KELLOGG AND

BY THE SAME AUTHORS
BY VERNON LYMAN KELLOGG

ELEMENTARY ZOOLOGY

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FIRST LESSONS m ZOOLOGY

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DARWINISM TODAY

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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

SO|l 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. YORK- PA

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

2056240

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 AMOEBA 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

XI. 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

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 boyli.

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.

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 writh 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 showr 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 skull 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^
fronio-parietal..

pterygoid-J.A,

cervical vertebra^
clavicle —

splieno-ethnnrid
maxillary

digits

ex-occipital

supra-scapula

"-carpels

radio-ulna

sacral vertebra

'—-calcaneum

/

U tibio-fibula

astragalus
FIG. 3. — Skeleton of garden toad.

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 tar sal bones,
the astragalus and calcaneum, 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
sympathetic 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, Melanoplus fcmur-rubrum;
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

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

antennas

auditory organ
ocellus I

•! head Compound eye /

—ovipositor

femur>
tibia'''

tarsal segments

FIG. 5. — The red-legged locust, Melanoplus femur-rubrum, 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

16 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 antenna?, 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 maxillae, 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 tar sal 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 pulmllus. 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 caca 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 tracheae
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 deferentia,
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.

Hydrae 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

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.

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 cnidocil. 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 Hydras
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. protos, 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

FIG. 8. — Amceba 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 Amceba
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 out 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.

Amoebae 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 Amoeba 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.

Paramoecium. — 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 Paramoecia 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 Paramoecium 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
Amcebae 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 Amcebae. 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.
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

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

ONE-CELLED ANIMALS

31

is a breaking up of the nuclei and a part of the micronucleus
of each individual passes over to the other. Then the Para-
moecia 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 peristome, and the central disk, the
epistome, are fringed with rather long
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-

F I G . i o . — Vorticella
sp. One individual with
stalk coiled, and one
with 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 Paramoscia 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, Rosalind varians (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 wrere 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 deviated 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 Amoeba, 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 Spirochcetce, 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 Volvox,
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.)

3 8 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 amoeboid 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 amoeboid 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 wrork 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 simple1 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 Linnaeus,
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

50 ECONOMIC ZOOLOGY AND ENTOMOLOGY

inclusiveness, which he called, species, genus, ordo and classis.
We still use Linnseus'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 work.

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, Merula,
and the house-fly genus, Musca.

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-
loria, 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 Canis 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 Felidce, 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 Canidae
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 Cams and
that is a member of the family Canidae, 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 wre are referring to, when we simply
say or write Canis familiaris.

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 Canis occidenialis 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 maximtis, 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. Rhizfip'oda (amoeba, Heliozoa, Radiolaria, Foraminif-

era, et al.).

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

Spirochata, et al.).
Class IV. Spdrozo'a (parasitic Protozoa such as Plasmodium

which causes malaria, Babesia which causes Texas

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

with cilia, Paramoecium, Vorticella, et ah).

BRANCH II. PORIF'ERA (sponges)
Class I. For 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. Scyphdzo'a (sl-fo-zo'-a) (most of the large jelly-fishes).
Class III. Actlnozo'a (sea-anemones; most of the corals, et al.).
Class IV. CtSndph'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. Cesto'da (tape- worms).

BRANCH V. NEMATHELMlN'THES (round-worms)

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

Class II. NematomSr'pha (horse-hair snakes, or cabbage- snakes,

et al.).

Class III. Acanthoceph'ala (thorn-headed worms).
Class IV. Ch(zt8g'natha (ke-tog'-na-tha) (arrow- worms).

56 ECONOMIC ZOOLOGY AND ENTOMOLOGY

BRANCH VI. TROCHELMIN'THES (wheel-worms)
Class I. Rotifer a (wheel animalcules).

BRANCH VII. M(3LLUSCOI'DA

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

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

Class II. Phord'nida (worm-like animals living in sand).
Class III. Br&chiop' 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. Aster oi'dea (starfishes).

Class II. Ophiuroi'dea (brittle-stars).

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

Class IV. Hdlothur oi'dea (sea-cucumbers).

Class V. Crlnoi'dea (sea-lilies, or feather-stars).

BRANCH IX. ANNEL'IDA (segmented worms)

Class I. Archiannffl ida (marine worms living in the sand).

Class II. Chcetdp'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. Hirudlriea (leeches)

BRANCH X. ARTHR^P'ODA

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

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

Class II. Onychdph'ora (slime-slugs).

Class III. Myri&p'oda (myriapods, centipedes, et al.).

Class IV. Insec'ta (insects).

Class V. Arach'nida (scorpions, spiders, mites and ticks).

BRANCH XI. M6LLUS'CA

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

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

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

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

Class IV. Pelcc^p' oda (clams, mussels, oysters, scallops, et al.).

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

THE CLASSIFICATION OF ANIMALS

57

BRANCH XII. CHORD A 'TA

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

Class I,

Class II.

Class III

Class IV

Class V.

Class VI.

Class VII.
Class VIII.

Class IX.

Adelochor'da (balanoglossids, et al.).

Urochor'da (ascidians, et al.).

Leptocard'ii (lancelets).

Cyclostdm' ata (lampreys and hagfishes).

Pisces (pis-sez) (fishes).

Amphib'ia (frogs, toads, salamanders, water-dogs,

et al.).

ReptU'ia (snakes, lizards, turtles, alligators, et al.).
A'ves (birds).
M&mmdl'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 be1 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, Lencandra 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 wast^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
spongin. 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 Porifera (L. porus, 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 Coelenterata (Gr. koilos, hollow; enter on,
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
medusae 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 water, 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

70 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. 18. — 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
turn produce other rediae. The rediae finally
give rise to certain heart-shaped bodies each
with a long flexible tail. These are called cer-
carice, 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. 19. — Liver-
fluke, Fasciola
hepatica. (Nearly
twice natural
size.)

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, Tania 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 Tania 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

FIG. 22. — A piece of a muscle of the ox, with
three specimens of the tape-worm, Tcenia saginata,

ir* £»rn-»irc forl oforro ^AJof ni-ol oi^d« o f f Of Ocf OT-V*«l»/r ^

tape-worm, T &nia inree specimens 01 cne tape-worm, i wma- saginaia,
saginata. (Highly in encysted stage. (Natural size; after Osterberg.)
m a g n i fi e d ; after
Wood.)

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 midticeps, 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, Midticeps midticeps, from the intestine of
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 larvae
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
thousands or millions of these little parasties often
causes great suffering, sometimes death to the host.
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

79

FIG. 25.
vinegar-eel,
A n guillula
sp. (Great-
1 y magni-
fied; from
a living
specimen.)

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

pIG 26. Encapsuled Ascaris are several round- worms, or

trichinae in trunk muscle "eel- worms," some of which are very

°-fiPig- JGBatly f ag~ common and of considerable economic
nified; after Braun.;

importance. The large-headed thread-
worm, Ascaris 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

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
feces 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, FILARIA, 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 which 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 FlG- 29.— Microfilaria
,11 i r-i j~i of the blood: immature

the larval filariae, or microfilariae, are stage of Fila'ria bancroftL

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 medinensis, 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 Ch&tognatha (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, Lack-
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
maturing of all the grubs that are infected.

Several other species belonging to this
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

FIG. 30. — A
wheel animalcule,

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 caeca. 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.

90 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

nuscles of the fylorif caeca,

musclei of the pyloric caeca

eye spot --J

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 caca,
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 ampullae 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 peri-visceral 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

epithelium of the body ' ** """" "

cavity

mesentery-
pyloric caecumr

—ossicles

— ampulla

tube fool

ambulacral ossicle

ectodermal covering —

\M

/ I
Hb x

pedicellaria — •

. radial 'canal /
radial blood-vessel

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

starfish, Asterias 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 franciscanns, 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, Cucumaria frondosa. (About
j 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 Echinoidea (Gr. echlnos, hedgehog;
eidos, likeness), look quite unlike the starfish. The body is

96 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, Pcntacrinus sp. (About i 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 arid 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 pinnules 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; fious, foot) including the earth-
worms and many marine worms; the Hirudinea (L. hirudo,
leech) or leeches; and the marine Archiannelida (Gr. archi-,
primitive; annellus, little ring) and Gephyrea (Gr. ' gephyrd,
bridge).

The Earthworm. — In the Chcetopoda 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 clitellum. 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 ccdom. 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.

ioo ECONOMIC ZOOLOGY AND ENTOMOLOGY

cerebral ganglion

retractor and protractor
muscles of the pharynx

cesophageal pouches— «
seminal receptacle
seminal

aniis \

pharynx
psophagua

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.

nephridium f^rsal ttotd vessel

\ hepatic cells /

\ \ i longitudinal muscle

'. \ / firmlnr miiscle fit

I/

ft jcircular muscle fibres
epidermis
.cuticle

typhlosole

nephridipore ! nephrostome \

• ventral vessel

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 cronjhelmi, the upper right-hand one a nereid, Nereis sp., the lower
right-hand one, Polynce brevisetosa. (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

io4 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-
FIG. 40.— The posed of many segments. Most of the seg-

medicinal leech, ments are marked by transverse lines, making
Hirudo medtcina- fU0 • i u

Us. (Grows to be tne ammal appear to have many more seg-
six or eight inches ments than it really has. The ventral side is
long>) 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-

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 t° 57> fiye 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

1 06

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 canaK 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 antennas. 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 oimaxilli-
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

-uropod
-telson

FIG. 41. — Ventral aspect of female crayfish, Cambarus 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 where 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

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 defer entia 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-ckss 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

ii4 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 Cetochilus 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.
The animal is enclosed in a shell
often of the shape of a truncate

FIG. 44. — A stalked barnacle,
Lepas hillii. (About | natural
size.)

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-

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 vulgaris, 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 Hippa, 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, Litmdus, 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
doing a great deal of damage.

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 Myriapoda1 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 antennas.
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 ei-
seni (Mex-
ico). (Length

tw°

i24 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 \vith 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 „ ,

... . ., .., ,, ,. scolo pendra sp. (.Natural

Insects, to contrast it with the earlier size ^

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.

FIG- 49-— A centipede

i26 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 or 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 antennae, 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 antennae 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 antennas 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 F _M ,

segment, of chitin rods, delicate nerve parts of a honey-bee

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

tory nerve running to the brain. The ££.*& ±-£

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

loped auditory apparatus of this type. maxillary palpus; mx.L,
Af. , ,, i maxillary lobe; st.,

A few insects, such as the grasshopper, stipes of maxjna;

katydids, crickets and others have a

cardo of

very different kind of "ear," not situated !abium;
•' turn of

maxilla; II.,
w., submen-
labium; m.,
mentum of labium; pg.,

,,,.,

on the head, but on the abdomen (in

the grasshoppers), front legs (in katydids paraglossa. gl., glossa;
and crickets), or elsewhere on the body. Kp'' labia palpus'
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

1 3o 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,
Pteroslichus calif ornicus; 2, from a carrion beetle, Silpfu. ramcsa; 3, from a
click beetle, Melanotus variolatns; 4, from a honey-bee, Apis mellifica;
5, from a Scarabaeid beetle, Ligyrus gibbosus; 6, from a blow fly, Calli-
phora •vomitora. (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.

--on

FIG. 53.— Lon-
gitudinal section
through a few
Most of the light rays that enter each om- facets and eye-ele-
matidium must be those that fall nearly ver- ments (ommati-
..11 Ai 11 j ^ dia) of the com-

tically on the external lens, and pass verti- poun(j eye of a

cally in to the sensitive rhabdome. Thus moth. /., cor-

each ommatidium "sees" only any object or neal facets; cc.,

. J J J crystalline cones;

part of any object directly in the line of its p.^ pigment; r.,

long axis, and as the surface of the compound retinal parts; o.n.,
eyes of insects is usually strongly curved, ?^f^gr nExner:
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.

i32 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-
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
ccelli 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-

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

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," ff, 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

i34 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
piilvillus, 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 which 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 grsup 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 many 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 two-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 OF 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

i38 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

i4 2 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 vitelline 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 copulatrix.

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 lias deferens,
through which the spermatozoa
pass to reach the single ejaculatory
duct, from which they are expelled
by the male at mating.

TYPES OF 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. FIG. 59. — Honey-bee, Apis
And very different from either of mdlifica, reproductive organs,
,, . ,, ,, sting and poison glands of

these, again, are the mouth-parts que*n) dors£ view 6 (Greatiy

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

i44 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; e, labium; m.x p., maxillary palpi; I. p., 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, Serphus dilatatus. 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 is sucked up the sheath into the mouth. The

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-epipharynx 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, Culex sp. lep.,
Labrum-epipharynx; md., man-
dible; mx.L, maxillary lobe;
mx.p., maxillary palpus; hyp.,
hypopharynx; li., 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; li., 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-

FIG. 64.-SphinX moth, showing pro- Cnt .in the Same insect
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 <.!,•••
figure natural size; small figure twice natu- the mjunes caused by
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
RedumidcB, order Hemiptera). A, Young just hatching from eggs; B,
young after first molting, snowing 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

1 50 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
plexippus. 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

154 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, antennas, 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

Wings membranous.

PLECOPTERA
ODONATA

ISOPTERA
CORRODENTIA

Fore wings parchment-like / ORTHOPTERA

I EUPLEXOPTERA

Wingless MALLOPHAGA

With sucking mouth-parts / HEMIPTERA

I THYSANOPTERA
Metamorphosis complete.

With biting mouth-parts. f NEUROPTERA

With wings membranous I M*COPTERA

I TRICHOPTERA

With fore wings thickened COLEOPTERA

With sucking mouth-parts LEPIDOPTERA

With lapping or piercing and sucking mouth- j ^IPTERA

parts. SlPHONAPTERA

' 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

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, Smynthurus 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 Le-
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 Thysanura 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
filaments rising from the thoracic seg-
ments, one tuft just behind each leg.
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.

FIG. 70. — Young
(nymph) of stone-fly,
from California. (Twice
natural size.)

i58 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.
the lower lip extended. (Natural size.)

Showing

Order Isoptera. — -The order Isoplera, 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 flampes, 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 Atropidae 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 divinatoria 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.)

i6a 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,
except the cicada or harvest flies. The
insects in these three singing families are
also the best known leaping insects, the
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 Mantidce) are, however, predaceous,
preying on other insects, and the cockroaches (family Blattidia)
prefer dried vegetable or animal matter. The metamorphosis
is incomplete, and the young, which resemble the parents

FIG. 75. — A biting
louse of pigeons, Lip-
eurus baculus. (Na-
tural size indicated
by line.)

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-

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 Hemiptera 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 Homoptera, winged
species with fore and hind wings of the same texture through-
out and usually held sloping or roof-like over the back; and

FIG. 77. — A water-bug, Serphus dilatalus. (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 Hetero ptera the squash-
bugs, chinch bugs, water-boatmen, assassin-bugs and stink-
bugs; while the Homoptera 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.

1 66 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, Myrmeleon 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

1 68 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 Trichoptera, 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
larvae 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. 79. — Water-
tiger, the larva of the
predaceous water-bee-
tle, Dyttcus sp. (Nat-
ural size.)

FIG. 80. — The predaceous water-beetle, Dy-
ticus 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 antennas 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. 8 1. — Horse-fly, Tabanus punctifer. (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

1 72 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-
and 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

i73

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

Human-flea, Pulcx irritans; male.

proved to disseminate the germs of plague among rats (see
Chapter XXIX). The commonest fleas affecting man are
the human-flea, Pidex 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.

i74 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 unjointed 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, Tropasa luna.
(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 antennae slender, and with slightly expanded
or hooked tip; and the Heterocera, or moths, most of which
are night fliers, and which have their antennae 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 Tenthredinida)
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, Proctotrypida,
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
an important kind is the curious small fig-
wasp (Blastophaga) by which the Smyrna
figs are cross-pollinated and made to set
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 papillae on the

FIG. 85. — Ichneu-
mon fly, Pimpla con-
qidsitor, laying egg in
cocoon of American
tent-caterpillar moth.
(About natural size;
after Fiske.)

i82 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 larva?,
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

i84 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 with the oncoming of winter
SP' <Fr°m ^e 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

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-
» jg sary function at all in the commu-

... nal economy; the workers build
FIG. 89— Honey-bee, Apis / '

mellifica. 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

1 88 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 conies 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.)

ig 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

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

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 195

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 larvas of the bee moth, Galleria mellonella. (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, Galleria mellonella, or the "small" bee-moth,

196 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

i98 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 larvae 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 d); 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 defined 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 pver delicately spun webs. The pedipalpi, or feet-

206

207

like palpi, are sometimes one-fourth to one-half as long as the
legs. The mandibles, or chelae, 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
man. A few species, however, are very venomous, and a bite
from one of them may result in great suffering, rarely in

FIG. 94. — Web of an orb- weaver, Zilla calif ornica; 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

2o8 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, Agalena 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

14

210 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 variegatum; 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, Ornithodorus 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, Tetranychus 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,

2i4 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
colonies, feeding on the skin and
causing crusts or scabs. The in-
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 co'mmunis 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.

FIG. 98. — Itch-mite, Sar-
coptes scabiei, female, dor-
sal aspect. (Greatly mag-
nified; after Fiirstenberg.)

SCORPIONS, SPIDERS, MITES AND TICKS 215

The common chicken-mites, Dermanyssus gallinaz, 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. But 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 umbo, 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 K

right auricle

anterior aorta \ \
reno-perlcardial aperture ^

renal aperture ..
genital aperture x

umbone
hinge tooth--.

stomach-
digestive gland.

gullet

cerebw-plc'iiral ganglion - -.$'-.*
month —

anter adductor^'

anter retractor ,
pedal ganglion

foot

intestine'"
typhlosole''

Fir,. 99. — Dissection of ;i fn

ventricle

pericardium

rectum
^kidney

f,* '-dorsal pall/al aperture
.- posterior aorta
i post, retractor

mantle

mantle cavity

post adductor
anus

visceral ganglion

exhalant siphon
super branchial chamber

- right gill

-inhalant siphon

shell

•pallial groove

ter 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
(interior 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

218 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-pleural 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 bookless 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 th,e 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 £he 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 (Atax), 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
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. pdekys, 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. 100. — A chiton, Isch-
nochiton magdalenen sis .
(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 byssus, 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, Mytilus 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.— Soft-shell
clam, Mya arenaria L.
(Reduced.)

FIG. 103. — A geoduck or
giant cla.m,Glycimeris generosa,
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, Schizotharus 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 rjund 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 tnat 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
15

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 lurida, 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 edulis, occurs along the northern
shores, and in many respects resembles our Pacific coast oyster.
Like the latter it is hermaphroditic. The Portuguese oyster,
0. 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
corning 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

23o 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' '
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. 1 06. — The giant yellow slug of California, Ariollmax 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 writh 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-

23 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 lamellosa. (Reduced.)

lewis I,

and used for food. Many Muricidce when crushed exude a
reddish-purple fluid which in olden times was used as a dye
famous under the name of Tyrian purpJe.

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).

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 apollyon. (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 opalescens 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 noiochord, 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

23?

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. leptos, 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, Reptilia (L. repo,

FIG. 112. — A lamprey, Petromyzon marinus. (After Goode.)

to creep), or turtles, snakes and crocodiles, AvesCL. avis, 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.

240 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 operculum, the posterior margin of which

swim-bladder

nostrils

lateral line

gill-rakers

bladder I 9\. * ~>
V
\

opercular flap
1 liver

I ventricle
conus artcrioxi'x

Fir.. 113. — Dissection

dorsal fa ^ ,, fav!ty °f tfie *<>'"» -

t,' kidney

^urinary bhtddcr
opening from kidneys

body mmcles

jlden 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

24 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. Icevis, 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 Acipenserida, 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 Lepisosteida, 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 Catostomida, 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 Cyprinidoe 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 Leptocephalida, are scaleless, occur
in the sea at moderate depths, and are little used as food in
America.

The family Clupeidce 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 Salmonida, 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 Oncorhynchus, 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 sock eye 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

251

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 irideus.

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 Sahelinus 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 Argentinida, are also closely related to the
Salmonida. 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 Esocida, 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 Mugilidce, 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 wholly 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 CentrarchidcB 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 Serranida. 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 Embiotocida, 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 Pleuronedidte. 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, Pseudoplenronectes 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}. — This 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
coecilians, 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 Apoda, or footless, snake-like forms, the Urodela,
or tailed amphibians, and the Anura, or tailless forms like the
toad and frog.

The Coecilians (order Apoda). — 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 Necturus, 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 tigrimim is an
interesting and widely distributed common species. In
some regions the larval form, known as axolotl, reaches
a large size and produces young before completing the
usual metamorphosis.

FIG. 117. — A brown salamander, N oto phthalmus torosus. (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

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 Bufonida,
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, Reptilia, 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

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 vertebrae; 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 Rhynchocephalia, 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. 119. — -The giant land-tortoise of the Galapagos Islands, Testudo 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 serpentina, 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 lacerlina, 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, M alacoclemmys 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 hunted. 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 mydas. 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, Gamalis 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 Sauria, 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. 1 20. — A fence lizard, Sceloporus occidentalis.

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

FIG. 121. — The Gila monster, Hcloderma suspectum, 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 scutes, 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 larva 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 Heterodon,
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

27o 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 zoo 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

ducing 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,oool 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 vibrissae, 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

a

.2
P

o

£

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.

278 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 (altricial 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 Ratitas (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, Struthio 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 Paludicola, cranes, rails and
coots, and the LimicolfS, 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 Gallina and Columbce). —
The Gallina 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 virginianus.
(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 Columba,
closely related to the Gallince. 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
Gallina and Columba, 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 (Tyrannidce) , crow family (Corvidce),
the sparrows and finches (Fringillidce) , the swallows (Hirun-
dinidce), the thrushes, robins and blue birds (Turdidce), 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 cinerea).
(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 godwits 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

29o 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 unwebbed 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, where 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,
heavy, strong leg of the divers; the small weak leg of the swifts
and humming-birds, almost always on the wing;' the stout,
heavily nailed foot of the scratchers, as the hens, grouse, and
turkeys; and the strong, grasping talons, with their sharp, long,
curving nails, of the hawks and owls, and other birds of prey.
In all these cases the fitness of the structure of the foot to the
special habits of the bird is apparent.

Similarly the shape and structural character of the bill
should be noted, as related to its use, this being chiefly con-
cerned of course with the feeding habits. Note the strong,
hooked, and dentate bill of the birds of prey ; they tear their
prey. Note the long, slender, sensitive bill of the sandpipers;
they probe the wet sand for worms. Note the short, weak
bill and wide mouth of the night-hawk and whippoorwill,
and of the swifts and swallows; they catch insects in this wide
mouth while on the wing. Note the flat, lamellate bill of the
ducks; they scoop up mud and water and strain their food from
it. Note the firm, chisel-like bill of the woodpeckers; they
dig into hard wood for insects. Note the peculiarly crossed
mandibles of the cross-bills; they tear open pine cones for seeds.
Note the long, sharp, slender bill of the humming-birds; they
get nectar and insects from the bottom of flower-cups. Note
the bill and foot of any bird you examine, and see if you can
recognize their special adaptation to the habits of the bird.

The most casual observation of birds reveals differences in
the flight of different kinds so characteristic and distinctive

292 ECONOMIC ZOOLOGY AND ENTOMOLOGY

as to give much aid in determining the identity of birds in
nature. Note the flight of the woodpeckers; it identifies
them unmistakably in the air. Note the rapid beating of the
wings of quail and grouse; also of wild ducks; the slow, heavy,
flapping of the larger hawks and owls, and of the crows; and
the splendid soaring of the turkey-buzzard and of the gulls.
This soaring has been the subject of much observation and
study, but is still imperfectly understood. The soaring bird
evidently takes advantage of horizontal air-currents, and some
observers maintain that upward currents also must be present.
The speed of flight of some birds is enormous, the passenger-
pigeon having been estimated to attain a speed of one hundred
miles an hour. The long distances covered in a single continu-
ous flight by certain birds are also extraordinary, as is also the
total distance covered by some of the migrants. The differ-
ences in the structural character of the wings should be noted
in connection with the observation of the differences in flight
habit. The tongue and tail of birds are two other structures
the modifications and special uses of which may be readily
observed and studied. Note the structure and special use
of the tongue and tail of the woodpeckers; note the tongue
of the humming-bird; the tail of the grackles.

Feeding Habits, Economics, and Protection of Birds. — The
feeding habits of birds have been already repeatedly referred
to. The study of these habits is not only interesting but is,
of course, of much importance in that it is the character of
these habits that determines the economic relation of birds to
man, that is, whether a particular bird species is harmful or
beneficial. Casual observation shows that birds eat worms,
grains, seeds, fruits, insects. A single species often is both
fruit-eating and insect-eating. Do fruits or do insects compose
the chief food- supply of the species? To determine this more
than casual observation is necessary. The birds must be
watched when feeding at different seasons. The most effec-
tive determinations of the kind of food taken by various
birds has been based on examinations of the stomach of many
individuals taken at various times and localities. Much
work of this kind has been done, especially by investigators

BIRDS 293

connected with the Bureau of Biological Survey of the United
States Department of Agriculture, and pamphlets giving the
results of these investigations can be had from the Superin-
tendent of Public Documents, Washington, D. C. The food
habits of over 400 species of native birds and of several intro-
duced kinds are referred to in these publications. Full reports
based on stomach investigations have been made on the food of
173 native species. As a result of all this work it has been
clearly shown that a great majority of birds are chiefly beneficial
to man by eating noxious insects and seeds of weeds. Most
birds commonly reputed to be harmful, and for that reason
shot by farmers and fruit-growers, have been proved to do
much more good than harm. An investigation of the food
habits of the crow, a bird of ill-repute among farmers, based
on an examination of 909 stomachs, show that about 29 per
cent, of the food of the year consists of grain, of which corn
constitutes something more than 21 per cent., the greatest
quantity being eaten in the three winter months. All of this
must be either waste grain picked up in fields and roads, or
corn stolen from cribs and shocks. May, the month of
sprouting corn, shows a slight increase over the other spring
and summer months. On the other hand, the loss of grain
is off-set by the destruction of insects. These constitute more
than 23 per cent, of the crow's yearly diet, and the larger
part of them are noxious. The remainder of the crow's food
consists of wild fruit, seeds, and various animal substances
which may on the whole be considered neutral. However,
some few birds have been proved to be, on the whole,
harmful.

The slaughter of birds for millinery purposes has become so
fearful and apparent in recent years that a strong movement
for their protection has been inaugurated. Rapacious egg-
collecting, legislation against birds wrongly thought to be
harmful to grains and fruits, and the selfish wholesale killing
of birds by professional and amateur hunters, help in the work
of destruction. Apart from the brutality of such slaughter,
and the extermination of the most beautiful and enjoyable
of our animal companions, this destruction works strongly

294 ECONOMIC ZOOLOGY AND ENTOMOLOGY

against our material interests. Birds are the natural enemies
of insect pests, and the destroying of the birds means the rapid
increase and spread, and the enhanced destructive power of
the pests. It is asserted by investigators that during the past
fifteen years the number of our common song-birds has been
reduced by one-fourth. At the present rate, says one author,
extermination of many species will occur during the lives of
most of us. Already the passenger-pigeon and Carolina paro-
quet, only a few years ago abundant, are practically exter-
minated. In Japan and Italy there are hardly any song-birds
left so ruthless has been their destruction. We do not want
to come to that condition. Protect the birds!

CHAPTER XXV
MAMMALS

Although by no means the largest numerically, the class of
mammals, Mammalia, is by far the most important group of
animals. Not only does it include man himself but practically
all of the domestic animals besides scores of others that add to
his welfare by furnishing him food or clothing. The name
Mammalia refers to the mammary glands of the female which
furnish milk for the nourishment of the young for some time
after its birth.

In size, the mammals range from the tiny pigmy-shrew of
fields and meadows to the great wrhales which attain a
length of eighty to a hundred feet and a weight of many tons.
In structure and habits there is also a remarkable range of
variation. Most mammals live on land and their legs are
usually well fitted for walking, running or jumping, but some
live in trees and have their appendages adapted for holding
on to the branches or for taking considerable leaps through the
air. Others, like the burrowing gophers and moles, live in the
earth and have the forelegs fitted for digging. The water-
inhabiting forms often have their appendages modified into
fins or flippers and in other ways show remarkable adaptations
fitting them for their aquatic life.

Body -form and Structure. — Most mammals are clothed
with hairs, which are peculiarly modified epidermal proc-
esses. Each hair, usually cylindrical, is composed of two
parts, a central pith containing air, and an outer more solid
cortex; each hair rises from a short papilla sunk at the bottom
of a follicle lying in the true skin. In some mammals the hairs
assume the form of spines, or "quills," as in the porcupine.
The hairy coat is virtually wanting in whales and is very
sparse in certain other forms, the elephant, for example,

295

296 ECONOMIC ZOOLOGY AND ENTOMOLOGY

which has its skin greatly thickened. The claws of beasts of
prey, the hoofs of hoofed mammals, and the outer horny
sheaths of the hollow-horned ruminants are all epidermal
structures.

The bones of mammals are firmer than those of other ver-
tebrates, containing a larger proportion of salts of lime.
Among the different forms the spinal column varies largely in
the number of vertebras, this variation being chiefly due to
differences in length of tail. Apart from the caudal vertebrae
their usual number is about thirty. The mammalian skull
is very firm and rigid, all the bones composing it, excepting
the lower jaw, the tiny auditory ossicles, and the slender
bones of the hyoid arch, being immovably articulated. The
correspondence between the bones of the two sets of limbs is
very apparent. The number of digits varies in different mam-
mals, and also in the fore and hind limbs of a single species.
Among the Ungulates, or hoofed animals, the reduction in the
number of digits is especially noticeable; the forefoot of a pig
has four digits, that of the cow two, and that of the horse one.
The two short "splint" bones in the horse are remnants of
lost digits. The teeth are important structures in mammals,
being used not only for tearing and masticating food, but as
weapons of offense and defense. A tooth consists of an inner
soft pulp (in old teeth the pulp may become converted into
bone-like material) surrounded by hard white dentine, or ivory,
which is covered by a thin layer of enamel, the hardest tissue
known in the animal body. A hard cement sometimes covers
as a thin layer the outer surface of the root, and may also
cover the enamel of the crown. The teeth in most forms are
of three groups : (a) the incisors, with sharp cutting edges and
simple roots, situated in the center of the jaw; (b) the canines,
often conical and sharp-pointed, next to the incisors; (c)
next the molars, broad and flat-topped for grinding, and
divided into premolars and true molars. There is great variety
in the character and arrangement of the teeth in mam-
mals, their variations being much used in classification.

The mouth is bounded by fleshy lips. On the floor of the
mouth is the tongue, which bears the taste-buds or papillae,

MAMMALS 297

the organs of taste. The esophagus is always a simple straight
tube, but the stomach varies greatly, being usually simple, but
sometimes, as in the ruminants and whales, divided into
several distinct chambers. The intestine in vegetarian animals
is very long, being in a cow twenty times the length of the
body. In the carnivores it is comparatively short — in a tiger,
for example, but two or three times the length of the body.

The blood of mammals is warm, having a temperature of
from 35° C. to 40° C. (95° F. to 104° F.). It is red in color,
owing to the reddish-yellow, circular, non-nucleated blood-
corpuscles. The circulation is double, the heart being com-
posed of two distinct auricles and two distinct ventricles.
Air is taken in through the nostrils or mouth and carried
through the windpipe (trachea) and a pair of bronchi to the
lungs, where it gives up its oxygen to the blood, from which it
takes up carbon dioxide in turn. At the upper end of the
trachea is the larynx, or voice-box, consisting of several car-
tilages attaching by one end to the vocal cords and by the
other to the muscles. By the alteration of the relative position
of these cartilages the cords can be tightened or relaxed, brought
together or moved apart, as required, to modulate the tone
and volume of the voice.

The kidneys of mammals are more compact and definite in
form than those of other vertebrates. In all mammals except
the Monotremes (duckbills, etc.), they discharge their product
through the paired ureters into a bladder, whence the urine
passes from the body by a single median urethra. Mammary
glands, secreting the milk by which the young are nourished
during the first period of their existence after birth, are present
in both sexes in all mammals, though usually functional in the
female only.

The nervous system and the organs of special sense reach
their highest development in the mammals. In them the
brain is distinguished by its large size, and by the special pre-
ponderance of the forebrain, or cerebral hemispheres, over the
mid- and hind-brain. Man's brain is many times larger than
that of any other known mammal of equal bulk of body, and
three times as large as that of the largest-brained ape. In

298 ECONOMIC ZOOLOGY AND ENTOMOLOGY

man and the higher mammals the surface of the forebrain is
thrown into many convolutions; among the lowest the surface
is smooth. Of the organs of special sense, those of touch con-
sist of free nerve-endings or minute tactile corpuscles in the
skin. The tactile sense is especially acute in certain regions,
as the lips and end of the snout in animals like hogs, the fingers
in man, and the under surface of the tail in certain monkeys.
All the other sense-organs are situated on the head. The or-
gans of taste are certain so-called taste-buds located in the
mucous membrane covering certain papillae on the surface of
the tongue. The organ of smell, absent only in certain whales,
consists of a ramification of the olfactory nerves over a moist
mucous membrane in the nose. The ears of mammals are
more highly developed than those of other vertebrates both in
respect to the greater complexity of the inner part and the
size of the outer part. A large outer ear for collecting the
sound-waves is present in all but a few mammals. A tympanic
membrane separates it from the middle ear in which is a chain
of three tiny bones leading from the tympanum to the inner
ear, which is composed of the three semi-circular canals and
the spiral cochlea. The eyes have the structure characteristic
of the vertebrate eye, consisting of a movable eyeball com-
posed of parts through which the rays of light are admitted,
regulated, and concentrated upon the sensitive expansion,
called retina, of the optic nerve lining the posterior part of
the ball. The eye is protected by two movable lids. In
almost all mammals below the Primates (man and the
monkeys) there is a third lid, the nictitating membrane. In
some burrowing rodents and others the eye is quite vestigial
and even concealed beneath the skin.

The mental qualities of animals reach their highest develop-
ment among the mammals. In the wary and patient hunting
for prey by the carnivora, the gregarious and altruistic habits
of the herding hoofed mammals,, the highly developed and
affectionate care of the young shown by most mammals, and
in the loyal friendship and self-sacrifice of dogs and horses
in their relations to man, we see the culmination among animals
of the development of the functions of the nervous system.

MAMMALS 299

In the characteristics of intelligence and reason, man, of course,
stands immensely superior to all other animals, but both intelli-
gence and reason are too often shown by many of the other
mammals not to make us aware that man's mental powers
differ only in degree, not in kind, from those of other animals.

Development and Life History. — All animals except the
Monotremes give birth to free young. The Monotremes
produce their young from eggs hatched outside the body.
The embryo of other mammals develops in the lower portion
of the egg-tube, to the walls of which it is intimately connected
by a membrane called the placenta. (In the kangaroos and
opossums, Marsupialia, there is no placenta.) Through this
placenta blood-vessels extend from the body of the mother and
from the embryo, and a close connection between the vascular
systems of the parent and the embryo thus becomes established.
In this way the developing young derives its nourishment from
its mother.

The duration of gestation (embryonic or prenatal develop-
ment in the mother's body) varies from three weeks with the
mouse, eight weeks with the cat, nine months with the cow,
to twenty months with the elephant. Like the birds, the young
of some mammals, the carnivores, for example, are helpless at
birth, while those of others, as the hoofed animals, are very
soon able to run about. But all are nourished for a longer or
shorter time by the milk secreted by the mammary glands of
the mother.

Classification.1 — The mammals are usually divided into
eleven orders, eight of which occur in North America. The
small order Monotremata includes but three species of primitive
mammals, each representing a separate genus. They are
found in Australia, Tasmania and New Guinea. Their most
unusual and primitive characteristic is that of laying eggs.
After hatching from the eggs the young are nourished on milk
which does not issue from teats, but is poured out over the

1 The classification adopted here is that used by Hornaday in his
American Natural History. While later authorities have changed many
of the scientific names, especially those of genera, the ones here used are
the most familiar and hence the most useful.

300 ECONOMIC ZOOLOGY AND ENTOMOLOGY

hair of the abdomen and licked off by the young. The duck-
bill or platypus, genus Ornithorhynchus, is about sixteen inches
long, has webbed feet, close water-proof fur, and a flattened
duck-like bill. It lives mostly in water, with an underground
chamber leading from the water, in which the eggs are laid and
the young reared. The spiny ant-eater, genus Echidna, lives
in burrows, and feeds, by means of a long snout bearing the
toothless mouth and extensile tongue, on ants. Its eggs are
carried in a skin pouch on the abdomen.

The order Marsupialia includes the kangaroos, opossums,
and others. These differ from all other mammals in that the
female has an external pouch, or marsupium, in which the young
are placed after birth and carried about and nourished until
they are more fully developed. As these animals have no
placenta, by means of which the young may be nourished by
the blood of the mother, they are born in a very helpless
condition and so must be cared for in the marsupium for some
months. In Australia most of the land animals are marsupials.
The kangaroos are the most familiar examples. They were
formerly quite abundant, but have been hunted for their skins
to make leather for shoes until their numbers have been much
reduced. The opossum, Didelphys virginiana, which is the
only North American representative of the order, lives in trees,
is about the size of a common cat, and has a dirty-yellowish
woolly fur. Its tail is long and scaly, like a rat's. Its food
consists chiefly of insects, although small reptiles, birds, and
bird's eggs are often eaten. When ready to bear young the
opossum makes a nest of dried grass in the hollow of a tree,
and produces about thirteen very small (half an inch long)
helpless creatures. These are then placed by the mother in
her pouch. Here they remain until two months or more after
birth. Probably all the North American opossums found from
New York to California and especially common in the Southern
States, belong to a single species, but there is much variety
among the individuals. They are commonly used for food
and are sometimes seen on the market.

The order Edentata includes the sloths, armadillos and ant-
eaters, all found in tropical regions. The sloths dwell in the

MAMMALS 301

tree tops feeding on green leaves. They are not entirely tooth-
less as the name of the order would indicate, but they are
nearly so. "One cannot look at a live sloth without thinking
that nature has but poorly equipped this animal to live in this
murderous world. Its countenance is a picture of complete and
far-reaching stupidity, its bodily form the acme of four-footed
helplessness. It can neither fight, hide, nor run away. It has
no defensive armor, not even spines. It is too large to live in a
hole in a tree, and too weak to dig a burrow in the earth. It
is too tired to walk on its feet, as the monkeys do, so through-
out its queer life it hangs underneath the branches of the trees
in which it finds its food." (Hornaday.)

The armadillos occur principally in South America, but one
species, the nine-banded armadillo, Tatu novemcinctum, is
found also in Mexico, Texas and Arizona. They are covered
with hard bony plates which form a protecting case for all
parts of the body. When attacked the animal draws in its
legs and rolls up into a ball leaving exposed to its enemy only
this bony shell.

The ant-eaters are also confined to South and Central
America. The small mouth situated at the end of a long
slender beak is entirely toothless. They devour great quan-
tities of ants and thus help to reduce the numbers of these
insects which are often great pests in tropical countries.

To the order Sirenia belong the manatees, or sea-cows, and
the dugongs. These are aquatic, seal-like animals with the
fore legs reduced to a pair of flippers and the hind legs wanting.
One species of manatee, Trichechus latirostris, is still found off
Florida, and others occur in the warm waters of the islands and
along the coast of Mexico, Central and South America. The
great Arctic sea-cow, Hydrodamalis gigas, once occurred
abundantly in the Bering Sea region where it reached a length
of twenty to thirty feet. The natives and the whalers used
it for food until it was practically exterminated about 1780.
The last animal of this species seen was killed in 1854.

The Cete are an order of aquatic mammals all more or less
fish-like. The whales, dolphins and porpoises belong to this
order. In all, the posterior limbs are so reduced that they

302 ECONOMIC ZOOLOGY AND ENTOMOLOGY

do not appear at all externally, while the forelimbs are devel-
oped as broad flattened paddles without distinct fingers or nails.
The tail ends in a broad horizontal fin or paddle. The Cete
are all predaceous, fish, pelagic crustaceans, and especially
squids and cuttle-fishes forming their principal food. Most
of the species are gregarious, the individuals swimming together
in "schools." Some of them can remain under water for a
long while but they must all come to the surface to breathe.
As the whales come to the surface they blow the air from their
lungs out through the blow holes on top of their head. This
air is so heavily laden with moisture that it is usually supposed
and said that the whale is actually "spouting" water.

The whales comprise two families, the sperm whales, Physe-
terida, with numerous teeth in their lower jaw, and the whale-
bone whales, Balanidce, which have in the mouth, instead of
teeth, many long parallel plates with fringed edges, the valuable
"whalebone" of commerce. The great sperm whales reach a
length of eighty feet of which the head forms nearly one-third.
They feed on various kinds of fish and squid. They are hunted
for the sperm oil, which is obtained from the "blubber or layer of
fat that lies under the skin, and for the spermaceti which is
obtained from the head and is used in making candles and
ointments. The teeth of these whales are also of considerable
value, being used for ivory. Of the whalebone whales, the
sulphur-bottom whale of the Pacific Ocean, reaching a length
of nearly one hundred feet, is the largest, and hence the largest
of all living animals. These great monsters feed on minute
shrimp-like crustaceans and other small organisms swimming
at or near the surface of the sea. The whale swims along
with its mouth wide open, the mass of "whalebone" plates
acting as a strainer until a mouthful of dainty food is procured.
The sulphur-bottom whale, the right whale, the hump-back
whale, the bow-head whale and others are all hunted for the
"whalebone," or baleen, and for the oil. The bow-head or
polar whale is the most important commercially, a single speci-
men sometimes yielding 3500 pounds of whalebone and 275
barrels of oil.

The family Delphinidce includes the dolphins and porpoises

MAMMALS 303

and certain others some of which yield valuable oil. It also
includes the vicious killer "whale," or orca, which "has the
appetite of a hog, the cruelty of a wolf, the courage of a bulldog,
and the most terrible jaws afloat." Although they are not
more than fifteen to twenty feet long three or four of them
will attack and destroy even the largest whale.

The hoofed mammals, order Ungulata, include some of the
most familiar mammal forms. Most of the domestic animals,
as the horse, cow, hog, sheep and goat, belong to this order, as
well as the familiar deer, antelope, and buffalo of our own land,
and elephant, rhinoceros, hippopotamus, giraffe, camel, zebra,
etc., familiar in zoological gardens and menageries. The order
is a large one, its members being characterized by the presence
of from one to four hoofs, which are the enlarged and thick-
ened claws of the toes. The Ungulates are all herbivorous,
and have their molar teeth fitted for grinding, the canines being
absent or small. The order is divided into the Perissodactyla,
or odd-toed forms, like the horse, zebra, tapir, and rhinoceros,
the Artiodactyla, or even- toed forms, like the oxen, sheep, deer,
camels, pigs and hippopotami, and the Proboscidia, the ele-
phants. The Artiodactyls comprise two groups, the Ruminants
and Non-ruminants. All the native Ungulata of our Northern
States belong to the Ruminants, so-called because of their habit
of chewing a cud. A ruminant first presses its food into a ball,
swallows it into a particular one of the divisions of its four-
chambered stomach, and later regurgitates it into the mouth,
thoroughly masticates it, and swallows it again, but into
another stomach-chamber. From this it passes through the
other two chambers into the intestine.

The deer family, Cervida, comprises the familiar Virginia, or
red, deer of the Eastern and Central States and the white-
tailed, black-tailed, and mule deers of the West, all belonging
to the genus Odocoileus, the great antlered elk or wapiti,
Cervus canadensis, the great moose, Alee americana, largest of
the deer family, and the American reindeer or caribou, Rang-
ifer caribou. All species of the Cervidae have solid horns, more
or less branched, which are shed annually. Only the males
(except with the reindeer) have horns. The antelope, Antilo-

3o4 ECONOMIC ZOOLOGY AND ENTOMOLOGY

capra americana, common on the Western plains, also sheds its
horns, which, however, are not solid and do not break off at the
base as in the deer, but are composed of an inner bony core
and an outer horny sheath, the outer sheath only being shed.
The family Bovidce includes the once-abundant buffalo, or bison,
Bison bison, the big-horn, or Rocky Mountain sheep, Oms
canadensis, and the strange pure white Rocky Mountain goat,
Oreamnos montanus. The buffalo was once abundant on the

FIG. 132. — Buffalo, Bison bison, in Golden Gate Park, San Francisco, Cal.

Western plains, travelling in enormous herds. But so relent-
lessly has this fine animal been hunted for its skin and flesh that
it is now practically exterminated. A small herd is still to be
found in Yellowstone Park, another in Canada, and other pro-
tected groups live in parks and zoological gardens. On Jan. i,
1913, a total of 3,453 bison were alive in North America. In
all of the Bovidce the horns are simple, hollow, and permanent,
each enclosing a bony core.

Many of these native, wild hoofed animals have been impor-

MAMMALS

305

tant as a source of food, but nearly all are now so reduced in
numbers that they are little hunted except for sport. The
domesticated mammals, the most important of which belong
to this order, are discussed in Chapter XXVI.

The order Glires, the rodents, or gnawers, is the largest of the
orders of mammals, and includes the rabbits, porcupines,

FIG. 133. — A buffalo, Bison bison, killed for its skin and tongue, on the
plains of western Kansas, forty years ago. (Photograph by J. L. Knight.)

gophers, chipmunks, beavers, squirrels, rats and mice. The
special arrangement and character of the teeth are character-
istic of this order. There are no canines, a toothless space
being left between the incisors and molars on each side. There
are only two incisor teeth in each jaw (rarely four in the upper
jaw). These teeth grow continuously and are kept sharp
and of uniform length by the gnawing on hard substances and

3o6 ECONOMIC ZOOLOGY AND ENTOMOLOGY

the constant rubbing on each other. The food of rodents is
chiefly vegetable.

The order is divided into several families of which the fol-
lowing are the most common: the Leporida, the rabbits and
hares; the Erethizontida, the porcupines; the Geomyida, the

FIG. 134. — Chipmunk. (Permission of Camera Craft.)

pocket gophers; the Zapodidce, the jumping mice; the Dipodida,
the pocket mice and kangaroo rats; the Murida, the mice and
rats; the Castorida, the beavers; and the Sciurida, the squir-
rels, woodchucks and prairie-dogs.

Of the hares and rabbits, the cottontail, Lepus sylvaticus, and

MAMMALS 307

the common jack-rabbit, L. texanus, are the best known.
The cottontail is found all over the United States, but shows
some variation in the different regions. There are several
species of jack-rabbits, all limited to the plains and mountain
regions west of the Mississippi river. The food of rabbits is
strictly vegetable, consisting of succulent roots, branches, or
leaves.

As long as they confine their feeding to wild plants, or even
to cultivated field crops, the damage that they do is usually
not great, although when very abundant they may materially
injure wheat or alfalfa fields. In the gardens, however, where
they will attack all kinds of vegetables, they sometimes cause
considerable annoyance, or even serious loss. Tree and shrubs
are often injured, especially in the winter time when the ground
is covered with snow and there is little other green food to be
had. The rabbits eat the ends of the branches within their
reach or gnaw the bark, sometimes girdling the tree. The most
satisfactory remedy, where the rabbits are abundant enough to
be a nuisance, is to allow hunters to kill them. Most rabbits
are of fine flavor, especially when young. The cotton-tails are
usually considered superior even to Belgian hares and other
domesticated species. In some regions where the country is
sufficiently open "rabbit drives" are organized, and as many
as 10,000 to 20,000 rabbits are killed in a single drive.
Various kinds of traps are used in the orchards and gardens,
and poisoning is sometimes resorted to, but the latter is always
dangerous. Rabbit-proof fences are effective and although
expensive are often profitable. Trees may be protected with
close meshed wire or by veneer, cornstalks, sacking or other
substances. Most of thepaints or smears usually recommended
to be put on the trees are apt to injure them. The sulphur-
lime mixture, such as is used for scale insects (see page 415)
has proved a very effective repellent wash in many places.

Nearly fifty years ago the common rabbit of Europe was
introduced into Australia as a game animal. In the absence
of their natural enemies the rabbits multiplied so rapidly that
they soon became serious pests and have cost the country
millions of dollars, $3,500,000 being the estimated annual loss.

3o8 ECONOMIC ZOOLOGY AND ENTOMOLOGY

The skins are shipped in great quantities to Europe, where the
fur is used in making many articles such as boas, muffs, hats
and trimmings. The fur of the American rabbits is but little
used except by the Indians.

There are two North American species of porcupines, an
Eastern one, Erethizon dorsatus, and a Western one, E. epixan-
thus. The quills in both these species are short, being only an
inch or two in length, and are barbed. In some foreign porcu-
pines they are a foot long. They are loosely attached in the
skin and may be readily pulled out, but they cannot, be shot
out by the porcupine, as is popularly told. The little guinea-
pigs, Cavia, kept as pets, are South American animals related
to the porcupines. Because of the ease with which they can
be reared and handled, and for certain technical reasons, guinea-
pigs are much used in physiological and bacteriological labora-
tories for experimental purposes. The sacrifice in this way of a
few thousand guinea-pigs has aided in enormously increasing our
knowledge of the causes of and remedies for infectious disease.

The pocket-gophers, of which there are several genera and
species mostly inhabiting the central plains, are rodents found
only in North America. They all live underground, making
extensive galleries. They are very destructive to such crops as
alfalfa, clover, grains, potatoes, and to many others, and often
cause the loss of thousands of dollars in orchards by destroying
the roots or girdling the trees and thus quickly killing them.
Gophers may be poisoned or trapped. Small bits of carrots,
potatoes, raisins, prunes or other substances may be poisoned
by placing a small amount of strychnine in them; an amount
equal to about half a grain of wheat is sufficient. The poisoned
baits should be placed in the main tunnel, not in the short
lateral tunnels that are used for bringing the dirt to the surface.
If placed in the lateral tunnels they may be covered over or
pushed to the surface where other animals or birds may find
them. Many special forms of traps are used, almost all of
them good if sufficient care is taken in setting them. When
the ground is not too dry success may often attend the use of
carbon bisulphide. Rags or waste may be saturated with this
liquid and placed in the hole which is then closed tightly, or

MAMMALS 309

the gas may be introduced by means of a small hand pump
constructed for this purpose.

The mice and rats constitute a large family of which the
house mice and rats, the various field mice, the wood-rat,
Neotoma pennsylvanica, and the muskrat, Fiber zibethicus, are
familiar representatives. The common brown rat, Mus decu-
manus, was introduced into this country from Europe about
1775, and has now nearly wholly supplanted the black rat, M.
ralttis, also a European species, introduced about 1544. Rats
are by far the worst of all the mammalian pests. The damage
that they do to foods and stored products the world over
amounts to hundreds of millions of dollars annually and, what
is far worse, they may carry, as we shall learn (page 375), the
germs of the dreaded bubonic plague and are thus a constant
menace. The fight against them has been carried on for ages
and still they continue to multiply and spread. Poison and
traps are more or less successful, the degree of success depend-
ing, in a large measure, on the skill of the one who is doing the
poisoning or the trapping and to a still greater extent on the
age or experience of the rats, the old, experienced fellows be-
coming very cunning. The modern methods of fighting the
rat are to cut off its food supply and to destroy, as far as possi-
ble, its breeding places. A liberal supply of food means many
litters of rats and many young in a litter. Scarcity of food will
reduce both, so if garbage cans are kept closed and feed bins
and cellars and store houses made rat proof, the rats will
either die or seek a more hospitable place. The great fight
carried on against the rats in San Francisco when this city
successfully fought the plague some years ago, shows what
can be done by united effort directed along these lines. In
that fight fully 1,000,000 rats were slain, 8,000,000 square
feet of concrete were used in rat-proofing, more than 100,000
new, covered garbage cans were installed, and all rubbish was
cleaned up in all parts of the city. It was the rat fighting
that stayed the disease.

The muskrat, Fiber spp., is one of our largest rats, reaching a
length of twenty-one inches. It lives in the water, and makes
houses there much as do beavers, and is hunted for its fur.

3io ECONOMIC ZOOLOGY AND ENTOMOLOGY

Mice, as a rule, are less serious pests than rats, but the total
damage that the common house mouse, M us musculus, does
about dwellings and storehouses is very great. This species
is a native of India, but has become thoroughly cosmopolitan.
Some of the field mice, Microtus sp., frequently do considerable
damage in fields of alfalfa or grain and in nurseries and orchards.
It is estimated that the damage that they do in the United
States amounts to more than $3,000,000 annually. Rarely
they occur in great numbers and thus become a veritable
plague, devastating large areas. In such outbreaks they are
best controlled by placing alfalfa or grain poisoned by arsenic
in or at the entrance of their burrows. These plagues rarely
last more than a season, as natural enemies and diseases soon
reduce the mice to normal numbers.

The beaver, Castor canadensis, is the largest rodent, weigh-
ing sometimes as much as fifty pounds. With their sharp
chisel-like teeth beavers cut down small trees in order that they
may get at the bark which they use for food. They often
build dams of considerable size in order to make a deep pond
in which to live and work. The dam is made of trees which
have fallen into the stream and sticks of wood of all sizes with
the interstices filled with mud. The beavers burrow into the
banks or build houses which extend above the surface of the
water. The entrance to the burrow is always below the surface.
Beavers are much hunted for their fur, which is very valuable.
They are so nearly exterminated that they are now found only
in a few localities.

The woodchucks, or ground-hogs, Marmolla spp., are other
familiar rodents larger than most members of the order. The
chip-munks and ground-squirrels, of which there are several gen-
era, are commonly known rodents found all over the country.
They are the terrestrial members of the squirrel family, the
best known arboreal members of which are the red squirrel,
Sciurus hudsonicus, the fox-squirrels, S. ludovicianus and S.
niger, and the gray or black squirrel, S. carolinensis. The
little flying squirrel, Sciuropterus volans, is abundant in the
eastern states.

The ground-squirrels, commonly known as spermophiles

MAMMALS 311

because they are so fond of seeds, are very serious pests of
grain growers in many regions. The remedies for them are the
same as for gophers, that is, carbon bisulphide put into the holes
when the ground is moist, or poisoned grain put at the entrance
to the burrows. One of the western members of the group
has been found to be affected at times with the plague bacillus,
and instances are recorded where human beings have become
infected with this disease after being bitten by fleas from
plague-infected ground-squirrels. Some of the ground-squir-
rels compensate in a measure for the damage that they do,
by eating many destructive insects such as grasshoppers,
cut-worms, beetles, etc., often, too, killing mice and other
small noxious animals. The thirteen-lined spermophile,
Citellus tridecemilineatus , is common over the Mississippi
valley, and other large members of the same genus occur
throughout the West. The prairie-dogs, Cynomys ludovicianus,
are closely related to the ground-squirrels, and are found in
great "towns" over the western plains. Lands so infested
are unfit for cultivation and may even be ruined for pasture.
Wheat or other grain poisoned with strychnine placed at the
entrance to their burrows in the winter or early spring will
kill most of them. Carbon bisulphide, as recommended for
gophers and squirrels, is very effective.

The shrews and moles belong to the order Insectivora, They
are all small carnivorous animals, which, because of their size,
confine their attacks chiefly to insects. The shrews are small
and mouse-like; certain kinds of them lead a semi-aquatic life.
There are nearly a score of species in North America. Of the
moles, of which there are but few species, the common mole,
Scalops aquaticus, is well known, while the star-nosed mole,
Condylura cristata, is recognizable by the peculiar rosette of
about twenty cartilaginous rays at the tip of its snout. Moles
live underground, and have the fore feet wide and shovel-like
for digging. As they destroy great numbers of cutworms, grubs
and other injurious insect larvae and do not eat vegetable food
they must be regarded as very beneficial. But their burrows
are sometimes so destructive in the lawns and flower beds that

3i2 ECONOMIC ZOOLOGY AND ENTOMOLOGY

the damage they do more than counterbalances the good. In
the fields and garden, however, they should be protected.

The bats, order Chiroptera, differ from all other mammals in
having the fore limbs modified for flight by the elongation of
the forearms and especially of four of the fingers, all of which
are connected by a thin leathery membrane which includes also
the hind feet and usually the tail. Bats are chiefly nocturnal,
hanging head downward by their hind claws in caves, hollow
trees, or dark rooms through the day. They feed chiefly on
insects, although some foreign kinds live on fruits. There
are a dozen or more species of bats in North America, the most
abundant kinds in the Eastern States being the little brown
bat, Myotis subulatus, about three inches long with small
fox-like face, high slender ears, and a uniform dull olive-brown
color, and the red bat, Lasiurus borealis, nearly four inches long,
covered with long, silky, reddish-brown fur, mostly white at
tips of the hairs. Most of the bats are beneficial as they cap-
ture and destroy many insects, but a few exotic kinds feed on
fruit, and the large vampire bats suck the blood of other
animals.

The order Ferce include all those animals usually called the
carnivora, such as the lions, tigers, cats, wolves, dogs, bears,
panthers, foxes, weasels, seals, etc. All of them feed chiefly on
animal substance and are predatory, pursuing and killing their
prey. They are mostly fur covered and many are hunted for
their skin. They have never less than four toes, which are
provided with strong claws that are frequently more or less
retractile. The canine teeth are usually large, curved, and
pointed.

The FelidcB, or cat family, includes the lions, tigers, hyenas,
leopards, jaguars, panthers, wild cats, lynxes, and the common
domestic cat. The largest of them, the lions, occur in Central
Africa preying on any other animals that they can capture.
Inferior to lions in size but superior in strength are the Bengal
tigers that occur throughout the jungles of southern Asia.
Other smaller tigers occur in other parts of the Old World.
They often prey upon domestic animals and sometimes will
even attack man if enraged or driven by hunger. Indeed, there

MAMMALS 313

is a notable annual loss of life among the natives of India from
the attacks of "man-eating" tigers.

The jaguar, Fdis onca, which occurs as far north as the
southern part of the United States, is the largest and most
beautiful of the American members of this family. The puma,
or mountain lion, or cougar, Fells concolor, occurs throughout
the western mountains and foothills. It preys upon deer,
mountain sheep and other wild animals, and sometimes upon
domestic animals. Like all members of the family it will
avoid man if possible, but in defense of self or of young and
sometimes when driven by hunger, the pumas will attack man
savagely. Large specimens measure five feet in length from
nose to base of tail.

The Canada lynx, Lynx canadensls, and the bay lynx, wrhich
is also known as the red lynx, or wild cat, or bob cat, Lynx rufus,
still occurs in considerable numbers in many parts of the coun-
try, often raiding the poultry yards. The ocelots, Fells parda-
lis, beautifully marked by spots and broken bands running
lengthwise of the body, occur only as far north as Texas.

The Canida, or dog family, includes the wolves, coyotes,
foxes, and the domestic dogs. The gray or timber wolf, Cams
occidentalis, is the largest and most formidable of them. These
wolves range through the north and west where they often
hunt in packs and are able to overpower animals much larger
than themselves. They were formerly very troublesome on
stock ranches, killing many young calves and colts. The coyote,
or prairie wolf, Canis latrans, is only about two-thirds as large
as the gray wolf. It feeds on small animals and birds, and
often visits the ranchers' poultry yards. But as coyotes often
kill prairie-dogs and ground-squirrels they make recompense in
some measure for the damage that they do. They are usually
crafty enough to avoid all traps and to keep out of range of guns.
Wolves and coyotes are sometimes destroyed by placing a two
to four grain capsule filled with strychnine in small pieces of
beef or suet. The meat should not be touched by the hands,
and should be dropped from horseback along trails used by
the wolves.

There are many species of foxes in America, the red fox,

3i4 ECONOMIC ZOOLOGY AND ENTOMOLOGY

Vulpes fulvus, being perhaps the most widely distributed and
generally known. The black fox, or the silver gray fox, is a
variety of the red fox that is wholly black except the tip of the
tail, which is white. These are the most valuable for fur,
single skins selling at from $500 to $1000, and extra fine ones
sometimes bringing $2000 to $2500. The Arctic fox, Vulpes
lagopus, is white all the year around in its northern range, but
further south it is darker and is known as the blue fox. The
white skins are worth $10 to $12, the blue skins two to four
times as much. In Alaska successful attempts have been made
to rear these foxes in captivity. Less success has so far re-
warded the efforts to breed the black or silver fox, as it is much
more shy and must have game for its food, refusing to take the
food prepared for it as does the blue fox. Doubtless, however,
further experiments will show how it may be handled and
bred successfully in large restricted areas.

The family Mustelidce includes several of our most valuable
fur-bearing animals, many of which are, however, now nearly
exterminated. The otter, mink, ferret, weasel and martin all
have long slender bodies and very short legs. The otter, Lutra
canadensis, used to be common along many of our streams but
is now rarely found except in the far north. The fur of the sea
otter, Latax Ittlris, is now most valuable and rare. Specimens
are still taken occasionally along the Alaska coast. Minks,
Lutreola spp., are still rather common, occurring along the
banks of many of our streams. There are several species of
weasels, the most common one of which, Putorius erminea, is
often called the ermine. It is brown in summer and white in
winter. Weasels are often serious pests of the poultry yards,
for they usually kill many more chickens or ducks or geese
than they can eat. They do some good on the farm by catch-
ing rats and field mice.

The wolverine, or skunk-bear, Gulo luscus, looks not unlike a
large skunk or a badger except that it is without stripes.
It occurs throughout the west and north, and is often
called glutton, on account of its habit of eating almost any-
thing it can find and seemingly maliciously destroying much
else. The skunks, Mephitis spp., and Spilogale spp., are well

MAMMALS 315

known in all communities. The ill-smelling fluid which causes
other animals, including man, to keep a respectful distance when
possible, is secreted by two glands near the base of the tail.
The skunks are very destructive in poultry yards, but since
their skins are now much used as substitutes for otter, mink and
sable, they will probably soon be much less common than at
present. The badgers, Taxidea, are broad, flat, short-legged
animals living in burrows throughout the west, and feeding on
ground-squirrels and any other small animals that they can
capture.

The raccoons, or " coons, " family Procyonida, are found in
wooded regions throughout America. They usually live in
hollow trees, and eat almost all kinds of food. They sometimes
give poultry raisers a good deal of trouble, but are usually
easily trapped or hunted and killed.

The bears belong to the family Ursula, and all, except the
polar bear, to the genus Ursus. They feed on almost any kind
of meat or fish that they can obtain, and on roots, berries,
honey a'nd many other things. Unless fighting in defense of
self or young they will seldom molest man, but some of the
larger species make occasional destructive raids on stock
ranches where they may kill sheep or hogs or young cattle. The
polar bear, Thalarctos maritimus, is found throughout the Arctic
regions and is one of the largest of our bears. The fur is white
all the year around. The black bears, U. americanus, are the
most common and widely distributed. They vary greatly in
color and size, and are sometimes called brown bears or cinna-
mon bears. The huge grizzly bear, U. horribilis, occurs
throughout the mountain regions of the west but is rapidly
being exterminated. The long brown hairs that make up the
heavy coat are tipped with gray, hence the name " silver tip "
so often used. Several other species occur in America, the
largest of all the bears being the great brown Kodiak bear,
U. middendorffi, of Kodiak Island, Alaska.

The seals and the sea-lions, order Pinnipedia, are all aquatic,
mostly marine animals. The true seals, family Phocida, have
their legs so thoroughly modified for swimming that they are of
little use on land. The common harbor seals, Phoca mtulina,

3i6 ECONOMIC ZOOLOGY AND ENTOMOLOGY

have short stiff hair and are of no value for fur. The harp seal,
or Greenland seal, Phoca groenlandica, is highly prized, the
value of the catch sometimes reaching nearly half a million of
dollars.

The fur seals and the sea-lions belong to the family Otariidee.
The legs of these animals, while well adapted for swimming, are
still of some use on land, so that some of them can travel quite

FIG. 135. — A fur seal, Callorhinus alascanus, male, the herd on the beach
in the background. (Photograph by G. A. Clark.)

rapidly, though awkwardly, for a considerable distance. The
fur seals, genus Callorhinus, are by far the most important
members of the group. The value of the catch for 1910 was
$437,000, and for 1911, $423,000. They are found on land only
on certain islands in the Bering Sea where they come for breed-
ing. Early in the spring the old males arrive on the rocky
shores of the islands and await the females, which begin to come
early in June. Each male gathers around him a group of

MAMMALS 317

females, sometimes as many as thirty to eighty and, fighting
away all intruders, keeps guard over the harem for the rest of
the season. The young seals, or pups, are born soon after
the females arrive on the rookeries, the mothers nursing them
until they are themselves able to go into the water for their
food.

In September the seals of the Pribilof Islands begin leaving
and in about two months they are all gone. They go as far
south as the Santa Barbara Islands off the California coast,
then turning north again they keep along the general trend of
the shores in water about one hundred fathoms deep. After
traveling some 6000 miles or more without touching land, they
again reach their breeding grounds. The Russian herd of the
Commander Islands makes a similar migration along the coast
of Japan.

When Alaska first became a territory of the United States,
there were probably between two and three million seals on the
rookeries of the Pribilof Islands, but the relentless way in which
they have been hunted in the open sea in the past thirty, years,
has greatly reduced the size of this herd. In the early days of
Russian control the seals were killed indiscriminately. In
1834 the Russians established regulations protecting females on
the breeding grounds and permitting only young males, or
bachelors, to be killed. This has been the method of land
sealing ever since. In 1879 pelagic sealing began and many of
the mother seals were killed while they were on their migra-
tion journey or their feeding excursions. Thousands of the
pups were left on the beach to starve, and the herds were
depleted. In 1870 there were about 2,500,000 seals in. the
American herd, in 1890, 1,000,000 and in 1912 only about
250,000. The Russian herd has been about one-half as
large.

In 1911 the four governments, Russia, the United States,
England and Japan, the two former being owners of the herds
and the two latter participating in pelagic sealing, entered into
a treaty suspending pelagic sealing for fifteen years. In the
law of 1912 designed to give effect to this treaty, our Congress
included a provision prohibiting the land killing of males for

3i8 ECONOMIC ZOOLOGY AND ENTOMOLOGY

five years. Thus under present regulations no seals may be,
killed except the few that are allowed the natives for food.

The California sea-lion, Zalophus calif ornianus, and S teller's
sea-lion, Eumetopias stelleri, are both found along the rocky
shores of the north Pacific. Their hair is coarse* and of little
value for fur, but the skins are used for many purposes.

The Pacific walrus, Odobenus obesus, is the most important
species of the walrus family, Odobenidce. These animals attain
a length of ten to twelve feet and a weight of 1500 to 2000
pounds. The canine teeth are developed into two huge valu-
able ivory tusks sometimes as much as two feet long. They
feed principally on shell fish and crustaceans which they dig up
from the bottom of the shallow bays. These huge clumsy
animals, now comparatively few in numbers, were formerly
abundant, and furnished the natives of the northern shores
food, fuel, oils and excellent skins which were used in build-
ing houses, boats, dog harness, etc.

The order Primates is the highest order of animals, and in-
cludes the lemurs, monkeys, baboons, apes and man. The
lemurs, family Lemuroidea, are the lowest members of the
group. These are strange, squirrel-like or fox-like little ani-
mals living in the trees and bushes in Madagascar and other
near-by regions. The marmosets, family Callithricida, are
curious small long-haired, long-tailed animals, but little higher
in the scale than lemurs. They are found in tropical America.
The New World monkeys, family Cebida, are mostly smaller
and weaker than the Old World forms. Nearly all have long
prehensile tails which greatly aid them in their travels in the
tree tops. They all have a wide nose in which the nostrils are
separated by a broad septum and the openings directed
laterally. On this account they are known as platyrrhine
monkeys, while the Old World monkeys, which have the nose
septum narrow and the openings of the nostrils directed for-
ward, are called catarrhine monkeys.

The family Cercopithecida includes monkeys of Japan,
Asia, Africa and the Malay Archipelago. None of these has
a prehensile tail and some have only a very short tail. The
red-faced monkey of Japan is one of the best known of these.

MAMMALS

The baboons, of which there are about sixteen species, are
among the largest members of the family. They are bad
tempered, always ready for a fight, and, as they usually travel
in small companies, they make very formidable foes.

>'

FIG. 136. — "Bob," a monkey of the genus Cercopithecus. (Photograph
by D. S. Jordan.)

The family Simiida, includes the anthropoid apes, namely, the
gibbon, orang-utan, chimpanzee and gorilla. The gibbons are
small, long-armed and arboreal. About six species are found
in the Malay Peninsula and adjacent islands. The orang-

320 ECONOMIC ZOOLOGY AND ENTOMOLOGY

utans are found in the same regions as the gibbons. They are
much larger, reaching a height of four feet or more. They too
live among the tree-tops and swing themselves from limb to
limb by their long powerful arms.

In many respects, such as the shape of the head and the
hands and the size and activity of the brain, the chimpanzee,
Pan troglodytes, is much more man-like than any of the other
apes. It is a very imitative and teachable animal and captive
individuals are often trained to do many things that men do.
The chimpanzees live in tropical Africa. The gorilla, Gorilla
gorilla, is the largest of the apes and structurally most like
man. Its shorter arms and its habit of walking erect on the
ground indicate a higher stage of development, but the skull
is much less man-like than is the skull of the chimpanzee.

Belonging to the same order, similar in structure, yet sepa-
rated by the widest gulf as regards development of the intel-
lect, the power of speech, and many other qualities, is the
human species, Homo sapiens, the only species in the family
Hominidce. Although the members of the lowest savage tribes
differ in appearance from the highest civilized Americans or
Europeans more than do the members of different families in
some groups of the lower animals, yet all human beings are
considered as belonging to the same species for there are no
constant structural differences. We may, however, recognize
several more or less distinct races or varieties. There have
bedn discovered in Europe the fossilized remains of at least
one and perhaps two extinct species of man. These species
were much more primitive and bestial in structure than man
of to-day, but they are unmistakably the progenitors of the
present-day human type. They carry the history of man
back to the beginning of the present or Pleistocene geological
epoch. This was certainly at least five hundred thousand
years ago.

CHAPTER XXVI
DOMESTICATED ANIMALS1

The animals that we call domestic, while sometimes of kinds
and appearance very different from any wild animals that we
know, are yet certainly all descended from kinds that are or
were originally wild. There are wild pigs, wild goats, wild
doves, wild ducks, wild silk-worms. There are no wild dogs
nor probably any longer any true wild horses, but it is easy for
us to see from what wild animals our tame dogs and horses have
been derived.

It is certain from the records of history, and from ancient
pictures and carvings, and still more ancient bones and relics,
that man has had domesticated animals for the last ten thou-
sand years. How long before that he made a practice of tam-
ing and using and perhaps breeding his animal companions of
pre-historic times we may never know. In the caves where
are found the bones and rude implements of early man, that
primitive man of the Glacial epoch, there are also found the
bones of various animals, but these seem to be the remains of
kinds that were either his victims or his conquerors in the raw
struggle for existence of those ancient times. However, when
the pre-historic Egyptians and Cretans emerged from the
Stone Age into the earliest light of history they appear with
cattle, sheep, donkeys and dogs already fully domesticated.

Artificial Selection. — The domestication of animals is the
result of several different factors. First, there may be the
simple capture and taming and using of individuals of a wild
species. Then comes the rearing in captivity of young of this
species, and the easier taming of these home-reared individuals
because of their earlier acquaintanceship with man.

1 Most of this chapter is taken from Chapter XIX of "The Animals
and Man," by the senior author.

21 321

322 ECONOMIC ZOOLOGY AND ENTOMOLOGY

But in this rearing in captivity a new element enters almost
at once. That is the choosing or selection of certain of these
young to be allowed to grow up, and again the choosing among
these when grown up of those to be the parents of more young.
This selection may be almost unconsciously done, or it may be
made intentionally and carefully, so as to preserve the most
desirable individuals and have them give birth to others like
themselves.

Then there comes the crossing of special individuals or the
hybridizing with other races in the hope of adding or combin-
ing in the offspring the desirable qualities of both kinds of
parents. It is this careful selecting and crossing that are
usually meant when animal breeding is spoken of. And our
modern hosts of kinds or races of domesticated animals, the
scores of sorts of dogs and cats and cattle and pigeons and
ducks, have all been produced by "breeding." The acts of
choosing and hybridizing and choosing again and rearing from
these chosen offspring and again from each following genera-
tion until a form is arrived at very different in appearance or
habit from the original ancestor are called also artificial selec-
tion. It was largely on a basis of his observations of the
methods and results of artificial selection that Charles Darwin
founded his great theory of natural selection, which is, simply,
that nature unconsciously chooses or selects among animal or
plant individuals and kinds through the survival and producing
of young by those types born with traits advantageous in the
struggle for existence, this struggle being inevitable on account
of the geometrical ratio by which animals multiply.

The art of the animal breeder has reached in these later days,
the days since Darwin particularly, a very high stage of devel-
opment. It is becoming a science, because the breeders are
studying the laws of variation and heredity and making their
hybridizations and selections on a basis of the scientific knowl-
edge of these laws (see next chapter).

An important thing to note in connection with animal
breeding and artificial selection is that the selecting and modi-
fying are all made to change the animals along lines wholly
determined by man; lines that make the animals more useful

DOMESTICATED ANIMALS

323

or pleasing or curious to us but not better fitted to survive in
nature. In fact, most of these artificially induced changes tend
to unfit the animal for success in life unaided by man; they are
mostly degenerative changes. The loss of flight, the shortening
of legs, the over-development of fat, the production of crests
and plumes and ruffs, the loss of horns, the sluggishness and
helplessness that characterize the domestic animals of different

FIG. 137. — Assyrian hunters with great dogs; from an Assyrian wall
relief of 668 B.C., now in the British Museum. (After Keller.)

kinds, are all characters and conditions of degeneration. As
an outcome of the modern great interest and activity in the
methods and results of producing new races and types of
domesticated animals, the history of the origin of many of the
more widespread and useful of these animal races has been
unravelled. The following paragraphs give in briefest possible
form some interesting facts about the origin of our more
familiar animal companions.

324 ECONOMIC ZOOLOGY AND ENTOMOLOGY

There seems to be no doubt that the dog is the oldest
domesticated animal, as he is also the closest and the most
nearly universal animal companion of man. From among the
crudest of living human races to the most civilized and culti-
vated, the dog is everywhere and always at man's side, serving
him as faithful helper in the chase, in caring for his flocks and
home, and as companion of his table and fireside. The Bush-
men of Australia, the Esquimaux of the Arctic, the Indians of
the prairie and pampas, the cannibals of the scattered Paci-
fic Islands as well as the Caucasians of the world's great capi-

FIG. 138. — Thibet wolf, Canis niger, one of the wild ancestors of dogs.
(After Sclater.)

tals have their dog companions. And as is inevitable under
such many and different human conditions and stages of
civilization the kinds of dogs are many and very different.
About fifty breeds of sporting dogs and fifty of non-sporting
dogs are recognized by fanciers. There are many books filled
with the descriptions and illustrations of these varieties, which
range in size from the tiny toy dogs of Paris, that a lady can
carry in her muff, to the great Danes and St. Bernards that
stand three feet high and weigh one hundred and fifty pounds.
The origin of all these dog races is not to be found in any one

DOMESTICATED ANIMALS 325

wild species of dog-like animal, but in several. These wild
ancestors of the dog are certain wolves and jackals of various
lands. Dogs are probably descended from at least seven such
wild species, namely, the jackal, Canis aureus, of western Asia,
the landga, Canis pallipes, of India, the jackal wolf, Canis
anthus, of northeast Africa, the walgie, Canis niger, of Thibet,
and the coyote, Canis latrans, and dun-gray wolf, Canis occi-
dentalis, of North America.

The house cats, on the contrary, as various and as widely
distributed as they are, seem to be all descended from a single
wild species. This is the dun wild-cat, Felis maniculata, of
northeast Africa. All of the present races of house cats trace
their lineage back to Egypt. That the Egyptians were much
given to the possession and care of cats the numerous cat
mummies of their graves show. Cats were a sacred animal
for them under the special protection of the goddess Bast, a
goddess introduced into Egypt by Semitic influence. The
fanciers now recognize about thirty established races of cats.
They are grouped in two main classes, namely, long-haired
cats and short-haired cats, and in both groups appear certain
repeated colors as white, cream, gray, silver, yellow, black,
smoke "blue," brown, orange, "red," etc. The pattern may
be solid color or banded (tabby) or spotted (tortoise-shell) in
different colors. There is a Mexican hairless cat (just as there
is a Mexican hairless dog). The so-called Manx cats are
always tailless, but very short-tailed or even tailless individuals
occur occasionally in several other races, at least among the
short-haired kinds.

The horses of modern times can be traced back to two wild
ancestors, namely, Equus przewalski, of northern Asia, from
which all the Oriental, Mongolian, Arabian, North African
and East European races have sprung; and Equus caballus
fossilis, or the diluvial horse, of Europe, from which the Ger-
man, Norman, English and West European horses generally
have risen. In America fossil horses have been found back
through a series of geologic ages as far as the beginning of the
Tertiary Age forming a connected series from the small
Eohippus of the lower Eocene period, about the size of a fox,

326 ECONOMIC ZOOLOGY AND ENTOMOLOGY

and with four toes and splint of the fifth digit on each hind
foot; through Protorohippus and Orohippus of the Middle
Eocene, about fourteen inches high, with four toes on front
feet and three toes on hind feet, and no splints; through Meso-
hippus of the Oligocene, about the size of a coyote, and with
three toes on all its feet; through Protohippus and certain other
kinds of the Middle Miocene, about as large as Shetland ponies
and with three toes on all feet but with the side toes not touch-
ing the ground; to Equus, which first appeared in the Pleisto-

FIG. 139. — Restoration of the four-toed horse; based on a mounted
skeleton, sixteen inches high, in the American Museum of Natural History.
(After C. R. Knight.)

cene with only one developed toe and splints of the second and
fourth on each foot.

The color of the prehistoric horse is not known, but it was
probably dun with more or less well-defined stripes like a
zebra. The bones of human beings have been found associ-
ated with those of prehistoric horses in South America and in
Europe. Remains of horses are associated in Europe with
human relics of the Bronze Age, and figures of the wild horse

DOMESTICATED ANIMALS

327

are abundant among the drawings made by late Glacial man on
cave walls in Spain and France.

About a dozen living natural species and sub-species of the
genus Equus are known, including horses, asses, zebras, and the
now nearly if not quite extinct quagga. Of domesticated
races of horses and asses the number must run to more than a
score of well-marked distinct breeds, varying in size from the

FIG. 140. — Arion, a record-holding American trotting horse. (After

Plumb.)

minute ponies of the north British islands to the great Clydes-
dale and Percheron draught animals.

Donkeys have been derived from two wild species, the Nu-
bian Desert donkey, Equus toeniopus, and the onager, Equus
onager, of eastern Asia. Tame donkeys are figured in the
earliest of Egyptian and Assyrian drawings and carvings.

The races of domesticated hogs are also descended from two
wild races, the European wild boar, Sus scrofa, and another

328 ECONOMIC ZOOLOGY AND ENTOMOLOGY

FIG. 141. — The Banteng, Bos sondaicus, or wild ox of Java and South
Asia. (After Keller.)

FIG. 142. — White Hall Sultan, a Shorthorn prize bull. (After Plumb.)

DOMESTICATED ANIMALS

329

species, Sus vittatus, from eastern Asia. From this latter the
swine of China and those of the Romans and indeed most of the
European races have descended. The lake dwellers of Switzer-
land had domesticated hogs, and pig remains have been found
with prehistoric relics in Denmark. China has had domesti-
cated swine for thousands of years.

The many races of cattle all seem to trace back to two
sources, the wild banteng, Bos sondaicus, of Java and South

^-

FIG. 143. — The wild sheep of the Trans-Caspian steppes, Ovis arkal.
(After Keller.)

Asia, from which are derived the zebus, the old Egyptian long-
horns, and many of the races of Europe, such as the Spanish,
Albanian, Sardinian, Polish and brown Alpine cattle; and the
primitive wild ox of Europe, Bos primigenius, from which have
descended most of the English, North German, and Holland
races. This wild species persisted in Germany until the twelfth
century and in Poland up to the eighteenth century. A
few persons in America have tried to create a hybrid race by

330 ECONOMIC ZOOLOGY AND ENTOMOLOGY

crossing domestic cattle with the buffalo, but probably no
permanent result has been reached.

The domesticated races of sheep seem to have had three
original wild sources, Ovis musimon of South Europe, Ovis
arkal of Western Asia, and Ovis tragelaphus of North Africa.
Most of our present European and American races come from
the second named of these wild kinds. The earliest certain
remains of tame sheep appear in the Stone Age. In the Bronze

FIG. 144. — Typical American Merino ewe, a highly specialized breed of
sheep, with fine, close-set wool. (After Shaw.)

Age sheep domestication was well developed. The oldest
Assyrian drawings picture domesticated sheep, among which
the still persisting fat-tailed race appears. The Egyptians had
domesticated sheep in the times before the Pharaohs.

Our goats also are descended from three wild races, namely,
Capra cegagrus of Western Asia, Capra falconeri and Capta
jemlaica of the Himalayas. The earliest prehistoric indications
of tame goats come from the times of the Lake-dwellers. Jn
the Bronze Age they were common.

DOMESTICATED ANIMALS 331

Other mammals that are represented by domestic races are
the camel, the elephant, the water buffalo, the rabbit, the
ferret, the reindeer, the lama and alpaca, the guinea-pig, the
mouse, the rat, etc. But, excepting the rabbit, the domes-
ticated forms of these animals are only wild species tamed
and reared under man's hand but not much modified by breed-
ing. There are about fifteen races of domesticated rabbits
all of which probably trace their lineage back to wild species
native to Spain and Southern France.

FIG. 145. — Silver-laced Wyandotte cockerel.

Of birds there are domesticated races of doves, chickens,
turkeys, ducks, geese, swans, pea-fowls, pheasants, canary
birds, ostriches, cormorants and others. Of these the doves
and chickens are represented by the most varieties. Brown,
an English authority on domestic birds, lists more than seventy
races of chickens now living, thirteen races of ducks, ten of
geese, and eight of turkeys. Of pigeons there must be nearly as
many domestic races as there are of chickens. And yet all of

332 ECONOMIC ZOOLOGY AND ENTOMOLOGY

them, with all their extraordinary variety of crests, and ruffs,
and tails and plumage pattern, and all their various special
manners such as tumbling, dancing, and the like, are descended
from a single wild species, the common rock dove, Columba
lima, of Europe, Asia and North Africa.

The domestic races of chickens are by some naturalists also
held to be descended from a single wild species, the jungle fowrl,
Callus bankiva, which ranges from Hindukoosh to the Chinese
island of Hainau and through most of the Indonesian islands.
But other naturalists believe that one or two other wild species
of fowl are concerned in the ancestry of our barnyard hen.

\

FIG. 146. — Wild jungle fowls, Callus bankiva, of India. (After Brown.)

The domestic ducks are derived from the wild duck, Anas
boschas, and have evidently originated from this ancestor inde-
pendently both in China and in Europe. The domestic geese
seem to have an older origin than the ducks; in fact, geese are
probably the oldest of domesticated birds. The ancestor of
our races is the wild species, Anas cinereus. The Chinese races,
however, are descended from Anas cygmoides, and the early
Egyptians seem to have tamed and used the Nile goose,
Chenalopex egyptiaca.

The domesticated peacocks are descended from a wild species

DOMESTICATED ANIMALS 333

of India, Pavo cristatus. The turkeys trace their ancestry to
the wild Meleagris gallopavo of North America. The swans are
really only tamed wild kinds. Common species are the white
swan of Europe, Cygnus olor, the black swan of New Holland,
Cygnus atratus, and the black-necked swan of South America,
Cygnus nigricollis. The pheasants also are so far practically
only partially tamed wild species, whose eggs are usually
hatched under turkeys. Most of the kinds kept are from
the Orient.

Canary birds are descended from the wild species, Fringilla
canariensis, of the Canary Islands. But there has been some
crossing of them with other species of wild birds, especially
certain sparrow and finch kinds. There are now numerous
domesticated races which vary structurally and in color-pattern
as well as in voice. Many of the characters resemble the ruffs,
crests, and other plumage eccentricities of pigeons. The prin-
cipal place of canary bird breeding at present is in the Harz
Mountains of Germany.

Tamed cormorants are used by the Chinese and Japanese as
fishing birds, somewhat as falcons were used in days of old as
hunting birds. Indeed, in these same days cormorants were
used for sport. Charles I of England had a "master of the
cormorants." Nowadays, however, cormorant fishing is
a practical means of gaining food. A ring is placed about
the neck of each bird so as to prevent it from swallowing the
fish it catches. Several different species of cormorants are
thus used.

The ostrich is the most recent addition to the ranks of domes-
ticated birds. The tamed species is derived directly from the
widely distributed African ostrich, Struthio camelus.

Besides mammals and birds two or three species of fish, such
as the carp and goldfish, may be caljed domesticated. This
is certainly true of the goldfish, which is a product of Chinese
animal breeding. S ome most bizarre forms have been produced
in the thousand or more years in which this fish has been a
subject of selection and hybridization.

There are also, finally, at least two species of insects that have
a right to be called domesticated animals, namely, the honey-

334 ECONOMIC ZOOLOGY AND ENTOMOLOGY

bee and the mulberry silk- worm. The honey-bee, Apis mellifica,
has "been long used by man to obtain honey from, but only in
modern times has the species been the subject of true "breed-
ing." However, already several distinct races have been
produced. The bee is native to Europe and Asia, and "wild"
honey-bees in America are only communities established by
wandering swarms from hives, or from other " wild " commu-
nities which have descended from such escaped swarms (see
p. 185).

The silk-worm, Bombyx mori, has on the contrary been an
artificially bred animal for five thousand years, and scores of
races, with differently colored and shaped cocoons, exist. The
actual wild species from which the domesticated races are
descended is not known, but it is most likely some one of the
several wild species of northern India. The cocoons of cer-
tain of these wild Indian species are to-day still collected for the
silk and sold under the commercial name of "Tussoor" silk.
The ancient breeding and care of silk-worms was mostly done
in China and Japan. To-day it is carried on even more ex-
tensively in France and Italy (see p. 176).

CHAPTER XXVII
ANIMAL LIFE AND EVOLUTION

In all this book so far, we have made but little reference to
that phase of the study of animals which is usually called
animal evolution, or animal bionomics. We have taken the
many species of animals, and the great variety of form and
manner of life of these species, as facts, not problems; and we
have even described many kinds of extraordinary adaptations,
or modifications of structure and life to fit their possessors to
special or unusual conditions, without suggesting that the ques-
tion of the origin of these adaptations presents perhaps the
most important and attractive problem in all the study of
animals. We have postponed all such references deliberately
in order, primarily, to accent the facts and problems of eco-
nomic zoology throughout the book, and, secondarily, so that we
might take up the evolutionary phase of animal life in a single
compact chapter which should present an outline of the present-
day status of knowledge and speculation on the subject. By
putting this chapter of the book last in the present part we hope
to leave as a final impression in the elementary zoologist's
mind a special stimulus to further interest in and study of
animal life. For it is exactly the evolutionary phase of animal
study, the pursuit, that is, of the solution of questions as to the
why and how and the origin and change in animal form and
function and in animal kinds, which is the chief inspiration for
the really philosophic study of animal life. The usefulness of
knowing animals and their life, the enjoyment from a trained
observation of their manifold forms and behavior, and the drill
obtained from a careful study of their anatomy and physiology,
are all really achieved by human endeavor of a different type
from that required for the solution of evolutionary problems.
And all of them are much more really within the possible grasp

335

336 ECONOMIC ZOOLOGY AND ENTOMOLOGY

of beginning students. So that we believe it well to postpone,
as we have done in this book, any special consideration of the
subjects associated with animal evolution until the student has
had some personally acquired experience in the study of the
other phases of zoology.

Evolution a Fact. — Although there is much discussion of the
causes of evolution there is practically none any longer of
evolution itself. Organic evolution is a fact, demonstrated
and accepted. The many important open questions about
evolution concern the factors that originate and guide it.
Evolution means the blood relationship of organisms, their
descent from common ancestors, the origin of kinds by the
transformation or modification of other already existing kinds.

Evolution was not discovered by Charles Darwin nor by
Lamarck, whose names are, however, the greatest of all those
associated with it. It grew as a conception and a belief slowly
through all the years from the times of the Greeks until it
received its two most positive announcements and its two most
plausible explanations from Lamarck and Darwin. Darwin,
especially, presented such a full and convincing statement of
the facts that prove the reality of evolution that he put
evolution for all future time into our accepted understanding
of nature. Hence to Darwin belongs the greatest merit that
attaches to any name connected with the history of evolution.

The Causes, or Factors, of Evolution. — Evolution has two
conspicuous conditions of animal (and plant) life to explain;
first, all the different kinds of animals, and, second, all the
various adaptations or special fittings of these kinds to their
environment, so that they may live successfully as individuals
and persist as species. The factors or causal agencies pro-
posed to explain evolution must, therefore, to be acceptable,
explain not only the origin of species but their adaptations.
The factors proposed are many. Most conspicuous among
them are those called variation, heredity, 'selection and
segregation.

Variation and Mutation. — No two animals in the world are
alike. Whether widely related or so-called " identical twins,"
products of a single egg, there are differences or variations be-

ANIMAL LIFE AND EVOLUTION 337

tween them. Among the thousands of worker bees in the
same hive, all produced from eggs of the same queen, all reared
under the same conditions, and all looking superficially very
much alike, the trained eye of the student of variations has no
difficulty in discovering differences in size, color, character of
wing venation, number of wing hooks, etc., etc., differences
indeed in the condition of any part or attribute carefully
studied. The variations among the children in one family,
among the puppies or kittens in one litter, or among human
individuals or dogs or cats in general, are readily apparent,
because we are familiar with the human and dog and cat
bodies and attributes and readily recognize differences among
them. But these differences are no less real and discoverable
among the individuals of any other animal species.

These variations have been determined to be of two kinds.
One kind, called acquired, or fluctuating, is produced chiefly
by the inevitable environmental differences, kind and amount
of food, etc., to which the different individuals of a species or
even of one brood of the species, are subjected during their
development from embryo to adult. These fluctuating varia-
tions are apparently not directly inherited, and hence probably
have little to do with determining evolutionary change. They
may have some importance in aiding or hindering the individual
possessing them in their " struggle for existence," and by help-
ing to save or lose the lives of these individuals determine who
among them shall live to produce offspring and who shall not.
But even those saved by the possession of a favorable fluctu-
ating variation will not necessarily hand it on to their offspring,
and thus impress it on a future race.

Variations of the second kind are called congenital, by which
is meant that they depend primarily upon the character of
the germ cells from which the new individuals are produced,
and tend to appear whatever may be the character of the
environment during development. These variations are
directly heritable, that is, they are handed on to the offspring
of the individuals possessing them. What causes them in the
first place, what determines that the fertilized egg cells produced
by different individuals of the same species shall differ among

338 ECONOMIC ZOOLOGY AND ENTOMOLOGY

themselves, is not at all understood as yet. These congenital,
heritable variations may be, and usually are, small, but they
may also be large, and are then called "sports." They have
become especially familiar in recent years, under the name of
"mutations," in the condition of combinations or groups
occurring together, and thus making the individuals possess-
ing them readily distinguishable from the parent type. Recent
important discoveries in heredity have added to the interest
and importance of these congenital variations, and have thrown
a first faint light upon some of the conditions that attend their
origin. It is undoubtedly true that they are really the most
important actual beginnings of divergence among animals.
They are the building stones from which new species and better
adaptations are made. The importance of a knowledge of
variations on the part of animal and plant breeders is obvious.
It is especially important to distinguish between the heritable,
or congenital, and the non-heritable, or acquired, variations.
Only the first kind can be taken advantage of in the work of
making new races.

Heredity. — The extent and manner in which we inherit our
traits, both physical and mental, from our parents and an-
cestors has always been the subject of much speculation and
study. One of the greatest among students of heredity was
Francis Galton, only recently dead, whose studies, based
largely on human pedigrees, resulted in the formulation about
half a century ago of what is known as Galton' s "law of
ancestral inheritance." This states that on the average we
receive one-half our inheritance from our parents, one-fourth
from our grandparents, one-eighth from our great grand-
parents, one-sixteenth from our great, great grandparents, and
so on backward by halving fractions, the sum of them all being
one, or the total of our inherited qualities.

Such a law, or generalization,- about heredity is of interest
and value, but it gives us little basis on which to predict the
specific character of the results of any mating. It applies
to beings and characteristics in masses, and to average in-
dividuals. And it does not say what half, or fourth, or eighth,
we shall get from any particular pair of ancestors. That is,

ANIMAL LIFE AND EVOLUTION 339

it does not say what characteristics, but only what proportion
of a whole personality, shall be inherited. Hence it is a gen-
eralization that has not been of much practical use to breeders.
Recently, however, great progress has been made in the study
and elucidation of the exact heredity behavior, in successive
generations, of specific traits in animals and plants, so that there
are now well established certain new generalizations, or "laws,"
of heredity that are of immediate practical use to the breeder.
These new generalizations are known as the Mendelian
principles of heredity because some of them were first dis-
covered, by experimental work with plants, by Gregor Mendel,
an Augustinian monk of Austria. He did his work and
published his results in the years near 1860, but his conclu-
sions remained practically unknown until 1900. The Mendel-
ian principles cannot be expressed by any such single, simple
and comprehensive generalization as the Galtonian law of
ancestral inheritance. They do not attempt to treat of
the inherited personality of the individual as a whole but
concern themselves with the various separate characteristics
or traits of the individual. In heredity that follows the
Mendelian order — and it may be that all inheritance may be
shown to do this — there is no real or permanent blending, of
contrasted qualities, such as shortness and tallness, black and
white, rough and smooth, etc. Each of these conditions is
considered as an unmodifiable persistent unit character which
can be combined with or separated from others but cannot be
really blended with any. When two of these contrasted
characters are brought together by a cross-mating the offspring
of this mating may all show but one of these characters or
may all show an apparent blending of them. But in the next
generation, obtained by mating these offspring together, or
with other similarly produced offspring, both of the original
contrasted characters will reappear and by proper selecting
and mating each may be made to breed pure again. If the
original cross-mating has been of such a kind as to bring
together several different pairs of contrasting characters, there
will be opportunity in the second and later generations to
pick out individuals showing new combinations of unit char-

340 ECONOMIC ZOOLOGY AND ENTOMOLOGY

acters and thus representing new types or races. This
Mendelian feature of the combining and segregating, recom-
bining and resegregating of unchangeable unit characters, has
much importance for the practical breeder. It is a condition
depending upon the character of the germ cells produced by
the mated individuals and of their mated offspring rather
than of the somatic or general bodily character. For although
after the first cross-mating all of the offspring may be like
only one of the parents as regards a certain character, it will
be found that by allowing them to produce offspring of their
own that their germ cells really represent, in presumably equal
numbers, the contrasted characters of both parents.

The Mendelian order of heredity, although simple and easily
understandable in its more apparent aspects, cannot be de-
scribed in a few words. For a detailed account of it the student
should read some such modern treatment of it as Punnett's
"Mendelism, "or Bateson's "Mendel's Principles of Heredity."

A special phase of the problem of heredity is that of the in-
heritance of acquired characters. The congenital characters
of an individual, which are the outcome of the constitution
of the germ cells that produced it, are undeniably heritable.
Besides these characters, however, every individual acquires
during its life certain characteristics and variations which are
plainly due to the direct modification of the body parts and
functions by its lesser or greater use of those parts, or by the
direct influence of the abundance or scarcity of food, the rigor
or mildness of climate, the amount of sunlight or moisture,
etc. If these acquirements on the part of the parents are
heritable, and many of them are plainly personal adaptations
to the particular environment and circumstances of life in
which the individual finds himself, then inheritance by the
offspring would be a distinct advantage in leading a similar
life. If they could start endowed at birth with all their
parents had gained, their own going on with the adapting and
modifying process would lead to still further change away from
the original type, and thus in comparatively few generations
a new type much better adapted to a particular kind of
environment would be produced. This conception of personal

ANIMAL LIFE AND EVOLUTION 341

acquirement and adaptation, and the handing on of it by in-
heritance, resulting in a rapid cumulation of difference, was
the basis of Lamarck's explanation of evolution.

But owing primarily to the keenly critical examination of
the actual conditions and results of heredity by August Weiss-
mann, present-day biologists believe that such acquired char-
acters cannot be inherited, and hence that the modification
and adaptation of species has all to depend for its beginning
on favorable chance congenital variations, to be preserved
and slowly cumulated by the action of natural selection.
This belief makes it hard to gain a satisfactory conception of
the actual methods of evolution, because it makes an enormous
demand on variation, the precise working of selection, and the
extent of geological time. So that there is a strong tendency
among present-day biologists to search for other factors of
species modification, and to try to determine by experiment
the actual outcome in heredity of the modification of the body,
and, if possible, of its germ cells, by external influences. As
yet none of these experiments has given any sound basis for a
reinstatement of the belief in the inheritance of acquired
characters, but some of them do prove that the germ cells of
animals can be directly influenced by external conditions, and
that young, differing markedly from their parents, are produced
by these influenced germ cells. That is, environmental
influences which may modify the body may also modify the
germ cells and thus cause change from the species type in the
offspring which can be handed on by inheritance to their own
progeny, but these changes will not be replicas of the acquired
variations of the parents. Thus the only result on heredity
of a better exercise of an animal's capacities will be to give its
offspring more vigor and a better start in life perhaps, but it
cannot endow the offspring with the parents' actual gain in
fitness. Education can be handed on only by tradition, not
by true germinal inheritance.

Another special subject in connection with heredity which
should be mentioned in this book because of its importance in
the work of the breeder, is that of the alleged advantage or
disadvantage of in-breeding. In the light of the Mendelian

342 ECONOMIC ZOOLOGY AND ENTOMOLOGY

discoveries in-breeding is seen in a new aspect. The mating
together of closely related individuals derives both its ad-
vantages and disadvantages from the probable occurrence in
both parents of similar unit characters. Their offspring
will thus get a double portion of each common character. If
it is a good trait advantage will come of the mating, if a bad
trait disadvantage. Thus to accent and fix quickly a good
trait close breeding will be useful; to remove a bad trait out-
breeding will be necessary. In addition out-breeding practi-
cally always adds, vigor to the offspring. But in many cases
of in-breeding vigor is not lost until after several or many in-
bred generations have been produced.

Selection, Natural and Artificial. — Natural selection, which
is a phrase summing up the presumable result of the interaction
on animals and plants of several distinct natural causes and
conditions, has been generally considered since Darwin's time
to be the principal factor in evolution. It is the factor chiefly
relied on by Darwin in his explanation of evolution, and its
formulation is Darwin's principal original contribution to
evolutionary discussion.

Natural selection depends upon, first, the geometrical ratio
of reproduction, resulting in the production of more individuals
than there is food or space for, this overproduction of living
creatures necessitating a "struggle for existence" among them;
second, the universal occurrence of variations, small or large,
among all the myriads born; third, the presumption that some
of these variations will give advantages to certain individuals
in this struggle, resulting in their success and growth to
maturity and production of young; fourth, the inheritance
by the young of the advantageous variations of their parents,
and their handing on of them to their own succeeding genera-
tions thus constituting a new race or species characterized
by the original new variations and succeeding new and better
ones. Thus there is a "natural selection" of individuals
within a species, and also a "natural selection" of specially
favored species in their competition with other species. The
whole steadily acting combination of conditions results in a
constant movement from one kind of animal or plant type to

ANIMAL LIFE AND EVOLUTION 343

another and to the establishment of divergent lines of this
movement, these changes in type and lines always being in
the direction of better adaptation or fitness to the conditions
of life. Several recent discoveries based upon the experi-
mental study of variation and heredity have much lessened
the importance of natural selection as a species-forming
agent. It still remains, however, the chief explanation of
adaptation.

Artificial selection has much less in common with natural
selection than popularly supposed. It depends, however, as
natural selection does, upon the existence of variations and
heredity and upon the culling out of certain individuals which
are allowed to produce offspring while the great majority are
not so allowed. This culling out, or selection, however, is made
according to the needs and whims of man and not at all upon
the basis of natural advantage or fitness. As a matter of
fact most artificial selection is in the direction of unfitness
for existence under natural conditions. Very few domestic
races of animals could hold their own in nature.

In artificial selection, man, by being able to control matings
exactly, has a means of modifying races much more rapidly
than they are usually modified in nature. Man not only selects
to live the individuals showing certain wished-for variations,
but can mate together individuals which show these particular
variations in highest degree. Or he can mate individuals
showing different variations which he would like to combine.
By taking advantage of the great present-day extension of our
knowledge of the facts and laws of variation, inheritance, and
selection the artificial breeder can work much more rapidly
and with much more accuracy than ever before.

Segregation, or Isolation. — The modification of species
either in nature, or under the hands of man, always includes as
part of the process the segregation, or isolation, from the whole
mass of individuals of a small number specially like each
other. This is effected in natural selection by the saving of the
few with advantageous variations and the death of the others;
in artificial selection, by the culling out process of the breeder.
These few saved or selected individuals breed together and are

344 ECONOMIC ZOOLOGY AND ENTOMOLOGY

the beginners of a new type within the species, that is, of a
modification of it.

Such segregation can also occur in nature, and certainly often
does, by the chance isolation by geographic barriers of a few
individuals of a species, which are thus prevented from
breeding miscellaneously with the other members of the species,
but must breed together, thus tending to perpetuate their own
variations and idiosyncrasies. Such geographical isolation
has certainly led to the origination of many species modifica-
tions called geographic races or varieties, and with time and
the cumulation of these modifications through many genera-
tions, to many actual new species.

It is possible also that certain physiological causes of the
enforced mating together of certain few individuals, thus pro-
ducing a sort of physiological segregation or isolation, may lead
to species modification. Personal antipathies, separate times
of coming to maturity, etc., may act as such agents of physi-
ological segregation.

The Proof of Evolution. — Despite our statement at the begin-
ning of this chapter that the fact of evolution is so generally
accepted that there is no longer any discussion of its proofs,
it may be advisable to state here succinctly on just what basis
the general belief in evolution rests. This basis is that of the
observed facts in four general biological subjects, namely,
paleontology, comparative anatomy and physiology, embry-
ology and development (ontogeny), and plant and animal
geography.

By a study of animal fossils from all the different fossil-
bearing strata of the earth's crust, it is evident that in the
earliest geographical epochs only very simple animals lived,
such as Protozoa, the simpler invertebrates, and, perhaps, a few
simple Chordates. With the passing of time there came into
existence more specialized or higher invertebrates, then the
simplest true vertebrates, as the fishes and amphibians, and
finally the higher kinds, as the reptiles, birds and mammals.
The paleontological record is, in other words, plainly a record
of organic evolution.

A careful comparison of the structure of different animals

ANIMAL LIFE AND EVOLUTION 345

shows such fundamental similarities as to indicate beyond
doubt an actual blood relationship of wider or closer degree
among them. The superficial differences among animals
evidently of common identity of basic structural plan are
exactly those which life under differing conditions would call
for as helpful modifications or adaptations. This same condi-
tion of fundamental likeness with superficial differences is true
also of the functions or physiology of animals.

A close study of the complete life history or development of
an animal from beginning egg to full-grown adult condition,
reveals the fact that this course of personal development
shows striking similarities both with the paleontological record
and with the revelations of comparative anatomy. Ontogeny
is said to recapitulate phylogeny, by which is meant that each
animal in its personal development runs through swiftly, but
more or less obviously, a much abridged recapitulation of the
stages of the evolution of the species to which it belongs.

Finally the facts of the present and past distribution of
animals over the earth's surface reveal such striking conditions
of close animal relationships accompanying the present or past
continuity of land and water masses, and such wideness of
relationship associated with long separated regions, that only
the explanation of evolution is sufficient to account for these
facts. In Australia, which is a great land mass long separated
geographically from other continents, the animals, except such
kinds as are spread by man unwittingly or intentionally, or
are easily distributed by ocean currents, are of kinds very
different from those elsewhere in the world. But in Africa
and South America, which are more widely separated geo-
graphically but have been connected in geological periods not
so very remote, there are many fairly close relationships among
the animals of the two regions. The differences, also, are just
about as great as the length of time of the actual separation of
the two continents would make probable. By such zoo-geo-
graphic studies carried on for many kinds and groups of ani-
mals, and for many regions of the earth, a great army of facts
has been collected which correspond perfectly with the theory
of descent, i.e., evolution.

346 ECONOMIC ZOOLOGY AND ENTOMOLOGY

Animal Ecology and Adaptations. — The relation of animals
to their physical environment, and their inter-relations with
other animals and plants, constitute a special phase of biologic
study called animal ecology. As these special relations are
associated always with special adaptive conditions of structure
and function, the subject of ecology includes, in a way, the
subject of adaptations, and thus comes with particular perti-
nence under the attention of the student of animal evolution.

The relations and varied adaptations of animals in connec-
tion with food getting, defense and offense, production and care
of young, and similar other activities common to all animals
but performed in extraordinarily various ways, are most
stimulating subjects of investigation. As these adaptations
are functional as well as structural, such subjects include the
study of the behavior, instincts and intelligence of animals, and
become thus directly related to the problem of the origin of our
own instincts and intelligence. Among the various highly
developed special adaptations of animals those of color and
color pattern, of parasitism, and of different phases of mutual
aid, offer unusually interesting subjects of special study, and
may be introduced here by a few paragraphs.

Color is produced by the presence of pigment in the surface
parts or by the structural character of the epidermal hairs,
feathers, or scales with which the animal's body may be
covered. By reflection and interference effects, due to the
laminated or striated structure of these parts, brilliant metallic
or iridescent colors are produced, such as the blues, purples and
greens of the humming-birds, butterflies, fishes, etc. The
most obvious use of the colors depends largely upon their
arrangement into definite patterns and on the harmonizing of
these color patterns with the environment in such a way as to
make the animal more or less indistinguishable when at rest
and thus hide it from its enemies. The phenomena of pro-
tective resemblance and mimicry are among the most highly
developed and extraordinary of animal adaptations.

Some of the many curious conditions of structure, develop-
ment and habit, developed in connection writh the adoption of a
parasitic life have already been described in this book.

ANIMAL LIFE AND EVOLUTION 347

Another kind of association among animals is that based on a
greater or lesser degree of mutual aid derived from this associa-
tion. It appears in two types, one exemplified by com-
mensalism and symbiosis, in which two different kinds of
animals live together temporarily or permanently to their
mutual benefit or at least to the benefit of one kind and
little or no injury to the other, and the other exemplified by a
gregarious and social or communal life, in which a number of
individuals of the same kind live together in temporary or
permanent bands or in large family communities.

The first type is illustrated by the hermit crabs that carry
colonies of hydroid polyps on their shells, the little crab being
protected from enemies by the stinging threads of the polyps,
while the sessile polyps gain an advantage by the crab's
movements and probably by getting small bits from the crab's
clumsy tearing up of its own food. Especially developed is
the commensal relation between certain insects called ant-
guests and the ants which serve as their hosts. Over 1500
species of insects, mostly small beetles and flies, live in the
nests of various ants, some as robbers, some as tolerated para-
sites, and some as desired commensals. These latter provide
the ants with certain kinds of special food produced by their
bodies, and aid in cleaning both the nests and the ants them-
selves, while they in turn receive food from the storerooms of
the ants, or even by regurgitation from their mouths.

Of the second type the life of the communities of the social
wasps and bees and ants, already described in some detail
elsewhere in this book, is the best example. The highly
specialized communities of the honey-bee and of the ants are
a splendid illustration of the possibilities and great advantages
of adaptations based on the principle of mutual aid. It is
of course the extreme development of the mutual aid factor
in human life that makes man the highly successful and noble
animal he is.

PART II

CHAPTER XXVIII

PARASITIC PROTOZOA CAUSING DISEASES OF MAN
AND DOMESTIC ANIMALS

Parasites and Disease. — More than two hundred years
ago it was known that small animal parasites were associated
with and were the cause of certain diseases, and it soon came
to be generally believed that all of our ills were in some way
caused by such parasites, known or unknown. At first only the
parasitic worms and other large parasites were known, but
later it was discovered that many of the Protozoa and minute
plant parasites, the bacteria, also caused many diseases. To-
day we know definitely that such diseases as typhoid, cholera,
tuberculosis and many others are caused by the presence of
bacteria in the body and that such maladies as malaria,
sleeping sickness, syphilis, and many fevers are caused by
Protozoa.

Then there is a long list of other epidemic diseases, such as
smallpox, measles and scarlet fever, the exact cause of which
has not been determined. Many of these are believed to be
due to micro-organisms of some kind, and if so these parasites
will almost certainly sooner or later be found. Curiously
enough most of the diseases in this last class, and many of those
that are caused by bacteria, are contagious, while all that are
caused by animal parasites are, as far as is known, infectious
but not contagious. It is important that we keep in mind this
distinction. By contagious diseases are meant those which
are transmitted by contact with the diseased person, by touch,
or by the breath or the effluvia from the body, or by the use

349

350 ECONOMIC ZOOLOGY AND ENTOMOLOGY

of the same articles. Smallpox, measles and influenza are
examples of this group. By infectious diseases are meant those
which are disseminated by contaminated water or food, or other
infected substances introduced into the body in some way.
Typhoid, malaria, yellow fever, and cholera, and others are
examples of this class. Thus it is evident that all of the con-
tagious diseases may be infectious, but most of the infectious
diseases are not as a rule contagious, although some of them
may become so under favorable conditions.

Just one example will show the importance of knowing
whether a disease is contagious or infectious. Until a few years
ago it was believed that yellow fever was highly contagious,
and every precaution was taken to keep the disease from
spreading by keeping the infected region in strict quarantine.
This often meant much hardship and suffering and always a
great financial loss. We now know that it is infectious only
and not contagious, and that all this quarantine was unnec-
essary. The whole fight in controlling an outbreak of yellow
fever, or in preventing such an outbreak, is now directed against
the mosquito, the sole agent by which the disease can be trans-
mitted from one person to another.

Definition of a Parasite. — A parasite is a living organism
that lives in or on some other organism from which it derives
its nourishment for the whole or a part of its existence. As a
general thing we are accustomed to think of a parasite as work-
ing more or less injury to its host. As a matter of fact the num-
ber of parasitic organisms that are seriously detrimental to
the welfare of their hosts is comparatively small while the
number of parasites that do no appreciable harm, and of whose
existence in the body the host is often not even aware, is large.

DISEASES CAUSED BY AMCEB.E

Amoebic Dysentery. — A species of Amoeba, A. dysenteries, is
found associated with a disease of man known as amoebic
dysentery. This disease occurs most commonly in tropical
countries, but is sometimes met with in temperate zones.
The amceba3 are found in the alimentary canal, usually in

PARASITIC PROTOZOA 351

the large intestine, where they produce serious ulcers or
at least extend and prevent the healing of ulcers started from
other causes. Amoeboid organisms are found in the tissues
of the brain in animals affected with hydrophobia, and
similar organisms are found in the skin of smallpox patients,
but it has not been shown that they cause these diseases.
Several other Amcebce may be found in various tissues or
organs of men and many of the domestic animals, but they
are usually regarded as harmless.

One species, Amoeba meleagridis , is, however, the cause of a
fatal disease of turkeys known as entero-hepatitis, or "black-
head." The disease is now spread
throughout North America, and when
once a farm has become infected no
further attempts should be made to
raise turkeys there, at least for some
years. Turkeys become infected by
swallowing the encysted amoebae that
have been distributed in the drop-
pings from infested turkeys. Young
turkeys may become infected from FlG I4?Z Amoeba dysen-
encysted amoeba? which adhere to teria. The two lower para-
the shells from which they hatch. *£$££*$? ™£
In the alimentary canal of their host smaller spherical mass in
the amoebae break from their cyst and the upper left corner is an
cause ulceration of the intestine and
abscess of the liver. Diarrhea soon
begins, and in the later stages of the illness the head of the
turkey turns black.

The same Amoeba often occurs in other birds, such as chick-
ens, ducks, quail, pigeons, sparrows, etc., but it seldom causes
serious trouble in any except turkeys, and young turkeys are
much more susceptible than old ones. It is believed that
sparrows have been an important factor in the spread of the
disease.

There is no efficient remedy. Turkeys should not be
allowed to run with other fowls and they should be kept only
in uninfected places.

352 ECONOMIC ZOOLOGY AND ENTOMOLOGY

SLEEPING SICKNESS AND OTHER DISEASES CAUSED BY
TRYPANOSOMES

To the group of parasitic Protozoa known as trypanosomes
belong some of the most important enemies of mankind.
These elongated, spindle-shaped, delicate little organisms, are
found in insects, reptiles, birds and mammals. Many of the
most important species are conveyed from one vertebrate host
to another by means of insects, the parasites often undergoing
some stages of their development in the invertebrate host.

FIG. 148. — Trypanosoma gambiense. Various forms from blood and cere-
brospinal fluid. (After Manson.)

Trypanosoma lewisi, a parasite of rats, is perhaps the
best known, as it is always common wherever rats are found.
These parasites are transmitted from rat to rat by the common
rat-louse and probably also by rat-fleas. They do not seem
to injure the rats. Trypanosoma gambiense is the most
important member of this group, as it is the parasite that
causes the disease known as sleeping sickness, a scourge
that for the last few years has created more interest and

PARASITIC PROTOZOA

353

been more carefully studied than any other disease. It
has spread rapidly over a large part of Africa, killing hundreds
of thousands of the natives of these regions. The early symp-
toms of the disease are various, but infection is usually soon
followed by fevers, and the patient gradually becomes anemic
and physically and intellectually feeble, with an increasing
tendency to sleep. As the stupor deepens the patient loses
all desire or power of exertion and soon succumbs to the
uncanny death.

Other animals beside man may be infected with this parasite,
but it does not seem to injure them. The parasite is carried

FIG. 149. — Tsetse-fly. (After Manson; two and one-fourth times natural

size.)

from one host to another by a species of tsetse-fly, Glossina
palpalis, which resembles somewhat our common stable-fly.
It is now known that another tsetse-fly, G. morsitans, is
also an agent in the transmission of this disease. When the
fly sucks blood from an infected animal some of the trypano-
somes are taken into its body where they undergo certain
changes, the fly usually not becoming infective until about
three or four weeks later. It is then capable for a period of

23

354 ECONOMIC ZOOLOGY AND ENTOMOLOGY

four months or more of infecting any person or other animal
that it bites.

G. palpalis is found only in tropical Africa and is limited in its
distribution there to certain very definite, narrow, brushy
areas along the water's edge. If these places can be avoided
there seems to be little danger. Those who are fighting the
disease have found that if the brush in the vicinity of watering-
places and ferry-landings is cleared away such places become
comparatively safe. These flies do not lay eggs but produce
full-grown larvae which soon pupate in the ground.

Trypanosoma cruzi is another species that causes a serious,
often fatal, disease in Brazil. It is transmitted by the bug
Conorrhinus megisius, belonging to the family Reduviidce, order
Hemiptera. This bug has habits very similar to those of the
bedbug, inhabiting houses and biting sleeping persons. Kala
azar, a chronic disease occurring in the Mediterranean region
and in many places in Asia, is caused by a parasite, Leish-
mannia donovani, somewhat resembling the trypanosomes.
The infection is probably acquired by the biteiof an insect,
perhaps a bedbug. A similar disease, called Delhi boil, occurs
in the same region and also in Brazil, and it is thought that
infection may be carried to a wound by house-flies.

There are several diseases of domestic animals caused by
trypanosomes. Tsetse-fly disease, or nag ana, is one of the
most serious scourges of domestic animals in Central and
Southern Africa. In some sections it is almost impossible to
keep any kind of imported animals on account of this disease,
which is caused by Trypanosoma brucei. This parasite is to
be found in several different kinds of native animals which seem
to be themselves practically immune but are always a source
of danger when non-immune animals are introduced. The
tsetse-fly, Glossina morsitans, one of the most dreaded insect
pests of Southern Africa, is largely responsible for the trans-
mission of this disease, but one or two other species of tsetse-
flies may also act as hosts for the parasite. All through Asia,
in parts of Africa and in the Philippines there is a very serious
disease of horses and cattle known as surra. This disease,
which also affects camels, elephants, buffaloes and dogs in

PARASITIC PROTOZOA 355

regions where it occurs, is caused by Trypanosoma evansi and
is probably transmitted by the bites of stable-flies (Stomoxys)
and horse-flies (Tabanida).

In 1906 some cattle that had been imported into America
from India for experimental purposes were found to be in-
fected by the parasite which causes this disease. Fortunately
this discovery was made while the cattle were still in quaran-
tine. All those infected were destroyed and the disease thus
stamped out before it had a chance to spread. A disease
similar to both nagana and surra, and known as murrina, has
recently been found affecting horses and mules in Panamas.
It is caused by Trypanosoma hippicum. It is believed that the
parasite is carried mechanically from one host to another by
flies that visit the sores due to wounds of various kinds on the
animals.

Dourine, or mal du coit, is a serious disease of horses that
has been introduced into North America, where it appears from
time to time in widely separated parts of the west. It is caused
by Trypanosoma equiperdum, and is transmitted during breed-
ing, perhaps rarely by bites of flies or fleas. As soon as infect-
ed animals are discovered they are destroyed, and the disease
is now almost or quite stamped out. Trypanosoma equinum
causes a deadly disease of horses, known as mal de caderas, in
Brazil and other parts of South America.

Several other species of trypanosomes are found in wild and
domestic animals. Almost any of these may at any time be-
come of more or less economic importance when susceptible,
non-immune animals are brought into the regions where the
parasites occur, or when the parasites by some means are
introduced into new regions.

RELAPSING FEVERS AND OTHER DISEASES CAUSED BY
SPIROCH,ETES

The spirochsetes are very minute, thread-like parasites
closely related to the trypanosomes. They occur in shellfish
and in the alimentary canal or blood of certain fish, birds and
mammals where they apparently do no harm, but some

356 ECONOMIC ZOOLOGY AND ENTOMOLOGY

produce diseases in man and other animals. The most im-
portant of these are the relapsing fevers of which there are

FIG. 150. — Relapsing fever tick, Ornithodorus moubala. (About four
times natural size.)

FIG. 151. — The fowl-tick, Argas persicus. (About four times natural size.)

several types caused by as many different species of Spiro-
chceta. The relapsing fever of Africa, or African tick fever,

PARASITIC PROTOZOA 357

is one of the most dreaded of these. It is caused by S. dutioni,
and is transmitted by the bite of a common African tick,
Ornithodorus moubata, which has habits similar to those of the
bedbug. The relapsing, or remittent fever of Europe is caused
by S. recurrentis, and is probably transmitted by some blood-
sucking insect, possibly by the bedbugs. The relapsing fever
of America is caused by 5". novyi. The mode of infection is not
definitely known. Yaws, a disease of the tropics which is
characterized by numerous ulcerating sores on the body, is
caused by Spirochata pallidula. It is thought that the common
house-fly plays an important part in its dissemination. Of the
diseases of domestic animals caused by spirochsetes a fatal
disease of fowls known as spirochaetosis is the most important,
as it may kill all the fowls in the chicken yard in the course of a
few days. It is caused by Spirochada marchouxi (gallinarum)
and is transmitted by ticks, usually by the common chicken
tick, Argas persicus.

Syphilis. — To the genus Treponema belongs a single im-
portant parasite, T. pallidum, that used to be classed with the
Spirochceta. It is the cause of that terrible disease, syphilis,
which results in untold suffering not only among those individ-
uals who are responsible for its dissemination but among many
innocent persons as well. Much of the syphilitic disease that
is in the world to-day is due to the infection of infants before
or at the time of their birth.

MALARIAL FEVERS AND OTHER DISEASES CAUSED BY SPOROZOA

The Sporozoa,or spore-forming Protozoa, include the smallest
but by no means least important members of the branch.
They are all parasitic and vary greatly in appearance, organiza-
tion and life history. They are so very plastic that they can
adapt themselves readily to their various hosts. Some of
them live during some stages of their development in the blood
cells of man and other vertebrates, the rest of their life being
passed in insects or other invertebrates. Malarial fevers are
caused by such parasites. Those that occur in man belong to
the genus Plasmodium. The three most important species are

358

ECONOMIC ZOOLOGY AND ENTOMOLOGY

2.

Some may be taken
into the stomach
of the Hlosquito w'nen
it bites

&

FIG. 152. — Diagram to illustrate the life-history of the malarial para-
site, i is a red blood corpuscle; 2 to 7 show the development of the
parasite in the corpuscle; abed and a' V c' and e the development of the
parasite in the stomach of the mosquito; / g h i the development in the
capsule on the outer wall of the stomach of the mosquito, k in the salivary
gland.

PARASITIC PROTOZOA 359

vivax, malaria and falciparum, causing respectively the tertian,
quartan and remittent types of malarial fever in man.

The life history of all of these is very similar, the principal
difference being in the length of time it takes them to sporulate.
Let us begin with the parasite after it has been introduced into
the blood and trace its development there. At first it is slender
and rod-like in shape. It has some power of movement in the
blood-plasma. Very soon it attacks one of the red blood-
corpuscles and gradually pierces its way through the wall and
into the corpuscle substance; here it becomes more amoeboid
and continues to move about, feeding all the time on the
corpuscle substance, gradually destroying the whole blood
cell. As the parasite feeds and grows there is deposited within
its body a blackish or bro\vnish pigment known as melanin.

During the time that the parasite is feeding and growing it
is also giving off waste products, but as the parasite is com-
pletely inclosed, in the corpuscle wall these waste products
cannot escape until the wall bursts. After about forty hours,
if the parasite is vivax, or about sixty-five hours if it is malaria,
it becomes immobile, the nucleus divides again and again and
the protoplasm collects around these nuclei, forming a number
of small cells, or spores, as they are called. In about forty-
eight or seventy-two hours, depending on whether the parasite
is vivax or malaria, the wall of the corpuscle bursts and all these
spores with the black pigment and the waste products that
have been stored away within the cell are liberated into the
blood-plasma.

These spores are round or somewhat amoeboid and are carried
in the blood-plasma for a short time. Very soon, however,
each one attacks a new red corpuscle and the process of
feeding, growth and spore-formation continues, taking exactly
the same time for development as in the first generation, so that
every forty-eight hours in the case of vivax, and every seventy-
two hours in the case of malaria, a new lot of these spores and
the accompanying waste products are thrown out into the
blood. Thus in a very short time many generations of this
parasite occur, and thousands or hundreds of thousands of the
red blood corpuscles are destroyed, leaving the patient weak

360 ECONOMIC ZOOLOGY AND ENTOMOLOGY

and anaemic. It will be seen, too, that the recurrence of the
chills and fevers is simultaneous with the escaping of the
parasites from the blood corpuscles, together with the waste
products of their metabolism. These waste products are
poisonous, and it is believed that this great amount of poison
poured into the blood at one time causes the regular recurring
crisis.

FIG. 153. — Malarial mosquito, Anopheles maculipennis, on the wall.
(About six times natural size.)

We have already learned that such a process of asexual re-
production cannot go on indefinitely, but for a long time those
who were studying these parasites were at a loss to know where
the sexual stage took place. Many men have worked on this
problem but perhaps most .credit will always be given to
Ronald Ross, a surgeon in the English army, who, after many
months of continuous labor, finally demonstrated that the

PARASITIC PROTOZOA 361

sexual stage of the development of these parasites takes place
in the stomach of the mosquito.

It was found that certain of the parasites in the blood do not
go on with their development there. When these particular
parasites are taken into the stomach of most mosquitoes they
are digested with the rest of the blood. But when they are
taken into the stomach of mosquitoes belonging to the genus
Anopheles, or other closely related genera, they are not digested
but go on with their development. Conjugation takes place,
resulting in the production of a new form of the parasite, the
zygote, that makes its way through the walls of the stomach on
the outside of which it forms a little nodule. Within these
nodules further division and development takes place, until
finally the nodules burst open and many thousand minute rod-
like organisms, sporozoites, formed by the repeated division
of the zygote, are turned loose into the body cavity of the
mosquito. Owing to some unknown cause these little organ-
isms collect in the large vacuolated cells of the salivary glands
of the mosquito, and when the mosquito bites a man they pour
down through the ducts with the secretion into the beak
and are thus again introduced into the human circulation.

The nodules, or cysts, on the walls of the stomach of the
mosquito may contain as many as ten thousand sporozoites,
and as many as five hundred cysts may occur on a single
stomach.

It takes ten, twelve, or more days from the time the parasites
are taken into the stomach of the mosquito before they can
complete their transformations and reach the salivary gland,
the time depending on the temperature. So it is ten or twelve
days, or sometimes as long as eighteen or twenty days, from the
time an Anopheles bites a malaria] patient before it is dangerous
or can spread the disease. On the other hand, the sporozoites
may lie in the salivary gland alive and virulent for several
weeks. It does not give up all the parasites at one time, so that
three or four or more people may be infected by a single
mosquito.

The findings of Ross have been verified many times, and
many experiments have proven beyond any doubt that this is

362 ECONOMIC ZOOLOGY AND ENTOMOLOGY

the only way in which malaria is transmitted, and that the
low-lying lands or swamps have nothing whatever to do with
malaria except in so far as they furnish a breeding place for
mosquitoes. Much less, then, can the mists or bad air — -mal
aria in the Italian — produce malaria. Without mosquitoes
there is no malaria.

TEXAS FEVER or CATTLE

To the genus Babesia (formerly known as Piro plasma) be-
long several species of blood parasites that are of great eco-
nomic importance. In the vertebrate host they live in the

FIG. 154.-

-Texas fever tick, Margaropus annulatus, young adult not
fully gorged. (About four times natural size.)

red blood corpuscles, and they are transmitted from one
animal to another by means of ticks. The most important of
the diseases caused by the members of this genus is a disease
of cattle known in the United States as Texas fever, or tick
fever, or splenic fever. It occurs in nearly all tropical and
subtropical and in many temperate regions, and outside of
the United States is more commonly known as "red water."
In the United States it causes an annual loss estimated at $100,-

PARASITIC PROTOZOA 363

000,000, and in many parts of the world it is almost impossible
to keep cattle because such a large per cent, of them die of
the disease. The parasite, Babesia bigeminum, that causes the
disease is transmitted by the common cattle tick, or Texas
fever tick, Mar gar opus annulatus, in the United States, and by
closely related species in other countries. The infection is not
direct, that is, the tick does not feed on one host, then pass
directly to another, carrying the disease germs with it. Unlike
many other ticks the Texas fever tick does not leave its host
until it is fully developed. When the female is full grown
and gorged she drops to the ground and lays from 1000 to
4000 eggs from which the minute "seed ticks" soon hatch.
These make their way to some nearby blade of grass or shrub
and at the first opportunity attach themselves to any cattle
that may pass that way.

If the mother tick feeds on an animal that is infected with
Texas fever some of the parasites that she takes into the body
will find their way into her eggs, and the young ticks that hatch
from these will be infected and ready to transmit the disease
to their host.

It has been found that the Southern cattle in the regions
where the ticks occur normally usually have a mild attack of
the disease when they are young, and although they may be
infected with the parasite all the rest of their life it does not
affect them seriously. But these cattle are a source of danger
when taken into a region where the ticks do not occur naturally,
for the larvae that issue from the eggs laid by the infected adult
ticks may attack non-immune cattle which soon sicken and die.

At present in the United States no cattle south of a certain
quarantine line are allowed to be taken north except under
very strict regulations. It has been demonstrated that by a
system of feed-lots and pasture rotation many infested regions
may be made perfectly safe. The aim is to let all of the ticks
drop to the ground on land where they may be destroyed or
left to starve. When it is necessary to treat cattle that are
badly infested with ticks, large vats are built and filled with a
dipping solution and the cattle are then driven through it.
Many different kinds of solutions have been used for this pur-

364 ECONOMIC ZOOLOGY AND ENTOMOLOGY

pose. One should consult some of the Government or Experi-
ment Station Bulletins (see page 419) for directions for making
and using these.

Similar diseases caused by other species of the genus Babesia
occur in horses, sheep, dogs and other animals, but none is so
important as the Texas fever of cattle.

OTHER PROTOZOAN DISEASES

Spotted Fever. — Spotted fever, or Rocky Mountain fever,
is a disease that occurs in the mountains in the northwestern
United States. It is transmitted by ticks, Dermacentor ven-
ustus, and is supposed by many to be due to an organism closely
related to, or belonging to the genus Babesia. It has been
shown that domestic animals, particularly the larger ones,
in the region where the fever occurs, are the principal hosts
for the adult ticks, so if these animals can be kept free from
ticks, by dipping and otherwise, the disease can be largely
controlled.

Pebrine of Silkworms. —About the middle of the nine-
teenth century a strange malady appeared among the silk-
worms in Southern France and caused enormous losses. The
silk growers knew nothing of the nature of the disease, and were
at a loss to know how it spread, for even though they placed
the eggs of the silk-worm moth in perfectly clean places and
took the very best care of the larvae, the silk-worms would
suddenly sicken and die at a certain stage of their development.
Pasteur, who was then just beginning his great work, made a
careful study of the disease and discovered that it was caused
by a sporozoan. It was found that this parasite, now known
as Glugea (Nosema) bombycis, was so minute that it would
enter the eggs before they were laid by the moth, so that the
larvae were affected from the time they hatched, although the
disease did not manifest itself until a later stage in their devel-
opment. The disease is known as pebrine, and was the first
disease proved to be due to an infection by a Protozoan
parasite. In several countries where silk-worm growing is
an important industry, Government experts now examine all
the eggs that are used for hatching and only those that, by

PARASITIC PROTOZOA

365

microscopical examination, are shown to be free from the para-
site are sent to the growers.

Epidemics Among Fishes. — Sometimes in the United States,
and more frequently in Europe, destructive epidemics appear
among the fishes in lakes or rivers. Hundreds of thousands
of fish may die and be washed upon the shores and the particu-
lar species attacked may be almost exterminated in some
regions. The diseases responsible for these epidemics are
caused by various species of Myxosporida, which attack and
destroy the tissues of their hosts, often causing many serious
tumors over the body. Young fish are especially apt to suffer
from the attacks of these parasites.

DISEASES CAUSED BY INVISIBLE MICROORGANISMS

There are a number of diseases the causative agents of which
are not yet definitely known. Nevertheless it has been demon-

FIG. 155. — Stable-fly, Stomoxys calcitrans, after engorging itself
blood. (About three times natural size.)

with

strated that many of these are caused by living organisms,
probably too small to be seen by any microscopes that have
yet been invented. More refined microscopic methods may
sometime reveal some of these to us, and we may then be able
to determine their relation to other known forms.

That yellow fever is caused by such an organism has been
definitely shown, and although we do not know the parasite

366 ECONOMIC ZOOLOGY AND ENTOMOLOGY

we know much of its life-history, and certain investigators
do not hesitate to express their belief that it belongs to the
genus Spirochceta. Yellow fever is transmitted only by the
yellow fever mosquito.

Infantile paralysis, or poliomyelitis, is also caused by one
of these1 ultra-microscopic parasites, which can probably be
distributed, as recently indicated by experiments with mon-
keys, by the common stable-fly, Stomoxys calcitrans. The dis-
ease seems also to be directly contagious.

Cattle plague, canine distemper, swamp fever of horses, hog
cholera and several other diseases also belong to the group pro-
duced by invisible parasites. Some of them will probably
be found to be caused by animal parasites, others by bacteria.

1 It has recently been found to be visible in certain stages, although
invisible in others.

CHAPTER XXIX
INSECTS AND DISEASE

We have already learned (Chapter XXVIII) that insects are
the necessary hosts of the parasites that cause some of our worst
diseases, and that the spread of these diseases depends wholly
on the presence of the infected insects. It is only during the
present century that the very great importance that insects
thus bear to our health has been realized, and many of the most
important recent discoveries in medical science have had to do
with this relation of insects to some of the common scourges
that afflict man or his domestic animals.

Since it was shown beyond all doubt that malarial fevers
depend wholly on the presence of infected mosquitoes (page
361), successful efforts have been made to control these insects
in some of the places where the disease was most common.
As mosquitoes breed only in quiet water the problem of
control is not as great as it would at first appear to be, and there
is now no reason why almost any community should not rid
itself of these disease-bearing pests. In temperate regions
malaria is not as fatal as it is in the tropics where it is the cause
of one-fourth to one-half of all the sickness. Yet it has been
estimated that the annual monetary loss due to sickness from
malaria in the United States is many millions of dollars. The
suffering and misery, the loss of vitality of young and old,
and the death of twelve thousand persons each year, are results
of malaria the importance of which cannot, of course, be
stated in dollars and cents.

Almost every day there is an increase in the evidence that
shows how dangerous are such common and long tolerated
household pests as house-flies and their near relatives, the stable-
flies, flesh-flies and others. That these insects do aid in the
dissemination of certain of our germ-caused diseases, as typhoid

367

368 ECONOMIC ZOOLOGY AND ENTOMOLOGY

and tuberculosis, is sure. That they may aid in distributing
others is highly probable. Mosquitoes and house-flies will be
feared in the not far distant future as venomous snakes are
now. And they will be fought even more vigorously, for
their abundance makes them immensely more dangerous.

Life History and Habits of Mosquitoes. — Mosquitoes lay
their eggs in water, or in places where water is apt to accumu-
late. Some species fasten the eggs together in little masses
that float on the surface and look like small particles of soot at

\

FIG. 156. — Mosquito eggs and larvae, Theobaldia incidens; two larvae
feeding on bottom, others at surface to breathe. (Enlarged.)

first glance. Other species lay their eggs singly, some floating
about on the surface of the water, others sinking to the bot-
tom where they remain until the young issue. In the summer
time the eggs hatch in thirty-six to forty-eight hours. The
larvae, or "wrigglers," are fitted only for aquatic life, but they
must obtain their oxygen directly from the air and so have
to come to the surface to breathe. This is an important thing
to remember when considering means for their control. The
larvae of most mosquitoes have, on the eighth abdominal seg-

INSECTS AND DISEASE 369

ment, a rather long breathing tube, the tip of which is thrust
just above the surface of the water when they come up to
breathe. Other larvae do not have such a breathing tube, the
spiracles which open into the trachea being situated on the
surface of the eighth segment. The pupae of all species are
active but take no food. . The two trumpet-shaped breathing
tubes of the pupae are situated on the thorax, and when the
pupae come to rest these extend just above the surface of the
water. When the adult is ready to issue the pupal skin splits
along the back and the mosquito slowly comes forth, usually

FIG. 157. — Mosquito pupae, T. incidens, resting at the surface of the water.

(Enlarged.)

resting for a short time on the cast-off pupal skin until the wings
become dry and firm enough to use.

Malaria-carrying Mosquitoes. — In the United States only
mosquitoes belonging to the genus Anopheles carry malaria, so
it is important to be able to distinguish the members of this
genus in their various stages. The eggs of Anopheles are laid
singly, but are often found together in groups of three or four
floating on the surface of the water. Each egg is provided with
characteristic membranous expansions on each side near the
middle. These keep the eggs afloat. The larvae feed largely
on minute plants or other organisms at the surface of the water,
and when feeding lie nearly horizontally, with the body touch-
ing the surface at several points. The absence of a breathing
tube, and this habit of always lying with the body parallel to the
24

370 ECONOMIC ZOOLOGY AND ENTOMOLOGY

surface of the water when feeding or at rest, readily distinguish
these larvae from those of any of the non-Anopheline, or non-
malarial, mosquitoes. The pupae are, however, not so easy to
distinguish. The adults of Anopheles have spotted wings, a
character which only a few of our other mosquitoes have.
With most mosquitoes the maxillary palpi (see Fig. 159) of
the male are long and those of the female very short, but the

FIG. 158. — A female mosquito, T, incidens; note the thread-like antennae.
(Three times natural size.)

Anopheles mosquitoes have the palpi long in both sexes, so
any female mosquito with long maxillary palpi is an Ano-
pheles. The males of all mosquito species may be readily
distinguished from the females by the big feathery antennas.
The antennae of the female are provided with only a few hairs.
When an Anopheles mosquito is resting on the wall or ceiling,
its body is held at an angle with the surface on which it is stand-
ing, as shown in Fig. 163. Other mosquitoes rest with their

INSECTS AND DISEASE 37 1

bodies nearly parallel to the surface on which they are standing.
(Compare Figs. 162 and 163.)

FIG. 159. — A male mosquito, T. incident; note the feathery antennae
(Three times natural size.)

FIG. 160. — Anopheles larvae, the one to the right feeding. (Enlarged.)

Mosquito Control. — Mosquitoes, in all stages of their devel-
opment, have many natural enemies, most important of which
are fish and various aquatic insects that feed on the larvae

372 ECONOMIC ZOOLOGY AND ENTOMOLOGY

and pupae. But often the eggs are laid in water where none of
the natural enemies occurs, and they then breed undisturbed.

FIG. 161. — Wing of Anopheles maculipennis. (Eleven times natural size.)

FIG. 162. — A non-malarial FIG. 163. — A malarial mosquito,

mosquito, Theobaldia incident, Anopheles maculipennis, female,

male standing on the wall. standing on the wall. (About

(About twice natural size.) twice natural size.)

Such places require careful attention when fighting mosquitoes.
All water troughs and barrels or cisterns should be emptied

INSECTS AND DISEASE 373

frequently, or be kept covered so that the mosquitoes cannot
get to the water in them. All tin cans, or other scattered
receptacles that might hold a little water, should be removed or
placed so that water will not stand in them. Small ponds
should be drained or kept covered with a film of oil during the
summer time. Larger ponds are usually naturally stocked
with fish, predaceous insects and other enemies of mosquito
larvae and pupae, so that they are not a source of danger unless
the margins are filled with rushes or other strong plant growth.
Mosquitoes will not breed in running streams, but the quiet
pools along the sides may afford excellent breeding places,
particularly if they are cut off from the rest of the stream.
Many species breed abundantly in wet pastures or meadows,
and others abound in the brackish tide pools in the marshy
land along sea-coasts. Such marshes must be drained or
dyked so the water will not remain on them, or all the little
pools must be covered with oil if such regions are to be freed
from these pests.

Yellow Fever and Mosquitoes. — For many years the cause
and method of dissemination of yellow fever was a puzzle to
physicians and scientists. The disease was always regarded
as highly contagious as well as infectious, and every effort was
made to isolate patients and to establish strict quarantines in
infected regions. But all such methods proved unsatisfactory.
Many people became ill without ever having been near a yellow
fever patient, while others worked in daily contact with sick
persons yet did not take the disease.

During the American occupation of Cuba in 1900 yellow
fever became very prevalent there and a board of army
medical officers, known as the Yellow Fever Commission, was
appointed to study the disease and try to find some means to
control it. Some years previously a physician had suggested
that a certain species of mosquito, Stegomyia fasdala (calopus),
which was always found in regions where the yellow fever oc-
curred, might be concerned in the transmission of the disease.
The Yellow Fever Commission early decided to put this theory
to the test, and before their experiments had been finished it
was shown that yellow fever was transmitted by this mos-

374 ECONOMIC ZOOLOGY AND ENTOMOLOGY

quito and in no other way. Since that time many other ex-
periments have been made, and it is now definitely known how
this disease spreads through an infected region. The virus
that causes the fever occurs in the blood plasma of the human
host, but the yellow-fever patient is a source of infection for the
mosquito only during the first three or four days after the fever
manifests itself. The virus must undergo an incubation period
of twelve to fourteen days in the mosquito before she is capable
of transmitting the disease. After this incubation period the
mosquito is infective for the rest of her life. The parasite

FIG. 164. — Yellow-fever mosquito, Stegomyia fasciata. (About eight times
natural size.)

that causes the disease has never been seen, probably because
it is too small, but it is believed that it is one of the large group
of Sporozoan parasites.

One of the members of the Yellow Fever Commission died of
yellow fever during the course of the experiments, and another
member contracted the disease but recovered. The applica-
tion of the knowledge gained by these studies enabled the
officers soon to check the epidemic of yellow fever then existing
in Cuba. A few years later when the disease appeared in
virulent form in New Orleans it was stamped out in a re-
markably short time by waging a ceaseless war against the
mosquitoes. The Panama Canal Zone has long been regarded
as one of the worst regions in the world for yellow fever and
malaria. Since the United States began work on the Canal
persistent efforts have been made to control the mosquitoes
there. These efforts have been so successful that there has
been no yellow fever in the Canal Zone for several years, and
cases of malaria are comparatively rare.

INSECTS AND DISEASE 375

The yellow-fever mosquito is a domestic insect. It is seldom
found far from human habitation and for this reason can be
comparatively easily controlled, for if every possible breeding
place within a few hundred feet of every house was properly
cared for this mosquito would no longer be present.

Fleas and Plague. — Plague is a disease that for ages was
regarded as one of the greatest of human scourges, because
when once started in a region there seemed to be no way to stop
its ravages. But it, too, has been conquered within the last
decade by the discovery of the cause of the disease, and the
way -in which it is transmitted from one host to another.

Plague is primarily a disease of rats and other rodents, and it
is commonly spread by the fleas with* which these animals are
always infested. When a rat dies of the plague the fleas which
have been sucking its blood leave it for some other host. As
most of the rat-fleas will also bite man the infected fleas may
communicate the disease to him.

The disease is caused by the presence in the blood of a
bacillus, Bacillus pestis. There are several types of plague
distinguished by the way in which they affect the patient, and
they are probably spread in different ways. The bubonic
plague is the most common. It may occur as sporadic cases
among animals and be transferred from them to man by fleas.
Under favorable conditions this type may become epidemic.
Pneumonic and septicaemic plague are more virulent types, and
may be transmitted directly from man to man and probably
also conveyed by insects.

In the efforts to control the last outbreak of plague that
occurred in the United States the whole fight was directed
against the rats that had the disease and against the fleas that
carried the infection to man. Hundreds of thousands of rats
were killed, their breeding places destroyed, warehouses and
storerooms made rat-proof, covered garbage cans were required
in every yard, and many other measures were taken to make it
impossible for rats to exist in any great numbers in the infested
region. In this way there was stamped out in a remarkably
short time an epidemic which might at an earlier time have
proved a national calamity. In some places ground-squirrels

376 ECONOMIC ZOOLOGY AND ENTOMOLOGY

have become infected with the plague, and the Government is
now waging a war against them in order that the disease may
not be kept alive in them and again become epidemic among rats
and man.

There are four species of fleas occurring in the United States
that are commonly found on rats. Two of these are also
common pests of man, and the others do not hesitate to bite
man when they have a chance, so that all may transmit the
plague from diseased rats to human beings. The cat and dog-

FIG. 165. — Human-flea, Pulex, irritans ; female.

size.)

(Twenty times natural

flea, Ctenocephalus canis, is probably the most common of them.
It occurs in all places where cats and dogs are kept, and is often
more common in houses and a worse pest than the human-flea,
Pulex irritans, which is always a troublesome and persistent
biter. The common rat-flea of the United States, Ceratophyl-
lusfasciatus, and the Indian rat-flea, or plague-flea, Xenopsylla
(Lamopsylla) cheopus, are not so troublesome to man.
As fleas breed in the dust under the carpets, in the cracks of

INSECTS AND DISEASE 377

the floors, and in the sleeping places of cats and dogs, all these
places must be thoroughly cleaned when a house becomes
infested with fleas. Fleas are less apt to be troublesome in
houses where rugs are used instead of carpets, as the rugs are
more often taken outside for dusting and the floors more
thoroughly cleaned. Mats that can be easily cleaned should
be provided for the sleeping places of dogs and cats, and these
animals should of course be kept out of doors. Benzine,
naphthaline, pyrethrum and other substances are sometimes
used against fleas, but the results are not wholly satisfactory.
It is possible to kill all of the insects in the house by fumigation,
but fumigating is dangerous unless done by an experienced
person.

House-flies. — Until a few years ago the house-fly was looked
on as a harmless, although somewhat troublesome, household
pest, and was even regarded with some favor as it was sup-
posed that it was of service as a scavenger. But careful studies
of the insect and its habits have taught us to regard it in quite
a different light, and it is now regarded as one of the most
dangerous insects. It is hard to conceive of a better carrier of
small particles of filth and germs, or one with better opportuni-
ties for collecting and distributing them. Almost every part
of its body, and almost all of its habits, particularly adapt it
for the picking up and distribution of filth and germs. The
whole body is provided with a covering of spines and short soft
hair in which particles of dirt are easily carried. The blunt
end of the proboscis by which the fly sucks up its liquid food is
provided with numerous ridges and depressions so that some of
the material on which the fly is feeding is carried from one arti-
cle of food to another. The legs are particularly hairy, and the
last segment of each of the feet is furnished writh two little
pads which are covered with innumerable closely-set hairs that
secrete a sticky substance. It is the presence of these hairs on
its feet that enables the fly to walk on smooth perpendicular
surfaces, such as the windowpane, or on the ceiling, and, inci-
dentally, to carry along samples of the filth through which or
over which it walks.

Ninety-eight per cent, of the house-flies lay their eggs in horse

378 ECONOMIC ZOOLOGY AND ENTOMOLOGY

manure, the others breeding in cow manure, human excrement
or other filth. Each female lays from 120 to 150 eggs at a

FIG. 166. — The house-fly, Musca domestica. (Eight times natural size.)

time, and may lay five or six batches of these at intervals of a
few days. These eggs hatch in ten to twenty-four hours, and

INSECTS AND DISEASE

379

the whitish maggots feed and grow in the filth for three or four
days before changing to the quiescent pupal stage which lasts
four or five days longer. Then the adult fly issues. Some of
the filth through which the fly has to crawl as it issues from the
pupa inevitably clings to the little brush-like feet and the hairy
body. If the flies bred only in stable manure and flew directly
from the stable to the house there would be comparatively

FIG. 167.— Head of house-fly, showing eyes, antennae and mouth-parts.
(Much enlarged.)

little reason to complain, at least from a sanitary standpoint,
for the amount of filth they carry from the barnyard to our food
would be of little consequence. Too often, however, they visit
other places before calling on us, and, unfortunately, these other
places are often most unclean. Experiments have shown
that when the fly walks over germ-infected material many of

380 ECONOMIC ZOOLOGY AND ENTOMOLOGY

the germs are carried and distributed to other substances over
which it may walk, and that bacteria may live in the alimentary
canal of the fly and even increase in numbers there and remain
virulent in the excreta, or "fly specks," for as long as twenty
days after these specks have been deposited. It has been
shown also that larvae of flies may feed on bacteria and the
same organisms be recovered from the adult flies which develop

FIG. 1 68. — Foot of house-fly, showing claws, hairs, pulvilli and
minute clinging hairs on the pulvillas. (Greatly enlarged.)

the

from the larvae. All this indicates some of the possible ways in
which flies may carry filth or disease germs from their dangerous
breeding or feeding grounds directly to foods which may be
exposed in the market place, dairy, or home.

It has been proved beyond a doubt that flies play an impor-
tant part in the dissemination of typhoid germs, and it has
also been shown that they carry some of the germs that cause
the sickness and death of many babies, especially bottle-fed
babies. Time and again it has been noted that outbreaks of

INSECTS AND DISEASE

381

enteritis and other intestinal diseases occur during fly time, and
a moment's thought, in the light of our knowledge of the habits
of flies, will show how easy it is for the milk to become infected
around dairy barns or milk wagons where the flies are always
found in great numbers. It is quite possible, too, that flies
may sometimes be concerned in the transmission of the germs

FIG. 169. — Larvae and pupse of house-fly, Musca domestica, in manure.
(Natural size.)

that cause tuberculosis, influenza and other dreaded diseases.
Of course only a small proportion of the flies carry disease
germs, but they are all filthy, and it is impossible, without
careful laboratory analysis, to distinguish those which carry
disease from those which are merely dirty.

The only safe thing to do is to banish them all, not only from
the house and the market place, but from the storerooms and
dairies and all other places where food of any kind may be

382 ECONOMIC ZOOLOGY AND ENTOMOLOGY

exposed. Screens, sticky fly paper, fly poisons and fly traps
about the house will give some relief, but there is little use in
protecting the food after it has entered our homes if in the
stores or markets or dairies it has already been exposed to con-
tamination by thousands of flies that have visited it there.
The problem is a larger one than simply keeping the flies out of
our houses; larger but not more difficult, for the remedy is sim-
ple, effective and inexpensive. If the manure in which the
flies breed is hauled from the barn at least once a week and scat-
tered thinly over a field, it will dry so quickly that the flies will
not breed in it. If it is impracticable to scatter the manure at
once, it should be composted at least half a mile from any dwell-
ing. Most livery stables have the manure removed daily,
but few of them are careful to see that the bins or other places
where the manure is stacked before being hauled are thor-
oughly clean. Thus there is left in cracks or corners enough
manure to serve as breeding places for hundreds of thousands of
flies. Then, too, few stablemen take the care to clean the stalls
as thoroughly as they should, and many a one is surprised
when he finds that the flies are breeding abundantly in the stalls
which he considered sufficiently cleaned. Finally, after every
effort has been made to clean up the breeding places of flies,
our attention should be turned to trapping or poisoning the few
flies that may still appear. Many more or less efficient fly
traps are on the market, some of which, if properly baited,
do really good work. Fly papers are often quite effective, but
they are disgusting unless kept out of sight. A poison made by
adding one tablespoonful of formaldehyde to one-half a pint
of milk and water forms a very attractive bait and a deadly
poison for the flies. The best way to use it is to place a piece
of bread in a saucer and almost cover it with the poison,
milk and water.

The Stable-fly, or Biting House-fly. — This is another fly
that is commonly found in houses. It looks very much like the
common house-fly, and only a close observer will notice the
difference between the two. The most noticeable and impor-
tant difference is in the character of the mouth parts. The tip
of the proboscis of the house-fly is blunt and roughened, fitted

INSECTS AND DISEASE

383

for rasping and reducing to a liquid or semiliquid condition
the material upon which it feeds. The mouth parts of the
stable-fly, on the contrary, form a strong piercing beak which
can cut through even the toughest skin in order that the fly
may suck the blood of its victim. Persons are often bitten by
flies that they believe to be house-flies. But house-flies cannot
bite, and it will usually be found that the culprits are stable-

FIG. 170. — Stable-fly, Stomoxys calcitrans. Resembles house-fly in
general appearance, but has pointed, piercing and sucking beak, and the
vein which terminates near the tip of the wing is not so sharply angulated
as in the house-fly. (See Fig. 166.) (Five times natural size.)

flies. If the wings of a house-fly and a stable-fly be carefully
compared it will be seen that the fifth vein (counting from the
front margin) of the house-fly's wing is bent forward at a con-
siderable angle while the corresponding vein in the wing of
the stable-fly is only slightly curved. The fourth and fifth
veins are the two veins that end near the tip of the wing. In
the house-fly the tips of these veins are very close together; in
the stable-fly they are rather widely separated.

384 ECONOMIC ZOOLOGY AND ENTOMOLOGY

The stable-flies develop in much the same way, and under the
same conditions as the house-flies, but they are more apt to be
found in cow manure or old straw or other decaying vegeta-
tion, than in horse manure. The stable-fly also takes longer
to complete its development than does the house-fly, often
requiring three or four weeks to pass through the larval and
pupal stages.

Stable-flies are among the most serious pests of cattle and
horses, biting them severely and causing considerable swellings
in the places where they bite. They have recently been the
subject of particular study and investigation because they have
been suspected of being intimately connected with the dis-
tribution of that mysterious disease known as poliomyelitis,
or infantile paralysis. This disease, which has been slowly
spreading over America as well as most European countries, has
baffled the skill of physicians because they have been unable
to determine how it is transmitted. Experiments have been
made which show that stable-flies are capable of transmitting
the disease if they are allowed to bite first an infected and then a
healthy monkey. While this by no means proves that it
really spreads the disease among human beings, it yet adds
greatly to the evidence against this insect, so that the flies
should be destroyed whenever possible. The same measures
that are necessary for the control of the house-fly would aid
materially in controlling this insect also.

Other Diseases Carried by Insects. — There are many other
diseases that are known to be transmitted by insects. Sleep-

FIG. 171. — Filaria in the thorax, head and labium of a mosquito. (After
Castellan! and Chalmers.)

ing sickness and other diseases caused by trypanosomes and
carried by tsetse-flies have been discussed in Chapter XXVIII,
and in Chapter XII it has been shown how mosquitoes carry

INSECTS AND DISEASE 385

the filaria that cause elephantiasis. Mosquitoes are also prob-
ably responsible for the spread of dengue or break-bone fever.
We do not yet know the organism that causes the disease, but
experiments have shown that it can be spread by Culexfatigans,
and possibly by other species of mosquitoes.

For a long time the theory that pellagra is in some way asso-
ciated with the eating of maize has been generally accepted.
Recently Dr. Sambon has suggested that pellagra may be
caused by some organism that is transmitted by certain small
black flies belonging to the family Simulida. This theory is
not yet firmly established and there are many who do not
accept it at all. The investigations that are now being carried
on will doubtless soon settle the question. The black-flies are
very serious pests of live stock and their habits are discussed
in Chapter XXX. The stable-fly has also been considered
as a possible agent in the transmission of pellegra.

Certain little moth-like flies, Phlebotomus pappataci, which
on account of their habits are sometimes called "sand-flies,"
carry an unknown germ that causes a very infectious disease
known as three-day fever, or sand-fly fever. But as this and
several other diseases of lesser importance spread by insects, do
not occur in our country we need not discuss them.

The relation of ticks to several important diseases has already
been discussed in Chapters XIX and XXVIII.

CHAPTER XXX

OTHER INSECTS AFFECTING MAN AND DOMESTIC
ANIMALS

Besides the mosquitoes, house-flies and fleas, there are
several other insects that affect man and his domestic animals
more or less seriously. The habits of some of these make it
quite possible for them to carry infection from one host to
another under favorable conditions. So aside from the annoy-
ance and suffering they may
cause they must always be re-
garded as potential sources of
greater danger.

Flies. — Among such trouble-
some and dangerous insects

• FIG. 172. — A black-fly,
Simulium sp. (About 6
times natural size.)

FIG. 173. — Horse-fly, Tabanns
punctifer. (A little larger than
natural size.)

various kinds of flies are perhaps most important. The little
"punkies, " or " no-see- urns," Ceratopogon spp., that often
occur in great swarms in certain regions, bite very severely and
are extremely annoying to man and beast. The black-flies, or
buffalo-gnats, Simulium spp., also fly in great swarms and
inflict very painful bites. The lancet-shaped stylets of the

386

INSECTS AFFECTING MAN AND ANIMALS 387

mouth-parts make a wound into which is injected poison from
the salivary glands. Animals are driven frantic by the
attacks of these pests and may even suffer death unless they are
afforded some protection. Considerable losses are occasioned
each year because of farmers not being able to work animals
in the fields during the season that these insects are flying.
The possible relation of these flies to pellagra has been referred
to in the preceding chapter.

The larvae of the black-flies are aquatic, attaching themselves
to the surface of rocks in swiftly moving streams. It is
difficult to fight them there, but some small streams may be
cleared of their breeding places, or the water may be treated

FIG. 174. — Screw-worm fly, Chrysomyia macellaria. (Three times natural

size.)

with phinotis oil and many of the larvae destroyed without
injuring the fish in the stream. Dense smudges will keep the
adults away, and some protection may be afforded animals by
smearing them with cotton-seed oil or oil and tar.

The horse-flies, gad-flies, breeze-flies and deer-flies, all be-
longing to the family Tabanidce, can pierce through the toughest
skin and are often a source of great annoyance to live stock.
Some of them often attack man also. Cattle and horses
sprayed with some crude oil emulsion are not attacked as
freely as unsprayed animals. Laurel oil has recently been
recommended as a fly repellent.

Horn-flies, Hamatobia serrata, and the stable-fly, Stomoxys
calcitrans, are among the most serious pests of cattle. Means
for controlling the latter have been suggested in the previous

388 ECONOMIC ZOOLOGY AND ENTOMOLOGY

chapter, but it is harder to control the horn-fly because it
breeds in the cow manure all over the pasture. Various
repellent washes are recommended for use, but none is wholly
satisfactory.

The screw-worm flies, Chrysomyia macellaria, often cause
great suffering on account of the habits of the larvae. These
gray-flies, as they are sometimes called, may lay a mass of three
or four hundred eggs on the surface of wounds on cattle,
horses, etc. The larvae which hatch from these eggs in a few
hours make their way into the wound and feed on the surround-
ing tissue. Slight scratches that might otherwise quickly heal

FIG. 175. — Blow-fly, Calliphora vomitoria. (Two and one-half times

natural size.)

often become serious sores on account of the presence of these
larvae. Many cases are on record of these flies laying their
eggs in the ears or nose of children or of persons sleeping out of
doors during the day. The larvae, burrowing in the mucous
membrane, cause terrible suffering and often death.

The blow-flies, Calliphora vomitoria, the blue-bottle flies,
Lucilia spp., and the flesh-flies, Sarcophaga spp., all have
habits somewhat like those of the screw-worm flies. The
flesh-fly, instead of laying eggs, deposits living larvae upon
meat wherever it is accessible, and as these larvae grow with

INSECTS AFFECTING MAN AND ANIMALS 389

astonishing rapidity they are able to consume large quantities
of flesh in a remarkably short time. In this way they may be
of some importance as scavengers.

The bot-flies, family Oestrida, are another group of flies that
are a great source of annoyance, and often loss, to the stock-
man. Rarely, too, the larvae of some of them may infest man.
The adult flies look much like small hairy bumble-bees. The
mouth- parts are rudimentary so they cannot bite, yet many
animals have an instinctive fear of them and will do every-
thing that they can to get away from the pests. The common
bot-fly of the horse, Gastrophilus equi, attaches its eggs to the

FIG. 176. — Horse bot-fly, Gastrophilus equi. (Two and one-half times
natural size.)

hair of the legs or some other part of the body of the animal.
The horse licks off the eggs into its mouth. The eggs hatch
just before or after they are licked off and the larvae develop
in the alimentary canal of their host. Sometimes the walls of the
stomach may be almost covered with the larvae that have at-
tached themselves there. This of course seriously interferes
with the function of this organ. When full grown, the larvae
pass from the horse with the droppings, and complete their
transformations in the ground. There are two other species of
bot-flies attacking the horses. These have habits similar, in
most respects, to the species just described.

3QO ECONOMIC ZOOLOGY AND ENTOMOLOGY

It is believed that the bot-flies of cattle, or the ox-warbles,
Hypoderma lineata, and //. bows, gain an entrance into the ali-
mentary canal in the same way, that is by being licked from the

FIG. 177. — Bots, larvae of Gastrophilus equi, in stomach of horse.

(Enlarged.)
i

hairs on the body where the eggs have been laid by the adult
•fly. But instead of passing on into the stomach they penetrate

FIG. 178. — Ox warble-fly, Hypoderma lineata. (About two and one-half
times natural size.)

the Walls of the esophagus and later make their way through the
tissues of the body, until at last they reach a place along the
back just under the skin. Here, while completing their

INSECTS AFFECTING MAN AND ANIMALS 391

development, they make more or less serious sores. When fully
mature their larvae drop to the ground and undergo their trans-
formation to pupae and finally to flies. Some entomologists
believe, however, that the eggs are laid on the backs of the
cattle and that the larvae bore through the skin to the place where
they are to complete their larval development. Although this is
one of the most common pests of cattle this question in regard
to its life-history has never been definitely settled. The sheep
bot-flies, Oestrus ovis, lay their eggs in the nostrils of sheep.
The larvae pass up into the frontal sinuses, where they feed on
the mucus and tissues, causing great suffering and loss. Many

FIG. 1 79. — Bot, larva of Hypoderma lineata, from cow. j (Enlarged.)

other species of animals are infested by their own particular
species of bots. Several instances are recorded where the ox-,
warbles have occurred in man, always causing much suffering
and sometimes death.

Horses and cattle that can rest in the shade during the hot-
test part of the day are not bothered as much by bot-flies as
are animals that do not have such protection. Cattle often
obtain further protection by standing in the water when it is
available. Horses that are thoroughly groomed and kept
free from the eggs of the bot-flies will not, of course, be infested
with the larvae. After they have gained an entrance little
can be done to cause the larvae to leave the alimentary canal
of the host until they are fully developed. The ox-warbles

392 ECONOMIC ZOOLOGY AND ENTOMOLOGY

are much more serious pests, but fortunately they can be
controlled by concerted action on the part of all of the stock
owners in a community. After the larvae have attained con-
siderable size they are easily detected as they lie under the
skin on the backs of the cattle. When they are nearly ready
to issue they can easily be squeezed out and destroyed. They

FIG. 180. — Body-louse, Pediculus vestimenti. (About eighteen times
natural size.)

may also be killed while still under the skin, but bad sores are
apt to result if this is done so it is much better to squeeze them
out. If all of the cattle owners in a community attend to this
early each spring, it is evident that the number of bot-flies
will soon be so reduced that they will cause little trouble.

Lice. — There are two distinct groups of wingless parasitic
insects commonly called lice. One group, the blood-sucking
lice, belongs to the family Pediculidce, order Hemiptera; the
other, the biting lice, constitutes an independent small order, the

INSECTS AFFECTING MAN AND ANIMALS 393

Mallophaga. The Pediculidce are confined to mammals, the
three species found on man and a few that infest domestic ani-
mals being the best known. The mouth parts are fused to form
a flexible sucking tube, and the feet are provided with a single
strong curved claw which enables them to cling to the hair of
their host. The head-louse, Pediculus capitis, is very annoying
on account of the intense itching caused by the bite. The
eggs, called "nits," are attached to hairs, and are very hard

FIG. 181. — The sucking louse of the horse, Hamate pinus asini. (About
twenty times natural size.)

to remove. These lice are never common where clean-
liness is the rule, but under certain conditions they may
be met with. Thorough combing and washing followed
by an application of pomade, vaseline or some such greasy
substance wTill get rid of the pest. The body lice, P.
•vestimenti, known as "graybacks," "crumbs," "seam-squir-
rels," live on the body and hide among the clothing.
They sometimes become very serious pests where the
surroundings are not sanitary, but can be controlled by

394 ECONOMIC ZOOLOGY AND ENTOMOLOGY

cleanliness. Infested clothes that may contain some of the
eggs should be boiled or steamed, or the inside of the seams
smeared with mercurial ointment. The crab-louse, Pthirius
inguinalis, lives on the hairs on protected parts of the body.
Sulphur and mercurial ointment are ths remedies used.

FIG. 182. — A chicken-louse, Menopon pallidum. (Greatly enlarged.)

Most of the sucking lice on domestic animals belong to the
genus Hcematopinus. Dogs, horses, cattle, sheep, hogs and
other animals are infested with species peculiar to themselves.
The animals may be freed from these pests by washing

INSECTS AFFECTING MAN AND ANIMALS 395

thoroughly with tobacco water, or dilute carbolic acid, or dilute
kerosene emulsion. Ointments made of kerosene and lard,
or sulphur one part and lard four parts, are effective. It is
possible to fumigate an animal by inclosing all but the head in
a sack or tent and burning sulphur or tobacco inside the tent.

The Mallophaga do not suck blood, but feed on bits of dry
feathers or hair which they bite off with their small sharp jaws.
They are commonly called bird-lice, because most of them
infest birds, but some species are found on mammals where
they feed on the hair or epidermal scales. The injury done to
the host is due chiefly to the irritation caused by the insects
wandering over the body. They sometimes occur in such
numbers as seriously to affect barnyard fowls. The common
chicken-louse, Menopon pallidum, is about one- twentieth of
'an inch long and is an unusually swift and active little pest.
The affected fowls make an effort to rid themselves of the pest
by bathing in fine dust. Good dust baths should always be
available for this purpose, and the roosts should be kept clean.
Badly infected poultry houses should be sprayed with kerosene
or fumigated by burning sulphur in them, and then thoroughly
whitewashed. •

Dogs, horses or other domestic animals infected with biting
lice may be treated as recommended for sucking lice.

Bedbugs — Although bedbugs, Acanthia lectularia, usually
occur only in neglected houses, they may be accidentally in-
troduced into the cleanest places, and they are often met with
in hotels. They cannot fly, as they have no wings, but they are
active crawlers and may migrate from house to house when food
becomes scarce. They are more commonly distributed on
clothing, especially bed clothing and upholstered furniture.
When crushed they give off a very disagreeable odor which is
due to the secretions from glands at the base of the abdomen.
They are nocturnal in their habits, hiding away in cracks in
bedsteads or other furniture or in the walls during the day.
Their very flat soft bodies are capable of being squeezed into
seemingly impossible places. The mouth-parts are fitted for
piercing and sucking blood. Normally they feed only on blood,,

396 ECONOMIC ZOOLOGY AND ENTOMOLOGY

but they may possibly subsist for a time on moisture in wood
or dust.

The bite is very irritating to most people, but no poison is
secreted. The recurrent fever of Europe isprobably transmitted
by bedbugs, and it is quite possible that other diseases also
may be carried by this unclean pest. Recent experiments have
indicated that it may prove to be one of the agents in the
spread of the bacillus that causes leprosy.

FIG. 183. — Bedbug, Acanthia lectularia. (About six times natural size.)

The simplest way to get rid of bedbugs is to clean all the
furniture and woodwork thoroughly. Carpets and rugs should
be removed, and every crack and crevice in furniture, picture
frames, walls and floors should be given a liberal treatment
with gasoline. Corrosive sublimate (bichloride of mercury)
in water or alcohol may be used for the same purpose, but it is
more expensive than gasoline and more apt to injure some
articles. As the water or alcohol evaporates a thin coating of
the powder is left that gives a large measure of protection as
long as it lasts. Fumigation with hydrocyanic gas is more satis-
factory, but this gas should be used only by some experienced

INSECTS AFFECTING MAN AND ANIMALS 397

person who is well aware of the danger attending its use.

Bedbugs are sometimes found in poultry houses where they
may be very annoying. The closely related bugs often found
so abundantly in swallows' nests and in other places out of
doors do not become household pests.

Cockroaches. — Like the bedbugs, the cockroaches are night
foragers. But they are much less particular about the kind of
food that they eat. Their mouth-parts are fitted for biting.
Kitchens, pantries, restaurants, hotels and bakeshops where the
air is warm and humid, are their favorite haunts, and almost
any kind of organic matter that can
be found around such places suits
their taste.

There are four common species
found in dwellings in this country,
only one of which is native. The
American roach, Periplaneta americana,
is the largest of these. It is light
brown in color and about one and one-
half inches long. The Australian
roach, P. australasia, is nearly as large
as the preceding species, but is darker
in color. The Asiatic roach, P. orien-
talis, or black beetle, as it is some-
times called, is about one inch long,
and brownish black in color. The
wings of the female are rudimentary,

and in the male the wings do not reach to the tip of the
abdomen. The most abundant and destructive of the group
in many parts of the United States is the little, yellowish-
brown, German cockroach, Ectobia germanica, which is only
about half an inch long. It is often caUed croton-bug because
of its intimate association with the pipes of New York City's
Croton water system.

The eggs of cockroaches are laid in small, purse-like, horny,
brown cases which are usually carried about by the female
until the young are ready to issue. It probably takes about a
year for the young to become fully developed.

FIG. 184. — The croton-
bug, or German cock-
roach, Ectobia germanica.
(Twice natural size.)

398 ECONOMIC ZOOLOGY AND ENTOMOLOGY

Although the actual damage done by these insects is not
often very great, they are, on account of their unpleasant odor
and their habit of crawling into everything, most disgusting
creatures to have about the house. It is suspected that they
may be concerned in the transmission of certain diseases by
contaminating food. Fumigation with hydrocyanic gas is
the best remedy to use when this is practicable. There are
many roach powders on the market, but few of them are
wholly satisfactory. Indeed it is usually only by a combina-
tion of several methods of fighting, such as poisoning, trap-
ping and sealing up their hiding places, that one can hope to
control the roaches in a badly infested house, unless fumiga-
tion is resorted to. All the cracks and crevices where the
roaches hide should be filled if possible; when this cannot be
done such places should be thoroughly syringed with a solution
of bichloride of mercury. Sweet chocolate or sugar and pow-
dered borax thoroughly ground together make a very good
poison. It is most readily eaten from pieces of slightly
moistened bread. Phosphorous paste makes a good poison
when spread on moist bread. Many roaches may be trapped
by placing food or some other attractive article in the bot-
tom of a deep vessel and arranging sticks or papers so the in-
sects can easily crawl from the floor to the edge of the vessel.
The sides of the vessel should be steep enough so the roaches
cannot crawl out after they have entered it.

Ants. — In the southern states a few of the common ants
may become of some importance in the field or garden on ac-
count of their habit of making large bare areas around their
nests or because they strip the foliage from plants. The
introduced Argentine ants, Iridomyrmex humilis, are the
worst of these, as they do considerable damage to citrus and
other trees by destroying the opening blossoms or the very
young fruit. In badly infested regions almost all kinds of
flowers are attacked. All kinds of stored food products may
be infested by these ants and the loss in store rooms from this
source is often important. But it is as household pests that
ants are of primary interest. One little red species, Mono-
morium pharaonis, makes its home in houses, building nests

INSECTS AFFECTING MAN AND ANIMALS 399

between the walls, under the hearthstones, or in other suitable
places. The small black ant, M. minimum, the pavement-ant,
Tetramorium ccespitum, of many eastern cities, and other
species which have their nests out of doors, frequently invade
houses and cause great annoyance by getting into all kinds
of food. As in the field so in the houses the Argentine ant is
by far the most important in regions where it occurs. Indeed
in places where this introduced species is well established the
other species disappear, for the intruder attacks and finally
overcomes, by sheer force of numbers, all other kinds of ants.

Nearly all ants live in large colonies in a common nest, but
the Argentine ants build small nests or burrows anywhere
throughout the infested region. Not only are the Argentine
ants more numerous than other
species, but they are more per-
sistent in their search for food,
and methods that usually afford
protection from other ants are
of little or no avail against
this introduced marauder.

The best way to get rid of FIG. 185. — Argentine ant, In-
most ants is to find the nest and fjjjjj^ humilis- (Much en'
treat it with carbon bisulphide,

pouring a few ounces of the liquid in holes made in the
nest and immediately stopping up the holes so the gas will be
forced throughout the nest. Colonies of the house ants may
often be treated with gasoline or boiling water. Dilute car-
bolic acid injected into the crevices through which the ants
enter a room will sometimes drive them away. Oil of lemon
diluted with alcohol will serve the same purpose for some
species. When it is impossible to destroy the nests, many
of the ants may be trapped by putting out scraps of attrac-
tive food or sponges wet with sweet syrup. The persis-
tent use of such traps will usually give relief from the
pests if the baits are removed as soon as they are covered
with the ants. Powdered borax spread around the thres-
hold or other places where the ants enter will act as a re-
pellent. Wood or cloth that has been treated with a

400 ECONOMIC ZOOLOGY AND ENTOMOLOGY

saturated solution of corrosive sublimate will repel the ants
as long as the poison remains. ''Ant tape" is made by soak-
ing ordinary cotton tape in a saturated solution of corrosive
sublimate. After the tape is dry it may be fastened around
table legs, on the edges of shelves or in other places. The
ants will not cross the tape as long as the poison remains on
it. It may thus afford protection for several months if kept
dry. As corrosive sublimate is very poisonous it must not be
used where children can reach it, and care must be taken to
wash the hands thoroughly after handling it. It has been
found that the most successful way to control the Argentine ant
is to place a number of sponges that have been soaked in a
weak solution of arsenic in convenient places about the yard
or in the houses. A gallon of this poison may be prepared

by mixing one-third of an ounce
of arsenite of soda in a syrup
that has been made by dissolv-
ing six pounds of sugar in a
gallon of water. This poison
acts very slowly and is carried
to the nest by the workers and
fed to the queen and the young
so that the whole colony may be
exterminated or driven away in
a few weeks. The same remedy
may prove effective in fighting
other species.

Clothes -moths. — There are two common species of small
moths whose larvae attack woolen fabrics, furs and feathers.
The case-making clothes-moth, Tinea pellionella, is very com-
mon, particularly in the North. The wings expand about
half an inch, the forewings are grayish yellow with indistinct
fuscous spots, and the hind wings are grayish. The eggs are
laid on or near the articles upon which the larvae are to feed.
As soon as they hatch the larvae begin to construct little cases
or covers out of bits of the material on which they are feeding.
This case is enlarged from time to time as the insect grows.
There may be two or more generations in warm places.

FIG. 1 86.— The clothes-moth,
Tinea pellionella; larva, larva in
case, and adult. (Twice natu-
ral size; after Howard and
Marlatt.)

INSECTS AFFECTING MAN AND ANIMALS 401

The webbing, or southern clothes-moth, Tineola biselliella,
is more abundant in southern latitudes. It is about the same
size as the preceding species, and the fore wings are uniformly
pale ochreous without any markings. The larvae feed on al-
most any kind of dry animal tissue, but are especially de-
structive to woolens, furs, feathers and hair. They construct
no case, but spin a cobwebby path wherever they go and when
ready to pupate make silken cocoons.

Clothing in continuous use or carpets or hangings that are
frequently aired and dusted, are not troubled by these insects.
The woolen clothes, furs, etc., that are stored away for the
summer, and carpets or upholstered furniture that do not
receive regular and thorough cleanings suffer most. If woolens
and furs are well dusted and allowed to hang in the sun for a
few hours, and are then packed in tight paper boxes or wrapped
carefully in linen they will not be bothered by the moths.
Carpets are apt to become infested
along the edges or under heavy furni-
ture that is seldom moved. A liberal
use of gasoline over the infested areas
will kill the larvae that are feeding
there. Napthaline flakes or "moth
balls" act as repellants for the moths,
but do not kill the larvae. The insects FIG. 187.— Carpet-
do not breed in temperatures lower beetle, or "buffalo-
than 40° F., and valuable goods are j$^ b£'*.3
often placed in cold storage when it is adult. (After Howard

necessary to pack them away for some an,d Marlatt; much

J enlarged.)

time.

Carpet-beetles.— The carpet-beetles, Anthrenus scroph-
ularice, or "buffalo-moths," as the larvae are sometimes called,
feed on carpets and sometimes on other woolen goods that are
packed away. The adults are small, broadly oval, black
beetles that are covered with minute black and grayish scales
which give the insect a mottled appearance. The larvae
have habits somewhat like those of the clothes moth larvae,
and may be controlled by the same treatment.

Some of the insects that attack flour, meal and other grain
26

402 ECONOMIC ZOOLOGY AND ENTOMOLOGY

products are discussed in Chapter XXXVI. Absolute cleanli-
ness will usually keep the kitchen and pantry free from these
pests. No open, partially-used packages should be left for
breeding places for these insects.

CHAPTER XXXI
CONTROLLING INSECT PESTS

The next nine chapters will be devoted to a consideration of
the very important relations that the insects bear to our
material welfare, in their capacity as pests of our crops,
orchards and forests. It is estimated that the annual money
loss occasioned by insects in the United States is approximately
as follows:

Cereals $300,000,000

Hay and forage 66,500,000

Cotton 85,000,000

Tobacco 10,000,000

Truck crops 60,000,000

Sugars 9,500,000

Fruits 60,000,000

Farm forests 11,000,000

Miscellaneous crops 10,000,000

Animal products 300,000,000

Natural forests and forest products 100,000,000

Products in storage 200,000,000

$1,212,000,000

This summary takes into account only those insects which
directly affect our crops or other products. We might well add
to this something of the financial loss caused by those insects
already discussed, that affect man himself, but this is a much
more difficult problem. It has been estimated, for instance,
that we pay more than $10,000,000 a year for screens for our
houses to protect us from mosquitoes and flies, and yet this af-
fords us only a small measure of protection. Such an amount
is comparatively insignficant when compared to the reduced
value in real estate because of the mosquitoes that infest
many regions making them almost uninhabitable, or to the

403

4o4 ECONOMIC ZOOLOGY AND ENTOMOLOGY

tremendous financial loss resulting from the quarantine and
suspension of business which, until recent years, always fol-
lowed an outbreak of yellow fever in any region.

Again we might consider the great loss of time and energy
that is occasioned by malaria in many regions. A man's
producing capacity may be reduced 50 to 75 per cent, for a
number of years because of this disease. This, of course, most
seriously retards the development of the malarial regions,
regions that might otherwise be producing millions of dollars
where they now produce only hundreds of thousands. It is
not conceivable that we can make any estimate in dollars
and cents of the great bodily and mental suffering entailed
as a result of some of the diseases that are carried by insects
and of the hundreds of thousands of deaths that occur annually
from these diseases. Yet these are by far the most important
factors to be considered in estimating the economic importance
of insects, and the work that is being done along the line of con-
trolling the insects that carry disease germs is the work that
most demands the co-operation and support of every citizen.

In no country in the world are the forces that are fighting
insect pests so well organized as they are in the United States.
The federal government maintains a large and very effective
Bureau of Entomology employing more than one hundred
men most of whom devote their whole time to the study of the
insect pests and methods of controlling them. Nearly all
states have their State Entomologists, who may or may not be
connected with the state agricultural colleges and experiment
stations, and many other horticultural officers and inspectors
who devote a large part of their time to the study and control
of insects.

We cannot fight insects successfully without some knowl-
edge of their structure and habits and life-history. More
than this, we must know something of their relation to other
insects and other animals. So the study of economic
entomology includes attention to systematic and morphologic
and ecologic entomology. It is a much more comprehensive
study than it is perhaps popularly supposed to be.

Government entomologists really devote a large part of

CONTROLLING INSECT PESTS 405

their time to the study of the general biology of insects, and
many of their bulletins and special reports are scientific papers
of much value to naturalists, as well as to the general public,
for whom they are primarily issued. Directions for obtaining
these bulletins and reports are given on page 419.

Sometimes the fight against an insect pest can be carried on
successfully by one man in his own orchard or field, but more
often the whole community must co-operate if lasting benefits
are to be secured, because most of the insects so readily pass
from one place to another. The necessity for such co-opera-
tion is well illustrated in the fight against flies and mosquitoes.
One unclean stable, where the manure is left for a breeding place
for flies, may be a source of annoyance and danger to all the
homes in the community. For a successful campaign against
house-flies, all the members of the community must see to it
that there are no manure piles, open privy vaults, open garbage
cans or other places where the flies may breed and feed, while
a united effort should be made to trap and kill as many of the
adult flies as possible. Some mosquitoes, such as the yellow-
fever mosquito and others, breed only near houses and fly but
a short distance. In such instances a "single person may free
his house from these pests by seeing that the mosquitoes
find no breeding places near. But many kinds of mosquitoes
fly for considerable distances, and the problem of their control
then becomes one for the community as a whole to deal with.

NATURAL ENEMIES OF INSECTS

Insects have many natural enemies which in many ways help
to control the injurious species. Indeed, were it not for this
condition many of them would increase so rapidly that they
would be wholly beyond the control of man. It is a significant
fact that with all our improved methods for fighting insects the
total amount of damage that they do to our crops is increasing
rather than decreasing. This is due in part to the introduction
of new pests, and in part to the more extensive and intensive
cultivation of crops. But the fact that we are changing the
natural conditions of vast areas and often destroying many of

4o6 ECONOMIC ZOOLOGY AND ENTOMOLOGY

the natural enemies of some of the insects, and thus upsetting
the balance that had been established in nature, is accountable
for a large measure of this increase.

The part that birds play in the control of the insect pests of
forest, orchard, garden and field is of much more importance
than is usually realized. Many species of birds feed chiefly
upon insects. From an examination of the stomach contents

FIG. 1 88. — Phoebe, a well known flycatcher, 90 per cent, of whose food
consists of insects.

of large numbers of birds it has been estimated that insects
form about 96 per cent, of the food of flycatchers in some
regions, 95 percent, of the food of wrens, 94 per cent, of warblers,
65 per cent, of woodpeckers and meadow-larks, and more than
25 per cent, of the native sparrows. Swifts, swallows, titmice,
crows, jays, blackbirds and many others feed largely on in-
sects. As many as 3000 to 5000 insects have been taken from
the stomach of a single bird. Of course many beneficial insects
are eaten with the injurious ones, and some of the birds also
take toll of fruit in the orchard or grain in the field but with

CONTROLLING INSECT PESTS

407

the notable exception of the introduced English sparrow and
of the few species of native sap-suckers, and two kinds of
hawks, practically all of our birds are to be regarded as friends
and helpers on the farm or in the orchard.

The common garden toads eat many insects and worms
during the evenings while they are feeding. Spiders trap and
destroy many of the smaller insects and are especially
serviceable on small flowering bushes and garden plants.

But it is to the insects them-
selves that we must look for some
of the most destructive enemies
of others of their class. It will
be convenient in considering
these to divide them into two
groups; first the predaceous in-
sects, which run or fly about
attacking and devouring other
insect species, and, second, the
parasitic insects, which spend a
part or all of their lives in or on
the body of their hosts.

Among the predaceous insects
the ladybird-beetles are per-
haps the most important, as in both the adult and larval
stages they destroy great numbers of plant-lice, scale-insects
and other noxious insects. A remarkable example of the good
that they may do is furnished by the Australian ladybird-
beetle, Novius cardinalis, that was introduced. into California
to aid in controlling the cottony-cushion scale, Icerya purchasi,
a pest that threatened the destruction of the citrus fruit in-
dustry in California. So rapidly did the beetles multiply
and so effectively did they do their work that the scale was
soon under control and is no longer regarded as a serious pest.
Many other species of ladybird-beetles have been introduced
into this country, but none has been so successful in its work as
this one.

Many of our native species of ladybird-beetles are par-
ticularly destructive to certain kinds of aphis and scale-insects.

FIG. 189. — A ladybird-beetle,
Coccinella calif arnica; larva,
pupae, and adult on Lawson's
cypress. (Twice natural size.)

408 ECONOMIC ZOOLOGY AND ENTOMOLOGY

In California millions of living ladybird-beetles are gathered
each winter, while hibernating in great masses in the high
Sierras, and as soon as the aphids begin to appear in destructive
numbers in the melon fields and other places large shipments of
the beetles are sent to the infested regions.

The larvae of the lace-winged-flies and the syrphus-flies are
also great enemies of aphis and other soft-bodied insects.
The predaceous ground-beetles (family Carabida) and the
tiger-beetles (family Cincindelidce) destroy many larva? and

FIG. 190. — The fluted scale, I eery a purchasi, attacked by the Australian
ladybird-beetle, Novius cardinalis. In .the lower left-hand corner, a
Novius which has just issued from its pupal case. (Upper figure slightly
enlarged; lower figure much enlarged.)

adult insects that can be captured on the ground. The
assassin-bugs (family Reduviida) are all predaceous, as are
several other kinds of Hemiptera, We have already called
attention to the importance of dragon-flies in controlling
mosquitoes.

Among the parasitic insects the tachina-flies (family
Tachinida) rank high as enemies of variouskinds of caterpillars.
The eggs are usually laid on the body of the insect into which
the young make their way as soon as they are hatched. Here
they feed, often without destroying the host until it pupates.
Sometimes the eggs of the tachina-flies are laid on the leaves,

CONTROLLING INSECT PESTS

409

and leaf-feeding larvae take the eggs into their alimentary canal
where they hatch. The parasites then bore their way into the

FIG. 191. — -A preda-
ceous g r o u n d-b e e 1 1 e,
Calosoma sycophanta.
(Natural size.)

FIG. 192. — A tachina-fly,
Blepharipeza adusta, the larva
of which is an internal para-
site. (About twice natural
size.)

body tissues of the host. The parasitic Hymenoptera, which
include some of the best known and most important of the
parasites and which comprise hundreds of different kinds,

.

^/^4|^u

FIG. 193. — Braconid cocoons on a caterpillar that has been killed by the
parasites. (About natural size.)

each attacking its own particular single or few host kinds,
have been discussed in Chapter XVII.

4io ECONOMIC ZOOLOGY AND ENTOMOLOGY

The most extensive experiment in attempting to control a
serious insect pest by its insect enemies is the work that is now

FIG. 194. FIG. 195.

FIG. 194. — Aphids on a leaf, which have been parasitized by a Braconid
parasite. (About natural size.)

FIG. 195. — Larvas and pupae of the oak tree moth, Phryganidia califor-
nica, that have been killed by a disease caused by bacteria. (Natural
size.)

being carried on by the Bureau of Entomology in the fight
against the gipsy-moth in the New England states. The way

CONTROLLING INSECT PESTS 411

in which this insect was introduced and the damage that it does
is referred to on page 507. Trained entomologists have been
sent to every foreign land where the gipsy-moth is known to
occur, and they have gathered and sent to this country all of
the different insect enemies of the pest that they could dis-
cover. Some of these have proved to be of no effect in our coun-
try, others aid a little, and still others give promise of being
important factors in the control of the moth. Those in charge
of the work do not expect to be able to find any one insect that
will do for the gipsy-moth what the Australian ladybird-
beetle did for the cottony-cushion scale, but they do expect that
if they introduce a great many parasitic and predaceous kinds
enough of them may work together to check the slow spread of
the pest and finally control it.

Insects are often attacked by fungi and by certain bacterial
diseases. Sometimes these are very important factors in con-
trolling outbreaks of chinch-bugs, scale-insects, grasshoppers,
various larvae and other insects. But the conditions which
favor the development of the fungi or bacteria are often beyond
our control, and usually there is but little that we can do to
aid in the spread of these diseases.

PREVENTIVE METHODS OF CONTROL

The natural enemies of insects do much, indeed, toward
controlling their numbers, but some of the worst pests require
the constant attention of the farmer or orchardist or he soon
sees his crops badly injured or totally destroyed. We can
never hope to get rid entirely of some of the pests, but by careful
management they may be kept in check so that they may not
reap the lion's share of the harvest. The most important
thing in dealing with insects is to begin early. Too often when
a pest makes its appearance the orchardist waits for a more
convenient season to commence fighting it. Meantime the
insect has had a chance to lay its eggs or, perhaps, to produce
several generations thus increasing many fold the number that
must now be fought. Until one understands how very rapidly
many insects multiply one can hardly realize the importance of
trying to get rid of a pest just as soon as it is found in the

4i2 ECONOMIC ZOOLOGY AND ENTOMOLOGY

orchard or field. It is usually much easier and cheaper to
prevent an insect from getting a start in the orchard or garden
than it is to fight it after it has gained a firm foothold. "An
ounce of prevention is worth a pound of cure."

Among the most effective means of preventing insect injury
may be mentioned the following:

High Cultivation. — This not only makes the tree or other
plant yield its best returns but it is a well known fact that a
strong healthy plant is not nearly as apt to be attacked by as
many insect pests as one that is already weakened or, if it is
attacked, it is able to stand much more injury without the
effect being shown in the crop it yields. The first and best
way of fighting insect pests is then to keep the plant in the
very best condition possible by high cultivation, judicious
pruning, fertilizing, etc.

Clean Culture. — Many of the most injurious insects pass the
winter months under rubbish of various kinds that lies scattered
over the farm. If this rubbish is not allowed to accumulate
such insects will be more likely to perish during the winter.
Keeping clean will also reduce the opportunities for feeding and
breeding and allow a more thorough application of insecticides.
In orchards this recommendation for clean culture is of especial
importance. Many insects breed and complete their develop-
ment in dead wood or fallen fruit, others pass the winter months
or lay their winter eggs upon the smaller branches of the trees.
If the orchardist would take the pains to trim out and burn all
the dead and infected branches, and to see that all fallen fruit
was destroyed, there would be little complaint of some of the
insects that are now serious pests.

Crop Rotation. — Many insects live only on one kind of plant,
and when not able to find this plant they perish or are scattered
so as to do little damage. This fact may often be taken
advantage of by a system of crop rotation.

Protection of Plants. — Many small plants, especially in the
garden, may be protected by screens or other devices for
keeping the pests away from the plants.

Late Plowing. — Many insects may be killed or exposed to
their enemies by plowing the field late in the fall. Some of

CONTROLLING INSECT PESTS 413

the wire-worms and the eggs of grasshoppers and other pests
are thus destroyed. Late plowing of fallow lands is especially
important, as there are usually many insects in such fields.

Trap Crops. — It is sometimes profitable to plant a crop that
is attractive to the insects that are to be combated and after
the insects have gathered there, to destroy the whole crop by
burning or plowing it under or spraying it with some insecti-
cide that will kill the insects. In this way the main planting
of the same or other crops may be left comparatively free from
the pests.

ACTIVE METHODS OF CONTROL

In spite of all our care and precautionary measures, however,
many pests \vill certainly become established in the orchard or
garden or field, and then the fight must be waged against the
insects themselves.

Hand-picking. — This is often the simplest way of getting rid
of many of the larger insect pests. Large caterpillars, like the
tomato-worm and the larvae of other moths, are easily seen
and destroyed. Tent-caterpillars are also best fought by
gathering them after they have collected in their "tents" and
crushing or burning them. In the fall or winter the eggs
of such moths as the tussuck-moth are easily gathered and
destroyed.

Trapping, etc. — Insects may often be found collected in con-
siderable numbers under loose boards or boxes scattered over
the field. If such places be examined occasionally many injuri-
ous insects can be destroyed. The larvae of certain moths, as
the codling-moth, pupate in any sheltered place they find on
the trunk of the tree. Advantage may be taken of this habit
by placing a band of burlap around the tree. Under this the
larvae collect and they may easily be destroyed. The use of
lights in the field to attract moths is more or less successful in
some places. Numbers of cut-worm moths may thus be
destroyed. Codling-moths are not attracted to these lights.

Insecticides. — The most widely used and perhaps the most
effective method of fighting insect pests after they have obtained
a foothold in the orchard, is the use of insecticides, or insect

414 ECONOMIC ZOOLOGY AND ENTOMOLOGY

poisons. These may be considered under four heads: first, the
internal poisons, or those which take effect by being eaten along
with the ordinary food of the insect; second, the contact in-
secticides that kill the insects when applied directly to their
body; third, the gases that are used for fumigation, and, fourth,
various substances that act as repellents. The kind of insec-
ticide to be used depends in a large degree upon the structure
of the mouth-parts of the insects. For beetles, the larvae of
moths and butterflies, and others with biting mouth-parts
the internal poisons are used, while for the various insects
with sucking mouth-parts, as the plant-lice, scale-insects, etc.,
the contact insecticides are used. The reason for this is very
plain. It would be useless to spray a plant with poison when
it was infested by an insect with sucking mouth-parts, for
such insects obtain their food from the juices of the plant
which are not reached at all by the poison. But if the plant
is infested by biting insects, such an application of poison to
all the leaves and tender shoots would be effective, for with
each bitten off and swallowed mouthful of leaf, the insect would
get a dose of the poison.

Internal Poisons. — Paris green was for a long time regarded
as the most efficient of the internal poisons and is still used to a
limited extent.

The poison is applied as a spray, using one pound of Paris
green to 150 to 200 gallons of water for such trees as apples,
pears, etc. For peach and plum trees and other plants with
delicate foliage which is very susceptible to the poison the
mixture should not be stronger than one pouud of Paris green
to 250 or 300 gallons of water. A pailful or two of fresh lime
water should be added to every 200 gallons of the mixture to
prevent the poison from scalding the foliage. In preparing
the mixture the Paris green should first be mixed into a fine
paste with a small amount of water; it should then be strained
thoroughly and the bulk of water added. The lime may be
added to the paste before straining, in amount equal to the
amount of poison used, instead of being added to the mixture as
above recommended. The mixture must be kept well stirred
during the spraying.

CONTROLLING INSECT PESTS 415

For fighting such insects as cut-worms and grasshoppers
a bran mash poisoned with Paris green is often very effective.
This may be made as follows: thoroughly mix one pound of
Paris green with twenty-five pounds of bran or middlings
and moisten with about a gallon of water which has been sweet-
ened by adding one or two quarts of cheap molasses. This will
make a stiff mash that may be placed in the affected field, a
tablespoonful or so in a place.

For most purposes arsenate oj lead is now used instead of
Paris green. It is less injurious to the foliage, remains in
suspension longer, and in many other ways is better than Paris
green. It may be manufactured at home, but it is usually
safer to buy some of the reliable brands that are on the market.
It comes in two forms, as paste and powder. Four to ten
pounds of the paste, or two to five pounds of the powder,
are used with every 100 gallons of water. The spraying should
be so thoroughly done that all the foliage and fruit is covered
with a thin film of the poison. Some fungicide, such as Bor-
deaux mixture or sulphur -lime, is of ten used in connection with
this insecticide, and the trees are thus freed from their insect
pests and fungus diseases with one spraying. A gallon of mo-
lasses or twenty- five pounds of glucose is often added to every
loo gallons of the spray when arsenate of lead is used for flea-
beetles and other leaf-feeding insects on cabbages, turnips, etc.

White hellebore is often used instead of arsenic, especially
in the garden. It may be applied dry, diluted with five or ten
parts of flour, or it may be used as a spray, one ounce to a
gallon of water.

Contact Insecticides. — Of the many contact insecticides
used, the sulphur-lime solution is, in many respects, the best.
It acts quickly on the scaly covering of such insects as
the San Jose scale and soon kills the insect. It has the addi-
tional advantage of being an excellent fungicide as well as an
insecticide. There are many brands of concentrated sulphur-
lime solution on the market, and most orchardists now prefer
to buy some of these rather than prepare the mixture them-
selves. In using these all that is necessary is to add water and
apply thoroughly with the spray pump. The strength of the

4i6 ECONOMIC ZOOLOGY AND ENTOMOLOGY

various commercial brands varies somewhat but as a rule nine
to twelve gallons of the concentrated solution to 100 gallons of
water should be used in treating trees in the winter for such
insects as San Jose scale and blister-mites. For use in the
summer for fungus and soft-bodied insects, such as aphids
and young scale-insects, the proportion should be about
two or three gallons of the concentrated solution to 100 gallons
of water. It has recently been demonstrated that in some
instances sulphur-lime solution jnay take the place of arsenical
sprays as it acts as a stomach poison as well as a contact in-
secticide. Sulphur-lime, three gallons to 100 gallons of water,
has been used with some success in controlling the codling
moth. The addition of a little arsenate of lead will probably
be found advisable.

It is somewhat difficult to prepare sulphur-lime wash with
uniformity unless one is well prepared for this work. The
best plan is to obtain one of the bulletins issued by the state
in which the orchardist lives, and follow carefully the directions
given there. The following formula is one that is often used:

Unslaked lime 5 pounds

Flowers of sulphur n pounds

Water 5 gallons

Put a little of the water in a kettle or boiler over a good fire;
add the lime and after it has started to slake sift the sulphur
over it adding enough water to maintain a thin paste. After
the slaking and mixing are completed add more water and boil
for about one hour adding enough water from time to time to
make up for evaporation. If properly made the mixture will
be of an amber color, and there will be but little sediment.
This is a concentrated solution which, before using, should be
diluted to the strength indicated above.

Kerosene emulsions or distillate oil emulsions are often used
for many of the soft-bodied sucking insects. The follow-
ing is the standard formula for kerosene emulsion: kerosene
2 gallons; soap (preferably whale-oil soap) 1/2 pound; water
i gallon. The soap should be dissolved in the water heated to
boiling and the kerosene then added. Churn or otherwise

CONTROLLING INSECT PESTS 417

thoroughly mix the kerosene and soapsuds until a thick emul-
sion is formed which will set on cooling. When needed mix one
part of this emulsion with twelve parts of water and spray
over the insects.

The distillate-oil emulsion can only be made satisfactorily
with a power sprayer. The proportions are: distillate oil 20
gallons, fish oil or whale-oil soap 30 pounds, hot water 12
gallons. Five and one-half gallons of the emulsion should be
used to each 100 gallons of water when spraying for such in-
sects as thrips. About a pint of strong tobacco extract
added to each 200 gallons of diluted distillate oil emulsion
adds much to its efficiency as a spray for thrips.

There are several miscible oils on the market under various
trade names. These are convenient to use because they readily
mix with water. The proportions to use for the winter and
summer sprayings are generally indicated on the package
containing the oils.

Resin sprays are still used in some regions, particularly for
white-flies on citrus trees. The following formula has proved
satisfactory: resin 20 pounds, caustic soda, pulverized, 7
pounds, fish oil 3 1/2 pints. Boil together in a little water and
finally add enough water to make 100 gallons.

A carbolic acid emulsion, made by adding i gallon of crude
carbolic acid to eight pounds of whale-oil soap that has been
dissolved by boiling in eight gallons of water, makes a good
stock solution for sprays for aphis, mealy-bugs and other soft-
bodied insects. For use add twenty gallons of water to every
gallon of the emulsion.

Whale-oil soap or common laundry soap are often used for
spraying for aphids or other soft-bodied insects.

Tobbacco extracts and nicotine solutions are sometimes very
efficient when used by themselves or in connection with some
other material.

There are several mixtures that are used for dipping animals
infected with ticks or mites. Sulphur-lime, crude oil, white
arsenic, tobacco and other substances are used for this purpose.
As the use of most of these is attended with more or less danger
unless properly done the detailed directions given in some of
27

4i8 ECONOMIC ZOOLOGY AND ENTOMOLOGY

the recent government and experiment station bulletins
should be consulted. (See p. 419).

Pyrethrum, Persian insect powder, or buhach, is a powder
made by pulverizing the flowers of pyrethrum. It gives off
a volatile oil which is poisonous to insects but does not affect the
higher animals. It is used principally as a household remedy,
where it can be dusted on or near the insects.

Gases. — As the citrus trees and some others have a very
dense foliage and retain their leaves the year round it is difficult
to spray them with the ordinary insecticides. When it is
necessary to treat them for insect pests they are usually fumi-
gated with hydrocyanic acid gas, which is generated under a tent
that is placed over the tree. Nine ounces of water are placed
in an earthenware vessel and three ounces of sulphuric acid
added; then three ounces of potassium cyanide are dropped
into the liquid and the tent quickly closed as the gas that is
immediately generated is deadly to all animal life. The
amount of gas necessary to kill all the insects on the tree varies
with the species of insects and the size of the tree. Careful
tables are given in government and state bulletins relating to
this subject.

Nursery trees that are infested with scale-insects or other
pests may be placed in a tight bin or a fumigating house and
given a thorough treatment with this gas. It is also some-
times used in greenhouses for scale-insects, aphids, etc., and in
mills that have become infested with the Mediterranean flour
moth or other pests. This gas is sometimes used to kill
household pests such as bedbugs, cockroaches, etc., but as it is
very dangerous it should never be used except by some ex-
perienced person.

Carbon bisulphide is used in killing insects in stored grain
and sometimes also in treating subterranean insects. It is
bought and used as a liquid which volatilizes into a heavy, ill-
smelling gas which is not quite as deadly as hydrocyanic gas
but is so strong that large doses prove fatal to all animal life.
It can be used in closets infested by clothes-moths by exposing
some of the liquid in a saucer on the floor, (better on a shelf as
the fumes are heavier than air and sink rather than rise) and

CONTROLLING INSECT PESTS 419

closing the door and cracks of the closet. Or infested cloth-
ing may be put into a tight trunk or box together with a small
saucer of the liquid. It is highly explosive and must never be
used in the presence of any artificial light.

When sulphur is burned, very poisonous fumes, mostly
sulphur dioxide, are given off. This gas is fatal to all animal
life and is sometimes used in fumigating rooms or other en-
closed spaces that are infested with insects. Under the head
of " Clayton gas" it has recently been much used for fumigating
ships and ship's cargoes to kill the rats and insects that are so
often found in the holds. It is very penetrating and effective
but is usually objectionable on account of its strong bleaching
properties especially in the presence of moisture. Seeds treated
with this gas will not germinate.

Repellents. — There is a popular belief that any ill-smelling
substance will keep insects away from plants. While this is
not wholly true there are some substances which when applied
to a plant seem to afford it more or less immunity from the
attacks of certain insects. Bordeaux mixture, crude carbolic
acid and thick soap washes are among the most effective of
such substances and the various proprietary repellant mixtures
that are on the market usually depend on one or more of these
substances for their usefulness. As a general rule but little
reliance can be placed on them.

How TO OBTAIN STATE AND GOVERNMENT PUBLICATIONS

Frequent reference has been made and will be made in the
following chapters to various reports or bulletins issued by
state officials or by the United States Department of Agricul-
ture. Some of these are technical in character and intended
for special students but most of them are written for the general
public and give in a clear concise manner the results of the
latest studies and investigations on the subjects discussed.

The reports and bulletins of the various State Agricultural
Experiment Stations can be had by applying to the director of
the station in whatever city this station is situated. When
making application for such bulletins the applicant should state

420 ECONOMIC ZOOLOGY AND ENTOMOLOGY

the particular subjects in which he is interested, and any
available publications on that subject will be forwarded to
him. In a few states the State Entomologist is not an officer of
the Experiment Station. In such instances applications for
his publications should be directed to the State Entomologist.
His office is usually in the capital city. Some states maintain
a State Board of Horticulture or Agriculture which issues
reports or bulletins that are often of great interest.

Most of the government bulletins are also for free distribu-
tion. Each month the office of Experiment Stations issues a
list of the publications that have been published during the
preceding month. This "Monthly List of Publications" is
sent regularly to all who apply for it. Address the Editor and
Chief of the Division of Publications, U. S. Department of
Agriculture, Washington, D. C. Only a limited number of
each issue of many of the government publications is available
for free distribution. When this supply is exhausted the
publication may be had by applying to the Superintendent of
Documents, Washington, D. C. A small charge, usually only
five to twenty cents for bulletins, is made by this office. On
request the Superintendent of Documents will mail a price-list
of all the government publications relating to entomology,
ornithology, agriculture or any other subject.

The Division of Publications has recently issued a very
helpful circular (No. 19) giving a list of the "Publications of
the United States Department of Agriculture Classified for the
Use of Teachers." This may be had by applying to the
Editor and Chief of the Division.

The Department of Agriculture also issues a series of
"Farmers' Bulletins" and a "Year Book," both of which
contain a great deal of interesting and useful information on
many topics relating to agriculture.

The Farmers' Bulletins may be had by applying to the
Secretary of Agriculture. The Year Books can usually be
more readily obtained by applying to the congressman repre-
senting the district in which the applicant lives. The congress-
man may also supply the Farmers' Bulletins.

CHAPTER XXXII
INSECTS INJURIOUS TO ORCHARD TREES

It is estimated by careful and expert observers that insect
pests take, each year, about one-fifth of the American fruit
crop. This is an annual money loss to the growers, and to the
nation, of about sixty million dollars. A large part of this
loss can be prevented.

The orchard pests include insects of many kinds, repre-
senting different orders, and varying greatly in life history,
habits and structure. The injury to the trees may be to the
roots, the trunk, the leaves, the flower buds, or the fruit.
Apple trees, for example, have their roots attacked by the
woolly-aphis, their trunks mined by the round-headed and
flat-headed borers, their leaves eaten by tent-caterpillars, the
buds attacked by the larvse of the bud-moth, and the fruit
burrowed into by the codling-moth grub.

The insects attacking a particular part of the tree, as the
leaves, may effect their injury in different ways. They may
eat the leaves, as caterpillars, beetles and other insects with
biting mouth-parts do; or suck the plant juices from them, as
the aphids, scale-insects and other insects with sucking mouth-
parts do. Similarly with the fruits. Some insect pests bite
holes in them, some suck juice from them, and some bore un-
sightly tunnels in them, the insects feeding and developing in
the very heart of the fruit.

Even in the case of two different insects that attack the same
parts of the same kind of orchard trees in much the same way,
as with two biting insects that eat the leaves, there may yet be
such differences in their life history and habits that the best
remedies for them may be radically different. The remedy for
one, which may be a wingless insect, might be an easy means of
preventing its access to the leaves; for the other, a winged

421

422 ECONOMIC ZOOLOGY AND ENTOMOLOGY

kind, which cannot be kept from the leaves, the remedy may be
the application of a poison on the leaf surfaces so that with each
bite will go a dose of poison.

Thus there is not much practical advantage in discussing
in general terms the insect pests, or the conditions of insect
attack, of orchard trees. We believe it will be better worth
while for the elementary student to try to get acquainted with
a few of the more important specific orchard pests in his
locality, and to that end we have given in the following
paragraphs, brief accounts descriptive of the insect, its life,
the character of the injury done by it, and the approved reme-
dies for it, of a number of the most serious and widespread of
these pests. Some of these insects can be found and observed
by the student at almost any time of the year in almost any
orchard.

For fuller information about the insects mentioned in this
chapter, and for accounts of many others, injurious to orchards,
some manual of economic entomology may be consulted. San-
derson's "Insect Pests of Farm, Garden and Orchard" is an
excellent recent book of this kind. O'Kane's "Injurious
Insects" is another.

Codling -moth (Cydia pomonella). — Of all the pests of apples,
the codling-moth is easily first in importance. In many
orchards where the codling-moth is uncontrolled by spraying
50 per cent, to 90 per cent, or more of the fruit is infested.
By proper spraying the amount of loss may be reduced to
only 5 per cent, or even 2 per cent, yet this insect now costs
us, when we consider both the loss from bad fruit and the
amount expended in fighting it, about twenty million dollars a
year.

The winter is passed in the larval stage as a little white
grub safely hidden away in a tough little cocoon underneath
the rough bark of the tree or in other protected places in the
orchard or in the store room where the apples have been stored
for the winter. Early in the spring the larva changes to pupa,
and about the time the trees are in bloom there issues the
small purplish-brown moth. It has a wing expanse of but
three-fourths of an inch. The fore- wings are marked by fine

INSECTS INJURIOUS TO ORCHARD TREES 423

greenish lines or bands and often by minute golden spots on
the outer margin. The hind wings are grayish, and darker
toward the outer margin. The codling-moths fly at dusk and
usually lay their eggs on the leaves. The larvae may feed on
the tender leaves for a short time, but they soon make their
way to the calyx, or blossom, end of the forming fruit and enter
there. A few may enter at the stem end or in the sides of
the fruit. For the next three or four weeks they burrow
and feed in the apple, usually around the core, and, finally,
having attained their full growth, bore their way out and drop

FIG. 196. — Codling-moth, Cydia pomonella. (Twice natural size.)

to the ground and hide themselves under pieces of rough bark
or other rubbish where they form a thin cocoon. In some
regions there is only a single generation each year, but in
most regions there are two and in some places three and even
part of a fourth.

If all the larvae that hide themselves away in the fall were to
live through the winter the insect would be a much more serious
pest than it is. Fortunately a large proportion of them is
destroyed by the birds during the winter. Many apples are
carried into the store houses before the worms have issued
from them, and when these leave the apples they hide away
in protected places, and the moths that issue the next spring
will fly back to the orchards unless the store rooms are care-
fully screened so that they cannot escape. In many places

424 ECONOMIC ZOOLOGY AND ENTOMOLOGY

it has been found worth while to tie bands of burlap around
the tree so that the larvae will find there suitable places to
pupate. During the summer these bands are examined often

FIG. 197. — The larva, or worm, of codling-moth, Cydia pomonella.
(Three times natural size; after Slingerland.)

and any larvae or pupae found are destroyed. In the fall they
should be removed or very carefully examined to see that none
of the larvae pass the winter in them.

FIG. 198. — Cocoons of codling-moth larvae under bark on old apple
tree. An empty pupa case shows where the moth has issued from one of
the cocoons. (Natural size.)

Spraying with Paris green or arsenate of lead must be relied
upon as the principal means for controlling this pest. Three

INSECTS INJURIOUS TO ORCHARD TREES 425

or four pounds of arsenate of lead (paste) to one hundred gallons
of water make the most effective spray. The proper time to
spray for this pest is just after the petals fall and while the
calyx cup is still open. It is of prime importance that the
calyx cup of every small apple or pear be filled in order that
the first meal that the young larva takes on the fruit will
contain enough of the poison to destroy it. In regions where
most of the larvae of the first brood hatch at about the same
time it has been found that a single spraying thoroughly done
at the proper time will save 95 or sometimes 98 per cent, of the
fruit. In places where the larvae issue irregularly it may be
desirable to give a second spraying about three or four weeks
after the blossoms fall, or even a third still later. The first
spraying should be done by using a coarse spray with a pressure
of from 150 to 250 pounds. This drives the spray through the
stamens and into the lower calyx cavity. Later sprayings
may be applied as a finer mist in order that a thin film of the
poison may be left over the surface of the fruit and leaves.

The Apple-maggot, or Railroad-worm (Rhagoletis pomonella).
— Sometimes an apple that is apparently perfectly sound ex-
ternally will be found to be "railroaded" inside by a dozen
or more little maggots that make discolored streaks through-
out it. When these larvae leave the apples they pupate in the
ground or in the boxes or barrels where the apples have been
stored, and early the next summer the adult flies issue. They
are a little smaller than the house-fly, and have the wings con-
spicuously marked by four black connected bands; the body is
blackish with yellowish head and legs, and 'with narrow white
stripes across the abdomen.

This pest can be controlled by destroying infested summer
apples by gathering them up at least twice a week, or by allow-
ing hogs to run in the orchard and eat all the apples that fall.

The Cherry Fruit-fly (Rhagoletis cingulata) . — This insect, the
larvae of which are often found in cherries, looks very much
like the adult of the apple-maggot, but it is somewhat smaller
and the black bands across the wings are arranged differently.

All fruit found to be affected should be destroyed before the
larvae have a chance to escape and pupate.

426 ECONOMIC ZOOLOGY AND ENTOMOLOGY

The Mediterranean Fruit-fly (Ceratitis capitata). — This is
probably the most important fruit pest in the world. At the
time this is being written it does not yet occur in North America,
but there is always danger of its being introduced from Hawaii
or other tropical islands where it is now doing much damage.
Under favorable conditions it multiplies very rapidly and as
it attacks many kinds of cultivated and wild fruits its
introduction into this country might result disastrously to
much of our fruit, particularly on the Pacific Coast and in the

FIG. 199. — Mediterranean fruit-fly, Ceratitis capitata. (Much enlarged.)

South. The fly is a little smaller than the common house-
fly and is closely related to the two fruit-flies just described.
Figure 199 shows the characteristic markings of the wings.
The quarantine officers in all of our ports are carefully watch-
ing for this pest, and are destroying all fruit or vegetables that
may contain the living larvae.

The Plum Curculio (Conotrachelus nenuphar). — While this
little insect causes most injury to plums it may also attack
peaches and cherries. The adult is a thick-set beetle a
little more than three-eighths of an inch long, black, but covered
with short, fine, brownish hairs; there are also a few patches
of white hairs. The back is marked w'ith conspicuous ridges

INSECTS INJURIOUS TO ORCHARD TREES 427

and tubercles. The head is produced into a long snout. The
female beetle hibernates under leaves or rubbish, and as soon
as the fruit is formed commences to lay her eggs in it in small
holes that she makes with her snout. After laying her eggs
she makes a small crescent-shaped cut in the skin of the fruit.
This characteristic mark has suggested the common name
"little Turk" for this pest. The larvae usually feed around
the pit, often causing the fruit to drop. When full grown they
crawl out, pupate in the ground, and the adult beetles, which
issue three or four weeks later, feed on the ripening fruit, often
doing much damage before they
seek out a suitable hiding place
in which to pass the winter.

As the beetles have the habit
of "playing possum" when
alarmed many of them may be
caught by jarring the tree with a
padded club and causing them to FlG- 200. — The plum cur-
Hrnn tr> a ranvac that hac KPPTI culio> Conolrachelus nenuphar.

drop to a canvas that nas been (Enlarged. after siingerland.)
spread under the tree. Some

fruit growers use curculio catchers made by stretching a
canvas on a frame that is mounted on wheels, a slit being
left in one side to allow the apparatus to be wheeled against
the trunks of the trees. Recent experiments seem to indicate
that spraying the leaves with arsenate of lead may be a satis-
factory method of control as the beetles feed for awhile on the
foliage when they first issue in the spring.

Tent -caterpillars (Malacosoma americana). — The larva? of
many moths often occur in such numbers in the orchard that
they quite strip the trees of their foliage. Among the most
conspicuous of this group of pests are the tent-caterpillars,
so-called on account of their habit of living together in colonies
and spinning a large web or tent in which or on which they
rest at night or at other times when not feeding. When full
grown each finds a convenient place to spin a thin, tough, white
cocoon from which, a few weeks later, the adult moth issues
and lays the eggs which are to remain on the trees over winter.
The eggs are laid in a mass usually on the smaller branches,

428 ECONOMIC ZOOLOGY AND ENTOMOLOGY

often making a complete band around a twig. They are
covered with a frothy, glue-like substance which protects them
during the winter and furnishes the first meals for the young
larvae.

These pests have many natural enemies, such as birds,
Hymenopterous parasites and an important bacterial disease.
These help much to control them, but it is sometimes necessary

FIG. 201. — Egg mass and small tent of tent-caterpillar,
thirds natural size.)

(About two-

to resort to active methods of control. The eggs may be
pruned off in the winter and placed in a box covered with a
screen so that the parasites may be allowed to escape and the
larvae be retained when they hatch. The tents containing
the young larvae can be quickly gathered and destroyed when
they are small. Spraying very early, before the blossoms ap-
pear, with arsenate of lead will kill many of the larvae.

Canker-worms. — -The canker-worms, inch-worms, measur-
ing-worms, or loopers are common throughout nearly all parts

of the United States. There are two species, the spring canker-
worm, Paleacrita vernata, which has only one pair of abdominal

FIG. 202. — A trio of apple tent-caterpillars, larvae of the moth Mala-
cosoma americana. These caterpillars make the large unsightly webs or
tents in the apple trees, a colony of the caterpillars living in each tent.
(Natural size; after Slingerland.)

legs, and the fall canker-worm, Alsophila pometaria, which
has two pairs. Otherwise they are very similar in appearance.

430 ECONOMIC ZOOLOGY AND ENTOMOLOGY

They have similar habits also, except that the adult of the
spring canker-worm lays her eggs early in the spring, while the
moth of the fall canker-worm lays hers late in the fall. The
larvae of both species issue about the same time in the spring
and feed on the tender foliage. The young canker-worms
have a habit of dropping from the tree when it is jarred or
shaken and hanging suspended by a slender thread which they

FIG. 203. — California tussock-moth, Hemerocampa vetusta; larva and co-
coon with an egg mass on the cocoon. (About natural size.)

spin from the mouth as they drop. They pupate in the ground
and the spring canker-worm passes the winter in this stage,
the adult issuing early in the spring. The female moth is
entirely wingless and less than one-half of an inch long. They
climb up the trunks of the trees and lay their eggs in irregular
masses underneath the loose bark or in cracks or crevices. The

INSECTS INJURIOUS TO ORCHARD TREES 431

fall canker-worm moths issue during November and December
and lay the eggs which are to hatch early the next spring.

The most efficient remedy is to spray with arsenate of lead
as soon as the foliage is well open. A second later spraying is
sometimes desirable. It is a common practice to place bands
around the trees to prevent the females crawling up to lay their
eggs. These bands usually consist of a strip of some heavy
paper tied tightly around the tree after the bark has been made
smooth. It is then covered with some sticky substance, such
as "tanglefoot," which will prevent the moths from crawling
over it.

The White-marked Tussock-moth (Hemerocampa leuco-
stigma). — The females of the tussock-moths are similar in

FIG. 204. — California tussock-moth, Hemerocampa vetusta; male above;
wingless female below. (Natural size.)

appearance to the female canker-worm moths, being entirely
without wings. When they issue from the cocoon they seldom
travel far, often simply crawling on top of the cocoon to deposit
their eggs. The larvae vary a great deal in color and markings,
but they are always covered with long blackish or yellowish
hairs and have conspicuous tufts toward the anterior and
posterior ends of the body. On the Pacific Coast the most
common tussock-moth is H. zetusta, but there are other species
that may be found in the orchard or in woodland trees.

432 ECONOMIC ZOOLOGY AND ENTOMOLOGY

The best method of control is to gather the eggs during the
winter and destroy them. The larvae seem to be very resistant
to poisons, and when the arsenical sprays are used it is necessary
to make them very strong.

Climbing Cut-worms. — Several species of smooth-bodied
cut-worms often climb the trees, eating the foliage or destroying
the young fruit. Sometimes these cut-worms go in great

FIG. 205. — Green-fruit worms, Xylina grotei, at left, and Xylina anten-
nata, at right. (Natural size; after Slingerland.)

bands or armies traveling across the country and destroying all
the vegetation in their path. The adults, which are moths that
usually fly only at night, are mostly grayish or brownish, and
are often called owlet-moths on account of the peculiar appear-
ance of the eyes and head.

About the only successful method of combating cut-worms
after they have once gained foothold on the trees is to jar
them off and destroy them. Fortunately they are attacked by
several natural enemies which generally keep them in control.

The Bud -moth (Tmetocera ocellana). — Often the unfolding
leaves of fruit trees are tied together with silken webs making

INSECTS INJURIOUS TO ORCHARD TREES 433

an irregular nest in which the larvae of the bud-moth feed and
in which they pupate. Because they attack the buds before
they are open they are able to do considerable damage before
anything can be done to control them.

A careful spraying with arsenate of lead just as the leaves
begin to unfold is about the only remedy that can be recom-
mended.

^ The Pear Thrips (Euthrips pyri).—For several years this
little insect has been the most serious pest with which the
orchardists of central California have had to contend, and
recently it has been discovered
that it also occurs in some of
the eastern states where it does
considerable damage. It at-
tacks many kinds of orchard
trees, but does particular injury
to pears, cherries and prunes.
The adult thrips are minute,
black-bodied insects with their
four long narrow wings fringed
with long hairs. They appear
early in the spring and soon
make their way into the ten-
derest part of the bud, often
completely destroying it. A
little later they begin laying the eggs from which the wingless
young thrips hatch. These continue the destructive work
begun by the adults. The insect passes the winter in the
larval and pupal stages in the ground, the adult issuing very
early the following spring.

In fighting this pest some insecticide must be used that will
penetrate the buds and kill the thrips without injuring the
buds. The distillate oil emulsion and tobacco extract (see
page 417) have proved most efficient in California. The first
spraying must be done as soon as the adult thrips are numerous
on the trees, the second application should follow ten days
later, and still a third, which is for the larvae, should be given
about two weeks after the second. Deep plowing in the fall

FIG. 206. — The pear thrips, adult-
(Much enlarged; after Moulton.)

434 ECONOMIC ZOOLOGY AND ENTOMOLOGY

and winter will destroy many of the larvae and pupae that are
in the ground.

The Pear- leaf Blister-mite (Eriophyes pyri}. — This little
mite, that causes red blister-like blotches on the leaves of the
pears and sometimes of the apples, is not an insect, as is
commonly supposed, but is an Arachnid and is discussed on
page 213.

The Peach Borer (Sanninoidea exitiosa). — This insect is
probably the most important of those that attack the trunk
of orchard trees. Not only the peach but the apricot, plum,

FIG. 207. — California peach-tree borer, larva of Sanninoidea opalescens,
in cocoon. (About natural size.)

prune and nectarine may be seriously affected by it. The eggs
are laid on the outer bark near the base of the trunk. The
larvae burrow in and feed on the inner bark usually close to the
surface of the ground. Their presence is indicated by gummy
exudations mixed with the castings of the larvae. Several
larvae feeding on a tree may completely girdle it or so weaken
it that it will bear little fruit and be much more subject to
the attacks of other insects or diseases. Much of the sawdust-
like castings and bits of bark are incorporated in the cocoon
which the larva spins in the end of the burrow or on the surface
of the tree, or in the ground close to the surface. The adult

INSECTS INJURIOUS TO ORCHARD TREES 435

insects are beautiful, clear-winged, steel-blue moths. The
abdomen of the female is marked by a conspicuous orange band,
that of the male by three or four much narrower stripes.

The moths may sometimes be kept from laying their eggs
on the tree if the trunk is wrapped with some heavy paper
and the earth mounded up around the crown. Various re-
pellent or protective washes have been tried with but little
success. After the larvae have entered the tree they must be
dug out and destroyed. If the trees are well mounded up

FIG. 208. — Adults, male and female, California peach-tree borer, Sanni-
noidea opalescens. (About natural size.)

early in the spring it will greatly facilitate the work of " worm-
ing" early in the fall, for most of the young larvae will be above,
the surface of the ground when the mounds are levelled.

A closely related species known as the California peach-tree
borer, S. opalescens, occurring on the Pacific Coast, has habits
and a life history similar to the eastern species and yields to
the same methods of control.

The Peach Twig-borer (Anarsia lineatella). — Early in the
spring many of the tender shoots on the peach trees will often

436 ECONOMIC ZOOLOGY AND ENTOMOLOGY

wither and die. If these are examined, minute, brownish,
black-headed larvae may be found in them. These larvae bore
down the center of the stem for one or two inches. When the
firmer wood is reached they leave the dead shoot and attack
another live one; thus one larva may destroy several twigs.
When full grown the larvae crawl down the branches to the
trunk of the tree, where they pupate. The small dark gray
moths that issue from these pupae lay their eggs on the new
twigs near the bases of the leaves. These eggs soon produce
the second generation of larvae which feed on the twigs as did
the first generation. In some places a third brood of larvae
may appear late in the fall. These, as well as the members
of the second brood, will often attack the fruit, usually working
in or around the seed, often doing much damage and always
making the fruit unattractive.

The larvae of the last brood pupate early in the fall, and the
moths that issue from these pupae lay their eggs close to the
crotches of the tree. The young larvae that issue from these
eggs bore into the bark in the crotches and make a little cell
in which they pass the winter. Little turrets made of pellets
woven together with silk spun by the larvae mark the locations
of these silk-lined cells in which the larvae hibernate. As
soon as the buds begin to grow in the spring the larvae leave
their burrows and begin their destructive work. The most
effective remedy is to spray the trees with sulphur-lime as
soon as the buds begin to swell. This will kill the larvae
after they have opened up the winter cells and are migrating
from these to the tender shoots.

The Round-headed Apple-tree Borer (Saperda Candida}. —
Frequently the trees in young apple orchards are injured by
cylindrical round-headed larvae boring in the trunk. A few
of these larvae working in a small tree may entirely girdle it.
After feeding in the cambium for twro seasons the larvae bore
into the heart of the wood, and not until the third season do
they change to the pupae from which the adult beetles issue.

The methods of control are much the same as those suggested
for the peach borer, the object being to keep the beetle from
laying her eggs on the tree, and to cut out any larvae that may

INSECTS INJURIOUS TO ORCHARD TREES 437

have gained an entrance before they have had time to do
much injury. A heavy coating of whitewash kept over the
trunk of the trees during the summer affords much protection.

There is also a flat-headed borer that works in the trees
in much the same way, and can be controlled by the same
methods.

The Periodical Cicada (Cicada septemdecim) . — It is com-
monly supposed that cicadas do much damage to the orchard
trees. As a matter of fact, however, the injury that they cause
is not particularly serious except to young trees. When the
female is laying her eggs she makes rather large holes or wounds
in the bark with her ovipositor. As soon as the young hatch
they drop to the ground and bury themselves in the soil
where they feed on roots and other substances for more than
sixteen years, finally changing to the pupae or nymphs. Then,
seventeen years after the eggs have been laid, they issue
as the adult cicadas, which soon lay their eggs and die. As
there may be more than one brood in a locality with different
times of emergence it is not always seventeen years between
the outbreaks. Government bulletins giving dates upon which
all the various broods occurring in the United States may be
expected to issue, can be obtained by making application as
suggested on page 420.

There are other species of cicadas that complete their
development in much less time. Although these insects do
not at all resemble grasshoppers, the two have been confused
under the term locust, the periodical cicada often being re-
ferred to as the seventeen-year locust; the term locust, how-
ever, is properly applied only to the grasshoppers.

APHIDS, OR PLANT-LICE

In structure and habits the plant-lice (family Aphidida)
are among the most interesting of our insects. They are all
very small and soft-bodied, and feed upon the leaves or stems
of plants, sucking the sap by means of a long slender beak.
Their life history is subject to considerable variation among
the different species, but they all agree in certain features.

438 ECONOMIC ZOOLOGY AND ENTOMOLOGY

The eggs are usually laid in the fall on the twigs or other parts
of the plant on which the insect is feeding. These eggs go over
the winter. The young aphids that hatch from these eggs in
the spring immediately begin feeding upon the host plant.
Usually this is a generation of females. When about two
weeks old they begin giving birth to living young which in turn
give birth to other young and so through the summer. Thus
there is a series of generations of wingless females that give
birth parthenogenetically to living young. In the fall there
appears a generation that is composed of both males and
females which are usually winged. After mating, the females
lay the winter eggs. At any time during the summer when food
becomes scarce or when conditions are otherwise unfavorable,
there may appear winged generations of females that fly to
other plants and thus provide for the distribution of the species.
This method of reproduction and distribution makes possible
a very rapid increase of the number of individuals. The off-
spring from a single female, if all the members of the summer
generations lived, would amount to hundreds of millions.
Fortunately, they do not all live. They have many natural
enemies, chief among which are the ladybird-beetles, the
syrphus-fly larvae, the lace-wing-fly larvae, the braconid-flies,
etc.

Certain secretions from the body of the aphids play an
important part in their life. Through small pores or openings
scattered over the body, many kinds, as the woolly aphis and
others like it, secrete a waxy substance that forms a mat of
felted or woolly threads which afford the insects considerable
protection. Nearly all of the aphids also secrete a sweet,
sticky substance known as honey-dew. Formerly it was sup-
posed that this honey-dew came from the two little tubercles
that occur on the posterior end of the body of many of them,
but it is now known that it issues in drops from the alimentary
canal. Sometimes so much is produced that the plants and
the ground below are quite covered with the sticky, honey-like
secretion. Many insects are very fond of this honey-dew,
the ants being especially partial to it. On page 492 is given
an account of a particular way in which the ants care forcer-

INSECTS INJURIOUS TO ORCHARD TREES 439

tain aphids for the sake of their honey-dew. But the ants do
not always assume such a definite relation to the welfare of
the aphids. Usually they appear on aphis-infested trees only
to feed on the honey-dew, and neither injure nor care for the
aphids. The black sooty fungus that grows on this honey-dew
often completely covers the leaves and fruit making them very
dirty and disagreeable to the sight and touch.

The Green Apple Aphis (Aphis pomi.} — This is one of the
most common aphids found on apple trees. It feeds on the
tender tips of the green shoots and upon the young leaves,
causing the leaves to become twisted and curled in such a
way that they afford excellent protection for the aphids that
are feeding within. At any time during the summer winged
females may appear and fly to other trees. Early in the fall
the sexual generation appears and the females lay their eggs
on the apple twigs. During the winter time these small, shin-
ing black, oval eggs may be found on the twigs, usually near the
tips. The best method of control is to prune off and destroy
all of the twigs on which the eggs are found. A strong sulphur-
lime spray will kill many of the eggs, but it does not always
give entire satisfaction. As the leaves begin to curl soon after
the aphids attack them it is hard to reach them with any spray.
A good strong tobacco spray, however, will kill many of them
if it is used very early. Kerosene emulsion may also be used.
It is necessary to use considerable force with any spray for
these insects in order to drive it into the curled leaves.

The Rosy Apple Aphis (Aphis sorbi}. — This species resembles
the preceding in habits and general appearance, but the body
is usually rosy in color. The color may vary, however, from
grayish to purplish or black. The winter eggs are not as
conspicuous as the eggs of the green aphis, and are not easily
detected. It is necessary therefore to rely upon the efficiency
of the sulphur-lime wash for destroying the winter eggs, or
upon some of the contact sprays for killing the insects after
they have attacked the leaves. It is thought that one genera-
tion of these aphids leaves the apple and migrates to some un-
known food plant on which they may pass the principal part
of the summer. In the fall some of the winged females return

440 ECONOMIC ZOOLOGY AND ENTOMOLOGY

to the apple trees and give rise to the sexual generation which
produces the winter eggs.

The Woolly Apple Aphis (Sckizoneura 'lanigera). — -This is
the most destructive of the apple aphids, doing particular
damage in young orchards, and as its most injurious work
is on the roots of the trees its presence is often not suspected
until the trees have been badly damaged. These aphids
secrete a white, woolly, waxen substance that covers the body,
and when a number of them are feeding together the white

FIG. 209. — Apple leaves curled by rosy aphis, Aphis sorbi. (Reduced.)

patches that they make are quite conspicuous. The forms that
feed above ground usually attack the new shoots or the tender
bark about wounds or scars on the trees. The greatest damage,
however, is done by the root-feeding forms. These gather in
small colonies over the smaller roots, where their feeding causes
knots or galls. If they are abundant many of the smaller
rootlets are killed and young trees, particularly, are thus seri-
ously injured. The larger roots may become very knotty and
much deformed, but the aphids are usually found on the
smaller tenderer roots. Many of the wingless aphids live over

INSECTS INJURIOUS TO ORCHARD TREES 441

the winter on the roots of the tree. Early in the spring
some of these migrate to the trunks or branches, where they
feed during the summer. There are several generations
of apterous females during the summer. In the fall winged
females appear which, it is believed by some students, migrate
to elm trees, where the eggs are laid in crevices in the bark.
These hatch early in the spring and cause the curly leaves on
the elm. A little later a generation containing winged females

FIG. 210. — Woolly aphis, Schizoneura lanigera, and the galls caused by
their attacks on apple tree roots. (Two-thirds natural size.)

appears, and some of these migrate back to apple trees and start
new colonies there. Elm trees near an orchard may thus serve
as a source of infection. It would probably be much easier
to keep nursery trees free from woolly aphis if the nurseries
were not located near groves of elms.

The aphids that occur on the trunk and branches may be
killed by spraying with kerosene emulsion, whale oil soap,
tobacco extract or other contact sprays. It is necessary that

442 ECONOMIC ZOOLOGY AND ENTOMOLOGY

the spray be applied with much force in order that it may
penetrate the woolly secretion that covers the insects. The
root forms are harder to control, as it is difficult to reach them.
But if the earth is removed from all of the roots that are within
eight or ten inches of the surface, and those affected then
treated with kerosene emulsion or tobacco extract, most of
the aphids may be destroyed. If the ground is thoroughly
wet with the emulsion or tobacco it seems to act as a repellant
and the roots may not be infested again for some time. As it
is the young trees that suffer most from the attacks of this
insect, great care should be taken to see that the pest is
not introduced into the orchard with nursery stock. No
nursery stock that shows any indication of having been at-
tacked by this aphis should be accepted, for by no treatment
can it be made absolutely safe. Nursery men often sprinkle
tobacco dust on the ground along the rows of growing young
trees. This not only kills some of the aphids that are close
to the surface, but it acts as a repellant, for a while at least.
Trees grown on Northern Spy stock do not seem to be as
seriously attacked as those grown on other roots.

Black Peach Aphis (Aphis persiccz-niger.} — There are
several other species of aphids that attack the peach, plum and
other orchard trees, usually confining their attacks to the
foliage or tender twigs. The black peach aphis is of particular
importance because, like the woolly aphis of the apple, it attacks
the roots as well as the leaves and branches. Both the winged
and the wingless aphids may be found on the foliage during
the summer, but winged forms do not seem to occur on the
roots. The aphids may be found on any of the roots through-
out the year, but they do most damage to the smaller roots.
As they cling tenaciously to the roots they are very apt to be
distributed on nursery stock, and great care should be taken to
keep them from being introduced into the orchard in this way.
The colonies are established on the foilage in the spring by some
of the larvae migrating from the roots. The methods suggested
for controlling the woolly aphis should be used in fighting this
species.

INSECTS INJURIOUS TO ORCHARD TREES 443

SCALE-INSECTS

Although most of the Coccidtz, or scale-insects, are so small
or obscure that they are usually overlooked by the ordinary
observer they are economically the most important group in
all the insect class. The scale-insects attack almost all kinds of
trees and shrubs, but it is difficult to make anything like a reason-
ably accurate estimate of the amount of damage done by them
because so many factors are involved. Some trees may harbor
many scale-insects and yet show but little injury, others when
only slightly infested by certain species suffer severely. The
injury may be only temporary, causing the leaves or fruit
to drop, or it may be permanent, retarding, dwarfing or even
killing the tree. In discussing the development and life history
of the scale-insects it will be convenient to group them into
three more or less well-defined groups. The first group includes
the mealy-bugs, which are common in almost all greenhouses,
and a few others, most of which move about over the plant
freely until ready to lay their eggs. In these the segmentation
of the body remains distinct, and the legs and antennae are func-
tional throughout the life of the female. The second group
includes the genus Lecanium and others, such as the common
black scale and the cottony maple-scale. The young insects of
this group wander about freely for a while, but before they are
half grown they insert their long projecting mouth-parts into
the tissues of the plant and remain stationary for the rest
of their life. The body-wall becomes dark and hard, often
very convex or hemispherical, and usually all resemblance
to an insect is lost. The third group includes those species
that have the body concealed by a scaly covering made up of
a waxy secretion in which is imbedded the molted skins of
the insect The San Jose scale, the oyster-shell scale, the
rose-scale, and others, are examples of this group. With
the second molt the female loses her eyes, antennae and legs,
and becomes a sac-like creature covered over with its protect-
ing scale and with its long beak thrust into the plant tissue.

In the first, or mealy-bug, group, the eggs of many species
issue from the body before they are hatched, the female often

444 ECONOMIC ZOOLOGY AND ENTOMOLOGY

secreting white filamentous or flocculent masses of wax which
protect the eggs. In the other groups the eggs may be hatched
within the body of the mother and the young produced alive, or
they may be protected underneath her body, or under the waxy
scale, until they hatch. The young, or larvae, of all the
species are very similar, being minute, mite-like, little creatures
that move about freely for a while. It is in this stage that
they scatter over the different parts of the tree and sometimes
even to different trees or orchards. The females molt twice
during their development. With some there is little change
in the appearance of the insect after these molts, but with
others, as we have seen, the changes may be very remarkable.
During the first stage, and often during the second also, the
males and females are very much alike, but in their further
development the male makes one more molt than the female
and enters a pupal stage in which the appendages of the future
adult can be clearly seen folded against the sides of the body.
The adult males that issue from these pupae are remarkable
in several respects. Although belonging to the order Hemip-
tera, the adults of which normally have two pairs of wings,
the male Coccids have only one pair, the second pair being
represented by two slender, little, hooked organs which hook
over the hind margin of the wings. They have no mouth-parts
or mouth-opening for taking food. In the place where the
mouth-parts are usually situated there is an extra pair of
eyes. In many species the end of the abdomen is provided
with long, pointed, stylet-like processes.

As the females never acquire wings, and as the larvae are so
small that they can crawl for only a few yards at the most,
it is evident that these insects must depend on some agencies
besides their own powers of locomotion for their general dispersal.
The active young larvae may crawl on the feet of birds, or upon
insects, such as the ladybird-beetles or the ants that are often
found on trees that are infested with the scale-insects, and thus
be carried for considerable distances to other trees or to near-by
orchards. Or they may crawl on the ladders or boxes or other
articles that are used in gathering the fruit. It is evident, how-
ever, that nursery stock or budding or grafting materials, are the

INSECTS INJURIOUS TO ORCHARD TREES 445

chief agencies by which scale-insects are transferred over any
great distances. The fact that most of them are very small
and inconspicuous makes it an easy matter for them to es-
cape detection, and thus important species are often introduced
into new regions even when a close watch is being kept for
them. For the same reason nursery stock and imported plants
of various kinds are the principal means of transferring these
pests from one country to another.

Besides the damage that the scale-insects do by sucking the
juices from the plant, and, in some instances at least, poisoning
the tissues on which they are feeding, they may secrete a con-
siderable amount of honey-dew, which makes the leaves,
branches and fruit sticky and disagreeable to handle, and fur-
nishes a medium in which a black sooty fungus grows. Badly
infested trees present a very disgusting appearance, and the
fruit is often unfit for use until it is washed thoroughly to
remove these substances. Many insects, particularly the
ants, are very fond of this honey-dew and feed on it as they do
on the honey-dew secreted by the aphids.

The list of scale-insects known to attack orchard trees is a
long one, but we shall note only a few of the most important.

The San Jose Scale (Aspidiotus perniciosus). — The San
Jose scale is probably the most important of 'all the scale-in-
sects, as it has become distributed over the whole United States
and is responsible for the death of many thousands of orchard
trees and the loss of much fruit in orchards in which the trees
are not killed but seriously weakened. This insect was prob-
ably introduced into America from China, and was first dis-
covered on some trees in an orchard near San Jose, California.
Thus it came to be popularly known as the San Jose scale.

The covering wax scale of this insect is so small and flat
and so closely resembles the color of the bark, that it makes
the insects very difficult to detect, especially when there are
only a few on a tree. On the fruit or leaves or new branches
their presence is more easily detected on account of the con-
spicuous red spot that usually surrounds them. When the
tree is badly infested the scales often form a complete crust
over the bark and branches, giving them a characteristic

446 ECONOMIC ZOOLOGY AND ENTOMOLOGY

grayish appearance. If a piece of the outer bark of the in-
fested tree is cut away the cambium will be seen to be dis-
colored by numerous red spots, which, in the case of a serious
infestation, may coalesce, staining the whole outer surface of
the cambium. The scale of the male is usually darker than
that of the female, and oblong-oval instead of circular. The

FIG. 211. — San Jose scale, Aspidiotus perniciosus, on fruit, leaves, and
stem of a pear tree. (Reduced.)

scales of the young of the male and female are alike, both being
small circular and black. The insect passes the winter in the
immature condition under these black scales on the trunk
or the branches of the tree. In the early spring the females
become mature and begin to produce living young. The young
soon make their way from underneath the scale of the mother,
and, after wandering about for a short time, settle down and

INSECTS INJURIOUS TO ORCHARD TREES 447

begin active feeding. Soon after this they begin the secre-
tion of the waxy substance which is to form their scaly
covering. Their development is very rapid and after about
thirty days they themselves begin to produce living young.
Thus there may occur from two to six generations during the
summer.

There are several kinds of parasites that are of more or less
importance in controlling the San Jose scale, but none of these
acts quickly enough to make it unnecessary to use active meas-
ures in fighting the pest. Many kinds of sprays have been
tried, but the sulphur-lime spray is the one which is now most
generally used. The directions for making and using this spray
will be found on page 416. Before spraying, the trees should
be pruned back as much as is practicable so that all of the
remaining wood may be thoroughly covered. In some re-
gions miscible oils are extensively used.

There are four or five other species of scale-insects that look
very much like the San Jose scale, and, indeed, can only be
distinguished from it by the use of the lens, but as their habits are
much the same and as the same remedies are to be used for
them they need not be especially discussed.

Oyster-shell Scale (Lepidosaphes ulmi). — As the name in-
dicates, the scale of this insect is shaped somewhat like an elon-
gate oyster shell. It is long and narrow, usually somewhat
curved toward the posterior end. The color varies from light
brown to dark brown. This is a very common pest on almost
all kinds of fruit trees, occurring also on many other trees both
cultivated and wild. As it is large enough to be easily seen
it is perhaps better known than almost any other species. It
passes the winter in the egg stage, the eggs being well protected
by the firm tough scale under which they lie. In many regions
only a single brood occurs each year, but in the South there may
be two broods. This insect is subject to the attack of several
natural enemies, among the most important of which are the
chalcid-flies, which sometimes control the pest fairly well. It
is very difficult to kill the eggs by spraying in the winter, but
if the trees are thoroughly sprayed with the sulphur-lime wash
just before the buds open most of the young will be killed soon

448 ECONOMIC ZOOLOGY AND ENTOMOLOGY

after hatching. Kerosene emulsion or whale-oil soap or other
sprays may be used just after the young hatch as they are
very easily killed before they are protected by the scale.

The Scurfy-scale (Chionaspis furfur a). — This scale is very
common on apple and pear trees, but may also attack cherry,
peach, plum and many other trees. The scale of the adult fe-
male is whitish or dirty gray, flat, and irregu-
larly ovate. The yellow exuvium is at the
narrowed anterior end. The scale of the
male is snow white, and elongate with the
sides nearly parallel. The males and the
females usually occur on different branches.
They pass the winter in the egg stage and so
are controlled by the same methods as are
recommended for the oyster-shell scale.

The European Fruit Lecanium (Lecanium
corni). — There are several species of scale-
insects that belong to the group commonly
known as Lecaniums, but as they are similar
in appearance and habits only one species
will be described. L. corni was formerly
known under many different names as it
varies somewhat in appearance under dif-
ferent conditions and on different host plants.
In many regions it is usually known as the
plum-scale. In the west it is commonly
known as the brown apricot-scale. It is
usually quite convex, sometimes almost hemi-
spherical, but often oval or even pointed at
one or both ends. The color varies from light
brown to dark brown, a medium reddish-
brown being perhaps the prevailing color.
The surface is usually shiny and often marked by fuscous
transverse or longitudinal markings and irregular pits. The
young insects may be found on the twigs and branches of the
tree during the winter time, as it passes the winter in the im-
mature stage. Any large apparently full-grown scales which
may be found during the winter are the remains of the dead

FIG. 212.— The
European fruit
Lecanium, L.
corni, on twig of
apricot tree.
(Natural size)

INSECTS INJURIOUS TO ORCHARD TREES 449

bodies of mothers that have laid their eggs early in the
summer. A small chalcid-fly is a very common parasite of
this scale and often controls it effectively when it once becomes
well established in an orchard. The parasites cannot be
depended on for absolute control, however, and spraying is
usually necessary. The sulphur-lime spray gives very good
results, but some prefer a kerosene emulsion, one part to four
parts of water, or a 5 per cent, or 6 per cent, distillate oil
emulsion. The spraying should be done in the winter in order
that the over-wintering young may be killed.

29

CHAPTER XXXIII
INSECTS AFFECTING CITRUS FRUITS

Insect pests are among the most serious obstacles to the
successful growing of citrus fruits. In spite of the fact that
California growers spend more than half a million dollars
annually in fighting the scale-insects (Coccidce) in their orange
and lemon groves, the losses caused by these pests are still
enormous. It is estimated that the Florida orange growers
would receive annually at least one-half million dollars more for
their crop if the white-fly, Aleyrodes citri, could be exterminated
in their groves.

As the attack on citrus trees is made chiefly by a few insects
that are closely related to each other, and hence are much alike
in the nature of their injurious feeding, and in their structure,
life-history and general habits, the remedies for the citrus
pests are less various than those used in the warfare against the
insect enemies of the deciduous orchards. Hence certain
generalizations can be made concerning insect attacks on citrus
fruits and concerning the remedies for them.

The injuries are chiefly caused by sap-sucking insects of the
order Hemiptera. These insects, though small, are prolific
breeders, and when once allowed a foothold in a grove increase
rapidly to enormous numbers. They suck the juices from
leaves and fruits, causing the former to wilt and the latter to be
rendered unmarketable. As most of the citrus insects secrete
honey-dew, the sooty fungus, Capnodium, whose spores ger-
minate freely in this substance, frequently grows in a close
felted mass over the attacked leaves and fruits, not only
rendering them unsightly and disagreeably dirty, but actually
seriously hurting the tree by interfering with the functions of
the leaves. The fungus closes the stomata, or breathing pores,
in the leaves, and prevents the proper exchange of gases neces-
sary to the tree's health.

450

INSECTS AFFECTING CITRUS FRUITS 45 1

The remedies for the insect pests must be such as will kill
them by external contact, or by suffocating them. The spray-
ing of arsenical poisons on the trees would have no effect, for
the food is drawn by the insects from below the surface.
Fumigation by hydrocyanic gas, the application of kerosene
emulsions or similar contact poisons, and recourse to dis-
tributing and encouraging the natural insect enemies of the
pests, are the remedies chiefly used.

The following paragraphs give brief accounts of the character
and life of a number of the more important of the pests.
They should enable those students who have opportunities to
visit orange and lemon groves to become acquainted with the
insects, and to understand the means of controlling them.
Most of the citrus fruit pests, it will be noted, are scale-insects
and, therefore, the general account of these insects given in
Chapter XXXII should be referred to in connection with
the accounts in this chapter of various species of the group.

The White-fly (Aleyrodes «><).— This is by far the most
important pest of the citrus trees in the Gulf states. The
adults are small white insects with two pairs of wings covered
with a white waxy powder, which has suggested the popular
names of "white-fly" or "mealy-wings." These insects prefer
to rest in quiet shady places, hence they are less common in dry
open groves than they are in groves where the foliage is dense
and there is considerable moisture. The eggs are laid on the
underside of the leaves, preferably on new leaves. The young
larvae are similar in appearance to young scale-insects, and
move about freely for a short time before they settle on the
underside of the leaves and begin feeding. As they are
whitish-green in color and translucent they are hard to see.
The pupal stage, which is entered a few weeks later, is similar
in appearance to the later larval stages. There are usually
three broods during the year. As the undersides of the leaves
are often almost completely covered with these pests the
injury that they may do by sucking the juices from the leaf
tissues is often very great. Perhaps the greatest injury, how-
ever, is caused by the sooty mould that grows in the honey-dew
that is secreted by these insects. This honey-dew drops on the

452 ECONOMIC ZOOLOGY AND ENTOMOLOGY

leaves and fruit, and the fungus growing in it forms a thin
covering that seriously interferes with the function of the leaf
and very materially damages the fruit.

Certain fungus diseases that attack the white-flies often
control them quite effectually but it is sometimes necessary to
resort to spraying. The resin wash has been much used. A
spray made by thoroughly emulsifying two gallons of paraffine
oil with one gallon of whale-oil soap and one gallon of water is
strongly recommended. One gallon of the stock emulsion
should be used in fifty gallons of water. December, January,
and February are the best months to spray for these insects, as
practically all of them are then in the larval stage. As it is
very difficult to reach thoroughly all of the foliage on an orange
or lemon tree with any spray mixture, it is much more satis-
factory, where possible, to fumigate with hydrocyanic acid gas.
If properly done at the season suggested for spraying, it will
effectively control the white-fly.

There are two other species of white-fly, A. nubifera, and A.
howardi, affecting citrus trees, but they are similar in appear-
ance and habits to A . citri.

Black Scale (Saissetia olea). — This is perhaps the most
important scale-insect on the orange trees of the Pacific
Coast, not so much on account of the direct injury caused by
the loss of sap, which the myriads of insects are con-
stantly drawing from the leaves and branches, but because,
like the white-fly, it secretes a great deal of honey-dew in which
a sooty mould grows. This is an insect widely spread over the
world and long known as a pest of olives and oleanders. The
adult female is almost hemispherical in shape, a little longer
than broad, hard or leathery in texture and dark brown or
black in color. The younger stages are flatter and on the
dorsal side are marked by one longitudinal and two transverse
ridges, forming the letter "H." The adult also shows this H,
but less plainly. The black scale is not nearly as serious a pest
in the Gulf region as it is on the Pacific Coast.

In 1900 there was introduced into California a small Hymen-
opterous parasite, Scutellista cyanea, of the black scale that
has proved to be, in some localities at least, an important factor

INSECTS AFFECTING CITRUS FRUITS 453

in its control. Sometimes as high as 80 per cent, of the scales
will show the small hole whence the adult parasite has escaped
from its host. Yet the numbers of living scales that are left are
great enough often to make it necessary to use some artificial
methods of control. Most growers rely on fumigation to con-
trol this pest, but in some cases, especially in the case of young
trees, it is practical to spray. The kerosene sprays discussed
on page 416, have been found most satisfactory.

FIG. 213. — Black scale,
Saissetia olea, on orange
twig. (Slightly en-
larged.)

FIG. 214. — Young of black scale,
Saissetia olece. (About seventy times
natural size; after Quayle, photo by
Doane.)

The hemispherical scale, S. hemispharica, looks very much
like the black scale, but the dorsal surface is smooth and shining
and does not have the ridges that form the letter H. It is
often found on citrus trees out of doors, but is a more common
pest in greenhouses, where it attacks many kinds of plants.
The soft brown scale, Coccus hesperidum, is also sometimes

454 ECONOMIC ZOOLOGY AND ENTOMOLOGY

associated with the black scale, but is easily distinguished be-
cause of its reddish-brown or yellowish color and by minute
darker spots or bars on its dorsal surface which may form more
or less distinct radiating lines. It is elongate oval in shape.
It is often very abundant on the trees, where it does con-
siderable damage by taking sap from the plant. This species
is attacked by three or four kinds of internal parasites that
usually keep it well in control, so that the grower does not often
have to resort to sprays or fumigation.

The Red Scale of California (Chrysomphalus auranti.}—
This is one of the most destructive scale insects in California.

FIG. 215. — Red scale, Chrysomphalus duranti, on lemon leaf. (Enlarged;
after Quayle, photo by Doane.)

Unlike the black scale it does not secrete the honey-dew in
which the sooty mold grows, but the direct effect of the attack
on the tree is much more serious. It attacks all parts of the
tree, trunk, branches, twigs, leaves and fruit. The trees are
often killed within two or three years after the first infestation
if they are not properly cared for. Even when the insects

INSECTS AFFECTING CITRUS FRUITS 455

are not abundant enough to injure the tree seriously they may
cause considerable loss by their presence on the fruit. Atten-
tion is usually called to the pest by the presence of small light
yellowish spots on the leaves. The scale of the female is
almost circular in outline, very flat, and about one-thirty-sec-
ond to one-sixteenth of an inch in diameter. The scale of the
male is more elongate. This insect increases in numbers so
rapidly that although it is attacked by several natural enemies
it is necessary to take active measures early to control it when
it gains a foothold in the orchard. Fumigation is the most
practical remedy.

The yellow scale, a variety of the red scale, is very similar in
appearance and habits to the red scale, and is only distin-
guished from it by its lighter color. It confines its attacks to
the leaves and fruit, seldom attacking the twigs or branches.

The red scale of Florida, C. aonidum, is similar in appearance
to the red scale of California, but the waxen cover is heavier
and darker, usually reddish-brown or almost black with a
whitish spot in the center. It is of little importance as an
enemy of citrus trees, but is often a serious pest in greenhouses.

The Purple Scale (Lepidosaphes becki). — In general ap-
pearance this scale is very much like the oyster-shell scale that
occurs on the apple trees. It attacks all parts of the trees,
the leaves, branches, trunk and fruit frequently becoming
entirely covered by the pest. It may cause the leaves or fruit
to drop, or may even kill part of the tree, but it. seldom kills
the entire tree and so is not as serious a pest as the red scale.
It occurs in destructive numbers throughout the citrus regions
of Florida and the Gulf states and in certain sections of Califor-
nia. The female insect occupies only the anterior portion of the
scale, the posterior portion being full of eggs and growing to
meet the requirements as more eggs are produced. The young,
soon after hatching, make their way from beneath the pro-
tecting scale, settle on the plant, and begin secreting the waxy
substance that is to form their scale-like covering. It is
toward the destruction of these younger scales that the
orchardist must direct his attention, for the old insects are so
well protected that it is difficult to kill them with any ordinary

456 ECONOMIC ZOOLOGY AND ENTOMOLOGY

spray or even by fumigation, nor will the fumigation affect
the eggs. On badly infested trees it is usually necessary to
give two treatments, the second about six weeks or two
months later than the first, in order that the young which
hatch after the first treatment may be killed. The dosage
used in fumigating for the purple scale is one-fourth to one-
third stronger than that used for the red scale.

FIG. 216. — Purple scale, Lepidosaphes becki. (Much enlarged; after
Quayle, photo by Doane.)

Glover's Scale (Lepidosaphes gloveri). — The waxen scale of
this insect resembles that of the purple scale, but is longer and
narrower and less curved, hence it is often known as the long
scale. It is a serious pest in Florida and the Gulf region, but has
never become a pest in California. The life history and habits
are much the same as those of the purple scale, and the remedies
to be used are the same.

The Chaff Scale (Parlatoria pergandi) . — The scales covering
the females of this species are whitish, rounded or oval, with
the molted skin close to one margin. The scale of the male
is similar, but more elongate. They are usually found on the
trunk and branches of the tree, but may also occur on the

INSECTS AFFECTING CITRUS FRUITS 457

fruit. The insect is destructive to citrus trees in Florida and
the other Gulf states, but does not occur in California. It is
very often found as a pest in greenhouses in many sections of
the United States. When the scales occur on parts of the
tree that can readily be reached with sprays they may be com-
paratively easily controlled by spraying with kerosene emul-
sion; otherwise, fumigation should be resorted to.

The Mealy-bug (Pseudococcus citri}. — This insect is one of
those kinds of Coccidce that are unprotected by any scaly
covering. The body is covered with
a mealy or flocculent waxy secretion
which, on the sides, takes the form
of short waxy filaments. The two
posterior filaments are two or three
times as long as those on the sides.
The insects are active during all the
stages of their development until the
female begins to secrete the loose,
fluffy, cottony mass that serves to
protect the eggs. The females may
begin laying eggs when they are only
five or six weeks old, and as each fe-
male will lay from three to four hun-
dred eggs the number of individuals

in a colony increases very rapidly. fseMococctacunf ^reauy
They may attack any part ol the enlarged; after Quayle,
tree, but are usualy found in pro- photo by Doane.)
tected places, such as the base of

the leaves, in the navel of the orange, or in places where the
leaves or the fruit touch each other or some other object. These
insects secrete considerable honey-dew, which is so very sticky
that it takes much washing and brushing to remove it and the
smutty fungus that grows on it from the fruit. Aside from
the cost of the labor required to clean the fruit, this washing
is undesirable because it affects the keeping qualities of the
oranges and lemons.

On account of their habit of hiding away in protected places,
and because the cottony secretion that covers them is so hard

458 ECONOMIC ZOOLOGY AND ENTOMOLOGY

to penetrate, mealy-bugs are among the most dreaded pests in
the orange and lemon orchards. Any of the sprays used at
ordinary strength will leave many of them unharmed. A strong
carbolic acid spray, made as suggested on page 417 and applied
under a very high pressure, is the most efficient remedy yet
found. Two or three or even more applications are often
necessary before the insects can all be destroyed. Fumiga-

FIG. 218. — Mealy-bugs, Pseudococcus citri, on lemons. (Reduced,- after
Quayle, photo by Doane.)

tion as ordinarily used on citrus trees does not kill nearly all
of the mealy-bugs, and for this reason has not proved as satis-
factory as some of the sprays.

The mealy-bugs are attacked by several parasites and pre-
daceous insects. The ladybird-beetles are particularly im-
portant in the control of this pest. The larvae of one of these
little beetles, Cryptolcemus montrouzieri, is covered with
cottony tufts making it look very much like the mealy-bug

INSECTS AFFECTING CITRUS FRUITS

459

as it feeds among them. The larvae of lace-wing flies and
syrphus-flies also destroy many mealy-bugs.

The Cottony-cushion Scale (I eery a purchast).—This insect
was at one time the most serious pest of the citrus fruits in
California where it destroyed many groves of citrus trees and

FIG. 219. — Cottony-cushion scale, Icerya purchasi, on orange tree. A
few young are seen on the white egg sacs. (About natural size; after
Quayle, photo by Doane.)

many ornamental plants. It has not appeared in destructive
numbers in other parts of the United States. It was intro-
duced into California from Australia about 1868, and within
ten years had become very abundant and destructive, particu-
larly in the southern part of the state. For some years the
orange and lemon growers fought against it unsuccessfully.

460 ECONOMIC ZOOLOGY AND ENTOMOLOGY

Finally an entomologist was sent to Australia to study the pest
in its native home and see if some natural enemy could not
be found that would help to control it. Among other things
that he sent back were colonies of the small ladybird-beetle
now commonly known as the Australian ladybird, Novius
( Vedalia) cardinalis, and within a remarkably short time this
little beetle, both the larvae and adults of which feed exclu-
sively upon this scale, had so reduced the numbers of the pest
that it was practically under control, and since that time the
cottony-cushion scale has not been regarded as a serious pest.
As soon as it appears in considerable numbers on any trees
or plants some of the twigs or branches are cut off and sent
to the State Horticultural Commissioner who in return sends
out a small colony of the ladybird-beetles, if he finds that they
are not already present among the specimens that are sent in.
The large cottony egg sac of the female scale is longitudinally
ribbed or fluted, and is a conspicuous object that is not likely
to be mistaken for any other insect. The young are some-
times found on the leaves where they are easily recognized by
the light cottony secretion and the large glass-like filaments
that project from parts of the body. As the ladybird-beetles
keep it so well in control it is rarely necessary to take any other
measures to combat it.

Florida Wax -scale (Ceroplastes floridensis] . — Although this
insect seldom appears in great numbers on the orange or lemon
trees, its striking appearance, when it is present at all, at
once attracts attention to it and sometimes occasions consider-
able needless alarm. The young, which are seen on citrus trees
more commonly than the adults, are covered with a white waxy
secretion that radiates from the center so that the very young
insect looks like a small oval white star. As the insect grows
older the waxy covering becomes more or less distinctly
separated into six or eight plates. The color is white with a
pinkish tinge.

The Barnacle -scale (C. cirripedijormis), looks somewhat
like the preceding but is much larger and the waxy plates
are more distinctly marked, each plate being mottled with
grayish or light brown. As these insects rarely become at

INSECTS AFFECTING CITRUS FRUITS 461

all abundant it is seldom necessary to use any methods of
control.

The Orange Thrips (Euthrlps citri}.— Within the last few
years certain thrips have been doing considerable damage to

(the oranges in some parts of California. They usually
work around the stem or depressions in the skin, making dis-
tinct whitish marks which, while not affecting the edible
qualities of the fruit, seriously affect its market value, as such
fruit cannot be graded as first class. The insects themselves
are very minute, and are seldom noticed unless looked for very
carefully. Spraying is the most satisfactory means of con-
trol. The sulphur-lime spray (see page 415) is the one most
commonly used. It is necessary to use great care to reach
all parts of the tree, and a high pressure is essential. There
are other species of thrips that attack the orange, but their
habits are the same and they yield to the same methods of
control.

There are several other orange pests, such as Fuller's rose
beetle, Aramigus fullerl, and the diabrotica beetle, Diabrotica
soror, which feed on the leaves, doing particular damage to
young shoots or to new grafts. The red and silver mites are
referred to on page 213. The larvae of certain moths attack
the fruit and sometimes the leaves also, but these are usually
of little importance.

The Mexican Orange Maggot (Trypeta ludens). — This insect
has not yet established itself in the United States. It is, how-
ever, a serious pest of oranges in Mexico, and there is always a
possibility of its gaining an entrance into this country in spite
of the strict quarantine which is established against it. The
larvae, or maggots, feed in the pulp of the orange. When
fully developed the larvae enter the ground and pupate. The
adult fly is yellowish in color, and has transparent wings
marked with brownish bands.

CHAPTER XXXIV
INSECTS INJURIOUS TO VINEYARDS AND BERRIES

The small fruits have their insect enemies no less than the or-
chard fruits. Grapes, currants, berries, all have a constant
struggle against insect pests, and call for our help in no uncer-
tain tones. A quarter of a century ago the enormously valu-
able vineyards of France seemed to be on the point of total
destruction from the insidious attacks of a minute soft-bodied
delicate-winged aphid, the grape phylloxera, that carried on
most of its deadly work underground and hence was hardly
visible to the appalled vineyardists. And later, in the exten-
sive vineyards of California a similar tale of destruction began
to be told. The French government offered a great reward to
any one who should devise an effective remedy for the pest, and
scores of entomologists gave their whole time to the study of the
life of the insect. Finally it was found that certain American
wild grapes had developed a natural resistance or immunity to
the attacks of the pest, and grape-growing was revolutionized
by the adoption of the practice of grafting the valuable but deli-
cate wine grape kinds on to the strong resistant wild roots. As
the kind of fruit is determined by the graft and not by the stock
this combination has proved the saving of the great vine indus-
try of Europe and California.

Among the other grape pests are several kinds of beetles, the
adults of which eat the leaves while their larvae attack the roots,
leaf-hoppers which take sap from the leaves and tendrils by
means of their sharp little piercing and sucking beak, and the
larvae of certain small moths which eat both leaves and the
grapes themselves.

Among the more important enemies of raspberries and black-
berries are the active, strong-jawed larvae of certain clear-
winged moths (Sesiidte) and certain beetles. These are vari-
ously called cane-borers, crown-borers and root-borers because

462

INSECTS INJURIOUS TO BERRIES 463

they mine the plants in these various parts of it. Scale-insects
and slugs (larvae of saw-flies) also do much damage.

Currants and gooseberries suffer from cane-borers, slugs,
aphids and scale-insects, and from the effective girdling opera-
tions of a saw-fly that attacks the stems. Certain flies lay
their eggs in the berries, and the hatching larvae burrow in and
feed on the pulp and seeds

Strawberries have an unusual number of insect enemies,
including weevils, aphids and the boring larvae of various moths
and beetles.

For all these various pests remedies have to be devised with
special care and ingenuity because of the tenderness of the
plants and the fact that it is the berries themselves which are
so often attacked and which, of course, cannot be poisoned.
Careful pruning of partly infested plants and the complete
cutting out and burning of more seriously attacked plants are
largely resorted to by berry growers. However, arsenical
sprays and emulsions of whale-oil soap and kerosene have their
place in the fighting, as well as a number of special remedies
applicable to the particular conditions under which berries are
grown.

Students in any locality will have no difficulty in getting per-
sonally acquainted with some, at least, of the most important of
the grape and berry pests described in the following paragraphs.
For accounts of others, government and state bulletins, horti-
cultural books and manuals of injurious insects may be re-
ferred to.

GRAPES

The Grape-vine Phylloxera (Phylloxera vastatrix) . — The in-
sect referred to in the first paragraph of this chapter is a small
brownish plant-louse or aphid, which is commonly called by its
generic name, phylloxera. It may occur in four different
forms. During the fall there appears a sexual generation
which lays the winter eggs under the rough bark of the vine.
These hatch early in the spring, and some of the young aphids
crawl out to the leaves where they produce small but conspicu-
ous reddish galls. This leaf feeding form rarely occurs on the

464 ECONOMIC ZOOLOGY AND ENTOMOLOGY

European varieties of grapes, and probably does not occur at
all in California. Most of the young which hatch from the
winter eggs crawl down to the roots, where their feeding causes
small cancerous swellings or galls. Generation after genera-
tion of wingless individuals may be produced on the roots with-
out any winged or sexual forms appearing, so that the whole
root system may soon become badly infested. As the at-

FIG. 2 20. — The grape phylloxera, Phylloxera vastatrix. In the upper
left-hand corner an egg from which a male has issued, next an egg from
which a female has issued; in upper right-hand corner, winter egg; at left-
hand of middle row, a just-hatched young, next a male (note absence of
mouth-parts); at right end of middle row, female; lower figure, winged
form. (Much enlarged; after Ritter and Riibsaamen.)

tacked roots soon decay, the vitality of the vine is seriously
affected and it usually dies within a short time. Sometimes,
during the summer, a winged generation of females may appear.
These make their way to the surface, fly to other plants and lay
eggs there of two sizes. The smaller of these eggs produce the
males and the larger the females of the sexual generation that
lays the winter eggs.

INSECTS INJURIOUS TO BERRIES 465

No satisfactory remedies for controlling the pest in badly at-
tacked vineyards have yet been found. Carbon bisulphide is
sometimes introduced into the ground around the vines and
many of the root-inhabiting aphids thus destroyed. Flooding
has been resorted to in some regions, but such methods are either
too expensive or are possible only in certain localities. When
any of the vines are found to be unthrifty or dying, the roots
should be examined carefully and, if the insect is found, all of
the vines in the affected portion of the vineyard should be dug
out and burned.

But the principal remedy for the phylloxera is the replanting
of the vineyard on "resistant" roots. The pest is a native
of America, and the wild grapes of this country have come to be
naturally immune, or resistant, to the attacks of the insect.
Grafting the European cultivated varieties on to the wild or
only slightly modified American varieties is therefore an effect-
ive means of escaping the ravages of the pest.

Phylloxera was first made known in New York in 1853, and
was soon discovered to be well scattered over the wild vines in the
eastern United States. It was introduced into France about
1863, and increased with such rapidity that in twenty years it
had destroyed more than one-third of all the vineyards of that
country and had affected most of the others. It was intro-
duced into California, where French varieties of grapes are
largely grown, about 1874, and by 1900 many thousands of
acres of vineyards had been destroyed. The vineyards of both
Europe and California are now chiefly planted on resistant
roots.

The Grape-root Worm (Fidia viticida). — The adult of this
insect is a chestnut-brown beetle that appears on the vines
about the close of the blooming season and begins feeding on
the leaves. The series of cell-like holes or chain-like markings
which it makes in the leaves are usually the first thing to
attract the attention of the grower to the fact that these little
pests are in his vineyard. The young larvae which hatch from
the eggs, that are deposited on the inner bark or in crevices of
the vine, make their way into the ground and begin feeding on
the roots. If they are abundant they may destroy many of the

466 ECONOMIC ZOOLOGY AND ENTOMOLOGY

smaller rootlets and may even injure the larger roots by eating
off the bark. They lie dormant during the winter, and come
near the surface early in the spring to pupate.

Deep cultivation late in the fall or early in the spring will
destroy many of the larvae and pupae. A thorough spraying
with arsenate of lead as soon as the beetles appear will destroy
many of them, but a second spraying may be necessary a little
later.

The Imported Grape-root Worm (Adoxus mtis), which occurs
in California, has habits similar to the eastern species just
described, and yields to the same treatment.

The Grape-vine Flea-beetles (Haltica spp.). — These are
small, shining, green or dark blue beetles, characterized by their
strongly developed hind legs which enable them to leap for
considerable distances. The rose-chafer, Macrodactylus sub-
spinosus, slender bodied and with long slender spiny legs, is
another beetle that feeds on the foliage of the grape. In spray-
ing for these various beetles the work must be done early, and
it is often advisable to add glucose or molasses to the arsenate
of lead (see page 415.)

The Grape-berry Moth (Polychrosis viteana), and the grape
curculio, Capronius inaqualis, the larvae of both of which feed
on the foliage but do more damage by attacking the fruits, may
be controlled by similar arsenical sprays.

The Grape Leaf -hopper (Typhlocyba comes). — This is a very
widely distributed pest of the vines, and has come to be known
by many common names, such as leaf-hopper, vine-hopper,
vine-thrips or thrips, but as it is not a thrips at all, and as there
are several other kinds of leaf-hoppers, it is better to call it the
grape leaf-hopper. The adults are about one-eighth of an inch
long, with the body and wings prettily marked with red or
yellowish bands or spots. The over-wintering adults appear
on the vines as soon as the buds open, and a little later lay their
eggs beneath the epidermis of the underside of the leaf. The
young are small, whitish, wingless insects with conspicuous
red eyes, but become more and more like the adult with each
molt. In some regions there is only one generation each year,
but in other places there may be a partial or even a full second

INSECTS INJURIOUS TO BERRIES 467

generation. Adults hibernate in leaves or rubbish in the vine-
yard or along the fences or in near-by fields or meadows, and if
such places are burned over during late fall or winter these
hibernating adults may be destroyed.

When the insects attack the vines they may be more or
less successfully controlled by spraying with some contact
insecticide, such as whale-oil soap, kerosene emulsion, or
resin spray (see page 417). An undershot nozzle must be
used and great care taken to reach the underside of all the
leaves. In California and other places where the vines are
pruned back close to the main trunk each year, a hopper cage
made by fastening fine wire screen, such as mosquito netting,
over a frame may often be used with
success. One side of the cage is left
open and the bottom is made of a
shallow tray with a U-shaped opening
so that the cage may be pushed over
the vine. The sides of the tray are
smeared with crude oil so that the
hoppers that fly from the vine when FlG 22I._Grape leaf-
it is jarred are caught and killed in hoppers, at left Typhlocyba
this material. When the vines are v^erata, on right T comes.
, , , e ... (Much enlarged: after

not pruned back, of course, this cage Forbes.)

cannot be used. In such places sticky

shields against which the leaf-hoppers are likely to jump when
two men are carrying them on opposite sides of the vines, may
catch and destroy large numbers of these pests.

RASPBERRIES AND BLACKBERRIES

The most serious pests of raspberries and blackberries are the
borers that attack the canes. The raspberry root-borer, Bem-
becia marginata, also called the raspberry crown-borer, usually
attacks the plant below the surface of the ground, sometimes
girdling and killing it, but it may sometimes leave the roots
and bore into the canes. The adult insects are beautiful clear-
winged moths related to the peach-tree borer and the

468 ECONOMIC ZOOLOGY AND ENTOMOLOGY

currant-borers. The aflected plants should be dug up and
burned.

The Raspberry Cane-borer (Oberea bimaculata) , the adult of
which is a slender cylindrical beetle about one-half an inch
long with antennae about as long as the body, and the red-
necked cane-borer, Agrilus ruficollis, the larvae of a flat blackish
or bronze-colored beetle with a red prothorax, both attack
the canes of raspberries and blackberries. The larvae of a
fly that looks very much like a small house-fly also often
destroy many of the new shoots.

In all these cases affected canes should
be cut out and destroyed as soon as no-
ticed.

Scale-insects. — Among the scale-insects
which often attack the raspberry and
blackberry vines, the rose-scale, Aulacaspis
rosce, is perhaps the most common. Atten-
tion is usually attracted to the presence of
this insect by the white elongate scales of
the males which often occur in such num-
bers as to make the canes look as if they
had been whitewashed. The scale of the
female is circular and somewhat darker.

The badly infested canes should be cut
out and the others sprayed with the sul-
phur-lime wash during the winter.

Such leaf-feeding insects as the raspberry
sa,w-fty,Monophadnoidesrubi, and the rasp-
berry Byturus, Byturus ttnicolor, may be
controlled by spraying with arsenate of
lead, if the application is made before the
berries form. If the slug-like larvae of saw-flies appear later,
white hellebore may be sprayed or dusted on the plants. A
little greenish or brownish mite, Bryobia pratensis, referred
to on page 212, often occurs in destructive numbers on the
raspberry leaves causing them to turn yellow and fall.
Thorough sprayings or dustings with sulphur will usually
control them.

FIG. 222. — Rose
scale, Aulacaspis
rosa, on blackberry
bush. (About nat-
ural size.)

INSECTS INJURIOUS TO BERRIES

469

CURRANTS AND GOOSEBERRIES

As with the raspberries and blackberries the cane-borers are
the most important enemies of the currant and gooseberry
bushes.

The Imported Currant-borer (JEgeria tipuliformis}. — In
appearance and habits this insect is much like the raspberry
root-borer, but it works in the canes above the ground and
not in the crown or roots. The eggs are laid in the axils of
the leaves or on the currant canes, the larvae boring into the
canes as soon as they are hatched. During the winter the
half-grown larvae may be found in the center of the cane at
the bottom of the burrow where
they have been working. Early
in the spring they commence to
work again, pupating in May.
The adult moths issue in June.

The leaves of the affected canes
are lighter or yellowish in color,
thus enabling one to detect and
prune out the affected parts of
the bush. All dead or affected
wood should be cut out and de-
stroyed as early as possible.

The Currant-stem Girdler

(J anus integer] . — This is a small, slender, shining black saw-
fly that girdles the currant canes just above the point where
she lays her eggs.

As the first indication of the presence of the pest is the
dying tips that have been girdled, nothing can be done to check
the damage that season, but if the affected stalks are cut off
three or four inches below where they were girdled the larvae,
which are lying in the stalks, may be destroyed. If the prun-
ing is left until winter time the cut should be made eight or
nine inches below the dead end of the cane.

The Currant Saw-flies (Pteronus ribesi and Gymnonychus
appendiculatus). — 'The larvae of these saw-flies, which feed on the
foliage, and any other leaf-feeding larvae may be controlled by

FIG. 223. — Imported currant-
borer, Mgeria tipuliformis,
adult. (About natural size.)

470 ECONOMIC ZOOLOGY AND ENTOMOLOGY

spraying with arsenate of lead while there is no fruit on the
bushes. At other times white hellebore should be dusted
or sprayed over the plants.

The Currant Aphis (Myzus ribis}. — In the spring or early
summer the leaves of the currant bushes, and less frequently
the gooseberry bushes, become more or less blistered and swollen
and curled. The distorted parts are usually conspicuously
red in color and soon attract attention. Examination will
reveal colonies of small yellowish-green aphids on the under-
side of the leaves.

When only a few of the leaves are affected they should be
picked off and destroyed. Spraying with kerosene emulsion
or whale-oil soap or tobacco extract is effective if care is taken
to reach the aphids before they have become well protected
by the curling of the leaves. If the bushes are sprayed during
the winter with sulphur-lime solution many of the eggs will be
destroyed.

Scale -insects. — Several different species of scale-insects, the
most important of which is the San Jose scale (see page 445),
often attack the currant and gooseberry bushes and sometimes
prove very destructive. The best remedy is to prune out the
parts that are badly infested and spray the rest with sulphur-
lime solution during the winter.

The Yellow Currant-fly (Epochra canadensis}. — This fly is
about the size of the house-fly, but the body is more slender
and the wings are longer and narrower. The body and legs
are pale yellow or brownish and the wings are marked with
brownish cross bands. This insect passes the winter in the
pupal stage in the ground or in rubbish below the bushes.
The flies issue early in the spring and the females deposit
their eggs in the berries just underneath the skin. The larvae
feed upon the pulp and seeds, and when full grown they leave
the berries, which have dropped to the ground, and enter
the ground to pupate. These fallen berries should, if possible,
be destroyed before the larva? leave them. If chickens are
allowed to run under the bushes they will pick up many of
the larvaa and pupa3. An effective but rather expensive way to
save the crop of berries is to cover the entire bush with mosquito

INSECTS INJURIOUS TO BERRIES

netting taking care to tie it carefully around the bottom. If
this is done just after the berries have formed, and before the
flies appear, none of the berries can become infested.

A radical remedy is to destroy all of the fruit while it is
quite small before any of the larvae have had a chance to pupate.
Thus by the loss of one crop all the flies in the garden will be
destroyed, and reinfestation can only come from a neighbor's
field. As the flies do not often fly far from the bushes this in-
festation will come but slowly.

FIG. 224. — Yellow currant-fly, Epochra canadensis, laying eggs on currants
(Somewhat enlarged; photo by Paine.)

The Dark Currant-fly (Rhagoletis ribicola). — This fly is not
as well known as the preceding species, but in the state of
Washington and other places it is often very abundant and
destructive. The adult is only about half as large as a house-
fly. The body is shining black, the thorax marked by four
narrow yellow lines and a conspicuous yellow spot. The
wings are marked with four broad, brown cross bands, the
outer pair of which are united anteriorly. The habits are
similar to those of the preceding species, and the control
measures the same.

472 ECONOMIC ZOOLOGY AND ENTOMOLOGY

STRAWBERRIES

The Strawberry Crown-borer (Tyloderma jr agarics). — The
white grub-like larvae of this beetle often cause the death of
many plants by boring into the crown and eating out a large
cavity. The dark-colored adult is about one-fifth of an inch
long, and belongs to the group of snout beetles, having the head
produced into a conspicuous blunt snout. The beetles pass the

FIG. 225. — Larvas of strawberry crown-moth, Sesia niiilans, in crown of
strawberry plant. (Somewhat reduced.)

winter in the soil, emerging in the spring to lay their eggs on
the plants. All dead or weakened plants should be dug out and
destroyed as soon as noticed. As soon as a bed becomes
badly infested it should be plowed up and a new one planted
elsewhere, care being taken to use young plants that contain
no eggs or larvae of this pest. As the beetles cannot fly the new
bed will not be readily infested.

INSECTS INJURIOUS TO BERRIES 473

The Strawberry Crown-moth (Sesia rutilans).— On the
Pacific Coast the strawberry crown-borer does not occur, but
in its stead is another pest that works in much the same way
and is even more destructive. This is called the strawberry
crown-moth. The moths are a beautiful steel-blue or black.
The adults lay their eggs on the crown of the plant early in
the summer, and as the larvae develop they bore deeper and
deeper into the crown of the plant, sometimes penetrating
the larger roots. They may feed on the plants all winter,
changing to the pupae early in the summer.

The control measures suggested for the preceding species
should be used in fighting this insect. Care must be taken
to remove all of the crown and the large roots, or the larvae
will be left in the ground.

The Strawberry Weevil (Anthonomus signatus). — These
little snout beetles appear in the strawberry patch early in the
spring and gnaw small holes through the outer crust of the
nearly mature buds where they deposit their eggs. They then
cut the stem so that the bud soon falls to the ground. Where
this pest is bad, only enough of the staminate varieties of
vines should be grown to insure good fertilization, as the
larvae feed on the pollen of these plants. It may even prove
profitable in some instances to plant early blooming staminate
varieties in places where the beetles may readily gain access
to them, and then destroy the plants after the beetles have
laid all their eggs and before the adults of the next generation
issue. Clean culture is important in order that the beetles
may have few places in which to hibernate.

Strawberry Root-worms. — The larvae of three or more species
of beetles may be found on the roots of the strawberries, some-
times entering the crown also. The adult beetles are leaf
feeders, and may be controlled by spraying with arsenate of
lead. Where the roots are badly infested they should be dug
out and burned.

The Strawberry Root-louse (Aphis forbesi). — Early in the
spring a few small greenish aphids may be found on the
underside of the strawberry leaves. Late in April or early in
June ants begin to appear on the vines in considerable numbers,

474 ECONOMIC ZOOLOGY AND ENTOMOLOGY

and soon after this, if the roots of the plants are examined, the
aphids will be found there also. The ants have carried the
aphids from their nests to the roots, where they continue to
care for them, taking them to new plants when the old plants
die or become overcrowded. During the summer winged
generations of the aphids appear, and thus distribute the species
over wider areas. Late in the fall the winged sexual generation
occurs, and the eggs are laid on the underside of the leaves,
where they remain until they hatch in the following spring.
Little can be done to control the aphids on the roots of the
plants. If the bed is badly infested the vines should be lightly
covered with straw early in the spring and the whole area
burned over. This will burn all the leaves and stems and
destroy all the aphids as well as many other insects. A quick,
hot fire will not seriously injure the plants. Care should be
taken in selecting plants for transplanting to see that there are
no eggs on the leaves nor aphids on the roots.

CHAPTER XXXV
INSECTS INJURIOUS TO GARDEN TRUCK

Only the market gardener and those who have tried to raise
a few vegetables in their own kitchen gardens realize how many
and how vexing are the insect pests of garden truck. The an-
nual value of the truck crops in the United States is estimated
to be more than three hundred million dollars, and yet each
year the insects take about one-fifth of the vegetable crops,
causing a loss, therefore, of more than sixty million dollars.

The garden pests, like those of the orchards and grain fields,
are various in kind and life-history and in the manner in which
they work their injuries. Leaf-eating beetles are especially
numerous and serious in their attacks. The black and yellow
striped Colorado potato-beetle, the active, leaping, little flea-
beetles and the spotted and striped Diabroticas are conspicuous
and familiar examples of these leaf-eaters. The caterpillars
of various moths and butterflies also strip or mutilate the
leaves of many vegetables. Cut-worms and army-worms are
notorious pests of this kind. The naked green cabbage-worm,
which is the larva of a dainty white butterfly imported from
Europe half a century ago, is an especially serious caterpillar
enemy of cabbages and other cruciferous garden plants. Several
species of aphids often occur in sufficient numbers to do serious
damage to peas, beets, cabbages and other vegetables. Squash-
bugs, the harlequin cabbage-bugs, certain leaf-hoppers and
other sucking bugs of the order Hemiptera take a heavy toll
of plant sap from many garden plants.

The remedies for garden pests have to be, like those for the
pests of vineyards and berries, especially devised to fit the
particular conditions of vegetable growing. Not many kinds
of garden truck can be sprayed with arsenical poisons, although
some, of course, notably potato plants, can. Such simple

475

476 ECONOMIC ZOOLOGY AND ENTOMOLOGY

but often sufficient means as hand-picking and trapping can be
effectually used, especially in smaller gardens. Clean cultiva-
tion and the destroying of all hiding, places for over- wintering
insects are great helps in the struggle.

Various special remedies are described in the accounts, which
follow, of a few of the more important of the garden truck
pests.

POTATOES

The Colorado Potato -beetle (Leptinotarsa decemlineata). —
This beetle is in many regions the best known of all the garden
pests. Its black and yellowish striped wings make it a

FIG. 226. — Colorado potato-beetle, Leptinotarsa decemlineata, and its
larva. (About twice natural size.)

conspicuous object on the vines, and the results of its work are
all too evident. It furnishes a good example of the way in
which an insect once regarded as harmless may, by a slight
change in its habits, become of very great economic im-
portance. Originally it fed on various common weeds, es-
pecially the Colorado thistle, Solanum rostratum, in Colorado
and other Rocky Mountain states. When potatoes (another
species of Solanum) began to be planted in the region where
the beetle occurred it found them more to its liking, and with
the abundance of food that could be had with little or no effort,
it so increased in numbers and spread so rapidly that it soon

INSECTS INJURIOUS TO GARDEN TRUCK 477

became a most formidable foe, whose destructive work was
checked only when we learned to use Paris green.

The beetles pass the winter in the ground, appearing in the
spring as soon as the potatoes begin to grow. When the insects
are abundant they may entirely destroy the young plants.
The eggs are laid on the leaves, and the larvae, which appear a
little later, also attack the plants. There may be two or even
three generations during the year. The insect has many ene-
mies, the most important of which are certain tachina-flies,
which lay their eggs on the larvae, and certain predaceous insects
which feed on the eggs or larvae. In small patches the beetles,
larvae and eggs may be gathered from the vines and destroyed.
Larger areas should be sprayed with Paris green or arsenate of
lead, most growers now preferring the latter. It is used at the
rate of three to five pounds to fifty gallons of water, the stronger
spray being used for the beetles, the weaker for the larvae.

Flea-beetles (Epitrix spp). — There are several species of
flea-beetles that occur in the garden, attacking almost all kinds
of plants. These are all small dark beetles that leap quickly
when disturbed. They pass the winter in leaves or rubbish
in the garden or along the fences, and early in the spring attack
the young plants as soon as they appear above the ground.
Particular damage may be done to potatoes by the minute
whitish larvae which sometimes feed on the tubers, making
discolored little holes in them that detract from their market
value.

If the plants are thoroughly sprayed very early with arsenate
of lead most of the beetles may be destroyed. Bordeaux mix-
ture seems to act as a repellent, so it is often worth while to use
it and lead arsenate combined. When the tubers are infested
by the larvae they should be dug up as soon as they are mature
and exposed to the sun for a few hours before storing.

Potato Stalk-borer (Trichobaris trinotata) . — This is a small
whitish grub that bores into the potato stalks, weakening or
entirely destroying them. The pupa is formed in the vine
near the surface of the ground, and the small grayish snout
beetle, which issues a little later, remains there all winter. This
suggests an efficient remedy. The vines should be raked up

478 ECONOMIC ZOOLOGY AND ENTOMOLOGY

and burned as soon as the potatoes are dug. These beetles
feed on several different kinds of weeds so that any weeds
in and near the garden should also be destroyed.

There is also another borer, the larva of the moth Papaipema
nitella, that attacks potato stalks as well as tomatoes, corn,
and many other plants. The larva? pupate in the lower
part of the stalk; therefore if the old vines and weeds are
destroyed early in the fall this pest will usually not become
troublesome.

The Potato Tuber-worm (Phthorimcea operculella). — For a
long while this has been the most serious pest of potatoes in
California. In the southern states it is a common tobacco pest,
and has recently been reported as injuring potatoes there also.
The moth issues early in the spring and lays her eggs on the
young potato plants. The larvae bore into the stalks, often
killing them, but most damage is done when they make their
way into the ground and attack the tubers, boring irregular
channels in them and soon rendering the potatoes unfit for use.
Several generations may occur each season, the moths of the
later broods laying their eggs on the tubers when opportunity
offers.

When plants are found to be wilting on account of the
presence of these larvae in the stalks they should be cut and
destroyed to prevent infestation by later broods. The field
and adjoining lands should be kept free of nightshade and
other related plants as this insect feeds on these also. The
potatoes should be exposed as little as possible, both before and
after digging, so that the moth may not have an opportunity
to lay her eggs on them. If stored potatoes are found to be
badly infested they may be fumigated with carbon bisulphide.
Four or more treatments at short intervals may be necessary
before all of the larvae are destroyed.

PEAS AND BEANS

The Pea -weevil (Bruchus pisorum). — This common and
widespread pest has made it impracticable to grow peas on a
large scale in many regions. Some parts of Canada and some

INSECTS INJURIOUS TO GARDEN TRUCK 479

of the northern states are comparatively free from the pest,
and so furnish most of the seed that is used. The adults, which
are small, grayish, snouted beetles, appear on the vines while the
peas are in blossom, and lay their eggs on the young pods.
The larvae enter and feed on the peas, finally pupating in them.
In the northern regions they remain in the seed until it is
planted the following spring. In other places they leave the
peas in the fall.

As there is only one generation a year, and as this species
does riot breed in dry peas, it is often worth while to hold the
seed in bins or sacks until all of the adults have issued. Or the

FIG. 227. — Pea-weevils, Bruchus pisorum, and infested peas. (About
twice natural size.)

seed may be treated by heating or scalding or fumigating with
carbon bisulphide.

The Bean -weevil (Bruchus oUectus). — This is the most
common of three or four species of bean-weevils that occur in
some parts of the United States. The adults are only about
one-eighth of an inch long, dark-colored and short-snouted.
Several larvae or bettles may be found in one bean, and they
continue to breed in the stored product throughout the year.
All infested beans should be fumigated with carbon bisulphide
as soon as possible. If the seed is thrown lightly into water
most of the infested beans will float. By destroying these one
can avoid planting infested seed.

480 ECONOMIC ZOOLOGY AND ENTOMOLOGY

The Pea Aphis (Macrosiphum pisf). — This large green aphis
sometimes appears on the peas in such numbers as to weaken
very much or even to kill the plants. The insects pass the
winter on clover and vetches, sometimes doing considerable
injury to these plants. They are usually fairly well controlled
by natural enemies and fungus diseases, but it is sometimes
necessary to resort to spraying in order to save the crop.
Whale-oil soap or some of the tobacco washes may be used.
Considerable force must be used in applying the spray. It is
sometimes practicable to brush the aphids from the vines and
destroy them by covering them with soil. Clover and peas
should not be planted close together.

The Bean Thrips (Heliothrips fasciatus) . — In many places on
the Pacific coast this is the most serious pest of the peas and
beans. It also does a great deal of damage to tomatoes, po-
tatoes, alfalfa and many other cultivated and wild plants.
The black-bodied little insect, with its four narrow, hair-
fringed wings, is so small that it rarely attracts attention even
when present in great numbers, and its presence is usually
not suspected until the leaves of the plant begin to turn yellow-
ish and dry up because the sap has been sucked out. There
are six or seven generations during the year. The young
are wingless and whitish, often with reddish markings on the
sides of the body.

Because the insect feeds more commonly on the underside of
the leaves, and on account of the nature of the crops that it
infests, it is rarely practicable to control this pest by spraying.
We must depend, then, upon the natural enemies of the thrips,
and clean culture methods, for control. As this thrips feeds
on many weeds, particularly on wild lettuce, these should be
kept out of the garden and nearby fields.

CABBAGE

The Imported Cabbage-worm (Pontia rapes). — This is the
most common of a number of butterfly and moth larvse that
feed on cabbage. Before this species was introduced into
America, more than fifty years ago, the larvae of some of our
native butterflies belonging to the same genus were often

INSECTS INJURIOUS TO GARDEN TRUCK 481

abundant in gardens, but they did not bore into the head of
the cabbage as the invader does, and so were not such serious
pests. Because it breeds more prolifically and feeds earlier
and later in the season the imported species has almost or quite
driven the others from the garden. The familiar white cab-
bage-butterflies, with their black-tipped fore wings, appear
early in the spring and lay their eggs on almost any available

FIG. 228. — The imported cabbage-butterfly, Pontia raps; male above,
female below. (Natural size.)

food. In the south the adults may be found at all times of the
year. The female has two black spots in the disc of each fore
wing,the male only one. Both sexes have a spot on the anter-
ior margin of the hind wing. The larvae are velvety green
with a faint yellowish line above and yellowish spots on the
sides. The pupae, or chrysalids, are usually found on the
underside of leaves, on rocks, fences or other objects. The insect
usually passes the winter in the field in the pupal stage.

482 ECONOMIC ZOOLOGY AND ENTOMOLOGY

Minute hymenopterous parasites and other enemies aid in
controlling this pest, but it is sometimes necessary to spray
with arsenate of lead, two or three pounds to thirty gallons of
water. Where the insect is troublesome the spraying should be
done early and repeated as often as is necessary to protect the
plants until the heads form. If the fields are well cleaned many
of the over-wintering pupse will be destroyed. The same meas-
ures should be used for the control of any of the other leaf-
feeding larvae, and for the flea-beetles and others that often
attack the cabbage.

The Harlequin Cabbage -bug (Murgantia histrionica). —
These bright-colored cabbage-bugs, or calico-backs, or fire-
bugs, are often found feeding on the cabbage, where they do
much damage, particularly to young plants, by sucking the
sap from them. The adults, which hibernate in rubbish, be-
come active very early in the spring. This has suggested the
use of trap-crops such as kale, which may be planted early so
that the bugs may feed on it and be destroyed there by spray-
ing with kerosene before the cabbages are planted. The young,
or nymphs, may be destroyed on the cabbage by spraying with
strong kerosene emulsion or whale-oil soap. If a field is kept
clean during the winter, so that the insects will have few places
in which to hibernate, they will usually not become destruc-
tively abundant.

The Cabbage Aphis (Aphis brassica). — These little green-
ish aphids are nearly always more or less abundant on the
cabbage, but usually little damage is done except to the
young plants. Any of the contact insecticides, such as kero-
sene emulsion, or whale-oil soap, or tobacco extract, will
destroy the aphids if it is applied with considerable force.
Again, clean culture is the most successful means for combat-
ting this garden pest, for if all of the refuse is destroyed in the
field the over-wintering insects will perish

The Cabbage -maggot (Pegomyia brassicce). — The roots of
cabbage, cauliflower and radishes are frequently tunneled by
small whitish, footless maggots which are sometimes so numer-
ous that they seriously weaken or kill the plant. The adults
are small flies that look much like the common house-fly, but

INSECTS INJURIOUS TO GARDEN TRUCK 483

they are less than one-fourth of an inch long. The flies lay
their eggs on the plant close to the surface of the ground, or
in the soil near the plant. The larvae soon mine into the
stalk or roots, where they feed for a few weeks, entering the
soil again to pupate. There may be two or three generations
during the summer.

After the larvae have entered the plant but little can be done
to control them. Most of them can be killed by pouring a
teaspoonful of carbon bisulphide in a small hole four or five
inches from the plant, but this is hardly practicable on a large
scale. Control by cultural methods is more satisfactory. All
the old plants and roots should be destroyed early in the fall,
as many of the pupae pass the winter in or around these. Fall
plowing and crop rotation are to be recommended. Mustard
and other cruciferous wild plants should not be allowed in or
near the garden, as they also harbor this pest. If the cabbages
are not planted until most of the flies have laid their eggs on some
other plants they will escape serious injury. Seed beds should
be protected so the plants will not become infected before they
are transplanted. Some growers keep the fly from laying her
eggs on the plant by protecting it with a collar of tarred felt
paper which lies on the ground and surrounds the base of the
plant. Gas tar and other repellents have been used with more
or less success. Very early or very late radishes may escape
infestation.

BEETS

The Beet Leaf -hopper (Eutettix tenella). — In some of the
western states where sugar beets are grown extensively a
condition known as beet curly-leaf, or blight, has caused con-
siderable loss, particularly in warm dry seasons. A few years
ago it was discovered that this condition was caused by a
very small whitish leaf-hopper that sucks the sap from the
leaves. When the plants are badly infested the beets become
stunted, or shrivel, and are of little or no value.

So far no practicable means of control has been found, but
if the land is kept moist and other conditions made favorable
for the plants they will be better able to withstand the loss

484 ECONOMIC ZOOLOGY AND ENTOMOLOGY

due to the insects' feeding. Spraying with contact insecti-
cides has been suggested, but as the insects feed on the under-
side of the leaves it is difficult to reach them.

Web -worms. — There are three or more species of web-worms
(caterpillars) that attack, and sometimes defoliate beets and
other garden plants. They are called web-worms on account
of their habit of spinning fine webs as they feed. The invaded
plants may be killed outright, or only retarded in their develop-
ment. The slender, greenish worms are marked with many
small black spots and sometimes with lighter markings. When
fully developed they enter the ground and spin long slender
cocoons in which they pupate. The adult moths are greenish
or brownish and have a wing expanse of about an inch.

They may be controlled by spraying with Paris green or
arsenate of lead. If the field is plowed late in the fall many of
the pupae will be destroyed. As these worms feed on other
plants, including many of the common weeds, it is evident
that these should be kept out of the garden or fields.

The Beet Aphis (Pemphigus beta). — Sometimes the beets
in certain parts of the field are found to be much smaller than
the average, and soft and spongy rather than firm as they should
be. If such beets are taken from the ground they may be
found to be covered with a mold-like substance which is really
the flocculent excretion from many little plant-lice that are
feeding there. As long as this insect fed on yarrow, door-mat
weed, grasses, and other wild plants as it used to, it was, of
course, of no economic importance, but as soon as beets began
to be cultivated in the region where it occurred it found them
more to its liking, and now in some regions many tons of beets
are destroyed by it each year.

If this pest becomes abundant in a field it should be
starved out by refraining from planting beets or other root
crops there for two or three years.

OTHER GARDEN INSECTS

Cut-worms and Army-worms. — Most of the common dull
grayish cut- worms (caterpillars of certain owlet-moths), hide

INSECTS INJURIOUS TO GARDEN TRUCK 485

away in the ground or rubbish during the day and come forth
at night to feed on any available vegetation. As they have a
pernicious habit of cutting off small tender plants close to the
surface of the ground, they may often do much damage, par-
ticularly in the garden. They are usually held in check by

FIG. 229. — A cut-worm, species undetermined. (About natural size.)

their natural enemies, but sometimes they seem to get away
from control and occur in such numbers that they destroy
nearly every green thing in the affected regions. At such
times some of the species will begin to migrate in great armies

FIG. 230. — Adult of army-worm, Leucania unipimcla. (About natural

size.)

in search of food. They are then called army-worms, and
their control becomes a matter of prime importance to the
man whose field, orchard or garden lies in their path.

The methods used in fighting cut-worms must vary according
to time, place and local conditions. No single remedy can be

486 ECONOMIC ZOOLOGY AND ENTOMOLOGY

given that will prove equally successful at all times and places.
Remedies that are very effective under ordinary conditions
often become wholly useless during a bad outbreak. Clean
cultivation will materially lessen the number of larvae that
occur in a garden under ordinary circumstances. When
the worms are abundant and marching, ditching is often re-
sorted to, usually with very satisfactory results. Banding
trees with tanglefoot or some similar substance is helpful in
case the cut-worms are of the climbing sort. A very few in a
garden may destroy many valuable plants, so it is often worth
while to search for them in the ground around the plants, and
destroy them. Poisoned baits may often be used with success.
When they suddenly appear in great numbers in a field but
little can be done to control them.

The Corn Ear- worm (Heliothis obsoleta). — This larva bores
unsightly irregular channels on the ears of corn, doing particular
damage to sweet corn. It is also a serious pest of cotton, feed-
ing in and destroying the bolls; hence it is also known as the
cotton boll-worm. Tomato fruit-worms and tobacco bud-
worms are among some of the other names that are applied
to this pest, which attacks almost all kinds of garden crops and
many forage plants. The greenish-yellow adult moths appear
early in the spring and lay their eggs on corn and other food
plants. The larvae feed about a month, and then enter the
ground to pupate. There may be from two to five or six broods
during the summer, the greatest number occurring in the south
where the feeding season is longer.

In the garden about the only satisfactory means of control
is hand picking. It is seldom practicable to spray. In the
cornfield the time of planting should be so regulated that the
corn will not be in silk when the moths are flying most abun-
dantly. All infested land should be plowed late in the fall or
during the winter, as this will destroy many of the over-winter-
ing pupae.

The Striped Cucumber-beetle (Diabrotica vittata). — These
small, yellow, black-striped beetles attack many of the vines
in the garden as soon as they are above the ground, and as they
often occur in great numbers they may destroy most of the

INSECTS INJURIOUS TO GARDEN TRUCK 487

young tender plants. The eggs are laid in the soil about the
food plant, and the slender white larvae feed on the roots,
sometimes doing considerable damage there. As the adult
hibernates in the ground or in rubbish in the field, all of the
vines should be destroyed as soon as the crop is off. The most
practicable method of protecting the young vines is to cover
them with a screen that will keep the beetles away. Early
squash or beans may be planted as trap-crops so that the
insects will be attracted to these while the
other vines are getting well started. Air-
slaked lime, tobacco dust or other powders
thoroughly dusted over the plants, afford
some protection, especially if some untreated
trap-crop is near-by.

Squash -bug (Anasa tristis). — This rather
large, flattened, blackish bug is often found
sucking the sap from the leaves of various
vegetables, but it is found most commonly
on squash vines. The adults hibernate in
the garden and appear early in the summer.
The eggs are laid on the underside of the
leaves. The wingless young or nymphs also
feed on the leaves. In the south there may
be two or even three generations during the year. The in-
sects may be gathered and destroyed, and the egg masses
may be easily crushed on the leaves. Shingles or boards or
leaves placed on the ground near the plants make good
hiding places for the adults, and if such traps are examined
in the evening and early morning many of the bugs may be
found and killed.

The Squash-vine Borer (Melittia satyriniformis) . — Often
the squash vines wilt and die because of the attacks of a whitish,
black-headed larva that bores into them. Other vines may also
suffer, but the late varieties of squash seem to suffer most.
The borers may attack almost any part of the vine, but do
most damage when they are working in the base, for they may
then destroy the whole vine. The adult is one of the clear-
winged moths (family Sesiidce}, looking somewhat like the

FIG. 231.— The
cucumber - beetle,
Dial) r otic a 12-
punctata. (Three
times natural
size.)

488 ECONOMIC ZOOLOGY AND ENTOMOLOGY

peach-tree borer. The eggs may be laid on any part of the
plant. In the South there may be two generations each
year. As the borers feed in the vine they cannot be reached by
insecticides. A gummy exudation usually discloses the posi-
tion of the larvae, and it is sometimes worth while to slit the vine
open and kill the pest. The vines should be burned as soon
as the crop is gathered. Fall and winter plowing and crop
rotation will help to control such insects as these.

The Onion-maggot (Pegomyia ceparum). — The roots and
bulbs of onions are sometimes attacked by small white maggots
that in appearance resemble the cabbage-maggot. The
adults of the two species are closely related and can only be
distinguished by close examination. The cultural methods
suggested for controlling the cabbage-maggot are effective in
dealing with this insect also.

The Tomato -worms or Tobacco-worms which are often
serious pests on tomato vines are described on page 499.

CHAPTER XXXVI
INSECTS AFFECTING FIELD AND FORAGE CROPS

As the great field crops of the United States are its chief wealth,
the insect pests that attack grains, cotton and grasses are the
most important animal enemies of our material welfare. The
annual losses from insect attacks on cereals amount to three
hundred million dollars, on hay and forage crops to sixty-six
million dollars and to cotton eighty-five million dollars. The
annual losses to wheat and corn caused by the attacks of but
two insects, the Hessian-fly and the chinch-bug, must amount
to a hundred million dollars. Too much time and care,
then, cannot be given to the study of the nature of the grain
pests and to devising means of lessening their ravages. Be-
cause of the enormous supply of food furnished them by our
great fields of growing grain, their numbers may become,
without restraint, almost inconceivable. In fact, in the case
of all the insect pests of fruits and crops it is our own fault, as
it were, that has led them to become as dangerous to these crops
as they are. We have, by our planting of great numbers of
one kind of plant together, furnished the insects such bountiful
supplies of food that their enormous increase in numbers is
an inevitable result. It is this encouraged increase that con-
stitutes the danger. The number of chinch-bug individuals
that can live at one time in a growing cornfield of hundreds of
acres is simply inconceivable. But as the increase of animals
proceeds by geometrical ratio while the addition of new acres
of food supply can increase only by arithmetical ratio, the
insect numbers finally become more than the food supply can
maintain without too much injury, and then the great losses
begin.

The grain pests are of great variety of kind and habit.
Aphids, and beetle and moth larvae attack the roots. Biting

489

490 ECONOMIC ZOOLOGY AND ENTOMOLOGY

beetles and sucking bugs attack the leaves and stems. The
minute whitish larvae of small flies lie in the stems or leaf axils
and drain the sap. Weevils ravage the stored grain. Cotton
has its peculiar pests, one of which alone, the notorious cotton
boll-weevil, that came into this country from Mexico only
twenty years ago, has in the last decade caused an annual
loss of not less than twenty-five million dollars.

Grasses and forage plants have an exceptionally wide range
of insect enemies, and enemies that for the most part are very
difficult to fight successfully in any inexpensive way. Most
of their combating must be done by such general agricultural
methods as crop rotation, or very deep or unusually late or
early plowing, etc.

The few grain, cotton, and forage crop pests described in the
following paragraphs comprise the ones of chief importance,
but there are many others to be taken into account. Students
should refer to sources of more inclusive and detailed informa-
tion concerning these pests. The bulletins of the government
and state bureaus of entomology are good sources for this
information. Sanderson's " Insect Pests of Farm, Orchard and
Garden," already mentioned, is a good recent manual.

CORN

The Western Corn-root Worm (Diabrotica longicornis) . —
This is a slender larva, or grub, that bores into the roots of young
corn and seriously interferes with its development. Sometimes
these larvae will destroy the greater part of the root system so
that the plant either dies, or is easily blown over by the wind,
or, if it lives, is unproductive. The adult is a small bluish-
green, leaf-eating beetle about one-third of an inch long. The
eggs are laid in the ground in the fall near the roots of the corn
and do not hatch until the following spring. As the larvae feed
only on corn it is evident that a system of crop rotation will con-
trol the pest.

The Southern Corn-root Worm (Diabrotica i2-punctata}. —
The larva of this species is similar in appearance and habits to
the one just described, but it has a wider range of food plants.

INSECTS AFFECTING FIELD CROPS 491

The wing-covers of the small bright-green beetle are marked
with twelve black spots. The beetle feeds on the foliage of
many garden and field plants, often doing considerable damage.
On account of this wide range of food plants it is not as easily
controlled as the preceding species, but crop rotation will still
be of some value. Sometimes it is profitable to plant the corn
so late that it will not come up until after the beetles have laid
their eggs on other plants.

The Cora-root Web -worm (Cr ambus caliginosellus). — This is
still another larva that attacks the roots and stalks of corn,
sometimes killing so many of the young plants that the field
must be reseeded. The yellowish or brownish little cater-
pillars, covered with a case made out of loose web and particles
of dirt, are usually found feeding in the corn plant below the
surface or close to the surface of the ground. The adults are
small, white and yellowish "grass-moths," so called because
they are so frequently seen flying from the grass when it is
disturbed. When the moths are at rest the wings are folded
close around the body. The larvae of the second generation
hibernate in their silken tubes, and are ready to begin feeding
as soon as the plants begin to grow. As the larvae live on the
roots of grasses, corn that is planted on new land will suffer
most. In well-cultivated fields where crop rotation and late
fall or early spring plowing is the practice the injury is usually
not so great.

The Larger Corn-stalk Borer (Diatrce zeacolella). — This in-
sect belongs to the same family of moths as the preceding species
but it is larger. The larvae live in the stalk of the corn, often
weakening it so that it is easily broken by the wind. In the
fall the caterpillars of the second generation bore deep into the
tap-root and there pass the winter, pupating early in the
spring. If the old stalks and butts are dragged together and
burned most of these over-wintering larvae will be killed.
Again, crop rotation is recommended as the best remedy.

The Bill-bugs (Sphenophorus spp.). — There are several
species of snout beetles, or weevils, that injure corn and other
field crops by attacking the stalk and roots. They are usually
injurious in both the larval and adult stages, and are hard to

492 ECONOMIC ZOOLOGY AND ENTOMOLOGY

control. One species, at least, passes the winter in the corn
stubble, and can be killed by burning the stubble. They will
all be less injurious in fields where root crops are rotated with
corn or wheat crops.

The Corn-root Aphis (Aphis maidi-rddicis). — Sometimes the
corn roots are badly infested with little greenish plant-lice
that suck the sap from the plant. The life-history of this
insect is especially interesting as it shows the close relation that
ants and plant-lice sometimes bear to each other. In the fall
the little brown field ants, Lasius brunneus, gather the eggs
that have been laid by the aphids in the ground, and store them
in their nests. Here they are cared for until they begin to hatch
in the following spring. The ants then carry the young plant-
lice to the roots of grasses or weeds that grow in the cornfield
and carefully tend them there, moving them to new plants
when the old ones become overcrowded. When the corn is
planted many of the aphids are transferred to the roots of the
corn, and, as they increase in numbers very rapidly, much
damage may be done in some fields. Because the ants tend
them with such care and receive in return the honey-dew
that is secreted by them these aphids are often called "ant-
cows."

If grasses or weeds are not allowed to grow in the field during
the early spring most of the aphids will starve before the corn
sprouts.

The Corn Ear-worm, which frequently does much damage
in the field; has been discussed on page 486.

WHEAT

Chinch-bugs (Blissus leucopterus). — The adult chinch-bugs
are only about one-fifth of an inch long. The body is dark-
colored, and the whitish wings, which lie folded over the back,
are each marked by a dark triangular spot. The very young,
often called "red-bugs," have no wings, but these gradually
develop as the insect passes through its successive molts.
Because of their habit of assembling in such great numbers on
the stems of wheat, corn and many other field crops, the
chinch-bugs are often the worst pest the farmer has to

INSECTS AFFECTING FIELD CROPS 493

contend with. The insects hibernate in old corn stalks, dead
leaves, clumps of grass or other sheltered places in the field or
roadside. As soon as the grasses or grains begin to grow they
begin feeding on them and lay their eggs, from which the first
brood of young soon issues. They may do serious injury to
the wheat or other small grains before the crops ripen. About
the time the wheat is ready for harvest
the chinch-bugs migrate to oats or young
corn. Fortunately, they do not fly when
making these migrations, but crawl slowly
from field to field. The eggs from which
the second brood are to hatch are laid in
the corn. The young of this brood be-
come mature late in the fall and seek
out suitable places to hibernate. If corn
is not available the whole season may be
passed on grasses.

Many years ago it was discovered that
the chinch-bugs were attacked by a
fungus disease that sometimes very effec-
tively controlled them. When infected
bugs are taken into the laboratory and times natural size.)
placed in boxes with healthy bugs, the
latter soon become infected. These infected bugs may then
be sent into the fields and placed on badly infested plants.
In this way the disease rapidly spreads, and when the climatic
conditions are right it soon destroys most of the chinch-
bugs in the field. But this method of control has not been
wholly satisfactory because in cool and dry weather the disease
does not spread fast enough.

Clean culture is of prime importance. If the adult bugs
that are hibernating in the fields or in grasses by the roadside
and fences are destroyed by burning, there will be no injury
in the following spring. When the insects are migrating from
the wheat to the corn they may be effectively checked by
barriers of dust or coal tar. The dust barrier is made by
plowing and thoroughly pulverizing a narrow strip of ground

FIG. 232. — The

494 ECONOMIC ZOOLOGY AND ENTOMOLOGY

and then making a deep furrow in it across which the chinch-
bugs cannot pass. The furrow must be kept in good condition
by frequent cleaning or dragging. In wet weather it will be
necessary to resort to a barrier made by a narrow line of coal-
tar or some similar substance placed across the path of the
invaders. Such barriers require constant care and attention
during the ten days or two weeks that the bugs are migrating.
Sometimes when the chinch bugs have gained an entrance into
a cornfield those that have massed on the first few rows of
corn can be destroyed by a blast torch or by spraying with
kerosene emulsion.

The Hessian-fly (M ayetiola destructor) . — Probably about 10
per cent, of the wheat crop is destroyed annually by the Hessian-
fly and in some regions the loss
may reach 40 or 50 per cent, in bad
years. The adult is a very small
blackish fly with a pair of delicate
wings that are provided with very
few veins. The eggs are usually
laid on the leaves, and the larvae
make their way toward the base of
the stem where, protected by the
leaf sheath, they begin sucking the

• A«. ,T -s a iuice from the plant. The pupar-

FIG. 233. — The Hessian-fly, J . , . » ,

Mayetiola destructor, adult mm in which the pupal stage is
male. (Much enlarged; after passed looks so like a flax seed that

the pupal stage is usually referred to

as the " flax-seed stage." There may be one to four generations
a year, according to the region and climatic conditions, but the
early spring and late fall broods are most destructive. The
flies that issue late in the fall lay their eggs on the young win-
ter wheat, and the pupal, or flax-seed, stage is reached before
cold weather comes. The adults issue from these pupae early
the next spring.

The best method of control is to refrain from planting the
wheat in the fall until the flies have laid their eggs elsewhere.
Only a close study of the fly and the weather conditions that
control its time of issuing in the fall will enable one to

INSECTS AFFECTING FIELD CROPS 495

choose the right date for sowing. After conducting long series
of experiments the United States Bureau of Entomology has
suggested the following dates as safe for sowing wheat in aver-
age seasons: in northern Michigan soon after the first of Sep-
tember; in southern Michigan and northern Ohio, about
September 20; in southern Ohio, after the first week in October;
in Kentucky and Tennessee, October 10 to 20; in Georgia and
South Carolina, October 20 to November 15. The exact
time will also depend upon altitude as well as latitude. Crop
rotation, thorough cultivation, clean culture and the use of
good fertilizers are all important in regions where the Hessian-
fly is a bad pest. No varieties of wheat thus far found are
wholly exempt from the attacks of the fly but some, on account
of their habit of growth, withstand the injury better than others.

The larvae of certain other flies may also often be found
working in the wheat in much the same way as the Hessian-fly,
but they rarely occur in sufficient numbers to do serious
damage.

The Wheat Joint -worm (Isosoma tritici}. — The joint- worms
occur in the stems of the wheat causing them to swell slightly
and become hard and woody so that the grain is not well
nourished. The adults are small black insects belonging to
the family Chalcidida, nearly all the other members of which
are parasitic. Crop rotation is the best means of control.
Infected straw and stubble should be burned before the adult
insects, which are overwintering in such places, issue.

The Wheat Straw-worm (Isosoma grandi}. — This insect is
closely related to the preceding species, but has somewhat
different habits. Many of the members of the spring brood
are wingless and look much like small ants. The eggs are laid
on the young wheat, and the larvae frequently destroy the whole
plant by eating out the crown. The adults of the next genera-
tion are larger and provided with wings so that they may fly
considerable distances. The young that hatch from the eggs
of this brood work in much the same way as the wheat joint-
worms. They pass the winter in the pupal stage in the straw.

The control measures are the same as for the wheat joint-
worm.

4g6 ECONOMIC ZOOLOGY AND ENTOMOLOGY

The Grain-aphis, or Green -bug (Toxoptera graminum) —
This little green plant-louse sometimes seriously injures young
wheat plants by sucking out the sap. They do most damage
in the south, where the open winters often allow them to feed
and reproduce during the whole year. In such instances they
become so abundant on the winter wheat that whole crops may
be ruined as early as March or April. As long as the tempera-
ture is above 56° F. the green-bugs are held in check by a
minute wasp-like parasite, Lysiphlebus testaceipes, and it is
only during the winter time, when it is warm enough for the
pest to breed but too cold for the parasite, that the plant-lice
become destructively abundant. Oats are the favorite food
of these aphids, and they seldom do much damage in places
where volunteer oats are not allowed to grow.

When small injured spots appear in the field late in the winter
the green-bugs in such areas should be killed by spraying with
kerosene emulsion, or by burning straw over them, or by plow-
ing under the infected grain.

STORED GRAIN

Stored grains are often attacked by the larvae of beetles or
moths, and unless preventive measures are adopted much of
the grain may be destroyed.

The Grain-weevil (Calandra granaria) , and the Rice -weevil
(C. oryzce). — Weevils are usually the most common pests of
stored grain. They are small beetles with long snouts, with
which they puncture the grain, thus making a place where the
egg may be inserted. The larvae are short, thick, legless grubs
that feed in the grain until ready to pupate. The beetles, too,
feed on the grain, and as they increase in numbers very rapidly
a slight infestation may soon assume serious proportions.
Grain should be stored only in clean, tight bins. If this pre-
caution is taken but little loss will be suffered on account of
these pests. If, however, the grain becomes infested, it should
be treated with carbon bisulphide, using about five pounds for
every 1000 cubic feet, or even more if the room is not tight.
Best results will be obtained if the temperature is 70° F. or
higher. Dishes containing the liquid, or cotton or waste

INSECTS AFFECTING FIELD CROPS 497

saturated with it, should be placed on top of the grain. As
the gas that comes from it is heavy it will sink and reach all
parts of the bin. Remember that this gas is inflammable and
explosive. If the grain in the bins can be heated to 120° F. all
the weevils in all stages of development will be killed.

The Saw-toothed Grain-beetle (Silvanus surinamensis). —
Unlike the weevils, which are somewhat cylindrical, this small
grain-beetle is quite flat. It may easily be recognized by the
serrate margins of the prothorax. The larvae are long and
slender and provided with six
legs, enabling them to move
about freely and thus injure
several grains. The methods
of control are the same as for
the weevils.

The Angumois Grain-moth
(Sitotroga cerealella) . — In the
south the grain-moth is even
a worse pest than the weevils
for it often occurs in almost
incredible numbers and attacks
wheat in the field as well as in
the granaries. The moths fly
from the storerooms while the
wheat is heading, and lay their eggs on the grain. The larvae
make their way into the kernels and become full grown about
the time the wheat is mature. Other generations follow,
the members of each attacking the grain wherever it is
found, in the field, in the stack, or in store-rooms. Corn is
not attacked as often as wheat, but seed corn stored in barns
may often be badly injured. The grain should be threshed
as early as possible and stored in tight bins or good sacks. If
it becomes infested while stored, it may be treated with car-
bon bisulphide. Cleanliness about the barns and particularly
around the granaries is most essential. Badly infested grain
may be fed to chickens or hogs.

The Mediterranean Flour-moth (Ephestia kuehniella) .—
Mills are sometimes overrun with the larvae of a small grayish

FIG. 234. — Adult, pupa, and
larva, of the saw-toothed grain-
beetle, Silvanus surinamensis.
(Much enlarged; after Howard and
Marlatt.)

moth. The larvae spin little silken tubes which protect them
while they are feeding in. the flour or waste about the mill.
When full grown they wander about in search of a suitable
place to pupate, spinning a web wherever they go. It is this
habit that renders them most injurious, for the infested flour
and many parts of the mill become filled with the webs. This
necessitates frequent and expensive stoppings of work in the
infested mills. Great cleanliness about the mill is necessary.
When the insect becomes troublesome the mill should be
closed tightly and fumigated with hydrocyanic acid gas under
the direction of some experienced person. If the temperature
throughout the mill can be raised to about 120° F. and main-
tained there for a day, all moths, pupae, larvae and eggs will
be killed.

COTTON

The Boll-weevil (Anthonomus grandis). — There are several
important enemies of the cotton plants, but during the last few
years the boll-weevil has become so important as to over-
shadow almost all the others. Indeed, one of these insects,

FIG. 235. — Boll-weevil, Anthonomus grandis. (Much enlarged.)

the cotton-worm, which was formerly looked upon as one of
the worst enemies, is now regarded with some favor by many
planters because it sometimes aids in controlling the weevil by
stripping the late foliage from the plants and thus depriving
the weevil of its food.

This small, brownish snout beetle is commonly known as the
Mexican cotton boll-weevil because, like several other insect
pests of the south, it came into the United States from Mexico.

INSECTS AFFECTING FIELD CROPS 499

The beetles attack only cotton. Those issuing from their
winter hiding places early, feed on the foliage and lay their
eggs on the unopened buds, or "squares," as soon as they com-
mence to form. The larvae hatching from these eggs feed for
ten or twelve days, and usually cause the infested squares to
fall to the ground. There may be four or five generations
during the summer, the beetles attacking the older bolls as
soon as the squares are no longer available. The adults of the
last generation hibernate in old cotton plants or in rubbish in
or near the fields. When they are hunting for suitable places
in which to hibernate they may fly for considerable distances,
and thus the distribution of the species is provided for.

The larvae in many of the infested squares that drop to the
ground will perish on the hot, unshaded soil. It is therefore
advisable to plant the rows as far apart as practicable and to
use varieties of cotton that produce little foliage in order
that the sun may shine on the fallen squares. As the damage
is usually worse on the late varieties the best of the early
varieties should be selected in regions where there is danger of
boll- weevil infestation. Any cultural methods that will
strengthen the plant and aid in the early maturing of the bolls
will materially increase the yield. As soon as the crop is
gathered all the cotton stalks and all the rubbish in the field
*should be burned. This will kill many of the insects, and
destroy the feeding and hibernating places of most of those
that are left.

The Cotton Boll-worm, which is the same as the corn ear-
worm, has been discussed on page 486. It is best controlled
in the cotton field by plowing late in the fall, thus destroying
the over-wintering pupae. Early varieties of cotton should be
planted, as it is the later broods of moths that lay their eggs
on the cotton, the corn being preferred as long as it is young and
available. Late planted corn in or near the cotton fields will
sometimes keep the boll-worm away from the cotton.

TOBACCO

Tobacco-worms, or Horn- worms.— The large greenish horn-
worms (larvae of sphinx- or hawk-moths) are probably the most

500 ECONOMIC ZOOLOGY AND ENTOMOLOGY

serious pests of tobacco in the United States. They feed on the
green leaves, and, when abundant, may cause a loss of from 10
to 15 per cent, of the crop. Two species, somewhat similar
in appearance and habits, are found throughout the tobacco
growing regions. The northern tobacco-worm, Phlegethontius
quinqtiemaculata, is more common north of the latitude of
Washington, D. C.,and the southern tobacco-worm, P. sextata,
is the species usually destructive in the southern tobacco
fields .

FIG. 236. — Tobacco-worm, larva of the hawk-moth, Phlegethonlius qitin-
quemaculata, feeding on tomato. (About 1/2 natural size.)

The adults, which are large grayish sphinx-moths, lay their
eggs on the lower surface of the leaves. The larvae feed on the
leaves and become full grown in about three weeks. They are
then three or four inches long and dark green in color with
white stripes on the sides. On the northern species these
white markings are V-shaped, while on the southern species
they are simply oblique lines. On the last segment of the
body is the conspicuous "horn," which has suggested the name
"horn-worm." The larva? burrow into the ground a few
inches before changing to the brownish pupae. In the pupal
stage the proboscis of the forming moth is inclosed in a peculiar
handle-like sheath. In some regions these pupae are known as

INSECTS AFFECTING FIELD CROPS 501

"horn-blowers." During the summer the pupal stage lasts
about three weeks, and there may be two or even three genera-
tions in the south.

The insect passes the winter in the pupal stage. Many of
the pupae can be destroyed by thorough plowing and harrowing.
As the larvae are usually easily detected on the plant, hand-pick-
ing is the common method of control where labor is cheap.
Paris green dusted or sprayed over the plants has long been a
favorite remedy, but as this sometimes burns the foliage, ar-
senate of lead is now more commonly used. From four to six
pounds of arsenate of lead to 100 gallons of water are
the proportions usually recommended.

These same horn-worms are often important enemies of
tomatoes.

The Tobacco Flea-beetle (Epitrix parvula). — This small,
black flea-beetle looks much like flea-beetles more commonly
found on tomatoes, potatoes and other garden plants. Indeed,
this species does, not restrict itself to tobacco, but may often
be found on other plants in the field and garden. The beetles
feed on the foliage, and, when abundant, may do considerable
damage, particularly to young plants. The slender, whitish
larvae usually feed on the roots of weeds, but they sometimes
attack the roots of garden plants also. They pupate in the
soil when fully developed. There are probably several genera-
tions each year.

If the field is kept free from weeds there will be less oppor-
tunity for the larvae to find food. Where the beetles appear in
destructive numbers the plants should be sprayed thoroughly
with arsenate of lead, five or six pounds of the poison to 100
gallons of water. The tops of the young plants may be dipped
into an even stronger solution of the poison just before they
are set out if there is danger of the flea-beetles attacking them
early.

The Tobacco Leaf -miner (Phthorimaa operculella.} — This
little larva, which is only about half an inch long, lives between
the upper and lower epidermis of the leaves causing them to
split. This has suggested the popular name of "split-worm"
for the pest. Sometimes the larvae come to the surface and

502 ECONOMIC ZOOLOGY AND ENTOMOLOGY

wander about before entering the leaf in another place, If the
leaves are well sprayed with arsenate of lead many of the
larvae will be poisoned as they attempt to eat their way into the
leaf again. The adult insect is a small grayish moth with
minute dark spots on the front wings.

The Cigarette-beetle (Lasioderma serricorne). — This minute
brownish beetle, which is only about one-sixteenth of an inch
long, and its whitish grub or larva, feed on dried tobacco when-
ever they can find it. They do serious damage to the stored
dried leaves and to cigars and cigarettes after they have been
manufactured. In warm factories the insect may breed
throughout the year and increase in numbers very rapidly.
As this pest lives and breeds in any kind of dried tobacco it is
necessary to keep the factory clean and not allow fragments or
dust to collect in out of the way places. Infested tobacco or
tobacco products or infested factories may be fumigated with
carbon bisulphide or with hydrocyanic gas.

There are several other insects that do more or less damage
to tobacco, but most of them can be controlled by keeping the
field and its immediate vicinity free from weeds, especially
those weeds that are nearly related to the tobacco plant,
or by spraying with arsenate of lead.

GRASSES AND FORAGE PLANTS

The Clover Root-borer (Hylastinus obscurus) . — The roots of
clover are often attacked by a short, thick, whitish larva that
feeds in the tap root or the larger rootlets. The adult insect is
a beetle only about one-eighth of an inch long and reddish-
brown in color. The beetles hibernate in the infested plants,
and early in the spring fly to new plants where they lay their
eggs. Badly infested fields should be plowed up as soon as the
crop is cut so that the roots may dry out and the larvae starve
before they are ready to pupate. This insect is seldom in-
jurious in pastures.

The Alfalfa Weevil (Phytonomus murinus). — The alfalfa
weevil has recently been introduced into some of the western
states and threatens to become a serious pest. Both the larvae

INSECTS AFFECTING FIELD CROPS 503

and adults feed on the foliage and sometimes on the stem of the
plant also, so they are capable of doing much injury. The
beetles are only a little over one-eighth of an inch long, dark
brown, and are covered with short, thick, black and grayish
hairs. The snout is short and curved.

Among the control measures that have been suggested are
cutting the first growth when most of the eggs are on the
plant, disking the field early in the spring and dragging the
field with brush after the crop has been cut. Every effort is
being made to prevent the spread of this pest.

FIG. 237. — Alfalfa weevil, Phytonomus murinus. (Much enlarged.)

Grubs. — Grass and pasture lands are often badly infested
with large white grubs which feed on the roots of the plants
growing there. These may remain in the larval stage two or
three years, but finally transform to pupae from which issue the
large, brown beetles known as May -beetles, or June-bugs. The '
beetles fly at night and are frequently attracted to lights. As
these same insects are common pests of corn and of many other
cultivated plants it is not well to let them become numerous in
grass lands that are near cultivated fields. Deep plowing late
in the fall will destroy or expose to the birds many of the larvae
and pupae. Hogs turned into an infested pasture will root
out and eat most of the grubs.

Wire-worms. — The long, cylindrical, hard, wire-worms have
habits similar to the grubs just discussed. They may remain
in the larval stage from three to five years and often do con-
siderable damage to corn, wheat, potatoes and other field and
garden crops. The adults are the well-known click-beetles, or
snapping-beetles. Late fall or eary spring plowing, and crop
rotation, are the control measures usually adopted.

504 ECONOMIC ZOOLOGY AND ENTOMOLOGY

Grasshoppers. — There are many species of grasshoppers that
occur in fields or meadows in greater or less numbers every
year. The Rocky Mountain locust, that lives permanently on
the high plains of some of the Rocky Mountain states, was for
many years the best known of these because of its great
migrations into the Mississippi Valley where it destroyed all
the vegetation to be found there. The last of these migrations
was in 1877. The settling and consequent changed conditions
of the regions in which this grasshopper breeds have put a
stop to the great flights.

Grasshoppers lay their eggs in masses in the ground, and cover
them over with a sticky fluid that forms a capsule-like covering
when dry. Meadows and pastures or bare, dry, rather firm
ground, are the places usually selected for egg-laying. The wing-
less young, or nymphs, that issue the following spring feed on
grasses or any other available vegetation. When the food
becomes scarce they may travel in great numbers as do the army
worms, devouring every green thing in their path. However,
they cannot travel far in this wingless stage, and even after
acquiring their wings most kinds seldom fly far from their
breeding grounds, and so are easily controlled. If the places
where the eggs are deposited are plowed during the fall or early
spring most of the eggs will be destroyed or buried so deep that
the young cannot come to the surface when they hatch. It is
sometimes practicable to burn over a field where the young
occur in great numbers and thus destroy them before they
migrate to cultivated fields. On hard smooth ground many
may be killed by rolling with a heavy roller. When the nymphs
are migrating a field may be protected by ditching as for the
army worms (page 484). The poisoned mash (page 415) rec-
ommended for use against cutworms, may also be used with
success against the grasshoppers. Various forms of hopper-
dozers have been contrived for catching the wingless grass-
hoppers. The most common is a long, shallow pan or tray
mounted on runners in which is placed a little water covered
with kerosene or crude oil. Oil or coal tar may be used
without the water. The back and ends are provided with
walls about three feet high to prevent the grasshoppers from

INSECTS AFFECTING FIELD CROPS 505

jumping over it when the apparatus is pulled or pushed across
the field.

Ordinarily the grasshoppers are pretty well controlled by
their natural enemies, among the more important of which are
birds, the larvae of blister-beetles, tachina-flies and bee-flies,
and a little red mite that attacks the nymphs and the eggs.

CHAPTER XXXVII
INSECTS INJURIOUS TO FOREST AND SHADE TREES

Since the attention of the American people has been called
to the need of preserving and caring for the forests of our land,
and the government has established forest reservations in all
those states still containing extensive wooded areas, the study
of the insect pests of forest trees has made considerable prog-
ress. Although in European countries, especially Germany,
the study of forest insects has been the most notable part of
the economic entomological work, it has not been so in America.
But forest preservation is a much older science in Europe than
with us, where, indeed, it is a very recent thing.

The insect enemies of forest trees are many, and often very
serious in their ravages. Especially in the great pine forests
are the insects a constant menace, and too often a menace
realized. Fire is the only other forest enemy as dangerous as
the insects. And the danger of fire, because less insidious and
difficult to appreciate, is being much more rapidly lessened by
vigilant care and effective methods of prevention than is the
less obvious but more widespread and continuous danger
from insect attack.

Forest entomologists estimate the annual forest loss from
insect pests at one hundred million dollars. Yet the injuries
to shade and ornamental trees are likely to have, in the eyes of
most of us, an importance that outweighs that of the forest
losses. No money value can satisfactorily be assigned to a row
of stately elms along a street in town or village, nor to a
single well-placed, splendid old oak in a dooryard. We shall
give, therefore, special attention in this brief chapter to the
insect enemies of shade trees and to the means of fighting them.
This is the more fitting, also, as forest insects must be controlled
rather by general forestry methods and the work of specially

506

INSECTS INJURIOUS TO FOREST TREES 507

trained forest rangers and caretakers than by the usual
methods of the economic entomologist.

The few insects described in the following paragraphs are
perhaps the most important of the commoner pests of shade
trees, but there are many others of similar habits which may be
found by keen-eyed and persevering students. The remedies
for these others will be of the same general nature as those
recommended for the insects described, although modifications
of them may need to be made to fit particular cases.

Government and state bulletins will give further and more
detailed information about the pests briefly described here and
also about others likely to be found on the trees.

The Gipsy-moth (Porthetriadispar). — One of the very worst
of the many shade tree and woodland pests is the gipsy-moth,

FIG. 238. — Gipsy-moth, Porthetria dispar, adult female. (About 1/4
larger than natural size.)

which was introduced into this country from Europe about
1868. Fortunately it spreads slowly and as yet occurs only in
the New England states. The federal government and the
states concerned are now spending more than a million dollars
a year in trying to control this pest. But in spite of all their
efforts the insect is gradually widening the boundaries of the
infested areas, and other localities may in time suffer from its

ravages.

The brownish-yellow, slender-bodied, male moth flies readily,
but fortunately the large, sluggish female cannot fly, although

508 ECONOMIC ZOOLOGY AND ENTOMOLOGY

she is provided with well developed wings. The female has the
wings whitish, marked with small black spots and wavy lines.
She lays her eggs on the trees, near-by fences or hedges or other
convenient objects. The egg masses, which consist of 400 or 500
eggs covered over with yellowish hairs from the insect's body,
remain over winter in these places. The young caterpillars,
which issue early in May, at once begin feeding on any available
foliage. They are covered with long hairs, and as they swing
from the branches by fine silken threads they may be carried
by winds for considerable distances, or they may drop on
passing vehicles and be transported for some miles before they
drop off. Thus new localities, not too far away, are easily

FIG. 239.— Gipsy-moth, Porthetria dispar, larva. (About 1/4 larger than

natural size.)

infected. The full-grown dark-brown larvas attain a length of
about three inches, and attack practically all kinds of wild and
cultivated trees and shrubs. A deciduous tree will often live
even after three or four defoliations, but the coniferous trees
die after one complete stripping.

In the orchard this pest may be fairly well controlled by
painting the egg masses with creosote sometime during the
winter, or by spraying the leaves with arsenate of lead as soon
as the larvae appear in the spring. In the woodlot control is
much more difficult, and usually even impossible, although the
same measures as recommended for the orchard may some-
times be practicable. As the very young larvae do not feed on
conifers these trees may be protected by clearing out all brush
and deciduous trees. In its native home this insect is not such
a serious pest because it is controlled by its natural enemies.

INSECTS INJURIOUS TO FOREST TREES 509

For several years the U. S. Bureau of Entomology has been
introducing many of these parasitic and predaceous insects,
hoping that some would prove to be efficient here. A measure
of success has attended these efforts and it is quite possible that

FIG. 240. — Brown-tail moth, Euproctis chrysorrhoza, adult. (About 1/4
larger than natural size.)

when enough of these natural enemies have been established in
this country the pest may be overcome, and, in the future,
kept in reasonable control.

The Brown-tail Moth (Euproctis chrysorrhaa) . — Like the
gipsy-moth the brown-tail was introduced from Europe, but

FIG. 241. — Brown-tail moth, Euproctis chrysorrhaa, larva. (About 1/4
larger than natural size.)

much more recently. It attacks orchard trees and almost
all kinds of shade trees except the evergreens. The moths are
snow-white, with a conspicuous brown tuft at the end of the
abdomen. They fly by night, and are attracted by lights, so
that shade trees and fruit trees in towns are usually first to

510 ECONOMIC ZOOLOGY AND ENTOMOLOGY

suffer from their attacks. The insects pass the winter as small
larvae that hibernate in a nest made of leaves and tips of twigs
fastened together with silken webs. Some of the hairs of the
full-grown larvae cause severe irritation when they touch the
human skin. This is regarded by many as the most serious
phase of an outbreak of this pest. As yet the insect occurs

FIG. 242. — Tent of tent-caterpillar on a live-oak tree. (Reduced.)

only in some of the New England states, but it is constantly
being introduced into other states on nursery stock, and unless
great care is taken it may soon become established elsewhere.
The winter nests containing the young larvae are conspicuous
on the leafless trees, and should be pruned off and burned. Ar-
senate of lead, 4 pounds to 50 gallons of water, will kill most of

INSECTS INJURIOUS TO FOREST TREES 511

the young larva; before they make their nests if the trees are
sprayed as soon as the eggs are hatched in the late fall.

Tent -caterpillars and tussock-moths, which have been de-
scribed in the chapter on orchard insects, and many other
leaf-feeding larvae, often do much damage to shade trees. A
study of their habits and life history will usually reveal some
vulnerable point and suggest the control measures to be
adopted. Where arsenate of lead is used it is usually necessary
to use 4 or 5 pounds to 50 gallons of water.

The Elm Leaf -beetle (Galerucella luteola). — Elm trees are
attacked and seriously injured by many different insects. In
many places the leaf-beetles are the most important of these
pests. These beetles are about one-fourth of an inch long and
greenish or yellowish marked with darker spots and lines.
They hibernate in protected places during the winter and feed
for awhile on the young leaves in the spring before they lay
their eggs. The larvae feed for two or three weeks before de-
scending to the ground to pupate. There may be two genera-
tions each year.

Although it is difficult to spray trees as tall as elms often
grow to be, without the use of special apparatus, yet it is pos-
sible to construct a spraying outfit that will enable the operator
to reach easily all parts of the tree. Infested trees should be
sprayed with arsenate of lead as soon as the beetles begin to
feed in the spring, and again about two weeks later when the
first larvae hatch. Sometimes later sprayings may also be
necessary.

Plant -lice and Scale -insects. — Many of the plant-lice that
feed on the foliage of various shade trees, and the scale-insects
that may attack any parts of the trees above the ground, can
often be controlled by spraying with kerosene emulsion during
the summer or, and usually better, with the sulphur-lime wash
during the winter.

The Locust-borer (Cyllene robinia). — Locust trees are often
attacked by borers which after a little while penetrate so far
into the wood that they cannot be removed or killed. These
borers are the larvae of dark-brownish beetles which are about
an inch and a half long and have eight or ten narrow golden

512 ECONOMIC ZOOLOGY AND ENTOMOLOGY

yellow stripes across the thorax and wing covers. Repeated
attacks may kill the trees, and it is the safest policy to cut out
and burn all infested trees in order that they may not serve as
breeding places for new generations that will later attack sound
trees.

The Carpenter -worm (Prionoxystus robinice). — The larvae of
a large, grayish, night-flying moth have come to be known as
"carpenter worms" because they work so readily in the wood

FIG. 243. — Elm leaves curled by elm aphis, Schizoneura ulmi. (Reduced.)

of many of our shade trees. For some months after hatching
the larvae burrow in the sapwood, and when several of them are
at work in one tree they may kill it by girdling. As they
grow older the larvae bore into the solid wood, making large
burrows in which they live for a year or two longer before
they change to pupae. As these borers are more apt to be
found in trees that have the bark rough or scarred or wounded,
care should be taken to keep the bark uninjured. The larvae

INSECTS INJURIOUS TO FOREST TREES 513

in the burrows may be killed by injecting a little carbon
bisulphide into the hole after the castings and exudations have
been cleared from the entrance. The hole in the bark should
then be filled with cement.

The Leopard-moth (Zeuzera pyrina) .—The leopard-moths are
beautiful white moths that have their bodies and wings marked
with many black spots. The larvse may

be found in any part of the tree, but they

more often attack the smaller limbs. As

they work principally in the sapwood,

the affected limbs are usually killed. The

only satisfactory method of treatment is

to cut out all the infested wood and burn

it. It is easier and safer to sacrifice the

whole tree if it is badly infested. The

female moths do not fly readily, so the

infestation does not spread rapidly except

in places where the trees are very close

together.
The Oak-primer (Elaphidion mllosum).

—When oak-pruner beetles occur in con-
siderable numbers the trees are made un-
sightly by the dead branches which later

fall to the ground. The damage is done

by the larvse, which bore in the twigs and

finally cut them off. As the larvae pupate

in the fallen twigs they should be gathered

and burned before the adult beetles issue.

This insect attacks many kinds of shade

trees, and sometimes may be injurious to v w ,

. , . , rlG. 244. WOrK

certain fruit trees also. of oak twig-girdler,

On the Pacific Coast there is another AgrUus sp. (About
smaller borer, Agrilus politus, that attacks 2/3 natt
and kills the small branches of the oak trees. As the twigs
are killed, but not cut off, the tree soon becomes very ragged
and unpleasing in appearance. Such infested twigs should be
cut off some time during the winter.

33

5H ECONOMIC ZOOLOGY AND ENTOMOLOGY

FOREST INSECTS

A certain amount of insect injury is occurring in almost every
great forest all the time, while from time to time particular
forests are devastated by the outbreaks of certain insects that
kill practically all of the trees in the affected regions. In some
instances these outbreaks have spread over 50,000 square miles,

FIG. 245. — Work of a bark-borer, Phlceosinus cristatus, on Monterey
cypress. (Reduced.)

and trees that would have produced millions of feet of lumber
have been destroyed. Each year there are lesser outbreaks
when, although comparatively few trees may be killed, many are
retarded in their growth or so distorted or injured that they
make only second- or third-class lumber. Altogether the

INSECTS INJURIOUS TO FOREST TREES 515

annual loss to our forests from insect attacks must amount to
many millions of dollars.

A great part of this injury is due to the work of the bark-
beetles, belonging to the family Ipidce. These are small,
robust, blunt-headed beetles which burrow into the bark to
lay their eggs, and whose larvae burrow out through the live
bark in all directions from the egg chambers. Of these bark-
beetles the members of the genus Dendroctonus are the largest
and the most important. The adult beetles bore into the bark
until they reach the cambium where each species makes a
characteristic kind of burrow. The larvae also make character-
istic chambers in the bark or on the surface of the wood so.that
one who is acquainted with their work can always tell from the
nature of the borings just which species has been at work on a
tree. The members of the genera Ips, Scolytus, and others also
frequently do considerable damage. For a long while it was
believed that nothing could be done to control the spread of
these insects in the forests. But a study of their life- history
suggested that many of them might be controlled by cutting
out the infested trees and thus destroying the immature
stages of the beetles before the adults issue to attack new trees.
Experience has shown that this is practicable, and the Bureau
of Entomology has agents in the principal forest regions to
direct properly the work of cutting wherever the owners care
to undertake it.

Abalone, 232
Acanthia lectularia, 395, *3g6
Acanthocephala, 87
Acarina, 209
Achroia grisella, 196
Acipenserida;, 247
Acropora muricata, *67
Actinozoa, 67
Adaptation, 346
Adelochorda, 237
Adoxus viiis, 466
Aegcria tipuliformis, *^6g
African tick fever, 356
Agelina sp., *2og
Agkistrodon cantor trix, 270

A. piscivoris, 270
Agrilus sp. injury, *5i3

A. politus, 513

A. ruficollis, 468
Alee americana, 303
Aleurodes citri, 451

A. nubifera, 452

A. howardi, 452
Alfalfa weevil, 502, *$O3
Alligator mississippiensis, 264
Alligators, 264

Alternation of generations, 65
Alosa, 249

Alsophila pometaria, 429
Amblyomma variegatnm, *2ii
Amblystoma tigrinum, '257
Ammophila, *i83
Amoeba, structure and habits,

*26
Amceba dysentercz, 350, *35i

A. mcleagridis, 351
Amcebic dysentery, 350
Amphibia, 239, 256, 257
Amphineura, 222
Amphipoda, 121
Anarsia lineatella, 435

INDEX

(Numbers marked with * indicate illustrations.)

Anasa tristis, 487
Anas boschas, 332

A. cinereus, 332

A. cygmoides, 332
Anchovies, 250
Anguillidas, 249
Anguillula sp. *jg
Animals, branches and classes, 54

classification, 48, 55

domesticated, 321, 7

denned, i

names, 50

Ankylostomiasis, 84
Annelida, 98
Anolis principally, 265
Anopheles, larvae, *37i

A. maculipennis, *36o, *372

wing, *372
Anosia plexippus, metamorphosis,

"151

Anseres, 280
Ant-eater, 300, 301
Antelope, 303

Antennae, different kinds, *i3o
Anthonomus grandis, *4g8

A. signatus, 473
Anthrenus scrophiilaritz, *4oi
Antilocapra americana, 303
Ant-lion, 167
Ants, 199, 398

Argentine, 398, *399

black, 399
25, nest, artificial, *2os

pavement, 399
Anura, 256, 257
Aphididae, 437
Aphids, 437
Aphis, *4io

grain, 496

green, 439

peach, 442
Si?

5*8

INDEX

Aphis, rosy, 439, *44o
woolly, 440, *44i

Aphis brassicce, 482
A. forbcsi, 473
A. maidi-radicis, 492
A. persiccE-nigcr, 442
A. pomi, 439
A. sorbi, 439, *44o

Apis mellifica, *i2y, 334

Apple-maggot, 425

Apple-tree borer, 436

Apoda, 256

Aptera, 154

Apteryx, 274

Archiannelida, 98

Arachnida, 206

Araneina, 206

Argas persicus, 212, *3S6

Argentinidae, 252

Argonaut, 235

Argon auta argo, 235

Argyrosomus, 252

Ariolimax californica, *2$i

Armadillos, 301

Army-worms, 484, *485

Arrow-worms, 86

Artemia, 113

Arthrogastra, 206

Arthropoda, 106

Artiodactyla, 303

Ascaris canis, 81

A. lumbricoides , So
A. megalocephala, 80

Ascidians, 237, *238

Aspidiotus perniciosus, 445,

Asterias sp. *go

Asteroidea, 94

Atropidae, 161

Alropos sp. *i6i

A. divinatotia, 161

Aulacaspis rosae, *468

Aves, 273

Axolotl, 257

Babesia, 362

B. bigeminum, 363
Baboons, 319
Bacillus pestis, 375
Badgers, 315
Balaenidae, 302

Balanoglossus, 237
Banteng, *328
Bark-borer, injury, 514
Bark-lice, 161
Barnacles, *ii5
Barnacle-scale, 460
Bass, 253
Bats, 312
Beach-fleas, 121
Bean-weevil, 479

thrips, 480
Bears, 315
Beavers, 310
Bedbugs, 395, *396
Bee-hive, observation, *i95
Bee-lice, 196

-moth, *i95
Bees, social, 184

honey, 185
Beet leaf-hopper, 483

aphis, 484
Beetles, 169

carpet, *4oi

ladybird, *4O7

predaceous ground, *4og
Bembccia marginata, 467
Berries, insects injurious to, 462
Bill-bugs, 491
Bird-lice, 161
Birds, classification, 278

determining and studying,
285

development and life-history,
277

distribution and migration,
288

economics, 292

external parts and regions,

*275
feathers, *274

habits, 290, 292

plumage, 289

protection, 292

and seasons, 286

song, 285

structure, 273

water and shore, 280
Bison bison, *3O4, *3©5
Black-fies, 385, *386
Black-head, of turkeys, 351
Black scale, 452, *453

INDEX

Bladder-worms, 75
Blastophaga, 181
Blattidiae, 162
Blepharipeza adusta, *4og
Blissus leucopterus, 492, *493
Blister-mites, 213
Blow-fly, *388
Blue-bottle flies, 388
Boa constrictor, 272
Bob-white, *282, 283
Boll-weevil, *4g8
Bombyx mori, *ijf>, 334
Book-louse, *i6i
Boreus, 167
Bos sondaicus, *328, 329

B. primigenius, 329
Bot-flies, 389

horse, *389, *39O

sheep, 391
Bovidae, 304
Brachiopoda, 88
Brachyura, 116, 120
Braconidae, 180
Braconidae, cocoons, *4og
Branches, 53
Braula, 196
Brevoortia, 250
Brittle-stars, 95
Brown-tail moth, *5o9

larva, *5og
Bruchus pisorum, 478, *479

B. obtectus, 479
Bryobia pratensis, 212, 468
Bud- moth, 432

Buffalo, *304, *3O5
Bufo halophilus, *2$8
Bufonidae, 258
Bull, *328
Bumble-bee, *i85
Butterflies, 174
Byturus unicolor, 468

Cabbage, aphis, 482

insects injurious to, 480

maggots, 482

-snakes, 86
Caddis-flies, 168
Calandra granaria, 496

C. oryzcR, 496
Calcarea, 62
Callinectes hastatus, 121

Calliphora wmitoria, *388

antennae, *i3o
Callithricidae, 318
Callorhinus alascanus, *3i6
Calosoma sycophanta, *4og
Canary birds, 333
Cancer magister, 121
Candle-fish, 252
Canidae, 313
Canine distemper, 366
Canis anthus, 325

C. aureus, 325

C. latrans, 313, 325

C. niger, *324, 325

C. occidentalis, 313, 325

C. pallipes, 325
Canker-worms, 428
Capnodium, 450
Capra cegagrus, 330

C. falconeri, 330

C. jemlaica, 330
Capronius incequalis, 466
Carassins auratus, 249
Carbon bisulphide, 418
Carcharias, 246
Carcharodon carcharias, 246
Caribou, 303
Carp, 248

Carpenter-worm, 512
Carpet-beetle, *4oi
Castor canadensis, 310
Castoridae, 306
Caterpillar, internal structure, 136,

*i37

Cat-fishes, 248
Catostomidae, 248
Cats, house, 325
Cattle, 329
Cattle plague, 366
Cavia, 308
Cebidae, 318
Cell, defined, 35

differentiation and specializa-
tion, 40

Centipede, *i25
Centrarchidae, 253
Cephalopoda, 222, 233
Ceratitis capitata, *426
Ceratophyllus fasciatus, 376
Ceratopogon spp. 386
Cercopithecidae, 318

20

INDEX

Cercopithecus, *$ig
Ceroplastcs floridensis, 460
C. cirripediformis, 460
Cervidae, 303
Cervus canadensis, 303
Cestoda, 77
Cete, 301
Cetochilus, 114
Cetorhinus, 239, 246
Chastognatha, 86
Chaatopoda, 98
Chaff-scale, 456
Chalcidae, 180
Chameleons, 265
Chelonia, 262
Chelonia mydas, 264

C. imbricata, 264
Chelura, 121
Chelydra serpentina, 263
Chenalopex egyptiaca, 332
Cherry fruit-fly, 425
Chicken-mites, 215

tick, 212

Chickens, 331, 332
Chimaeras, 247
Chimpanzee, 320
Chinch-bug, 492, *493
Chionaspis furfura, 448
Chipmunk, *3o6
Chiroptera, 312
Chitin, 127
Chiton, *22i
Chordata, 237
Chrysemmys picta, 264
Chrysomphalus auranti, *4S4

C. aonidum, 455

Chrysomyia macellaria, *387, 388
Chubs, 248
Cicada, 437

C. septemdecim, 437
Cigarette-beetle, 502
Ciliata, 34
Circulatory system, dragon-fly,

*i4o

Cirripedia, 115
Citellus tridecemilineatus, 311
Citrus fruits, insects affecting, 450
Clams, 222

geoduck, *224

hard, 223

little-neck, 223

razor, 225

Clams, soft, 223

Washington, 224
Classes, denned, 53
Classification, meaning and basis,

branches and classes, 55

and nomenclature, 51

zoological, 51
Clothes-moths, 400
Clover root-borer, 502
Ciupea, 249
Clupeidfe, 249
Cobra, 272
Coccidae, 443

Coccinella californica, *4O7
Coccus hesperidum, 453
Coccyges, 283
Cockerel, *33i
Cockroaches, 162, 397
Codfish, 253
Codling-moth, 422, *423

cocoons, *424

larva, *424
Ccecilians, 256
Ccelenterata, 63
C (Knur us cerebralis, 75
Coleoptera, 169
Colinus virginianns, *2&2
Colorado potato-beetle, *476
Columbae, 283
Columba lima, 283, 332
Condylura cristata, 311
Conorrhinus megistus, 354
Conotrachelus nenuphar, 426, *42
Copepoda, 114
Copperheads, 269, 270
Coral Islands, 67
Corals, 66, *67
Coregonus, 251
Cormorants, 280, 333
Corn ear-worm, 486

root-aphis, 492

root- worm (Western), 490
(Southern), 490

root web worm, 491

stalk-borer, 491
Corrodentia, 161
Corvidae, 285
Cotton boll-worm, 499
Cottontail, 306
Cottony-cushion scale, *459
Cougar, 313
Coyote, 313

INDEX

521

Crabs, 120

Crambus c all gino sell its, 491

Cr angon franciscorum, 118

C. mdgaris, 118
Crayfish, habits, 113

structure, 107, *iog, *m
Crickets, producing sounds, 163
Crinoidea, 97
Crocodiles, 265
Crocodilia, 262
Crocodilus americanus , 265

C. niloticus, 265

Cross-pollination of flowers, 198
Crotalus, 270
Croton-bug, *397
Crustacea, 107

classification, 113
Cryptobranchus, 256
Cryptolcemus montrouzieri, 458
Ctenocephalus canis, 376
Ctenophora, 68
Cucumber-beetle, *487
Cucu maria fron dosa, *95
Culex sp. mouthparts, *i^6

C. fatigans, 384
Currant, aphis, 470

saw-flies, 469

stem-girdler, 469
Cuttlefishes, 233
Cut-worms, 484, *4&5

climbing, 432
Cyclops, *H4
Cyclostomata, 239
Cydia pomonella, 422, *423, *424
Cygnus atratus, 333

C. nigricollis, 333

C. olor, 333
Cyllene robinice, 511
Cynipidae, 181
Cynomys ludoviciamis, 311
Cypridina, 114
Cyprinidae, 248
Cyprinus carpio, 248
Cypris, 114

Damsel-flies, 158
Dark currant-fly, 471
Dasyatis, 247
Decapoda, 116
Decapods, 235
Deer, 303
Delhi boil, 354

Delphinida;, 302
Dendroctonus , 515
Dendrostomum cronihelmi, "103
Dermacentor venustus, 364
Dermanyssus gallince, 215
Development, embryonic, 45

in metazoa, 43

post embryonic, 45
Devil-fish, *234
Diabrotica longicornis, 490

i2-punclata, *48j, 490

D. mttata, 486
Diatr&a zeacolella, 491
Diddphys virginiana, 300
Dimorphism, 65
Dinosaurians, 261
Dipneusti, 255
Dipnoi, 255
Dipodidae, 306
Diptera, 170
Disease and shell-fish, 228

and parasites, 349
Dissosteira Carolina, *i4o
Dobson-fly, 167

Dog, 3.13, 324
Dolphins, 302
Donkeys, 327
Doris tuberadata, *233
Dourine, 355
Doves, 283
Dragon-flies, *is8

nymph, *i59
Duck-bill, 300
Ducks, 280

domestic, 332
Dugongs, 301
Dysentery, amoebic, 350
Dyticus sp. *i(x)

Eagles, 283

Ear-shells, 232

Earthworm, cross section, *io2

habits, 98

dissection, *ioo

structure, 99
Earwigs, 164
Echidna, 300
Echinodermata, 89
Echinodoris sp. *233
Echinoidea, 95
Echinorhynelus gigas, 87
Ecology, 346

522

INDEX

Ectobia germanica, *$w
Eels, 249
Eel- worms, 80
Egg, fertilization, 46
Elaphidion villas um, 513
Elaps fttlvius, 270
Elasmobranchii, 245
Electric-rays, 247
Elephant-fishes, 247
Elephantiasis, 84
Elk, 303
Elm, aphis, *5i2

leaf-beetles, 511
Embiotocidae, 253
Embryology, 45
Embryonic development, 45
Emulsion, kerosene, 416

distillate oil, 416

carbolic acid, 417
Endentata, 300
Engraulidae, 250
Entero-hepatitis, 351
Entomostraca, 113
Eohippus, 325
Ephemeridae, 156
Ephestia kuehnietta, 497
Epitrix sp. 477

E. parvida, 501
Epochra canadensis, 470, *47i
Equus, 326

E. caballus fossilis, 325

E. onager, 327

E. przewalski, 325

E. tceniopus, 327
Erethizon dorsatus, 308

E. epixanthus, 308
Erethizontidae, 306
Eriophyes, 213

E. pyri, 434
Ermine, 314
Esocidae, 252
Euglena, 34
Eulachon, 252
Eumetopias stelleri, 318
Euplexoptera, 164
Euproctis chrysorrhcea, *5O9
European fruit-Lecanium, 448
Eutettix tenetta, 483
Euthrips pyri, 433
Evolution, 335

factors, 336

proof, 344

Eyes, compound, 130
facets, *i32

longitudinal section, *i3i
simple, 132

Fasciola hepalica, 70, *7i

F. magna, 72
Families, defined, 52
Feather-stars, 97
Felidae, 312
Felis concolor, 313

F . maniculata, 325

F. pardalis, 313

F. onca, 313
Feridae, 312
Fertilization of egg, 46
Fiber zibethictis, 309
Fidia mticida, 465
Field and forage crops, insects

affecting, 489
Fig- wasp, 181
Filaria bancrofti, 84

F. loa, 86

F. medinensis, 86
Filaria in mosquito, *384
Fish culture, 242
Fishes, 239, 247

epidemics among, 365
Flat-worms, 69

classification, 77
Flea-beetles, 477
Flea, 172

cat and dog, 173, 376

human, *i73, *376

plague, 375, 376

rat, 376
Flesh-flies, 388
Flies, two- winged, 170
Flounder, 253, *254
Foraminifera, 33
Forest and shade trees, insects

affecting, 506
Foxes, 313
Fringe- wings, 166
Fringilla canariensis , 333
Fringillidae, 285
Frog, *4, 257

external structure, 5

internal structure, 6

life-history and habits, 12

skeleton, *n

INDEX

523

Gadidae, 253

Galerucella htteola, 511

Galleria mellonella, *iQ5

Galley- worm, 124

Gall-flies, 181

Gallinae, 282

Callus bankiva, *332

Garden truck, insects affecting, 475

Gar-pikes, 248

Gastrophilus equi, *^8g

larvae, *3go
Gastropoda, 222
Gastropods, marine, 231
Gavial, 265

Gavialis gangeticus, 265
Geese, 280

domestic, 332
Genus, denned, 51
Geomyid<z, 306
Gephyrea, 98
Gibbons, 319
Gid, 75

Gila monster, *266
Gipsy moth, *507

larva, *5o8
Glires, 305
Glossina morsitans, 353

G. palpalis, 353
Glover's scale, 456
Glugea bombycis, 364
Glycimeris generosa, *224
Goat, Rocky Mountain, 304, 330
Goldfish, 249, 333
Gonionema vertens, *65
Gophers, 308
Gorilla, 320
Gorilla gorilla, 320
Grain aphis, 496

beetle, saw-toothed, *497

moth, Angumois, 497

weevil, 496
Grantia, 58
Grape curculio, 466

-berry moth, 466

leaf-hopper, 466

imported root-worm, 466

root-worm, 465
Grape-vine, phylloxera, 463, *464

flea-beetles, 466
Grasshoppers, control, 504

external structure, 14, *i8

immature stages, *i4

Grasshoppers, internal anatomy, 18
mouth-parts, *i44
producing sounds, 163

Grayling, 252

Green-fruit worms, *432

Gribbles, 122

Ground-hog, 310

Grubs, 503

Guinea-pigs, 308

Guinea-worm, 86

Gulls, 280

Gulo luscus, 314

Gymnonychus appendiculatus, 469

Hwmatobia serrata, 387
Hcematopinus, 394

//. asini, *393
Hamonchus contortus, 81
Hag-fish, 239
Hair-snakes, 86
Halibut, 253
Haltica sp. 466
Hares, 306

Harlequin cabbage-bug, 482
Harvest-mites, 213
Hawks, 283
Heliothis obsoleta, 486
Heliothrips fasciata, 480
Hell-bender, 256
Hellebore, white, 415
Hell-grammite, 167
Heloderma, 266

H. suspectum, *266
Hemerocampa leucostigma, 431

//. velusta, *430, *43i
Hermit-crabs, n8, *iig
Hemiptera, 164
Hemispherical scale, 453
Heredity, 338
Herodiones, 281
Herring, 249

lake, 252
Hesperina, 179
Hessianrfly, *494
Heterocera, 179
Heterodon, 269
Heteroptera, 165
Hip pa, 1 20
Hirudinea, 98
11 ir iido medicinalis, *io4
Hirundinidae, 285

524

INDEX

Histogenesis, 152
Histolysis, 152
Hogs, 327
Holocephali, 247
Holothuroidea, 96
Homarus americanus, 117

H. grammaris, 117
Hominidas, 320
Homoptera, 165
Homo sapiens, 320
Honey-bee, 184, 185. *i86,*334,

antenna, *i3o

external structure, *i27

legs, *i33

mouth-parts, *i2Q

queen, drone, worker, *i86

reproductive organs, 143

ventral view of worker, *i9i
Hookworm, *82

disease, 81

Old World, *83
Horned toad, 267
Horn-flies, 387
Horn-worms, 499
Horse-fly, *i7i, *386
Horses, 325, *327

four-toed, 326
House-fly, and disease, 377, *3?8

foot, *38o

head, '379

larvae and pupa?, *38i

mouth-parts, *i47
Hydra, longitudinal section, *23

structure and habits, 21, *22
Hydrocyanic acid gas, 418
Hydrodamalis gigas, 301
Hydroids, 64
Hydrozoa, 64
Hyla versicolor, 258
Hylastinus obscurus, 502
Hylidas, 258
Hymenoptera, 179
Hypoderma lineata, *39O

larvae, *39i

H. bovis, 390

Icerya purchasi, 407, *4o8, *459

Ichneumon-fly, *i8i

Ichneumonidae, 180

Icthyosaurians, 261

Iguanas, 267

Imported grape root-worm, 466

Imported cabbage-worm, 480, *48i

current-borer, *^6g
Infantile paralysis, 366
Infusoria, 34
Insecta, 125
Insecticides, 413
Insectivora, 311
Insects, 125

antennae, 129, *i3o

classification, 153

controlling, 403

natural enemies, 405

parasites, 407, 408

predaceous, 407

senses, 129
Ipidae,5i5

I PS, 5i5

Iridomyrmex humilis, 398, *399
Ischnochiton magdalenensis, *22i
Isolation, 343

Isopod, *I2I

Isopoda, 121
Isoptera, 159
Isosoma tritici, 495
I. grandi, 495
Itch-mite, *2i4
Ixodes ricinns, *2io
Jaguar, 313
Janus integer, 469
Jelly-fishes, 64, *6$
Jew-fish, 253
Jiggers, 213

JtlluS Sp., *I24

Kangaroo, 300

Katydids producing sounds, 163
Kiwi, 274

Ladybird-beetle, *4O7
Lake-flies, 156
Lamellibranchia, 221
Lampreys, 239
Lampropcltis boyli, *26g
Lamp-shells, 88
Lancelet, 238
Lasioderma serricorne, 502
Lasiurus borealis, 312
Lasius brunneus, 492
Latax kttris, 314
Laterodectus mactans, 207
Lead, arsenate, 415
Lecanium corni, *448
Leeches, 104

INDEX

525

Lcishmannia donovani, 354
Lemuroidea, 318
Lemurs, 318
Leopard-moth, 513
Lepas hiUi, *ii5
Lepidoptera, 174
Lepidosaphes becki, 455

L. gloveri, 456

L. ulmi, 447
Lepisma sp. *i55

L. domestica, 156

L. saccharina, 155
Lepisosteidae, 248
Leporidae, 306
Leptinotarsa decemlineata, *
Leptocardii, 238
Leptocephalidae, 249
Lepus texanus, 307

L. syfaaticus , 306
Leucandra apicalis, *sg
Leucania unipuncla, *48s
Lice, 392

bird, 395
Life processes, 42
Ligyrus gibbosus, antennae, *
Limicolae, 281
Limnoria, 122
Limulus, 121
Lions, 312

Lipeurus baculus, *i62
Lithobians, 124
Liver-flukes, 70, *ji
Lizards, *266
Lobster, 116
Locust-borer, 511
Loligo opalescens, *235
Longipennis, 280
Louse, body, *392

chicken, *394

crab, 394

head, 393

horse, *393
Lucilia, 388
Lumbricus sp., *ioo
Luna-moth, *i78
Lung-fishes, 255
Lutra canadensis, 314
Lutreola, 314
Lynx, 313
Lynx canadensis, 313

L. rufus, 313
Lysiphlebus testaceipes, 496

Machera palula, 225
Mackerel, 252
Macrochelys lacertina, 263
Macrochires, 283
M acrodactylus sttbspinosits, 466
Macrosiphum pisi, 480
Macrura, 116

M alacoclemmys palustrus, 264
Malacosoma americana, 427, *429
' Malacostraca, 116
Mai du coil, 355
Malarial mosquito, *36o

parasite, *358
Mai de coder as, 355
Mallophaga, 161, 395
Mammalia, 295
Mammals, 295

body, form and structure, 295

classification, 299

development and life-history,

AT 2"

Man, 320

Manatees, 301

Mange-mite, 214

Mantidae, 162

Mantis, 162

Margaropus annnlatus, *362

Marine protozoa, 32

worms, *io3
Marmosets, 318
Marmolta, 310
Marsupialia, 300
Mastigophora, 34
Mayetiola destructor, *494
May-fly, *is6
Mealy-bug, *457, *4s8
Mecoptera, 167
Medicinal leech, *io4
Mediterranean flour-moth, 497

fruit-fly, *426
Medusae, 64, *65
Melanerpes erythrocephalus, *284
Melanoplus spretus, 164
Melanotus variolatus, antenna, *i3O
Meleagris gallopavo, 333
Melittia satyriniformis , 487
Melospiza cinerea, *28?
Mendelian principles, 339
Menhaden, 250
Menopon pallidum. *394, 395
Mephitis, 314
Mermis albicans, 86

526

INDEX

Mesohippus, 326
Metamorphosis, 149

complete, 150, *i5i

incomplete, *i49
Metazoa, 39

reproduction and development,

43

Mice, 309, 310
Microfilaria, *8s
Microtus, 310
Milliped, *i24
Minnows, 249
Mink, 314
Miscible oils, 417
Mistichthys, 239
Mites, 212
Mole, 311
Mollusca, 216
Molluscoida, 88
Monarch butterfly, metamorphosis,

ISI

Monkeys, 318
Monomorium minimum, 399

M. pharaonis, 398
Monophadnoides rubi, 468
Monotremata, 299
Monotremes, 299
Moose, 303
Mosquitoes, control, 371

eggs and larvae, *368

life-history and habits, 368

malaria-carrying, 369

mouth-parts, *i46

pupae, *3&9

yellow fever, 373
Moth, 174

codling, *423

clothes, 400

oak-tree, *4io

tussock, *43o
Mouth-parts, different types, 143

grasshopper, *i44

honey-bee, *i29

house-fly, *i47

mosquito, *i46

sphinx-moth, *i48

water-bug, *i4S
Mud-eels, 256
Mugilidae, 252
Mullet, 252

Multiceps multiceps, 75, *^6
Murgantia hislrionica, 482
Muricidae, 232

Murrina, 355

Mitsca domestica, *378

mouth-parts, *i47
Mus decumanns, 309

M. muscnlus, 310

M. rattus, 309
Muskrat, 309
Mussels, 222

fresh water, 216

and buttons, 220

and pearls, 220

sea, *223
Mustelidae, 314
Mustelus, 246
Mutation, 336
Mya arenaria, 223, *224
Mycetozoa, 35
Myotis subulatus, 312
Myriapoda, 123
Myrmeleon sp. *i67
Mytilus edulis, *22$
Myxosporida, 365
Myzus ribis, 470

Nagana, 354

Naja tripudians, 272

Natrix, 269

Nautilus, chambered, 236

paper, 235

Necator americanus, *82
Necturus, 256
Nemathelminthes, 79

classification, 86
Nematoda, 86
Nematomorpha, 86
Neotoma pennsylvanica, 309
Nephrops norwegicus , 118
Nereis, sp., 103
Neuroptera, 166
Nicotine solutions, 417
Noctiluca, 34
Non-calcarea, 62
Notophthalmus lorosus, *2$7
Notropis, 248

Novius cardinalis, 407, *4o8, 460
Nudibranchs, *233

Oak-tree moth, *4io

pruner, 513

twig-girdler, *5i3
Oberea bimacula, 468
Ocellus, 132
Ocelot, 313

INDEX

527

Octopods, 234

Octopus, 233, 234

Odobenidas, 318

Odobenus obesus, 318

Odocoileus, 303

Odonata, 158

Oestridae, 389

Oestrus ovis, 391

Oncorhynchus , 250

One-cell animals, 39

Onion-maggot, 488

Onycophora, 123

Ophibolus, 269

Ophiuroidea, 95

Opossums, 300

Orang-utans, 319

Orca, 303

Orcamnos montanus, 304

Orchard pests, 421

Orders, denned, 52

Organs and functions,

principal systems, 43

Ornithodorus moubata, 212,

Ornithorhynchus, 300

Orohippus, 326

Orthoptera, 162

Ostracoda, 114

Ostrea angulata, 227
O. edulus, 227
O. lurida, *226
O. virginiana, 225

Ostriches, *279, 333

Otariidae, 316

Otter, 314

Oviparous, 260

Ovis arkal, *S29, 33°
0. canadensis, 304
O. musimon, 330
O. tragelaphus, 330

Ovoviparous, 260

Ox warble-fly, *39O
larva, *39i

Oysters, 225
pearl, 228

Oyster-shell scale, 447

Pagarus sp., *ii9
Paleacrita, vernata, 429
Palinurus. 118
Paludicolae, 281
Pan troglodytes, 320
Papaipema nitella, 478

Papirius maculosus, *i55
Paramcecium, structure and habits,

29, *3Q
Parasita, 165
Parasites, and disease, 349

denned, 350
Paris green, 414
Parlatoria pergandi, 456
Passeres, 283, 285
Paw cristatus, 333
Peach-borer, 434
Peach twig-borer, 435
Peacocks, 332
Pear-leaf blister-mite, 434
Pearl-oysters, 228

shell, *229
Pearls, 77

and mussels, 220
Pear thrips, *433
Pea aphis, 480

weevil, 478
Pebrine, 364
Pecten, 224
Pediculidae, 392, 393
Pediculus capitis, 393

P. vestimenti, *392, 393
Pegomyia brassicce, 482

P. ceparum, 488
Pelecypoda, 221
Pellagra, 384
Pemphigus beta, 484
Pentacrinus sp., *g6
Perch, 253
Percida?, 253
Peripatus, 123

P. eiseni, *i23
Periplaneta americana, 397

P. auslralasia, 397

P. orientalis, 397
Perissodactyla, 303
Petromyzon, 239

P. marinus, *2^g
Pheasants, 282, 333
Phlososinus cristatus, injury, *5i4
Phlebotomus pappataci, 385
Phlegethontius quinquemacidata,

*5°°

P. sextata, 500
Phoca mtulina, 315

P. grwnlandica, 316
Phocidae, 315
Phoebe, *4o6

528

INDEX

Phryganidia californica, *4io

Phrynosoma, 267

Phthorimcea operculella, 478, 501

Phyllopoda, 113

Phylloxera vastatrix, 463, *464

Physeteridae, 302

Phytonomus murinus, 502, *5O3

Pici, 283

Pickerel, 252

Pigeons, 283

domestic, 331

passenger, 283
Pike, 252

wall-eyed, 253
Pimpla conquisitor, *i8i
Pinnipedia, 315
Piroplasma, 362
Pisces, 239
Plague and fleas, 375
Planarians, 69
Planaria, sp., *7o
Plant-lice, 437
Planula, 64
Plasmodium, 357

P. falciparum, 359

P. malarial, 359

P. vivax, 359

Plathemis trimaculata, *i58
Platyhelminthes, 69
Platypus, 300
Plecoptera, 157
Pleuronectidae, 253
Plum-curculios, 426, *427
Poliomyelitis, 366
Polychrosis viteana, 466
Polymorphism, 65
Polyna brevisetosa, *io3
Polynices lewisi, *2$2
Polypus, 234

P. apollyon, *2$4
Polyzoa, 88

Pontia rapes, 480, *48i
Porcupines, 308
Porifera, 62
Porpoises, *3O2
Porthetria dispar, *SO7
Portugese man-of-war, 65
Post-embryonic development, 45
Potato stalk-borer, 477

tuber-worm, 478
Prairie-dogs, 311
Prawns, 118

Primates, 318
Prionoxystns robinae, 512
Pristis peclinatus, 247
Proboscidia, 303
Proctotrypidae, 180
Procyonidas, 315
Prater os pongia, 35
Protohippus, 326
Protophyta, 32
Protoplasm, 35
Protorohippus, 326
Protozoa, classification, 34

parasitic, 34

reproduction in, 37
Pseudococcus citri, *4$8, *4S7
Psendopleuronectes americann-s,*2^4
Psittaci, 283
Psocidae, 161
Psoroptes communis, 214
Pier onus ribesi, 469
Pterosauria, 260
Plerostichus calif ornicus , antenna,

.*i30

Pthirius inguinalis, 394
Publications, Government, 419
Pulex irritans, *i73, 376
Pulicidae, 172
Puma, 313

Purple scale, 455, *456
Putorius erminea, 314
Pygopodes, 280
Pyrethrum, 418
Python, 272

Quail, *282

Rabbits, 306

domestic, 331
Raccoons, 315
Radiolaria, 33
Railroad-worm, 425
Raja erinacea, *2$6, 247

R. Icevis, 247
Rana catesbiana, 257
Rangifer caribou, 303
Ranidae, 257
Raptores, 283
Raspberry byturus, 468

cane-borer, 468

root-borer, 467

saw-fly, 468
Rasores, 282

INDEX

529

Ratitas, 279
Rats, 309
Rattlesnakes, 269

head, *2fi

rattles, *2jo
Rays, 247

Red-necked cane-borers, 468
Red scale, *454
Red spider, 212
Reindeer, 303
Relapsing fever, 356

tick, *3S6
Repellents, 419
Reptilia, 260
Resin spray, 417
Rhagoletis cingu-lata, 425

R. pomenella, 425

R. ribicola, 471
Rhizopoda, 34
Rhiptoglossi, 265
Rhopalocera, 178
Rhynchocephalia, 262
Rice- weevil, 496
Rocky Mountain fever, 364
Rodents, 305
Rosalina varians, *33
Rose-chafer, 466
Rose scale, *468
Rotifers, *87

Sacculina, 116

Saissetia hemisphcerica, 453

S. olece, 452, *453
Salamander, *257
Salmo irideus, * 251

S. salar, 251
Salmon, 250
Salmonidae, 250
Salvelinus, 251
Sand-bugs, 120
San Jose scale, 445, *446
Sanninoidea exitiosa, 434

S. opalescens, *434, *43S
Saperda Candida, 436
Sapphirina, 114
Sap-suckers, 285
Sarcophaga, 388
Sar copies scabiei, 213, *2i4
Sardinella, 249
Sardines, 249
Sauria, 265
Saw-fish, 247

Saw-flies, 180
Saxidomus nuttatti, 224
Scab-mite, 214
Scale insects, 443
Scalops aquaticus, 311
Scaphopoda, 222
Sceloporus occidentalis, *266
Schistocerca americana, "163
Schizoneura lanigera, 440, *44i

S. nlmi, *si2
Schizothoerus nuttalli, 224
Sciuridas, 306
Sciuropterus volans, 310
Sciurus carolinensis , 310

5. hudsonicus, 310

S. litdovicianus, 310

S. niger, 310
Scolopendra, 124, *i2S
Scolyius, 515
Scombridae, 252
Scorpion-flies, 167
Scorpions, 206
Screw-worm fly, *387, 388
Scurfy-scale, 448
Scutellisla cyanea, 452
Scutigera forceps, 124
Scyphozoa, 66
Sea-anemones, *63, 66

cows, 301

cucumbers, *95, 96

lily, *96, 97

mats, 88

slugs, 233

squirts, 237, *238

urchin, *94, 95
Sea-lions, 316, 318
Seals, 315

fur, *3i6
Segregation, 343
Selection, artificial, 321, 342

natural, 342
Serpentes, 265
Serphus dilatatus, "165

mouth-parts, "145
Serranidae. 253
Sesia rutilans, *4?2, 473
Sex, 46
Shad, 249
Sharks, 245
Sheep, *330

Rocky Mountain, 304

wild, *329

53°

INDEX

Shell- fish and disease, 228

Ship-worms, 229

Shrews, 311

Shrimps, 118

Sialidae, 167

Silk- worm, *ij6, 334

diseases, 364

Silpha ramosa, antenna, *i3o
Siluridae, 248

Silvanus surinamensis , *4Q7
Silver-fish, 155, 156
Simiidae, 319
Simulidae, 385
Simulium, *386
Siphonaptera, 172
Siren, 256
Sirenia, 301

Sitotroga cerealella , 497
Skates, *246, 247
Skunk-bear, 314
Skunks, 314
Sleeping sickness, 352
Slime moulds, 35
Slime slugs, 123
Sloths, 300
Slugs, 231
Smelt, 252

Smynthurus hortensis, 155
Snails, 230

Snake-bites, treatment, 271
Snakes, 267

coral, 270

garter, *268

king, *26g

water, 269
Snow-flea, 167
Soft brown-scale, 453
Sow-bug, *i2i
Sparrow, *287
Species, defined, 51
Spermophiles, 310, 311
Sphargis coriacea, 264
Sphecina, 183
Spenophorus sp., 491
Sphinx-moth, mouth-parts, "148
Spiders, 206

hour-glass, 207
Spilogale, 314
Spirochceta, 356

S. duttoni, 357

S. marchouxi, 357

5. novyi, 357

Spirochceta pallidula, 357

S. recurrentis, 357
Spirochaetae, 34
Spirochaetes, 355
Spirochaetosis, 357
Sponges, bath, *6i

boring, 62

classified, 62

structure, 58

vase-shaped, *59
Spontaneous generation, 36
Sporozoa, 34, 357
Spotted fever, 364
Spring-tail, *iss
Sqstabu, 246
Squamata, 262
Squash-vine borer, 487

bug, 487

Squids, 233, *23S
Squirrels, 310
Stable-fly, *366, 382, *383
Star-fish, cross section of ray,

*92

dissection, *go

structure, 89
Steganopodes, 280
Stegomyia fasciala, 373, *374
Sting-rays, 247
Stomach- worm, 81
Stomoxys calcitrans , *365, *383,

.387

Stone-flies, *i57
Strawberry crown-borer, 472

crown-moth, 473

root-louse, 473

root- worms, 473

weevil, 473

Striped cucumber-beetle, 486
Strongylocentrotus franciscaniis, *94
Strnthio camelus, 279, 333
Sturgeons, 247
Suckers, 248
Sulphur-lime, 415
Sunfishes, 253
Surf-fish, 253
Surra, 354
Sus scrofa, 327

5. viftatus, 329
Swamp fever, 366
Swans, 280, 333
Sympetrum illoliim, *i59
Syphilis, 357

INDEX

53i

Tabanidae, 387

Tabanus punctifer, *iyi, *386
Tachina-fly, 408, *4og
Tcenia saginala, *74, *75

T. solium, 73
Tapes staminea, 224
Tape-worms, 73, *74
Tarantulas, 208
Tatu novemcinctum, 301
Taxidea, 315
Teleostomi, 247
Tent-caterpillars, 427, *42g, 511

tent, *428, *SIQ
Tenthredinidae, 180
Teredo, 229
Termes flavipes, 160
Termites, 159, *i6o
Termopsis augusticollis, 161
Terrapins, 263
Testudo, *263, 264
Telramorium caspilum, 399
Tetranychus bimaculatus, 212

T. mytilas pidis , 213

T. sexmaculatus , 213
Texas fever, 362

tick, *362

Thais lamellosa, *2$2
Thalcectos maritimus, 315
Thamnophis, 269

T. parietalis, *268
Theobaldia incidens, eggs, larvae,
*368

female, *37o

male, *37i, *372

pupae, *369

Thorn-headed worms, 87
Thread-worm, 80
Thrips, 1 66
Thymallidae, 252
Thysanoptera, 166
Thysanura, 155
Ticks, 209

castor-bean, *2io

disease-carrying, *3S6, *362

fowl, *356

relapsing fever, *356
Tiger, 312

Tinea pellionella, *4OO
Tmetocera ocellana, 432
Toad, *2S8
Tobacco flea-beetle, 501

extracts, 417

Tobacco leaf-miner, 501

-worms, 499, *5<x>
Tortoise, 262, *263
Toxoptera graminum, 496
Tree-frogs, 258
Trematoda, 77
Treponema pallidum, 357
Trichechus latirostris , 301
Trichina, 79, *8o
Trichinella spiralis, 79
Trichobaris trinotata, 477
Trichoptera, 168
Trionyx, 263
Triopha modesta, *233
Trochelminthes, 87
Tropasa luna, *ij8
Trout, 251
Trypanosoma brucei, 354

T. cruzi, 354

T. equinum, 355

T. equiperdum, 355

T. evansi, 355

T. gambiense, *352

T. hippicum, 355

T. lewisi, 352
Trypanosomes, 352
Tsetse-fly, *353

disease, 354
Turbellaria, 77
Turdidae, 285
Turkey, 333
Turtles, 262, 263
Tussock-moth, *43O, *43i, 511

white-marked, 431
Tyloderma fragarice, 472
Typhlocyba comes, 466

T. mdnerata, *4-6f
Typhoid and flies, 380
Tyrannidae, 285

Uca spp., 121

Uncinararia duodenalis, 84

Uncinariasis, 81

Ungulata, 303

Unionicola, 220

Urochorda, 237

Urodela, 256

Urosalpinx, 232

Ursidae, 315

Ursus americanus, 315
U. horribilis, 315
U. middendorffi, 315

532

INDEX

Variation, 336

Ventral nerve cord, locust, *i4o
Venus mercenaria, 223
Vertebrates, denned, 237
Vespa sp., *i84
Vespina, 183
Vinegar eel, *79

Vineyards, insects injurious to, 462
Vision, mosaic, 131
Volvocinas, 40
Vol-vox, 35

Vorticella, structure and habits, *3i
Vulpes fulvus, 314
V. lagopus, 314

Walrus, 318
Wapiti, 303
Wasps, 183

digger, "183

Water bug, mouth-parts,* 145
Water-dog, 256

moccasin, 269

tiger, *i6g
Wax-scale, 460
Weasel, 314
Web-worm, 484
Whale-oil soap, 417
Whales, 302
Wheat, joint-worm, 495

straw-worm, 495
Wheel animalcules, *8?

White-ants, 159
Whitefish, 251
White-fly, 451
Wire-worms, 503
Wolf, *324
Wolverine, 314
Wolves, 313
Woodchucks, 310
Wood-lice, 121
Woodpecker, *2&4

Xenopsylla cheopus, 376

Xylina antennala, *432

X. grotei, 432

Yaws, 357

Yellow currant-fly, 470, *47i

Yellow fever, cause, 365
commission, 373
and mosquitoes, 373
mosquito, *374

Yellowjacket, *i84

Zalopus calif ornianus, 318
Zamenis constrictor, 269
Zapodidas, 306
Zeuzera pyrina, 513
Zilla calif arnica, *2Of
Zooids, 64
Zoology, defined, 2

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