop and the stom-

A STUDY OF THE GRASSHOPPER 19

ach. They secrete a fluid which aids in digestion. The
Malpighian tubules are a number of fine hair-like tubes which
arise from the alimentary canal at the point of union of the
stomach and the large intestine. They gather from the blood
and empty into the intestine certain waste products, thus
functioning something like the kidneys of higher animals.

The muscular system comprises many sets of muscles, the
largest and strongest of which are in the thorax. As there is
no internal skeleton the muscles are attached to the hardened
portions of the body-wall.

The respiratory system consists of series of small many-
branching tubes called trachea. Their walls are thin and elastic.
The external openings of these, the spiracles, have already
been noted. From the spiracles short tubes lead to two lateral
trunks which send off branches to a pair of dorsal trunks.
These lateral and dorsal trunks send branches to all the
organs and tissues of the body. The air enters the trachea
through the spiracles and is carried to all parts of the body,
where oxygen is given up to the tissues which need it, and the
waste carbon dioxide is carried away.

The reproductive system of the female is easily dis-
tinguished if the female has been collected in the fall or late
summer before she has laid her eggs. At such a time almost
the whole abdomen will be filled by the pair of thin-walled
ovaries in which may be seen the masses of oblong, brownish
or yellowish eggs. Running from the posterior end of each
ovary is a small tube, the oviduct. These unite near the pos-
terior end of the body and form a single tube which opens
between the bases of the valves of the ovipositor. The repro-
ductive organs of the male are similar to those of the. female
but much smaller. They consist of a pair of testes which lie
on the dorsal side of the posterior part of the stomach. Lead-
ing from the testes are two very small tubes, the vasa deferent ia,
which unite to form a short tube that opens on the dorsal
surface of the last segment of the abdomen. These organs
cannot be easily distinguished unless the specimen is in just
the right condition.

The nervous system is made up principally of a series of

20 ECONOMIC ZOOLOGY AND ENTOMOLOGY

ganglia, small masses of nerve cells and tissue, which are con-
nected with each other by a pair of white nerve cords. The
largest of these ganglia is situated in the head above the esoph-
agus and is called the brain. Nerve cords which unite this
ganglion with one below the esophagus pass on either side of
the esophagus. From this ganglion a pair of longitudinal cords,
very close together, pass backward along the floor of the body.
At intervals along these cords are ganglia from which fine
branching nerve fibers run to all parts of the body.

The circulatory system consists of an elongate, thin-walled
dorsal vessel called the heart situated just under the dorsal
wall of the abdomen. It is not easily distinguished except in
fresh specimens. Its structure will be described in a later
chapter where the internal anatomy of a caterpillar is discussed.
(See Chapter XVI.) There are no arteries or veins. The
colorless blood of the insect fills all the space of the body-cavity
not occupied by organs and other tissues, and is in an enclosed
vessel only while passing through the heart.

CHAPTER IV
A STUDY OF HYDRA

Frogs and grasshoppers and all the other vertebrates and
insects are very complex animals, having their bodies made up
of many highly specialized organs and tissues, each part
adapted to performing some special life process. There are
other many-celled animals much simpler in structure than
this, animals without specially developed digestive, nervous,
muscular or reproductive systems. Yet they are capable of
doing all of the essential things that the more complex animals
can do. They can take and assimilate food, respond to stimuli,
move, and reproduce their kind. Hydra is a good example
of such a simple animal, and as it is to be found in most open
fresh-water ponds, in water troughs and other places where the
water is not too stagnant, it may be taken as a type for study.

Hydrse will often be found attached to a stone, stick or leaf,
or to the green, moss-like plants that are often found in stand-
ing water. They may be green or brownish in color and as
they are only about one-eighth of an inch long or even smaller,
they will have to be looked for very carefully. Once seen,
however, they may be easily recognized by the cylindrical body
attached by the base and with its free end crowned with a
circlet of slender tentacles or arms which lash about slowly
while the animal is extended. When touched or alarmed the
whole body is quickly contracted and the tentacles drawn in,
so that the animal now looks like a simple, small, round or oval
projection on the leaf or stone. Food is caught by the ten-
tacles and conveyed to the mouth, which lies in the center at
the base of the tentacles. Through the mouth the food passes
into a space, the digestive cavity, surrounded only by the body-
wall. The food is dissolved in this cavity and the waste parts

21

22 ECONOMIC ZOOLOGY AND ENTOMOLOGY

thrown out through the mouth opening. The digestive cavity
extends out into the tentacles.

In a prepared cross-section, the body of Hydra is seen to
be a hollow cylinder with walls made up of two well-defined
layers of cells with a thin non-cellular layer between them.
Some of the cells of the outer layer, or ectoderm, have contractile
basal processes running parallel to the long axis of the body.

"W^ 33 ^

^ }

/ ./

*'
^"^v / ^"

^$&~

FIG. 6. Hydra. Note two tentacles catching an insect larva; note the
budding young Hydra. (Natural size, one-sixth inch; from life).

Like the muscle cells of higher animals these cells contract
under certain stimuli, and the whole body of the animal is
shortened, as we have seen. Among these cells, particularly
on the upper part of the body and on the tentacles, are small
stinging cells called nematocysts. The cells within which nema-
tocysts develop are called cnidoblasts, and each is provided at

A STUDY OF HYDRA 23

its outer end with a trigger-like process, the cnidodl. The
long thread-like tubes that are shot out when the nematocysts
are exploded carry a poison called hypnotoxin, which paralyzes
or kills minute animals that are stung by them.

The endoderm lines the digestive cavity. Some of the endo-
derm cells are provided with fine threads, or flagella, whose
lashings set up currents that waft the food in and out. Other
cells are furnished with blunt processes which may surround
and engulf some of the food particles, and digest them.

ovy

FIG. 7. Diagram of a longitudinal section of Hydra, bd, buds, the
upper one just beginning to develop; ect, ectoderm; end, endoderm; hyp,
hypostome; mth, mouth; net, nematocysts; ovy, ovary; spy, spermary.
(After Parker and Haswell.)

Some of the endoderm cells have contractile processes like
those of the ectoderm. The middle, non-cellular layer is a
thin homogeneous layer on each side of which lie the con-
tractile roots of the cells of the ectoderm and endoderm.

Hydra may produce new individuals either asexually or
sexually. In some individuals small swellings or buds may be
observed, usually near the base. At first these are simply
evaginations of the body-wall, but later they develop tentacles

24 ECONOMIC ZOOLOGY AND ENTOMOLOGY

and a mouth of their own. Finally the buds become constricted
at the base and separate from the parent. The young Hydrae
thus produced soon attach themselves to some object and begin
their independent existence. This budding takes place more
commonly when food is plentiful and other conditions are
favorable. At other times reproductive organs, ovaries and
spermaries, may be formed, and the animal produces special
germ cells. The ovaries appear as thickenings of the body-
wall near the lower end of the body. In each ovary a single
ovum or egg develops. The spermaries appear as smaller
thickenings of the ectoderm near the tentacles. In them the
sperm cells develop. When these reproductive elements are
ripe they are cast out into the water where the ova are ferti-
lized by the spermatozoa. Thus Hydra is hermaphroditic,
that is, both sexes are represented in a single individual.
We will find that many worms, snails and some other ani-
mals are also hermaphroditic. In such animals various
methods are adopted to prevent self-fertilization. In Hydra
this is prevented by the ova and spermatozoa in any indi-
vidual usually ripening and being cast into the water at dif-
ferent times. The fertilized ovum soon divides into a large
number of cells, forming the embryo, and after becoming
surrounded by a hard shell or cyst drops to the bottom of
the pond where it may remain for some time before it goes
on with its development.

Sometimes, through accident, a Hydra may be cut into two
or more pieces. Each part has the power of developing into
a new individual Hydra just like the original. This power of
developing anew parts of the body that may have been lost,
is possessed by many other animals, especially the lower ones,
and is known as regeneration.

CHAPTER V
A STUDY OF AMCEBA

The animals that we know best are all comparatively large
and have a body composed of many cells. Ordinarily we think
of a mouse or a humming-bird as being very small, but in the
insect world there are hosts of animals so small that they can
hardly be detected without the use of a magnifying lens. Yet
even the smallest of them are as giants when compared with
any of the one-celled animals, the Protozoa (Gr. prdtos, first;
zoon, animal), very few of which can be seen with the unaided
eye. Before the invention of the microscope the Protozoa
belonged to an unseen and unknown world. The earliest
lenses enabled the observers to see some of the largest of
them, and each improvement of the microscope has enabled
us to penetrate further and further into this fascinating field.
Now we know in detail the structure and life history of many
of these almost inconceivably minute animals.

Most of the Protozoa live in water, but a few live in damp
sand or moss, while many live in the bodies of other animals
where they may or may not cause serious injury. No moun-
tain stream is too pure, no ditch too foul to be the home of some
of these simple animals.

Amoeba. Among the most familiar of these one-celled ani-
mals are the Amoebae. They are most easily found in pools of
water, either in the slime or ooze on the bottom or in the
sediment that has settled on submerged leaves or sticks. If
some of this material is collected and poured into a dish of water
and allowed to settle for a few hours, Amoebae may usually be
found when small drops of the slime are examined on a slide
under the microscope. With the low-power lenses they
appear as small, semi-transparent, irregular-shaped objects
which, if watched carefully, will be seen to move very slowly.

25

26 ECONOMIC ZOOLOGY AND ENTOMOLOGY

Using the higher power lenses it will be seen that the outer part
of the jelly-like body, called ectosarc, is clearer than the more
granular inner part, the endosarc, and that within the endosarc
are many small granules, the food particles, and a compara-
tively large, round, clear space, the contractile vacuole, which

m&:^r

;**

' > - i' -JaHt \ V^ .

, . - f?Z;*v* :.;' ;
J v^t ' ' *-.'/ <

/-<^.\-^ . ' , '

"^ !^!*

FIG. 8. Amoeba sp. Showing the forms assumed by single individual in
four successive changes. (Greatly magnified; from life.)

appears and disappears with more or less regularity. Some-
times the darker, denser nucleus can be seen in the living
Amoebae, but it shows much more distinctly in specimens
killed by allowing a little carmine or other staining fluid to
run under the cover-glass.

Active Amoebae are constantly changing their shape, and by

A STUDY OF AMCEBA 27

these changes they effect a slow, flowing movement. Small
unequal projections, called pseudopodia, stretch out from various
parts of the body. At first these are formed only by the
ectosarc, but as they grow longer and larger the endosarc flows
out into some while others are withdrawn and new ones are
thrown out. The outline of the body thus continually changes.
As the animals move slowly about they come in contact with
other minute animals or plants around which the pseudopodia
flow and these organisms, which the Amceba uses for food,
are thus taken directly into the body. Any particles of food
or other substances which are taken into the body and not
digested pass out just as they entered, that is, the Amoeba
flows away and leaves them, much as a drop of oil that sur-
rounded a particle of sand might flow away and leave the
sand.

The oxygen that the Amoebae need is absorbed from the
surrounding water. Some of the waste excretions of the body
are absorbed directly by the water, others are forced oat by
the contractile vacuole.

Thus we see that while the Amceba has no mouth or ali-
mentary canal, no lungs or heart, muscles, glands or any of the
special organs and tissues that go to make up the higher ani-
mals, this minute speck of living substance moves, feeds,
respires, excretes and does all the essential things that the more
complex organisms do. As the Amceba feeds it grows until
it reaches a more or less definite size, then certain changes
take place in the nucleus which soon divides into two equal
portions, one portion withdrawing to one part of the body and
the other part to the opposite end. Then the substance
around the nuclei begins to divide, a portion collecting around
each of these nuclei. Finally the two halves pull entirely
away from each other and thus two new Amoebae are formed,
each like the original, but only half as large.

Amoebas continue to live and multiply as long as the condi-
tions surrounding them are favorable. But when the pond
dries up the Amoebae in it would be exterminated were it not
for a careful provision of nature. When the pond begins to
dry up each Amceba contracts its pseudopodia and secretes

28 ECONOMIC ZOOLOGY AND ENTOMOLOGY

a horny capsule about itself. It is now protected from dry
weather and can be blown by the winds from place to place.
If it again reaches water it expands, throws off the capsule
and commences active life again in the new pond.

CHAPTER VI
ONE-CELLED ANIMALS (BRANCH PROTOZOA)

The Amoeba which has just been studied is one of the sim-
plest of the one-celled animals. Others while still retaining
the one-celled condition, become more highly specialized along
certain lines and show a wonderful power to adapt themselves
both in form and habits to the various conditions under which
they live. A brief study of a few of these will be worth while.

Paramcecium. Paramcecia are usually found in considerable
numbers in any pond of stagnant water. A good supply can
often be obtained by placing sticks or leaves from a pond,
together with some dry hay or clover, in a dish, which is then
filled with water and allowed to stand for several days. When
very abundant the Paramcecia may even be seen with the
unaided eye as minute white specks near the edge of the dish.
Examined with the low power of the microscope they will be
seen as very active, slipper-shaped animals much larger than
the Amoebae. As they move about so rapidly it is desirable
to put them into some thicker medium, such as a thin mixture
of cherry gum; or a few shreds of cotton may be put under
the cover-glass and some of the Paramcecia will become en-
tangled in this in such a way that they may be studied.

It will at once be seen that Paramcecium differs from Amoeba
in many respects. It has a definite and persistent elongate-
oval shape, roughly like that of a slipper, hence it is often
called the slipper animalcule. There are definite anterior
and posterior ends and dorsal and ventral sides, and the body is
covered with minute cilia-, fine hair-like projections, which
vibrate very rapidly and propel the animal through the water.
On one side, beginning at the anterior end and extending more
than half the length of the animal, is a buccal groove, which is
provided with many small cilia which drive water currents and

29

30 ECONOMIC ZOOLOGY AND ENTOMOLOGY

all kinds of particles into the gullet which opens into the inte-
rior. Food particles surrounded by a film of water are taken
into the body through this opening and are digested just as
they are in the body of the Amoebae. The water drops are
ejected at a spot in the cell membrane just below the gullet.
If a little finely powdered carmine is added to the water

in which the Paramcecia are swim-
ming some of the grains will be taken
into the body where they will be seen
to follow a rather definite course from
one end of it to the other. Instead of
one contractile vacuole as in the
Amoebae there are two, and there are
also two nuclei, which can be seen in
specimens stained with carmine. The
large one, ovoid in shape, is called the
macronucleus, and the smaller oval
one close beside it is the micronucleus.
Between the bases of the cilia there
may be seen many minute oval sacs
lying side by side. These are called
the trichocysts, and from each a fine
stinging thread can be thrust out
which, it is believed, help to protect
the Paramcecium from other minute
animals.

The Paramcecia reproduce by sim-
ple division as do the Amoebae. The
macro- and micro-nuclei divide and
the body becomes constricted in the
middle and the organism is finally
divided into two smaller animals which
soon grow to be like the original.

FIG. 9. Paramceciitm
sp. Buccal groove at
right. (Greatly magni-
fied; from life.)

But after multiplication has gone on in this way for many
generations, often from one to two hundred or more, the Para-
mcecia seem to be unable to divide further until a new pro-
cess takes place. Two Paramcecia approach each other and
unite, usually with their buccal grooves together; then there

ONE-CELLED ANIMALS

3 1

is a breaking up of the nuclei and a part of the micronucleus
of each individual passes over to the other. Then the Para-
mcecia separate and each divides into two. This is, in very
simple condition, the process of ferti-
lization, which occurs in more elaborate
condition in all the higher animals.

Vorticella. Many other minute or-
ganisms will be found in the drops of
water that have been examined while
looking for the Amoebae and Paramce-
cia, but of these we wish to call parti-
cular attention to but one. On the
leaves or sticks that have been collected
from ponds and placed in vessels of
water, tiny whitish mould-like tufts
may sometimes be seen. Touch such
a spot with a needle and it may con-
tract instantly. If so, it is probably
a colony of Vorticella, or bell animal-
cules. Such a mass, examined under
the lens, will be seen to be made up of
a number of attached slender stalks
each having a bell-shaped free end,
hence the common name, bell animal-
cule. When the stalk is extended it is
straight or somewhat curved but when
the animal is disturbed the stalk con-
tracts into a close spiral. The thick-
ened upper outer margin of the bell,

the penstome, and the central disk, the s t a lk coiled, and one
epistome, are fringed with rather long with
cilia. Between the peristome and the
epistome is a groove, the mouth or vesti-
bule, which leads into the body. The substance comprising
the body is differentiated into an outer uniformly granular
ectosarc and a more transparent, colorless endosarc, in which
are numerous large food vacuoles, a large clear contracting
vesicle, a large curved macro-nucleus, and near it a micro-

stalk extended.
(From life; greatly mag-
nified.)

32 ECONOMIC ZOOLOGY AND ENTOMOLOGY

nucleus, the latter often being difficult to see unless the
specimens are stained. The slender stalk is made up of a
clear outer portion and a denser contractile inner rod.

The Vorticellae multiply by longitudinal division, or fission.
In this process a cleft first appears at the distal end of the bell-
shaped body and gradually deepens until the original body is
divided quite in two. The stalk also divides for a very short
distance. One of the new bell-shaped bodies develops a
circlet of cilia near the stalked end. After a while it breaks
away and swims about by means of this basal circlet of cilia.
Later it settles down, becomes attached by its basal end, loses
its basal cilia and develops a stalk. Conjugation sometimes
occurs between two individuals. Under certain conditions
there is produced, by repeated divisions, small free-swimming
forms, one of which may meet one of the large stalked forms
and be completely absorbed by it. This differs from the proc-
ess of fertilization in the Paramcecia in which the union was
only temporary, and presents an even more striking analogy
with the process of sexual reproduction occurring in the higher
animals.

Marine Protozoa. The Protozoa are more abundant in
the ocean than they are in fresh water. Although the ocean
water may appear to the unaided eyes as clear and free from
living things, yet a microscopical examination will show it to
be swarming with minute animals and plants. These are
found at all depths, from the surface to the deepest parts of
the ocean, and are interesting not only because they repre-
sent the lowest, simplest and doubtless earliest kinds of ani-
mals that appeared on the earth, but because they furnish,
together with the Protophyta, or one-celled plants, directly or
indirectly, food for all of the other animals of the sea. As we
study some of the representatives of the higher groups of ocean
animals we shall see that many of them are particularly adapted
by structure and habit for feeding on these minute organisms,
and that they in turn serve as food for other animals, so
that finally all of the animal life in the ocean becomes de-
pendent on the one-celled organisms for their food. This is
one of the reasons for believing that the Protozoa were the first

ONE-CELLED ANIMALS

33

animals to appear on the earth, and as ocean life is older
than terrestrial life it is probable that certain marine Protozoa
are the most ancient of all animals.

Some of these marine Protozoa, as the Foraminifera and the
Radiolaria, secrete a tiny shell of lime or silica which encloses
most of the body. When these animals die their shells sink
to the bottom where, as they slowly accumulate, they form a
thick layer over the floor of large areas of the ocean. The

FIG. ii. A marine Protozoan, Rosalina variant (Foraminifera), with
calcareous shell. (Greatly magnified; after Schultze.)

ooze thus formed is called Foraminifera ooze or Radiolaria ooze,
according to which order of Protozoa chiefly formed it. All
over the world are found great strata of rocks that are formed
almost exclusively of the fossil shells of these Protozoa. The
extensive chalk beds and cliffs of England, France, Greece,
Spain and America were made by Foraminifera, whose shells
were deposited there when these places were parts of the ocean
beds. The siliceous rock called Tripoli, found in Sicily, and the
Barbadoes earth from the island of Barbadoes are composed of
the shells of ancient Radiolaria.

3

34 ECONOMIC ZOOLOGY AND ENTOMOLOGY

Parasitic Protozoa. Because of their simple structure and
physiology the Protozoa easily adapt themselves to new modes
of life, when conditions are favorable. It was an easy step
from an existence in the water to life in the blood tissues of
some of the aquatic animals or in some of the higher animals,
and the Protozoa that have made this step have come to be
among the greatest scourges that affect mankind. These
parasitic Protozoa are so important that a later separate
chapter will be devoted to an account of them. (See Chapter
XXVIII.)

Classification of the Protozoa. The branch Protozoa is
divided into five groups or classes, the divisions being based
principally on the manner in which the members of the different
groups move about. The Amceba, the Foraminifera and the
Radiolaria belong to the class Rhizopoda (Gr. rhiza, root;
pous, foot). Rhizopoda means "root-footed" and the name
is applied to those Protozoa which move about by means of
the extending or flowing out of the root-like processes called
pseudopodia, or false feet.

Paramcecium and Vorticella belong to the class Infusoria
(L. infusus, infused), a name that was early used because
these organisms are so frequently found in infusions. Because
their body is furnished with minute hair-like organs called
cilia they are often called Ciliata.

From an economic point of view the class Sporozoa (Gr.
spora, seed; zoon, animal) is the most important. The mem-
bers of this class are parasitic and cause some of the most
serious diseases of man and other animals, such as the various
malarial fevers, the spotted fever of man, and the Texas fever
of cattle.

The whip-bearers (class Mastigophora, Gr. mastix, whip;
phero, bear) also include a number of important parasites, as
the trypanosomes that are the cause of the dreadful disease
which ends in sleeping sickness, and the Spirochatce, which are
the cause of certain relapsing fevers. The little green Euglena,
whose presence in standing pools often imparts a greenish
color to the water, and the wonderfully phosphorescent
Noctiluca of ocean waters, also belong to this class. The

ONE-CELLED ANIMALS 35

Noctiluca live near the surface, and when disturbed at night
their little bodies glow like coals of fire. This class also in-
cludes a number of so-called colonial Protozoa such as Volwx,
Proterospongia and others. These are more or less closely
associated groups of similar individuals or colonies in which the
individual members show some differences and have more or
less special functions to perform.

The members of the class Mycetozoa (Gr. mykes, fingers;
zoon, animal) resemble fungi in many respects and are often
included with them under the name "slime moulds." They
are of no economic importance.

Protoplasm and the Cell. All the Protozoa have the body
composed, for its whole life, of but a single cell. By cell is
meant not necessarily a little enclosed or box-like bit of animal
substance, but simply a small (usually microscopic) mass of
protoplasm which is composed of an inner, denser part called
nucleus and a surrounding less dense part called cytoplasm.
Protoplasm itself, " the physical basis of life," is a substance or
group of substances, usually viscous or jelly-like, which always
contains certain very complex albuminous chemical compounds
called proteins. These proteins are never found in inorganic
matter and are always fround in living tissues. Proteins
contain carbon, oxygen, hydrogen and nitrogen, and are
almost the only group of substances found in living matter of
which chemists have not yet been able to make representatives
in the laboratory. Besides the all-important proteins proto-
plasm usually includes certain other characteristic compounds
known as carbohydrates and fats (which contain no nitrogen),
and various salts and gases, and always water. The gases are
oxygen and carbon dioxide, and the salts are compounds of
chlorine as well as the carbonates, sulphates and phosphates of
the alkalies and alkali earths. Common salt (sodium chloride)
is almost always present.

What a Single Cell Can Do. All the larger animals are com-
posed of many cells which are grouped together to form organs
or tissues each with its special function to perform, but the
minute one-celled mass or protoplasm forming the whole
body of each Protozoan is able to carry on all the necessary

36 ECONOMIC ZOOLOGY AND ENTOMOLOGY

processes of life, digestion, assimilation, respiration, excretion,
secretion, and to reproduce others of its kind. It is this
wonderful capacity for living that separates the one-celled
organisms, simple as they may seem to be in comparison with
higher plants and animals, by a wide gulf from the most com-
plex of inorganic bodies. Some scientists have been able to
produce in their laboratories particles of matter that closely
resemble, in many respects, these simple organisms, but none
has yet been able to endow these creations with the subtle
power which we call life.

We have found, moreover, in our study of the Protozoa that
while they are each composed of but a single cell, or, rarely, of
a group of cells temporarily united to form a colony, the cell
itself may be very complex in its structure, some parts of it
adapted for protection, other parts for locomotion or food
getting. There may be a definite upper and lower side and
anterior and posterior end, and there may be many other
specializations of parts that especially fits each of these one-
celled animals to live in its particular place.

Spontaneous Generation. People used to believe that many
animals were spontaneously generated. When myriads of fly
larvae mysteriously appeared in a mass of decaying matter it
was supposed that they had been generated there spontane-
ously. When great numbers of frogs or insects or any other
animals appeared from some unknown source the phenomenon
was explained by spontaneous generation. Long after it had
definitely been shown that none of the larger animals could
arise in this way, many still held to the belief that at least the
simplest animals and plants arose in this way. If a vessel of
ordinary water in which there are apparently no living organ-
isms be allowed to stand for a few days it will usually be found
to be swarming with minute animals and plants. The source
of this life was a mystery to the older observers, but we know
now that some of these organisms come from others that were
already in the water and some come from spores that are
constantly in the air. If a bottle of water is boiled thoroughly
enough to kill all the organisms in it, and then closed so tightly
that no germs or spores can reach it from the outside, it will

ONE-CELLED ANIMALS

37

remain perfectly sterile that is, no living animal nor plant
will ever appear in it.

Reproduction in Protozoa. All life comes from life. Every
living creature is the offspring of some other living creature.
This is just as true for the Protozoa as for the higher animals,
but their method of reproduction is usually much more simple.
In many cases the Protozoan animal simply divides into two
more or less similar smaller animals which grow until they
attain a certain size and then divide again, and the process is
continued for generation after
generation. This is called repro-
duction by simple division or fis-
sion.

Protozoa that thus live and re-
produce by simple division have
been called immortal, and it would
seem that under natural condi-
tions such animals never die, for
as soon as they reach a certain
size they divide and form two new
individuals and as this process is
continued for generation after gen-
eration there would seem to be no
death of the individual. Careful
studies have shown, however, that this process of simple divi-
sion cannot continue indefinitely unless there is introduced
into the cycle from time to time the extraordinary process
known as fertilization by which the mature or old individuals
are rejuvenated. In many of the Protozoa this process of
fertilization is accomplished by the conjugation of two similar
individuals in which two animals come together and undergo
complete or temporary fusion. Such a conjugation is followed
by renewed activity, the process of division going on more
rapidly than before.

Many Protozoa instead of dividing directly into two parts
go through a process called spore formation. The animal
becomes encysted in a firm little sac or cyst in which it remains
for some time. Then it divides into many small bodies, called

FIG. 12. Division of
Amoeba. (Greatly magnified;
after Schultze.)

38 ECONOMIC ZOOLOGY AND ENTOMOLOGY

spores, which finally burst out into the water or other medium
in which the animal lives, where each spore develops into an
organism like the parent. This process makes it possible for
the animals to multiply very rapidly, and we shall see something
of its importance when we come to study the Sporozoa, a group
of parasitic Protozoa which all reproduce in this way and some
of which are the causes of certain common diseases of man and
other animals.

CHAPTER VII
ONE-CELLED AND MANY-CELLED ANIMALS

Of the animals so far studied, Amoeba, Paramoecium,
Vorticella and their allies have the minute body composed of
but a single cell. The others, the frog, grasshopper and hydra,
have the body composed of many cells. This distinction of
one-celled and many-celled body has led to the classification
of all animals into two primary groups, the Protozoa, including
all those with one-celled body, and the Metazoa, all those
with a many-celled body. They are groups of very unequal
size, as of the 500,000 (approximated) known kinds of living
animals all but about 10,000 are Metazoa. But the distinction
between Protozoa and Metazoa is very important; it is indeed
one of the most fundamental in animal structure and classifica-
tion. For although many-celled animals are undoubtedly
derived by descent from one-celled ones, yet the group of single-
celled animals, the Protozoa, is much larger than we should
expect it to be if it were simply the beginning of the animal
scale. It is not only a beginning stage in animal evolution,
but it is an evolutionary line of its own. There is a great deal
of variety and complexity in the structure, physiology and
mode of development within the protozoan branch. All this
diversity has, however, to be limited to the differences possible
to a single cell. The moment animal evolution made the step
from independent single cell to mutually dependent many cells,
united for life, infinitely greater possibilities of diversity in
structure and function and life history were open. And the
extraordinary variety of animal life as it appears to us now in
the various groups of Metazoa, is the result of Nature's taking
advantage of these possibilities.

But the step was not a sharp one, nor was the attainment of
present-day animal complexity and diversity brought about

39

40 ECONOMIC ZOOLOGY AND ENTOMOLOGY

at all speedily. It was millions of years after the first
many-celled animals appeared on the earth before the first
insect appeared. And still millions of years later before the
first backboned animal was evolved.

As to the step from isolated single cell to united many cells,
it was undoubtedly made in the simple way still represented
by a few living organisms known as Volvocinae, sometimes
called plants, and sometimes animals. These are one-celled
organisms that live as small colonies or groups of cells. These
few cells, only sixteen in the case of several of these organisms,
are all derived from a single cell by its division into two and the
succeeding divisions of these two into four, the four into eight
and the eight into sixteen. And they are all alike. They
remain together in the form of a tiny ball, the cells all imbedded
in a soft gelatinous substance secreted by them. Each cell has
a pair of flagella, and the waving of all the flagella moves the
little ball through the water. Each cell can take up food,
respond to stimuli, and in fact do all the things that we have
found are essential to living and which are done in the simplest
manner by the one-celled animals. Indeed it is probable that
each cell could live independently; and as a matter of fact each
one does for a short time when the colony breaks up after reach-
ing maturity.

For when this little colony is mature and ready to repro-
duce itself, the gelatinous stuff dissolves, the sixteen cells
are set free in the water, and each, by repeated division may
produce a new colony. Or a process of conjugation between
pairs of the freed cells can take place, and from each paired
cell formed by the conjugation of the two, a new colony may
be formed by simple division.

Differentiation and Specialization of Cells. If this first step
toward making a many-celled animal out of a single-celled one
seems simple, the next step does not. In the simplest kinds of
true many-celled animals an important new condition appears.
It is a condition of differentiation or specialization of the cells
united to form the body. The cells are no longer all alike in
appearance, and no longer have identical capacities. Only a
few of them remain in simple generalized condition. These

ONE-CELLED AND MANY-CELLED ANIMALS 41

are the so-called white blood corpuscles which have an appear-
ance much like that of the Amoebae and have a great deal of
freedom or independence in their life.

The rest of the hundreds or thousands or millions of cells that
go to make up a many-celled animal's body differ greatly
in appearance and behavior from Amoebae, and differ also
greatly among themselves. Besides the amreboid white cells
in the blood there are, in red-blooded animals, many elliptical,
disk-like reddish cells and they have an entirely different func-
tion from that of the white cells. The cells composing the
muscles are, moreover, not like either of the kinds of blood
cells; the cells of which the liver is composed are not like the
cells of the muscles; and the cells which compose the organs of
the nervous system, brain, ganglia and nerves, differ markedly
from those of the blood, muscles and liver, and differ also very
much among themselves.

Each of these kinds of cells, and each of the many other kinds
that exist in the body of one of the higher animals, has become
specialized in order to devote itself to a certain particular func-
tion or special work. For example, the cells of the nervous
system devote themselves to the function of receiving and
transmitting sensation. The muscle cells have developed to
a high degree the power of contractility, and they have for their
special function this one of contraction. Massed together in
great numbers, they form the strongly contractile muscles of
the body on which the animal's power of motion depends.
The cells which line certain parts of the alimentary canal are
the ones on which the function of digestion largely rests. And
so we might continue our survey of the whole complex animal
body. The point of it all is, however, that the thousands of
cells which compose many-celled animal bodies are differenti-
ated and specialized. That is, have become changed or modi-
fied from the generalized primitive amceboid cell condition so
that each kind of cell is devoted to some special work or func-
tion, and has a special structural character fitting it for its
special function.

Organs and Functions. The specialized cells are grouped
into tissues and organs. These organs are known to us

42 ECONOMIC ZOOLOGY AND ENTOMOLOGY

familiarly as various parts of the body, such as lungs, heart,
muscles, eyes, stomach, etc. The life of an animal consists of
the performance by it of various processes, such as breathing,
getting and digesting food, circulating blood, moving, seeing,
etc. These various processes or functions are performed by
the various parts or organs of the body.

The whole body of a many-celled animal is thus really a
machine composed of various parts, each part with its special
work to do but all depending upon one another and operating
to accomplish the work of living. The locomotive engine is a
machine similarly composed of various parts, each part with
its special work or function, and all the parts depending on one
another and so working together as to perform satisfactorily
the work for which the locomotive engine is intended. An
important difference between the locomotive engine and the
animal body is that one is a lifeless machine and the other a
living machine. But there is a real similarity between the
two in that both are composed of special parts, each part
performing a special kind of work or function, and all the parts
and functions so fitted together as to form a complex machine
which successfully accomplishes the work for which it is
intended. And this similarity is one which should help make
plain the fundamental fact of animal structure and physiol-
ogy, namely, the division of the body into numerous parts or
organs, and the division of the total work of living into various
processes which are the special work or functions of the various
organs.

Essential and Accessory Life Processes. A very complex
animal, such as a dog, performs a great many different func-
tions, that is, does a great many different things in its living.
But there are many animals in which the body is composed of
but a few parts and whose life includes the performance of
fewer functions or processes than in the case of a dog. There
are many animals that have no eyes, nor ears, nor organs of
special sense. There are animals without legs or other special
organs of locomotion; some animals have no blood and hence
no heart nor arteries and veins. But in the life of every animal
there are certain processes which must be performed, and the

ONE-CELLED AND MANY-CELLED ANIMALS 43

body must be so arranged or composed as to be capable of
performing these necessary life processes. All animals take
food, digest it and assimilate it, that is, convert it into new body
substance; all animals take in oxygen and give off carbon
dioxide; all animals have the power of movement or motion
(not necessarily locomotion); all animals have the power of
sensation, that is, can feel; all animals can reproduce them-
selves, that is, produce young. These are the necessary life
processes. It is evident that the dog could still live if it had
no eyes. Seeing is not one of the necessary functions or proc-
esses of life. Nor is hearing, nor is leaping, nor are many of
the other things which the dog can do; and animals can exist,
and do exist, without any organs to enable them to see and hear
and leap. But the body of an animal must be capable of
performing the few essential processes which are necessary to
animal life. How surprisingly simple such a body can be our
study of the Protozoa has already shown. But in most animals
the body is a complicated object, and is able to do many things
which are accessory to the really essential life processes, and
which make its life complex and elaborate.

The Principal Systems of Organs and Functions. These
complex life processes are usually carried on by systems of
organs which are known as the skeletal, muscular, digestive,
respiratory, circulatory, excretory, nervous and reproductive
systems. And the particular set of special functions or life
processes connected with each is sufficiently indicated by its
name. Of them all, the reproductive system and its function,
which is that of the multiplication of the species, calls for a few
special words of introduction before we pass to the considera-
tion of the successive animal groups. For it is in connection
with this function that some of the most important special
conditions in animal life exist. The important fact of sex, for
example, is correlated with this function, while the whole
subject of animal development may be looked on as part of
the study of animal multiplication.

Reproduction and Development in the Metazoa. We have
learned that the process of multiplication among the Protozoa
is, in most cases, very simple, consisting of the simple splitting

44 ECONOMIC ZOOLOGY AND ENTOMOLOGY

of the parent's body in two. Previous to this splitting in two
there may be a temporary fusion for the purpose of a mutual
exchange of part of the body substance, or a permanent con-
jugation of two individuals. The process of reproduction
among the many-celled animals is far more complex, and certain
particular organs of the body of complex structure are specially
devoted to this function. The results of the process, however,
are the same as among the lower animals, namely, the produc-
tion of new individuals. The manner in which the reproduc-
tive process is carried on, and the number of new individuals
produced by a single parent individual, may and do vary much
among different animals.

Among some of the -simpler many-celled animals the new
individual is sometimes produced by the growth of an external
bud, or by the splitting off of a small part of the parent's body,
a process much like the fission, or splitting in two, of the one-
celled animals. But this is an unusual method, and possible
to comparatively few animals. In almost all cases the young
come from eggs, or ova, which are produced inside the body of
the mother. These eggs usually issue from the body before
hatching, but in some animals, as all the Mammalia, the young
develop from the ova inside the body and are born as active
free animals, resembling the parent more or less in appearance
and structural character, although of course much smaller.

In all cases the young animal has to undergo a certain amount
of development and growth, which extends over a longer or
shorter period of time, before it is really like its parent, that is,
before it is a fully developed, full-grown individual. No
animal is born fully developed; it is born from the body of its
mother or hatched from its egg in an immature condition, and
growth and change are necessary before we have a fully devel-
oped rabbit or robin, or any other kind of animal.

But when we begin the study of the life history of the new
animal with the time of its emergence from the body of the
mother or from the egg, we are not beginning at the beginning.
When we first see the new animal it is already of appreciable
size and complex structure. But at its very beginning inside
the body of the mother it is, in every case, simply a single cell.

ONE-CELLED AND MANY-CELLED ANIMALS 45

Every individual begins as a single cell, and develops and grows
from this single cell to its final complex adult condition. The
first single cell is called the fertilized egg cell or ovum, and an
egg is simply this primary germ cell, or the embryo which
develops from it, together with a greater or less amount of
yolk (which is food for the germ), enclosed in a membrane or
shell. In the case of those animals which do not lay eggs, but
give birth to their young in a free condition, the egg, which is
kept inside the body of the mother, is usually composed of the
germ alone, food being provided the embryo directly from the
body of the mother. After the young has reached a certain
stage in its development, it leaves the body of the mother and
food is provided it by suckling or in some other way. The
development of an animal from first germ cell to the time it
leaves the body of the mother, if born free, or until it is hatched
from an egg, is called its embryonic development; and the
development from then on is called the post-embryonic develop-
ment. Beginning students of zoology cannot study the em-
bryonic development (embryology') of animals readily, but they
can in many cases follow the course of the post-embryonic
development, and this study will always be interesting and
valuable

It is a kind of study of particular importance to the economic
zoologist, because in all attempts to make better uses of animals,
or to restrain their injuries, a knowledge of their life history is
essential. This life history includes the facts of their develop-
ment and the facts of their habits and general behavior both
in immature and mature condition. In the case of an injurious
insect, for example, the times and place of egg-laying, the
character and duration of the immature stages, the time and
place of pupation, etc., are all important conditions. A
knowledge of these may enable the economic zoologist to hit
upon exactly the best means for combating the pest.

The radical changes or metamorphoses undergone during
development by many insects must be taken into account in
any consideration of them as possible enemies of man. Young
grasshoppers, for example, are wingless and can be captured
and killed by simple methods which would be of no use in the

46 ECONOMIC ZOOLOGY AND ENTOMOLOGY

case of the mature flying individuals. Indeed even simpler
and more effective means can be brought to bear against the
eggs of the grasshoppers. But a knowledge of the times,
places and peculiar manner of the egg-laying of grasshoppers
was necessary as a basis for devising these remedies. Butter-
flies and moths take only plant nectar and water for food, and
are harmless in the adult stage. But in their immature
stage, as strong-jawed biting larvae (caterpillars) many kinds
are extremely injurious. The mosquito is annoying as a
blood-sucking pest and dangerous as a breeder and disseminator
of yellow and malarial fevers only as a full-developed flying
adult, but it is only in its immature or larval and pupal stages
passed in quiet water that it can be successfully fought. The
student of economic zoology then should give a special atten-
tion to the study of animal multiplication and development.

Sex and the Fertilization of the Egg. Among the one-celled
animals we found that before an individual divided into two,
that is, multiplied, it sometimes met another individual with
which it exchanged body substance. Among most of the many-
celled animals the germ cell or fertilized egg cell which develops
into a new individual is produced by the fusion of two so-called
reproductive cells from two distinct individuals of the same
species or kind of animal.

The reproductive cells produced by the females are known
as eggs or ova, and are usually produced in the ovaries; those
produced by the male are called spermatozoa and are produced
in the spermaries, or testes. Before the ova can begin their
development they must be fertilized by the spermatozoa.
There are a few exceptions to this general rule, young being
produced by some kinds of animals from unfertilized eggs.
But these cases are comparatively rare and in most of them
fertilization of some of the eggs, at least, takes place also.

We shall find among the Metazoa various devices to aid in
bringing the ova and spermatozoa of two individuals of a kind
together. Many of the aquatic animals simply cast their
reproductive cells into the water where they meet by chance.
Of course many of the ova thus thrown out are never reached
by the spermatozoa and so no development takes place, but

ONE-CELLED AND MANY-CELLED ANIMALS 47

when the eggs are laid in this way they are always produced
in great numbers. An average sized oyster will produce
during the season about 16,000,000 eggs and a large old female
may produce more than three times that many during the few
summer months that she is breeding. The number of sper-
matozoa that are produced by a male oyster is simply incon-
ceivable, and the water in the vicinity of the oyster beds is
literally swarming with these minute cells during the breeding
season. These enormous numbers are made necessary by
the fortuitous mode of fertilization. It is a condition compar-
able with that of the great production of pollen and chance
method of pollination in the case of the pines and other wind-
pollinated flowers.

Other aquatic animals, as certain fishes, lay their eggs in a
more or less carefully prepared nest, and the male soon passes
by and deposits the milt, which contains the spermatozoa,
over them. With most of the higher animals, however, the
ova are fertilized while still inside the body of the mother, and
various provisions are made for transferring the spermatozoa
from the male to the female.

CHAPTER VIII
THE CLASSIFICATION OF ANIMALS

The first thing one asks about an animal new to one's ex-
perience is, what is its name? It is really less the name itself
that we wish to know, than the information that this name
gives regarding the placing of the animal in some classificatory
relation with other animals. It is the classifying interest
that impels our question; and with most of us it is this interest
which in turn usually develops from a collecting interest
that first attracts us to the study of zoology.

Meaning and Basis of Classification. However, if classify-
ing animals meant only arranging them in simple groups of
similar or dissimilar forms, and naming them, the classificatory
interest would deserve the reproaches so often heaped on it
by naturalists more interested in anatomy or physiology or
development. But classifying animals means much more
than that. Since the days of Darwin's "Origin of Species,"
when the theory of the evolution of animals and plants was so
clearly explained and proved that the world could not help
but accept it as true, the classification of living things has had
a new and great importance. It has the importance of repre-
senting our knowledge of organic evolution, for the classifying
of animals and plants now means arranging them in groups
according to their descent.

In the early days of the study of animals and plants their
classification or division into groups was based on the external
resemblances and differences which the early naturalists found
among the organisms they knew. But later when naturalists
began to dissect animals and get acquainted with the whole
body, the differences and likenesses of the inner parts, such
as the skeleton and organs of circulation and respiration, were
taken into account. For we know that animals which are

48

THE CLASSIFICATION OF ANIMALS 49

really closely related may not, on the surface, closely resemble
each other. The outside of their bodies may become much
modified to adapt them to different environments. But their
internal structure and their development will usually reveal
their nearness or relation. On the other hand, animals not
closely related by descent may become and look superficially
like each other by becoming adapted to living in the same
environment, taking the same kind of food, etc. But again a
study of the development and internal anatomy will usually
establish marked differences, indicating their lack of real gen-
ealogic nearness.

Modern zoological classification, is, therefore, based on a
great deal of serious study of animal structure and development
and represents, as we have already said, our present knowledge
of the actual blood relationships of animals. It means more
than that animals of the same group resemble each other in
certain structural characters. It means that the members
of a group are related to each other by descent, that is genealog-
ically. They are all the descendants of a common ancestor;
they are all sprung from a common stock. And this added
meaning of classification explains the older meaning; it ex-
plains why the animals are alike. The members of a group
resemble each other in structure because they are actually
blood relations.

The history of animal classification with all the changes in
it, and the succeeding points of view and new significance
represented by these changes, is an interesting chapter in the
history of science. It began, in any real way, with Linnseus,
the great Swedish naturalist who worked in the middle of the
eighteenth century. In the years just before and after 1750
he published successive editions of his "Systema Naturae,"
which was the first attempt to describe and name and classify
all the known kinds of animals and plants. In the loth edition
(1758) of this "Systema" he catalogued about 4000 kinds of
animals. (Now we know 500,000 kinds!)

In this great catalogue he adopted a system of short scien-
tific names, one for each kind of organism. And he classified
all these named animals into groups of successive degrees of

4

So ECONOMIC ZOOLOGY AND ENTOMOLOGY

inclusiveness, which he called, species, genus, or do and classis.
We still use Linnaeus's general system of classification and most
of his short two- word scientific names for the different animals
and plants that he knew, but we base the classification on other
grounds than the superficial resemblances that he used, and we
see in our classification a more far-reaching significance and a
much greater importance than he saw. But Linnaeus was the
first great animal classifier, or systematic zoologist, and de-
serves all honor for his important w r ork.

Animal Names. Well-known animals have common, or
vernacular names, but less familiar ones do not. Also these
common names differ in different countries; that is, are differ-
ent in different languages. The animal we call dog, the Ger-
mans call Hund, the French, chien, and the Italians, cane.
And even in the same country one common name may be
applied in different parts of it; as "quail" which means one
kind of bird in the East, another kind in the Mississippi Valley,
and still another on the Pacific Coast. "Partridge" has still
a wider divergence of application, and "minnow" refers to
nearly as many different fishes as the localities in which the
word is used.

Thus if there is to be accurate speaking and writing about
animals, and if the naturalists of different countries are to be
able to use names that are understandable to all, there is
necessary some system of naming animals other than the popu-
lar one of vernacular names. This system is that of the so-
called "scientific names," or two-word names in Latin or
Greek, devised and successfully established by Linnaeus. It
is a system which has given rise to much popular fun-making
and no little scientific discussion and dispute, but whose use-
fulness is so real and whose principles are so sound that it will
likely never be given up.

The names used in it are all Latin or Greek simply because
these classic languages are taught in the schools and colleges
of almost all the countries of the world, and are thus intelligible
and familiar to naturalists of all nationalities. In the older
days, indeed, all the scientific books, the descriptions and
accounts of animals and plants, were written in Latin, and now

THE CLASSIFICATION OF ANIMALS 51

most of the technical words used in naming the parts of animals
and plants are Latin. So that Latin may be called the language
of science. For most of the groups of animals we have English
names as well as Greek or Latin ones and when talking with an
English-speaking person we can use these names. But when
scientific men write of animals they use the names which have
been agreed on by naturalists of all nationalities and which
are understood by all of these naturalists. These Latin and
Greek names of animals, laughed at by non-scientific persons
as "jaw-breakers," are really a great convenience, and save
much circumlocution and misunderstanding.

Zoological Classification and Nomenclature. In any dis-
cussion of the nomenclature of zoological classification it is
first of all necessary to distinguish between the few names
used as common nouns, such as species, genus, family, order,
etc., which denote the different kinds of groups into which
animals are divided, and the host of proper noun names which
are applied to the many groups of each kind which have been
established by students of systematic zoology.

A single kind of animal, as a house-fly, a robin or a coyote,
is called a species of animal. Coyotes, dogs and gray wolves
are different species much alike. They are grouped together
with some other kinds of wolves and dog-like animals to form
a group called a genus. The robin belongs to a genus which
includes one or two other robin-like species of birds and the
house-fly to a genus which includes several other house-fly
species of insects. Each of these genera has a proper name,
which distinguishes it from all other genera, and for that matter
from all other groups of animals, because a genus name is
never used for more than one group of animals. The dog-
coyote-wolf genus is called Canis, the robin genus, Memla,
and the house-fly genus, Mnsca.

Each species belonging to these genera also has a specific
proper name, the dog's species name being familiaris, the
coyote's latrans, the gray wolf's occidentalis, the robin's migra-
toria, and the house-fly's domestica. But because of the
enormous number of kinds of animals we do not try to have
a separate single word name for each species, but always com-

52 ECONOMIC ZOOLOGY AND ENTOMOLOGY

bine the species name word, which may be used repeatedly,
that is, used for several different species, with the name of
the genus to which the species belongs, and thus make a two-
word name, or "binomial," for each animal kind. These,
two-word names distinguish the species unmistakably from
each other because although the same word, familiaris, may
be used for several or even many different species it is never
used for more than one species in any given genus, and the
genus name is never used for more than a single genus. So
that Can is familiaris, the scientific two- word name for the dog
species, unmistakably distinguishes the dog by name from
all the other half million species of animals we know. There
might be a Merula familiaris, or a Musca familiaris in the list,
but not a second Canis familiaris. You will have noticed
that we have capitalized the first or genus word in the two-
word scientific name of the dog, but not the second or species
word. And this is the rule in zoological nomenclature. Even
if the species word is derived from a proper name, as is often
the case, it is not capitalized. The botanists do not adhere to
this rule, so that they might write Canis Browni, if Canis were
the genus name of a plant and Browni the species name.

Just as there are often several and sometimes many species
sufficiently alike, or better, closely enough related, to be
grouped together into one genus, so there are usually several
or many genera related closely enough to be brought together
into a group of a higher or more comprehensive degree. There
are, for example, other genera of animals showing unmistakable
affinities, by their resemblances of structure, with the dog and
wolf genus Canis. Such for example are the genera Vulpes
and Urocyon which include various species of foxes. These
related genera are then grouped together to form a family; in
this case the family Canidce. Note that the proper name of
this family is made by adding idee to the stem part of the name
of one of the genera in it. That is, the name of an important
genus in the family is taken in the genitive case and pluralized
in order to make the family name. And this is a general rule
in zoological nomenclature.

Related families are grouped together to form orders.

THE CLASSIFICATION OF ANIMALS 53

Plainly related to the Canidce, for example, are the F elides, or
cats and cat-like animals, the Ursidce,, or bears, Mustelidce or
weasels, and some other families all of whose members are
carnivorous in habit and have teeth, feet, and other parts
specially modified in connection with this habit. All of these
families then are grouped together to form the order Carnivora.
All the families of hoofed animals, as the Equidce or horses, the
Bovidce or cattle, the Cervidce or various deer kinds, and other
similar families, compose the order Ungulata. But all the
animals of both Carnivora and Ungulata as well as of a number
of other orders agree in possessing certain important common
characteristics of structure and physiology, which undoubtedly
indicate a certain relationship. And so they are grouped to-
gether to form a class. The particular class comprising the
orders just spoken of is named the Mammalia, from the posses-
sion by all of its members of milk glands for producing milk
for their young.

Finally there is a plain relationship among the class Mam-
malia or mammals, and the class Aves, or birds, the class
Reptilia, or reptiles, the class Amphibia, or batrachians and the
class Pisces or fishes. They are all back-boned animals, while
other animals are not. They may be grouped together into
a single large group called a branch. The name of this branch
is the Chordata. There are eleven other branches in the animal
kingdom, all of which are named and divided into their classes
in the table on pages 55 to 57.

The branches are the largest groups used in the classi-
fication of animals, so that if we should now tabulate the
scientific classification of our dog we should find it to belong
to the

kingdom Animalia
branch Chordata
class Mammalia

order Carnivora
family Canidce
genus Canis

species familiaris.

Its scientific name is, however, simply Canis familiaris, which
indicates, to a zoologist, the whole classification of the dog.

54 ECONOMIC ZOOLOGY AND ENTOMOLOGY

Because as there is but one animal genus named Canis and
that is a member of the family Canidas, which in turn is a
member of the order Carnivora, which is a member of the
class Mammalia, which, finally, belongs to the great branch
Chordata, we have indicated all the superior groups by naming
the generic one only, and have pointed out what particular
species of that genus we are referring to, when we simply
say or write Canis familiar is.

There are many rules of custom which zoologists try to
follow in deciding on names for new kinds and groups of ani-
mals, but they are too many and too technical to discuss here.
However it is worth while to point out that while the scientific
name of an animal may be more or less descriptive by the
meaning of its genus and species words, it is not necessarily
so. Canis familiaris is, translated, the common dog; Canis
latrans, the barking dog; and Caws occidentalis the western dog,
which are all therefore names of descriptive nature. But
there might be a wolf named Canis smithi, which would not
describe it at all. The name however would be a perfectly
proper scientific name. There are indeed hundreds of scien-
tific names which have no or almost no descriptive significance
at all; and some that are even wrongly descriptive. For ex-
ample a Russian naturalist might find in the wilds of Siberia
a new kind of wolf, larger than any other kind known. He
might name it therefore, descriptively, Canis maximus, the
largest wolf. In the next year an American naturalist might
find a still larger species in the heart of Alaska. But the name
Canis maximus would always be used for the smaller Siber-
ian wolf, because the scientific name is primarily a symbol,
an arbitrary name, and not a description. And also the ad-
vantage of having the first name Applied to a species retained
for all time is very great. The stability of the system and its
convenience depend largely on the custom of not changing the
names unless absolutely necessary because of some original
mistake in assigning the species to a wrong genus, or the
necessity of dividing too bulky genera into smaller ones.

Branches and Classes of Animals. The following table gives
the names and arrangement of all the branches and classes of

THE CLASSIFICATION OF ANIMALS 55

the animal kingdom. No attempt should be made now to
memorize this table.

ANIMAL KINGDOM

BRANCH I. PROTOZO'A (one-celled animals)

Class I. Rhizdp'oda (amoeba, Heliozoa, Radiolaria, Foraminif-

era, et al.).

Class II. Mycetozo'a (slime-moulds).
Class III. Mastigoph'ora (whip-bearers, Euglena, trypanosomes,

Spirochcsta, et al.).
Class IV. Sporozo'a (parasitic Protozoa such as Plasmodinm

which causes malaria, Babcsia which causes Texas

fever of cattle, et al.).
Class V. Infuso'ria (mostly free-swimming Protozoa provided

with cilia, Paramcecium, Vorticella, et al.).

BRANCH II. PORIF'ERA (sponges)
Class I. Par if era (sponges).

BRANCH III. CCELEN'TERA'TA (se-len-te-ra'-ta)

(Aquatic, mostly marine, radially symmetrical ani-
mals having a combined body and stomach cavity)
Class I. Hydrozo'a (fresh water hydra, marine hydroids, many

of the small jelly-fish, a few stony corals, et al.).
Class II. Scyphozo'a (si-fo-zo'-a) (most of the large jelly-fishes).
Class III. Actliwzo'a (sea-anemones; most of the corals, et al.).
Class IV. Ctenoph'ora (ten-oph'-o-ra) (the comb- jellies, or sea-
walnuts).

BRANCH IV. PLATYHELMIN'THES (flat-worms)

Class I. Turbellar'ia (planarians, et al.).
Class II. Tremato'da (liver-flukes, et al.).
Class III. Ccsto'da (tape- worms).

BRANCH V. NEMATHELMlN'THES (round-worms)

Class I. Nemato'da (trichina, hookworms, et al.).

Class II. Nematdmor 1 pha (horse-hair snakes, or cabbage- snakes,

et al.).

Class III. Acanthocepli'ala (thorn-headed worms).
Class IV. ChcstSg'natha (ke-t5g'-na-tha) (arrow- worms).

56 ECONOMIC ZOOLOGY AND ENTOMOLOGY

BRANCH VI. TROCHELMIN'THES (wheel-worms)
Class I. Rotif'cra (wheel animalcules).

BRANCH VII. MOLLUSCOI'DA

(small animals which are more or less mollusc-like)

Class I. Polyzo'a (moss-animals).

Class II. Phord'nida (worm-like animals living in sand).
Class III. Brachiop'oda (lamp-shells, small marine animals with
a bivalve shell).

BRANCH VIII. ECHINODER'MATA

(radially symmetrical, marine animals with a rough
or spiny skin)

Class I. Asteroi'dea (starfishes).
Class II. Ophiui'oi'dea (brittle-stars).

Class III. Rchlnoi' dea (sea-urchins).

Class IV. Holothurol'dea (sea-cucumbers).
Class V. Crinoi'dea (sea-lilies, or feather-stars).

BRANCH IX. ANNEL'IDA (segmented worms)

Class I. Archiannel' Ida (marine worms living in the sand).

Class II. Chcetop'oda (earthworms, Nereis, et al.).

Class III. Gephyre'a (jef-e-re'-a) (marine, worms of uncertain
relationship, with little or no traces of segmenta-
tion in the adult).

Class IV. Hinidm'ea (leeches)

BRANCH X. ARTHROP'ODA

(animals with the body more or less distinctly seg-
mented and with jointed appendages)

Class I. Crusta'cea (crayfish, lobsters, crabs, shrimps, et al.).

^lass [I. OnychSph'ora (slime-slugs).

Class III. Myrldp'oda (myriapods, centipedes, et al.).

Class IV. Insec'ta (insects).
, Class V. Ardch'nida (scorpions, spiders, mites and ticks).

BRANCH XI. MOLLUS'CA

(bilaterally symmetrical, unsegmented animals, most
of which have shells)

Class I. Amplnncu'ra (chitons, et al.).

Class II. Gastrop'oda (snails, slugs, et al.).

Class III. Scaphop'oda (tooth-shells).

Class IV. Pclecyp'oda (clams, mussels, oysters, scallops, et al.).

Class V. Ccphalop'oda (squids, octopods and nautili).

THE CLASSIFICATION OF ANIMALS 57

BRANCH XII. CHORDA'TA

(animals that have a notochord at some stage of their
development)

Class I. Adelochor'da (balanoglossids, et al.).

Class II. Urochor'da (ascidians, et al.).

Class III. Leptocard'ii (lancelets).

Class IV. Cydostom' ata (lampreys and hagfishes).

Class V. Pisces (pis-sez) (fishes).

Class VI. Amphib'ia (frogs, toads, salamanders, water-dogs,

et al.).

Class VII. Repttt'ia (snakes, lizards, turtles, alligators, et al.).
Class VIII. A'ves (birds).
Class IX. Mammal' 'ia (mammals).

CHAPTER IX
SPONGES, AND SPONGE FISHING

The sponges are fixed, aquatic, plant-like animals living
mostly in salt water. They are regarded as representing the
simplest type of Metozoan body structure and cell specializa-
tion, and are classified as a branch of the animal kingdom
called Porifera. The body of the simplest sponges is vase-
shaped or cylindrical with the base attached to a rock or shell
or other firm substance. At the free end there is an opening
that leads down into the central cavity. The walls surround-
ing this cavity are perforated by numerous openings or canals
through which the water flows.

Few sponges are of this simple vase-like appearance, how-
ever. Most of them are unsymmetrical, and cling close to
the surface on which they grow, or form low compact bushy
bodies looking much more like plants than like animals.

Sponges belonging to the genus Grantia are convenient types
for study. They live in salt water and may be 1 obtained at
many points on the Atlantic or Pacific Coasts on rocks,
shells or other objects below low water line. They are sub-
cylindrical in form, attached at the base, and with a rather
large opening, the exhalant opening, or osculum, at the free end.
All over the sides are numerous small openings leading into the
inhalant canals which extend almost to the inner or gastric
cavity or cloaca. Opening into the cloaca and extending
almost to the outer wall are other canals, the radial canals.
The inhalant and radial canals run side by side and communi-
cate with each other by means of very small openings. The
cells lining the radial canal are furnished with long lashes, or
flagella, the lashing of which sets up currents of water which

1 Inland schools can obtain specimens preserved in alcohol or formalin
from dealers in natural history supplies.

58

SPONGES, AND SPONGE FISHING

59

passes in through the inhalant canals and through the small
openings into the radial canals on into the cloaca and out
through the exhalant opening at the free end of the sponge.
The cells lining the radial canals and the cloaca take up and
digest particles of food that are brought in by the currents of
water. Some of this digested food is passed by osmosis to the
adjacent cells which do not take up any food. Here we see a
simple step in physiological division of labor. The outer cells

FIG. 13. A group of vase-shaped sponges, Lcucandra apicalis. (Natural

size.)

which compose the ectoderm, or outer skin, serve to protect
the animal, while the inner cells, which make up the endoderm,
digest the food and feed the other members of the colony.
The currents that bring the food also bring fresh oxygen in the
water. Some of this is taken up by the cells, while the carbon
dioxide and other waste products that they excrete are carried
away by the same currents.

Between the ectoderm and the endoderm, and pierced by

60 ECONOMIC ZOOLOGY AND ENTOMOLOGY

the inhalant and radial canals, is the soft gelatinous-like
layer, the mesoderm, that is composed of various kinds of cells.
Some of these are concerned in the formation of the spicules
that make up the framework, some are concerned with diges-
tion and some with reproduction. Two or three kinds of spic-
ules may be found in the mesoderm of Grantia. They are
composed of carbonate of lime, and are very brittle when dry.
The framework of the commerical sponges is composed of
exceedingly fine flexible fibers of a horny substance called
s pong-in. This is the part of the animal that we commonly
know as the sponge in the market.

Grantia reproduces itself in two different ways. Small buds
sometimes appear on the external surface of the body which
develop into small individual sponges. These gradually
increase in size and finally break away from the parent and
attach themselves to some other substance. In the more
complex sponges these buds do not break away, but remain
attached so that in time there is built up a complex sponge
colony.

Besides this method of reproducing asexually, that is, with-
out the union of two kinds of germ cells, all sponges have a
mode of sexual reproduction. The male, or sperm, cells and
the female, or egg, cells are produced in the same individual.
The sperm cells when ripe are cast into the water and swim
about until they come in contact with egg cells which they
fertilize. From these fertilized egg cells sponge embryos
develop which, after they have reached a certain stage, swim
away by means of many cilia which cover their bodies and
finally attach themselves to some substance where they remain
the rest of their lives.

Sponges of Commerce. All sponges have the same general
type of structure but most of them branch extensively and
form immense colonies with innumerable canals and cavities
making altogether a complicated network. The sponges that
we use are really only the skeletons of some of these great
colonies with all of the soft parts dried or squeezed or washed
out. Bleaching powders or acids are sometimes used to
lighten the color, but they are apt to injure the fibers. The

SPONGES, AND SPONGE FISHING

61

best sponges come from the Mediterranean. This region
annually produces about $2,000,000 worth of sponges, which
is more than half the value of the product of the sponge
fisheries of the world. Some sponges come from the Red
Sea, others from the Bahama Islands, West Indies, the west
coast of Florida and other places. The annual output from
the Florida sponge fisheries is valued at between $500,000 and
$600,000. The commercial sponges do not live in very deep

FIG. 14. A common bath sponge. (Reduced.)

water, being usually found not deeper than 200 feet. In shal-
low water they are dragged from the rocks by men in boats
who use long poles with hooks on the ends. Those growing in
deeper water are dredged up or brought up by divers.

Many of the best sponge-fishing grounds have suffered very
severely from destructive methods of fishing and efforts are
now being made to protect these beds and to stock others.
Several methods of sponge culture have been tried, most of

62 ECONOMIC ZOOLOGY AND ENTOMOLOGY

them with little or no success. The United States Bureau
of Fisheries has found a method that it believes to be practi-
cable. Live sponges are cut into small pieces which are
fastened on some firm support and placed in suitable places.
In from four to six years these fragments grow to a good
marketable size.

Boring Sponges. Among the most interesting and impor-
tant of the sponges are the boring sponges which live on shells,
spreading over the surface at first but eventually penetrating
the shell in every direction, completely honeycombing it, and
causing it to break up. They thus help to dispose of the shells
of dead molluscs which would otherwise accumulate in vast
quantities. They also attack shells in which the animals are
still living and by boring through the shell greatly irritate the
host which must constantly secrete new shell to close up the
holes made by the intruder. These boring sponges are often
serious pests in the oyster beds. The pearl-shell fishermen
sometimes find some of their largest and otherwise finest shells
completely ruined by the work of some of them.

Classification. There is only one class belonging to the
branch For if era (L. poms, pore; fero, to bear) and that, too,
is called Porifera. It is divided into two sub-classes, the
Calcarea, including those sponges with a skeleton of calcareous
spicules, and the Non-calcarea, with the skeleton either absent
or composed of spong in fibers or of siliceous spicules. Grantia
is an example of the sub-class Calcarea; the commercial
sponges, the boring sponges, and indeed most of the others,
belong to the Non-calcarea.

CHAPTER X
CORALS, SEA-ANEMONES AND JELLY-FISHES

Like the sponges, most of the polyps, and jelly-fishes, com-
posing the branch Ccelenterata (Gr. koilos, hollow; enteron,
intestine) are found in the sea. Those who live near the sea-

FIG. 15. Sea-anemones. The middle specimen expanded and feed-
ing; lower specimens partly or wholly contracted and with disk closed.

shore are familiar with the many-colored, flower-like sea-
anemones that cover the rocks in shallow water, and with the
clear transparent medusae or jelly-fishes, which truly look
like masses of animated translucent jelly. Less familiar are

63

64 ECONOMIC ZOOLOGY AND ENTOMOLOGY

the little tree-like hydroids that are found on the submerged
rocks or shells along the shore at all depths. These little
animals look so plant-like that they are often called zoo-
phytes, or plant-animals, a name that is also applied to other
polyps. Many of them however live a part of their lives as
active, free-swimming forms before they settle down to be-
come attached to the places where they are to remain. In
the shallow waters of all tropical seas the coral polyps grow in
such numbers that their myriad skeletons form whole groups
of little islands and great projecting barrier reefs that may
reach for miles along the shores. The great barrier reef off
the north shore of Australia is more than a thousand miles
long. Only a few of the polyps live in fresh water. Hydra,
which is found in nearly all fresh water ponds or streams, is
the most familiar example, and has already been studied.

Hydroids and Jelly-fishes. In each of the four groups, or
classes, into which the polyps and jelly-fishes are divided there
are many modifications of the simple type plan presented by
Hydra. If the buds that develop on Hydra should remain
attached and continue to grow and in turn produce other buds,
there would soon be developed a tree-like colony with a Hydra-
like animal at the end of each branch. Some marine animals
are developed in just this way, and are known as hydroids. The
class Hydrozoa (Gr. hydor, water; zoon, animal) to which these
belong includes the Hydra and other Hydra-like animals. The
Hydrozoan colonies may be made up of two kinds of in-
dividuals, or zooids. One kind, known as the nutritive zooids,
or polyps, retains much of the general appearance of the
Hydra; the other kind, known as the reproductive zooids, or
medusae, develop into quite different looking animals. The
medusas are produced by budding off from the bases of the
polyps. They are umbrella-shaped, jelly-like masses and are
commonly known as jelly-fishes. After budding off from the
polyps they float and swim in the water for some time and
finally produce egg cells and sperm cells. From each fer-
tilized egg a new individual develops. This new individual
is at first an active free-swimming larva, called planula, which
does not resemble either a medusa or a polyp. After a while

CORALS, SEA-ANEMONES AND JELLY-FISHES 65

it settles down, becomes fixed, and develops into a polyp.
Thus a polyp may produce a medusa or jelly-fish which, how-
ever, produces not a new jelly-fish, but a polyp. This is called
an alternation of generations, and is not an uncommon phenom-
enon among the lower animals. It results from such an al-
ternation of generations that a single species of animal may
have two distinct forms. This having two different forms is

FIG. 1 6. A jelly-fish, or medusa, Gonionema vertens, eating two small
fishes. (From specimen from Atlantic Coast.)

called dimorphism. Sometimes, indeed, a species may appear
in more than two different forms; such a condition is called
polymorphism.

The Portugese man-of-war, common in tropical seas, is a
representative of another group of this class. It appears
as a delicate bladder-like float, brilliant blue or orange in
color, usually about six inches long, and bearing on its upper

66 ECONOMIC ZOOLOGY AND ENTOMOLOGY

surface, which projects above the water, a raised parti-colored
crest, and on its under surface a tangle of various appendages,
some thread-like and others in grape-like clusters of little
bell- or pear-shaped bodies. Each of these parts is a peculiarly
modified polyp- or medusa-zooid, produced from budding
from an original central zooid. Many other kinds of colonial
jelly-fishes occur which show similar differences among the
different members of the colony. Some individuals enable
it to move through the w T ater, some protect the colony, others
procure or digest food and still others are modified into re-
productive organs. The whole colony, or compound animal,
floats or swims at the surface of the water and performs all
the necessary functions of life as a single animal composed of
organs might.

Most of the common large jelly-fishes belong to a second
group (class Scyphozoa: Gr. skyphos, cup; zoon, animal). They
often occur in great numbers on the surface of the ocean.
Others live in deeper waters, a few having been dredged up
from depths of even a mile below the surface. The umbrella-
shaped bodies vary in size from less than an inch to more than
six feet in diameter. From the underside of the central part
of the body hangs a mass of long tentacles which are provided
with stinging-threads. The small animals that become en-
tangled in these tentacles, which sometimes reach a length
of more than 100 feet,, are stung by the stinging-threads and
serve as food for the jelly-fish. The body substance of some
jelly-fishes is more than 99 per cent, sea-water. Most of
them are nearly transparent, but some are beautifully colored
and many are phosphorescent.

Sea-anemones and Corals. The most familiar examples of
the polyps and jelly-fish branch of animals are the multi-
colored sea-flowers, or sea-anemones, found along all ocean
shores. The petal-like tentacles, that surround the central
mouth-opening spread wide and seize and thrust into the
mouth any small animals that may walk or swim into this
living trap. Less common are the beautiful sea-pens, sea-
feathers and sea-fans which are closely related to the sea-

CORALS, SEA-ANEMONES AND JELLY-FISHES 67

anemones. All these belong to the class Actinozoa (Gr. aktis,
ray; zoon animal).

To this class belong also the interesting coral polyps that are
found in all tropical and sub-tropical seas. The individual
coral polyps are not unlike the sea-anemones in general ap-
pearance and structure, but they usually live in great colonies,
forming large irregular or branching tree-like masses. As
the animals grow they secrete a strong skeleton of carbonate
of lime. The corals with which most of us are familiar are

FIG. 17. Branching coral, Acropora muricata, from Samoa. (Much

reduced.)

really only the calcareous skeletons of innumerable little
polyps. The living coral is quite different in appearance from
this hard stony skeleton. The surface is often soft and velvety,
pink, green, yellow, brown or purple, and covered with the
small waving tentacles of the numerous little polyp individuals
that make up the colony. As each individual polyp dies and
leaves its skeleton it is adding its small mite toward the for-
mation of the great coral rocks or reefs or islands charac-
teristic of the tropical seas. Coral polyps usually do not live

68 ECONOMIC ZOOLOGY AND ENTOMOLOGY

more than fifteen or twenty fathoms below the surface of the
water, so we find the reefs as fringing reefs lying attached to
some shore line, or as barrier reefs, lying a little further out and
separated from the land by an intervening lagoon. Or they
may be in the condition of atolls, which make up groups of small
coral islands, each surrounding a more or less circular or oval
lagoon. These coral islands are themselves often protected
by barrier reefs. The foundations upon which the coral
atolls rest are probably the summits of submarine mountains
which come to within 100 or 150 feet of the surface. On
such places coral polyps and many other kinds of marine
animals and plants grow, and accretions due to these and
other substances slowly raise the bank toward the surface
of the water, so that at low tide the tips of the growing
branches of the coral may be above the surface. As the
coral is broken and ground into fine bits by the action of the
waves and as other pieces are washed higher on top of these,
the island gradually rises above the level of the tides. The
waves continue to break up some of the coral into fine
particles, that, together with other debris, forms a little cal-
careous soil in which may germinate the seeds carried to it by
birds or ocean currents. With the growth and decay of vege-
table life the soil gradually becomes more fertile, until finally
the islands may become covered with a luxuriant plant growth
which in turn serves as the home of many insects and birds and
other animals.

There are over 200 kinds of coral polyps known. Many
kinds are used for ornaments or decoration. The red coral,
which grows chiefly in the Mediterranean, is much used for
jewelry. The rose-pink coral is very valuable, some of the
finest kinds selling for hundreds of dollars an ounce.

To the class Ctenophora (Gr. kteis, comb; phero, bear)
belong a few peculiar delicate, transparent, medusoid jelly-
fish, swimming by means of the rhythmical beating of several
rows of vibratile plates and not by means of the motion of
the bell or umbrella as in the case of other jelly-fishes.

CHAPTER XI

THE LIVER-FLUKES, TAPE- WORMS, AND OTHER
PARASITIC FLAT WORMS

The Worms. In the older classifications the name Vermes
was applied to a large group of worm-like creatures which
resembled each other in some respects, but as these animals
came to be better known it was found that some were not at
all closely related to others and it became necessary to divide
the group into five smaller groups of equal rank, the flat worms
(Platyhelminthes,) the round worms (Nemathelminthes), the
rotifers (Trochelminthes), the sea-mats and lamp-shells
(Molluscoidea) and the segmented worms (Annelida). These
all differ from the polyps and sponges by being bilaterally
symmetrical and in having three well-developed layers of
cells in the body-wall, the mesoderm being well developed.
Usually, also, the various systems of organs are much more
complex, and the individuals do not form colonies.

The first group (the branch Platyhelminthes; Gr. platus,
broad, helmins, worm) includes the liver-flukes, tape-worms
and other parasitic flat-worms, and a few free living flat worms
that live in fresh water or salt water, or, more rarely, on land.
They are usually much flattened and without true segmenta-
tion, although the bodies of the tape-worms have a jointed
appearance owing to their being largely made up of a string of
reproductive units. Many of the parasites have very com-
plex life histories and live in different kinds of animals while
passing through their successive stages of development.

Fresh-water Planarians. In the mud at the bottom of
ponds of fresh water or clinging to the rocks or sticks in
such places are often found small flat creatures that are known
as planarians. They look somewhat like small leeches, which
belong to the branch Annelida, but may be distinguished

69

yo ECONOMIC ZOOLOGY AND ENTOMOLOGY

from them by the absence of rings around the body. These
planarians are less than half an inch long, very thin and
rather broad. On the upper surface near the front is a pair
of pigmented spots which are probably sensitive to light and
are called the eyes. The mouth is on the under surface a
little behind the middle of the body. The alimentary canal
is composed of three main branches, each with numerous
small side branches. One main branch runs forward from
the mouth, and the other two run backward, one on each side
of the body. There is no anal opening, and the alimentary
canal thus forms a system of fine branches closed at the
tips, and extending all through the body. The nervous
system is composed of a ganglion or brain in the front end of

FIG. 1 8. A fresh- water planarian, Planaria sp. (Eight times natural
size; from a living specimen.)

the body from which two main branches extend back through-
out its whole length. From these main longitudinal branches
arise many fine lateral branches.

Many beautiful and interesting members of the class
Turbellaria the class to which the planarians belong are
marine and a few are found in moist earth.

Liver-flukes. 'The liver-flukes, Fasciola hepatica, live as
parasites in the liver of sheep and cattle, especially the former.
In Europe they sometimes kill hundreds of thousands of sheep
annually, and they have more recently become of some import-
ance in the United States, the Pacific and the Gulf Coast
regions suffering most. They are interesting not only on
account of their economic importance but because they furnish
a good example of a Metazoan parasite that requires two
different kinds of hosts in which to complete the different stages

THE LIVER-FLUKES, TAPE- WORMS, ETC. 71

of its development. The adult fluke, which occurs in the
sheep's liver, has a flattened leaf-like body, and is from three-
quarters of an inch to more in length. There are two suckers
on the ventral side, one surrounding the mouth, the other
nearer the anterior end. Their presence in the liver produces
a disease known as liver rot because the tissues of the liver
degenerate. Affected sheep often die.

The flukes are hermaphroditic, and each individual is capable
of producing about five hundred thousand
very minute eggs. These pass through the
bile ducts of the host into the alimentary
canal and thence with the excrement to the
ground. If the eggs fall on dry ground they
usually perish, but if they fall on damp herb-
age or in water there hatch from them small
ciliated larvae. These swim about in the
water for ten or twelve hours, and, if they
do not happen to come in contact with a
certain kind of snail, they perish. Those
that do succeed in finding a snail bore their
way through any of the soft parts into the
body, where they undergo certain changes,
finally forming sporocysts within which are

developed small larvae called redice, which in

,T ,. /T>, j- r 11 hcbatica. (Nearly

turn produce other rediae. I he rediae finally t ^ j c e n a t u r a'l

give rise to certain heart-shaped bodies each size.)
with a long flexible tail. These are called cer-
carics, and in this shape the parasites issue from the snail
host. Soon after leaving the snail the cercariae become en-
cysted and within the cyst further changes take place, the
animal becoming more like a minute adult fluke. If these
cysts are swallowed by a sheep when it is eating grass or
drinking water where they occur, the cyst is dissolved by the
digestive juices in the sheep's stomach and the young flukes
are liberated. They soon work their way from the stomach
to the duodenum and through the bile duct into the liver,
where they develop into the adult flukes.

It will be seen that under ordinary conditions there is little

FIG. IQ. Liver-
fluke, F as do I a

72 ECONOMIC ZOOLOGY AND ENTOMOLOGY

chance of many of the thousands of eggs that are produced
by the adult fluke ever meeting successfully all the danger
that beset their path. The eggs may fail to reach the water; or
if hatched the larvae may not be able to find a snail; or if the
snail is found it may be destroyed before they have completed
their transformations. The cercariae are always in danger of
being eaten by aquatic animals while in the water, or if not
eaten after they form their cysts the particular blade of grass
to which they are attached may never be eaten by a sheep.
Yet the number of eggs that are produced is so great that
hosts of the young flukes do successfully overcome all their
difficulties and infect so many sheep that they become an
important economic factor in sheep-raising in many regions.

With a knowledge of the life history of the parasite, however,
it is a comparatively easy matter to prevent the infection of the
sheep. This is accomplished by keeping them away from land
subject to overflow, or where the snails occur in numbers.
Springs and other watering places are particularly dangerous
when there are many snails about them.

This same species of liver-fluke, Fasciola hepatica, some-
times occurs in cattle, horses and other domestic animals
and even, although very rarely, in man.

Other Flukes. The large American fluke, Fasciola magna,
which is often a serious pest of cattle in the Southern states,
also occurs in the deer, which was probably its original host.
The life history has not yet been worked out, but it is probably
somewhat similar to that of the liver-fluke of sheep. Another
species of fluke is common in ducks, and many other animals
may be more or less seriously affected by still other kinds.
One species occurring in Egypt is a dangerous parasite of man,
infesting the urinary and abdominal blood-vessels where it
causes serious inflammation. The infection is probably from
bad water.

Some species are external parasites and attach themselves to
their hosts by means of a series of suckers. One kind that
attaches itself to the gills and fins of fresh-water fishes is
viviparous, that is, it brings forth its young alive, and the
embryo, before it is extruded, itself contains another embryo

THE LIVER-FLUKES, TAPE-WORMS, ETC. 73

and this in turn still another embryo so that three generations
of embryos are present one within the other.

Tape-worms. The tape-worms are the most common and
the best known of the flat worms. There are many species,
the adults of all of which live in vertebrate animals. But there is
almost always an alternation of hosts during the life of the
parasite, the larval tape-worm living in one animal and the
adult in another. In the larval stage the tape-worms may
occur in various parts of the body of the intermediate host,
but the adult or fully developed worm always occurs in the
alimentary canal of the final host. Many of the domestic
animals suffer from these parasites. At least ten different
species of tape-worms have been found in the dog, the inter-
mediate hosts including rabbits, sheep, and other animals
that the dog may feed on. Many of the domestic fowls are
infected by tape-worms, whose intermediate hosts are insects
or small aquatic crustaceans, like Cyclops.

Several kinds of tape-worms infest man. Tania solium,
whose intermediate host is the pig, may serve as an example
of the group. The adult worm is attached to the inner wall of
the intestine of man by a number of fine hooks with which the
small head is provided. The long, ribbon-like, symmetrical
body lies free in the alimentary canal, where it absorbs the
liquid food directly through its thin body-wall. The parasite
has neither mouth nor alimentary canal. The body may
reach a length of many feet and be composed of as many as
850 segments, or proglottids. Each proglottid produces both
sperm cells and egg cells, and as these become mature the
posterior proglottids drop off one by one and pass out of the
alimentary canal with the excreta. If some of these escaped
proglottids are eaten by a pig the embryos issue from the eggs,
bore through the walls of the alimentary canal of the host, and
make their way to the muscles, where they increase greatly in
size and develop into a rounded sac filled with liquid. In this
stage they are large enough to be readily seen, and the infected
spotted meat is called "measly pork." If such infected pork
is eaten by man without being cooked sufficiently to kill the
parasites, the young tape-worms will attach themselves to the

74 ECONOMIC ZOOLOGY AND ENTOMOLOGY

FIG. 20. Some segments of the tape-worm, Tcsnia saginata, from man.

(About natural size.)

THE LIVER-FLUKES, TAPE-WORMS, ETC. 75

walls of the alimentary canal and soon develop into the
many-jointed adult. Tape-worms cause much trouble, espe-
cially to children.

It is probable that the most common tape-worm affecting
man in the United States is one that passes its intermediate
stage in cattle. It is known as Tcenia saginata, and is much like
T. solium, but the head is depressed instead of being convex
at the end, and the hooks, which are conspicuous in T. solium,
are wanting in T. saginata.

It is plain that either one of two things is necessary to
prevent infection; all meat must be carefully inspected and
any that is "measly" rejected, or it must all
be so thoroughly cooked that there will be
no chance for any of the encysted forms to
remain alive.

FIG. 21. Head of
tape-worm, T & n I a
saginata. (Highly
mag n i fi ed ; after
Wood.)

FIG. 22. A piece of a muscle of the ox, with
three specimens of the tape-worm, Tcenia saginata,
in encysted stage. (Natural size; after Osterberg.J

If a child or an older person becomes infested a physician
should be consulted, as many of the vermifuges that are often
recommended are unsafe.

A serious disease of sheep, known as gid, is caused by the
cysts, or " bladder- worms, " of a tape-worm, Multiceps multiceps
(Ccenurus cerebralis), the adult stage of which is passed in the
intestine of the dog. The proglottids pass from the dog in the
feces and the eggs are released and splashed on the grass or
washed to pools where the sheep drink when the rains come.
When the eggs are taken into the stomach of the sheep the
embryo is released and makes its way into the blood-vessels and

76 ECONOMIC ZOOLOGY AND ENTOMOLOGY

finally to the central nervous system. In the brain it grows
rapidly to the size of a hazelnut, or larger, the sheep, of course,

FIG. 23. The gid parasite, Multiceps multiceps, in bladder- worm stage
from brain of sheep. (Much reduced; after Hall.)

suffering from the movements of the parasites and their
presence in the brain. The infected sheep usually dies and
when its brain infested with the "bladder-worms" is eaten by

FIG. 24. Adult gid tape-worm, Multiceps miiHiceps, from the intestine
the dog. (Natural size; after Hall.)

a dog or some other carnivore many more tape-worms are
produced in the new host.

THE LIVER-FLUKES, TAPE-WORMS, ETC. 77

This disease has been a serious scourge of sheep in Europe
for centuries, and for a long time has existed in Montana where
the loss is at least $10,000 every year. The number of the
parasites may be partially controlled by keeping only a few
dogs around the sheep or in regions where they are feeding,
and by keeping these dogs free from tape-worms. The dogs
should never be allowed to feed on the carcasses of the sheep
that have died from the disease, nor is it well to let them feed
on the heads of slaughtered sheep that may be infected.

Classification of the Flat-worms. The Platyhelminthes are
divided into three classes, the Turbellaria, the Trematoda,
and the Cestoda. Another class, the Nemertea, is sometimes
included in this branch, but its relation is doubtful. Its
members are of no economic importance.

The Turbellaria (L. turbellce, disturbance) are mostly non-
parasitic and have the epidermis covered with cilia. The
fresh-water planarians are examples.

The Trematoda (Gr. trema, perforation; eidos, likeness)
are all either external or internal parasites. The life history,
especially of the internal parasites, is often very complicated,
as we have seen in our study of the liver-flukes.

The Cestoda (Gr. kestos, a girdle, eidos, likeness) are all in-
ternal parasites in whose life history there occurs a tape- worm
stage in a vertebrate host and a bladder-worm stage in a
vertebrate or invertebrate host. The tape- worms of man and
of other animals are examples of this class.

Parasites and Pearls. After calling attention to so much
harm that these lowly parasites may cause it is only fair that
a paragraph should be given to pointing out how a few of them
are of some service to man. For a long time it has been known
that the pearls that are found in many molluscs are secretions
formed about foreign particles that have found their way in-
side the shell. It is now known that the larvae of several
Trematode and Cestode worms are the objects around which
some of the finest pearls are formed. The Trematode larvas
are most common in mussels, while the Cestodes are found
very abundantly in the pearl oysters of Ceylon and other parts
of the world. The vertebrate hosts in these instances are

7 8 ECONOMIC ZOOLOGY AND ENTOMOLOGY

usually certain fish that feed on the molluscs. In these the
adult parasite lives, and some of the young embryos that are
set free in the water gain access to the gills, liver or mantle of
the molluscs. Here many go on with their development until
the mollusc is eaten by a fish and the life cycle is begun again.
In some instances, however, the irritation due to the presence
of the parasite causes a calcareous secretion, like that forming
the shell, to be deposited around the parasite. This forms the
nucleus of a pearl which grows by additional layers being
deposited around it, the luster depending on the kind of mollusc
in which it is found. "The most beautiful pearl is only the
brilliant sarcophagus of a worm."

CHAPTER XII

TRICHINA, HOOKWORMS, FILARIA, AND OTHER
PARASITIC ROUND-WORMS

The large group of hair-like or thread-like unseg-
mented worms, constituting the branch Nemathel-
minthes (Gr. nema, thread; helmins, worm), includes
certain kinds which on account of their parasitic
habits are of very great economic importance. Per-
haps the most familiar examples of the branch are
the hair-worms, or horse-hair snakes, which are often
found in watering troughs or pools of water. Be-
cause of their remarkable appearance many persons
believe them to be horse-hairs that have dropped
into water and changed into these animals. They
really come mostly from the bodies of insects in
which they pass a part of their lives as parasites.
The vinegar-eel, which is found in weak vinegar is
another common example of the group.

Trichina. The dreaded trichina, Trichinella
spiralis, which causes the disease called trichinosis,
is a minute round-worm the adults of which live
in the intestine of man, pigs and other animals.
These adults produce living young which bore
through the walls of the intestine, and are carried
by the blood, or otherwise make their way to the
muscles, where they form little cells or cysts in
which they lie. The presence in the muscles of ^Fic. 25.
thousands or millions of these little parasties often ^ eg ,^ ( e / (J '
causes great suffering, sometimes death to the host. sp
It has been estimated that the trichinosed flesh of
a human subject may contain 100,000,000 of these
encysted trichinae. Before further development of specimen.)

79

( Great -
1 y magni-
fied; from
a living

8o ECONOMIC ZOOLOGY AND ENTOMOLOGY

the worms can take place such trichinosed flesh must be eaten
by another animal in which they can live. Pigs are probably
usually infected by eating dead infected rats or scraps of pork
that have been thrown out in garbage. Man is usually in-
fected by eating trichinosed pork. In the alimentary canal of
the new host the trichinae escape from the cyst and after be-
coming sexually mature produce the young which migrate to
the muscles again.

The close watch that the government inspectors keep over
the meats that go out from all the great packing houses makes

the dangers from all parasites of this
kind very much less than it used to be.
But the meat from the smaller slaughter
houses is usually not inspected and is
always a source of danger. No pork,
either fresh or smoked, should be used
without being thoroughly cooked in
order that any trichinae in it may be
killed.

Eel-worms. Belonging to the genus
A scar is are several round- worms, or
"eel-worms," some of which are very
common and of considerable economic
importance. The large-headed thread-
worm, A scar is megalocephala, which occurs in the alimentary
canal of the horse, reaches a length of from eight to sixteen
inches and may be as thick as a lead pencil. The fertilized
eggs of the parasites are passed from the body of the host
with the excreta, and probably gain entrance to a new host
through stagnant water or by a horse eating grass or leaves on
which the eggs occur.

A similar but somewhat smaller species, Ascaris lumbri-
coides, occurs in man and in sheep and hogs. In children,
particularly in tropical regions, these parasites may occur in
large numbers, sometimes from one to ten hundred in a
single individual. In such cases they may cause nervous-
ness, irritability, hysteria or even convulsions. In some cases

FIG. 26. Encapsuled
trichinae in trunk muscle
of pig. (Greatly mag-
nified; after Braun.)

TRICHINA, HOOKWORMS, FILARIA, ETC. 81

the parasites may emigrate to other parts of the host, but
ordinarily they remain in the alimentary tract.

The life history and mode of infection are similar to those of
the preceding species. The eggs may be washed from the
f eces into drinking water, or they may become dry and be blown
about as dust or become attached to fruit or vegetables.
Soon after they reach the stomach of their host they begin
their development. Strong vermifuges are necessary to re-
move them, but such medicines should be used only under
the doctor's advice.

Still another species, Ascaris canis, is a very serious pest of
dogs, especially puppies, and often causes serious losses to
breeders of these animals. It occurs also in cats, lynxes and
lions.

The stomach worm of sheep, Hcemonchus (Strongylus)
contortus, is another important intestinal parasite belonging
to the group. It is a very small thread-like species occurring
in the fourth stomach of sheep, cattle and goats. The larvae
which hatch from eggs that pass out with the feces get on the
grass blades and so into the stomach of new hosts. As the
infection is direct the disease often spreads rapidly and does
serious damage, particularly to lambs, which may die in con-
siderable numbers.

Uncinariasis, or Hookworm Disease. Perhaps no other
disease has attracted so much attention in the United States
during the past few years as the hookworm disease. It
is caused by a small round-worm from one-half to four-fifths
of an inch in length. On the anterior end, which is bent
back giving it the suggestive hook shape, is the cup-like mouth
by means of which the parasites attach themselves to the
mucous membrane of the walls of the intestine, where, in ad-
dition to sucking the blood of the victim and affecting the
mucous membrane, they produce a poison which may affect
the host in a variety of ways. The most pronounced symp-
toms are anemia and aberrations of appetite. The skin be-
comes dry, waxy white, or dirty yellow, and the patient may
eat too little or too much. In severe cases there seems to be
an uncontrollable desire for such things as chalk, rotten

6

82 ECONOMIC ZOOLOGY AND ENTOMOLOGY

wood, sand, gravel and all kinds of dirt. This has given the
popular name of "dirt eaters" to those affected with this
parasite.

The myriad eggs produced by the adult hookworms pass
out of the body of the host with the feces, and if these fall on
the ground and the temperature and moisture conditions are
suitable, as they usually are in the tropical and semi-tropical
regions where this disease is worst, the young larvae soon hatch
and grow for a few days before they become encysted. In this
latter condition they may remain for some time, even several
months, until they are in some way introduced into a new
host. There are two possible ways of infection, through the

FIG. 27. Hookworm, Necator americanus. a, Male; b, female. (Greatly

enlarged; after Wilder.)

mouth or through the skin and the circulatory system. For a
long while it was thought that infection was wholly through the
mouth, but it is now known that this is not even the usual
mode of infection. When the encysted larvae come in contact
with the skin of some person, such as the bare foot of a child,
they break from their covering and burrow their way into the
skin through some of the pores or hair follicles. They soon
find their way into the circulation and later into the lungs or
larynx and finally are swallowed and attach themselves to the
walls of the alimentary canal.

In passing through the skin they produce certain symptoms
commonly known as ground itch which often causes much
suffering. It will be seen that children are, under ordinary

TRICHINA, HOOKWORMS, FELARIA, ETC. 83

circumstances, more subject to attack than adults because
they go barefoot more, but adults are in no wise immune, and
in mining regions men may furnish the highest percentage of
infection because conditions in the mines are favorable for the
development of the parasite.

Epsom salts followed by thymol and then by epsom salts
again will remove the worms from the body of the host, but
reinfection may again take place unless sanitary measures are
adopted to control the spread of the pest. Where the modern
sewage facilities are found no hookworms occur, and the great
fight that is being made against this, the worst curse of the
poorer classes of the south, is made against the unsanitary

FIG. 28. Section through the skin of a dog two hours after it has
been infected with the Old World hookworm. (Greatly enlarged; after
Wilder.)

conditions that exist in many regions. If the soil is not
polluted with the feces that contain the eggs of the parasite
the disease will not spread.

Not only do the hookworms directly cause many deaths
each year, but they lower the vitality of the victims so that
they become an easy prey to other diseases. In addition
they retard their physical and intellectual development, seri-
ously affect the working capacity and in many other ways

84 ECONOMIC ZOOLOGY AND ENTOMOLOGY

exert a baneful influence on the general health and longevity
and on the material welfare of the people.

Porto Rico has suffered severely from this disease, as indeed
have nearly all tropical and sub-tropical countries. In the
old world the most common species of hookworm is
Uncinaria duodenalis. In the United States Necator
(Uncinaria} americanus is the most abundant. Both of these
species were formerly included in the genus Ankylostomum
and so the disease that they cause is frequently called
ankylostomiasis.

Several of our domestic animals are infected with other
species of hookworms. Uncinariasis, or "salt sick," or hook-
worm disease of cattle, is a very serious disease in some of the
southern states. This disease can be partially controlled by
intelligent methods of handling the stock. As it occurs chiefly
on low wet lands the selection of pasture lands is of first
importance, or rather it is of second importance, for the most
important thing of all is to keep the disease out altogether by
not allowing infected cattle to come on the farms or into the
locality.

A species of hookworm occurring in fur seals often causes a
loss of thousands of the young or pup seals each year on the
breeding grounds.

Filaria and Elephantiasis. Another genus of very serious
Nematode parasites is known as Filaria. The filariae cause the
various forms of disease known as filariasis. Filaria bancrofti
is the name of a minute, transparent, little worm that occurs in
human blood and lymph in many tropical and sub-tropical
regions, extending often into temperate climates. The larval
forms, that occur in the blood, are but a little more than
one one-hundredth of an inch long and about as big around
as a blood corpuscle. During the day time but few of these
are to be found in the blood near the surface of the body,
but as evening comes on they may be found there in in-
creasing numbers.

This night-swarming to the peripheral circulation has been
found to be a remarkable adaptation in the life history of the
parasite to the presence of night-flying mosquitos, for it has
been demonstrated that in order to go on with their develop-

TRICHINA, HOOKWORMS, FILARIA, ETC. 85

ment these larval forms must be taken into the alimentary
canal of a mosquito. There they undergo certain changes,
and then make their way through the walls of the stomach
into the muscles, where they increase in size until they are
about one-sixteenth of an inch in length. Later they migrate
to other parts of the body, some of them to the proboscis of
the mosquito from w r hich they issue when the mosquito is
feeding and thus gain entrance into another host. It is not
known that these parasites can gain an entrance into the
circulatory system in any other way,
but it has been suggested that mosqui-
tos dying in the water may liberate
some of the filariae which may later
find their way into the vertebrate host
when the water is used for drinking.

Soon after entering the circulatory
system of the human host the parasites
make their way into the lymphatics
where they attain sexual maturity,

and in due time new generations of F IG. 29. Microfilaria
,v i i i r-i of the blood; immature

the larval filariae, or microfilanae, are stage of Fila ' ria bancroflL

poured into the lymph, and finally (Greatly enlarged; after

into the definite blood-vessels, ready Terzi -)

to be sucked up by the next mosquito that feeds on the

patient.

In most cases of infection the presence of these filariae in the
blood seems to cause no inconvenience to the host. They
are probably never injurious in the larval stage, that is, in the
stage in which they are found in the peripheral circulation.

In many cases, however, the presence of the sexual forms in
the lymphatics may cause serious complications. The most
common of these is that hideous and loathsome disease known
as elephantiasis, in which certain parts of the patient become
greatly swollen and distorted. An arm or a leg may become
swollen to several times its natural size, or other parts of the
body may be seriously affected. This disease occurs most
commonly in tropic and sub-tropic regions. Nearly one-third
of the natives of the Samoan Islands suffer from elephantiasis.

86 ECONOMIC ZOOLOGY AND ENTOMOLOGY

The guinea-worm, Filaria mcdinensis, referred to on an
earlier page, is a member of this group. It has been known for
many ages, and is thought to be the "fiery serpent" mentioned
by Moses. It lives in the connective tissues, where it attains
a length of two or three feet. Its diameter is about one and
one-half millimeters. When it is ready to produce young it
usually descends to the feet or the lower part of the legs of the
host or the part most likely to come in contact with the water.
Here it burrows out to the surface, often producing serious
sores. The intermediate stage is passed in the body of
Cyclops, a small fresh-water crustacean.

There are several other species of Filaria that are parasitic
in man but they are of less importance. Filaria loa is an inter-
esting species that lives in the connective tissue just under
the skin and travels about from one part of the body to
another, occurring most commonly about the eyes, where
their presence may cause irritation and congestion.

Classification of Nemathelminthes. This branch may be
divided into three classes, the Nematoda, Nematomorpha and
Acanthocephala. The class Chatognatha (Gr. chaite, hair;
gnathos, cheek) or arrow-worms, is usually included in this
branch but the relationship of the group is very uncertain.

The Nematoda (Gr. nema, thread; eidos, likeness) are by
far the most important and include all of the forms that have
just been described, with the exception of the hair-snakes which
belong to the second class.

The Nematomorpha (Gr. nema, a thread; morphe, form)
include the hair-snakes, the larvae of which, as we have already
noted, are parasitic in insects. One common species, Mermis
albicans, frequently occurs abundantly enough in grass-
hoppers to be of some importance in their control. It is
probably this species, too, that at times causes so much alarm
in some regions when the "cabbage snakes" appear in great
numbers. When these round-worms occur on cabbages or
other vegetables it means that the insect that acted as their
host was probably resting or feeding on the plant when the
parasite left it. As soon as they can they pass into the ground

TRICHINA, HOOKWORMS, FILARIA, ETC. 87

and do not injure the vegetables. No harm will come from
eating vegetables that have been visited by these parasites.

The Acanthocephala (Gr. akantha, thorn; kephale, head), or
thorn-headed worms, include a number of parasitic forms
which show extreme specialization in their mode of life. The
anterior end is developed into a conspicuous spiny organ for
holding on to the walls of the alimentary canal of the hosts in
which they live. There is no mouth or digestive organs but
the parasite takes its nourishment through
the body-wall from the food surrounding it.

Echinorhynchus gigas, infesting hogs, is
the best known species of this class. In
America the larvae of the June beetle, Lach-
nosterna, which is the common white grub
found in the sod in pasture lands and else-
where, serves as the intermediate host for
the parasite. Hogs should not be allowed
to pasture on lands where the grubs have be-
come infected from previously infested hogs.
Once pasture land has become infected it

should be left for three years to insure the FIG. 30. A

maturing of all the grubs that are infected. wheel animalcule,

Several other species belonging to this ^Z^ffij^
class are parasites of fishes. living specimen.)

ANIMALS OF UNCERTAIN RELATIONSHIP

There are two groups of aquatic animals the exact relation-
ships of which are by no means agreed upon by systematic
zoologists. They are usually supposed to be more nearly
related to the worms than to any other group, and as they are
not of enough economic importance to be given a separate
chapter they may be mentioned here.

The Wheel Animalcules, or Rotifers, branch Trochel-
minthes (Gr. trochos, wheel; helmins, worm). These are
minute aquatic animals which on account of their size were for
a long time classed with the Protozoa. But they are really
very complex in structure. The anterior end is provided with

88 ECONOMIC ZOOLOGY AND ENTOMOLOGY

a circlet of vibrating cilia, which has suggested the common
name. These little animals are interesting on account of their
remarkable power to withstand drying. When the water in
which they are found evaporates, some of them do not die but,
as minute shrivelled dust-like particles, may lie for months
or even years and be revived again when water reaches them.
The Sea-mats and the Lamp -shells, Branch Molluscoida
(Mollusca, mollusc; Gr. eidos, likeness). The sea-mats, or
Polyzoa, are common on rocks along the seashore and sometimes
in fresh water also. Most of them either spread mat-like
over the surface of the objects on which they are growing, or
form branched tree-like or moss-like colonies and look much
more like plants than animals. Only their development
suggests any relation to the worms. The lamp-shells, or
Brachiopoda, are all marine. They look so much like little
clams that for a long time they were classed with the molluscs.
Their chief interest lies in the fact that they represent a group
of animals that were once very numerous but which have not
been able to adapt themselves to the changed conditions that
are found on the earth to-day. In ages past they seem to have
occurred in great numbers, as more than a thousand species
have been preserved as fossils in the rocks. To-day only
about one hundred species are known, and some of these are
very rare.

CHAPTER XIII
STARFISHES, SEA-URCHINS AND SEA-CUCUMBERS

The starfishes, sea-urchins, sand-dollars and sea-cucumbers,
branch Echinodermata (Gr. echmos, hedgehog; derma, skin),
compose the only branch of animals all of whose members
are exclusively marine. Although they are among the most
common inhabitants of all sea beaches no species has adapted
itself to life in fresh water. Why this is so no one is yet able
to explain. Most of them can move about freely but some of
the feather stars are attached to rocks or other objects as the
polyps are.

The Starfish. The common five-rayed starfish well illus-
trates the general plan of structure of members of this group.
The five rays arranged around the central disk illustrate the
radial symmetry which is characteristic of the branch. The
entire aboral or upper surface, as well as a greater part of
the oral or lower side, is thickly studded with the calcareous
plates, or ossicles, of the body-wall. These ossicles support
many short, stout spines arranged in irregular rows, and
numerous pincer-like processes, the pedicellaria. In the inter-
spaces between the calcareous plates are soft fringe-like pro-
jections of the inner body-lining, the respiratory c<zca. A little
to one side of the center of the disk is the small striated cal-
careous madreporic plate, and a little nearer the center is the
anal opening. At the tip of each arm or ray is a cluster of
small calcareous ossicles and within each cluster a small speck
of red pigment, the eye-spot or ocellus.

On the oral (under) surface are the centrally-located mouth,
and the ambulacral grooves running longitudinally along each
ray. In each groove are two double rows of soft tubular
bodies with sucker-like tips. These are called the tube-feet,
and are organs of locomotion.

89

go ECONOMIC ZOOLOGY AND ENTOMOLOGY

By removing all of the dorsal body-wall except the part
surrounding the madreporic plate and the anus, the internal

eye spot

muscles o,

cardiac stomach
intestinal caecum

'muscles of the pylorit caeca

FIG. 31. Dissection of a starfish, Asterias sp. male.

organs are exposed. The large alimentary canal is divided
into several regions. The short esophagus leads from the

STARFISHES, SEA-URCHINS, ETC. 91

mouth directly into a large membranous pouch, the cardiac
portion of the stomach. By a short constriction the cardiac
portion is separated from the part which lies just above, i. e.,
the pyloric portion of the stomach. From the pyloric portion
large, pointed, paired glandular appendages, the pyloric caeca,
extend into each ray. Their function is digestive, and some-
times they are spoken of as the digestive glands or "livers."
The pyloric cceca, as well as the cardiac portion of the stomach,
are held in place by paired muscles which extend into each
arm. The pyloric portion of the stomach opens above into
a short intestine which terminates in the anus. Attached
to the intestine is a convoluted many-branched tube, the
intestinal c&cum.

In the angle of each two adjoining rays are paired glandular
reproductive organs, which empty by a common duct on the
aboral surface. The small bulb-like bladders extending in two
double rows on the floor of each ray are the water-sacs, or am-
pulla, and each one is connected directly with one of the tube-
feet.

Passing around the alimentary canal near the mouth is a
ring-shaped canal from which the radial vessels run out be-
neath the floor of each ray and from which a hard tube extends
to the madreporic plate. This hard tube is the stone canal, so
called because its walls contain a series of calcareous rings,
while the circular tube is the ring canal or circum-oral water-
ring, from which radiate the radial canals. In some species of
starfish there are bladder-like reservoirs, Polian vesicles, which
extend interradially from the ring canal.

The ampullae and tube-feet are all connected with the radial
canals. By the contraction of the delicate muscles in the
walls of the ampullag the fluid in the cavity is compressed,
thereby forcing the tube-feet out. By the contraction of
muscles in the tube-feet they are again shortened, while the
small disk-like terminal sucker clings to some firm object.
In this way the animal pulls itself along by successive "steps."
This entire system, called the water-vascular system, is char-
acteristic of the branch Echinodermata. In addition to the
fluid in the water-vascular system there is yet another body-

92 ECONOMIC ZOOLOGY AND ENTOMOLOGY

fluid, the perivisceral fluid, which bathes all of the tissues and
fills the body-cavity.

The perivisceral fluid is aerated through the respiratory caeca
which, as we have seen, are outpocketings of the thin body-
wall which extend outward between the calcareous plates of
the body. Surrounding the stone canal is a thin membranous
tube, and within and by the side of the stone canal is a soft
tubular sac. The functions of these organs are not certainly
known.

calcareous spine

respiratory caeca

ossicles

ampulla

'tube fool

epithelium of (he body

cavity y$

""^r L?ft

mesentery
pyloric caecumr

ambulacral ossicle-
ectodermal covering

pedicellaria ^H/w ,/

.radial' canal
radial blood-vessel

FIG. 32. Semi-diagrammatic figure of cross-section of the ray of a

starfish, Astcrias sp.

The nervous system consists of a nerve-ring about the mouth,
and nerves running from this ring beneath the radial canals
along each arm.

The starfish feed upon other marine animals, especially on
molluscs. They are often very destructive on oyster beds,
where they may occur in such numbers as wholly to deplete
the beds unless they are removed by means of rakes or tangles
of ropes that are dragged over the beds for this purpose.

When the starfish wishes to feed on a mollusc that is too

STARFISHES, SEA-URCHINS, ETC. 93

large to be taken into its mouth the stomach is extended
through the mouth and the living prey is covered over by it.
As soon as the shell is opened ever so little the soft parts of
the victim are sucked up and digested by the starfish. Having
finished its meal the starfish draws its stomach in and seeks
another oyster or clam.

FIG. 33. Regeneration of starfishes, Linckia sp. Upper figure shows
a starfish regenerating arms that have been lost; the lower figure shows a
portion of an arm regenerating the disk and other arms. (About natural
size.)

Starfish, and in fact most of the Echinoderms, have the
power of regenerating lost parts. If, through accident, a
starfish loses one or more of its rays new ones will grow out
to replace the old ones, or, in some cases, the arm may prac-

94 ECONOMIC ZOOLOGY AND ENTOMOLOGY

tically regenerate all the rest of the body. Specimens showing
this process are sometimes found on the beaches. Fig.
33 shows such specimens found on the reefs in Samoa.

During its development from the egg to the adult the
starfish passes through a remarkable metamorphosis. The
young when it issues from the egg is more or less ellipsoidal, and
is active and free-swimming, being provided with numerous
cilia. This larva soon changes to another curious form with

FIG. 34. A sea-urchin, Strongylocentrotus franciscaniis, showing movable

spines. (Reduced.)

many prominent projections. This is so unlike a starfish
that the earlier naturalists did not realize that the larvae were
in any way related to the starfish and gave them the name
Bipinnaria, thinking they were fully developed adult animals.
The name is still used in referring to starfish larvae, but we now
know that the bipinnaria become, by later development,
adult starfish.

Other Echinoderms. All the various starfish belong to the
class Aster oidea (Gr. aster, star; eidos, likeness) and although
they may differ much in general appearance they are all readily

STARFISHES, SEA-URCHINS, ETC.

95

recognized. Some starfish may have thirty or more rays
instead of five as in the typical forms. Others may have the
interradial spaces filled out nearly or quite to the tips of the
rays, making the animal simply a pentagonal disk. Some
are very small, less than an inch in diameter, while others
attain an extent of three feet or more.

The brittle-stars belong to the class Ophiuroidea (Gr. ophis,
snake; our a, tail; eidos, likeness). They differ from the

FIG. 35. A holothurian or sea-cucumber, Cncumar'm frondosa. (About

| natural size.)

Aster oidea in that the body-cavity does not extend out into
the arms as it does in the starfish, or extends at most only into
the bases of the arms. The five radiating rays are usually
slender, more or less cylindrical, and sometimes branched.

The sea-urchins, class Echinoldea (Gr. echinos, hedgehog;
eidos, likeness), look quite unlike the starfish. The body is

9 6 ECONOMIC ZOOLOGY AND ENTOMOLOGY

globular, usually more or less flattened at the poles. It
is covered with many movable spines which may be small
and light or long and heavy. When the spines are removed
the calcareous plates that constitute the firm part of the body-
wall are plainly distinguished. Sea-urchins are found mostly
in tide pools near the shore, but some occur at great depths.

FIG. 36. A sea-lily, Pentacriims sp. (About 5 natural size.)

The sand-dollars or cake-urchins belong to the same class.
Their bodies are very much flattened and often brightly
colored. They are common in the sand on both the Atlantic
and Pacific coasts.

The sea-cucumbers, class Holothuroidea (Gr. holos, whole;
thouros, rushing; eidos, likeness), look even less like starfish.

STARFISHES, SEA-URCHINS, ETC. 97

The body is more or less cylindrical and looks not unlike a
cucumber, perhaps still more like a sausage. The body-wall
is tough and leathery and the five rows of tubular feet are
usually, but not always, present. At one end is a ring of
branched tentacles surrounding the mouth. These are often
flower-like or leaf-like and brightly colored. In the Orient
sea-cucumbers are largely used as food, the gathering and
preparing of this trepang, as it is called, forming a very con-
siderable industry.

Many of the feather-stars or sea-lilies, class Crinoidea (Gr.
krinon, lily; eidos, likeness), are fixed to rocks or the sea bottom
by a longer or shorter stalk which is composed of a number of
segments. Others are attached by a stalk during their larval
stage, but after a time the stalk is absorbed and the feather star
becomes free. The central disk is provided with a number of
radiating arms which are long and slender, sometimes re-
peatedly branched. The fine lateral pinnulce on these arms
give them a feather-like appearance. They occur mostly
in deep water. There are comparatively few species of crinoids
that still exist, but in former geologic times thousands of
species flourished. The fossilized parts of their bodies,
especially the little disk-like segments of the stem, are very
common in Paleozoic rocks.

CHAPTER XIV

EARTHWORMS, LEECHES AND OTHER SEGMENTED

WORMS

The segmented worms (branch Annelida, annellus, little
ring), of which the earthworm is the most common example,
show a decided advance in structure over the flat-worms and
round-worms. Their bodies are divided into a series of seg-
ments, and most of them have well developed nervous and
circulatory systems. There is a definite body-cavity, and
paired organs of excretion called nephridia.

The segmented worms are grouped in four classes, the
Chatopoda (Gr. chaite, hair; pous, foot) including the earth-
worms and many marine worms; the Hirudinea (L. hirudo,
leech) or leeches; and the marine Archiannelida (Gr. arc hi-,
primitive; annellus, little ring) and Gephyrea (Gr. gephyrd,
bridge).

The Earthworm. In the Chatopoda the sides of the body
are furnished with minute setae, or with special locomotor
protrusions known as parapodia. The familiar earth-worm, or
angle-worm, or fish- worm, as it is often called, will serve as an
example of the group. Earth-worms eat their way through the
ground forming definite burrows and bringing to the surface
soil from considerable depths. The earth that is swallowed as
they are digging contains more or less decaying vegetable matter
which is used as food. Darwin was the first to call attention to
the great good that the earthworms do by opening up the
soil so water can enter, enabling plant roots to penetrate
deeper, and by bringing to the surface soil from which the
various plant foods have not yet been taken by the plants.
He estimated that in England and conditions are prac-
tically the same in America about ten tons of soil per
acre pass annually through the bodies of these worms, and

98

EARTHWORMS, LEECHES, ETC. 99

that they cover the surface with earth at the rate of about an
inch in five or six years. Besides being an important factor in
increasing the fertility of the soil the earthworms furnish a
considerable part of the food supply of many birds. Nor
should we fail to mention the important part that they play
in the welfare of mankind, or rather "boykind," when, dan-
gling from a hook, they tempt the hungry fish from its haunts
in the shade of the rocks or among the gnarled roots of the old
tree. Usually they remain in the ground during the day,
wandering about only at night, but sometimes, particularly
after heavy rains, they may be found in considerable numbers
crawling over the ground in the early morning. As they are
often found on hard pavements where they have crawled or
been washed by the water many persons think that they have
''rained down."

External Structure. The body of the earthworm is long,
cylindrical, bluntly pointed at the anterior end and rounded
and flattened at the posterior end. The four double rows of
stiff bristles or setae are hardly visible to the naked eye but
they may be detected by drawing the worm backward across
the hand. Over the mouth is a small lobe called the prosto-
mium, and a short distance behind it is a broad thickened ring
or girdle, the clUellum. This is a glandular structure which
secretes the cases in which the eggs are laid.

Internal Structure. If a careful incision is made along the
dorsal line extending from behind the clitelleum to the anterior
end of the body the sides of the body-wall may be fastened
aside so as to expose the internal organs. The body-wall is
made up of a thin transparent covering, the cuticle, just be-
neath which is a less transparent layer, the epidermis, and two
layers of muscles, an outer circular layer and an inner longi-
tudinal layer. The space between the body-wall and the
alimentary canal is the body-cavity, or coelom. It is divided
into sections or segments by thin membranes, the septa. The
body of the earthworm may be compared to two tubes, a
larger outer one represented by the body-wall and a smaller
inner one, the alimentary canal, extending from one end
to the other. The space between these is the body-cavity.

zoo ECONOMIC ZOOLOGY AND ENTOMOLOGY

cerebral ganglion

retractor and protractor
muscles of the pharynx^

(esophageal pouches--
seminal receptacles~

seminal

pharynx
{esophagus

nephridium T^.

gizzard f-- .^

FIG. 37. Dissection of the earthworm, Lumbricus sp.

EARTHWORMS, LEECHES, ETC. 101

This is an arrangement that we find common in all the higher
animals.

In the alimentary canal a number of distinct parts may be
recognized. Anteriorly is the muscular pharynx, which is
followed by a narrow esophagus leading directly into the
thin-walled crop; next comes the muscular gizzard, and next
the intestine, which opens externally in the terminal segment
through the anus. The anterior end of the alimentary canal
is more or less protrusible, while the posterior portion is held
more firmly in place by the septa, which act as mesenteries.
Surrounding the narrow esophagus are the reproductive organs,
three pairs of large white bodies and two pairs of smaller sacs.
Under the reproductive organs are three pairs of bag-like
structures projecting from the esophagus. The front pair
are the esophageal pouches; the next two pairs are the esopha-
geal, or calcijerous, glands. They communicate with the
alimentary canal, and secrete a milky calcareous fluid.

By cutting transversely through the alimentary canal in the
region of the clitellum, a dorsal fold of the intestine, the
typhlosole, may be seen extending into the lumen. This fold
gives a greater surface for digestion, and in it are a great
many hepatic or special digestive cells. The entire alimentary
canal is lined internally with epithelium.

The dorsal blood-vessel lies along the dorsal surface of the
alimentary canal. From the anterior portion there arise
several circumesophageal rings, or "hearts." These hearts
are contractile, and serve to keep the blood in motion through
the blood-vessels. Just beneath the alimentary canal is the
ventral blood-vessel, and still beneath this the ventral nerve-cord.
The slight swellings on the nerve-cord in each segment of the
body are the ganglia. The brain, or cerebral ganglion, lies in
the first segment of the body above the esophagus, and is con-
nected with the ventral nerve chain by the circumesophageal
collar.

The excretory system is peculiar, consisting of a series of small
convoluted tubes, the inner ends of which are furnished with
small ciliated funnels which gather and carry off the waste
matter from the fluid that fills the body-cavity. There are

102 ECONOMIC ZOOLOGY AND ENTOMOLOGY

no special organs of respiration, but the thin walls of the skin
are traversed by a network of minute blood-vessels which
are separated from the air by only a very thin membrane
through which the oxygen passes readily and the carbon
dioxide is given off.

nepkridium don&l blodd vessel

\ hepatic cells /'

,' longitudinal muscle

/i ^circular muscle fibres
r epidermis
.cuticle

typhlosole

setae

; .' i nerve cord

nephridipore , nephrostome

ventral vessel
t
I

body cavity

FIG. 38. Cross-section of earthworm.

The earthworm is hermaphroditic, that is, both spermatozoa
and ova are produced in the same individual. The testes are
two pairs of flattened glands lying in the region of the tenth and
eleventh segments. These are connected with the seminal
vesicles and communicate with the exterior through the long
vasa deferentia which open in the fifteenth segment. The ovaries
are attached to the septa separating the twelfth and thirteenth
segments. The ova reach the exterior through a pair of funnel-
shaped oviducts, the mouths of which are near the ovaries.

EARTHWORMS, LEECHES, ETC.

103

They pass through the septum between the thirteenth and
fourteenth segments and open through the ventral wall of the
fourteenth segment. The sperm cells do not fertilize the ova
from the same individual. When the reproductive elements
are ripe, two worms mate and there is a transference of
spermatozoa from each individual to the other. The clitellum
then becomes very much swollen, and finally forms a collar-
like structure about the body of the worm. As this slips
forward the ova are discharged into it, and a little further
forward the sperm cells that have been received during
copulation are also emptied into it. As it passes on over the

FIG. 39. A group of marine worms. At the left a gephyrean, Dendro-
stomum cronjhclmi, the upper right-hand one a nereid, Nereis sp.,_the lower
right-hand one, Polynos bremsetosa. (From living specimens in a tide-
pool in the Bay of Monterey, California.)

head both ends of the collar become sealed and thus a capsule
containing the ova and spermatozoa is formed. This capsule
lies in the ground until the young are hatched. Only a part
of the eggs in each capsule develop, the rest being used for food
by the growing young.

The Marine Worms. To the genus Nereis belong many of
the large marine worms that are found on almost all sea
beaches. The head is provided with two pairs of eyes and
with several tentacles which act as feelers. The sides of the

io 4 ECONOMIC ZOOLOGY AND ENTOMOLOGY

body are provided with lateral plates, a pair to each segment.
These plates are divided into lobes, and aid the animal in
crawling or swimming, and as some of them are well pro-
vided with blood-vessels they also serve as respiratory organs.
Many of the marine worms swim in the sea, others are
more or less closely confined to their burrows, while some
form tubes of sand or gravel or secrete tubes of lime which
furnish excellent protection. Such tube-like houses are often
found on rocks and shells. They may usually be found on
the oyster shells in almost any market. The part of the
body that is protected has no further use
for the lateral appendages and so they have
almost or quite disappeared. On the head,
however, there have been developed great
plume-like appendages which are well sup-
plied with blood-vessels and act as gills.
These organs are often beautifully colored,
and when fully expanded look like gorgeous
flowers. Indeed, these worms and the sea-
anemones make veritable flower gardens in
many a tide pool along rocky shores.

The Leeches. In their general appear-
ance the leeches look much more like the flat-
worms (Platyhelminthes), than like the other
Annelida. The body is flattened, and com-
40 The posed of many segments. Most of the seg-
ments are marked by transverse lines, making
the animal appear to have many more seg-
ments than it really has. The ventral side is
provided with two sucking disks. The mouth,
which lies in the anterior disk, is provided
with sharp jaws which enable the leech to puncture the skin
of animals in order that it may suck their blood. Leeches
live mostly in the water, and are found most commonly on
such animals as fish, frogs and others that are aquatic or
semi-aquatic. They will readily attack man when the oppor-
tunity offers, and in olden days they were much used by physi-
cians to "bleed" their patients. A leech was allowed to at-

FIG.

medicinal leech,
Ilirudo medicina-
lis. (Grows to be
six or eight inches
long.)

EARTHWORMS, LEECHES, ETC. 105

tach itself to the body of a patient and feed until it was com-
pletely gorged. Leech farms where these "medicinal leeches"
were raised were formerly common in some countries, and a jar
of live leeches was a part of the regular stock of the apothecary.
They are now seldom used.

CHAPTER XV
CRAYFISH, LOBSTERS, CRABS, SHRIMPS, ETC.

The great branch Arthropoda (Gr. arthron, joint; pous,
foot) comprises, as shown by the table of classification on pages
55 to 57, five classes; the Crustacea (L. crusta, crust), or
crayfishes, crabs, lobsters, barnacles, etc.; the Onychophora
(Gr. onyx, claw; phero, bear) or slime slugs; the Myriapoda
(Gr. myrios, numberless; pous, foot) or centipedes and thous-
and-legged worms; the Arachnida (Gr. arachne, spider) or
scorpions, spiders, mites and ticks; and the Insecta
(L. insectum, cut into), which in point of number of species,
is by far the largest class in the whole animal kingdom.

The Arthropods get their name from two Greek words mean-
ing jointed foot, and the members of the branch are charac-
terized by the possession of legs and other laterally arranged
paired appendages each composed of several successive jointed
parts. The bodies of all Arthropods are bilaterally symmet-
rical, and are composed, as are those of the Annelida, or an-
nulate worms, of a series of successive segments. They are
inclosed by a more or less firm outer cuticle, which not only
serves as a protection to the soft body parts within but also
provides firm points of attachment for the muscles. This
hardened cuticle is called the exoskeleton.

The internal organs of the Arthropods show a more or less
obvious segmentation corresponding with the segmentation
of the body wall. The alimentary canal runs longitudinally
through the center of the body from mouth to anal opening-
The nervous system consists of a brain lying above the esoph-
agus and a double nerve-chain running backward from the
esophagus, along the median line of the ventral wall, to the pos-
terior extremity of the body. This ventral nerve-chain con-
sists of a pair of longitudinal cords and a series of pairs of

106

CRAYFISH, LOBSTERS, CRABS, SHRIMPS, ETC. 107

ganglia, arranged segmentally. The two ganglia of each pair
are fused more or less nearly completely to form a single gang-
lion, and the nerve-cords are partially fused, or at least lie
close together. In addition there is a smaller sympathetic
system composed of a few small ganglia and certain nerves
running from them to the viscera, this system being connected
with the main or central nervous system. In this group the
organs of special sense reach for the first time a high stage
of development. Compound eyes are peculiar to Arthropoda.
The heart lies above the alimentary canal. Respiration is
carried on by gills, in the aquatic forms, and by a remarkable
system of air-tubes or tracheae in the land forms (insects).
The sexes are usually distinct, and reproduction is almost uni-
versally sexual. Most of the species lay eggs.

CRUSTACEANS

The members of the large and important class Crustacea
are mostly aquatic, but a few species are found on land in
moist places. There are over ten thousand known species
in the class, about nine-tenths of which are marine.

Many are scavengers, feeding on any dead organic matter,
and thus doing a great service in helping to keep the shores,
small pools, and even the sea clean. Some prefer a vegetarian
diet and may do much damage to wood that is in the water
or even to crops on the land. The lobsters, crayfishes, crabs,
shrimps and prawns furnish man with an abundant supply of
most dainty food, and more important still, they furnish an
almost inexhaustible supply of food to many other aquatic
animals.

The name Crustacea refers to the covering or crust (exo-
skeleton) that protects the softer parts of the body and serves
for the attachment of the muscles. This crust may be very
hard, as with the crabs, or soft and delicate, as with some of the
smaller forms.

The Crayfish. The crayfish will serve as a typical example
of the class, but the group contains many remarkable and
important deviations from the type. The body is divided
into two well defined regions, the cephalothorax and the ab-

io8 ECONOMIC ZOOLOGY AND ENTOMOLOGY

domen. The cephalothorax is covered above and on the sides
by the firm carapace, which is divided by the transverse cervical
suture into parts corresponding to the head and thorax. The
compound eyes are situated at the ends of two short stalks which
arise just beneath the rostrum, the anterior horn-like projec-
tion of the carapace. The segments of which the cephalo-
thorax is composed are so fused together that they are not
readily distinguished, but each segment of the body bears a
pair of appendages and by the position and character of these
appendages the different regions can be determined. Each
of these appendages, except the antennae, consists of a basal
part from which arises two branches made up of one or more
segments modified to perform certain functions.

Just below the eyes is the first pair of appendages, the
antennules, in the base of each of which is an organ formerly
supposed to be an auditory organ but now known to be an
organ of equilibration. These aid the animal in keeping the
body in a proper position while swimming. Next come the
antenna, or feelers, which, like the antennules, are provided
with fine hairs which aid in the sense of touch and perhaps of
smell. The green gland lies at the base of the antennae. It is
probably an excretory organ with functions similar to the
kidneys of higher animals.

Next comes the group of appendages surrounding the mouth,
the mandibles, two pairs of maxilla and three pairs of maxilli-
peds. The mandibles are hard and jaw-like. The second
maxillae have a large paddle-like structure, the scaphognathite,
which extends back over the gills in the branchial chamber,
the space between the lower part of the carapace and the body-
wall. The movements of this appendage keep the currents of
water flowing through the gill chamber. The maxillipeds are
appendages of the thorax. The first pair of legs is much
larger than the others, the terminal segments being developed
into strong pincers or chela. Each pair of legs, except the
last, bears gills which extend up into the branchial chamber.
In the basal segments of the last pair of legs of the male are the
genital pores. In the female the genital pores are in the
basal segments of the second pair of walking-legs. In the

CRAYFISH, LOBSTERS, CRABS, SHRIMPS, ETC. 109

antennule

opening of green gland

maxillipeds

thorax

genital aperture

.-'an us

---'uropod

-telson

FIG. 41. Ventral aspect of female crayfish, Cambanis sp., with the
appendages of one side removed.

no ECONOMIC ZOOLOGY AND ENTOMOLOGY

male each segment of the abdomen, except the last, bears a
pair of appendages or swimmerets. The first two pairs are
modified to serve as channels for the sperm fluid. The last
pair of appendages is broad and flat and with the last segment,
the telson, forms the broad tail, or swimming fin. In the
female the first two pairs of abdominal appendages are very
small or altogether lacking.

The food, which for the most part consists of vegetable
matter, or dead organic matter, passes into the stomach
through a short esophagus. The stomach is divided into two
parts. The anterior portion, the cardiac chamber, contains
three strong teeth, the gastric mill. These grind the food
before it passes back through a fine strainer of stiff hairs into
the second or pyloric chamber, which receives the secretions
from the large digestive glands that surround the stomach.
The intestine is a straight tube opening to the outside by a
slit-like anal opening on the under side of the telson.

The heart lies in the pericardial sinus in the posterior
portion of the cephalothorax. The contractions of the heart
force the blood out into seven arteries which carry it to all
parts of the body. The ophthalmic artery supplies the eyes
and other parts of the head. The two antennary arteries
supply the antennae, excretory organs and other tissues. The
two hepatic arteries supply the digestive glands. The dorsal
abdominal artery supplies the intestine and surrounding
tissues. The sternal artery passes down to the ventral wall
where it divides, one part carrying blood to the appendages in
the thorax and the other part to the appendages of the abdo-
men. All of the arteries give off many branches which divide
again and again into very small capillaries which open into
spaces between the tissues. From all of the tissues the blood
finally makes its way to a large space, the sternal sinus, in the
ventral part of the thorax. From the sinus it passes out into
channels in the gills w r here it gives off its carbon dioxide and
receives oxygen from the water which bathes the gills. Then
through other channels, the branchio-cardiac sinuses, it
reaches the pericardial sinus which surrounds the heart.
From here it enters the heart through three pairs of openings,

CRAYFISH, LOBSTERS, CRABS, SHRIMPS, ETC. in

ii2 ECONOMIC ZOOLOGY AND ENTOMOLOGY

the ostia, which are guarded by valves that allow the blood to
enter but prevent it from flowing back into the sinus.

The nervous system is similar to that of the earthworm and
the insects. It consists of a dorsal ganglionic mass, the brain,
which is connected by cords passing around the esophagus
with the ventral nerve cord which lies along the floor of the
thorax and abdomen. Along the ventral nerve cord are a
number of ganglia which give off nerve fibers that reach the
various parts of the body.

The abdomen is quite filled with the powerful muscles that
flex that part of the body forward when the crayfish is swim-
ming, thus producing backward locomotion. These muscles,
as well as the strong muscles of the appendages, are all at-
tached to the firm body-wall, or exoskeleton, not to an
internal skeleton as in the vertebrates.

The sexes are separated. The spermatozoa are produced in
the male in the tri-lobed testis which lies under the heart and
over the anterior end of the intestine. They pass through the
long, coiled, paired vasa deferentia to the genital apertures in the
base of the last pair of thoracic legs. The eggs arise in the
bilobed ovary in the female and pass through the paired ovi-
ducts and out through the genital apertures on the next to the
last pair of thoracic legs. The eggs are glued to the swimmerets
of the female, and remain in this position until they hatch.

During the very early part of their development the young
or larval crayfish cling to the old egg shells or to the spinnerets
of their mother thus receiving much needed protection, for
their bodies are very soft. After about two days the young
make their first moult, casting off the old skin after a new one
has been formed underneath it. They usually moult about
seven times during the first summer and grow very rapidly
after each moult. In the process of moulting the lining of the
esophagus, stomach and the alimentary canal is also cast off.
Often one or more of the appendages may be lost during
moulting. Such lost parts are usually regenerated and it is
not uncommon to find individuals with one of the claws or
legs shorter than the others, the short appendage being a new
one that is replacing one that has been lost.

CRAYFISH, LOBSTERS, CRABS, SHRIMPS, ETC. 113

Crayfish, or crawfish, as they are more commonly called,
are found in most fresh water ponds and streams. The
common species in the eastern United States belong to the
genus Cambarus, those on the Pacific Coast to the genus Astacus.
Some species live in holes in the ground, digging deep enough
to reach water, or at least considerable moisture. The earth
that is removed in digging the burrows is sometimes built up
to form short chimneys above the ground. This burrowing
habit is often the cause of serious damage to the levees along
the rivers, particularly along the Mississippi River. In the
southern United States crayfish often occur in such
numbers that they become important pests in the corn and
cotton fields. In badly infested areas there may be as many
as 10,000 or 12,000 holes to the acre. From these holes the
crayfish issue in the evenings or on rainy mornings and feed
on the young tender plants. They may be easily killed by
placing a little carbon bisulphid in each hole.

In some sections of the country crayfish are used for food
and are considered a great delicacy, those on the west coast, on
account of their size, being particularly in demand. Recent
attempts have been made to introduce these larger species
into waters where only the smaller ones occur naturally.
In Europe the crayfish have been used for food for centuries
and in France "crayfish farming" has been successfully
practiced for many years.

CLASSIFICATION

The class Crustacea is divided into two sub-classes, the
Entomostraca and the Malacostraca.

Sub-class Entomostraca. Entomostraca are mostly small,
comparatively simple forms with little differentiation of the
appendages. Four orders are included in this class. The
order Phyllopoda comprises mostly fresh water species with
leaf-like appendages. The "fairy shrimps, " common in fresh
water pools in the early spring, are among the largest examples.
The species of A rtemia, an abundant Phyllopodin salt and brack-
ish or fresh water, are of great interest to biologists on account

8

ii 4 ECONOMIC ZOOLOGY AND ENTOMOLOGY

of the changes that may take place in them when the density of
the water is changed. Artemia and several other genera be-
longing to this order form a very important food supply for
many fishes.

To the order Ostracoda belong several genera; Cypris, which
occurs in fresh water, and Cypridina, which is marine, are the
most common. These resemble minute bivalve shells and
often occur in great numbers near the surface where the
surface-haunting fish and other animals feed on them.

In the order Copepoda the body is
long and distinctly segmented, and the
appendages are confined to the head
and thorax. The water-fleas, Cyclops,
are common in all pools or quiet waters.
The single median eye has suggested
the generic name. These are often used
as examples to show how rapidly some
of these forms may multiply. It has
been estimated that the descendants
of a single individual might in one
year number nearly 4,500,000,000, if all
the young lived and produced their full
number of offspring. They feed on
other smaller animals such as Protozoa
and Rotifera, and in turn serve as one
of the most important sources of food
for the young of many fresh water fishes. Related to Cyclops
is the genus Cetockilus which occurs in the surface water of
the sea in inconceivable numbers, sometimes forming almost a
solid mass extending for miles in quiet waters. Those whales
which are furnished with fringes of whalebone in the mouth
often swim in schools through the water where these minute
creatures abound, and as the water rushes through the wide-
open mouth the minute crustaceans are strained out and
thus furnish a dainty and abundant supply of food for the
largest of living animals. To the genus Sapphirina belong
some of the most wonderfully phosphorescent animals that
are found in the sea. This order also includes the so-called

FIG. 43. Water-flea,
Cyclops, female with
egg masses. (From life,
greatly magnified.)

CRAYFISH, LOBSTERS, CRABS, SHRIMPS, ETC. 115

fish-lice which are especially interesting because of their
parasitic habits and the greatly modified structure resulting
therefrom. Some live as commensals, that is, are associated
with their hosts in such a way as to derive benefit from them,
without injuring them. Others are truly parasitic and live
upon the blood or tissues of their host. The most common of
these attach themselves to the gills of fishes, but they may also
be found as external or internal parasites, of whales, molluscs,
marine worms, starfishes and many other animals that are
found in the sea.

The barnacles, order Cirripedia, look but little like other
Crustacea. For a long while they were classed with the
Molluscs, but a study of their
development showed that in the
young stages they are like the
crustaceans and not the molluscs.
The young are free-swimming,
and after going through a series
of changes they become attach-
ed to some firm object. Here
the young barnacle undergoes
further metamorphosis, and the
adult form with its compact or
somewhat worm-like body is de-
veloped. The appendages, or
legs, are long, slender and curled. FIG. 44. A stalked barnacle,
The animal is enclosed in a shell fy mUL ( About * natural
often of the shape of a truncate

cone and composed of six or more plates. The open end of
the shell may be closed by a lid or operculum, thus well pro-
tecting the inmate. The barnacle feeds on minute organisms
which it sweeps into its mouth by means of the long feathery
appendages.

Although barnacles may completely cover piling and other
timbers in the water, they do not injure them and may even
be of some service in protecting them from wood-boring or
wood-destroying animals. Sometimes, however, they are
serious pests on oyster beds. The goose-barnacle, or ship-

n6 ECONOMIC ZOOLOGY AND ENTOMOLOGY

barnacle, is attached to floating objects by means of a flexi-
ble stalk which may be very short or may attain a length of
nearly a foot. In warm seas the bottoms of ships are often
so covered with these barnacles that their progress is
seriously impeded.

The very degenerate parasitic Sacculina also belongs to this
order. The young sacculina swims about freely, but soon
attaches itself to the body of a crab. After undergoing a
series of changes, one stage of which is passed within the body
of the crab, it finally becomes little more than an ovoid sack
closely applied to the host, and sending off many root-like
filaments which extend to all of the tissues of the crab from
which it derives its nourishment.

Sub-class Malacostraca. This group includes the more
highly organized Crustacea. Most of them are of considerable
size, and the appendages show much differentiation. There
are several orders, some including mostly fresh water, others
mostly marine forms, but the members of only two of these
orders are of any particular economic interest or importance
except as they furnish food for fishes and other smaller animals.

The order Decapoda, to which the crayfish belongs, is the
largest and most important order belonging to the class. The
order is divided into two groups, or sub-orders, the Macrura
and the Brachyura. In the Brachyura the abdomen is usually
much reduced in size and folded underneath the thorax.
The Macrura includes the free-swimming shrimps and prawns,
the crawling lobsters and crayfish, and the hermit crabs, sand
bugs and others.

Lobsters. As a source of food for man the lobsters rank
first among the Crustaceans. They are found along rocky
shores on both sides of the Atlantic ocean. In structure and
habits they are much like the crayfish, but they attain a much
greater size, some individuals reaching a length of twenty inches
and a weight of twenty-five pounds. At rare intervals even
larger specimens are found, but these are to be regarded as
giants. The lobsters seen in the market usually measure ten
to twelve inches and weigh from one and one-half to two and
one-half pounds. Many states do not allow lobsters to be

CRAYFISH, LOBSTERS, CRABS, SHRIMPS, ETC. 117

taken that are less than nine inches long; others place the
minimum at ten or ten and one-half inches.

The food of lobsters consists of fish and any other animals
that they can capture in the sea. Although they prefer fresh
food they do not hesitate to eat dead or even decomposing
animal matter.

Females eight or ten inches long may produce 5000 to 10,000
eggs. Very large lobsters may produce nearly ten times this
number. The eggs are glued to the swimmerets and thus
protected as are the eggs of the crayfish.

Live lobsters are brownish or greenish with bluish mottlings.
The ones usually seen in the market are red because they have
been boiled.

At one time lobsters were very plentiful and very cheap
along the New England and Canadian coasts. It was no
uncommon thing for as many as 100,000,000 to be marketed
in a year, and the price was often as low as five cents for a
large lobster. But for the last thirty years the numbers have
been decreasing very rapidly until now the catch is only a
small fraction of what it used to be, possibly little more than
one-tenth, and many of the best grounds are no longer fished
because they do not yield profitable returns. As the supply
decreased the prices rapidly increased until now in many
places lobsters sell from fifty cents to one dollar each. The
problem of how to conserve the supply that still exists is a
very important one and has been the subject of much study and
experimenting. Closed seasons and a gauge or length limit
have been tried. "Egg-lobster" laws have been passed for
the protection of the female during the time she is carrying
her eggs. But there has been only a partial check in the
destruction of the industry. With certain modifications of
these laws and with the methods of artificial propagation that
are now being practiced in some states, it is hoped that more
encouraging results may be met with. The lobster fisheries
on the seacoasts of Europe have had the same difficulties
that have been met with here.

The common American lobster is called Homarus americanus,
and the common lobster of Europe H. grammarus, the Nor-

n8 ECONOMIC ZOOLOGY AND ENTOMOLOGY

wegian lobster, Nephrops norwegicus. Around the islands off
the coast of California is a large crustacean about the size of
the eastern lobster, but the front legs are not enlarged
into the great heavy pincers. It is often referred to as the
spiny lobster, or "salt water crawfish." It belongs to the
genus Palinurus, which is represented in different parts of the
world by several species that are highly valued as food.

Shrimps and Prawns. The prawns, which are marine and
much like the lobsters but very much smaller, and the shrimps,
which occur in both fresh and salt water, are often much sought
after for food. They often occur in great "schools," and are
caught in nets or dredges, sometimes in great numbers. They
are put fresh directly on the market, or are canned and
shipped to all parts of the world. The principal shrimp fish-
eries are along the shores of the Gulf of Mexico where the
common shrimp, Crangon milgaris, is exceedingly abundant.
Most of the canned shrimp come from this region. The same
species occurs on the Pacific coast where, however, the Cali-
fornia shrimp, C. franciscorum, is more important. Besides
supplying the local markets with the fresh shrimp the California
Chinese formerly dried great quantities of them. The dried
meat was separated from the shell and exported, the value
of the export reaching $100,000, in some seasons.

Some of the largest and finest prawns and shrimps are
found in Puget Sound, but the demand for them is so great
that they seldom get beyond the local market. Like the
lobster fisheries, the shrimp fisheries have suffered from lack
of intelligent regulation.

It should be noted that these crustaceans, which occur in
untold numbers in so many waters, form a large part of the
food supply of many of our important food fishes, and the
destruction or material reduction of this source of food has
an effect more far-reaching than at first appears.

The hermit crabs, which are more nearly related to the
shrimps and prawns than to the true crabs, found along all
seashores, well illustrate the structural changes that may be
brought about by a special or peculiar mode of life. Very early
the young animals seek out an empty shell, such as a snail or

CRAYFISH, LOBSTERS, CRABS, SHRIMPS, ETC. 119

periwinkle shell, in which they may hide. The body is thrust
well into the shell and the opening guarded by the feet and claws.
As the crab develops it becomes more and more adapted to the
shell in which it is living. The abdomen remains soft and
follows the convolutions of the shell. Only the last two
abdominal appendages remain, and these are modified into
hook-like organs. The first two or three pairs of thoracic legs

FIG. 45. A hermit crab, Pagarus sp. in a sea-snail shell. Upper figure
shows another crab removed from its shell. (Reduced.)

become curiously modified and help close the opening of the
shell. The right claw is often very much larger than the left
and well fitted for the dual purpose of capturing prey and
acting as a door. As the crab grows, its adopted home be-
comes too small for it, and from time to time it must seek
larger shells.

Some of the hermit crabs always have certain stinging

120 ECONOMIC ZOOLOGY AND ENTOMOLOGY

hydroids or sea-anemones attached to their shells. Both
animals doubtless derive some benefit from this association,
the crab being protected from its enemies and the hydroid or
anemone being moved from place to place where food is more
abundant and perhaps gathering some of the bits that are
scattered in the water when the crab is feeding. This is
another example of commensalism, or symbiosis.

The sand-bugs, genus Hip pa, so numerous on sandy beaches,
burrowing rapidly into the loose sands or sometimes swimming
about in the tide pools, are an important source of food for
some fish.

Many other interesting forms in this sub-order, some of them
of more or less economic importance, might be listed, but the
kinds already mentioned serve to show something of the
diversity of structure and habits of the group.

Crabs. The true crabs, belonging to the sub-order Brachy-
ura, differ from the crayfish and lobsters in having the body
short and broad instead of elongate and rounded. The
cephalothorax is often broader than long. The abdomen is
relatively small and is bent under the cephalothorax so that but
little of it is visible from above. The appendages are usually
well developed and similar to those of the crayfish or lobster
except that the number of abdominal appendages is reduced
to two pairs in the male and four pairs in the female. Most
crabs are scavengers, living on dead animal matter. During
their development they undergo a remarkable metamorphosis.
In some of these stages they are so unlike the adult that they
were described as different animals. The names, such as
zoea and megalops, given to these supposedly distinct animals,
are still retained, but we know now that they refer to different
stages in the development of the crab.

Most of the crabs live in the shallow waters near the shore,
but some live in deep water and a few live on land. Their
habits are various and there is a corresponding variation in
their structure and shape, size and coloring.

The spider crabs, with their long, slender legs and com-
paratively small body, are especially strange looking creatures.
Some members of this group living in Japanese waters measure

CRAYFISH, LOBSTERS, CRABS, SHRIMPS, ETC. 121

twelve to sixteen feet across the extended legs, the body itself
being but little more than a foot in width or length.

The fiddler crabs, Uca spp., so common along the Atlantic
coast, are the clowns among the crabs. The males have one
of the chelae very much enlarged, and when alarmed they
move this swiftly back and forth with a motion ridiculously
like that of a violinist with his bow.

The blue crab, or "soft-shelled" crab, Callinectes hastatus,
is the most important as a source of food on the Atlantic
coast. On the Pacific Coast a much larger crab, Cancer
magister, is taken in shallow waters, sometimes in considerable
numbers, and is much prized.

The horseshoe crab, or king-crab, Limulus, common all along
the Atlantic coast, is really not a crab at all, nor even a crus-
tacean, but belongs to another class,
the relationship which is uncertain.
Many believe that Limulus is most
nearly related to the spiders.

The beach fleas, order Amphipoda,
are perhaps the most numerous crus-
taceans found on the sea beaches, oc-
curring in countless numbers in the
tossed up seaweeds and mosses and
other sea wrack. They are important
as food for other marine animals. The
boring Amphipod, genus Chelura,

works on submerged timber, often

, . , , r j FIG. 46. A sow-bug,

doing a great deal of damage. isopod, species not deter-

The wood-lice or sow-bugs, order mined.
Isopoda, are among the few crus-
taceans that live a wholly terrestrial life. They live in moist
places, feeding chiefly on decaying vegetable matter, but
sometimes attacking tender plants and doing more or less
damage in gardens and green-houses. Although land animals,
they breathe by means of gills which are situated on the under
side of the abdomen. It is therefore necessary for them to
live in places where the gills may be kept damp in order that
there may be a ready transfer of gases through the membranes.

122 ECONOMIC ZOOLOGY AND ENTOMOLOGY

Their breeding or hiding places are usually easily found and
destroyed, or sliced potatoes or substances poisoned with
Paris green may be placed where the sow-bugs can find them.
Some members of this same order live in fresh water, others
are marine.

The gribbles, genus Limnoria, are another group of crus-
taceans that are very destructive to piles and other submerged
woods, which they may completely honeycomb to the depth of
half an inch or more. Where abundant they may cause the
piles to lose as much as an inch of surface each year. It is a
common practice now to give the piles a coat of creosote, or
better still to drive the creosote into the wood by pressure, in
order to protect it from the ravages of these and other wood
boring species. These gribbles attack and destroy much
floating and water-logged timber that might otherwise become
serious obstructions to navigation.

CHAPTER XVI

SLIME SLUGS, MYRIAPODS AND INSECTS

Slime Slugs. The slime slugs, composing the small class
Onychophora of the great branch Arthropoda, are curious, soft-
bodied, many-legged, but sluggish creatures
about two inches long, that live under bark or
stones mostly in sub-tropic and tropic lands.
About fifty species of them are known. The
best known genus is named Peripatus. They
capture small insects for food by ejecting slime
on them from glands in the mouth. Their
bodies show a curious combination of worm
character and arthropod characters. The ani-
mals really seem to be a sort of link between the
Annelida and the Arthropoda.

Myriapods. The class Myriapoda 1 includes
the familiar thousand-legged or galley worms
and centipedes as well as certain smaller crea-
tures bearing only a few pairs of legs. They
are land animals, and have the body segments
nearly uniform in size and shape, except the
head which bears the mouth-parts and antennae.
The presence of true legs on most of the seg-
ments of the hinder part of the body and the
lack of the grouping of these segments into
distinct thorax and abdomen are the further
external structural characteristics which distin-
guish myriapods from insects. The internal
anatomy corresponds in general character with
that of the Insecta.

1 Modern classification tends to discard the long recognized class
Myriapoda in favor of two classes, one for the centipedes and allies, and
the other for the thousand-legged worms and allies.

123

FIG. 47.-
Peripatus el-
se ni (Mex-
ico). (Length
about two
inches.)

124 ECONOMIC ZOOLOGY AND ENTOMOLOGY

The most familiar myriapods are the millipeds or galley
worms, the centipedes, geophilids, and lithobians. The milli-
peds are cylindrical in shape, have two pairs of legs on most
of the body-segments and are vegetable feeders, though some
may feed on dead animal matter. The galley-worms, Julus
spp., large, blackish, cylindrical millipeds found under stones
and logs and leaves in loose soil, are familiar forms. They
crawl slowly, and when disturbed curl up and emit a mal-
odorous fluid. They can easily be kept alive in shallow glass
vessels with a layer of earth in the bottom, and their habits

FIG. 48. A milliped, Julus sp. (Natural size.)

and life history may thus be studied. They should be fed
sliced apples, green leaves, grass, strawberries, fresh ears of
corn, etc. They are not poisonous and may be handled with
impunity. They lay their eggs in little spherical cells or nests
in the ground. An English species, of which the life history
has been studied, lays from 60 to 100 eggs at a time. The
eggs of this species hatch in about 12 days.

The lithobians, centipedes and geophilids are flattened and
have but a single pair of legs on each body-ring. They are
predaceous in habit, catching and killing insects, snails, earth-
worms, etc. They can run rapidly, and have the first pair
of legs modified into a pair of poison claws, which are bent
forward so as to lie near the mouth. The common "skein"
centipede, Scutigera forceps, is yellowish and has fifteen pairs
of legs, long 4o-segmented antennae, and nine large and six
smaller dorsal segmental plates. The true centipedes, Scolo-

SLIME SLUGS, MYRIAPODS AND INSECTS 125

pendra spp., have twenty-one to twenty-three body-rings,
each with a pair of legs, and the antennae have seventeen to
twenty joints. They live in warm regions, some growing to
be as long as twelve inches or more. The "bite" or wound
made by the poison claws is fatal to insects and other small
animals, their prey, and painful or even dangerous to man.
The popular notion that a centipede
"stings" with all of its feet is falla-
cious. It is recorded by Humboldt
that centipedes are eaten by some of
the South American Indians. The
geophilids are very slender-bodied and
usually rather long centipede-like
forms with as many as 300 pairs of
legs. They are usually yellowish and
are common in damp places under
stones or logs, or in the ground.

Insects

The great class Insecta, with its
350,000 known species, is a group of
animals of special importance in the
study of economic zoology. As we
know but few more than 500,000
different kinds of animals altogether,
it is apparent how dominant among
animals, as regards numbers at least,
the insects are. In fact we might

well call this the Age of Man and FlG - 49- A centipede
, ... .,1 ..i i- Scolopendra sp. (Natural

Insects, to contrast it with the earlier size S

Age of Reptiles, Age of Fishes, Age

of Invertebrates, etc. The insects include more kinds of
animals directly injurious to the material welfare of man
and to his health and duration of life than any other animal
group. So it is that as students of economic zoology we
must give insects, and their relations to man, a more detailed
consideration than we shall give any other animals.

126 ECONOMIC ZOOLOGY AND ENTOMOLOGY

Although from the silk- worm we get all the silken cloth and
thread we use, and from the honey-bee all the honey and
beeswax, yet these are almost the only species of insects of all
the myriad living kinds that afford man useful products.
But in two other and far more important ways, insects are of
direct benefit to us. Some of them act as scavengers of con-
siderable importance, and many of them kill injurious species
of their own class. It is, indeed, on the many predaceous and
parasitic insects that we rely for chief protection from the
many injurious and dangerous kinds. We can, and do,
make much headway against injurious insects by the use
of artificial remedies, but without natural checks on their
increase, among which checks the attacks of other insect
species are the most important, insect pests would overrun us
completely.

A knowledge of the special structure, physiology and mode of
development of insects is necessary as a basis for good work in
economic or applied entomology. And a knowledge of insect
classification, which of course is based on similarities and
dissimilarities both of structure and of development and habit,
and which indicates by a few words the existence of these
resemblances and differences, is also most important to the
economic entomologist. Hence our first consideration of
insects will concern itself with their structure, physiology,
development and classification. The study of the grasshop-
per, already made, has given us a good understanding of the
insect body. But there is much modification, or specialization,
of general body-shape and character as well as of the various
particular parts of it, as antennae, mouth -parts, legs, wings,
etc., and it will be advisable to examine in some detail the
external features of the body of a highly specialized insect
such as the honey-bee. A number of statements concerning
the general make-up of the insect body, already made in con-
nection with the study of the grasshopper, will be repeated and
expanded and a number of technical names of parts of the
body redefined. The grasshopper was studied primarily as
an introduction to the invertebrates in general. The bee will
be studied primarily as an introduction to the insects.

SLIME SLUGS, MYRIAPODS AND INSECTS 127

THE EXTERNAL STRUCTURE OF THE HONEY-BEE

Body -wall. The body of a bee, which is a well-developed
insect type, is, let us note first of all, entirely covered by a firm
body wall or hardened skin. This body-wall is composed of
two layers, an inner, very thin and soft, cellular layer, the cells
being arranged side by side to form a skin membrane, only
one layer of cells in thickness, and an outer, thicker, non-cellu-
lar cuticular layer, composed of material secreted by the skin
cells and perhaps partly of the hardened outer ends of these
cells themselves. This thick, firm, colored cuticle is made up of

FIG. 50. Honey-bee, Apis mellifica. (Nearly 3 times natural size.)

successive fine laminae well fused together, and is composed
chiefly of a complex sustance called chitin. It is this chitinized
cuticle which gives the body-wall of insects its hardness, and
makes of it not only a firm protecting cover for the soft parts
within but also an exoskeleton to which the muscles are
attached. The chitinized cuticle, although extending continu-
ously over the body, is flexible in certain places, as between the
head and thorax, thorax and abdomen, various abdominal
segments and at the articulations of antennas, mouth-parts,
legs, wings and between the various antennal, mouth-part
and leg joints, etc. This is necessary, of course, for the
effective movement of all these parts. Such flexible places
in the cuticle are called sutures, while the firmer, fixed parts
are called sclerites.

128 ECONOMIC ZOOLOGY AND ENTOMOLOGY

Body -regions and Segments. The body of a honey-bee, like
that of a grasshopper, is made up of three readily distinguish-
able main parts or regions, the head, thorax and abdomen, each
part bearing its special appendages, as antenna; and mouth-
parts on the head, legs and wings on the thorax, and the
parts forming the sting on the abdomen.

Each of the main body-regions is composed of several body
segments, but in the head and thorax these segments are so
fused as to be hardly distinguishable as separate parts. In the
abdomen, however, six distinct segments can be distinguished.

All insects have the body fundamentally composed of suc-
cessive segments grouped more or less compactly into three
body regions. The typical number of segments fused to form
the head is probably six, perhaps only four. The thorax
is composed of three, called prothoracic, mesothoracic, and
metathoracic, segments, while the abdomen comprises from
seven to eleven segments, although in some insects these may
be so fused as to make the abdomen seem made up of but three
or four, or even a single segment.

Segmented Appendages. The antennae or "feelers" of the
head, the legs, and less plainly the mouth-parts, show that
each of these movable appendages of the body is made up also
of a series of successive segments or "joints." The hardened
body wall, the segmentation of the body, and the segmentation
or jointing of the body appendages, of the bee and all other
insects, are the fundamental characteristics that show their
relationship to the crustaceans, myriapods, spiders and other
Arthropoda.

Mouth -parts. The mouth-parts of the bee are composed of
a skin flap called upper lip or labrum, a pair of firm, trowel-like
little jaws or mandibles used chiefly for moulding the wax
when the cells are being built, and a complex tongue-like organ
composed of various parts as shown and named in Fig. 51.
This " tongue" is the nectar-gathering organ, and is so arranged
that its various parts can be held together so as to form an
imperfect tube inside of which a long hairy rod moves back and
forth. The flower-nectar taken up on the expanded tip of this

SLIME SLUGS, MYRIAPODS AND INSECTS 129

hairy rod is forced up the tube by the pressing together of the
parts composing its walls.

Antennae and Senses. The two feelers, or antennae, of the
bee are slender, elbowed processes, each composed of thirteen
small segments, which can be moved freely, and extend out in
front of the face so as to be in advance of the head when the
bee is flying or walking. They are general
organs of touch and smell and probably
also of hearing. Each of these senses
has its own particular specific organs on
the antennae, those of feeling being fine
tactile hairs and papillae, those of smell
being variously shaped very minute pits
or cones, each with a fine nerve ending
in it, while those of hearing are more
problematical. But it has been proved
that many insects have special auditory
organs in the antennae consisting usually
of fine hairs which can be set into vib-
ration by the sound waves, and an elabo-
rate receiving arrangement, in the second FlG 5 x Mouth-
segment, of chitin rods, delicate nerve parts of a honey-bee

fibers, special ganglion cells and an audi- with maxilla and man-

. . , i rr^i dibles of one side re-

tory nerve running to the brain. The moved . md ^ mam li-

male mosquito has a very highly deve- ble; mx., maxilla; mx.p.

loped auditory apparatus of this type. maxillary palpus; mx.l

J , f maxillary lobe; si.

A few insects, such as the grasshopper, st i pes O f maxilla; cd.

katydids, crickets and others have a cardo of maxilla; //.
very different kind of "ear," not situated .

on the head, but on the abdomen (in mentumof labium; pg.
the grasshoppers), front legs (in katydids paraglossa. g/., glossa

1. ^t u j lip-, labia palpus,

and crickets), or elsewhere on the body.

This kind of ear is composed of a small, thin vibratory drum
or tympanum, with an air-space underneath it, and a tiny
ganglion and special nerve in connection with it.

The sense of smell is very highly developed in most insects.
Indeed it is probable that most of an insect's sensation of out-
side things comes through its organs of smell. And the

130 ECONOMIC ZOOLOGY AND ENTOMOLOGY

minute pits and cones or papillae which are the organs of smell
and are stimulated by substances in gaseous or otherwise
very finely divided condition, may be very abundant, several
thousand being present on each of the bee's antennae.

FIG. 52. Different kinds of insect antennae, i, From a ground beetle,
Pterosliclnts calif ornic us; 2, from a carrion beetle, Silplu ramcsa; 3, from a
click beetle, Melanotus variolatus; 4, from a honey-bee, Apis mellifica;
5, from a Scarabaeid beetle, Li gyms gibbosus; 6, from a blow fly, Calli-
phora wmitora. (About 12 times natural size.)

Eyes and Sight. On the head, also, beside the antennae
and mouth-parts, are the eyes. These are of two kinds, namely
a pair of large compound eyes and three smaller simple eyes or

SLIME SLUGS, MYRIAPODS AND INSECTS 131

ocelli. The external surface of the compound eyes is revealed
by the microscope to be divided into many small hexagonal
facets. Each of these is a minute, rigid, flat lens behind which
exists, arranged as a slender, rod-like organ,
a perceptive unit of the compound eye.
These units are called ommatidia, and each
one is composed of a crystalline part just
behind the external lens, surrounded by pig-
ment, and behind this a sensitive nerve end-
ing, called a rhabdome, also surrounded by
pigment. From the rhabdome a fine nerve
runs backward to join with the similar fine
nerves from the other ommatidia to form
the large optic nerve going to the brain.
Each ommatidium is thus a complete little
eye with light gathering and transmitting
and perceiving apparatus, but without means
of change of focus, and only slight means of
adjustment to varying intensity of light.

This slight means of adjustment depends
on the power of the insect to move the pig-
ment surrounding the ommatidia back and
forth, and thus to arrange it in a way to
allow more or less light to reach the rhab-
domes.

Most of the light rays that enter each om-
matidium must be those that fall nearly ver-
tically on the external lens, and pass verti-
cally in to the sensitive rhabdome. Thus
each ommatidium "sees" only any object or
part of any object directly in the line of its ^; pigment; >-.,
long axis, and as the surface of the compound retinal parts; O.H.,
eyes of insects is usually strongly curved, (fter "j^ner;
separate ommatidia usually see only separate greatly magnified.)
points in objects of the environment. These
points put together side by side form a mosaic correspond-
ing to the object or objects in front and at the sides of the
eyes. Such seeing is called mosaic or apposed vision.

-on

FIG. 53. Lon-
gitudinal section
through a few
facets and eye-ele-
ments (ommati-
dia) of the com-
pound eye of a
moth. /., cor-
facets; cc.,

132 ECONOMIC ZOOLOGY AND ENTOMOLOGY

However, when the pigment surrounding the ommatidia
is drawn back from their anterior ends, light rays can pass
through the lateral walls of the ommatidia from the lenses
of adjoining ommatidia, and thus the reflected rays from a
single point in an object may reach and stimulate several
adjacent rhabdomes, forming a picture in a somewhat different
way from that by the strict mosaic method. This picture is
called a superposition image as contrasted with the apposition
image of the true mosaic vision.

The focal distance of the lenses in the compound eyes is
usually about two yards, so that these eyes see objects best at

that distance from the insect.
The sharpness or clearness of the
image formed depends, too, on
the number and size of the sepa-
rate ommatidia. The smaller
and the more numerous they
are the more perfect will be the
mosaic; that is, the more complete
and clear will be the picture seen.
The number of facets in the com-
pound eyes of insects varies from
three or four to twenty thousand
or more.

The simple eyes, or ocelli, are
very different from the com-

FIG. 54. Part of corneal
cuticle, showing facets, of the
compound eye of a horse-fly,
Therioplectes sp. (Greatly
magnified.)

pound eyes in make-up. Each ocellus has but one lens, but
behind it is a varying number of sensitive or optic cells each
with anterior crystalline part and posterior retinal or percip-
ient part. But the very short focus of the lens, usually but a
few inches, and the primitive character of the structure of the
part behind the lens, limit the vision probably to little more
than a perception of shadows in imperfect outline. The
ocelli can only perceive objects very close to the insect, and
then with but little clearness. In fact the vision of insects,
either by means of compound or simple eyes, is at best imperfect
when compared with that of the vertebrate animals. Although
observation and experiment have shown that insects can dis-

SLIME SLUGS, MYRIAPODS AND INSECTS 133

tinguish colors and pattern when the color shades and the
outlines are strongly contrasted, yet on the whole insect eyes
are much better constructed for quickly recognizing moving
bodies and passing shadows than for seeing in detail either
the shape or the color pattern of objects.

Legs. The appendages of the bee's thorax are the legs and
the wings. The thorax is composed of three closely fused body

_FiG. 55. Legs of honey-bee. A, Left front leg of worker, anterior
view, showing position of notch, dd., of antenna cleaner on base of first
tarsal joint, tar., and of closing spine ee, on end of tibia tb; B, spine of
antenna cleaner, ee, in flat view; C, details of antenna cleaner; D, left
middle leg of worker, anterior view; E, left hind leg of worker, anterior or
outer view, showing the pollen basket, cb, on outer surface of tibia,
tb and the so-called "wax-shears," //. F, inner view of first tarsal
joint of hind leg of worker, showing rows of pollen-gathering hairs
on tarsus, tar. (After Snodgrass.)

segments. Each of these segments bears a pair of legs, but
only the hinder two bear pairs of wings. The legs of the bee
are of the number characteristic of insects. However, some
insects have the legs wanting. In such insects as have adopted
a strictly sedentary life, as the scale insects, absence of the

i 3 4 ECONOMIC ZOOLOGY AND ENTOMOLOGY

legs is the rule rather than the exception. The bee's legs are
well fitted for walking, but they are also modified, the hinder
ones especially, for the performance of other functions. The
fore legs carry a number of branched hairs and curved bristles
for collecting pollen. They also have a curious little combina-
tion of structures called an antenna cleaner composed of a
rounded indentation lined with a row of short spines and nearly
closed by a large movable spine. The middle legs have also
pollen-gathering hairs and a curved spine which is used to pry
the pollen from the hindmost pair of legs. The hindmost
legs are most modified of all. They have a so-called "pollen
basket," or concave outer surface margined with curved bris-
tles; "pollen combs" composed of transverse rows of short
strong hairs; and, finally, a structure called the "wax-pincers,"
being the two opposed edges of two joints of the leg, one lined
with spines, the other smooth. This structure, according
to Casteel, has nothing to do with cutting wax, but aids in
the gathering of pollen.

The separately articulated parts or joints of each leg have
been given special names. Beginning with the one which
articulates with the body, called the coxa, the others are the
trochanter, a very small one, the femur, which is the largest,
the tibia, which is next in size to the femur, and finally the
tarsal segments, which, in the bee, are five in number. The last
or terminal one bears a pair of claws and a little pad called the
puhillus, lying between the claws. These tarsal segments
vary from one to five in different insects.

The legs of insects show great variety in structure and use.
Aquatic insects have one or more pairs of the legs modified to
be swimming organs; subterranean insects have digging legs;
leaping insects have the hindmost pair usually very large and
long. Some predaceous insects have the forelegs modified
to be grasping or lacerating organs. In fact only those in-
sects which use their legs exclusively for walking and running
have them in a condition w r hich might be called .unmodified.
In such insects they are usually long and slender with the seg-
ments more or less cylindrical in shape.

The last tarsal segments of the different legs can be called the

SLIME SLUGS, MYRIAPODS AND INSECTS 135

feet, for it is on the claws and little pads present on these seg-
ments that the insect stands. Insects that can climb on
smooth surfaces or walk on overhanging walls have small
hollow hairs on the pads of the feet from which a sticky se-
cretion issues.

Wings. Bees' wings are four in number, which is the typical
number for insects in general. However, many insects, in-
cluding all the true flies or Diptera, have but a single pair of
wings. Parasitic insects, such as fleas, lice, etc., are usually
wingless. All of the living wingless insects, except a single
small group called the Aptera, are believed to have lost their
wings by degeneration. The Aptera, however, are believed
to be the immediate descendants of the primitive wingless
ancestors of the whole great insect class.

The bees' wings are membranous, very thin and trans-
parent, and supported on a framework of branching veins.
The wings of maity insects, however, are thickened, as for ex-
ample the fore wings of grasshoppers and all beetles. The wing
veins may be few in number as with the bee and house-fly,
or many, as in the hind wings of the grasshoppers. Most
of the butterflies and moths have their wings covered com-
pletely above and below with fine scales in which pigment of
various colors is held. In the two-winged flies it is the hind-
most pair of wings that is lost, or rather is replaced by a pair
of very different structures, small stems with expanded tips,
called balancers. In one small group of insects, however, it
is the front pair of wings that is gone.

The two wings on each side of the bee's body can be fastened
together, and are, when the bee is flying, by a row of tiny
hooks along the front margin of the hind wing which catch
hold of the hind margin of the front wing. This is a device
which makes the bee practically tw r o-winged when in flight.
Some other insects, as most of the butterflies and moths,
for example, also have means for fastening the two wings of
each side together.

Sting. The appendages of the abdomen, although several
in number, are all combined to form the sting. This sting
is made up of a sheath containing two movable barbed darts

136 ECONOMIC ZOOLOGY AND ENTOMOLOGY

and a pair of sting feelers which probably act as sense organs.
The sting is connected by a duct with a poison reservoir which
is supplied with poison from a pair of interior glands.

Wax Plates. On the under side of each of the last four seg-
ments of the worker-bee there is a pair of wax plates. The wax
issues as a fluid from small glands in these plates. On its
issuance it spreads out over the surface of the plates and
hardens. It can then be plucked off in thin sheets by the bee.

THE INTERNAL STRUCTURE or A CATERPILLAR

The body of the bee is too small to be dissected easily.
For a study of the internal insect anatomy we may take a
caterpillar; any kind will do, although one with a naked in-
stead of hairy body will be more convenient to use. Although
caterpillars are immature insects they are the young stages
of butterflies and moths they will reveal all the important
organ systems, except one, in well-developed condition. The
one exception is the reproductive system, which may be
examined in a full-grown grasshopper.

Adipose Tissue. On opening the body of the caterpillar
the first thing noted is a mass of whitish flocculent material
which is fat, or adipose tissue. It is formed out of the surplus
food eaten by the voracious caterpillar, and is used during the
time which the insect spends in the chrysalis stage when it is
inactive and cannot feed. This adipose tissue lies all around
and over the various internal organs, and must be picked
away to reveal them.

Alimentary Canal. The most conspicuous organ visible,
after the fat is removed, is the long straight alimentary canal
running from mouth to anus through the middle of the body.
It is composed of successive parts, named, beginning at the
mouth, esophagus, ventriculus or stomach, small intestine,
large intestine and rectum. Where the ventriculus and
small intestine join, a few delicate, whitish, thread-like con-
voluted tubules arise known as the Malpighian tubules. These
correspond in function to the kidneys of other animals, taking
up and excreting waste from the blood.

SLIME SLUGS, MYRIAPODS AND INSECTS 137

138 ECONOMIC ZOOLOGY AND ENTOMOLOGY

If the caterpillar is of a kind that spins a coccoon when it is
ready to change into a chrysalis, the silk glands will be found as
a pair of long, smooth, rather thick, whitish cords lying one
on each side of the alimentary canal and running forward to
the mouth. Another pair of smaller, shorter tubes, not ex-
tending farther back than about the beginning of the ventri-
culus are the salivary glands. The silk glands are, indeed,
only an enlarged and modified second pair of salivary
glands.

Respiratory System. In taking out the adipose tissue and
alimentary canal there will be noted many dark little thread-
like processes which are in reality fine tubes, called trachea.
By tracing them to their origin they will be found to arise
from larger tracheae, which in turn are given off from main
longitudinal trunks. There are two or four of these trunks,
one or two on each side of the body, and from them arise
not only the branches that by repeated subdividing extend
to all parts of the body, but short strong lateral trunks
that run to small openings called spiracles, or stigmata, in the
sides of the body. In most caterpillars nine pairs of spiracles
will be found, one pair on the prothoracic segment and the
others on the abdominal segments, one pair to each. The
spiracles and tracheae are the organs of the respiratory system of
the caterpillar, and similar organs, although varying much in
number and arrangement, will be found in all insects, except
a few very small and thin-skinned ones, which respire directly
through the skin. The spiracles show on the outside of the
body as small blackish spots, but are actually small openings
in the body-wall, provided usually with valves or fringes of
hairs to keep out foreign particles. They allow air to pass into
the interior system of tracheae, and carbon dioxide to pass out.
The tracheae, although thin-walled and delicate, especially
the finer ones, are lined with a thin chitinous membrane in
which are spiral thickenings which hold them open and give
them a certain necessary elasticity. When the insect contracts
certain muscles lying as longitudinal and circular bands along
the inner side of the body-wall, the pressure of the body con-
tents forces the tracheae to close and expels the gas in them out

SLIME SLUGS, MYRIAPODS AND INSECTS 139

through the spiracles. When the muscles are relaxed and the
pressure is removed the elastic- walled tracheae open again and
are filled with fresh air which rushes in through the open
spiracles. One can readily see this alternate contraction and
expansion, or respiratory movement, of the body in a live
grasshopper.

The respiratory system of insects is, as we have learned from
its condition in the caterpillar, very different from that of the
vertebrate animals. There is no breathing through nostrils or
mouth on the head; there are no lungs; there is no taking up
and carrying of oxygen by the blood. The air that enters an
insect's body through the spiracles is carried to every smallest
part of it by the tracheal tubes. Similarly these tubes take
up from the tissues and cells of the body waste carbon dioxide
and carry it outside the body. The blood has nothing to do
with respiration in insects. It only gets what air it needs for
itself.

Circulatory System. The blood of insects is better called
blood lymph because it is always a mixture of blood and
lymph. There is no elaborate system of arteries and veins,
but only a single main longitudinal vessel which lies just under
the body-wall of the middle of the back, and is sometimes called
heart, but more often, simply, dorsal vessel. To see this organ
in a caterpillar it is necessary to cut one open longitudinally
along the middle of the underside and to take out carefully
all the fat tissue and the alimentary canal. Then there may
be seen running along the inner surface of the body-wall of
the back a delicate membranous flattened tube which is
composed of a number of successive chambers separated from
each other by delicate valves and provided also with small
lateral openings also furnished with valves. In the thin walls
there are delicate muscle fibers, so that the vessel can contract
and expand as these muscles are contracted and relaxed.
This pulsation, combined with the arrangement of the valves,
allows the blood lymph, which everywhere else in the body is
not confined but flows freely among the body organs, to enter
the dorsal vessel through the lateral openings and be forced

140 ECONOMIC ZOOLOGY AND ENTOMOLOGY

forward from one chamber to another until it issues from a
narrow anterior extension of the vessel, called the aorta.

In many insects the dorsal vessel is not so long and slender as
in the caterpillar, nor composed of as many chambers. But in
all insects the circulatory system comprises nothing more than
a pulsating dorsal vessel and the blood lymph flowing freely
everywhere in the body cavity.

Nervous System. Extending along the
middle of the floor of the caterpillar's body
will be seen a delicate white thread with
small expansions or knots in it arranged
segmentally, but wanting in the last two
abdominal segments. In the head there

FIG. 57. FIG. 58.

_FiG. 57. Diagram of circulatory system of a young dragon-fly; in
middle is the chambered dorsal vessel, or heart, with single artery. Arrows
indicate direction of blood-currents. (After Kolbe.)

FIG. 58. Diagram of ventral nerve-cord of locust, Dissosteira Carolina.
(After Snodgrass.)

is a knot underneath the esophagus and from it a pair of
stout threads which run up and around the esophagus,
one on each side, and into a larger knot lying on top of the
esophagus.

These knots and thread compose the main part of the central
nervous system of the caterpillar, the threads being the nerve-

SLIME SLUGS, MYRIAPODS AND INSECTS 141

cords or connections, and the knots, the ganglia, or nerve cen-
ters. The ganglion in the head above the esophagus is called
the brain, and from it nerves run to the eyes and antennae.
From the head ganglion under the esophagus nerves run to the
mouth-parts. From the ganglia in the thoracic segments
nerves run to the legs and to the strong thoracic muscles that
move the legs. In insects with wings, nerves run from these
ganglia also to the wing muscles. From the ganglia in the
abdomen nerves run to the various body organs such as ali-
mentary canal, dorsal vessel, tracheae, muscles, etc. Thus
although the head ganglia of an insect may be looked on as
the most important nerve centers of the body, and one is
called the brain, by analogy with the brain of vertebrate
animals, yet really each ganglion is a little brain for its own
part of the body, and there is a good deal more independence
about the control of the different parts of the insect's body than
there is in the vertebrate's body.

Although the ganglia and connecting longitudinal cord, or
commissure, seem to be single knots and a single thread, they
are in reality all double, each ganglion consisting of a pair
fused together on their inner faces, and the connective com-
missure also is composed of two cords lying so close together
as to seem but one.

In most insects there are not as many ganglia as we find in
the caterpillars, the reduction in number being brought about
not so much by the loss as by the fusion of ganglia. The
typical six or seven abdominal ganglia may be fused to form
but two or three or even one, and the three thoracic ganglia
are also often fused to form a single one. In certain highly
specialized insects, indeed, all the abdominal and thoracic
ganglia join to form one large thoracic nerve center, or "body
brain," as it has been called. Only in young insects and in
adults belonging to generalized or primitive species, are there
separate ganglia for most of the segments of the body.

Besides the central nervous system, most insects have also a
sympathetic nervous system, which usually consists of a very
small ganglion just in front of the brain, and one or two small

142 ECONOMIC ZOOLOGY AND ENTOMOLOGY

ganglia lying on the sides of the alimentary canal, all these
ganglia being connected by fine nerve-cords.

Musculature. Lying next to the skin of the caterpillar's
body can be seen many muscles, some of them extending
longitudinally and others as transverse or circular bands. Also
in the head and thorax are many other muscles for moving the
mouth-parts and legs. Most insect muscles are small and
short, so that for the complete musculation of the body a great
many separate muscles are required. Several thousand have
been counted in the body of a single insect.

The muscles which lie against the inside of the body-wall in
the caterpillar are repeated almost ^identically for each seg-
ment. This musculation then can be said to be segmental in
character just as we have found that the respiratory system,
nervous system and even the dorsal vessel can be said to be
segmentally arranged. That is, the internal systems of organs
of the insect show as plainly, almost, as the external surface of
the body, the fundamental segmental make-up. And they
also show, just as the outside of the body does, the bilateral
symmetry of the body. If the insect's body be cut longi-
tudinally by a vertical plane it will be divided into equal halves,
both external and internal organs either being in pairs, one
member on each side of this vertical plane, or being made of
fused pairs lying in this vertical plane.

Reproductive System. As the caterpillar is only an im-
mature moth or butterfly its reproductive system is not fully
developed. Any adult insect of good size and not too hard wall
may be used to study the organs of reproduction. A grass-
hopper will do very well.

In the female the eggs are produced in many small tubules,
called ovarioles, which are grouped to form two ovaries (right
and left) from each of which runs an oviduct. The two oviducts
unite to form a single wider short tube called the vagina.
From this the eggs pass out of the body in little packets. The
eggs are fertilized while still in the body of the female by
spermatozoa that have been received from the male and held
in a small sac called the spermatheca. Each egg is inclosed in
an inner, thin mtelline membrane and an outer thicker firmer

SLIME SLUGS, MYRIAPODS AND INSECTS 143

shell or chorion. But a small hole, called micropyle, is left
at one pole in both these coverings, and through this a sper-
matozoan enters the egg while it is in the vagina, or a special
posterior part of it called the bursa copidatrix.

The organs of the male that produce the spermatozoa are
called testes, and correspond in position and function to the
ovaries of the female. They are also composed of many
tubules, but they are closely pressed together to form a small
solid ovate mass. From each testis
runs a duct, the vas deferens,
through which the spermatozoa
pass to reach the single ejaculatory
duct, from which they are expelled
by the male at mating.

TYPES or MOUTH-PARTS

Corresponding to the great vari-
ety of food taken by insects is a
great variety in structure of mouth-
parts. The mouth-parts of the
honey-bee, which laps up flower
nectar, are very different from
those of the grasshopper, which
bites off and chews green leaves.

And very different from either of mdlifica, reproductive organs,
.v ,1 ,1 sting and poison glands of

these, again, are the mouth-parts que n> dors view 6 (Grea ti y

of a butterfly or moth, or of a magnified; after Snodgrass.)
mosquito, or a squash-bug.

To the economic entomologist a knowledge of the kind of
mouth-parts possessed by any insect pest is very important.
For on the structure of its mouth will depend largely the kind
of artificial remedy which must be devised to kill it. For ex-
ample, if an insect pest of fruit trees has a piercing and sucking
mouth, then spraying the surfaces of leaves with an arsenical
poison will do little good, for it gets its food, plant sap, from
the interior of the leaf or stem. But if it has a biting and chew-
ing mouth then such a poison sprayed over the leaves may be

FIG. 59. Honey-bee, Apis

144 ECONOMIC ZOOLOGY AND ENTOMOLOGY

very effective. For with each bite of leaf the insect will
get a little dose of poison, and a few such doses will kill it.
Students of economic entomology should therefore pay special
attention to insect mouth-parts. The following brief descrip-
tion of several different types of mouth parts may serve as an
introduction to this study.

Mouth-parts of Grasshoppers. A familiar type of the biting
insect mouth is that of the grasshopper. Here the

FIG. 60. Mouth-parts of grasshopper, a, Labrum; b, tongue; c,
mandibles; d, maxillas; c, labium; m.x p., maxillary palpi; /./>., labial
palpus. (Greatly magnified.)

upper lip or labrum, inclosing the mouth above is broad and
flap-like, and the jaws, or mandibles, which like the honey-
bee's, open and shut laterally, are large, strong, heavily
chitinized and have their biting edges furnished with small
tooth-like projections. The maxilla, sometimes called second
pair of jaws, which, with the mandibles, close the mouth at
the sides, are each composed of several parts, movable on
each other, of which one is a small feeler, or maxillary palpus,
bearing at its tip many taste buds. The under lip, or labium,
is a broad flap-like piece also made up of several articulating

SLIME SLUGS, MYRIAPODS AND INSECTS 145

parts of which two are feelers, or labial palpi, much like the
maxillary palpi and also provided with taste buds at their
tips. With the strong, hard-toothed jaws the grasshopper
can bite off and crush not alone bits of soft green leaves but bits
of plant stalks and even woody stems. The biting type of
mouth-parts like the grasshopper's, although with many slight
differences in the make-up of the various parts, is possessed
by the cockroaches, crickets and katydids which belong to the
same insect order as the grasshoppers, and also by the beetles,
the dragon-flies, the white ants, and various other less familiar
insects. All such insects bite off and chew more or less solid
substances.

Mouth -parts of Cicadas, Squash-bugs, etc. Cicadas,
squash-bugs, bedbugs, and many other sap-sucking and blood-

FIG. 61. Head and prothorax of water-bug, Scrphus d Hat at us. Show-
ing the piercing beak and the first pair of legs which are fitted for grasping.
(About natural size.)

sucking insects that belong in the same order with them
have a slender, sharp-pointed, more or less firm piercing beak
which is composed of a tubular sheath inside of which are
four sharp needle-like pieces which can project out of the
end of the sheath and be worked back and forth so as to
lacerate plant or animal tissue and thus cause a flow of sap or
blood which i,s sucked up the sheath into the mouth. The

10

146 ECONOMIC ZOOLOGY AND ENTOMOLOGY

four piercing stylets are the greatly modified mandibles and
maxillae, and the tubular sheath, which has a narrow longi-
tudinal slit along its upper side, is the much modified labium.
The labrum is reduced to a very small triangular piece at the
base of the sheath, and the maxillary palpi are wanting.
The labial palpi are also wanting, or are sometimes present
as two small feelers rising from the base of the labial sheath.

Insects with this type of mouth-
parts have muscles running from
the top of the pharynx or throat
cavity to the top of the head
which, when contracted, expand
the pharynx and make a pump-
ing or sucking organ of it.

Mouth-parts of Mosquito.
The piercing and sucking beak
of the mosquito is made up in
much the same way as that of
the squash bug and cicada.
That is, there is a tubular
sheath, narrowly open from
base to tip along the middle
of its upper side, in which lie
a number of sharp, slender
stylets, which can project be-
yond the edge of the sheath
and pierce or lacerate plant
tissue or the skin of animals.

The sheath is the much modified under lip or labium, while
the needles are the modified mandibles and maxillae and
two additional ones called labrum-epi pharynx and hypopharynx.
That is, they are outgrowths from the upper and lower walls of
the mouth or throat (pharynx). Thus the mosquito has six
piercing needles held together in its beak, instead of four as
with the cicada and squash-bug and their allies. Or rather
this is true only of the female mosquito, for the male mosquito
lacks two of the stylets, probably the mandibles, and never, or
but rarely, pierces the skin of animals to suck blood. There is

FIG. 62. Mouth-parts of a
female mosquito, Cnlcx sp. Icp.,
Labrum-epipharynx; md., man-
dible; mx.l., maxillary lobe;
mx.p., maxillary palpus; hyp.,
hypopharynx; //., labium; gl.,
glossa; pg., paraglossa.

SLIME SLUGS, MYRIAPODS AND INSECTS 147

also a pair of maxillary palpi, as long as the beak in both males
and females of some mosquitoes, but shorter in the females of
most species.

Mouth -parts of House-fly. -The mosquitoes belong to the
order of two-winged flies, but their mouth-parts cannot be
taken as typical of the order. A house-fly, for example,
has a mouth very different in make-up. The labium is a
fleshy proboscis expanded at the tip to form a special lapping
and rasping organ, and there are no mandibles or maxillae,
at least in functional condition. There is one pair of short

FIG. 63. Mouth-parts of the house-fly, Musca domestica. lb., Labrum;
mx. p., maxillary palpi; //., labium; la., labellum.

palpi which are usually called the maxillary palpi, although
they may really belong to the labium. The house-fly takes
up food either by lapping liquids with the broad tongue-like
end of its proboscis, or by rasping off bits of solid food, pouring
out saliva over them and then lapping them up as a fluid
mixture. The end of the proboscis, which is called the labellum,
is very elaborately contrived and furnished with ridges for
rasping and special muscles for folding and unfolding.

Mouth-parts of Butterflies and Moths. The sucking tube
of the butterfly or moth is still another very different type of
mouth. There is no labrum, mandibles nor labium, or only
rudiments of them. But the maxillae are developed into a
pair of long, slender, coiling pieces or processes which can be
held together in such a way as to form by means of their
grooved inner faces a perfect tube, long, slender and flexible.
With this tube they suck out nectar from the nectaries

148 ECONOMIC ZOOLOGY AND ENTOMOLOGY

of flowers or drink water from little
pools or damp places. They take no
other food. There is a pair of tufted
maxillary palpi which rise from each
side of the base of the sucking tube
and between which the tube, when not
in use, is compactly coiled.

Some moths and butterflies have
their mouth-parts wholly atrophied
and take no food in their adult condi-
tion. This is true also of numerous
insects of various kinds. Such kinds
of insects usually live but a short time
in adult condition, and use up during
this short time the fat stored in the
body during the immature life. The
moths and butterflies, for example,
are extremely voracious feeders in their
young or caterpillar stages. At this
time, too, they have mouth-parts of
very different type from
those possessed in adult
life. A caterpillar's
mouth-parts are of bit-
ing type with strong
cutting and crushing
mandibles and the food
is the tissues of plant
leaves and stems. Thus
it is important in the
study of insect mouth-
parts to recognize that
they may be very differ-

~ ent in the same insect

ric. 04. Sphinx moth, showing pro-

boscis. At left the proboscis is shown at different times of its
coiled up on the underside of the head, the life, and that, therefore,
normal position when not in use. (Large f i j T ,: nr : p c rqil = P H hv
figure natural size; small figure twice natu-
ral size.) an insect, and the rem-

SLIME SLUGS, MYRIAPODS AND INSECTS 149

edies for these injuries, may be very different in different
stages of the insect's life.

DEVELOPMENT AND METAMORPHOSIS

Although moths and butterflies are hatched from the egg in
a condition extraordinarily different in appearance from that
which they finally assume, not all insects undergo so great a
metamorphosis during their development. For example, a
just-hatched grasshopper is unmistakably grasshopper-like in

FIG. 65. Metamorphosis, incomplete, of an assassin-bug (family
Red iivi idee, order Hcmlptcra}. A, Young just hatching from eggs; B,
young after first molting, showing beginning wing-pads; C, older stage
with larger wing-pads; D, adult with fully developed wings. (% larger
than natural size.)

appearance, although it has no wings and the proportions of
the different parts of its body are somewhat different from those
of its parents. The young grasshopper has three pairs of legs,
has a head with antennae, compound eyes and biting mouth-
parts like those of its parent, walks and hops about, feeding
on green plants, and altogether looking and acting much as
fully developed grasshoppers do, except that it has no wings
and hence cannot fly. As it grows, however, wings begin to
appear as tiny bud-like expansions on the back of the two

150 ECONOMIC ZOOLOGY AND ENTOMOLOGY

hinder thoracic segments. These wing-buds rapidly increase
in length, and by the time the developing grasshopper has come
to its adult size the wings are also full size and ready for use.

During this growth and development of the young grasshop-
per, which requires several weeks for its completion, it molts
several times. This molting is the shedding of the chitinized
cuticle which covers the body. Before each molting takes
place, however, the skin cells have secreted a soft and colorless
new chitinized cuticle which, as soon as the outer old one is cast
off, becomes firm and colored, and takes its place. The young
grasshopper shows most of its changes in size and appearance
just after each molting. The wing-buds hardly seem to grow
between molting periods, but after each molting they may be
seen to be larger and more developed.

Insects whose development is, in general, like that of the
grasshopper, that is, those which hatch from the egg in a
condition more or less resembling the parent except for size
and total absence of wings, are said to undergo a development
without metamorphosis or with incomplete metamorphosis.
While insects which, like the moths and butterflies, hatch from
the egg in a stage very different in appearance from that of the
parent, and in their development have to undergo extraordi-
nary changes in appearance and structural make-up to become
like the parent, are said to develop with metamorphosis, or
with complete metamorphosis.

In insects with complete metamorphosis there is a curious
stage called the pupal or chrysalid stage which is interpolated
between the first or larval stage, which is that in which the
insect hatches, and the final or adult stage, the stage in which
the insect is sometimes called an imago. After the young
caterpillar has undergone a certain period of rapid growth and
increase of size, during which period it molts several times
but does not show any external changes making it any more
like its parent than it was at the beginning, it stops feeding
and changes into an inactive, non-feeding stage with its body
inclosed in a thick, firm, chitinized covering which is neither of
the shape of the larva nor of the imago. This is the so-called
pupal stage, and the insect in this condition is called a pupa.

SLIME SLUGS, MYRIAPODS AND INSECTS 151

It is in this stage that most of the radical changes in structure
are undergone which are necessary to make the moth or
butterfly out of the caterpillar, the house-fly out of the maggot,
or the beetle out of the grub.

However, most of these changes have their beginnings during
the larval stage. For example, little wing buds have been
developing all through the larval life, but they have remained
very small and invisible underneath the chitinized cuticle of the
larva. Especially in the last few days of the larval stage are the
various changes going on rapidly. But they are so radical in

FIG. 66. Metamorphosis, complete, of Monarch butterfly, Anosia
plcxippns. a, Egg (greatly magnified); b, caterpillar or larva; c, chrys-
alid or pupa; d, adult or imago. (| natural size; after Jordan and
Kellogg.)

character that it is impossible for the insect to maintain an
active food-getting life and make the changes at the same time.
Hence comes the necessity for the quiescent pupal stage in
which the insect, living on food stored up as fat by the larva,
and safely inclosed in a hard protecting shell, can make the
great changes necessary to its becoming a fully developed
winged imago, different as to mouth-parts, eyes and antennae,
different as to body shape, different as to legs and abdominal
appendages, and, together with all these structural differences,
radically different as to habits and behavior. Many of the

152 ECONOMIC ZOOLOGY AND ENTOMOLOGY

internal systems of organs undergo as radical changes as the
external parts. Muscles, salivary glands, parts of the alimen-
tary canal, etc., of the larva break down and are used as food by
new growth centers which develop into new muscles, new
salivary glands and other new internal parts. This internal
degeneration of larval parts and rebuilding of imaginal parts are
called histolysis and histogenesis, and form a fascinating subject
of study, which requires, however, a training in histologic
methods of technique beyond that of the elementary student.
In the next chapter, which is devoted to the classification of
insects, we shall point out the character of the metamorphosis
and some of the special features of development presented by
each of the different insect orders.

CHAPTER XVII

THE CLASSIFICATION OF INSECTS, AND INSECT
BENEFITS AND INJURIES

Linnaeus, the first great classifier of animals, divided the
insects into seven orders based on the character of the wings.
In the order Aptera, or wingless insects, he placed all insects
lacking wings. But now we know that there are wingless
moths, wingless beetles, wingless flies, and so on, and that
these different kinds of insects ought not to be classified to-
gether simply because through degeneration from one cause
or another they have lost their wings.

The two-winged insects with balancers in place of the hind
wings Linnaeus called Diptera, and this order still stands about
as he established it. All the four-winged insects with mem-
branous wings he placed in two orders, those having stings in
the Hymenoptera and those without stings in the Neuroptera.
Insects with their wings covered with scales he called Lepi-
doptera, and insects with their fore wings thickened he called
Coleoptera if the wings were thickened for their whole length,
and Hemiptera if their wings were thickened only over the
basal half.

Although now different criteria are used as a basis for insect
classification and the class Insecta is divided into more than
seven orders, Linnaeus's seven ordinal names are still used, and
the insects indicated by each of them are largely also charac-
terized by the condition of wings indicated by the names. But
out of the Linnaean orders Aptera and Neuroptera, nine dif-
ferent new orders, beside the two still bearing the same
names, have been made. And three other new orders have
been made for insects taken from the Hemiptera and the
Coleoptera. In all we now recognize nineteen orders in the
class Insecta. This, at least, is the American practice. Most

153

i54 ECONOMIC ZOOLOGY AND ENTOMOLOGY

English and Continental entomologists do not recognize so
many different orders.

The two principal criteria used in the modern classification
of insects are the structure of the mouth-parts and the char-
acter of the development. Of these, the development condi-
tion is held to be the more fundamental, although this may be
open to question. However, on a primary basis of develop-
ment and mouth-part conditions, combined with character
of wings, antennae, and to a less extent, of legs and abdominal
appendages, insects are now classified into orders in the
following way:

Metamorphosis very slight; biting mouth-parts;

wingless APTERA

Metamorphosis incomplete.
With biting mouth-parts.

EPHEMERIDA
PLECOPTERA

Wings membranous.

ODONATA

ISOPTERA
CORRODENTIA
Fore wings parchment-like ............... / ORTHOPTERA

I EUPLEXOPTERA

Wingless ............................... MALLOPHAGA

With sucking mouth-parts ................. ( HEMIPTERA

I THYSANOPTERA
Metamorphosis complete.

U7-.1- u-4.- f NEUROPTERA

With biting mouth-parts. MECOPTERA

With wings membranous ................. \ TRICHOPTERA

With fore wings thickened ............... COLEOPTERA

With sucking mouth-parts ................. LEPIDOPTERA

With lapping or piercing and sucking mouth-
parts " ................... I HYMENOPTERA

Order Aptera. The Aptera undoubtedly include the most
primitive of living insects. This primitiveness is shown not
alone by the absence of wings, which is the characteristic which
gives the order its name, but is manifest also in the very
simple and generalized condition of most of the body parts,
internal as well as external.

All the insects of the order are small, but a group of them

THE CLASSIFICATION OF INSECTS

155

known as the spring-tails, or Collembola, are very small indeed,
most of them measuring only two or three millimeters in length.
These Collembola are more specialized in structure than the
other Aptera, and represent a side line of evolutionary de-
velopment within the order. Most of them possess a curious
forked spring on the under side of the body by means of
which they leap vigorougly when disturbed. But few of
these minute insects are injurious, although at least one spe-
cies, called the garden-flea, S my nt hunts hortensis, is sometimes
found in considerable numbers
upon the leaves of young cab-
bages, turnips, cucumbers and
various other plants, on which
it probably feeds. Certain
other species are reputed to
exist in such abundance in the
soil of flower and vegetable

FIG. 67. The spotted spring-
tail, Papirius maculosus, with
spring extended. (Natural size,
two millimeters.)

FIG. 68. Young and adult Lc-
pisma sp. from California. (Twice
natural size.)

beds as to keep the soil so constantly disturbed by their
movements that the roots cannot hold the plants firmly.

The other principal group in the order, known as the Thy-
sanura, is represented in this country by three small families
which contain but a few species. All the Thysamira have a soft
flattened body of from but a few millimeters to three-fourths
of an inch in length, and live mostly under stones and logs in
the soft soil and humus at the bases of tree trunks. A common
species that occurs in houses is known as the silver-fish, or
fish-moth, Lepisma saccharina. It is about one-half an inch
long and silvery white with a yellowish tinge. It feeds

156 ECONOMIC ZOOLOGY AND ENTOMOLOGY

chiefly on sweet or starchy materials, sometimes doing real
damage in libraries, where it attacks the book bindings. It
attacks starched clothing, eats the paste off the wall-paper,
causing it to loosen, and infests dry starchy foods. It runs
swiftly and avoids the light. It can be killed by spreading

pyrethrum powder in book cases,
wardrobes and pantries. Another
species, called the bake-house sil-
ver fish, Lepisma domestica, is often
common about fire places and
ovens, running over the hot metal
and bricks with surprising immu-
nity from the effects of the heat.

All of the Aptera when hatched
from the egg very much resemble,
except in the matter of size, the
parent form. And they reach the
adult condition with very little
change except that of a marked
growth in size.

Order Ephemerida. The Ephe-
merida or May-flies, or lake-flies,
are a small order of delicate four-
winged insects which live in adult
condition for from but a few hours
to a few days, varying with different
species. They have soft, poorly
developed mouth-parts of biting
type, or no mouth-parts at all, and
probably only a few kinds take any

food as adults. The wings are very thin and many veined,
with the hind wings smaller than the fore wings, or even
wholly lost in a few species.

The eggs are dropped into the water of ponds or quiet stream
pools, and the young which hatch from them are soft-bodied
flat creatures, called nymphs, which crawl about on the bottom,
often on the undersides of stones. They have well-developed
biting mouth-parts with sharp-pointed mandibles. They

FIG. 69. Young (nymph)
of May-fly, showing (g) tra-
cheal gills. (Three times
natural size; after Jenkins
and Kellogg.)

THE CLASSIFICATION OF INSECTS

157

breathe by means of delicate leaf-like tracheal gills on the sides
of the abdomen, and when ready to change into adult condition,
crawl up out of the water onto the bank or plant stems or float
to the surface, and there quickly cast the nymphal cuticle and
issue as winged imago. Some species molt again after having
used their wings a little while.

The May-flies often issue from rivers or lakes in enormous
numbers in the summer, and form an annoying plague to
house-boat dwellers or summer cottagers simply by their too
abundant presence. Their dead bodies falling on the surface
of the water are sometimes driven by
the wind on the shore in great windrows.

Order Plecoptera. 'The Plecoptera,
or stone-flies, are unfamiliar insects
which, like the May-flies, hatch from
eggs dropped into the water, and live
an immature life of several months as
flattened wingless nymphs crawling
about at the bottom. Indeed, the
stone-fly nymphs often live side by side
with the young May-flies, but can usu-
ally be distinguished from them by be-
ing thicker and broader, and having
tracheal gills not leaf-like but composed
of separate filaments or tufts of such FIG. 70. Young

filaments rising from the thoracic seg- to"^).. of . sto " e - f ?>''

from California. (Twice

ments, one tuft just behind each leg. natural size.)

They cannot live in stagnant water or

foul streams. When ready to change to the winged adult

condition the nymphs crawl out from the water, the cuticle

splits along the back, and the winged fly issues.

The adult flies have four rather large, membranous, many-
veined wings, the hind ones being larger than the front ones.
The mouth-parts are well developed and fitted for biting, but
the food habits are not known. About 100 species occur in
North America, among which there is none injurious to man.
The young of many kinds furnish food for many fishes.
And this is true also of the May-flies.

158 ECONOMIC ZOOLOGY AND ENTOMOLOGY

Order Odonata. -The Odonata are the familar dragon-flies,
devil's darning-needles, and damsel-flies, that swoop about over
ponds and quiet streams, capturing small flying insects. The
body is long and slender, and the four wings are membranous,
many-veined, and all about equal in size. They live largely
on the wing and are among the most rapid and powerful insect
fliers. The legs are slender and weak, and chiefly used to hold
captured prey up to the mouth and for perching. Like the
May-flies and stone-flies, their young stages are spent in water
as wingless, crawling nymphs. Here also they capture smaller

FIG. 71. Adult and last exuvia of the white-tail dragon-fly, Plathemis

trimaculata. (Natural size.)

living insects, not however by speedy pursuit but by lying in
wait and seizing any unwary prey that may come within reach
of the curious extensile under lip which is provided with sharply
toothed, jaw-like pincers.

About 300 species of Odonata are known in North America,
and 2000 in all the world. All of them have beautifully
colored bodies, and many have the wings strongly patterned
by conspicuous brown blotches and bands. None of them is
injurious to man, but almost all may be considered as beneficial,
because they are all destroyers of noxious insects. It is

THE CLASSIFICATION OF INSECTS

probable that dragon-flies are the most efficient natural remedy
for mosquitoes. As nymphs they destroy many mosquitoes
in their young or "wriggler" stage, while as adults they capture
hosts of flying mosquitoes.

FIG. 72. Young (nymph) of a dragon-fly, Sympetrum illotum. Showing
the lower lip extended. (Natural size.)

Order Isoptera. -The order Isoptera, termites, or so-called
white ants (although not related to the true ants) comprises less
than ten species in North America, but is much better repre-
sented in subtropical and tropical regions. In equatorial
Africa and South America, for example, the termites are very
important insects both because of their numbers and because
of their habits. They have strong biting mouth-parts, and
they feed chiefly upon dead wood. By virtue of this habit
they may be of considerable benefit as scavengers, or of con-
siderable harm by destroying wooden poles, furniture, etc.
They live in large communities, usually making their nests
underground or in "houses" built of soil brought up labori-
ously grain by grain and fastened together so as to produce
earthen structures rising like tents or pinnacles for several
feet above the surface of the ground.

The communities comprise kings and queens (males and
females) provided with four nearly equal, delicate, membranous

160 ECONOMIC ZOOLOGY AND ENTOMOLOGY

wings, wingless workers, and wingless soldiers. The soldiers
have greatly enlarged mandibles which are used in fighting
enemies. The workers are smaller than soldiers or kings and
queens, but exist in larger numbers and get the food and build
the nest for the whole community. After a marriage flight
the queens find hiding places in the ground, break off their
wings, and each lays a few eggs from which begins a new
community. The young are all alike when first hatched, and
only workers or soldiers develop from the first eggs. Later

FIG. 73. Termite queen, worker and soldier. (Natural size.)

eggs give birth to young which develop wing buds and after
several meltings become fully formed winged individuals.

Only one species, Termes flavipes, is found in the eastern
states. Its workers are about 1/5 of an inch long, white
and soft-bodied. The soldiers are a little larger, and the
winged males and females, which go from the nest and swarm
in the air in late spring or late summer, are chestnut brown to
blackish and but little longer than the workers. This species
usually makes its nest in or under old logs or stumps. It
sometimes does damage by mining the foundation timbers

THE CLASSIFICATION OF INSECTS

161

of houses, and in the southeastern states they have been found
infesting living plants, particularly orange trees, guava bushes,
sugar cane and pampas grass. The largest and most abundant
species, Termopsis augusticollis, on the Pacific coast, makes its
nest by mining in dead stumps and logs and sometimes ruins
telephone and telegraph poles in this way. A single com-
munity of this species may include thousands of individuals.

Order Corrodentia. -The order Corrodentia, or book-lice
and bark-lice, is composed of very small insects most of which,
composing the family Psocida, have two pairs of wings and a
plump rounded body, while the others,
forming the family Atropida, have no
wings or only small wing scales or buds
and a flattened body. The Psocidae
are the bark-lice and are commonly
found in small clusters on bark, while
the Atropidse are the so-called book-
lice, common in old books and on dry
dead organic matter.

In both families the mouth-parts are
of the biting type, with the jaws especi-
ally strong and heavy for the success-
ful biting off and chewing of hard dried
food. Atropos divifiatoria is the spe-
cies usually found in books. It is
about 1/25 of an inch long, grayish-
white, with slender projecting antennae, and small eyes look-
ing like distinct black spots on the head. It does not limit
its feeding to the paste of book bindings but does much dam-
age to dried insects in collections.

Order Mallophaga. The Mallophaga, or biting bird-lice,
compose a group of about 1500 known species, all of which
live as external parasites on the bodies of birds and mammals.
They have strong biting mouth-parts, and feed exclusively on
the hairs or feathers of their host. They do not, like the true
lice, suck blood.

The body varies from 1/25 to 1/3 of an inch long, is wholly
wingless and much flattened. The insects have no compound

FIG. 74. A wingless
book-louse, Atropos sp.
(Much enlarged.)

ii

162 ECONOMIC ZOOLOGY AND ENTOMOLOGY

eyes, and in this and their winglessness show the degeneration
which a parasitic life almost always produces. The eggs are
fastened to the hairs or feathers, and the young undergo little
change during their development except an increase in size to
become like the parents.

Almost every species of bird or mammal is infested by one
or more kinds of Mallophaga, and some-
times the host must suffer much annoy-
ance and even injury from the irritation
produced by its many small parasites.
All of the common barnyard birds are
troubled more or less by these biting lice,
and their presence may become a serious
matter in hen-houses. An account of cer-
tain special Mallophagan pests and of
remedies for them is given in Chapter
XXXVII.

Order Orthoptera. The order Ortho-
ptera is much larger than any of the other
orders so far considered, and includes
many familiar insects, such as the grass-
hoppers, katydids, crickets, cockroaches
and praying mantises. The order is di-
vided into six families, of which three in-
clude all the well-known singing insects,

FlG - A. biting except the cicada or harvest flies. The

louse of pigeons, Lip- insects in these three singing families are

earns baculus (Na- a i so t h e best known leaping insects, the

tural size indicated , . , . , . . ,, ,

by line.) hind legs being especially long and strong,

so that when the insect is at rest the
"knee joints" of these legs stand up conspicuously above the
body.

All the Orthoptera have strong biting mouth-parts and nip
off and chew their food, which is usually green leaves and stems.
The mantises (family Mantidcs) are, however, predaceous,
preying on other insects, and the cockroaches (family Blattidice}
prefer dried vegetable or animal matter. The metamorphosis
is incomplete, and the young, which resemble the parents

THE CLASSIFICATION OF INSECTS 163

except in size and the absence of wings, have the same feeding
habits and the same haunts as the adults. The name of the
order is derived from the straight-margined parchment-like
fore wings (orthos, straight, and ptera, wings) which are chiefly
used as covers to protect the large membranous hind wings on
which the flight function depends. There are numerous wing-
less species in the order, and some with degenerate short wings
incapable of flight.

The "music" which is made by the male crickets, katydids
and meadow-grasshoppers, is produced by the rubbing to-
gether of the bases of the f ore wings in which certain veins
are thickened and roughened so as to make effective stridulat-

1- * .-?*'"'" .

*

FIG. 76. The American locust, Schistocerca americana. (Natural size.)

ing organs. Grasshoppers make sounds when at rest by
rasping the inner surface of the broad hind legs across the
outer surface of the folded fore wings, and while in flight many
of them make a loud clacking sound by striking the front
margin of the hind wings back and forth past the hinder
margin of the thickened fore wings.

Despite the beneficial feeding habits of the insect-preying
mantises, the Orthoptera as a whole must be looked on as a
seriously injurious group of insects. Cockroaches are great
pests in houses, while crickets and especially grasshoppers
work much injury to field crops. The notorious Rocky Moun-

164 ECONOMIC ZOOLOGY AND ENTOMOLOGY

tain Locust, Melanoplus spretus, which used to appear
occasionally in countless numbers in the grain fields of the
Mississippi valley, travelling a thousand miles by a single flight
from the Rocky Mountain plateau, is no longer such a danger,
but there are many other non-migratory species of grass-
hoppers which constantly attack the field crops. Some of
these injurious Orthoptera are referred to in Chapter XXXVI
and remedies for their attacks described.

Order Euplexoptera. The Euplexoptera, or earwigs, com-
prise a small number of insects which were formerly included
in the Orthoptera. They are small brownish or blackish insects
readily recognized by the curious forcep-like appendages on
the tip of the abdomen. They are either winged or wingless,
and when winged have small thickened wing-covers extending
only about half way to the tip of the abdomen with the well-
developed, nearly hemispherical hind wings compactly folded
underneath them. Earwigs are nocturnal in habit, and feed
by means of their biting mouth-parts on ripe fruit, flowers
and other vegetable food. Despite the name they have
nothing to do with ears. The young undergo an incomplete
metamorphosis, and closely resemble the parents, except in
size, from the time of their hatching.

Order Hemiptera. The Hemiptera, or sucking bugs,
cicadas, aphids, scale-insects, etc., compose a large order which
includes over 5000 species in North America, representing a
large variety of insect life. Many of them are of great econo-
mic importance. Some of the most destructive crop pests and
most discomforting insect scourges of man and the domestic
animals belong to this order. The chinch-bug of the corn and
wheat fields of the Mississippi valley, the tiny sap-sucking
aphids or plant-lice and phylloxera, and the insignificant-
looking scale-insects cause annual losses of millions of dollars
to American fields, orchards and vineyards.

The mouth-parts in all the Hemiptera. are arranged to form
a piercing and sucking beak capable of taking only liquid
food. This food is usually the sap of living plants or the blood
of living animals. The wings are typically four in number,
although some species have but two wings and others none.

THE CLASSIFICATION OF INSECTS

165

The Hcmiptera have an incomplete metamorphosis, the young
at birth resembling the parents in most essential characteristics
except size and the presence of wings.

The order is sub-divided into three sub-orders, one, the
Parasita, composed of wingless species living as parasites on
man and other mammals; another, the Honwptcra, winged
species with fore and hind wings of the same texture through-
out and usually held sloping or roof-like over the back; and

FlG. 77. A water-bug, Scrphus dilatatus. (Natural size.)

another, the Heteroptera, with four wings held flat on the back
when folded and with the bases of the front wings thickened,
hence the name of the order (hemi- } half, ptera, wings). The
Parasita include the sucking lice; the Heteroptera the squash-
bugs, chinch bugs, w r ater-boatmen, assassin-bugs and stink-
bugs; while the Homo ptera include the cicada or harvest-flies,
the tree- and leaf-hoppers, the aphids, or plant-lice and the
degenerate scale-insects. Some of the more injurious species
of this order are described in Chapters XXX to XXXVII.

166 ECONOMIC ZOOLOGY AND ENTOMOLOGY

Order Thysanoptera. The curious little insects known as
thrips, or fringe-wings, which used to be classified with the
Hemiptera, are now given the standing of an independent
small order. This is due to the peculiar character of their
mouth-parts and feet, and to the interesting nature of their
development, which is apparently of a sort of transitional con-
dition between incomplete and complete metamorphosis. The
food of the thrips is either the sap of living plants or moist
decaying vegetable matter, especialy wood and fungi. The
mouth is of sucking type with needle-like mandibles and
maxillae to pierce plant tissue, but it is curiously asymmetrical,
the right mandible being wholly wanting and the upper lip
being more expanded on one side than the other. The feet
have a small protrusible membranous sac or bladder at the
tips instead of fixed claws or pad. These tiny sacs probably
fill some special role in enabling the thrips to hold on to leaves
or flower surfaces.

While most of the thrips species live on wild plants, a few
infest fruits, grains and vegetables, and do much injury.
Among these are the onion thrips, wheat thrips, grass thrips,
orange thrips and pear thrips. This last pest appeared
suddenly in California a few years ago, and since then has
caused the loss of millions of dollars worth of prunes, apricots
and other deciduous fruits. Several of the thrips are described
in the later special chapters on injurious insects.

Order Neuroptera. The Neuroptera, constituting a small
order in point of numbers, are insects with biting mouth-parts,
and a metamorphosis usually called complete, but in which the
larval stage resembles somewhat the adult stage, and the pupal
stage is not usually undergone as a wholly immobile chrysalid,
but more often in a condition which suggests that of an inac-
tive larva with conspicuous external wing-pads. This stage
is usualy passed in a special cell or cocoon made by the larva
when full grown. The adults have four membranous, many-
veined or so-called "nerve-veined" wings, hence the name of
the order (neuron, nerve, ptera, wings). The Neuroptera
include seven families of mostly unfamiliar insects, some very
large, and others extremely small. The immature stages of

THE CLASSIFICATION OF INSECTS

167

one family, the Sialida, of which the large dobson-fly or hell-
grammite is the best known species, are passed in the water of
streams or ponds, but the members of all the other families
are terrestrial through all their life. Of these the ant-lions,
whose larvae make small pits in loose soil in which to catch
prey, and the aphis-lions, lace-winged flies and snake-flies,
whose sharp-jawed larvae feed on such small defenseless in-
sects as aphids and codling moth larvae, are more or less famil-
iar and may be counted as beneficial insects. There are no
seriously injurious insects in the order.

' :

FIG. 78. Pit of ant-lion, and, in lower right-hand corner, pupal sand-
cocoon, from which adult has issued, of ant-lion, Mynnclcon sp.
(About natural size.)

Order Mecoptera. The order Mecoptera includes a few
little-known insects called snow-fleas and scorpion-flies. The
mouth-parts are of biting type, and are elongated to form a sort
of short, blunt beak. The metamorphosis is complete. Most
of these insects are probably predaceous in habit, feeding on
other small insects, and thus perhaps doing good, but some
take only animal food found dead. The curious snow-fleas,
Boreus, are minute, black, leaping creatures that appear on
snow in winter time, and in summer live on tree trunks or in

168 ECONOMIC ZOOLOGY AND ENTOMOLOGY

moss. The scorpion-flies have four, rather long, slender, mem-
branous wings with numerous veins, and long angular legs,
with which they scramble awkwardly about among green or
drying grass leaves.

Order Trichoptera. The Trickoptera, or caddis-flies, com-
pose a small homogeneous order of four-winged insects many
of which look much like moths. In fact, there is little doubt
that this order may be looked on either as the direct ancestors
of the moths and butterflies or as a group descended from such
ancestors. The wings are membranous, but obscurely colored
by a covering of hairs and narrow scales; the antennae are long
and slender, and the legs delicate and unmodified. The in-
sects limit their flight to short, uncertain excursions along the
shore of the stream, and spend long hours in the close foliage
of the bank. So far as observed they take no food, although
they have fairly well-developed mouth-parts fitted, apparently,
for lapping up liquids.

The eggs are dropped into water and the aquatic larvae
build protecting cases (hence the name, case- or caddis-flies)
of little pebbles, sand, or bits of wood fastened together by
silken threads. Some of the cases can be carried about by the
larva in its ramblings, but others are fastened to the boulders
or rock-beds of the stream. The larvae are caterpillar-like,
with head and thorax that project from the case, usually
brown and firm-walled, while the abdomen is soft and whitish.
They breathe by means of thread-like tracheal gills, and feed
on bits of vegetable matter and probably other small aquatic
creatures. Some have the interesting habit of spinning a tiny
silken net stretched in such a way that its broad shallow mouth
is directed up-stream so that the current may bring food into
it. When the caddis-worm is ready to pupate it withdraws
wholly into the case and closes the opening with a loose wall of
stones or chips and silk. When ready to issue the pupa usu-
ally comes out from the submerged case, crawls up to some
support above the water, and there the winged imago emerges.
Some kinds, however, emerge in the water.

About 500 species of caddis-flies are known of which 150

THE CLASSIFICATION OF INSECTS

169

occur in North America. None of them is injurious. The
larvse of many species are eaten by fish.

Order Coleoptera. The great order of Coleoptera, or bee-
tles, is the largest of all the insect groups, and many of its
members are among the most familiar of our insect friends and
enemies. More than 12,000 species are known in North
America north of Mexico. They represent nearly 2000 genera
grouped into 80 families. The classification of the Coleoptera

is one of the most difficult subjects in the
study of systematic entomology, and but
few entomologists know more than a few
score or few hundred of the commoner
kinds. The beetles are mostly readily dis-
tinguished by their horny fore wings, or
elytra, which serve as protecting covers for

FIG. 7 Q . Water-
tiger, the larva of the
predaceous water-bee-
tle, Dyticifa sp. (Nat-
ural size.)

FIG. 80. The predaceous water-beetle, Dy-
tlcus sp. pupa and adult. (Natural size.)

the large membranous hind wings. They all have strong bit-
ing mouth-parts and a firm dark chitinized cuticle or outer
body-wall. The body is usually short and robust with its
segments well fused together. There is much variety in the
character of the antennae and feet, and these differences are
largely relied on in classifying beetles into different families.
The eggs are laid underground, or on leaves or twigs or in
branches or trunks of live trees, in fallen logs or in decaying

170 ECONOMIC ZOOLOGY AND ENTOMOLOGY

matter, in fresh water, etc., and from them hatch larvae, usually
called grubs, with three pairs of legs (sometimes wanting),
biting mouth-parts, simple eyes and small antennae. These
larvae may be predaceous, as water-tigers (larvae of water-
beetles), or plant feeders, as the larvae of the long-horn and
leaf-beetles, or carrion feeders, as those of the burying beetles
and so on. They grow, molt several times, and finally change
into a pupa either on or in the food, or very often in a rough
cell underground. From the pupa issues the fully developed
winged beetle, which usually has the same food habits as the
larva.

The economic status of the order Coleoptera is an important
one. So many of the beetles are plant feeders and are such
voracious eaters in both larval and adult stages that the order
must be held to be one of the most destructive in the insect
class. Such injurious pests as the Colorado potato-beetle, the
round-headed and flat-headed appletree borers, the wire-worms
(larvae of click-beetles), the white grubs of meadows and lawns
(larvae of June-beetles), the rose-chafers, flea-beetles, bark-
borers, and fruit and grain weevils are assuredly enough to
give the beetles a bad name. But there are good beetles as
well as bad ones. The little lady-bird beetles eat unnumbered
hosts of plant-lice and scale-insects, the carrion-beetles are
active scavengers, and the members of the predaceous families,
as the Carabids and tiger-beetles, undoubtedly kill many noxi-
ous insects by their general insect-feeding habits. In the later
chapters on injurious insects (XXX to XXXVII) many kinds
of beetle pests will be described.

Order Diptera. The Diptera, or two-winged flies, consti-
tute another large order of insects, which are characterized,
first of all, by their possession of but one pair of wings, those
of the meso-thoracic segment, the hinder pair being transformed
into two short, slender, knob-ended structures called balancers.
These have a special nervous equipment, and have been shown
by experiment to have some control of the equilibrium of the
fly when in flight. The two wings are membranous, usually
clear and supported by a few strong veins. The mouth-parts
show much variety, and although no flies can bite in the sense

THE CLASSIFICATION OF INSECTS

171

of the chewing and crushing biting common to beetles, grass-
hoppers and other insects with jaw-like mandibles, some, as
the mosquito, have elongate mandibles, slender and sharp-
pointed, so that they act as lacerating needles to make punc-
tures in the flesh of animals or tissues of plants. Most flies,
however, have no piercing beak, but, like the house-fly, lap up
liquid food with a curious folding fleshy proboscis which is the
highly modified labium or under lip. They feed on flower
nectar or any exposed sweetish liquid, or on the juices of
decaying animal or plant substances.

FIG. 81 Horse-fly, Tabanus punctifcr. (About i| natural size.)

All the Diptera have a complete metamorphosis, the young
hatching from the eggs as footless and even headless larvae
(maggots, grubs), usually soft and white, and in many cases
taking food osmotically through the skin. Larvae of different
kinds of flies live under a great variety of conditions; some in
water, some in the soft tissue of living plants or decaying
fungi, some in the flesh of live animals or in carrion, some
underground, feeding on plant roots.

The pupae of the more specialized flies are concealed in the
thickened and darkened last larval molt, the whole puparium or
chrysalid looking much like an elliptical brown seed. In some

172 ECONOMIC ZOOLOGY AND ENTOMOLOGY

of the flies, however, as in the mosquito and other midges, the
pupal stage is an active one although no food is taken during
it. The life history is usually rapid so that generation after
generation succeeds one another quickly. Thus it may be
true, as an old proverb says, that a single pair of flesh-flies
(and their progeny) will consume the carcass of an ox more
rapidly than a lion.

About 50,000 species of Diptera are known, of which about
7000 occur in North America. The order includes the familiar
house-flies, flesh-flies, and blue-bottles of the dwelling and
stables; the horse-flies and green-heads that make summer life
sometimes a burden for horses and cattle; the buzzing flower-
ancl bee-flies of the garden; the beautiful little pomace-flies
with their brilliant colors and mottled wings, that swarm
about the cider press and fallen and fermented fruit; the bot-
flies, those disgusting pests of horses, cattle, rabbits, rats,
etc.; the fierce robber-flies that prey on other insects, including
their own fly cousins; the midges that gather in dancing swarms
over pastures and streams; the black-flies and punkies, vexers
of trout fishers and campers, and worst of all, the cosmopolitan
mosquitoes, probably the most serious insect enemies of man-
kind. A number of the specially injurious kinds of flies are
described in Chapters XXVIII and XXX to XXXVII.

Order Siphonaptera. The fleas are blood-sucking parasites
of birds and mammals which were long classified as a family
(Pulicidce) of the Diptera, being looked on as wingless and
otherwise degenerate flies. They are now, however, given
the rank of an independent order. Nearly two hundred species
of fleas are known in the world, of which about fifty occur in
North America. Only a few species have been found on birds,
the others on mammals, both domesticated and wild.

The fleas are all wingless and have the body greatly flattened
laterally. The mouth-parts are composed of several sharp,
strong, piercing stylets and a pair of thicker grooved parts which
can be held together to form a sucking tube. While the adults
are more or less familiar the young are rarely seen. The larvae
are small, slender, white, footless, worm-like grubs which lie
hidden in cracks and crevices and live on dry organic detritus.

THE CLASSIFICATION OF INSECTS

17.3

They are especially common in dirty dwellings and in cat and
dog houses. With the common cat- and dog-flea the larval
life lasts only one or two weeks. When full grown the larva
usually spins a thin silken cocoon within which it pupates.
The adult flea issues in a few days after pupation. In a few
species, as the "chigoe" or "jigger" flea of the tropics, the
adults burrow into the skin of the host, lay eggs there and the
young may pass their development in a sort of tumor caused
by the burrowing adult. The hen-flea of the southern States
has the same habit of development. The rat-fleas have been

; - i

:>

I/*

FIG. 82. Human-flea, Pulcx irrilaiis; male.

proved to disseminate the germs of plague among rats (see
Chapter XXIX). The commonest fleas affecting man are
the human-flea, Pulex irritans, and the cat- and dog-flea,
Ctenocephalus canis. The best way to fight them is to keep
rooms and the places where cats and dogs sleep thoroughly
clean. Flea larvae will not develop successfully in places
where they are often disturbed, hence much sweeping and
scrubbing will keep them down. The adult fleas are very
resistant to insecticides.

174 ECONOMIC ZOOLOGY AND ENTOMOLOGY

Order Lepidoptera. Lepidoptera, or moths and butterflies,
are the insects most favored of collectors and nature lovers.
The beautiful color patterns, the graceful flight and dainty
flower-haunting habits and the interesting metamorphosis
during their development make them very attractive, while
the comparative ease with which the various species may be
determined and the large number of popular as well as more
technical books about them, make the moths and butterflies,
among all the insects, most collected and studied.

About 7000 species are known in North America, and except
for a few kinds with wingless females and a few other clear-
winged kinds which have a superficial likeness to wasps and
bees, all the species may be readily recognized as moths or
butterflies by the complete coating of tiny scales on the four
wings both above and below. It is on these scales that the
colors and patterns of the moths and butterflies depend. The
scales are very small, varying from 1/350 to 1/30 of an inch
in length and from the thickness of a fine hair to 1/60 of an
inch in breadth. They are arranged in more or less regular
rows, which overlap each other so that a shingle-like covering
over the wing is produced. On a large butterfly the total
number of scales on all the wings may number more than a
million. Each scale is really a tiny flattened membranous sac
with a short stem which is held in a little pit or pocket in the
wing membrane. All the scales are finely and regularly
striated from base to tip, and most of them contain a number
of small pigment granules. The colors are produced both
by the pigment and by the complicated reflections caused by
the striated and laminated structure of the scales. On the
latter condition depend the irridescent and metallic colors,
such as the changing blues and greens, while on the presence
of the pigment depend the fixed brown, reddish and yellow
colors. The wings themselves are large and membranous
and supported by a few strong veins. The fore wings are
longer and narrower in proportion to their length than the
hind wings, this condition being particularly emphasized
among the swift-flying species, such as the sphinx-moths.

The mouth-parts of all the Lepidoptera, except a few

THE CLASSIFICATION OF INSECTS 175

primitive species of moths, are extraordinarily modified so as
to form a long, slender, flexible, sucking tube, by means of which
flower nectar and water can be drunk. This tube is made of
the two elongated maxillae, grooved on their inner faces and
held, even locked, together to form a perfect tube. Upper lip,
mandibles, and under lip are either wholly wanting or reduced
to mere rudiments. Thus no adult moth nor butterfly can
seriously injure any plant or animal; but strongly contrasted
to this innocuousness of the adults are the serious capacities
for mischief of the larval or caterpillar stage.

From the eggs, which are almost always deposited on the
proper special food plant, hatch the well-known worm-like
larvae or caterpillars which are provided with strong biting
mouth-parts. They proceed at once to the serious business of
voracious eating. The young caterpillar may eat many times
its weight of leaf tissue in a single day, and where the cater-
pillars are abundant they may quickly defoliate whole shrubs
and trees. The caterpillars are provided with three pairs of
jointed thoracic legs and five pairs of fleshy un jointed abdominal
legs, and can migrate freely from plant to plant, thus increasing
their capacity for harm. When they are full grown they usu-
ally burrow into the ground, spin a silken cocoon, or seek some
hiding place in which to pupate. The pupa is enclosed in a
thick, horny, chitinized cuticle, and is wholly inactive and
takes no food. When the radical changes of the breaking
down of the larval organs and the building of the new organs
of the adult are completed, the cuticle breaks and the winged
imago emerges.

The food habits of the caterpillars make many of them
serious pests of growing crops. Most are leaf eaters, and all
are voracious feeders, so that an abundance of cut-worms or
army-worms or tomato-worms always means hard times for
their favorite food plants. Some kinds do not eat leaves but
attack fruits, as that dire apple pest, the codling-moth larva;
while still others are content with dry organic substances, as
the larvae of clothes-moths, meal-moths and the like. The sole
material compensation which the Lepidoptera make for their
disastrous toll on all green things is the gift of silk made by the

176 ECONOMIC ZOOLOGY AND ENTOMOLOGY

moth species known as the mulberry or Chinese silk-worm.
This thoroughly domesticated and industrious species produces
each year over $100,000,000 worth of fine silk. It can be
reared with perfect success in this country and made to produce
large cocoons of an admirable quality of silk, but the cost of
the labor necessary to caring for the larvae through their long

FIG. 83. Silk-worms, larvae of the moth Bombyx mori. (About \ natu-
ral size.)

growing period is so much higher in America than in Italy, or
France, or the Orient, that silk cannot be produced here under
present conditions to commercial advantage. The method
of rearing silk-worms is, briefly, as follows.

The heavy, creamy white moths take no food, and most of
them cannot fly despite their possession of well-developed
wings, so degenerate are the flight muscles from generations

THE CLASSIFICATION OF INSECTS 177

of disuse. The eggs, about 300, are laid by the female on any
bit of cloth or paper provided for her by the silk-worm growers.
In the annual race of silk- worms, i.e., the one which produces
but one generation a year, the eggs go through the winter and
hatch in the following spring at the time the mulberry trees
begin leafing out. Other varieties produce two (bivoltins),
three (trivoltins), and even five or six (multivoltins) , genera-
tions a year. The larvae, or " silk-worms," must be abundantly
fed with either mulberry or osage orange leaves from which
all rain or dew drops must be wiped off. When very young
they are fed but two or three times a day, but later in their
life must have seven or eight daily meals. They grow rapidly,
and in most races are dull slaty white in color with a few indis-
tinct darker markings. They are very sluggish in habit and
can easily be kept in shallow open trays, which should be kept
well aired and cleaned. The worms molt every nine or ten
days, ceasing to feed for a day before each molting during the
forty-five days of larval life. At the end of this time each
worm spins a dense white or golden or pale greenish silken
cocoon which is, to man, the silk-worm's raison d'etre, but
which is primarily the protecting cover for the defenseless pupa.
In spinning this cocoon the silken thread, which issues from
the mouth and is produced by the hardening of a viscous fluid
secreted by a pair of long silk glands stretching far back in
the body, is at first attached irregularly to near-by objects, so
that a sort of loose net or web is made; then the spinning be-
comes more regular, and by the end of three days the thick,
firm, symmetrical, closed cocoon, composed of a single con-
tinuous silken thread, averaging over 1000 feet long, is com-
pleted. Silk growers provide a loose network of branches or
wicker on which the silk-worms spin their cocoons. Inside the
cocoon the larva pupates, and if undisturbed the chrysalid
gives up its damp and crumpled moth after from twelve to
fourteen days or longer. A fluid secreted by the moth softens
one end of the cocoon so that the delicate creature can force
its way out. But this is the happy fate of only those
moths which the grower allows to issue to lay eggs for the next
year's crop. To produce good silk the grower must save the

1 78 ECONOMIC ZOOLOGY AND ENTOMOLOGY

cocoon from injury by the moth, so he kills his thousands of
pupae by dropping the cocoons into boiling water or by
putting them into a hot oven. Then, after cleaning away
the loose fluffy silk of the outside, he finds the beginning of
the long thread which makes the cocoon, and with a clever
little reeling machine he unwinds, unbroken, its hundreds of

FIG. 84. The luna-moth, or pale empress of the night, Tropcea lima.

(About f natural size.)

feet of merchantable silk floss. Or the cocoons are taken to a
central establishment where the pupae are killed and the silk
wound and made into large skeins ready to go to the cloth-
making mills.

The order Lepidoptera is divided into three principal sub-
orders, namely, the Rhopalocera, or butterflies, which are day

THE CLASSIFICATION OF INSECTS 179

fliers, and which have their antennae slender and thread-like
with the tip thickened so as to form a small spindle-shaped
club; the Hesperina, or skippers, which are also day fliers and
which have the antennas slender and with slightly expanded
or hooked tip; and the Heterocera, or moths, most of which
are night fliers, and which have their antennas variously formed,
either entirely thread-like or with some of the segments pro-
vided with many long hairs arranged so as to make the antennae
look like a flat brush. The Heterocera include by far the
greater number of species of Lepidoptera, and many of the
more obscurely colored ones are rarely seen. They vary in
size from the small clothes-moths and leaf-miners to the great
Cecropias and Lunas. Colored pictures of most of the more
common kinds of moths and butterflies can be found in nature
books, and the different species can readily be determined by
referring to these pictures. A number of the species with
injurious caterpillars are described in Chapters XXX to
XXXVII.

Order Hymenoptera. The Hymenoptera are a large order,
which includes, besides the popularly known ants, bees and
wasps, many less familiar insects showing much variety in
appearance and habit, 7500 species being found in this coun-
try alone. Many of these are parasites, spending their larval
life within the bodies of other insects, feeding on their tissues
and finally destroying them. Because of the great importance
of these parasites in keeping noxious insects in check, and
because of the gifts from the honey-bee and the innocuous
character of most of the other members of the order, the
Hymenoptera may be looked on as the chief beneficial order of
insects.

Few generalizations can be made that will apply to all
members of the order although there is no question concerning
the true relationship of all the kinds of insects included in it.
The name of the order is derived from the clear membranous
condition of the two pairs of wings (hymen, membrane, ptera,
wings). The front wings are larger than the hind ones and
all are provided with comparatively few branched veins.
The workers of all the ant species are wingless as are also the

i8o ECONOMIC ZOOLOGY AND ENTOMOLOGY

females of certain wasps. In many Hymenoptera the front
margin of the hind wings bears a series of small recurved hooks
which, when the wings are outspread, fit over a ridge on the
hind margin of the fore wing thus fastening the two wings firmly
together. The mouth-parts are variously modified, but usu-
ally are fitted for both biting and lapping. This is arranged for
by having the maxillae and labium more or less elongated and
forming a sort of proboscis for taking up liquids, while the
mandibles always retain their short, strong, j aw-like character.
The females throughout the order are provided either with a
saw-like or boring or pricking egg-layer (ovipositor), or with
the same parts modified to be a sting.

In the development of all Hymenoptera the metamorphosis
is complete, and the larvae are, more than in any other order,
helpless and dependent for their food and safety on the
special provision or care of the parents. The parasitic species
lay their eggs either on or in the body of the insect which is to
serve as food for the larvae, while the gall-making kinds lay
their eggs in the plant tissue on which their larvae feed. With
most of the solitary wasps and bees, food is stored up in the cell
in which the egg is deposited, so that the larvae on hatching will
find it ready. With the social wasps and bees and all the ants,
the workers bring food to the young during their whole larval
life.

The Hymenoptera may be roughly divided into a few im-
portant groups. First, the saw-flies (family Tenthredinidce)
whose larvae, soft-bodied, naked, caterpillar-like creatures,
usually with six to eight pairs of abdominal legs besides the
three pairs of thoracic legs, are called slugs. Common kinds
are the current-slug, rose-slug, larch-slug and others, which do
considerable damage by eating away the soft tissues leaving
only the veins, thus making "skeletons" of the leaves of their
food plants. The saw-flies compose a large family, 600 species
being known in this country, but the adults are rarely seen by
the general observer.

Second, the great group of parasites comprising several
families (Ichneumonidce, BraconidcE, Chalcididce, Proctotrypidce,
and others), and including species varying in size from the

THE CLASSIFICATION OF INSECTS

181

smallest insects known to others two inches or more in length.
Some of these minute parasites lay their eggs within the eggs of
other insects, and their larvae live their whole lives in the con-
tents of these host eggs, but most Hymenopterous parasites
deposit their eggs on the skin of the larvae or nymphs of other
insects, especially on caterpillars. The parasite larvae, on
hatching, bore their way through the skin into the host body
and remain there, feeding on the blood lymph and perhaps on
other body tissues. The host dies, but
usually not until the parasites have com-
pleted their larval life and have changed
to pupae either within the host's body, or
have issued from it and pupated outside.
Parasitized caterpillars are often able to
pupate, but from their pupa there issues,
not a moth or butterfly, but many of the
little four-winged parasites. These fly
freely about, mate, and then deposit their
eggs on the body of other hosts.

A few members of this group are not
parasites but gall-makers. Among these qnisitor, laying egg in

an important kind is the curious small fig- cocoon of American

/n; L i \ r. t_- i_ J.-L o tent-caterpillar moth.

wasp (Blastophaga) by which the Smyrna (About natural size;

figs are cross-pollinated and made to set after Fiske.)
seed and thus to become especially palata-
ble. The fig- wasp has been introduced from Asia Minor into
California, and has greatly added to the value of California
figs.

Third, the family Cynipida or gall-flies, some of which are
parasites, but most of which thrust their eggs, by means of a
sharp ovipositor, into the leaves or green stems of oaks, roses
and a few other plants, so that the hatching larvae find them-
selves surrounded by rich plant food. The presence of the
larva stimulates the plant to a vigorous production of new
tissue about it, which takes on the form of a gall of definite
shape. These galls are different for different species of gall-
flies, and for different species of plants, and present a host of
curious shapes. Some look like tiny seeds or papilla? on the

FIG. 85. Ichneu-
mon fly, Pimpla con-

182 ECONOMIC ZOOLOGY AND ENTOMOLOGY

leaf or stem, while others, as the giant oak-gall of California,
are as large as one's fist. The gall-fly larvae lie in the middle
of the galls feeding on the abundant plant juice and pupating
there in the autumn when the active plant growth ceases. The
gall-flies issue in the following spring, biting their way out of
the gall by means of their stout jaws.

The fourth, fifth and sixth groups of Hymenoptera are the
wasps, bees and ants. They are treated in the following
chapter.

CHAPTER XVIII

INSECTS (Continued): WASPS, ANTS, THE HONEY-
BEE AND OTHER BEES

Wasps. The wasps are divided into two groups, viz., the
solitary or digger wasps (superfamily Sphecina), and the social
wasps (super-family Vespina). The Sphecina, as represented
in North America, include a dozen or more families, while the
Vespina include but three, but these latter wasps, or a few of
them, the hornets and yellow-jackets, are more often seen and
much better known popularly than the solitary wasps. Among
the solitary bees each female makes a simple nest, usually a
short burrow in the ground or in a plant stem (in the case of a

FIG. 86. Digger-wasp, Ammophila, putting inch-worm into nest-burrow.

(From life; natural size.)

few parasitic kinds the wasp makes no special nest at all), lays
one or more eggs in it, stores it with food for the hatching larvae,
and closes it up. This food is usually other insects or spiders
stung to death or, more commonly, stung in such a way as not
to kill but paralyze the prey. When the wasp larvae hatch
they find their food all ready for them, devour it slowly as they
grow, pupate in the nest burrow, and finally issue as full
fledged wasps.

The social wasps live, as is well known, in large communities
composed of an active egg-laying female or queen, a few males

183

184 ECONOMIC ZOOLOGY AND ENTOMOLOGY

or drones, and many infertile females, or workers. A small
nest is made in the spring out of chewed old wood mixed with
saliva so as to form "wasp-paper," by a queen that has mated
in the autumn before and passed the winter solitarily in hiding.
In this little "queen nest" she lays a few eggs, brings food to
the hatching larvae until they change to pupae in their cells,
and then awaits their issuance. They issue as workers, and
immediately enlarge the nest, making more paper combs and
cells, in which the queen lays more eggs. The workers bring
food, which is killed and masticated insects, and care for the

young, which develop into
more workers. Thus the com-
munity, or really family,
grows through the summer,
till it may contain many hun-
dred individuals. In the late
summer males and fertile fe-
males are produced, and then

FIG. 87. Two workers of the w jth the oncoming of winter
yellow-jacket, Vespa sp. (From ,1 , i i i

life; natural size.) the workers and males and

many of the females die, leav-
ing a few mated females to pass the winter and begin new
colonies in the spring. Thus the social wasp communities
break down and are rebuilt annually.

Bees. This is also the case with the communities of bumble
bees, which are the simplest kind of social bees. There are
among the bees solitary kinds also, with the same general
manner of life of the solitary wasps, except that the food col-
lected and stored for the young is never killed or paralyzed
insects but always flower nectar and pollen mixed. This is
also the kind of food brought by the bumble-bees for their
larvae.

Among the bees there is however another and more special-
ized type of social kind. This type is represented in America
by a single species, the honey-bee or hive-bee, Apis mellifica,
which is not a native insect but one introduced long ago from
Europe. With this bee the community does not break down
annually but persists, under favorable conditions, indefinitely.

WASPS, ANTS AND BEES

185

The hive-bee has long been a domesticated species of animal,
and several different varieties or races of it have been created
by artificial selection, the more familiar ones being the German
or black race, the Italian or amber race, and Carniolan or
striped race. As the life of the honey-bee is not only one of
the most interesting of all animal lives, but is one which the
economic zoologist needs especially to know, we give in the
following pages a rather detailed ac-
count of the natural history of the
honey-bee, mostly taken from Chapter
XV of "American Insects," by the sen-
ior author.

The Honey-bee. A community of
the hive-bee, which may live, of course,
not in a hive at all, but in a hollow
tree, as undoubtedly was the habit of
the species in wild state (the "bee-
trees" of America, however, are inhab-
ited by bee colonies which have swarmed
away from domesticated ones and are
only wild by virtue of escaping from
the slave-yards of their human mas-
ters), consists normally of about 10,000
(winter) to 50,000 (summer) individuals,
of which one is a fertile female, the
queen; a few score to several hundred are
males, the drones; and the rest are infer-
tile females, the workers. These three
kinds of individuals are readily distinguishable by structural
characters. The queen has a slender abdomen one-half longer
than that of a worker, she has no wax-plates on the underside
of the abdominal segments, and no transverse series of comb-
like hairs, the planta, on the underside of the broad first tarsal
segment of the hind feet, and no pollen-basket on the outer
surface of the hind tibia. The drones, males, have a heavy
broad body excessively hairy on the thorax, and lack pollen-
basket, planta, wax-plates, and other special structures of the
workers. The workers are smaller than queen or drones, and

FIG. 88. Bumble-bee
at clover blossom.
(From life; natural size.)

1 86 ECONOMIC ZOOLOGY AND ENTOMOLOGY

possess certain special structures or body modifications to
enable them to perform certain special functions connected
with their performance of the various industries characteristic
of the species. These special structures will be described in
some detail later when the various special industries are par-
ticularly considered. In internal organization the workers
differ from the queen in having the ovaries rudimentary, so
that only in exceptional cases can workers produce fertile
eggs.

In functions the three castes differ as they do in the social
wasps and the bumble-bees, only more constantly; that is, the

queen lays the eggs, never, as with
the bumble-bees and social wasps,
doing any food-gathering or nest-
building; the males act simply as
consorts for the queen, which
means that only one of every thou-
sand, perhaps, performs any neces-
sary function at all in the commu-

FIG. 8 9 .-Honey-bee, Apis nal <*onomy; the workers build
mcllifica. a, Queen; b, drone; c, brood- and food-cells, gather, pre-
worker. (About jnatural size.) pare and store food, feed and

otherwise care for the young, re-
pair, clean, ventilate, and warm the hive, guard the entrance
and repel invaders, feed the queen, control the production of
new queens, and, with the aid of a queen, distribute the spe-
cies, founding new communities, by swarming.

The life history of a community is as follows: A "swarm"
consisting of a queen and a number of workers (from two to
twenty thousand or more), issues from a community nest and
finds, through the efforts of a few of the workers, a place for a
new nest. This is some sheltered hollow place, usually, through
the intervention of the bee-keeper, another hive. Taking
possession of this new nesting-place, the workers immediately
begin to secrete wax and to build "comb," i.e., double-tiered
layers of waxen cells, usually as "curtains" or plates hanging
down from the ceiling of the nest. The bee-keepers supply
artificially made "foundations" or beginnings of these curtains

WASPS, ANTS AND BEES 187

in vertical frames set parallel and lengthwise of the hive, so
that the combs will be built symmetrically and conveniently
for the bee-keeper's handling. In many of these cells the
queen, which has received the fertilizing sperm-cells from a
male during a mating flight high in the air, lays fertilized eggs,
one at the bottom of each cell. In other cells, pollen and
nectar brought by workers are stored for food. In three days
the eggs hatch, the tiny larvae being footless, white, soft-bodied
helpless grubs. They are fed at first exclusively with "bee-
jelly, "a highly nutritious, "pre-digested" substance elaborated
in the bodies of the nurse workers and regurgitated by them
into the mouths of the larvae. After a couple of days of feeding
with this substance, the larvae are fed, in addition to bee-jelly,
pollen and honey taken by the nurse from the cells stored with
these food-substances. After three days of this mixed feeding,
the larvae having grown so as to fill half or two-thirds of the cell,
lying curled in it, a small mass of mixed pollen and honey is
put into each cell, which is then capped, i.e., sealed over with a
thin layer of wax. The larva feeds itself for a day or two
longer on the "bee-bread" and then pupates in the cell. The
quiescent non-feeding pupal stage lasts for thirteen days, when
the fully developed bee issues from the thin pupal cuticle,
gnaws away the wax cap and emerges from the cell. For from
ten days to two weeks the bee does not leave the hive; it busies
itself with indoor work, particularly nurse work, the feeding
and care of the young. Then it takes its place with the fully
competent bees, makes foraging expeditions or undertakes
capably any other of the varied industries of the worker
caste.

After numerous workers have been added to the community,
egg-laying by the queen going on constantly, so that the young
come to maturity, not in broods, but consecutively, day after
day, certain hexagonal cells of plainly larger diameter are made
by the comb-building workers, and in these the queen lays
unfertilized eggs. This extraordinary capacity for producing
either fertilized or unfertilized eggs, as demanded, depends
upon the queen's control of the male fertilizing cells held in the
spermatheca. This reservoir of fertilizing cells can be kept

i88 ECONOMIC ZOOLOGY AND ENTOMOLOGY

open as eggs pass down the oviduct and by it on their way out
of the body, thus allowing the spermatozoids to swim out,
penetrate (through the micropyle in the egg-envelopes) and
fertilize the eggs, or it may be kept closed, preventing the
issuance of the spermatozoids and, consequently, fertilization.
From the unfertilized eggs laid in the larger cells hatch larvae
which are fed and cared for in the same way as the worker
larvae, but which require six days for full growth, the pupal
stage lasting fifteen days. When finally the fully developed
bees issue from these cells it will be found that all are males
(drones). This parthenogenetic production of drones, dis-
covered about 1840 by Dzierzon, and long accepted as proved,
was recently questioned by Dickel and one or two other natu-
ralists and was therefore reinvestigated by Petrunkewitsch
and others, with the result of confirming, on new evidence,
and by new methods of investigation, the declarations of the
discoverer of the fact.

If, now, the bee community has increased so largely in num-
bers that its quarters begin to be insufficient for further ex-
pansion, excited groups of workers will be seen tearing down
certain cells and replacing them by a new giant cell which is
usually built up around one of the fertilized eggs laid in a
small hexagonal cell. The egg hatches before the cell is fin-
ished, and the larva lies in the large open cavity of the growing
cell, on which numerous nurses are in constant attendance.
Often several of these unusual giant cells may be built at one
time. The larva which hatches from the fertilized egg in one
of these cells is fed the nutritious bee-jelly through all of its
life, little or no pollen or honey being given it. When the
larva is five days old a quantity of the milky semi-fluid jelly
is put into the cell, which is then capped, the opening being at
the bottom of the hanging, nut-shaped cell, and in only seven
days more the fully developed bee issues. This bee is a queen.
Very rarely a worker and not a queen issues from a queen-cell.
That is, a larva hatching from a fertilized egg laid by the
queen in a small hexagonal cell, if fed bee- jelly for two or three
days and then pollen and honey, will develop into a worker;
that larva from the same egg if fed bee-jelly all its life, and

WASPS, ANTS AND BEES 189

reared in a large roomy cell, will develop into a queen. The
differences between a queen honey-bee and a worker honey-bee,
both structural and physiological, are as already pointed out,
conspicuous. The influence of a varying food-supply is some-
thing mysteriously potent, and this case of the queen bee
gives great comfort to those biologists who believe that the
external or extrinsic factors surrounding an animal during
development have much influence in determining its outcome.

As there is by immemorial honey-bee tradition but one queen
in a community at one time, when new queens issue from the
great cells something has to happen. This may be one of three
things; either the old and new queens battle to death, and it is
believed that in such battles only does a queen bee ever use her
sting, or the workers interfere and kill either the old or the new
queen by "balling" her (gathering in a tight suffocating mass
about her), or either old (usually old) or new queen leaves the
hive with a swarm, and a new community is founded. If
several new queens are to issue, the workers usually, by thick-
ening the outside walls of one or more of the cells, compel the
issuing to be successive and not simultaneous. This results
in a series of royal battles, or a series of swarmings, or a combi-
nation of the two. A queen ready to issue from a cell makes
a curious piping audible some yards from the hive, which is
answered by a louder piping, or trumpeting, from the old
queen. At these times there is great excitement in the hive,
as indeed there is during all of the queen-raising season.

The swarming out, it is apparent, does not break up the old
community; in fact only accident, or the successful attacks of
such insidious enemies as the bee-moth, and various contagious
diseases, break up the parent colony. In this respect is to be
noted an important difference between the other social bees
and wasps with their communities annually destroyed and
refounded, and the honey-bee with its persistent one. Of
course workers die and so do drones and queens. The tireless
workers which hatch and labor in the spring and summer
months rarely live more than six or eight weeks, while the
workers born in the late autumn and remaining quietly in the
shelter of the hive through the winter live for several months.

igo ECONOMIC ZOOLOGY AND ENTOMOLOGY

Queens live, usually, if no accident befalls, two or three years;
an age of four or five years is occasionally attained. Most of
the drones in each community either die naturally before win-
ter comes or are killed by the workers. Feeble workers and
larvae and pupae are also sometimes killed just before winter,
if the food-stores which are to carry the community through
the long flowerless season are for any reason not likely to prove
sufficient for so large a number of individuals. In all these
matters, that is, the making of queens and when, the swarming
out and when, and the reduction of the community to safe
winter numbers, the decision is made by the workers and not
the queen. The queen is not a ruler; she is the mother, or,
better, simply the egg-layer for the whole community.

The drones, we have seen, have one particular function to
perform in the community life, the queen another single partic-
ular function; but the workers have numerous varied perform-
ances to achieve if the community shall live successfully. It
might be expected by analogous conditions elsewhere existing
in animal life, that with the division of labor in the honey-bee
economy there should be a corresponding differentiation of
structure or polymorphism inside the species. This polymor-
phism or existence of structurally different kinds of individuals
occurs in bees only to the extent already pointed out; there are
three kinds of individuals: the queens, with a special function,
the drones with a single special function, and the workers, each
capable of performing, and, for the time of the performance,
doing it exclusively, any of the varied industries necessary to
the community life. All worker honey-bees are alike, each
possessing all the special structural specializations, as pollen-
basket, wax-plates, wax-shears, trowel-like jaws, etc. which
have been developed for the special performance of particular
industries. In some other communal insects a differentiation
or polymorphism among the workers exists; many ant species
have two and even three kinds of workers, the termites have
soldiers as well as workers, etc. We purpose now to describe
briefly each of the principal special industries achieved by the
workers, at the same time describing the structural specializa-
tion connected with each of these industries.

WASPS, ANTS AND BEES

191

The wax produced by the workers is a secretion which issues
as a liquid, soon hardening, from pairs of thin five-sided plates,
one pair on the ventral surface of each of the last four abdomi-
nal segments. It is secreted by modified cells of the skin,
lying under the chitinized cuticle of the plates, and oozes out
through fine pores in the plates. To produce it certain workers
eat a large amount of honey, then massing together form a
curtain or festoon hanging down from the ceiling of the hive
or frame, and increase the temperature of their bodies by some
strong internal exertion; after the lapse of several hours, some-
times indeed of two or three days, fine, thin, glistening, nearly
transparent scales of wax appear on the
" wax-plates. " These wax-scales continue
to increase in area and soon project beyond
the margin of the segment, when they
either fall off or are plucked off by the
wax-producing worker. They are then
taken in the mouth, sometimes chewed
and mixed with some saliva, and carried
to the seat of the comb-building operation.
Here the wax is pressed against the frame
roof (or artificial foundation) and by means
of the trowel-like mandibles moulded into
the familiar hexagonal cells; each comb be-
ing composed of a double layer of these
cells, a common partition serving as base
or bottom of each tier. Although most
bee books speak rather glibly of the comb-building operations,
many of its details are still undetermined. In building cells
for storing honey, new wax is almost exclusively used; for
brood-cells, old wax and wax mixed with pollen may be used.
Any comb or part of a comb not needed is torn down and
the wax used to build other comb or to cap cells.

The seeking and collection of pollen and honey is not under-
taken by a bee until from ten to fifteen days after its emergence
from the pupal cuticle, these first days being spent in the hive
at nurse or other indoor work. Then short orienting flights
begin to be made, and soon the long-distance flights (a mile or

FIG. 90. Ventral
view of abdomen of
honey-bee worker,
showing wax plates.
(About 3 times nat-
ural size.)

i 9 2 ECONOMIC ZOOLOGY AND ENTOMOLOGY

more sometimes), which are often necessary for successful
foraging, are undertaken. The pollen is taken up or brushed
off from the ripe anthers of the flowers with the mouth-parts,
fore legs or ventral body- wall, the pollen-grains being readily
entangled in the numerous branching hairs, and then, by
clever manipulation of the fore, middle, and hind legs aided by
special pollen brushes (plantae) on the inner side of the first
tarsal segments of the hind feet, transferred and packed into
the pollen-baskets, one on the outer face of each hind tibia. A
forager loaded with pollen returns to the hive, and, seeking an
empty cell near the brood-cells, stands over it and with her
hind legs partly in it, thrusts off the two masses with the
aid of the middle legs (the spurs of the middle tibiae being
apparently often used as pries). This pollen is tamped
down in the cell by inside workers and receives no further
manipulation.

The "honey" which is collected by the foragers is not yet
bee-honey, but is nectar of flowers, too watery and too likely
not to "keep" to be stored in the cells without further treat-
ment. It is sucked and lapped up by the complicated elongate
flexible mouth-proboscis, swallowed into the fore-stomach or
honey-sac, and carried in this to the hive. Bees have been
seen to exude drops of water on their return flight when honey-
laden, and it is possible that it comes from the nectar in the
honey-stomach. At any rate some 10 or 12 per cent, of
the water content of the nectar has to be evaporated before
this nectar becomes honey. When the foraging worker with
honey-sac full returns to the hive it regurgitates its nectar
either into the mouth of another bee or into a clean (new wax)
cell, usually near the margin of the comb. At the bottom of
the honey-sac is the so-called stomach-mouth, a little pea-like
protuberance with two cross-slits, making four lips. These
lips can be opened or closed voluntarily; if the bee drinking
nectar wishes to bring it back to the hive to store it, she keeps
them closed, thus making a sac of the honey-stomach, open
only through the mouth; whenever she wishes to feed herself
she opens them, thus allowing the honey or pollen to pass on
into the true or digesting stomach. This arrangement also

WASPS, ANTS AND BEES 193

permits of the regurgitation of the bee-jelly or bee-milk (fed
the larvae by the nurse workers), which is believed to be pre-
pared in the true stomach, pressed past the lips forward into
the honey-stomach and on through the esophagus into the
mouth.

When the nectar is put into the honey-cells it has still to
have much water evaporated from it. To accomplish this an
effective system of ventilation is set up in the hive, so that
air-currents pass constantly over the open nectar-containing
cells; moreover, by the very vigor of this activity on the
part of the bees the temperature of their bodies is raised;
by radiation of heat from the bodies the temperature in the
hive is sensibly increased, and the currents of warm air soon
carry off the excess water. To make the honey "keep," that
is, to make it antiseptic, formic acid is added to it, probably
from glands in the head whose secretions distinctly show its
presence. It is just possible that the formic acid is supplied
by the poison-sacs, the poison introduced by the bee's sting
being largely composed of formic acid. But it is much more
probable that at the time of the regurgitation of the nectar
from the honey-stomach through the mouth the formic-acid
secretions from the head-glands are mixed with it.

Nectar for honey-making is obtained by bees from a great
many different plants, but that from some makes honey better,
to our taste, than that from others. Among the most impor-
tant producers of the best honey in the east and north are white
clover, basswood, buckwheat, and the fruit trees and small
fruits; in the middle states are the tulip tree, sorrel- tree, sweet
clover, and alfalfa; in the south are the mangrove, cabbage-
and saw-palmettos, orange trees and sorrel-tree ; while in
the west are alfalfa and white sage.

Besides pollen and nectar, two other substances are collected
and brought to the hive by the foraging workers. At some
seasons of the year when many larvae are being reared, and the
supply of water derived by condensation of the moisture in
the warm hive atmosphere as this air strikes the cooler hive-
walls is insufficient, the workers drink up dew from leaves, or
water from puddles, which they hold in the honey-sac and bring
13

i94 ECONOMIC ZOOLOGY AND ENTOMOLOGY

to the hive, regurgitating it into the thirsty larval mouths.
For the filling in of crevices, the stopping up of holes, the fasten-
ing together of loose parts, etc., the bees use a substance
called propolis, which is made of the resinous exudations of
various plants. This propolis is collected and packed into
the pollen-baskets as pollen is and brought in by the foragers.
Some of our bees, needing propolis, discovered a house just in
course of painting, and made a gallant though hopeless struggle
to bring in all the fresh paint as fast as it was put on by the
painters! Propolis is not packed in cells, but is used as soon
as brought in, the trowel mandibles being the instruments
used in putting and moulding it in the needed place.

Of the indoor work there is much besides those industries
already referred to, namely, wax-making, comb-building, honey-
making, crevice-chinking. Because the queen and nurses
(bees less than two weeks old) do not leave the hive, their
excreta are voided within doors; there are also bits of old,
dirty wax, occasional dead bees, and various other waste
substances constantly accumulating in the hive. Or, rather,
this detritus would accumulate if the workers were not always
keenly careful to carry out all such stuff; the hive is constantly
being cleaned, and is on any day in the week a model of good
housekeeping.

Besides keeping the hive clean the workers must keep it
ventilated, that is, clean of atmosphere as well as clean of floor
and wall. This is done by setting up air-currents through the
hive which carry out constantly the vitiated air and thus com-
pel fresh air to enter. Always near the exit and scattered
through the hive, especially along its floor, may be seen bees
standing with head down and body diagonally up and wings
steadily vibrating with great rapidity. These are the ven-
tilating agents, and they have an exhausting and tedious
work.

About the entrance may be also always seen bees which seem
neither to be leaving the hive nor entering it, but which move
about constantly and meet and touch antennae with all in-
comers. These are the warders of the gate. There are never
wanting enemies of the industrious, well-stocked honey-bee

WASPS, ANTS AND BEES

community, whose entrance into the hive must be vigorously
guarded against. Yellow-jackets hover tentatively around
the opening; they are arrant robbers and are ready to take
any chance to get at the full honey-cells. But more dangerous,
because of the habit of attacking en masse, are honey-bees of
other hives. Not infrequently a desperate foray by hundreds

FIG. 91. A small observation hive in which the honey-comb has been
destroyed by larvae of the bee moth, Gallcria mellondla. (Greatly re-
duced.)

of other bees will be made into a hive, especially a weak one,
and a pitched battle will occur in and about the entrance and
inside the hive itself, resulting in the death of hundreds, even
thousands of bees. More insidious and even more dangerous
are the stealthy invasions of a small dusty-winged moth, the
"large" bee-moth, Caller ia mellonella, or the "small" bee-moth,

i 9 6 ECONOMIC ZOOLOGY AND ENTOMOLOGY

Achroia grisella, which, slipping in at night unobserved, lay
their eggs in cracks; the larvae which hatch from the eggs feed
on the wax of the combs, and as they spin a silken net over
them wherever they go, the presence of many such larvae works
great injury both in the actual destruction of comb and in the
felting and cobwebbing of the interior of the hive with the
tough silken netting. Other still more insidious enemies there
are, as the minute bee-lice, Braula, which attach themselves
to the bees and suck out their body juices, and the invisible
bacterial germs of foul-brood and other characteristic bee
diseases. But all these are beyond the sensitiveness of the
guards to recognize, and for the successful fighting of them
the aid of the bee-keeper is necessary.

The feeding and care of the young bees, the larvae, have
already been partly described in the account of the life history
of the different kinds of individuals in the community, and
cannot be further referred to in this brief history of the honey-
bees' domestic economy. Of course only the more conspicuous
features in this economy have been described at all; a host of
interesting details cannot even be mentioned. But enough
has been said, surely, to indicate the fascinating field of obser-
vation afforded by a honey-bee community. If such a com-
munity be kept in an observation-hive and this hive be placed
conveniently near the house, or, better, inside one's room, it
will prove a never-failing source of interest and pleasure.

Perhaps it had better be explained how an observation-hive
can be kept in one's room without interfering with coincident
human occupancy. The observation-hive, in the first place,
may be simply an outdoor hive into each side of which a
large pane of glass has been let, with swinging outer wooden
doors, one on each side, which, when shut, keep the hive in
normal darkness, but opened, allow -"observing" to go on.
In addition to the side glasses a loose sheet of glass is inserted
just under the ordinary "honey-board" or removable top of
the hive. Or the observation-hive may be a special narrow,
two-frame hive, with both sides wholly composed of glass held
in the narrow wooden frame which forms the ends and the top
and bottom of the hive. A black cloth jacket should be kept

WASPS, ANTS AND BEES

197

on the hive when "observing" is not going on. In such a
hive, which will obviously hold but a small community (one of
not over 10,000 individuals) any single bee can be kept con-
tinuously under observation, as there are no side-by-side frames
between which it can crawl and thus be hidden from view.
To keep either of such hives in the house it is only necessary
to substitute for a pane of glass in a window a thin wooden
pane in which is cut a narrow horizontal opening, the size of
the regular hive-opening (if the latter is too broad it can be

FIG. 92. An ordinary bee-hive made into an observation hive by
inserting glass panes in sides and putting a glass sheet under the wooden
cover.

closed for a few inches at each end) . Or a narrow broad strip
of the full width of the window can be inserted so that the
lower sash of the window, when closed, will rest upon this
strip. In the strip cut a narrow opening of the width, or less,
of the hive opening. Set the observation-hive on a table or
shelf against the window so that the hive-opening corresponds
with that in the window pane or window-strip. Or, better,
place it six or seven inches from the window and connect hive
and window-opening by a shallow broad tunnel of wooden

198 ECONOMIC ZOOLOGY AND ENTOMOLOGY

bottom and sides but glass top. Over the glass top of this
tunnel lay a sheet of black cardboard, which will keep the
tunnel dark normally, but which can be simply lifted off
whenever it is desired to see what is going on at the entrance.
Here can be seen the departure of the foragers and their arrival
with pollen, propolis, or honey, the alertness of the guards,
the repelling of robbers and enemies, the killing of drones, the
ventilating etc., etc. Through the glass sides of the hive
itself can be seen all the varied indoor businesses in their very
undertaking; the life history of each kind of individual can
be followed in detail; the wax-making and comb-building, the
storing of the food-cells, the feeding of the young by the nurses,
the excitements, the joys, and the discouragements, the whole
course of life in this microcosm.

Practical bee-keeping is based first of all on a sound knowl-
edge of the natural history of the honey-bee, and second on an
acquaintance with the methods and tools used in handling
hives and honey. To the acquirement of the first of these
requirements we have just tried to guide the student. For
the second we must refer him to some one of the many book
guides for such work. Anna B. Comstock's "How to Keep
Bees" is a good small book; Root's "A, B, C and X, Y, Z of
Bee Culture" is a good larger one.

Cross-pollination of Flowers by Bees and Other Insects. A
means by which insects indirectly render a great economic
service to man is by their cross-pollination of flowers. The
nectar of flowers is a favorite food with many insects; all the
moths and butterflies, all the bees and many kinds of flies are
nectar-drinkers. Flower-pollen, too, is food for other hosts
of insects, as well as for many of those which take nectar.
The hundreds of bee kinds are the most familiar and con-
spicuous of the pollen-eaters, but many little beetles and some
other obscure small insects feed largely on the rich pollen-
grains. But the flowers do not provide nectar and pollen to
these hosts of insect guests without demanding and receiving
a payment which fully requites their apparent hospitality.
This payment is the cross-pollination by the insects of the
nectar-providing flowers. The agency of insects in this matter

WASPS, ANTS AND BEES 199

has long been recognized, and some orchard growers keep
hives of bees in or near their orchards to ensure the advantage
of cross-pollination to their trees.

Cross-pollination is simply the bringing of pollen from one
plant individual to the flowers of another individual of the same
species. Self-pollination is the getting of pollen from the
stamens of one flower on to the stigma of the same flower.
The advantage of cross-pollination, as first experimentally
proved by Darwin, and since then confirmed by other experi-
menters and, without scientific intention but none the less
effectively, by hosts of economic plant-breeders (horticul-
turists, florists, etc.), lies in the fact that the seeds produced
when the ovules of one plant are fertilized by the sperm-cells
(in the pollen) of another, develop plant individuals of mark-
edly stronger growth (shown in size of plant and its fruits, in
number of seeds, etc.), than seeds produced by the fertilization
of ovules by sperm-cells of the same plant. For the sake of
insuring this cross-pollination the flowers of many plants are
highly specialized. This specialization follows two general
lines: One includes means of preventing self-pollination such
as having stamens and pistils ripen at different times, or be of
such different lengths that the pollen cannot fall on the pistils
in the same flower, etc. The other line includes means for
attracting insects, such as color and pattern and the secretion
of nectar, and means, such as shape, curious modification of
flower parts, etc., to compel the visiting insects both to leave
on the stigma pollen brought from other flowers and to carry
away from the anthers pollen from the flower being visited.
Honey bees are undoubtedly the most important of all insects
concerned with cross-pollination, and perform in this way a
great service to flower and orchard growers.

The Ants. The ants constitute the fifth and last principal
group of Hymenoptera, and for their adequate treatment a
book much larger than the whole of this one would be necessary.
Such a book, indeed, has been recently written by Professor
W. M. Wheeler, 1 the foremost American student of ants, and

1 Wheeler, W. M. Ants, their Structure, Development and Behavior,
1910.

200 ECONOMIC ZOOLOGY AND ENTOMOLOGY

it is one of the most fascinating and stimulating books of
natural history ever written.

About five thousand kinds of ants are known, all of which
live socially in small or large communities comprising three
usually well-distinguished types of individuals, namely, fertile
females, or queens, males, or drones, and sterile females, or
workers. The workers are wingless, while the males and queens
are winged, although the queens pull off their wings after
mating. There may be a certain further amount of structural
differentiation within a species in that the workers may be of
two or three different types. The general appearance of ants
is so characteristic that they are readily distinguished from all
other insects, and their extraordinarily developed communal
life is more or less familiarly known to every observer or reader.
To the economic zoologist, however, ants do not present any
very large importance. A few kinds of house ants can be
extremely troublesome and a few garden-infesting kinds do
some injury to vegetables and fruits. Their greatest damage
probably is done indirectly, through their habits of protecting
and caring for plant-lice (aphids), from which they obtain
their favorite food of "honey-dew." All of these protected
aphids are injurious to plants because they suck their sap.

The ant communities live in nests comprising a number of
irregular chambers and galleries, most of the species living
underground, although a considerable part of the nest may be
above the normal ground surface, built up as a mound or hill-
side, of more or less symmetry and greater or less size. This
part above ground may be composed chiefly or wholly of soil
brought up from below surface, or may be partly or wholly
made up of bits of wood, grass and weed stems, chaff or pine-
needles. The nest may be made under a stone or log, or be
established in a wholly exposed place. Most ants keep their
nest fairly near the surface, but a few mine deeply. Still other
species tunnel out their corridors and rooms in wood an old
log or stump, dry branches, or what not while yet others live
in the stems of plants, in old plant-galls, in hollow thorns and
spines; finally a few make nests of delicate paper or tie leaves
together with silken threads. Very wonderful are some of the

WASPS, ANTS AND BEES 201

inter-relations between certain plants and certain ant species
in tropic regions, whereby the plant seems to have developed
suitable cavities for the accommodation of the ants, whose pres-
ence in turn is advantageous to the plant by the protection it
affords against the ravages of certain leaf-eating insects which
are repelled, or rather attacked as prey, by the ants. In many
cases two ant species will live together in a compound or mixed
nest, the relation between the two species being (a) simply
that of two close neighbors, friendly or unfriendly; (b) that
of two species having their nests with "inosculating galleries"
and "their households strangely intermingled but not actually
blended"; (c) that of one species, usually with workers of
minute size, which lives in or near the nests of other species
and preys on the larvae or pupae or surreptitiously consumes
certain substances in the nests of their hosts some different
larger species that is, the relation of thief and householder;
(d) that of two species living in one nest but with independent
households, one of these species living as a guest or inquiline
at the expense of the food-stores of the other, but consorting
freely with their hosts and living with them on terms of mutual
toleration or even friendship; and (e) that of slave-maker and
slave, a relation not at all rare and readily observed all over
our country.

Inside the nest the eggs are laid by the queen or queens in
large numbers, not in separate cells as with the wasps and
bees, but in little piles heaped together in various rooms and
sometimes moved about by the workers. The hatching larvae,
tiny, white, footless, helpless, soft-bodied grubs, are fed by the
workers either a predigested food regurgitated from the mouth,
or chewed fresh insects, caught and killed by the workers, or
dry seeds or other vegetable matter brought into the hive and
stored in the "granary" rooms. A single species may use all
these different kinds of food, but for the most part the ants
belonging to one species habitually use one kind of food for the
young. The primitive food consists of seeds and cut-up
insects. The adult ants feed on a variety of substances, both
animal and vegetable, almost all, however, having a special
taste for sweetish liquids, such as the secreted honey- dew of

202 ECONOMIC ZOOLOGY AND ENTOMOLOGY

plant-lice, scale-insects, certain small beetles and others, and
the sugary sap of certain trees. The males and fertile females
are fed by the workers.

Besides feeding the larvae, the nurses have to see that the
young enjoy suitable temperature and humidity of the atmos-
phere; this is accomplished by moving the larvae or pupae from
room to room, farther below the surface, or even out into the
warm sunshine above ground. The carrying about of ants'
"eggs," which are not eggs but usually the cocooned pupae,
by the workers, is a familiar sight around any ant-nest, particu-
larly a disturbed one. The various special industries under-
taken by ants, as the attendance on and care of honey dew-
secreting plant-lice, the fungus-growing in their nests, the
harvesting (but not planting!) of food-seeds, the waging of
wars for pillage or slave-making, the long migrations, etc., etc.,
are -more or less familiar through much true and some inaccu-
rate popular writing.

In any community there may live at one time several (two
to thirty) queens with wings removed. In small colonies there
is, however, usually but one. As already mentioned, winged
ants are to be seen only at certain times in the year. When a
brood of sexual individuals (males and females) is matured in
the community, these winged forms issue on a sudden impulse
(comparable in a way with the outwinging ecstasy of bees at
swarming time) from all the openings of the nest and take wing.
The air may be swarming with them, flights from neighboring
nests intermingling and joining. This is the mating flight,
and after, it is over those ants which have escaped the bird
attacks and other dangers attending this bold essay into the
outer world alight or fall exhausted to the ground; the males
soon die, while the females pull the wings from the body and
get under cover. In the communal nest, therefore, winged
ants are rarely found. The life of the workers of most ant
species is conspicuously longer than that of other social insect
workers; they live for from one to three or four or even five
years. Lubbock has kept workers until six years old, and
queens until seven. The males all die young, but both other
kinds of individuals are exceptionally long-lived for insects.

WASPS, ANTS AND BEES 203

There are several different ways in which a new community
may be founded. A fertilized queen may begin alone the
establishment of a new community by building a little nest,
laying a few eggs, caring for the hatching larvae herself, and
thus raising by her unaided exertions a small brood of neuter
workers which are always normally undersized, probably from
insufficient nourishment. This mode of community founding
is just like that obtaining among the social wasps and the
bumble-bees. An interesting fact in these cases is that the
food given the larvae by the queen is supplied from her own
body, by regurgitation through the mouth, no food whatever
being brought into the nest from the time that the queen first
begins to lay eggs until this first brood is matured.

Another method of colony founding is by the withdrawal of
young fertilized queens each with a group of workers from an
old and over-populous community. Still other methods are
those, recently carefully worked out by Wheeler and other
students, in which queen ants of one species found colonies by
the aid of workers of other species. Several phases of this
method have been observed. In one phase a queen enters a
colony of an alien species and decapitates its queen or is the
occasion of her being killed off by her own workers. The
intruding queen is then adopted by the workers and proceeds
to lay eggs whose hatching larvae are reared by the alien
workers and a compound or mixed colony is thus formed. In
another phase of this general method a queen enters a colony
of another species, snatches up the worker brood and kills any
of the workers or queens that endeavor to dispute her posses-
sions. The ants hatch with a sense of affiliation with their
foster mother and proceed to rear her eggs and larvae as soon
as they appear. Here, too, the colony is formed by a mixture
of two species, but the workers produced by the intrusive
queens inherit her predatory instincts and therefore become
slave-makers. They keep on kidnapping worker larvas and
pupae from the nests of the alien species, carry them home, and
eat some of them but permit many to mature, so that the mixed
character of the colony is maintained.

The observation and study of ants' ways must be mostly

204 ECONOMIC ZOOLOGY AND ENTOMOLOGY

done in the field, but some species readily live in artificial nests
prepared for them indoors. These nests can be so arranged
that much of the home life of the ants can be observed.

A simple formicarium, or ant nest, may be made by mounting
an inverted bell glass on a wooden block which is set like an
island in a shallow pan of water. Enough of the contents
(soil and ants) of a nest should be brought in and transferred
to the bell glass to fill it about half full. A cover of dark paper
or cloth should be placed around the bell glass as high as the soil
fills it, in such a manner that it may be readily removed at
times of observation. The ants in their nest building will
make some of their run ways and chambers next to the dark-
ened glass, and, by removing the cloth, may be seen at work.

Janet, a distinguished French student of ant life, uses a
block of porous earthenware in which several little chambers
or hollows have been made, connecting with each other by
little surface grooves, the whole covered with a glass plate,
and over that an opaque cover. Into a cavity at one end of
the block he puts water which soaks some distance along the
length of the block, thus rendering some chambers humid,
while others at the far end are dry. He gives the ants no soil,
forcing them to use the already made chambers. This formi-
carium reveals, therefore, none of the secrets of nest-building,
but it does reveal admirably a host of those interesting pro-
cesses connected particularly with the life history of the individ-
uals of the colony.

Miss Adele Field, an American student of ants, has devised
a nest (Fig. 93) in which glass is used for the base, outer wall
and partitions. A bit of sponge, kept moist, is placed in one of
the rooms. The glass base is double thick and placed on thick
white blotting paper for background, and the walls and parti-
tions are narrow strips of glass glued to the base with crockery
cement. On walls and partitions are glued strips of Turkish
toweling. On this is laid a thin glass roof frame for each room.
An outer removable roofing of blotting paper makes all the
interior of the nest dark, except the food room which should
not be covered as it represents the ants' outer world.

Sponge cake, apple, mashed walnut and the muscular parts

WASPS, ANTS AND BEES

205

of larvae of insects are among the ants' most liked edibles, says
Miss Field.

The extremely highly developed instincts of the social
Hymenoptera (social wasps, social bees and ants) have led to
their being called the most intelligent of insects. But as far as
our present knowledge goes we are not justified in attributing
any intelligence, in the strict meaning of the term, to any
insects. Their behavior is practically wholly controlled by
inherited instincts, which fit them to go through a certain life

FIG. 93. Plan of the Fielde ant-nest, ten inches by six inches, a, En-
trance and exit to food-rooms (i); 2, nursery; 3, sponge-room; b, screens;
m, passage.

routine very effectively, but which leave them helpless if by
any chance they are submitted to wholly new conditions.
Much experimental work has been done with the wasps, bees
and ants, to test their capacities for successful modifications of
their behavior, and the weight of authority is against admitting
their possession of real reason or intelligence. In this connec-
tion the books of Fabre, the French "Homer of insect life,"
those of the Peckhams, American students of solitary and
social wasps, and of Wheeler, the American student of ants,
should be read by students. They contain the most fascinat-
ing stories of insect life which can be written.

CHAPTER XIX
SCORPIONS, SPIDERS, MITES AND TICKS

The scorpions, spiders, mites and ticks, composing the class
Arachnida of the branch Arthropoda, are popularly regarded as
insects but they differ from the insects in several important
respects. They have four pairs of legs instead of three pairs,
the body is not divided into three well denned regions, as it is
in most insects, but into two, and they have no antennae.
There are also important differences in the respiratory system
and other internal structures.

The class is a large one including many diverse forms.

Scorpions. The scorpions, order Arthrogastra, are found
chiefly in warm regions. They are usually nocturnal, hiding
away under stones or in crevices during the day, and coming
forth at night to capture their prey, which consists chiefly of
insects and spiders. These they seize and hold with their large
pincer-like maxillary palpi and sting with the poison fang at the
end of the long narrow part of the abdomen. The first seven
segments of the abdomen are broad and flattened, but the last
five segments are narrowed, more rounded and whip-like. The
last segment bears the poison-fang or sting, the poison from
which is quickly fatal to most small animals. Some species
are quite poisonous to man, but the kinds found in the United
States, while they may inflict a painful sting, are not usually
dangerous.

Spiders. In the spiders, order Araneina, the abdomen and
the cephalothorax are very distinctly separated but the seg-
ments of each region are so closely fused as to be indistinguish-
able. The four pairs of legs vary in length according to the
habits of the different species; some are fitted for running,
others for jumping, others for walking over the ground or
grass or over delicately spun webs. The pedipalpi, or feet-

206

SCORPIONS, SPIDERS, MITES AND TICKS 207

like palpi, are sometimes one-fourth to one-half as long as the
legs. The mandibles, or chela, are large and terminate in a
slender sharp-pointed fang, through which poison flows when
a spider bites its prey. The bite usually quickly kills insects
and other small animals but as a rule does not seriously affect
A few species, however, are very venomous, and a bite

man.

from one of them may result in great suffering, rarely in

FIG. 94. Web of an orb-weaver, Zilla californica; the viscid threads are
omitted from part of the web; a trap-line runs from the center to a retreat
at one side. (Much reduced.)

death. The effect of a spider's bite does not depend altogether
upon the kind of spider, the condition of the victim's blood
being a considerable factor. Two people may be bitten by the
same kind of spider and one suffer little while the effect on the
other may be very serious. The most common of the very
poisonous spiders, and the only one to be much feared in this
country, is the "hour-glass" spider, or "black widow"
Latrodectes mactans. This is a small-sized sooty black

208 ECONOMIC ZOOLOGY AND ENTOMOLOGY

spider, the female of which has a round abdomen that is
marked on the underside by a bright red spot, usually hour-
glass shaped. The slender abdomen of the male has three
light spots or dashes along the median line and three or four
lateral stripes. The very young of both sexes have little
black on them and immature females are colored much like
the males. This species is cosmopolitan. In the United States
it occurs as far north as Massachusetts but is more common in
southern regions. These spiders are found in the fields on
plants or among loose stones and around houses in dark
corners or in boxes or rubbish.

The webs that spiders spin for traps to ensnare their prey or
to line their nests or to protect their eggs are made of silken
threads of various sizes. Some of these threads are composed
of several finer threads united. Spiders produce several kinds
of silk, one kind being always viscid and sticky. Most
spiders have three pairs of spinnerets, a few having but two
pairs, situated at the tip of the abdomen. On the ends of
these short finger-like spinnerets are many minute openings
through which the fine silken threads are drawn. These
openings lie in little papillae, called spinning spools and
spigots. When the tips of the spinnerets are placed close
together, the issuing threads all unite into a large strong
thread. If the spinnerets are held further apart the broad
silken bands are produced.

The great hairy tarantulas of our southern and western states
line their burrows with a thin layer of silk. The trap-door
spiders usually make a heavier lining sometimes dense and
tough, but with a smooth soft silken surface. The door that
these spiders make to guard the entrance to their burrow is
made of silk and earth, leaves, grass or moss, always resembling
closely the ground or ground-covering around it. The com-
mon black running spiders that often carry their egg sacs with
them and the stout-bodied little jumping spiders which leap
on their prey, spin but little web.

The sedentary spiders, or those which spin webs of various
sorts to capture their prey, include most of the common kinds.
The cob- web weavers, which are one of the trials of the house-

SCORPIONS, SPIDERS, MITES AND TICKS 209

keeper, the funnel-web weavers found in the woods and
meadows, and the various orb- weavers are all most interesting
and deserve more notice, but as they are of no particular
economic importance except as they destroy noxious insects,
they will not be discussed further here. The best book about
American spiders is "The Spider Book" by Professor J. H.
Comstock.

FIG. 95. Web of a grass spider, A galena sp. (Reduced.)

TICKS AND MITES (ORDER ACARINA)

From an economic standpoint the mites and ticks, consti-
tuting the order Acarina, are by far the most important mem-
bers of this class. The body is very compact, the cephalo-
thorax and abdomen being closely fused. This character
will serve to separate them from the spiders, the young of
which might be mistaken for mites.

Ticks. The ticks are all comparatively large, that is, they
are large enough to be seen with the unaided eye, even in their
younger stages, and some grow to be half an inch long. The
young when first hatched have only six legs but after the first

2io ECONOMIC ZOOLOGY AND ENTOMOLOGY

moult another pair appears. The sucking beak, which is
thrust into the host when the tick is feeding, is furnished with
many strong, recurved teeth which hold so firmly that the
head is often torn from the body and left in the skin of the host
when the tick is forcibly removed.

Ticks are wholly parasitic in their habits. Some of them
live on their host practically all their lives, only dropping
to the ground when fully mature to deposit their eggs. Others

FIG. 96. Castor bean tick, Ixodes ricinus, not fully gorged. (Magnified

about five times.)

leave their host twice to molt in or on the ground. The
female lays her eggs, 1000 to 10,000 of them, on or beneath
leaves and other litter on the ground. The young "seed-
ticks" that hatch from these in a few days, soon crawl up on
some nearby blades of grass or on a bush or shrub and
wait quietly and patiently until some animal comes along.
If the animal comes close enough, the ticks leave the
grass or other support and cling to their new found
host and are soon taking their first meal. Of course
thousands of them are disappointed and starve before their

SCORPIONS, SPIDERS, MITES AND TICKS 211

host appears, but as they are able to live for a remarkably long
time without taking food their patience is often rewarded and
the long fast ended. Those species which drop to the ground
to molt must again climb to some favorable point and wait
for another host on which they may feed for awhile. Then
they drop to the ground for a second molt and if they are
successful in gaining a new host for the third time they feed and
develop until fully mature and the female is ready to lay her eggs.

FIG. 97. Amblyomma variegaliim; several ticks belonging to the genus
Amblyomma transmit various diseases of domestic animals. (Magnified
about six times.)

The presence of even a few ticks on an animal is always a
source of annoyance and they often occur in such numbers as
to affect seriously some of our domestic animals. Chickens,
dogs, horses and cattle, all have their particular kinds of ticks,
some of which commonly attack man when the opportunity
offers. The bites of ticks often cause great pain. Sickness
and death sometimes follows the bite of some certain species,
but this probably only under exceptional conditions or when the

212 ECONOMIC ZOOLOGY AND ENTOMOLOGY

tick carries the parasite of some disease. Their chief impor-
tance, indeed, lies in the fact that they are concerned in the
transmission of several diseases that are caused by Protozoan
parasites. The Texas fever of cattle and the spotted or Rocky
Mountain fever of man are the most important of such diseases
in America. These will be discussed in Chapter XXVIII.

The chicken- tick, Argas persicus, is a very serious pest in
the southern states. It has a world-wide distribution, and in
Persia, where it has habits similar to the bed-bug, it is one of
the most dreaded pests, sometimes becoming so numerous
that the inhabitants desert the town rather than try to rid it
of the pests.

In Africa the most common tick, Orniihodorus moubata, lives
in the huts of the natives and has habits similar to the bed-bug.
Besides being a source of great annoyance it transmits a
disease known as relapsing fever which has at different times
been introduced into the United States, but has not become
established here.

Mites. The mites are much smaller than the ticks, so small
that they are not ordinarily seen unless one is searching for
them. Yet many of them make their presence destructively
or painfully evident, for they are not only important pests
of cultivated plants, but they attack man and domestic
animals.

Perhaps the best known of the mites is the "red spider"
of the greenhouses, Tetranychm bimaculatus, which is one of
the worst pests that occurs in such places. It is found out of
doors also and in some regions may totally defoliate almond
and prune trees and berry bushes and seriously injure many
other plants. These mites do not always have the character-
istic red color but during the time that they are feeding they
may be light or dark green with dark colored spots. This
species passes the winter in the ground. The usual method of
control is to dust the trees thoroughly with fine dry sulphur, or
the sulphur may be mixed with water, i Ib. to 5 gallons of
water, and applied as a spray. The fumes from the sulphur
kill the mites.

Another mite, Bryobia pratensis, also commonly called " red

SCORPIONS, SPIDERS, MITES AND TICKS 213

spider," often does much damage to fruit trees, particularly
on the Pacific Coast. The eggs are laid on the branches of
the tree, where they remain over winter, the young mites
issuing about the time the leaf buds open. They may be
controlled by spraying the eggs with the lime-sulphur wash
(see page 415) just before the eggs hatch in the spring, or by
spraying or dusting with sulphur. This same species is often
an important pest on clover and grasses and is then known as
the clover-mite. In the Mississippi Valley states they some-
times swarm into dwelling houses late in the fall. Dry sulphur
dusted around the windows and doors or other places where the
mites enter the house, or the free use of pyrethrum after they
have gained an entrance, will give relief.

Two other red spiders, Tetranychus mytilaspidis, and
T. sexmaculatus, are serious pests of citrus trees. They are
controlled by dusting the trees thoroughly with finely powdered
sulphur.

The blister-mites, Eriophyes, are minute whitish, grub-like
creatures that bore into the tissue of the leaves of many plants.
The pear-leaf blister-mite is perhaps the most important of
these. They spend the winter in the buds and as the leaves be-
gin to develop they make their way into the tissue, causing
green or reddish blisters. They may be controlled by spray-
ing during the late fall or early spring with kerosene emul-
sion diluted with five parts of water, or with the lime-sulphur
wash.

Of the mites that attack man, the young harvest-mites, or
"jiggers", are probably the most familiar. Normally these
little mites live on plants, but when opportunity offers they will
crawl on man or any other animal and burrow into the skin,
causing intolerable itching. Where these mites are trouble-
some, one should avoid sitting or lying on the grass or in
other places where they may occur. Harvest men and others
whose work exposes them to these pests may get some relief
by dusting sulphur in the underclothing and shoes, and
by bathing, using a strong carbolic or tar soap, as soon as they
return from the fields. Sulphur ointments are also used.
The minute, almost round, whitish mites, Sarcoptes scabiei,

2i 4 ECONOMIC ZOOLOGY AND ENTOMOLOGY

that cause the disgusting disease known as itch are seldom
found except on unclean people. These mites live normally
in the skin, often burrowing deep and causing intense itching.
Sulphur ointments and other washes are used as remedies,
but on account of their burrowing habits these mites are hard
to kill. Cleanliness will prevent infection.

Closely related to the itch-mite of man are several kinds
attacking domestic animals, causing mange, scab, etc. The

variety infesting horses burrows in
the skin and produces sores and
scabs, and is a source of very great
annoyance. These mites may also
migrate to man. Tobacco water
and sulphur ointments are used as
remedies.

Horses and cattle and other do-
mestic animals are also infested by
mites of the species Psoroptes com-
munis, which cause the common
mange. These do not burrow into
the skin, but live on its surface in

FIG. 98 Itch-mite, Sar- co i on i es , feeding on the skin and
copies scabiei, female, dor- . .

sal aspect. (Greatly mag- causing crusts or scabs. The m-
nified; after Fiirstenberg.) flammation causes the animal to

scratch and rub constantly, and

often results in the loss of much of the hair. Single animals
may be treated with sulphur ointments or with lime-sulphur
mixtures; where several are to be treated, dipping vats should
be used.

The mites, Psoroptes communis var. ovis, that cause scab in
sheep, are among the worst pests that sheep owners have to
contend with. Once introduced into the herd they spread
rapidly so that the whole flock may soon become infested. The
fleece of scabby sheep becomes rough and felted and is easily
rubbed or pulled off, often leaving the sheep very ragged and
sore. The most satisfactory treatment for scabby sheep is to
hand dip them or drive them through vats containing lime and
sulphur or tobacco mixtures.

SCORPIONS, SPIDERS, MITES AND TICKS 215

The common chicken-mites, Dermanyssus gallina, are about
i mm. long, light gray or whitish in color, but becoming quite
red when full fed. They hide away in any crack or corner
where they can find shelter during the day, and come out at
night to feed. When numerous they may be serious pests to
other animals as well as chickens. Cleanliness will prevent
infection. A thorough spraying with kerosene or strong
kerosene emulsion will kill all that are reached by the oil.
Whitewash helps some. A poorly constructed, badly infected
house should be burned. Smooth roosts supended on wires or
small iron rods afford few hiding places for the mites.

CHAPTER XX

OYSTERS, CLAMS, MUSSELS, OTHER MOLLUSCS,
AND THE SHELL-FISH INDUSTRIES

The oysters, clams, mussels and snails, the molluscs (branch
Mollusca) with which we are most familiar, have their soft
bodies protected by a firm outer shell which is formed of car-
bonate of lime. Bui the slugs, which are common in the garden
and in moist places the beautiful sea-slugs or nudibranchs,
which are found in salt water, and the cuttlefish and octopi,
which are also marine, all of which also belong to this branch,
are not protected by such a shell. In habits and distribution
the members of this branch vary as much as they do in structure
and general appearance. Many of the snails and slugs live
on land, feeding on live or dead and decaying vegetable tissue.
Most of the mussels live in fresh water, but all the other
members of the branch live in the sea, some at the surface,
others at moderate or great depths, many in the sand or mud of
shores and shallow bottoms.

The Fresh-water Mussels. A study of the fresh-water
mussel will give one a general idea of the structure of the typical
members of this branch. The two valves of the shell are held
together along the dorsal edge by the horny hinge-ligaments.
Toward the rounded anterior end there is, on each valve, a
prominent elevation, the nmbo, which marks the oldest part of
the shell, and from which extends a series of concentric lines
of growth. When the mussel is feeding in the bed of the stream
the anterior end is buried deep in the mud and only a little of
the posterior end is exposed. The valves are opened slightly
at the posterior end, and between them may be seen the edges
of the mantle that covers the soft body and lines the inside of
the shell. When one of the valves is removed it will be seen
that the mantle is attached to the inner surface of the shell a

216

hinge ligament v

right auricle

anterior aorta\ \
reno-pericardial aperture ^

renal aperture ^
i/t- n ita I a pert ure -.,

uinbone

stomach-
digestive

gullet-

cerebro-jilni nil g(

mouth -

anter adductor*'**
antur rttractur

x

filial ganglion

foot

intestine'"
typhlosole-'

gondd
FIG. 99. Dissection of a ii<

ventricle

f pericardium

rectum

f

/ kidney

^_,--dorsal palltal aperture
-- posterior aorta
post, retractor

post adductor
anus

...... visceral ganglion

exhalant si plum
super brcwichial e ham her

- right gill

inhalant

* shell

pal Hal groove

mantle

mantle cavity
Fresh-water mussel, I'nio sp.

OYSTERS, CLAMS, MUSSELS 217

short distance from the edge. The crease on the shell indicat-
ing this line of attachment is called the pallial line. Near the
anterior end of the inner surface of the valve is a rather large
distinct impression. This is the point of attachment of the
anterior adductor muscle. Just behind and above this is the
smaller impression of the anterior retractor muscle, and behind
and below it is the impression of the protractor muscle. At
the other end of the valve is the large impression of the poste-
rior adductor muscle and the small impression of the posterior
retractor muscle. The anterior and posterior adductor muscles
extend from one valve to the other and when they contract
the edges of the two sides of the shell are held close together.
When these muscles are relaxed the valves are opened slightly
by the strong hinge ligament which is stretched tightly when
the valves are closed. The retractor and protractor muscles
govern the movement of the foot.

Where the mantle covers the body it is a thin delicate mem-
brane, but the free part, below the pallial line, is somewhat
heavier, and the edges are thicker. At the posterior end the
thickened fringed portions of the two mantle lobes form two
short tubes, the inhalant and exhalant siphons. The cilia on
the fringes of the mantle cause a current of water to flow in
through the lower or inhalant siphon into the mantle cavity,
the space inclosed by the mantle lobes. Here the water bathes
the inner surface of the mantle and the gills, and passes
through the gills to a space just above them known as the
supra-branchial cavity. In this space it passes backward again
and out through the upper or exhalant siphon. The mantle
is an important organ of respiration, for as in the gills of fishes,
oxygen is taken from the water and carbon dioxide passed out
through its thin delicate walls. The shell is the product of the
secretions of the mantle. Over its whole surface the mantle is
constantly secreting a thin layer of carbonate of lime which
serves to thicken the older parts of the shell and to extend and
harden the thin soft margins.

When the mantle is removed from one side of the body the
large muscular foot, the thin delicate leaf-like gills and the soft
visceral mass of the body are exposed. The foot is large and

2i8 ECONOMIC ZOOLOGY AND ENTOMOLOGY

quite firm, somewhat triangular in shape, and is capable of
being extended beyond the edges of the shell for a considerable
distance. It is by means of this organ that the animal plows
its way through the mud or sand in which it lives. The gills
are two pairs of flattened, ribbed, membranous folds which hang
down into the mantle cavity from each side of the body. The
water bathing these gills and passing up between them comes
in very close contact with the minute blood-vessels with which
the gills are abundantly supplied so that the transfer of gases
from the water to the blood and from the blood to the water
can readily take place. The body is not divided into well-
defined regions. Just below and back of the anterior adductor
muscle is the mouth opening. On each side of it, looking some-
what like little gills, are two pairs of labial palpi whose function
it is to convey to the mouth the minute plant or animal organ-
isms that are carried in by the water. Through a short esopha-
gus these particles, which are the food of the mussel, pass
into a rather large stomach and from that into a long narrow
intestine which is coiled in the base of the foot and the visceral
mass. The posterior part of the alimentary canal, the rectum,
is a long straight tube extending through the pericardium and
opening into the supra-branchial cavity close to the exhalant
siphon.

The pericardium is the space in the upper portion of the
visceral mass just below the hinge-ligament. It is covered by
a delicate membrane, and contains the heart and some of the
blood-vessels. The heart consists of a single ventricle, which
surrounds part of the rectum, and a right and left auricle.
When the ventricle contracts it sends the blood forward and
backward through large blood-vessels, the anterior aorta and
the posterior aorta. Part of the blood is carried directly to the
mantle where it is aerated and then returned to the heart. The
rest of the blood is carried to various parts of the body and
finally collects in a space, the vena cava, just beneath the peri-
cardium. From the vena cava the blood passes into the excre-
tory organs, the kidneys, which lie just beside it, and on down
into the gills and finally back to the heart where it enters the
auricles.

OYSTERS, CLAMS, MUSSELS 219

Instead of a series of ventral ganglia and a more or less
specialized brain as is found in the insects, worms and some
other invertebrates, the nervous system of the mussel consists
of three scattered principal groups of ganglia connected by
nerve cords. Lying one on each side of the esophagus are the
cerebro-plenral ganglia. They are connected with each other
by a nerve which passes over the esophagus, and by larger
nerves with the pedal ganglion in the foot and the visceral
ganglion which lies near the posterior adductor muscle.

The sexes of the mussels are separate, that is the ova and
spermatozoa are produced in different individuals, but the
reproductive glands, or gonads, of the two sexes are very similar.
They form a glandular mass of tissue filling the base of the foot.
The ducts from the ovaries and testes open near the base of the
gills. The spermatozoa are carried from the body with the
water that passes out through the exhalant siphon, and find
their way to another mussel with the incoming water currents.
The eggs pass into the supra-branchial chamber, but instead of
passing on out of the body remain there until they are fertilized
by the spermatozoa from another individual. They then
drop down into the outer gills, which serve as brood chambers.
Here the young are held for some time, and develop bivalve
shells which enclose them. In some species the margin of the
shell is provided with stout hooks, but in others it is without
them. Thus armed, the young, or glochidia, as they are called,
pass into the water. When touched the shell closes quickly
and firmly. If the young come in contact with the fins or gills
of a fish the snapping shut of the shell may serve to attach them
to it. The forms with hooks on their shells are more often
found on the fins of the fish, the hookless kind on the gills.
Once attached, their presence causes an irritation of the tissues
of their host which results in a growth or cyst that soon covers
them over. In this condition they remain for some time,
drawing their nourishment from the host and undergoing the
transformations that change them to small mussels which fi-
nally drop to the mud where they continue their growth, feed-
ing on small organisms, both plant and animal, which are
taken from the water entering the mouth cavity. The

220 ECONOMIC ZOOLOGY AND ENTOMOLOGY

knowledge of this relation of the fish to the mussel is of prime
importance in the attempts that are being made to restock
some of the mussel beds that have been depleted on account
of the increased demand for the shells for the making of
pearl buttons.

Mussels and Buttons. Until about 1891 no use was made
of the shells of fresh-water mussels. But at this time it was
found that excellent pearl buttons could be made from these
shells, and so there has sprung up an industry spread through-
out the central part of the United States that has a value of
more than $6,000,000 annually and gives employment to
hundreds of people. The Government has established a station
for the propagation of mussels in order that depleted streams
may be restocked and new areas made productive. Mussels
containing the developing glochidia are teased up in water and
this water is poured into tanks containing fish. When their fins
and gills are well covered with the glochidia the fish are liber-
ated in the streams that are to be stocked with the mussels.

Mussels and Pearls. In an earlier chapter reference has
been made to the fact that pearls are produced in many mol-
luscs by the pearly nacreous substance, of which the shell is
formed, being deposited around certain parasitic worms that
are found in the body of the animal. When such secretions
are irregular in shape they are usually called baroques, or slugs.
When round or pear-shaped, or of some other regular shape,
they are called pearls.

It is not an uncommon thing to find baroques or slugs in the
fresh-water mussels, some of them very beautiful. These are
usually formed around certain parasitic flat worms, a
Distomid having the muskrat or otter as one of its hosts, being
a common form.

Perfect round pearls of delicate luster and great value are
also often found. Recent investigations have shown that the
egg or the dead body of a small water-mite may form the nu-
cleus around which the pearl is formed, the most perfect
pearls probably being formed around the eggs. These mites,
Unionicola (A tax), liveparasitically in the gills or mouth cavity
of the mussel, and when they lodge in the tissues in such a way

OYSTERS, CLAMS, MUSSELS

221

as to cause irritation, the mussels, as a means of protection,
cover them over with the pearly layer. These pearls vary in
value from a few cents or dollars up to hundreds of dollars.
Perhaps the most famous of all the fresh-water pearls is the
"Queen Pearl," which was found in a New Jersey stream in
1857. It was sold by the finder for $1500, but is now valued
at about $10,000. Occasionally some particularly valuable
pearls will be found in a new region, and during the "pearl
fever" that follows, thousands of 1
dollars worth of pearls may be
found, but the mussel beds of the
streams are usually almost or
quite depleted. Formerly the
shells thus gathered were left on
the bank to disintegrate, but
they are now used in the impor-
tant button industry.

Fresh-water mussels are some-
times used for food. The great
shell heaps, or "kitchen mid-
dens," found in many places
show that they must have
formed an important part of the
food of the early inhabitants of
this and other countries

Classes of Mollusca. The
branch Mollusca (L. mollis, soft)
is divided into five classes. The
class Pelecypoda (Gr. pelekys, axe,
POUS, foot) is the largest and most important group, including
the mussels, clams and oysters and others that furnish an
abundance of cheap, palatable and nutritious food. The name
Pelecypoda means "hatchet-foot," and refers to the fleshy foot
or organ that enables the clams and mussels to dig or plow
their way through the mud. The name Lamellibranchia, re-
ferring to the lamella-like gills on each side of the body, was
formerly used for this class. As all the members of the class

FIG. ioo. A chiton, Isch-
no chit on magdal enc n s is .
(Reduced.)

222 ECONOMIC ZOOLOGY AND ENTOMOLOGY

are inclosed in a shell composed of two parts or valves they are
commonly referred to as bivalves.

The class Gastropoda (Gr. gaster, stomach; pous, foot) in-
cludes the snail, slugs, periwinkles and many other molluscs
that are either naked or furnished with a shell composed of a
single piece.

The Cephalopoda (Gr. kephale, head; pous, foot) include
squids, octopi, cuttlefish and the nautilus.

The members of the classes Amphineura (Gr. amphi, around;
neuron, nerve) and Scaphopoda (Gr. skaphe, hollow; pous, foot)
are much less common and are of little or no economic impor-
tance. The first includes the chitons, which have segmented
shells and are fairly common on rocks on the California coast.
The tooth-shells sometimes found along the northern sea
beaches belong with the peculiar somewhat worm-like mem-
bers of the class Scaphopoda.

CLASS PELECYPODA

The Mussels. They are many genera and species of fresh-
water mussels, and they are to be found in suitable streams
and lakes in almost all parts of the United States. Their life
history and importance have just been discussed. The salt-
water mussels differ from those in fresh water in several
respects, the most noticeable of which is in shape and in the
presence of a number of fine tough threads, the bysstis, which
serve to attach the mussels to rocks or other substances on
which they are growing. These mussels often occur in great
masses over the rocks and piles or on tide flats wherever they
can find a place to attach themselves. They are often serious
pests on oyster beds, occurring in such numbers as to smother
the oysters or starve them by taking a large part of the food
that would otherwise go to the oysters. The salt-water mussels
are often used for food, and can advisably be thus used more
than they are at present. They occur in abundance on both
Atlantic and Pacific coasts of our country, and are easily
gathered at low tide.

Clams. In most of the clams the portion of the mantle that
forms the siphons in the mussels is especially developed and

OYSTERS, CLAMS, MUSSELS

223

produced into a long neck-like process. This enables the clam
to bore into the mud or sand for some distance and still
keep the end of the siphon in the water. Those who have
never been near the sea-shore where they could take part in a
clam-bake have at least enjoyed their clam chowder in their
inland homes even if it were made from the canned article.
Hardly a beach along any of our coast lines but furnishes an
abundance of one or more species of clams. Along the North
Atlantic coast the soft clam, Mya arenaria, is one of the most

FIG. 101. The common sea-mussel, Mytilits edulis L. (Reduced.)

important of the clams. At one time it occurred in seemingly
unlimited numbers, but on account of wasteful and destructive
methods of gathering them many of the best beds are now
nearly depleted. Most of these tide flats may be made to
yield abundant supplies again under the methods of cultiva-
tion and protection that are now being adopted in some
places.

The hard clam, or quohog, or little-neck clam, Venus
mercenaria, is the most important clam from New York south-
ward. Unlike the soft clam, whose shell is comparatively
light and often does not close tightly along the edge, the hard
clam has a heavy shell that closes very firmly.

224 ECONOMIC ZOOLOGY AND ENTOMOLOGY

Other species of clams and two or more kinds of scallops,
Pecten, occurring along the Atlantic coast, are used for food.
The scallops differ from the clams in having deep grooves
radiating from the hinge to the edge of the shell. Some are
beautifully colored. The meat of many of them is very dainty.

The soft clam has been in-
troduced into the waters of
the Pacific Coast States, doubt-
less with the shipments of
eastern oysters. There it is

FIG. 102 . S o f t-s h e 1 1
clam, Mya arena ria L.
(Reduced.)

FIG. 103. A geoduck or
giant cla.m,Glycimeris gcncrosa,
which attains a weight of five
or six pounds. (M u c h
reduced.)

known as the "eastern" clam, but has not yet found
much favor in the markets because there are several native
species that are more in demand. One of the most common
of these is the hard shell or little-neck, Tapes staminea,
which seems to take the place of the hard clam of the east
coast. The great Washington clam, Schizothasurus nuttalli, and
the butter-clam, Saxidomus nuttalli, are common in many
places on the northwest coast. One of the most remarkable
clams in the United States is the giant "geoduck" (earth
duck), Glycimeris generosa, which sometimes weighs as much as

OYSTERS, CLAMS, MUSSELS 225

six pounds and has a siphon that may be extended eighteen to
twenty-four inches. The body is very large, but the shells are
so small that they only cover the sides of the clam and the
great white mass that extends beyond the shells and the long
siphon looks not unlike the breast and neck of a duck, the
shells representing the folded wings.

In the hard, smooth, wave-beaten, sandy beaches of the
North Pacific are to be found the "razor-clams," Machera
patula, which are undoubtedly the finest of all the clams.
The meat is white and tender and most delicately flavored.
The canneries that have been established along the coast are
fast depleting the supply of these choice clams.

Oysters. Much more important than the clams, though
less numerous, are the oysters, two species of which occur
along our coasts and are used for food. Some of the most
extensive natural beds occur in Chesapeake Bay, but other
beds are found as far north as Prince Edwards Island and as
far south as the Gulf States. Many excellent beds are found
in Long Island Sound. The eastern oyster, Ostrea virginiana,
is unisexual, that is, the ova and spermatozoa are produced in
different individuals. During spawning season the female
produces sixteen to sixty millions of ova which are set free in
the water to meet by chance the spermatozoa from the male.
If this union takes place, the ova are fertilized and soon lose
their original pear shape and become quite round. If they
are not fertilized they soon perish. Within two or three hours
after fertilization these ova, which are single cells too small to
be detected with the unaided eye, begin to divide, and in two
hours more have changed from single round cells into masses
of cells, the masses themselves being rounded and about the
size of the original egg cell. A little later, small thread-like
projections, or cilia, begin to appear on one side. The embryos
have now reached the swimming stage, for by means of these
cilia they are able to move about through the water at will.
They remain in this stage from three to six days, or until the
shells have begun to form, when they sink to the bottom, and,
if they are fortunate enough to strike some suitable hard object,
they become attached and begin to take on the character of an
is

226 ECONOMIC ZOOLOGY AND ENTOMOLOGY

adult oyster. From this time on the young oysters are less
exposed to danger, but the number of them that reach maturity
is very small when compared with the number that perish or
are destroyed in one way or another.

The young oysters when first attached are called "spat";
when a little older this spat, now called " seed," may be trans-
planted to new beds, which are stocked in this way.

FIG. 104. Young (spat) of the west-coast oyster, Ostrea lurida, attached

to rock. (Reduced.)

In some regions clean shells or other " cultch" are distributed
over the beds just before the spawning season in order that
there may be plenty of clean hard surfaces for the young em-
bryos. The oysters are ready for market in from three to five
years, and are gathered from their beds by means of long-
handled tongs or dredged up by means of dredges and power

OYSTERS, CLAMS, MUSSELS 227

boats. It has been estimated that more than twenty-five
million bushels of oysters are gathered from the beds in the
United States each year.

The west-coast oyster, Ostrea lurid a, is much smaller than
the eastern oyster and has a much thinner shell. It differs also
in being hermaphroditic and viviparous; that is, both ova and
spermatozoa are produced in the same individual and the eggs
are fertilized in the gill and mantle cavities and here also they
pass through the early stages of development. At spawning
season, when these young embryos are set free, they have
already reached the swimming stage and are soon ready to
attach themselves to some convenient shell or other collector,
where they remain fixed through life.

The area available for oyster cultivation is much less on the
Pacific coast than on the Atlantic, but the total output of
oysters from the state of Washington amounts to about
$300,000 annually. Many years ago shipments of eastern
oyster spat or seed were made to the Pacific coast and planted
in San Francisco Bay where they were allowed to remain until
they reached a marketable size. Now many carloads are
shipped from the east each season and planted on the tide flats
in California and Washington, the introduced oysters attaining
a good size and a flavor hardly excelled in their native waters.
On account of the low temperature of the water during the
spawning season most of the young of the eastern oyster are
killed while they are swimming at the surface, and so the beds
of eastern oysters have to be replanted when the marketable
oysters are removed.

There are two common species of oysters native to Europe.
The smaller flat oyster, Ostrea ednlis, occurs along the northern
shores, and in many respects resembles our Pacific coast oyster.
Like the latter it is hermaphroditic. The Portuguese oyster,
O. angulata, is found on the southern shores and resembles
more our east-coast oyster in size and methods of breeding, but
is not so highly esteemed for food as the smaller northern
oyster.

The European oysters have been cultivated since the earliest
times, and in many places the collecting of the spat on especi-

228 ECONOMIC ZOOLOGY AND ENTOMOLOGY

ally prepared collectors, the transplanting and caring for the
seed and the final marketing of the oyster after it has been
fattened and often flavored to suit the taste of a fastidious
public, furnishes employment to many people along the sea
coasts.

Many other species occur in other parts of the world, where
they are usually important articles of food.

Shell-fish and Disease. In feeding, the oysters, clams and
mussels may take into their body any minute particles that are
to be found in the water where they are lying. Thus it will be
seen that any impurities that are in the water may readily
affect the bivalves living in it. It sometimes happens that
oyster or clam beds are situated so near the outfalls of sewers
from some city that the water is always polluted. Shell-fish
coming from such places are usually plump and look most in-
viting, but as they may contain typhoid germs and other dan-
gerous organisms they are to be avoided. The interest that
has been aroused in this subject during the last few years has
been the cause of much careful study, and, while the danger is a
very real one, the rigid supervision that is now kept over many
of the sources from which this important food supply comes,
makes most shell-fish safe. If they are thoroughly cooked
before being eaten the harmful organisms are destroyed. Oy-
sters that have been "freshened" or bloated by being trans-
ferred to fresher water for a few days or hours should never be
eaten raw, as the places where this process is carried on are too
often in dangerous proximity to sewer outfalls. A strong
public sentiment against such practice will insure its discon-
tinuance.

Pearl-oysters. The "pearl-oyster" of the South Seas is
really not very closely related to our oysters. It is more of the
shape of our common pectens, and has a strong byssus by
which it attaches itself, at least during its earlier stages, to
rocks or corals. The shell of some species is quite heavy, and
the wonderfully iridescent inner layer is known as " mother-of-
pearl." The pearl-shells form an important article of com-
merce, as the mother-of-pearl is used in the manufacture of
many articles. The pearls themselves, which are formed in

OYSTERS, CLAMS, MUSSELS

229

the same way as that already described for the fresh-water
pearls, may have, when large and of perfect shape and luster,
a very great value. The recently attained perfection in the
making of imitation pearls may somewhat lessen the market
value of true pearls, but the pearl-fisheries are still of great
importance.

For more than two thousand years Ceylon has been the
center of the pearl-fisheries industry, but many valuable pearls
and much better mother-of-pearl shells are found in the waters
of other tropical islands.

FIG. 105. Inner side of a pearl shell. (Reduced).

Teredos. Very unlike any other members of this class in
general appearance and habits are the teredos or ship-worms
that so often do great damage to any timber that is in salt
water. The young teredo is a free-swimming embryo like the
young of other molluscs, but it soon settles on some piece of
submerged wood and begins to burrow into it. As it grows
and develops its small bivalve shell, it bores deeper into the
wood, lining its burrow with a shell-like calcareous deposit.
As the ends of the siphons are kept close to the entrance of
the burrow, the animals soon become very much elongated and

2 3 o ECONOMIC ZOOLOGY AND ENTOMOLOGY

worm-like, and indeed are more commonly thought to be worms
than bivalve molluscs. They bore into the wood only for
protection, and do not feed upon it. Their food consists of
minute organisms that are taken into the body through the
siphons.

Teredos are very serious pests on the piles of wharves, and
on dykes, ships' bottoms and any other wood that comes in
contact with salt water. In some places they are so abundant
that a two-inch plank may be completely honey-combed and
destroyed in less than a year. The only protection is to cover
the wood with some substance which the teredo cannot or will
not penetrate. Heavy coatings of copper or verdigris paint
are often used, but they must be reapplied frequently. Cer-
tain other Pelecypod molluscs have the remarkable habit of
boring into solid rocks far enough to protect them.

CLASS GASTROPODA

Snails. Snails are very common objects in water and on
land. They all have shells, which may be conical or spire-
shaped or flattened. The most common snails have spiral,
more or less cone-shaped shells. One group, the pulmonate
snails, including many common aquatic and terrestrial forms,
do not breathe by means of gills as do most other molluscs.
On the right side of the body near the anterior end is an exter-
nal opening that leads into a sac, the so-called "lung." The
inner surface of this sac is abundantly supplied with fine blood-
vessels through the walls of which oxygen is taken from the
air and carbon dioxide thrown off. These snails are vege-
table feeders and are sometimes serious pests among flowers
and in the garden.

The members of another group of common pond snails
have gills and no lung-sac. These live on the bottom of the
ponds and feed on animal rather than vegetable food.

Most of the snails and the slugs have two pairs of " horns 1 '
with the eyes on the tips of the second pair. Some snails have
only one pair, which are used as feelers, the eyes being situated
at the base of these feelers.

OYSTERS, CLAMS, MUSSELS 231

Slugs. The small slimy slugs that are often so common in
moist places are very serious pests in vegetable and flower
gardens. They hide away in some cool, dark place during the
day, and at night come out and feed upon any succulent plants
that they can find. They do particular damage to early young
plants, often destroying them as fast as they come up. No
very efficient remedy has been suggested, but their numbers
may be somewhat reduced by one or more of the following
methods. The ground around the plants should be examined
for the slugs, which may easily be destroyed. If ashes or air-
slaked lime is then spread about the plants the slugs will not
bother them as long as the ashes or lime remains perfectly dry

FIG. 106. The giant yellow slug of California, Ariolimax californica.
(This slug reaches a length when outstretched of twelve inches.)

and does not form a crust over which the slugs can crawl.
Boards or stones afford good hiding places and may be placed
in the garden as traps to be examined each day. Lettuce or
cabbage leaves thrown on the ground are attractive baits and
are also good hiding places which can be easily examined every
morning. If the plants are examined at night with the aid of
a lantern many of the slugs may be found and destroyed.
Spraying with arsenate of lead or kerosene emulsion does some
good, the first poisoning the slugs, the latter killing those that
it touches and being more or less effective as a repellent.

Marine Gastropods.: Hundreds of shell-forming Gastropods
are found along every sea-shore. These present a wonderful
variety of shape and size and color. Some of them are most
beautifully colored and fantastically shaped. The great cow-
ries with their delicately colored porcelain-like shells, the lim-

2 3 2 ECONOMIC ZOOLOGY AND ENTOMOLOGY

pets so common on the rocks everywhere, the helmet-shells
from which cameos are cut, and hosts of others all belong to
this group. The large sea-snails and the much smaller but
more numerous drills (family Muricidce) are often of serious
economic importance. The sea-snails bore holes by means of
their roughened tongue-like organ, the radula, and an acid
salivary secretion through even the thickest-shelled clams, and
suck out the soft body of the victim. The oyster-drills, of the
genus Urosalpinx and of other genera, drill holes through
the oyster shells in the same manner, and as they often occur in
great numbers on the oyster beds they may destroy many
oysters. Some of them have a habit of collecting in great
masses at their breeding season, and are sometimes gathered

FIG. 107. Two kinds of oyster-drills; large one, Polynices
Gould; small one, Thais lamcllosa. (Reduced.)

and used for food. Many Muricida when crushed exude a
reddish-purple fluid which in olden times was used as a dye
famous under the name of Tyrian purple.

Abalones, or ear-shells, which are particularly abundant
along certain parts of the California sea-coast, are of interest
because of their economic importance. The animal lives
attached to a rock by a great muscle which fills most of the
firm ear-shaped shell that covers it. The outer side of the
shell is rough and dull-colored but the inner surface is smooth

OYSTERS, CLAMS, MUSSELS

233

and wonderfully irridescent. It is much prized for making
buttons and for other purposes for which mother-of-pearl
is used. Very beautiful and valuable baroque pearls are some-
times found in the abalones. The meat is dried or canned
and used for stews or chowder. Large quantities of dried or
canned abalone meat are shipped each year to China.

The nudibranchs or sea-slugs are doubtless the most beauti-
ful of all the molluscs. They are without a shell, and the
gills are usually in the shape of delicate, freely projecting tufts
often arranged in rows along the back. The gills, and indeed
the whole animal, are often most strikingly and beautifully
colored.

FIG. 108. Three Pacific coast nudibranchs; Doris tuberculata (in
lower left-hand corner), Echinodoris sp. (upper one), and Triopha modesta
(at right).

CLASS CEPHALOPODA

Squids, Cuttlefishes and Octopi. Both in habits and
structure the squids, cuttlefishes and octopi, or "devil-fishes,"
differ greatly from the other members of this branch. Most
molluscs move but little or not at all except as larvae, but the
Cephalopoda are very active all their life, swimming swiftly
through the water. The name Cephalopoda refers to the fact
that the foot assumes the appearance of a number of arms or

234 ECONOMIC ZOOLOGY AND ENTOMOLOGY

appendages of the head. The head is more or less definitely
set off from the rest of the body. The eyes are large and highly
developed. The main part of the foot is composed of a series
of eight or ten freely movable tentacles or "arms" surrounding
the mouth. These arms are provided with numerous sucker-

FIG. 109. A devil-fish, Polypus a poll yon. (Much reduced.)

like discs which enable the animals to hold fast to the rocks or
to catch and hold their prey, for they are all carnivorous.

The devil-fishes, genus Octopus (Polypus), have only eight
arms and so are known as Octopods. These arms or tentacles
may attain a length of fifteen feet or more, and with their great
sucker-like discs form very effective means of offense or de-
fense. The body is sub-spherical and without a shell. Their

OYSTERS, CLAMS, MUSSELS 235

terrifying appearance has been the basis for many weird sea
tales. The argonaut, or paper-nautilus, Argonauta argo,
secretes a beautiful thin shell for the protection of the eggs.
The cuttlefish, or sepias, and the squids, have in addition
to the eight arms of the Octopods, two other long slender

FIG. no. A squid, Loligo opalcsccns juv. (Reduced.)

arms, with suckers near the ends only, and so are known as
Decapods. The body is longer and better fitted for swimming.
Some of the squids attain enormous size, having a body-
length of twenty feet and arms thirty to thirty-five feet long.
The smaller squids are often very numerous and are commonly
used for bait by the fishermen of many regions. The cuttlefish

236 ECONOMIC ZOOLOGY AND ENTOMOLOGY

have in their body a horny calcareous substance known as
the "bone" or "pen." This is the cuttlefish bone that is
used to feed canary birds. True sepia ink is also a product
of these creatures. The ink is a dark secretion which the
cuttlefish discharges when it is irritated or frightened.
This clouds the water and allows the animal to escape from
its enemies.

The chambered pearly nautilus, genus Nautilus, belongs to
the only living genus of a group which was much better
represented in former geologic times.

CHAPTER XXI

FISHES AND FISHERIES

With this chapter we begin the discussion of the last and
highest branch of the animals. The branch is more commonly
known as the vertebrates, because all except a few of the lower
forms in it possess a backbone made up of a number of sepa-
rate vertebrae. This character separates them from all the
other animals that we have studied. Those forms that do
not have a vertebral column have, in common with the
vertebrate forms, in some stage of their development, apeculiar
structure called the notochord, which consists of a series or cord
of cells extending longitudinally through the body just below
the spinal nerve-cord. The presence of this notochord and
of gills in the neck region are about the only claims some of
the members of the branch have to be classed with the verte-
brates, and it is on account of the notochord that the name
Chordata has been given to the branch.

The branch is divided into nine classes of which the members
of five are familiar while those of the other four are strange
small marine animals not at all popularly known. In the
class Adelochorda (Gr. adelos, concealed; chorde, cord) which
includes the worm-like Balanoglossus, the notochord is im-
perfectly developed and for this reason some zoologists do not
consider it as belonging to the Chordata. These animals
occur only in certain places in the sea and are of particular
interest only to special students or investigators. In the
class Urochorda (Gr. oura, tail; chorde, cord), of which the
ascidians, or sea-squirts, are common examples, the notochord
is present only in the larval stage. The ascidians when born
are free-swimming tadpole-like creatures with a short noto-
chord and a fairly well-developed nervous and digestive
system, eyes and auditory organs. These larvae soon attach

237

238 ECONOMIC ZOOLOGY AND ENTOMOLOGY

themselves to a rock or some other firm substance, and all of
their organs become very much reduced and simplified. The
adult ascidian is a degenerate, sac-like organism looking as
much like a plant as an animal, and showing in no way the
relation to the vertebrates that is suggested by the larva.

As these two classes are so unlike each other and so different
from the vertebrates they are often considered as two distinct
subbranches of the Chordata and all the other classes are
included in a third subbranch, the Vertebrata. In almost all

FIG. in. An ascidian or sea-squirt from the coast of California.

(After Jordan and Kellogg.)

of the Vertebrata, the notochord, which is present in the early
stages of development, is replaced, in the later stages, by 'a
cartilaginous or bony backbone or spinal column.

The class Leptocardii (Gr. Icptos, small ; kardia, heart) includes
the primitive lancelet, in which the notochord is persistent and
unsegmented. Lancelets occur in the sand in shallow water

FISHES AND FISHERIES 239

along the Atlantic seacoast. They are slender, translucent
little creatures of very lowly organization.

The class Cyclostomata (Gr. kyklos, circle; stoma, mouth)
includes the lampreys and hag-fish, slender, eel-like forms hav-
ing a sucker-like mouth but no jaws. The lampreys, genus
Petromyzon, occur in both fresh and salt water, those living
in the sea ascending rivers to spawn. They sometimes attach
themselves to fishes by their sucker-like mouth and rasp the
skin and suck the blood. In this way they are of economic
importance as they may thus destroy some of the food fishes.
The hag-fish may burrow into the abdominal cavity of other
fish and devour the entire flesh and viscera in a short time.

The other five classes are the familiar ones of the Pisces
(L. piscis, fish), or fishes, Amphibia (Gr. amphi, on both sides;
bios, life), or frogs, toads and salamanders, Kept ilia (L. repo,

FIG. 112. A lamprey, Pctromyzon marinas. (After Goode.)

to creep), or turtles, snakes and crocodiles, Aves(L. cm, bird),
or birds, and Mammalia (L. mamma, breast), or mammals.
The fishes constitute the largest class of vertebrate animals,
about 13,000 species being known, 3000 of which live in North
America. They occur in almost all ponds, lakes and streams
and in the ocean, and vary in size from the great basking shark,
Cetorhinus, which reaches a length of thirty-six feet, to the dwarf
goby, Mistichthys, which is less than half an inch long. Be-
tween these extremes is found every variety in size, form
and relative proportions. The body may be greatly elongated
and almost cylindrical as in the eels, or long and flattened
from side to side as in the ribbon-fishes, or globe-shaped as
in the globe-fish.

24 o ECONOMIC ZOOLOGY AND ENTOMOLOGY

In habits too they differ as much as in size and shape.
Some live only in quiet ponds or lakes, others occur in the
swiftest mountain streams; some live only in fresh water,
others in the brackish waters of the bays or the salt water of
the sea. Certain kinds live close to the surface of the water,
others at moderate depths and still others in the deepest
parts of the ocean.

General Form and Structure. A typical fish, such as a sun-
fish or perch, has the body more or less pointed, the sides
somewhat flattened, the head wedge-shaped, and in many
other ways shows a body formed for moving rapidly through
the water. Most fish have the body covered with scales, al-
though many have the skin naked or covered with small scales
so hidden in the skin as to be hardly visible. The scales are
small horny or bony plates, outgrowths of the skin, which
usually overlap each other like shingles. The number, shape
and size of these scales are characters that are much used by
ichthyologists in classifying fishes. Three regions of the body
may be recognized, the head, the trunk and the tail, the latter
comprising that part of the body beyond the anal opening.
On the head are two usually conspicuous eyes set in protective
sockets. There are usually no eyelids, the skin of the body
being continuous, but transparent, over the eyes. Fishes are
near-sighted and vision is probably not very precise, although
the trout and some others seem to possess a very keen eye-
sight. In some of the deep sea fishes and in some cave-dwell-
ing species the eyes are rudimentary or wanting.

The mouth in most fishes is comparatively large and trans-
verse, and the jaws usually bear numerous teeth that enable
the fish to bite or hold their prey. Some fishes, however,
have the mouth small and round and fitted for sucking rather
than biting, and many have few or no teeth.

The nostrils are paired openings usually situated in front
of the eyes. They end in a pair of nasal sacs and do not
open into the roof of the mouth as they do in mammals, and
so have no relation to breathing. The sense of smell is rela-
tively acute in most fishes. On each side of the head is a
flap-like gill-cover, or opercnlum, the posterior margin of which

swim-bladder

lilii nil l/nr
(il>fr(-nl(ir jiup \

nostrils

jx r/riirilnil rtivily

'ventricle

caeca

_

\ intestine
\

\

limit} en rit t/
Fin. 113. Dissection'

opening from kidneys

lux/I/ );/(/,sT/r.s'

tionof the golden sunfish.

FISHES AND FISHERIES 241

is free so that water may be taken in at the mouth and pass
out through the gill-openings. The gills consist of a series
of slender filaments attached to bony arches. In these fila-
ments a supply of blood is constantly circulating in fine
capillaries through the walls of which carbon dioxide is given
off and a fresh supply of oxygen taken from the water that is
flowing over the gills. In some of the sharks and in some of
the flat rays that lie on the sea-bottom a pair of spiracles or small
openings occur behind the eyes. These open into the mouth
and the water can pass in through them instead of through the
mouth-opening. On the head of some fishes are to be found
soft pendulous filaments, sharp spines, or other appendages.
On the trunk usually occur two pairs of paired fins and two or
more unpaired fins.

Just back of the gill-openings are the pectoral fins, which
are homologous with the fore limbs of the other vertebrates.
On the ventral side of the body is another pair of fins, the
pelvic fins, which correspond to the hind limbs. The pelvic
fins may be placed well forward, almost under the head, or
well back on the body. The unpaired or median fins consist
of the dorsal fin above, the anal fin below, and at the posterior
end of the body, the caudal fin, or tail. Salmon and trout,
and a few other fishes, have in addition to these a small, soft
adipose fin between the dorsal and caudal fins. The median
fins are folds of the skin of the body supported by more or less
firm rays. The stiff unjointed rays are known as spines and
the others, which are softer and made up of little joints, are
called soft rays.

The stiff sharp spines in the paired median fins are often
very effective weapons of defense as a wound made by them
may be very severe, particularly when made by the spines with
serrated or ragged edges. Some of the scorpion-fishes and
others secrete a poison which is introduced into the wound
made by the spine.

Along the side of most fishes, extending from the head to
the caudal fin, is a series of modified scales which mark the
lateral line. This lateral line is subject to considerable varia-
tion in regard to its position and structure. In connection

16

2 4 2 ECONOMIC ZOOLOGY AND ENTOMOLOGY

with it are mucous tubes and other pores. It is well supplied
with nerves and it has been thought by some to be an organ
of sense, perhaps some sense that man does not possess and
therefore does not understand. It is closely associated with
the ear-sac, and possibly has some similar function, that is,
of determining vibration waves.

Most fishes are colored in such a way that they are hard to
detect in their natural environment, and are thus protected,
in a measure, from their natural enemies. Some show bright
colors only at breeding time while still others are beautifully
and brilliantly colored at all times.

The skeleton consists of the many bones composing the skull
and jaws, the shoulder girdle, the backbone with a varying
number of ribs and intermuscular bones, and the bones sup-
porting the fins. Most of these bones are comparatively soft
having little lime in them. Indeed, in many cases they are
mere cartilage. The small free intermuscular bones lie im-
bedded in the flesh, and when abundant materially lessen the
value of the fish for food.

The air-bladder or swim-bladder is a characteristic struc-
ture that is found in many fishes. In the garpike, bowfin
and the lung-fishes it is connected with the esophagus and is
used as a lung for breathing. In others it is joined through
the modified bones of the neck to the organ of hearing. Its
normal function seems to be hydrostatic, that is, it helps to
keep the fish of the same specific gravity as the water by the
absorption or secretion of gas.

Most fishes lay eggs which are fertilized outside of the body
by the male pouring the milt, or spermatozoa, over them as
they settle into the gravel or other places where they are to
develop. A few make more or less elaborate nests where the
eggs are protected until they hatch. These usually produce
fewer eggs than those that make no provision for the care of
their eggs. Some of the perch-like kinds and a few others
retain the eggs in the body until they hatch, and thus produce
living young.

Fish Culture. Many of our best food-fishes occur in seem-
ingly inexhaustible numbers. When we read of shoals of

FISHES AND FISHERIES 243

fish extending over an area of six or eight square miles or of
their being so thick in a stream that they completely fill it
from bank to bank, or of their filling the nets and traps of
the fishermen so full that they cannot be lifted, we can hardly
believe that the time will come when the supply will not meet
the demand. Yet when we consider that we sometimes take
3,000,000,000 herring, and more than 455,000,000 pounds of
salmon, and 75,000,000 pounds of white fish in one season,
and other kinds of fish in corresponding numbers, it seems
evident that the supply will not always last, especially as by
far the greatest number of these fish are taken while they
are on their way to their spawning beds or after they have just
reached them. Indeed, many of our most profitable fisheries
would have been ruined long before this if the state and
national governments had not come to their aid, and by more
or less effective laws stopped some of the needless slaughter,
and, especially, by artificial propagation, increased the supply.
We are accustomed to say that nature's way of doing a thing
is the best way, but this is not always so by any means.
When the female king salmon leaves the ocean, swims far up
some stream and reaches her spawning bed, she hollows out
a little place in the gravel and deposits her eggs which
scatter over the bottom. Many of them settle in crev-
ices where they are safe, but others are left exposed,
attractive morsels for the hungry trout and other fish which
haunt the spawning beds. Soon after the female has laid
her eggs the male deposits close to them the milt, which con-
tains the spermatozoa. Probably a large percentage of the
eggs are fertilized. They remain in their hiding places for
about two months, unless disturbed by freshets. Finally the
young salmon issues and after about two months more of wait-
ing, during which time it is absorbing the yolk sac which fur-
nishes it its food, it ventures forth to seek other food. Most
of these young salmon fall a prey to the larger fish and other
enemies before they are old enough to be able to take care of
themselves. Thus from the thousands of eggs that are laid
by the parent salmon comparatively few young issue and live
long enough to make their perilous journey back to the sea.

244 ECONOMIC ZOOLOGY AND ENTOMOLOGY

This is nature's way, and it is a wasteful one, yet enough fish
were produced each year to maintain the species in great
numbers. But when the demand of man for fish became so
great that, hundreds, and later, thousands of men devoted
their time and energies to catching salmon wherever possible,
it was found that the number of fish was fast decreasing.
Under these conditions, the government established hatcheries
along some of the rivers where the salmon naturally spawned.

On these spawning beds the salmon are taken by means of
traps or nets, and, if the eggs are ripe, the body of the female
is held over a pan and gently pressed so the eggs will flow
out into the water in the pan. The milt from the male is
procured in the same way, and is poured over the eggs, thus
fertilizing them. The eggs are then taken to the hatchery,
where they are placed in wire baskets which are lowered into
troughs of flowing water and kept until the young fish hatch
and have absorbed the yolk sac and are able to take care of
themselves. In this way 80 per cent, to 95 per cent, of the
eggs that are taken are saved, and millions of young fish are
turned into the streams from the hatcheries that are located
along the tributaries of many of the most important
salmon rivers.

This is surely a great improvement over nature's wasteful
methods. In this way the fisheries on the Sacramento and
Columbia rivers have been maintained, whereas otherwise they
would have long ago been depleted. Other salmon hatcheries
have been established in Washington, British Columbia and
Alaska, until now provision is made for caring for the eggs
of all of the species of salmon, especial attention being paid
to the king, or chinook, and the red, or sockeye, salmon, as
these are commercially the most important

In the same way the eggs of many species of trout are taken
and hatched, and the young turned directly into streams or
lakes, or kept in ponds where they can be fed and reared.
At certain stages of their development the eggs can be packed
and shipped long distances, or the young may be carried shorter
distances in cans if the water is kept well aerated. Thus many
barren streams and lakes can be stocked with choice varieties of

FISHES AND FISHERIES 245

trout or the supply may be increased in the regions where too
constant fishing has depleted the numbers.

With certain modifications of this general plan, necessitated
by the structure and habits of the fish, the black and striped
bass, the whitefish, shad, pike, codfish, mackerel and others are
also artificially propagated in great quantities.

The federal government now operates thirty-six permanent
hatcheries, besides nearly a hundred auxilliary stations. In
these more than forty species of the best food and game fishes
are handled. These hatcheries are distributed over thirty-
three states, and some of these states themselves maintain
other hatcheries which handle even more fish than the govern-
ment hatcheries. New methods and improved appliances are
constantly being adopted, wonderfully increasing the usefulness
of these establishments. In this way the United States
Bureau of Fisheries and the various State Fish Commissions
are doing a valuable work in economic zoology and one that
can be appreciated by all citizens. The same Bureau and
Commissions are at work also on similar problems in con-
nection with the lobster, oyster, crab, shrimp, clam, mussel
and other invertebrate animals that are considered as a part
of our fishery resources.

Classification. The class Pisces may be divided into four
sub-classes, namely: the Elasmobranchii, including the sharks,
skates, torpedoes, etc.; iheHolocephali, including the chimaeras,
a few strange-bodied forms; the Teleostomi, including nearly
all of the other fishes, as the sturgeons, catfish, bass, salmon,
trout, cod, mackerel, herring, etc.; and theDipneusti, or lung-
fishes, represented by only a few genera whose members have
lungs in addition to gills.

The Sharks, Skates and Ray. (sub-class Elasmobranchii).
These differ from the bony fishes in several important respects,
and some icthyologists raise the sub-class to the rank of a
class. They have a skeleton composed of cartilage, there is
no operculum, and no true scales. Their teeth are distinct,
often large and highly specialized. All the members of the
group are marine.

The fierce, carnivorous and voracious sharks live in the

246 ECONOMIC ZOOLOGY AND ENTOMOLOGY

surface waters and feed on any other animals that they can
capture. The shark's mouth is on the underside of the head,
so it must turn over on its back in order to sieze any prey
that is swimming above it. The great basking sharks, genus
Cetorhinus, which reach a length of nearly forty feet, often
gather in numbers and float motionless on the surface of the
sea. The great white shark, Carcharodon carcharias, occurs

FIG. 114. The common skate, Raja erinacca. (From Kingsley.)

in all warm seas, and because it does not hesitate to attack
man it is often known as the man-eating shark. It attains a
length of thirty feet or more. The smooth dogfish shark,
Mustelus, the horned dogfish shark, Squalus, and the sand-
shark, Carcharias, often occur in great numbers in shallow
waters and do much damage by destroying lobsters and many
valuable food fishes. They are a great nuisance on the

FISHES AND FISHERIES 247

fishing grounds not only on account of the fact that they kill
but because they drive away the schools of fish and squid and
destroy the nets and traps.

The skates and rays have a broad, flattened body with the
gill-openings on the underside. They are usually sluggish,
lying at the bottom of shallow waters along the shore feeding
on crabs, molluscs and bottom fishes. The small common
skates, or "tobacco-boxes," Raja erinacea, which reach a
length of about twenty inches, and the larger "barn-door
skates," R. lizvis, are numerous along the Atlantic Coast.
The sting-rays, genus Dasyatis, which lie in the sand in shallow
water, have a barbed spine on their whip-like tail which makes
a very painful wound. The torpedoes, or electric-rays, have,
on either side of the head, modified bundles of muscles which
store up considerable electric energy. The discharge from
these electric organs can give a strong shock to animals coming
in contact with them. It is said that a discharge from a
large electric-ray is sufficient to disable a man temporarily.
The saw-fish, Pristis pectinatus, differs from the typical rays
by having the body more elongate and shark-like. The head
is prolonged into a long saw-like snout which may reach a
length of five feet or more. This may be used as a weapon of
defense or to kill the small sardines and herring upon which
the saw-fishes feed.

The Chimaeras, or "Elephant Fishes" (sub-class Holo-
cephali). These fishes compose a small group of peculiar
forms looking somewhat like the smaller sharks. Most of them
live in deep water, but others are rather common in the
shallow water of bays along both coasts of America and else-
where. They are of very little economic importance.

The True Fishes (sub-class Teleostomi). -To this sub-class
belong nearly all of our common fishes, both of fresh water
and ocean. In most of them the skeleton is bony and not
cartilaginous as in the sharks and rays. The sturgeons,
family Acipenseridce, are the notable exception to this rule, as
their skeleton is cartilaginous. In the garpikes and a few
others the skeleton is only partly bony. The sturgeons occur
in both salt and fresh water, some of them attaining a weight

248 ECONOMIC ZOOLOGY AND ENTOMOLOGY

of 300 to 500 pounds or more. The skin is provided with series
of large bony plates on the sides, on the back and beneath.
These plates are not contiguous, and so do not form a complete
covering for the body. Although the meat is rather coarse it is
largely used for food, and the egg masses, or roe, are used in
making caviar. Some of the largest species, such as those that
run up into the Columbia, were almost exterminated by wanton
destruction before the need of conserving them was realized.

The garpikes, family Lepisosteidce, are common in the
lakes and rivers of the middle and eastern United States.
They are long and slender, and the body is covered with close-
set horny scales which form a complete armor. They are
carnivorous and often destroy great numbers of valuable food
fishes, they themselves being unfit for food.

The catfishes, family Siluridce, are distinguished by their
smooth skin, which is without scales, and by the somewhat
flattened head and the numerous long, soft, slender feelers
about the mouth. There are many kinds known by different
common names, such as "horned pout," "bull-head/' "chan-
nel-cat," etc. The latter sometimes reaches a weight of
200 pounds. Most of them are excellent food fishes.

The suckers, family Catostomidce, occur abundantly in almost
all regions. They feed on insects and small aquatic animals
which they suck up into their mouth. Some reach a length of
about three feet, but their flesh is flavorless and full of bones,
so they are but little used for food.

The family Cyprinidce includes the carps, chubs, minnows
and gold fishes. One of the most common carps, Cyprinus
carpio, commonly known as the European carp, is a native of
China, where it has been domesticated for centuries. About
300 years ago it was introduced into Europe and later into
the United States where its cultivation has attracted consider-
able attention. They are not generally prized as food fish
by Americans, but are largely used by other nationalities and
so are important fish in many of the larger markets. The
chubs (Notropis spp.) are abundant in nearly all fresh water,
and sometimes reach considerable size, but they are of little
value as food. Many of the smaller species belonging to this

FISHES AND FISHERIES 249

family are known as minnows. They are an important source
of food for larger fish, and are much used for bait.

The goldfish, Carassius auratus, is a native of China. In
its native waters or where it escapes from domestication it is
of a greenish hue, the beautiful golden yellow color being
brought about and retained by artificial selection. In the
same way the many strange shapes and varieties have been
produced.

The true eels, family Anguillida, are long, slender and with
small inconspicuous scales. They are found in most fresh
water streams and lakes where they feed chiefly on all kinds
of refuse, but they frequently destroy great numbers of shad,
herring and other fish, particularly at spawning time. They
go down the rivers to the sea to spawn. The ova are very
minute, and it has been estimated that a single female may
produce over 10,000,000 eggs. They are regarded as excellent
food fishes.

The conger-eels, family LeptocephaHdce, are scaleless, occur
in the sea at moderate depths, and are little used as food in
America.

The family ClupeidcR includes the herring, sardines, shad,
menhaden and others. The herring, genus Clupea, occur in
both the Atlantic and Pacific, and when they come in shore at
spawning time they are taken in great numbers and canned as
sardines, dried, smoked or salted, or used fresh for food or bait.
The herring fisheries of the North Atlantic are particularly
important. It has been estimated that at least 10,000,000,000
herring are taken by British and American fisherman each year
representing a weight of more than one-third as many pounds.
They occur in great shoals sometimes miles in extent.

The sardines (genus Sardinella) are fine-flavored little fish
with rather soft bones. Preserved in oil they form a most
important article of commerce. Great numbers are used for
bait.

The shad (genus Alosa), although very bony, are highly
esteemed on account of their fine delicate flavor. They occur
on both coasts, having been introduced into California, and
ascend the rivers to spawn in May. They are very prolific,

250 ECONOMIC ZOOLOGY AND ENTOMOLOGY

each female yielding usually about 30,000 eggs, but some have
been known to produce two or three or even five times as many.

Although the menhaden (genus Brevoortia) are but little
valued for food, they are of great commercial importance
on account of the oil that is extracted from them. The refuse
is used for fertilizer. They are also largely used in the prepa-
ration of fish meal for domestic animals.

The anchovies, family Engraulidce, are fine-flavored oily
little fish that are often preserved in oil or spices. They are
very abundant in many waters, and form an important source
of bait and of food for other fishes.

In many respects the family Salmonidce, including the salmon,
trout, and whitefish, is the most important of all. The
salmon fisheries constitute one of the principal industries of
the Pacific northwest, the whitefish are among -the most
important fish of the Lake regions, and the trout are found
in almost all swift-flowing streams and clear cold lakes, and
are more sought after by the angler than any other fish.

The Pacific salmon, genus OncorhyncJms, occur in the north
Pacific. Little is known of their habits while in the sea,
but just before spawning time they enter certain rivers and
start upstream for the spawning grounds, taking no food
while in fresh water. The king salmon, or quinnat salmon,
enters, in enormous numbers, such rivers as the Sacramento,
Columbia, Frazer and Yukon, large streams fed by mountain
snows. Up these rivers they may make their way through
rapids and over falls for several hundred miles, often to the
very head waters, before spawning. In the Yukon they may
ascend 2250 miles from the ocean.

The red salmon, or sockeye salmon, is commercially the most
important of all. They are taken in large seines or traps in
Puget Sound or similar bays while going in great schools to
the rivers which they ascend to reach their spawning grounds.
They will enter only such rivers as are fed by lakes, and spawn
in the small streams that flow into the lakes, sometimes 1000
to 1800 miles from the ocean. The other species spawn closer
to the sea in almost any fresh water stream. After spawning,
the salmon remain near their eggs until, too weak to resist

FISHES AND FISHERIES

25 1

the current, they drift down and die. Most of the young
make their way to the sea and a few return, three or four
years later, as mature fish ready to spawn. The salmon
fisheries have long been one of the most important industries
on the Pacific Coast. In some years more than 5,000,000
cases are packed, each case containing forty-eight one-pound
cans. The value of such a pack is more than $25,000,000.

The Atlantic Coast salmon, Salmo salar, ascend fresh water
streams to spawn, but unlike the western salmon, they return
alive to the sea again.

There are many species of trout, as the black-spotted,
rainbow and cut-throat, belonging to the genus Salmo. Many

FIG. 115. The rainbow-trout, Salmo iridcus.

of these species are represented by one or more varieties, so it
is often difficult for even an expert ichthyologist to determine
the species definitely. There are certain well-marked types,
however, and each region has its particular representative trout
type which affords the best kind of sport to the enthusiastic
anglers. The genus Salve! in us includes some of the choicest
and most beautiful of the brook trout. They are frequently
called char, and differ from the members of the genus Salmo
in that the body is covered with round crimson or gray spots
which are paler than the ground color. The scales are smaller
and so imbeded in the skin as generally to escape notice.

The whitefish, genus Coregonus, occurring usually in clear
cold lakes or streams, are regarded as especially fine food

252 ECONOMIC ZOOLOGY AND ENTOMOLOGY

fishes. The largest of the species of this genus ranges from
New York and the Great Lakes northward. The whitefish
constitute the most imporant group of the fresh water fishes.
While the average weight is probably under four pounds some
attain a weight of more than twenty pounds. Although
considerable quantities are salted the largest part of the catch,
valued some years at more than $1,500,000, is used fresh.

The lake herring, genus Argyrosomus, are closely related to
the whitefish, but are not as highly valued as food. They
occur in enormous numbers throughout the Great Lake region.

The grayling, family Thymallidce, beautiful, trout-like
fish, found in some of our northern streams and common in
Europe, are characterized by the greatly developed dorsal
fin. They are superior food and game fishes.

The smelt, family A rgentinidee, are also closely related to the
Salmonidce. They are mostly marine, and all are excellent
food fishes. The eulachon, or candle-fish, is regarded by many
as the most delicate and luscious of all fishes. They are very
oily and it is said that when dried and provided with a wick
they will burn like a candle. The oil is pressed out and
used to some extent as a substitute for cod-liver oil.

The pike, family Esocidce, are long, slender, swift-swimming
fish found in many fresh water lakes and streams, the fine
muskallunge of the Great Lake region reaching a weight of
sixty to eighty pounds. The smaller pike are sometimes called
pickerel. They are all excellent food and game fishes.

The mullets, family Mugilida, are found in both fresh and
salt water, where they feed on the organic matter that they
can sift out of the mud. In some regions they are especially
abundant, particularly along the Florida and Gulf coast where
they are important food fishes.

The mackerel, family Scombrida, are among the most im-
portant fishes of the Atlantic. Along the New England coast
many villages are almost w r holly dependent upon the success
attained by the crews of the fleets of splendid mackerel
schooners that each season put out to fish. Hundreds of
thousands of barrels of mackerel are salted each year, and great
quantities are used fresh. Several species occur along the

FISHES AND FISHERIES 253

Atlantic and Pacific Coasts and in many other parts of the
world. Some of the species such as the Spanish mackerel and
the tuna, are unexcelled as food or game fishes.

The large family Cenlrarchidce includes the sunfishes and
rock bass, black bass and others. The various species of sun-
fishes occur in almost all parts of the country. Some of them
are handsomely marked and they are all good food fishes.
The black bass are among the most important of the game
fishes, and are fast taking the place of the trout in many
streams where the latter have not been able to hold their own
on account of the changed conditions of the water and the
intensive fishing. The bass quickly adapt themselves to their
surroundings and have been successfully introduced into
California, Europe and other places where they do not occur
naturally. The fresh water white bass and yellow bass, and
the larger striped bass or rock-fish which lives in the sea and
runs up the rivers to spawn, and many other important sea
bass, belong to the family SerranidcB. The giant bass, some-
times called jewfish, reaches a weight of more than 500 pounds.

The family Percidce includes the wall-eyed pike and the true
perches of which the yellow perch is our most common ex-
ample. They are both good game and food fishes.

On the west coast is a family of perch-like ocean fishes,
family Embiotocidtz, commonly called perch or surf- fish.
These differ from almost all of the other higher fish in being
viviparous, the young being carried in the body of the mother
until they have attained considerable size.

The codfish, family Gadida, is one of the most important
of the North Atlantic fishes. It occurs also in the North
Pacific but in small numbers. The codfish industry gives
employment to thousands of men and warrants a profitable
investment in boats and other apparatus to the extent of
millions of dollars. The flesh of the cod is flaky and with
little flavor but it is well adapted to drying or salting and it
is in this condition that it is most largely used.

Among the most remarkable of our well-known fishes are
the flounders and halibut, family Pleuronectidce. The young
at first swim upright in the water like other fishes and have

254 ECONOMIC ZOOLOGY AND ENTOMOLOGY

their eyes in the normal position. But soon they begin to rest
on the bottom and the eye on the lower side begins to
migrate, so that in a little while both eyes are close together
on the upper side of the head. Many species of flounders
and soles are found along the shores of both oceans. They
are largely used as food. The halibut occur on offshore banks
in the northern part of the Atlantic and Pacific oceans. They
reach a length of six to eight feet and a weight of 500 pounds or
more. The halibut fisheries are very important, especially in
the north Pacific. The young halibut, called " chicken
halibut," are tender and of fine flavor, differing in this

FIG. 1 1 6. The winter flounder, Psendoplcuronectes americanus. (After

Goode.)

respect from most of the flat fishes which, although in great
demand for food, do not have much flavor.

With this brief review of only a few of the more important
of the many hundreds of common food or game fishes we must
leave the discussion of this sub-class without even a reference
to the many strange and interesting fishes that occur in the
fresh waters of other lands-and in other seas. Among the coral
reefs that surround many of the tropical islands are to be found
most beautifully colored fishes; in the greatest depths of the
ocean are strange uncanny fish, some of which are provided
with phosphorescent patches on their heads or on appendages,
enabling them to see in the dark abysses. For the study of these

FISHES AND FISHERIES 255

and such others, as the curious sea-horses and the remarkable
flying-fish, and the fishes that leave the water and wander
over the land, the student must go to some of the detailed
works on fishes, as Jordan's "Guide to the Study of Fishes."
Jordan & Evermann's "American Food and Game Fishes"
is a most excellent treatise, popular enough so that anyone may
enjoy reading it.

The Lung -fishes (sub-class Dipneusti). r l]\i?, sub-class,
formerly called Dipnoi, is represented by only a few living
species, occurring in Australia, South America and Africa.
They are of particular interest to the naturalist not only be-
cause they are the sole survivors of a once numerous group of
fishes, but because several things about their structure seem
to indicate that they must be closely allied to the ancestral
type from which both the bony fishes and the Amphibia, or
frogs, salamanders, etc., have descended. The gills in most
of them remain functional and are used while the animals are
in the water, but at other times, when they burrow into the
wet mud or elsewhere, they breathe by means of lungs, which
are spongy sacs, represented in most fishes by the air bladder.
The paired fins, too, have an elongated jointed axis with rays
which resemble the limbs of some of the Amphibia as much
as the fins of fish.

CHAPTER XXII
TOADS, FROGS AND SALAMANDERS

The toads and frogs are the most common representatives
of the class Amphibia, but the salamanders, or water-dogs,
are very often found along streams or in moist places. The
ccecilians, legless, worm-like or snake-like creatures occurring
in the tropics, also belong to this class.

Almost fifteen hundred living species of amphibians are
known. These may be grouped into three fairly well-defined
orders, the A pod a, or footless, snake-like forms, the Urodela,
or tailed amphibians, and the Anura, or tailless forms like the
toad and frog.

The Ccecilians (order A pod a). This order includes a few
worm-like or snake-like footless species called ccecilians usu-
ally having small scales embedded in the skin. They occur
only in tropical regions and are of no economic importance.

The Water-dogs (order Urodela}. Several widely different
forms are grouped together in this order so that it is often
divided into suborders. They all agree in having a tail, which
may be longer or shorter than the rest of the body. The mud-
puppies or water-dogs, genus Necturns, occur in the rivers and
lakes of the northern United States. They attain a length of
about two feet when full grown. They have four legs, and
breathe by means of bushy gills which arise from in front of
the forelegs. The sirens or mud-eels, genus Siren, burrow in
the mud in ponds and ditches in the southern states, attaining
a length of about three feet. They have three pairs of gills
and only one pair of legs.

The large, heavy-bodied, blackish water-dog or hell-bender,
genus Cryptobranchus, is another aquatic form, but the ex-
ternal gills are replaced by small openings or gill slits which
lead into the throat. It is found along the Ohio river

256

TOADS, FROGS AND SALAMANDERS 257

and its tributaries. The salamanders and newts are common
in many regions. Most of them possess neither gills nor
gill openings in the adult. Some of them are often called
lizards, but they differ widely from the lizards in many re-
spects. The body is soft and not provided with scales, and in
their development they pass through a tadpole stage similar
to that of the frogs and toads. Amblystoma tigrinum is an
interesting and widely distributed common species. In
some regions the larval form, know r n as axolotl, reaches
a large size and produces young before completing the
usual metamorphosis.

FIG. 117. A brown salamander, Notophthalmus lorosus. (Reduced.)

The Frogs and Toads (order Anura). This is by far the
largest and most important order of Amphibia. There are
about a dozen species of frogs, family Ranidce, found in the
United States. The well known bullfrog, Rana catesbiana,
is the largest of these, attaining a length of seven or eight
inches. It occurs in ponds and sluggish streams all over the
eastern United States and in the Mississippi Valley. Frogs
are very commonly used as food in the United States but not
as extensively as in some of the European countries. The large
hind legs and "saddle" afford a considerable mass of very deli-
cately flavored meat. It has been pointed out that there is an
opportunity for the development of a small but profitable
industry in raising frogs for market in some of the extensive

17

258 ECONOMIC ZOOLOGY AND ENTOMOLOGY

areas of marsh land where frogs abound. Frogs are used more
than any other vertebrate in the laboratories of schools and
colleges, not only because they are easily obtained but because
in their structure and habits one may find illustrations of so
many of the fundamental facts of zoology. The tree-frogs or
tree-toads, family Hylidce, are more closely related to the
toads than to the frogs. Their toes are usually provided with
adhesive disks which enable them to cling to the trunk of a
tree or other perpendicular surfaces. Their vocal sacs are

FIG. 118. A western garden toad, Bufo halophilus. (Reduced.)

large, and they make a noise out of all proportion to their
size. Hyla versicolor, the most common of these tree-frogs,
is green, gray or brown above, and has the power of slowly
changing from one color to another so as to produce a re-
markable harmony between the frog and its surroundings,
thus making it almost invisible to its enemies. This change
in color is brought about by the expansion or contraction of
certain pigment cells in the skin.

The structure and habits of the toads, family Bufonidce,
have already been discussed (Chapter II). There are
about fifteen species in the United States and less than one
hundred species in other lands. Some of the exotic species

TOADS, FROGS AND SALAMANDERS 259

are interesting on account of the unusual method of caring
for their eggs or young. The females of some species carry
the eggs on their back until they hatch. Others are provided
with a large pouch in which all the eggs are stored, or with a
cell-like pouch for each egg where the larva hatches and re-
mains until it has passed through the tadpole stage. In still
other species the male cares for the eggs. All toads are
beneficial because they eat so many noxious insects.

The Frog Book, by Mary Dickerson, gives an admirable
account of the kinds, distribution and habits of the American
frogs and toads. It is well illustrated in color.

CHAPTER XXIII
SNAKES, LIZARDS, TURTLES, AND CROCODILES

The large class, Kept ilia, including the turtles and tortoises,
crocodiles and alligators, lizards and snakes, is composed of
animals differing in general appearance but possessing many
characteristic features that show their close relationship. Most
of them are terrestrial in habitat. All are cold blooded and
almost all breathe by means of lungs, those that spend part of
their life in water coming to the surface to breathe. Nearly all
creep or crawl, dragging the body on the ground or close to it.
The body is covered with scales or with large plates. The rep-
tiles pass through no metamorphosis during their develop-
ment, the young when born or hatched from the egg resem-
bling the adult except in size. Most reptiles lay eggs, as do
the birds, and so are called oviparous. But the common
garter-snakes and some other species, retain the eggs within
the body until they are hatched, and so are said to be
ovoviparous. The eggs are usually laid in the earth or sand
or in vegetable mould and given no further care by the
mother, but some species show great solicitude for the
eggs, guarding them jealously until they hatch.

In general appearance some of the lizards resemble the
salamanders and other amphibians more than they do other
members of their own class, and the reptiles are usually closely
associated in the common mind with the amphibians. A study
of their body structure, however, shows that they are really
more closely related to the birds than to the amphibians. In
some of the extinct orders of reptiles the resemblance to birds
was quite remarkable from the fact that their whole body was
modified to fit them for flight. Some of these flying reptiles,
the Pterosauria, attained a great size, having a wing expanse
of twenty feet. But that was during the Cretaceous epoch, or

260

SNAKES, LIZARDS, TURTLES, AND CROCODILES 261

Age of Reptiles, when the giant Dinosaurians, some of which
measured over a hundred feet in length, roamed the swamps,
and the whale-like Ichthyosaurians swam in the seas.

In reptiles, as in amphibians, the chief variations in the body
skeleton are correlated with differences in external body
form. In the short compact body of the turtles and tortoises
the number of vertebrae is much smaller than in snakes.
Some turtles have only 34 vertebras; certain snakes as many as
400. The reptilian skull, in the number and disposition of
its parts and in the manner of its attachment to the spinal
column, resembles that of the birds, although the cranial bones
remain separate, not fusing as in birds. All of the reptiles,
except the turtles, are provided with small teeth which serve,
generally, for seizing or holding prey and not for mastication.

Reptiles breathe solely by lungs, of which there is a pair.
They are simple and sac-like, the left lung being often much
smaller than the other. In turtles and crocodiles the lungs
are divided internally by septa into a number of chambers.
Because of the rigidity of the carapace, or "box", of turtles the
air cannot be taken in the ordinary way by the use of the
ribs and rib muscles, but has to be swallowed. The reptilian
heart consists of two distinct auricles and of two ventricles,
which in most reptiles are only incompletely divided, the
division into right and left ventricles being complete only
among the crocodiles and alligators, the most highly organized
of living reptiles.

The organs of the nervous system reach a considerable de-
gree of development in the animals of this class. The brain
in size and complexity is plainly superior to the amphibian
brain and resembles quite closely that of birds. Of the organs
of special sense those of touch are limited to special papillae
in the skin of certain snakes and many lizards. Taste seems
to be little developed, but olfactory organs of considerable
complexity are present in most forms, and consist of a pair
of nostrils with olfactory folds on their inner surfaces. The
ears vary much in degree of organization, crocodiles and
alligators being the only reptiles with a well-defined outer
ear. This consists of a dermal flap covering a tympanum.

262 ECONOMIC ZOOLOGY AND ENTOMOLOGY

Eyes are always present and are highly developed. They
resemble the eyes of birds in many particulars. All reptiles,
except the snakes and a few lizards, have movable eyelids,
including a nictitating membrane like that of the birds.
With the snake the eye is protected by the outer skin, a
transparent portion of which remains intact over the eye.
Turtles and lizards have a ring of bony plates surrounding the
eyes similar to that of birds. In addition to the usual eye
there is in many lizards a remarkable eye-like organ, the so-
called pineal eye, which is situated in the roof of the cranium,
and is believed to be the vestige of a true third eye, which in
ancient reptiles was probably a well-developed organ.

Classification. The living reptiles may be divided into four
orders. One of these, the order Rkynchoccphalia, includes only
a single lizard-like genus confined to New Zealand. The
Chelonia, including the turtles and tortoises, are distinguished
by the scaly, bony or leathery shell covering the body. The
Crocodilia, or crocodiles and alligators, have the body covered
with rows of sculptured horny scutes or scales, while the
lizards and snakes, order Squamata, are usually covered with
many small, flat, horny, epidermal scales.

Turtles and Tortoises. The short stout body of these
animals is enclosed in a more or less firm shell, which consists
of an upper portion, the carapace, that is firmly joined along
the sides to the lower portion, the plastron. From the front
opening of this box-like covering the head and forelegs may
be protruded when the animal is feeding or moving about,
the hind legs and tail being extended from the opening along
the posterior margin. When the appendages are withdrawn
they fit snugly into these openings and the whole animal is
comparatively safe from its enemies. In some turtles the
shell does not become hard and horny, but remains soft or
leathery. The head usually terminates, in a hooked beak and
serves as a formidable weapon of offense or defense. Many
of the turtles are wholly aquatic, feeding on fish, frogs, worms,
molluscs and sometimes small water-fowl or upon the grasses
that grow in the water. Others spend a part of their time on
the land and part in the water while still others are wholly

SNAKES, LIZARDS, TURTLES, AND CROCODILES 263

terrestrial. The term turtle is usually applied to the aquatic
forms, while the land forms are commonly known as tortoises.
The name terrapin is applied to some of the kinds that are used
for food. They all lay eggs, which may be deposited in the
banks of the ponds, rivers or streams, or in the sand, where
they are incubated by the sun's rays.

Turtles, tortoises and terrapins are of considerable economic
importance as some of them are highly valued for food. Also
the horny carapace of many species is very valuable, being

FIG. 1 19. The giant land-tortoise of the Galapagos Islands, Tcstitdo sp.
(These tortoises reach a length of four feet; after Coleman.)

used extensively in the manufacture of combs and various
ornaments. Among the common aquatic species found in
the United States are the soft-shelled turtles, genus Trionyx.
The flat leathery shell as well as the enclosed body are used for
food. The animal defends itself viciously when attacked.
The large snapping-turtle, Chelydra serpent-ma, that is found in
so many of the streams and ponds east of the Rocky Mountains,
defends itself principally by its powerful beak as its shell is too
small to protect it completely. The southern alligator snap-
ping-turtle, Macrochelys lacertina, often attains a weight of

264 ECONOMIC ZOOLOGY AND ENTOMOLOGY

more than 100 pounds. It is largely used for food. Care has
to be exercised in handling live specimens for they are of ugly
temper and bite severely.

The painted turtle or painted terrapin, Chrysemys picta,
has the carapace beautifully marked and colored. It lives
in ponds and sluggish streams, feeding on aquatic plants and
any insects or small animals that it may find in the water.

The famous diamond-back terrapin, Malacoclemmys palustris,
lives in the salt marshes along the Atlantic coast. These
animals, once very abundant, are now comparatively rare
because they have been so much ,hun ted. The price has
rapidly risen from a few cents apiece to five or six dollars.

Still more highly prized for food is the great green turtle,
Chelonia my das. This species is widely distributed in tropical
seas and occurs as far north along the Atlantic Coast as the
Carolinas. It lives on the roots of eel or turtle grass, and may
attain a weight of 500 pounds or more.

The hawk's-bill turtle or tortoise-shell turtle, Chelonia
imbricata, is the source of the beautiful tortoise shell of com-
merce. Its shell is made up of a series of shield-like plates.
About eight pounds of the valuable dorsal shields are sometimes
obtained from a single large turtle of tropical and subtropical
oceans.

The leather-back turtle, Sphargis coriacea, is the largest of
the turtles, attaining a length of six to eight feet and a weight
of a thousand pounds. It lives in tropical and semi-tropical
seas, going on land only to deposit its eggs. Both the fore
and hind limbs are modified into broad flippers for swimming.
It is not used for food.

The giant tortoises, genus Testudo, inhabiting some of the
tropical islands, often weigh as much as 300 pounds and some
of them are estimated to be more than 400 years old.

Alligators and Crocodiles. The skin of the alligators is
thick and tough and covered with horny scales. The legs are
well developed, but the animal moves clumsily on land. The
long, laterally compressed tail makes them powerful swimmers.
There are only two species of alligators, one occurring in China,
the other, Alligator mississippiensis, in the southern parts of

SNAKES, LIZARDS, TURTLES, AND CROCODILES 265

the United States. The American alligator may grow to be
ten or twelve feet long, and is hunted for its skin which makes
strong, beautifully marked leather that takes a fine polish.
The wholesale slaughter of these animals for their skin has
so greatly reduced their numbers that extinction is threatened
unless measures are taken to protect them in certain preserves.

The crocodiles are more widely distributed than are the
alligators. The American crocodile, Crocodilus americanus,
is found in Florida, Mexico and South America. It differs
from the alligator in having a longer, narrower head.

The African crocodile, C. niloticus, is a ferocious species
often attacking man and is greatly feared by the natives of
that continent. There are several other crocodile kinds in
various parts of the world, some of them reaching a length of
twenty feet or more. The skin of many of the species is
used for leather.

The Indian gavial, Gavialis gangeticus, common in the
Ganges, attains a length of twenty feet or more, and is reputed
to feed on the bodies of children that are thrown into the river
by the natives. Its natural food is fish. It is distinguished
from the alligators and crocodiles by having a long slender
snout.

Chameleons, Lizards and Snakes. The order Squamata
is divided into three sub-orders: the Rhiptoglossi, including the
chameleons, the Sanria, including the lizards, and the Serpentes,
including the snakes. The true chameleons differ from the
other members of this order in several respects. The body is
laterally compressed, the legs are long and slender, and the toes
are grouped so that two of them are opposed to the other three.
The tongue can be projected for a remarkable distance for
capturing insects. Chameleons are of interest because of their
power of rapidly changing their colors. The color is usually
greenish, but under certain stimuli, such as light and tempera-
ture, the color may change to varied shades simulating the
surrounding objects. This change of color is, seemingly at
least, partially under control of the animal. None of the mem-
bers of this sub-order occurs in America, but there is found in
the southern states a beautiful green lizard, Anolis principalis,

266 ECONOMIC ZOOLOGY AND ENTOMOLOGY

that has the power of changing its color to a considerable
degree and so is popularly called a chameleon.

The group of lizards is a very large one, the species being
especially abundant in the tropics. The skin is covered with
many small scales, and the legs are fitted for running, but the

FIG. 120. A fence lizard, Scdoporus accident alis.

body is usually dragged along the ground and not wholly
lifted by the legs. The jaws are furnished with teeth. Lizards
feed principally upon insects, and some of the species may be
of considerable importance in controlling noxious forms.
Although the lizards are often regarded as being poisonous

- HI BflB^HB -sr-

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...

FIG. 121. The Gila monster, Heloderma suspect unt, the only poisonous

lizard. (After Snyder.)

the members of only a single genus, Heloderma, are really so.
This genus includes the Gila monster found in New Mexico,
Arizona and northern Mexico. It is a heavy-bodied, deep
black, orange-mottled lizard, twelve to sixteen inches long.
The poison is secreted by glands in the lower jaw and flows

SNAKES, LIZARDS, TURTLES, AND CROCODILES 267

along the grooved teeth into the wound. The bite of this ill-
looking reptile may be very serious.

The most common lizards in this country are the swifts
and ground lizards that are so numerous in many gravelly
and bushy places. They may often be seen sunning themselves
on rocks, fences or other exposed places. They are all very
timid. An interesting member of this group is the glass snake,
or joint-snake. Having no external limbs it is commonly
considered to be a snake rather than a lizard. Its tail is so
brittle that part of it may break off at the slightest pull or blow.
In time a new tail is regenerated. Many other lizards
possess this power of easily breaking off a portion of the tail.
It will be seen that this may often be of considerable impor-
tance to the lizard, for if it is pursued by an enemy the part
most likely to be seized is the tail, and if this can be broken off
the lizard may escape and in time the lost part be replaced.

In the desert regions of the Southwest are found several
species of the peculiar little lizard commonly known as the
horned toad, genus Phrynosoma. The body is shortened,
much flattened, and furnished with a number of spine-like
scales. These spines are particularly well-developed in a
row along the hind margin of the head. The color of these
animals resembles very closely the soil or rocks where they are
found. This protecting coloration doubtless helps to save
them from their enemies. In the tropics many of the lizards
attain a great size, and are of strange shapes and patterns.
Some of the tree-inhabiting forms are very beautifully colored.
The iguanas in South America often reach a length of five or
six feet, and are much used for food.

The appendages are entirely absent in most of the snakes.
A few species, however, have a pair of spur-like projections
on the hinder part of the body, doubtless vestiges of the hind
legs. The lower side of the body in front of the anus is covered
with broad scales, called abdominal s'cutes, which extend
from one side of the body to the other. The ends of these
broad scales are attached to the ribs, and the free posterior
edges may be drawn forward slightly and pressed against the
surface on which the snake is lying so that when they are

268 ECONOMIC ZOOLOGY AND ENTOMOLOGY

drawn back again the body of the snake is thrust forward.
It is the movement of these scutes, accompanied by the
undulations of the body, that enables the snake to crawl so
rapidly. They cannot move forward on smooth surfaces
because the scutes have nothing to catch against. The scales
on the head are quite regular in their arrangement, forming
definite patterns. The bones of the jaws are so arranged
that the mouth is very distensible. This allows the snakes
to swallow objects which are greater in size than the normal
diameter of the body and it is not an unusual sight to see a

FIG. 122. A garter-snake, Thamnophis parietalis. (After Snyder.)

snake with a part of its body very greatly distended by
some small animal that it has swallowed whole. The tongue
is slender, protrusible and deeply notched. It is commonly
supposed that the tongue can inflict injury, but this is not
true. It doubtless serves as a special organ of touch. The
teeth are sharp and recurrent. In the poisonous snakes cer-
tain of the teeth develop into long sharp fangs which are
grooved or tubular and serve to conduct the poison from the
poison gland in the head into the wound. The food of snakes
consists very largely of other animals which are usually caught
alive. Many species feed on the eggs of other animals. Many
persons erroneously regard all snakes as dangerous, and try to
kill all that they see. But most of our common kinds are not
only harmless but very serviceable because they destroy mice,

SNAKES, LIZARDS, TURTLES, AND CROCODILES 269

ground squirrels or other pests. The blind snakes, genus
Glaucoma, burrow in the earth and feed on insect larvae and
worms.

Among the most familiar of the many non-poisonous snakes
are the striped garter-snakes, genus Thamnophis, found every-
where in the fields and gardens. The common water-snake,
genus Natrix, is only semi-aquatic, spending most of the time
on land in the vicinity of ponds or streams. They are ex-
cellent swimmers and quickly take to the water when alarmed.
The large blacksnake, Zamenis constrictor, and the blue-racer,

FIG. 123. A king-snake, Lampropeltis boyli. (After Snyder.)

which is merely a color variety of the same species, are common
in open meadows, where they feed on frogs, mice, eggs, young
birds and other animals which they swallow alive. The
king-snakes, genus Ophibolus, are so called because they feed
on other snakes. They seem to be immune to the venom of the
poisonous snakes and readily attack any of them. The puff-
adders, or spreading vipers, or blow-snakes, genus Hetcrodon,
are commonly supposed to be poisonous but are really quite
harmless. No American snake with slender, sub-parallel-
sided head is poisonous.

The dreaded rattlesnakes, and the copperheads and water-
moccasins, are thick-bodied venomous snakes with flat, tri-
angular heads and with strong tubular fangs which are folded
flat against the roof of the mouth when it is closed. When

2 7 o ECONOMIC ZOOLOGY AND ENTOMOLOGY

the snake strikes, these fangs are lowered and thrust into
the victim and the poison, which is secreted by small glands in
the head, is injected through them. There are several species
of rattlesnakes, all belonging to the genus Crotalus, They are
most abundant in the Southwest, but are found in almost all
parts of the United States except in the higher mountains.
The rattle on the tail is composed of a series of partly overlap-
ping thin horny pieces, the somewhat modified successively
formed epidermal coverings of the tip of the body. A new rattle
is added each time the snake sheds its skin, and as the snakes
usually molt about three times a year the age of a rattlesnake
may be approximately estimated provided none of the terminal
units of the rattle has been lost.

FIG. 124. The rattles of the rattlesnake. The lower figure shows a longi-
tudinal section of the rattle.

The chestnut-colored copperheads, Agkistrodon contortrix,
occur throughout the eastern and middle United States. They
are very vicious and dangerous, striking without warning.
The water-moccasin, Agkistrodon pisciwris, of the southern
states is the most dangerous of our serpents. It is found in
swampy places and in the water. It is ill-tempered and aggres-
sive, striking on the slightest provocation. The poisonous
harlequins or coral-snakes, Elapsfulvius, that live in the south-
eastern United States, are also very venomous. They are
black, very strikingly marked by broad, yellow-bordered,
crimson rings.

SNAKES, LIZARDS, TURTLES, AND CROCODILES 271

Notwithstanding the fact that a bite from any one of these
venomous snakes may prove fatal to man in a very short time,
the real danger from these snakes is not as great as it would
seem, for they may usually be seen or heard and avoided. The
number of deaths resulting from snake bites in the United
States each year is very small indeed, an average of but only
two each year, it has been estimated. Sucking the blood and
poison from the wound or drinking large quantities of whiskey
are the two methods most commonly recommended for treat-
ing snake bites. Sucking the poison from the wound may do
some good but it is very dangerous, for should some of the poi-
son get into cuts or abrasions
on the lips or in the mouth

it might cause more harm
that it would in the original
wound. Excessive use of al-
coholic drinks must also be
avoided, as experiments have
shown that they may exert
a very unfavorable effect.
The best thing to do if one
should be bitten by a poi-
sonous snake is to apply pres-
sure, by a ligature or other-
wise, to the blood-vessels lead-
ing from the wound to the

heart to prevent the blood from carrying the poison to the
heart. If a physician is not available within a very short
time the tissue around the wound should be incised deeply and
a solution of potassium permanganate (i part of the chemical
to 100 parts of water) injected. If properly and promptly
applied such a treatment may destroy much of the venom
before it can reach the heart and be sent from there over the
whole system. Hypochlorite of calcium, i part to 60 parts of
water, or chloride of gold, i to 100, or chromic acid, i to 100,
may be used if the potassium permanganate is not available.
When the venom of a poisonous snake is introduced into the
blood of an animal in small quantities it is capable of pro-

FIG. 125. Dissection of head of
rattlesnake. /, poison-fangs; p,
poison-sac.

272 ECONOMIC ZOOLOGY AND ENTOMOLOGY

during a substance called antivenin which neutralizes the
effect of that particular kind of poison. In regions where
snake bites are of frequent occurrence the antivenin for the
most dangerous snakes is prepared and kept ready for use. A
small amount of it injected into the blood-vessels soon after a
snake has bitten a person usually counteracts the effects of
the venom. Most dangerous of all the poisonous snakes is the
dreaded cobra of India, Naja tripudians, a very vicious and
most deadly reptile. Twenty-five to 55 per cent, of cobra bites
prove fatal, and the annual loss of human lives in India from
this snake is often over 20,000. The sea-snakes, which inhabit
many tropical seas, attaining a length of six or eight feet, are
also very poisonous. The body is often compressed thus better
fitting them for their aquatic life. They do not leave the water
even to breed, but give birth to their living young while at sea.
The pythons, genus Python, which sometimes attain a
length of twenty or thirty feet, and the smaller boas or boa-
constrictors, Boa constrictor, are not venomous. They kill
their prey by coiling their body around it and crushing it.
These are tropical or semi-tropical snakes.

CHAPTER XXIV
BIRDS

The birds, class Aves, the most familiar and attractive of
wild animals, have been the object of so much attention and
study by professional naturalists, amateur nature students and
just nature lovers, that their classification, life history and
habits are better known than are those of any other animal
group.

About i2,ooo l different species of birds are known from all
the world, of which about 800 occur in North America. In
any single favorable locality in this country one can get ac-
quainted with from 100 to 200 species, counting in those
kinds that pass in the fall and spring migrations as well
as those that nest in the locality. The number of kinds
that may be called "all-year residents," that is, which
remain in the same region through the whole year, is, however,
very small, averaging usually about one-seventh of the total
number that may be seen in the region during the course of a
year. This limited number of kinds of birds in any one
locality, together with the bright colors and characteristic
manners which make their identification easy, the interest
of their songs and flight and their feeding, nesting and general
domestic habits, make birds excellent subjects for personal
field studies by students. And if the food habits are studied
from an economic point of view, valuable practical informa-
tion can be obtained during the study.

General Structure. The general body form and external
appearance of a bird are too familiar to need description.
The covering of feathers, the modification of the fore limbs

1 The British Museum Catalogue lists nearly 19,000 species but it
recognizes as full species about 7000 forms considered by most ornitholo-
gists to be merely varieties or sub-species.

18 273

274 ECONOMIC ZOOLOGY AND ENTOMOLOGY

into wings, and the toothless, beaked mouth are characteristic
and distinguishing external features. The feathers, although
covering the whole of the surface of the body, are not uni-
formly distributed, but are grouped in tracts called pterylce,
separated by bare or downy spaces called apteria. They are
of several kinds, the short soft plumules, or down feathers, the
large, stiffer, contour feathers, whose ends form the outermost

FIG. 126. A body feather and a wing feather from a chicken.

(Reduced.)

covering of the body, the quill feathers of the wings and tail,
and the fine bristles, or vibrissa?, about the eyes and nostrils,
called thread feathers. The fore limbs are modified to serve
as wings, which are well developed in almost all birds. How-
ever, the strange kiwi, or Apteryx, of New Zealand with hair-
like feathers is almost wingless, and the penguins have the
wings so reduced as to be incapable of flight, but serving
as flippers to aid in swimming underneath the water. The

BIRDS

275

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276 ECONOMIC ZOOLOGY AND ENTOMOLOGY

ostriches and cassowaries also have only rudimentary wings
and are not able to fly. Legs are present and functional in
all birds, varying in relative length, shape of feet, etc., to suit
the special perching, running, wading, or swimming habits of
the various kinds. Living birds are toothless, although certain
extinct forms, known through fossils, had on both jaws
large teeth set in sockets. The place of teeth is taken, as far as
may be, by the bill or beak formed of the two jaws, projecting
forward and tapering more or less abruptly to a point. In
most birds the jaws or mandibles are covered by a horny
sheath. In some water and shore forms the mandibular
covering is soft and leathery. The range in size of birds is
indicated by comparing a humming-bird with an ostrich.

Many of the bones of birds are hollow and contain air. The
air-spaces in them connect with air-sacs in the body, which
connect, in turn, with the lungs. Thus a bird's body contains
a large amount of air. The breastbone is usually provided
with a marked ridge or keel for the attachment of the large
and powerful muscles that move the wings, but in those
birds like the ostriches, which do not fly and have only rudi-
mentary wings, this keel is greatly reduced or wholly wanting.
The fore limbs or wings are terminated by three "fingers"
only. The legs have usually four toes, although a few birds
have only three toes and the ostriches but two.

As birds have no teeth with which to masticate their food,
a special region of the alimentary canal, the gizzard, is provided
with strong muscles and a hard and rough inner surface by
means of which the food is crushed. Seed-eating birds have
the gizzard especially well developed, and some birds take small
stones into the gizzard to assist in the grinding. The lungs
of birds are more complex than those of amphibians and rep-
tiles, being divided into small spaces by numerous membranous
partitions. They are not lobed, as in mammals, and do not
lie free in the body cavity, but are fixed to the inner dorsal
region of the body. Connected with the lungs are the air-
sacs already referred to, which are in turn connected with the
air-spaces in the hollow bones. By this arrangement the bird
can fill with air not only its lungs but all the special air-sacs

BIRDS 277

and spaces. The special function of these air-sacs in not un-
derstood; many believe that in some "way they aid the bird in
its flight or in respiration. The vocal utterances of birds are
produced by the vocal cords of the syrinx or lower larynx,
situated at the lower end of the trachea just where it divides
into the two bronchial tubes, the tracheal rings being here
modified so as to produce a voice-box containing two vocal
cords controlled by five or six pairs of muscles. The air passing
through the voice-box strikes against the vocal cords, the ten-
sion of which can be varied by the muscles. In mammals
the voice-organ is at the upper or throat end of the trachea.

The heart of birds is composed of four distinct chambers,
the septum between the two ventricles, incomplete in the
Reptilia, being complete in this group. There is thus no
mixing of arterial and venous blood in the heart. The sys-
temic blood circulation being completely separated from the
pulmonic, the circulation is said to be double. The circula-
tion of birds is active and intense; they have the hottest
blood and the quickest pulse of all animals. In them the
brain is compact and large, and more highly developed than
in amphibians and reptiles, but the cerebrum has no convolu-
tions as in the mammals. Of the special senses the organs
of touch and taste are apparently not keen; those of smell,
hearing, and sight are well developed. The optic lobes of the
brain are of great size, relatively, compared with those of other
vertebrate brains, and there is no doubt that the sight of birds
is keen and effective. The power of accommodation, or of
quickly changing the focus of the eye, is highly perfected.
The structure of the ear is comparatively simple, there being
ordinarily no external ear, other than a simple opening. The
organs of the inner ear, however, are well developed, and
birds undoubtedly have excellent hearing. The nostrils open
upon the beak, and the nasal chambers are not at all complex,
the smelling surface being not very extensive. It is probable
that the sense of smell is not, as a rule, especially keen.

Development and Life History. All birds are hatched from
eggs, which undergo a longer or shorter period of incubation
outside the body of the mother, and which are, in most cases.

2 78 ECONOMIC ZOOLOGY AND ENTOMOLOGY

laid in a nest and incubated by the parents. The eggs are
fertilized within the body of the female, the mating time of
most birds being in the spring or early summer. Some kinds,
the English sparrow, for example, rear numerous broods each
year, but most species have only one or at most two. The
eggs vary greatly in size and color-markings, and in number
from one, as with many of the Arctic ocean birds, to six or
ten, as with most of the familiar song-birds, or from ten to
twenty, as with some of the pheasants and grouse. The dura-
tion of incubation (outside the body) varies from ten to thirty
days among the more familiar birds, to nearly fifty among the
ostriches. The temperature necessary for incubation is about
40 C. (100 F.). Among polygamous birds (species in which
a male mates with several or many females) the males take no
part in the incubation and little or none in the care of the
hatched young; among most monogamous birds, however, the
male helps to build the nest, takes his turn at sitting on the
eggs, and is active in bringing food for the young, and in de-
fending them from enemies. The young, when ready to hatch,
break the egg-shell with the "egg-tooth," a horny, pointed
projection on the upper mandible, and emerge either blind
and almost naked, dependent upon the parents for food until
able to fly (aUricial young), or with eyes open and with body
covered with down, and able in a few hours to feed themselves
(precocial young).

Classification. The class Aves is usually divided into
numerous orders, the number and limits of these as published
in zoological manuals varying according to the opinions of
various zoologists. The rank of an order in this group is far
lower than in most other classes. In other words, the orders
are very much alike and are recognized mainly for the con-
venience in breaking up the vast assemblage of species. In
North America most of the ornithologists have agreed upon a
scheme of classification, which will therefore be adopted in
this book. This classification, together with a complete
catalogue of all North American bird kinds, is published by
the American Ornithologists Union as a "Checklist of North
American Birds." According to this classification the 800

BIRDS

279

(approximately) known species of North American birds
represent seventeen orders. Certain recognized orders, for
example, the ostriches, are not represented naturally in
North America at all.

Ostriches. The old order Ratitcz (now divided into several
smaller orders) or birds without keeled breastbone, as the

FIG. 128. Ostriches on ostrich farm at Pasadena, California.

ostriches, cassowaries, rheas, etc., is not represented naturally
in this country, but in California, Arizona, Florida, and a
few other states, the African ostrich, Struthlo camelus, is being
bred and reared on "ostrich farms" for the sake of its plumes.
This is the largest living kind of bird, specimens attaining
the height of eight feet and the weight of 300 pounds. The

280 ECONOMIC ZOOLOGY AND ENTOMOLOGY

eggs, which are five to six inches long and nearly as thick,
are laid naturally in shallow hollows scooped out in the sand
of the desert, and the hot sun and the male birds do most of
the incubating. The young hatch in from seven to eight
weeks, and can run about immediately.

Ostriches used to be hunted and killed for their feathers, but
since the discovery that they can be reared in confinement and
a superior quality of plumes thus obtained, their hunting has
been given up. They have been domesticated in South
Africa since about 1865, and now about half a million tame
birds exist there. The present annual value of the ostrich
plume output is about $10,000,000. Good average birds will
produce $50 worth of feathers a year, and are worth from
$700 to $1000 a pair. The plumes grow on the rudimentary
wings and tail, and the plucking does not hurt the birds in any
way.

Water and Shore Birds. The typical water birds include the
order Pygopodes, or loons, grebes, auks, etc. ; the Longipennes,
or gulls, terns, petrels and albatrosses; the Steganopodes, or
cormorants, pelicans, and boobies; and the Anseres, or swans,
geese and ducks. Among these the cormorants and gulls
are of some special use to man as scavengers along the sea-
shore, the gulls especially doing much to rid harbors of refuse
thrown overboard by the ships. But it is among the Anseres
especially that are found the water birds that interest the
economic zoologist particularly. The order includes about
sixty North American species, of which three are swans,
sixteen geese, and the rest ducks. In all, the bill is more or
less flattened and is also lamellate, i.e., furnished along each
cutting edge with a regular series of tooth-like ridges. The
feet are webbed and the legs short and set far back on the body,
an adaptation for effective swimming. The food consists of
roots and seeds of plants, worms, insects, small molluscs and
even small fishes, and only in occasional instances, as in the
invasion of grain fields by geese, are the food habits likely to
cause loss to man.

On the other hand, both geese and ducks are among our most
abundant and largest game birds, and certain species, such as

BIRDS 281

the Canada goose and the mallard, teal, pintail, widgeon,
shoveller or spoonbill, canvasback, redhead, bluebill and other
ducks, provide not only sport, but very enjoyable food during
the shooting season. Of these perhaps the most notable are
the mallard, which is primarily a fresh water duck and is the
ancestor of most of our domesticated races, and the canvasback,
a salt water species especially abundant from Chesapeake Bay
south along the Carolina Coast, and on the whole, more prized
for its flavor than any other duck. The special flavor of the
east coast canvasback may be due to its feeding largely on
wild celery ( Vail isneria) . To the uneducated palate, however,
the milder-flavored fresh water or river ducks will be more
enjoyable than the canvasbacks, redheads and bluebills of
the coast waters.

The wading and shore birds include the order Herodiones,
or ibises, herons and bitterns, the Paludicolce, cranes, rails and
coots, and the Limicolce, comprising the plover, curlew,
sandpipers and snipes. These orders include numerous game
birds such as the rails, woodcock, jacksnipe, various plovers,
curlews, yellowlegs and sandpipers. In rare instances cranes
may invade grain fields, but the food of most of the waders
is obtained from the marshes or bay and lake shores, and
consists chiefly of small animals, running all the way from frogs
down to insects. The rails, however, have a fondness for
seeds, especially wild rice, and the clapper rail and sora, or
Carolina rail, become very fat in the autumn and are much
hunted in the marshes of the South Atlantic States. The
woodcock frequents thick brush and covert in the Eastern States
and lies there concealed in daytime, issuing at dusk to search
for food on marshy ground. It is thus rather owl-like in habit
and with its big head and eyes is indeed rather owl-like in
appearance except of course for its long bill and snipe's legs.
Its flesh is highly esteemed, but in the absence of suitably
protecting game laws it has been so ruthlessly shot for market
that it is already a vanishing species. The jacksnipe, or Wil-
son's snipe, common over the whole country, is one of the best
known of game birds. It is a swift, erratic flyer, and fre-
quents open marshy ground. The golden plover is a special

282 ECONOMIC ZOOLOGY AND ENTOMOLOGY

favorite for its flesh but it has been so persistently shot that
its numbers have been greatly lessened.

The Pheasants and Doves ( Orders GallincB and Columba}.-
The Gall hue include most of the domestic fowls, as the hen,
turkey, peacock and guinea fowls. They include also the chief
game birds of most countries, as the grouse, quail, partridges,
wild turkey, ptarmigan, etc. They all have the bill rather

FIG. 129. The common Eastern quail, or Bob-white, Colinus mrginianus.
(Photograph by J. M. Slonaker.)

short, heavy, convex and bony, adapted for picking up and
crushing seeds and grains which compose their principal food.
They are mostly terrestrial in habit and are sometimes known
as the Rasores, or "scratchers." The eggs are numerous, and
are laid in a rude nest or simply in a depression on the ground.
In many of the species polygamy is the rule. The young are
precocial. Among the more familiar wild gallinaceous birds

BIRDS 283

are the eastern quail, or "bob-white," abundant in the eastern
and central United States, the ruffed grouse of the eastern
woods, and the prairie chicken of the western prairies. Besides
the bob-white there are five other quail species in this country,
all of which live in western and especially southwestern
regions. The examination of many stomachs has shown that
more than 50 per cent, of the food of all these quail is weed
seeds. The rest is composed of insects, some grains, and a
miscellany comprising leaves, buds, spiders, myriapods, crusta-
ceans, etc. The bob-white eats about 83! per cent, vegetable
matter and i6| per cent, animal matter. As the weed seeds
and insects together compose the major part of the food, quails
are far more beneficial than hurtful to the farmer.

The doves and pigeons constitute the small order Columbcs,
closely related to the Gallina. The bill is covered at the base
by a soft swollen membrane, or cere, in which the nostrils open.
The food consists of fruits, seeds and grains. The most
familiar wild species is the mourning dove, or turtle dove, which
occurs all over the country, and is shot as a game bird in some
states. The beautiful passenger pigeon, formerly extremely
abundant, moving about in enormous flocks in the eastern and
central states, has been exterminated by ruthless killing. All
the various kinds of domestic pigeons such as pouters, fantails
carriers, ruff-necks, tumblers, etc., are believed to be the modi-
fied descendants of the common European rock dove, Columba
lima.

Other Land Birds. Of the other land birds, besides the
GalliiKB and Columbce, about one-half belong to the order
Passeres. or perching birds. The others are distributed among
the orders Raptores, or birds of prey, Pici, or woodpeckers
Coccyges, or cuckoos and kingfishers, Macrochires, or whip-
poorwills, chimney-swifts and humming-birds, and the
Psittaci, or parrots, of which but one species, the small Caro-
lina parroquet, exists wild, in small numbers, in the United
States. It is found only in Florida.

The Raptores include the eagles, hawks, vultures and owls,
and their food habits make them on the whole decidedly bene-
ficial birds. Of the fifty or more species of eagles and hawks

284 ECONOMIC ZOOLOGY AND ENTOMOLOGY

found in this country only a few kinds ever raid barnyards or
pastures, while the same kinds, together with all the others,
make way with many noxious rodents and large insects, such
as grasshoppers, crickets and June bugs. Their captures of
other birds are, however, mostly to be deplored, and two species
of small hawks, Cooper's hawk and the sharp-shinned hawk,

FIG. 130. Red-headed woodpecker, Melanerpes erythroccphalus, young at
opening of nest to receive food from the mother. (Photograph by J. M.
Slonaker.)

deserve to be shot on sight, for they feed almost entirely on
wild birds and poultry.

There are twenty-three species of woodpeckers in the
United States, and the food of twenty of them consists chiefly
of insects, usually wood-boring grubs. These birds do much
good by destroying many insect pests of trees. But there
are three kinds, with short brushy tongues not adapted to

BIRDS 285

the capture of insects, which do some injury to trees by feed-
ing on the live bark and sap of trees. More than two hundred
and fifty kinds of trees, shrubs and vines are attacked by these
sap-suckers. They are especially fond of and, hence, hurtful
to hickory trees. The common sap-sucker of the western
states is the only woodpecker in that region that has the whole
head and throat red, while the common one of the middle and
eastern states is the only one having the front of the head from
bill to crown red and a black patch on the breast. By these
marks these two injurious woodpeckers can be distinguished
from the others, all of which are beneficial.

The Passeres include the familiar song birds and the great
majority of the birds of the garden, the forest, the roadside
and the field. The feet of these birds always have four toes
and are fitted for perching. The syrinx, or musical apparatus,
is well developed in most of them. Nesting and domestic
habits are various, but the young are always hatched in a
helpless condition, and have to be fed and otherwise cared for
by the parents for a longer or shorter time. The North Ameri-
can species of this order are grouped into eighteen families,
as the fly-catcher family (Tyranmdce), crow family (Corvidd),
the sparrows and finches (FringiUidce) , the swallows (Hirun-
dinidee), the thrushes, robins and blue birds (Turdidtz), etc.
In this small book nothing can be said of the various species
which belong to this order. However, as the Passerine birds
are those which immediately surround us and which, by
their familiar songs and nesting habits, most interest us, the
outdoor study of birds by beginning students will usually
be devoted chiefly to the members of this order, and many
different kinds will soon become familiar. The robin and
blue bird will introduce us to their shy and familiar relatives,
the song thrushes; the study of the king bird or bee-martin
will interest us in some of the other fly-catchers. From the
familiar chipping sparrow and tree-sparrow we shall be led to
look for their cousins the swamp- sparrows and the larger
grosbeaks and crossbills, and so on through the order.

Determining and Studying the Birds of a Locality. To
identify the various species of birds in the locality of a school

286 ECONOMIC ZOOLOGY AND ENTOMOLOGY

it will be necessary to have some book giving the descriptions
of all or most of the species of the region, with tables and keys
for tracing out the different forms. Such bird manuals and
keys are numerous now, as, because of the popular interest
in bird study, many bird books have been published in the
last few years. The best general manual is Coues' "Key
to the Birds of North America" (sth ed., 2 vols.). Chapman's
"Handbook of the Birds of Eastern North America," and
Florence Bailey's "Handbook of Birds of Western United
States," are each complete for the regions covered by them.
There are other books that attempt to make it possible by keys
based chiefly on color and pattern differences to distinguish
the birds without having their dead bodies actually in hand,
which usually means shooting the bird. There are several
magazines devoted to accounts of the life and habits of birds.
Of these "Birdlore" is the organ of the Audubon Society for
the Protection of Birds, and is an accurate but popular and
beautifully illustrated journal. Fig. 127 will aid the stu-
dent in the use of any of these bird books by making him
acquainted with the names of the various external parts and
special plumage regions of the bird's body.

Birds and Seasons, In trying to become acquainted with
the birds of a locality it must be borne in mind that the bird-
fauna of any region varies with the season. Some birds live
in it all the year through; these are called residents. Some
spend only the summer or breeding season in the locality, com-
ing up from the South in spring and flying back in autumn;
these are summer residents. Some spend only the winter in
the locality, coming down from the severer North at the be-
ginning of winter, and going back with the coming of spring;
these are winter residents. Some are to be found in the
locality only in spring and autumn, as they are migrating north
and south between their tropical winter quarters and their
northern summer or breeding home; these are migrants. And,
finally, an occasional representative of certain bird species,
whose normal range does not include the given locality at all,
will appear now and then, blown aside from its regular path
of migration, or otherwise astray; these are visitants. As to

BIRDS

287

the relative importance, numerically, of these various cate-
gories among the birds which may be found in a certain region,
and thus form its bird-fauna, we may illustrate by reference
to a definite region. Of the 351 species of birds which have
been found in the state of Kansas (a region without distinct
natural boundaries, and fairly representative of any Mississippi
valley region of similar extent), 51 are all-year residents, 125
are summer residents, 36 are winter residents, 104 are migrants,
and 35 are rare visitants.

\

FIG. 131. Nest of song sparrow (Melospiza cinercd).
(Photograph by J. H. Paine)

The all-year residents and the summer residents, comprising
about one-half of the species to be found in a locality, are the
only ones which breed there, and which thus present oppor-
tunity for observations on their nest-building habits and care
of the young. Numerous suggestive questions present them-
selves in connection with breeding. Why is it that some
species nest early and some late? Can the character of the
food of the young have anything to do with this? If so, what?
Does the condition of the particular trees, bushes or other
favorite sites for nests help determine the nesting time? Why

288 ECONOMIC ZOOLOGY AND ENTOMOLOGY

should some birds raise but one brood a year, and others two
or even three? Does the fact that a bird is an all-year resident
or only a summer resident have any influence in determining
its nesting time and the number of broods it rears? Compare
the habits of the various breeding species of the locality, and
find out if the summer residents have any breeding habits in
common as distinguished from the all-year residents.

Observe the behavior of the birds in courting time. Do the
males have "singing contests," as is sometimes reported? Do
they fight with each other? Do the males or females show any
differences, at this time, from their more usual plumage?
After mating which bird selects the nesting site? Are old
nesting sites preferred to new ones? If two broods are reared
is a new nest built for the second one? What are the principal
causes of mortality among the eggs and young during the breed-
ing season ? What instincts or habits of the parents have direct
reference to these dangerous conditions? What means of
protecting the nest are resorted to? What is the behavior of
the parents toward enemies of the young?

Distribution and Migration. The geographical distribu-
tion of animals is a subject of much importance, and offers
good opportunities in its more local features for student field-
work. The field-study of the birds of a given locality will
comprise much observation bearing directly on zoogeography, or
the distribution of animals. Certain birds will be found to
be limited to certain parts of even a small region; the swimmers
will be found in ponds and streams, and the long-legged shore
birds on the pond- or stream-banks, or in the marshes and
wet meadows, although a few, like the upland-plover, curlews,
and god wits are common on the dry upland pastures. Dis-
tinguish the ground birds of the shrubs and hedge-rows, and
these again from the strictly forest birds. Find the special
haunts of swallows and king-fishers. Which are the shy birds
driven constantly deeper into the wild places, or being ex-
terminated by the advance of man? Which birds do not re-
treat, but even find an advantage in man's seizure of the land,
obtaining food from his fields and gardens?

Make a map on large scale of the locality of the school,

BIRDS 289

showing on it the topographic features of the region, such as
streams, ponds, marshes, hills, woods, springs, wild pastures,
etc., also roads and paths, and such landmarks as school-
houses, country churches, etc. On this map indicate the local
distribution of the birds, as determined by the data gradually
gathered; mark favorite nesting -places of various species,
roosting-places of crows and black-birds, feeding-places, and
bathing- and drinking-places of certain kinds, the exact spots
of finding rare visitants, rare nests, etc.

As already mentioned, many of the birds of a locality are
" migrants," that is, they breed farther north, but spend the
winter in more southern latitudes. These migrants pass
through the locality twice each year, going north in the spring
and south in the autumn. They are much more likely to be
observed during the spring migration than in the fall, as the
flight south is usually more hurried. The observation of the
migration of birds is very interesting, and much can be done
by beginning students. Notes should be made recording the
first time each spring a migrating species is seen, the time
when it is most abundant, and the last time it is seen the same
spring. Similar records should be made showing the move-
ments of the birds in the fall. A series of such records, cover-
ing a few years, will show which are the earliest to appear,
which the later and which the last. Such records of appear-
ance and disappearance should also be kept for the summer
residents, those birds that come from the south in the spring,
breed in the locality, and then depart for the south again in
the autumn. Notes on the kinds of days, as stormy, clear,
cold, warm, etc., on which the migration seems to be most
active; on the greater prevalence of migratory flights by day
or by night; on the height from the earth at which the migrants
fly, etc., are all worth while. For an excellent simple account
of migration see Chapman's "Bird-Life," Chapter IV. A
more detailed account of migration, and one giving the records
for many species at many points in the Mississippi Valley, is
Cooke's "Bird Migration in the Mississippi Valley."

Plumage. It must be kept in mind in using bird-keys and
descriptions to determine species that the descriptions and
19

2 9 o ECONOMIC ZOOLOGY AND ENTOMOLOGY

keys refer to adult birds, and in ordinary plumage. Among
numerous birds the young of the year, although old enough to
fly and as large as the adults, still differ considerably in plumage
from the latter; males differ from females, and finally both
males and females may change their plumage (hence color
and markings) with the season. The seasonal changes of
plumage accomplished by molting may be marked or hardly
noticeable. "All birds get new suits at least once a year,
changing in the fall. Some change in the spring also, either
partially or wholly, while others have as many as three changes
perhaps, to a slight extent, a few more. ... It is claimed
by some that now all new colors are acquired by molt, and by
others that in some instances (young hawks) an infusion or
loss, as the case may be, of pigment takes place as the feather
forms, and continues so long as it grows."

There is much lack and uncertainty of knowledge concern-
ing the molting and change of plumage by birds, and careful
observations by bird students should be made on the subject.

For accounts of the plumage and color of birds see Chapter
III in Chapman's "Bird-Life" and Chapters VIII and IX in
Baskett's "Story of the Birds."

Structure and Habit. In connection with learning the dif-
ferent kinds of birds in a locality, observations should be made,
and notes of them recorded, on their habits, and on their ex-
ternal structure and its relation to the habits of the bird.
The interesting adaptation of structure to special use is particu-
larly well shown in the varying character of the bill and feet
of birds. The various feeding habits and uses of the feet of
different birds are readily observed, and the accompanying
modification of bills and feet can be readily seen in birds pre-
served as "bird-skins." In some cases the general structure
of feet and bills may be seen in the live birds by the use of an
opera-glass. The characters of bills and feet are much used
in the classification of birds, so that any knowledge of them
gained primarily in the study of adaptations will have a
secondary use in classification work.

Note the foot of a robin, bluebird, catbird, wren, warbler, or
other Passerine or perching bird. It has three un webbed toes

BIRDS 291

in front and a long hind toe perfectly opposable to the middle
front one. This is the perching foot. Note the so-called
zygodactyl foot of the woodpecker, with two toes projecting
in front and partly yoked together, and two similarly yoked
projecting behind. Note the webbed swimming foot of the
aquatic birds; note the different degrees of webbing, from the
toti-palmate, where all four toes are completely webbed, pal-
mate, w r here the three front toes only are bound together but
the web runs out to the claws, to the semi-palmate, where the
web runs out only about halfway. Note the lobate foot of
the coots and phalaropes. Note the long slender, wading
legs of the sandpipers, snipe, and other shore-birds; the short,