Practical zoology

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tical zoo

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PRACTICAL ZOOLOGY

THE MACMILLAN COMPANY
NEW YORK - BOSTON - CHICAGO - DALLAS
; ATLANTA + SAN FRANCISCO
MACMILLAN & CO., LimiteD
LONDON + BOMBAY + CALCUTTA
MELBOURNE
THE MACMILLAN CO. OF CANADA, Ltp.
TORONTO

PRACTICAL ZOOLOGY

BY

ROBERT W. HEGNER, Pu.D.

ASSISTANT PROFESSOR OF ZOOLOGY IN THE UNIVERSITY OF MICHIGAN 3
FORMERLY TEACHER OF NATURE STUDY IN THE SCHOOL OF EDUCA-
TION, UNIVERSITY OF CHICAGO, AND PROFESSOR OF BIOLOGY IN
THE STATE NORMAL SCHOOL AT RIVER FALLS, WISCONSIN ;
AUTHOR OF “INTRODUCTION TO ZOOLOGY,” ‘ COLLEGE
ZOOLOGY,” AND “ THE GERM-CELL CYCLE IN ANIMALS ”

New Work
THE MACMILLAN COMPANY
IQI5

All rights reserved

L

CopyRIGHT, 1915,

By THE MACMILLAN COMPANY.

Set up and electrotyped. Published September, 1915.

Norwood Ipress
J. 8. Cushing Co. — Berwick & Smith Co.
Norwood, Mass., U.S.A.

PREPACE

Tuts book is intended for the use of students in secondary
schools. It includes sufficient material for an entire year’s
work, but certain chapters or parts of chapters may be elimi-
nated if less time is available. The large number of chapters
and their short length make elimination easy and also facilitate
the assignment of lessons. For example, the book may be
adapted for a half year course by omitting chapters III, XII,
XIV, XVI-XVHI, XX-XXIV, XXVIII, XXX, XXXV, and
XXXIX. The word “practical” in the title has been chosen
since an effort has been made to present those facts and theories
about animals which will have the most practical bearing upon
the daily life of the student. It refers not alone to the eco-
nomic side of the subject but also to the elements that are of
greatest intellectual value.

Ideas differ considerably as to what constitutes the best course
in zoology for secondary schools, but we cannot be far wrong if
we succeed in combining a general knowledge of animals and
of zoological principles with a discussion of the relations of
animals to man, in such a way as to ¢n/erest the students. The
constant references to the relations of animals to their environ-
ment and the selection of common animals, especially those of
economic importance, for illustrative purposes tend to stimulate
the natural interest of boys and girls in animal life.

Many of the illustrations are from photographs which show
the living animals in their natural environment. Next to the
animals themselves, photographs of this kind furnish the best
idea of the species studied. The drawings representing ana-
tomical structures have been selected so as not to duplicate

those called for in the laboratory manual.
v

.

vl PREFACE

The directions for field and laboratory work have been
grouped together in a separate booklet, thus making it easy for
the teacher to assign lessons or modify the work. This also
makes unnecessary the presence of textbooks in the laboratory.
Throughout both the laboratory manual and the textbook a too
rigid plan has been avoided, and it is therefore expected that
each teacher will be able to express his own ideas regarding
the sequence of subjects and the phases of the work to be

emphasized. :
ROBERT W. HEGNER.

ANN ARBOR, MICHIGAN,
January, 1915.

TABLE OF CONTENTS

PAGE
PREFACE . ; : . : : A : : : : v
CHAPTER I
WHERE ANIMALS LIVE .. : ; : ‘ : ; : I
CHAPTER II
THE GRASSHOPPER . ; : : : f ; : ; 8
The habits, physiology, anatomy, and economic relations
of atypical insect. Locomotion (9). Food and mouth parts
(13). Digestion (13). Circulation (14). Respiration (15).
Excretion (15). Protéction (16). Sensations (16). Ner-
vous system (17). Reproduction (18). Metamorphosis (19).
Relation to man (20).
CHAPTER III
SoME INSECT ADAPTATIONS A 5 “ . ‘ ‘ « 24
Locomotion (24). Respiration (25). Securing food (25).
Coloration (29).
CHAPTER IV
INSECTS INJURIOUS TO VEGETATION . . : : : » “32
Extent of injury (32). Army worm (33). Chinch bug
(35). Other insects injuring field crops (35). Insects injur-
ing garden vegetables (35). Insects injuring fruits (39).
Insects injuring shade trees (42).
CHAPTER V
INSECTS PARASITIC ON DOMESTIC ANIMALS AND MAN. » 48

Botflies (49). Fleas (51). Ticks (53). Lice (54).

vu

vill TABLE OF CONTENTS

CHAPTER VI

INSECTS OF THE HOUSEHOLD. . : é : : ¢

Silver fish (57). Cockroaches (57). Ants (58). Cheese

skipper (59). Meal worm (60). Carpet beetle (60). Clothes
moth (60).

CHAPTER VII

BENEFICIAL INSECTS .« : ‘ ; : : : :
Silkworm (62). Honeybee (63). Cochineal, lac, etc. (65)

Food for man (67). Scavengers (67). Pollinization of
flowers (68). Predaceous insects (70). Parasitic insects

(71).

CHAPTER VIII

THE HousE FLY AND DISEASE

Disease germs (73). Bacteria (73). Germ diseases trans-
mitted by house flies (77). Typhoid fever (78). Dysentery
(78). Tuberculosis (79). Asiatic cholera (79). Other dis-
eases (79). Methods of control (80). Breeding habits of
house flies (80). Enemies of house flies (81). Prevention
of breeding (82). Prevention of distribution of germs (83).
Control by department of health (84). Example of a city fly
campaign (85).

CHAPTER 1X

MOSQUITOES AND DISEASE

How germs are carried (86). What the germs are (86).
THe MALARIAL Mosquiro (87). Anopheles the guilty
mosquito (88). Losses due to malaria (89). Breeding habits
of anopheles (g0). Enemies of mosquitoes (go). Control of
mosquitoes (90). Example of mosquito control (92). Driving
away mosquitoes (92). Tur YELLOW FEVER Mosquito
(93). Control in New Orleans (93). Control in Panama Canal
Zone (94). Control by school children (95). Mosquitoes
and other diseases (96).

PAGE

57

62

73

86

TABLE OF CONTENTS ix

CHAPTER X
PAGE
OTHER INSECTS THAT TRANSMIT DISEASE GERMS . : . 98
Fleas and bubonic plague (98). Control of plague in San
Francisco (98). Blood-sucking flies and disease (99). Bed-
bug and disease (100). Sucking lice and disease (100).

CHAPTER XI

CLASSIFICATION IN GENERAL AND OF INSECTS IN PARTICULAR . 102
Artificial classification (102). Natural classification (102).
Structure and life histories in classification (103). System of
classification used by scientists (103). Reasons for existence
of classification (105). Value of classification (106). Necessity
of scientific terms (106). Classification of insects (107).

CHAPTER XII
SPIDERS AND OTHER ARACHNIDS . . : : : . TIL

Where spiders live (111). Spiders with and without webs
(111). Types of webs (111). How webs are built (113).
Spinning organs (113). How insects are captured (114).
Sense organs (114). Respiration (114). Reproduction (114).
Aérial spiders (115). Water spiders (116). Trapdoor spider
(117). Tarantulas (117). Spider bites (118). Harvestmen
(118). Scorpions (118). Mites and ticks (119). King crab
(119). Characteristics and classification of Arachnida (119).

CHAPTER XIII

THE RELATIONS OF ARACHNIDS TO MAN . : : ;

Arachnids destroy insects (121). Spider silk (121).

Mites and ticks (121). Texas-fever tick (121). Chicken

mites (124). Fowl ticks (124). Mites which cause scab and

mange (125). Itch mite (125). Harvest mites or jiggers

(125). Face mites (126). Spotted-fever tick (126). “Red
spiders” on plants (126). Gall mites (127).

CHAPTER XIV
THE MYRIAPODA OR CENTIPEDES AND MILLIPEDES . : . 128

Millipedes (128). Centipedes (128). Characteristics and
classification (129).

x TABLE OF CONTENTS

CHAPTER XV

THE CRAYFISH : : : ‘ : ;
Habitat (130). Means of protection (130). Sensitiveness
to surroundings (132). Locomotion (133). Food and di-
gestion (133). Absorption and circulation (134). Respira-
tion (134). Reproduction (134). Relations to man (135).

CHAPTER XVI

CRUSTACEA IN GENERAL : . : : F :

Crabs (138). Barnacles (139). Fresh-water crustacea (140).

Relations of crustacea to man (142). Value of crustacea

as food for fish (142). Injuries due to crustacea (143).
Characteristics and classification (143).

CHAPTER XVII

THE MUSSEL OR CLAM AND OTHER BIVALVEsS . : .

Habitat (145). Locomotion (146). The protective shell

(146). Structure of the shell (148). Movement of valves

of shell (148). Water current in the mussel (148). Principal

parts of the body (149). Respiration (149). Sensitiveness

to the surroundings (150). Digestion (150). Circulation

(151). Reproduction (151). The oyster (153). Soft-shell

clam (155). Razor-shell clam (156). Hard-shell clam (156).
Scallop (156). Classification of mussels and clams (157).

CHAPTER XVIII

A LAND SNAIL AND OTHER MOLLUSKS : : :
Life on land (158). Protection (158). Locomotion (159)
Sensitiveness to surroundings (160). Method of feeding
(160). Respiration (161). Slugs (161). Fresh-water snails
(162). Marine gastropods (163). Cephalopods (165). The
relations of mollusks to man (166). Characteristics and

classifications of mollusks (167).

CHAPTER XIX

THE EARTHWORM AND OTHER SEGMENTED WORMS.

Need of moisture (168). Burrows (168). Locomotion
(168). Food (171). Digestion (171). Circulation and ex-

PAGE
130

137

145

158

168

TABLE OF CONTENTS

cretion (171). Respiration (172). Sensations (172). Ner-
vous system (172). Reproduction (173). Economic impor-
tance (173). Segmentation (174). Body cavity (174).
Leeches (175). Fresh-water segmented worms (176). Marine
segmented worms (176). Characteristics and classification
of the Annelida (177).

CHAPTER XX

THE ROUNDWORMS
“Horsehair snakes” (178). Intestinal parasites (178).
Trichina (179). Hookworm (179). Elephantiasis (181).
Other roundworms (181). Characteristics and classification
(182).
CHAPTER XXI
THE FLATWORMS : ; : : : ‘ ; ‘
Planaria (183). Parasitic flatworms (185). The liver
fluke (186). The tapeworm (188). Characteristics and
classification (191).
CHAPTER XXII

THE ECHINODERMS : ; : : : . :
Symmetry (192). Starfishes (193). Brittlestars (195)
Sea urchins (196). Sea cucumbers (196). Sea lilies (197).

CHAPTER XXIII

THE CGLENTERATES . ae : : : : . :

Hydra (199). Digestion (203). Reproduction (203).

Regeneration (204). Division of labor among individuals of

a colony (204). Alternation of generations (205). Jellyfish

(207). Sea anemones (207). Coral (208). Characteristics
and classification (210).

CHAPTER XXIV

THE SPONGES : : : : a ‘ : ‘

A simple sponge (211). Reproduction (212). Grantia

(213). Flow of water in fresh-water sponge (214). Spicules

and spongin (215). The relations of sponges to other

organisms and to man (215). Characteristics and classifica-
tions (217)-

xi

PAGE

178

183

192

198

211

xil TABLE OF CONTENTS

CHAPTER XXV

PAGE

THE PROTOZOA . s : 5 ; : : : 5 . 218
Paramecium (218). Life activities of one-celled animals
and many-celled animals compared (221). Ameba (222).
Euglena (224). Other fresh-water protozoa (224). Parasitic
protozoa (227). The malarial parasite (227). Pathogenic
protozoa (227). Control of pathogenic protozoa (229). Pro-
tozoan parasites of domestic animals (230). Protozoa in
drinking water (230). Colonial protozoa (231). Character-

istics and classification (233).

CHAPTER XXVI

AN INTRODUCTION TO THE VERTEBRATES . ‘ . ; . 234
The body as a machine (236). Organs and systems of
organs (237). Structure of organs (239). Protoplasm (239).
Tissues (241). Living and lifeless things (242). The
origin of life (244).
CHAPTER XXVII

THE FROG, A TYPICAL VERTEBRATE ; : ; : 2 S245
Movements (245). Croaking (246). Physiological proc-
esses (246). Digestion (246). Circulation (248). Respi-
ration (250). Excretion (252). Secretion (252). Theskeleton
and its functions (254). Muscular activity (256). Nervous
activity (256). Sense organs (261). Reproduction (262).

CHAPTER XXVIII

THE LAMPREY EELS AND OTHER CYCLOSTOMES : : . 268
Form of body (268). Mouth and food (268). Respiration
(269). Sensations (269). Internal organs (269). Devel-
opment (269). Other cyclostomes (270). The brook lam-
prey (270).
CHAPTER XXIX

THE STRUCTURE AND ACTIVITIES OF FISHES . ; : S 271

Habitat (272). Form of body (272). Locomotion (272).
Protection (273). Sensations (274). Respiration (275).
Reproduction (275).

TABLE OF CONTENTS Xill

CHAPTER XXX

PAGE
SOME COMMON FISHES OF NORTH AMERICA . ‘ , « 278

ELASMOBRANCHII (278). TELEOSTOMI (279). DIPNOI
(284).

CHAPTER XXXI

THE RELATIONS OF FISH TO Man . : - ‘ : . 285
Game fishes (285). Food fishes (288). The canning of
salmon (292). The value of the fishing industry (293). The
artificial propagation of fishes (294). The artificial propaga-
tion of the lake trout (295). | Work of the United States
Bureau of Fisheries (296).

CHAPTER XXXII

THE AMPHIBIA . : ‘ : 3 : A : . 299
Tailed amphibians (299). Tailless amphibians (301).
Regeneration (304). Hibernation (305). Poisonous am-
phibia (305). The common toad (305). The economic
importance of amphibia (307).
CHAPTER XXXIIl
THE REPTILIA . : i 309

TURTLES (310). Habitat (314). Fresh-water turtles (314).
Terrestrial turtles (316). Sea turtles (317). LIZARDs (319).
SNAKES (322). Harmless snakes (324). Constrictors (326).
Poisonous snakes (326). CROCODILES AND ALLIGATORS
(331). The economic importance of reptiles (332).

CHAPTER XXXIV

THE STRUCTURE AND ACTIVITIES OF BIRDS . : : » 335

The body built for flight (335). The wings as organs of
flight (335). Steering the body during flight (339). How
the feet are used (339). How the beak is used (343). Birds
are warm-blooded animals (345). Feathers (346). Molting
(347). Internal organs (348). Bird songs and call notes
(349). Bird migration (350). Mating (354). Nest building

xiv

TABLE OF CONTENTS

(354). Precocial and altricial birds (357). Birds’ eggs (358).
Incubation (358). Growth of the young (359).

CHAPTER XXXV

SOME COMMON BIRDS OF NORTH AMERICA

Ancient birds (361). Flightless birds (363). Water birds
(364). Land birds (369).

CHAPTER XXXVI

THE RELATIONS OF BIRDS TO MAN .

Commercial value (376). The value of birds as destroyers
of injurious animals (377). Domesticated birds (380).

CHAPTER XXXVII

BIRD PROTECTION

I. THE DESTRUCTION OF BIRDS (383). The destruction of
birds by man (383). Cats (387). Squirrels (388). Rats and
mice (388). Hawks (388). Owls (388). Crows and jays (388).
The English sparrow (389). Snakes (389). 2. THE PROTEC-
TION OF BIRDS (390). Protection from natural enemies
(390). Protection from man (390). 3. METHODS OF
ATTRACTING BIRDS (391). Bird houses (393).

CHAPTER XXXVIII

THE STRUCTURE AND ACTIVITIES OF MAMMALS

Habitats (398). Protection (399). Hair (400). Color
(400). Claws, nails, hoofs, and horns (401). Locomotion
(402). Internal organs (402). Digestion (403). Teeth
(404). Circulation (406). Respiration (406). Excretion
(407). Nervous system (407). Sense organs (408). ‘The
skeleton (410). Reproduction (410). Animal tracks (410).
Hibernation (413). Migration (414). Geographical distri-
bution (416).

CHAPTER XXXIX

THE ORDERS OF MAMMALS

Egg-laying mammals (419). Pouched mammals (420).
Invectivores (421). Bats (422). Flesh-eating mammals

PAGE

361

376

382

398

419

TABLE OF CONTENTS

(423). Gnawing mammals (430). Toothless mammals
(434). Even-toed hoofed mammals (435). Odd-toed hoofed
mammals (441). Elephants (442). Whales (442). Primates
(443).

CHAPTER XL

THE RELATIONS OF MAMMALS TO MAN

Domesticated mammals (450). Game mammals (451).
Predaceous mammals (453). Fur-bearing animals (455).
Gnawing mammals (458). Introduction of foreign mammals

(459).
CHAPTER XLI

THE PROTECTION AND PROPAGATION OF WILD LIFE

The need of protection (461). Protective measures (464).
The propagation of wild life (465).

CHAPTER XLII

THE CONSERVATION OF OUR NATURAL RESOURCES .

CHAPTER XLIII

THE PROGRESS OF ZOOLOGY

INDEX .

XV

PAGE

450

461

469

PRACTICAL ZOOLOGY

CHAPTER I

WHERE ANIMALS LIVE

Ir we compare the structures of our bodies, the food we eat,
the way we move from place to place, and our various other
activities with those of the apes, such as the gorilla, chimpanzee,
and orang-utan, we become aware of many similarities. If we
continue the comparison with other animals, for example, cattle,
sheep, horses, dogs, cats, etc., we realize that they possess struc-
tures and carry on activities which resemble in a general way
those of the apes and man. Likewise the birds, snakes, turtles,
frogs, and fish have many peculiarities in common with other
animals and with us.

Besides these animals, every one is more or less familiar with
many of what we call the ‘“ lower animals,” especially insects,
snails, oysters, earthworms, starfishes, tapeworms, and jellyfishes.
All of these animals must be able to live amid their surroundings ;
that is, in their natural habitat, and to reproduce others to con-
tinue the race after they are dead so that their kind may not
disappear entirely from the earth. In order to live, human be-
ings, as well as all the other animals, need certain things. The
most important needs for the maintenance of life are food,
water, air (oxygen), protection, and an opportunity to repro-
duce. These needs are satisfied by different kinds of animals
in different ways, and the variety of structures employed for
satislying these needs and the methods used seems almost infinite.

We are accustomed to think of other animals as living on land
B I

2 PRACTICAL ZOOLOGY

the way we do, and it is true that most of those we encounter
in our daily lives are terrestrial in habit; but we should remem-
ber that human beings, miners, for instance, may live under-
ground for long periods of time, or may remain in the water for
hours without injury, or may even move through space in a
balloon or aéroplane. These departures from activities on the
earth’s surface are, however, only temporary, and man’s habitat
is to be considered purely terrestrial.

Human beings share their ¢errestrial habitat with most four-
footed beasts, with the frogs and toads part of the time, and
with a host of the lower animals, such as insects, spiders, and
certain snails and worms. Fortunately, land animals do not all
try to live in the same sort of habitat, but are distributed over
the entire earth’s surface. Some seem to prefer the cold polar
regions, others temperate or tropic zones; some inhabit the
open plains, others live on forested mountains; and even the
height above sea level has an influence upon the kind of animals
inhabiting any particular area. Animals that live on the sur-
face are better known than those that live in the ground, since
the latter are less often seen. Among these ground inhabitants
or subterrestrial animals are the earthworm, and many other
worms, certain insects, crayfishes, and spiders, some of the
snakes, a few birds like the burrowing owl, and a number of
quadrupeds, of which the pocket gopher, mole, woodchuck, and
prairie dog are common examples. Almost all of these animals
must come to the surface from time to time to get food and for
other purposes, but their true homes are in the ground.

The animals of another group spend a part of their time flying
about in the air; to these the name aérial has been applied. The
most notable aérial animals are the birds, flies, butterflies, and
other insects, but there are a few flying quadrupeds, the bats,
and a few animals like the flying squirrels, flying lizards, and
flying fish, which do not really fly but only spread out the mem-
branes with which they are provided and sail through the air for
comparatively short distances.

WHERE ANIMALS LIVE 3

If animals were entirely restricted to the land for their homes,
only a comparatively small part of the world would be inhabited,
since about three fourths of our globe is covered with water.
Most of this is sea water, which contains about three and one
half per cent of salt, whereas a comparatively small area is cov-
ered by the fresh water in lakes, ponds, and streams. A study of
the animals that live in sea water and in fresh water soon reveals
the fact that, with few exceptions, those accustomed to salt
water perish almost at once if transferred to fresh water, and
vice versa, those living normally in fresh water die very quickly
if placed in the sea. Thus are the habitats of animals strictly
limited. Some of the common animals that live in the sea are
whales, sea turtles, many fish, a host of crabs, lobsters, and
similar forms, cuttlefishes, oysters, many clams and_ snails,
some worms, the starfish and its near relatives, the jellyfishes,
corals, sponges, and thousands of different kinds of minute
animals that can be seen clearly only with the aid of the micro-
scope.

Since most of us do not live on the seacoast, we are naturally
more familiar with the animals that live in fresh water. Fish,
crayfish, aquatic insects, the young of the mosquito, and the tad-
poles of frogs and toads are abundant fresh-water forms. They
do not, however, occur everywhere, but each kind of animal is
restricted to a rather definite habitat. For example, some fish
live in only the deepest parts of lakes, others prefer slow-flowing
streams, and many select the rapid waters of rivers and brooks.
Similarly, with other fresh-water inhabitants, each has its own
sort of habitat from which it very seldom strays.

This might seem to complete the list of available habitats for
animals, but there is one mode of existence that from the stand-
point of human welfare is probably more important for us to
know about than any other. This is the parasitic existence led
by thousands of forms, like the tapeworm, liver fluke, hookworm,
and trichina, and that vast army of invisible foes called germs
which are responsible for such diseases as malaria and yellow

4 PRACTICAL ZOOLOGY

fever in man and Texas fever in cattle. These internal parasites
live within the bodies of the particular animals upon which they
prey, and must be adapted to the conditions there; for example,
the tapeworm and the hookworm amid the digestive juices in
the alimentary canal of man, and the malarial parasite in the
blood of man. Other parasites are said to be external, since they
do not penetrate into the body, but simply ride about on their
victim. Human beings are sometimes infested with external as
well as internal parasites; we need only mention the louse and
the flea. Even parasites are sometimes attacked by other
parasites, thus establishing the truth’of the following lines: —
“Great fleas have little fleas
Upon their backs to bite ’em,

And little fleas have lesser fleas,
And so ad infinitum.”

The relations between animals and their surroundings are
often very complex. Living creatures must not only be able to
cope with the state of temperature, moisture, and other physical
conditions of their habitats, but must also maintain more or less
complex relations with plants, other animals of the same kind,
and animals different from themselves. There is always a
struggle for existence among the lower animals, just as there is
among human beings who work so strenuously for homes and
power. In this struggle for existence the weak usually succumb
and as a result the strength of the race is maintained. One
curious fact is that other animals may depend upon, as well as
struggle with, one another. This may best be illustrated by
Charles Darwin’s story of the field mice and humble bees.
Darwin found ‘that the visits of bees are necessary for the
fertilization of some kinds of clover; for instance, twenty
heads of Dutch clover yielded 2290 seeds, but twenty
other heads, protected from bees, produced not one.” .. .
“Humble bees alone visit the red clover, as other bees cannot
reach the nectar,— hence we may infer as highly probable,
that, if the whole genus of humble bees became extinct or very

WHERE ANIMALS LIVE 5

rare in England, the heart’s-ease and red clover would become
very rare, or wholly disappear. The number of humble bees in
any district depends in a great measure upon the number of
field mice, which destroy their combs and nests.... Now
the number of mice is largely dependent, as every one knows,
on the number of cats. ... Hence it is quite creditable that
the presence of a feline animal in large numbers in a certain
district might determine, through the intervention first of mice
and then of bees, the frequency of certain flowers in that dis-
trict!” The influence of old maids upon the number of cats
was suggested by Huxley as an addition to Darwin’s illustration.

Not all of the kinds of animals that exist at the present time
have been studied and named. There are many forms in every
locality that have thus far escaped the scientist, and there are
vast regions of the earth’s surface, both land and water, that are
yet to be examined. Nevertheless at least five hundred thousand
different kinds of animals have been described. It is obvious that
we can learn about only a few of this vast number. Fortunately,
it is possible to group these animals into large assemblages be-
cause of certain common characteristics; and these assemblages
can be subdivided into smaller groups. For example, all animals
with a long axis, like the human backbone, are placed in one
group, the vertebrates. One of the subdivisions of the back-
boned animals contains about eight thousand different kinds of
animals which possess hair and are called mammals; the mam-
mals may again be divided into smaller groups, one of which in-
cludes man.

In this way order has been introduced into what would other-
wise be a very chaotic mass of isolated items of knowledge, and
by selecting a few members from each assemblage or subdi-
vision we can get a very good general idea of the entire animal
kingdom. ‘This is what we propose to do in the following chap-
ters, and our selection will include those animals that we are most
likely to meet on our way to and from school or on our trips into
the country, and those that are of particular importance to man

6 PRACTICAL ZOOLOGY

either because of their use in industries or of their less direct
beneficial or injurious qualities. Furthermore, by directing our
attention to certain aspects of the life histories and activities
of these animals we shall obtain a general knowledge of the laws
and principles involved in the study of animals, the study known
as Zoology. Throughout our study, however, we should not
lose sight of the fact that we ourselves are animals, and that the
needs of the living creatures which we dominate are similar to
our own needs although the methods of satisfying them may be
very different. An animal must be adapted to the conditions
within its habitat or it cannot maintain itself. In our studies,
therefore, we must learn how the animal is adapted to its particu-
lar set of conditions before we can solve the problems involved.

Finally, there is one phase of animal study that has only re-
cently been emphasized, and that is the relation of animals to
the community, state, and nation. This subject, which is rather
fully treated in this book, we may call “‘ Civic Zoology.”

It will be necessary in the following chapters to speak of
certain of the large assemblages of animals, and for this
reason a simplified classification is here appended. It is
not intended that the student should learn the following
classification, but he should use it as a convenient and
simple reference. It is often advisable to separate the
entire animal kingdom into two subkingdoms, the Inverte-
brates and the Vertebrates, because of the relative importance
of the latter. The Vertebrates possess a backbone; the Inver-
tebrates do not. These subkingdoms may then be divided into
eight groups called phyla. The phyla are arranged, from the
simplest to the more complex. The numbers refer to the num-
ber of known kinds of animals in each phylum.

SusBkincpom I. INvERTEBRATA. — Animals without backbones.
518,400.
Phylum 1. Protozoa. — Minute, single-celled, or colonial
animals. 8500.

WHERE ANIMALS LIVE 7

Phylum 2. Porifera.— SPONGES. 2500.

Phylum 3. Coelenterata. — JELLYFISHES, Potyps, and
CORALS. 4300.

Phylum 4. Platyhelminthes. —TAPEworms, FLUKES. 4600.

Phylum 5. Nemathelminthes. —THREADWORMS. 1500.

Phylum 6. Annelida. —SEGMENTED WoRMS. 4000.

Phylum 7. Echinodermata.— STARFISHES, SEA URCHINS.

3000.
Phylum 8. Mollusca. — Cams, SNAILS. 60,000.
Phylum g. Arthropoda. — Crass, INSEcTS, SPIDERS.
400,000.
SUBKINGDoM II. VERTEBRATA.— Animals with backbones.
30,000.

Phylum ro. Vertebrata. — FisHrs, AMPHIBIANS, REPTILES,
Birps, MAMMALS. 30,000.

REFERENCES

Cyclopedia of American Agriculture. Edited by L. H. Bailey. — The
Macmillan Co., N. Y. City. Vol. III. Animals.

Cambridge Natural History. Edited by S. F. Harmer and A. E. Shipley.
— The Macmillan Co., N. Y. City. 10 volumes. -

College Zoology, by R. W. Hegner. — The Macmillan Co., N. Y. City.

American Natural History, by W. T. Hornaday. — Charles Scribner’s Sons,
N. Y. City.

Nature Study and Life, by C. F. Hodge. — Ginn and Co., Boston, Mass.

Practical Zoology, by Marshall and Hurst. — G. P. Putnam’s Sons, N. Y.
City.

Textbook of Zoology, by Parker and Haswell. — The Macmillan Co., N. Y.
City. 2 volumes.

Outlines of Zoology, by J. A. Thomson. — D. Appleton and Co., N. Y. City.

CHAPTER II
THE GRASSHOPPER

Tue Hasits, PHystotocy, ANATOMY, AND ECONOMIC
RELATIONS OF A TypicaL INSECT

Asout four fifths of the five hundred thousand different kinds
of animals known to man belong to a single group which we call
insects. Not only are insects numerous, so far as the number of
kinds is concerned, but there is an abundance of individuals of
each kind. This abundance makes it possible for us to collect
them without difficulty, and hence it is easy to obtain material
for our studies. Besides this, many insects, such as butterflies
and beetles, are very beautiful; they are also wonderfully adapted
to their various habitats, and when collected and properly ar-
ranged in a cabinet make one of the most interesting and instruc-
tive exhibits of natural objects that it is possible to possess.
Furthermore, certain insects, like the honeybee and silkworm, are
of great commercial value ; the gipsy moth, potato beetle, chinch
bug, army worm, and thousands of others must be continually
fought to prevent the destruction of our crops; and certain kinds,
the house fly and mosquito, for instance, are the principal
cause of the transmission of diseases like typhoid fever,
malarial fever, and yellow fever.

When we have learned the general structure and functions of
the parts of an insect, it is an easy task to distinguish these ani-
mals from all others; and sucha study lays the foundation which
will help us to understand the activities of other kinds of insects
and the structures concerned with these activities. In selecting

an insect for this first study we should try to find one large enough
8

THE GRASSHOPPER 9

to be examined easily, at least with a pocket lens, and one that
is comparatively simple in structure. For this reason we shall
use the grasshopper for our preliminary study. The grass-
hopper is one of the largest of our insects as well as one of the
simplest in structure. Grasshoppers are abundant during most
of the year and are therefore easily obtained for use in a
laboratory.

Grasshoppers or “‘lo-
custs’’ are common
everywhere in the fields
and meadows, jumping
out of the way of an
intruder or sometimes
flying up when ap-
proached. They may
be collected by a quick
grasp of the hand or
hundreds can be caught
in a short time in an
insect net. Methods
of locomotion can be
studied both in the field
and in the laboratory,
but the structure can
only be made out with a quiet, therefore, a dead specimen.
Insects can be killed painlessly by means of a cyanide bottle, and
preserved in 80 per cent alcohol. Grasshoppers resemble one
another in general structure, the different kinds differing only in
details, so the following account will apply to almost any of
them.

Locomotion. — Wincs. — Insects are the dominant animals at
the present time, so far as numbers are concerned — a fact that
is due to many causes. One of these causes is their ability to
move rapidly from place to place which enables them to find
food easily and to escape from their enemies. The locomotor

Fic. 1.— Carolina locust. (After Lugger.)

Io PRACTICAL ZOOLOGY

organs are the wings and legs. Some insects, like the bedbug and
the flea; are without wings and depend entirely upon their legs for
purposes of locomotion; whereas others, as the butterflies, make
flight their chief method of progression. The grasshopper uses
both wings and legs, but the latter are more effective during the
ordinary activities of daily life. Both wings and legs are at-
tached to the middle of the three principal parts of the body;
a part called the thorax (Fig. 1). The four wings are arranged
in two pairs fastened by movable joints at the sides near the
upper surface. The front pair are rather leathery in structure,
serving as a protection for the thin, membranous back wings,
which are folded beneath them when at rest. The thin wing
membranes are strengthened by minute tubes which are defi-
nitely arranged in every wing and are similar in number and
position in the individuals of every kind of insect but different
in the different kinds.

FLyInc. — The movements of the wings during flight are quite
interesting. The front edge of the wing is firm, whereas the mem-
brane as a whole inclines upward when the wing is lowered, and
downward when the wing is raised. This results in resistance
from behind, which propels the insect forward. The wings on
opposite sides of the body move up and down together, and the
faster they vibrate the more rapidly the insect progresses. The
house fly makes 330 strokes per second, the dragon fly 28, and
the cabbage butterfly 9.

Leos. — The six legs of the grasshopper are arranged in three
pairs; one pair is attached to each of the three parts or seg-
ments which make up the thorax. Other insects are likewise
provided with three pairs of legs. The legs are used by insects
chiefly for locomotion, but also for many other purposes, and an
examination of their structure will often enable us to determine
their functions (Fig. 2). Some are long and slender and fitted for
running (Fig. 2, 6); others are flattened out and bordered with
bristles, making them effective swimming organs (¢); some are
short and shovel-shaped for digging in the earth (d) ; a few enable

THE GRASSHOPPER TT

their possessors to grasp their food (a); and a number of kinds,
like the hind legs of the grasshopper (c), are longer and stronger
than the others and especially adapted for leaping.

Each leg is made flexible by a number of joints which divide
it into distinct segments. These segments have all been given
names which are important for two reasons: (1) they are often
descriptive of the part named, and (2) they enable us to talk
and write about the
various parts intelli-
gently. The segment
of the leg attached to
the body is called the
coxa; the next is the
trochanter; then fol-
lows the long slender
femur; then the tibia
with spines on its inner
surface; and finally the
tarsus. The tarsus
consists of three dis-
tinct segments, but the
one next to the tibia
zenlly aepreseris these ECG ae Ne ae anon be
that are fused together. a, grasping leg of praying-mantis; b, running
If the undersurface of _ leg of a beetle; c, leaping leg of a grasshopper :

‘ ‘ _ 4d, digging leg of mole-cricket; e, swimming leg
this segment is ex- Opi etle (After Sedgwick.)

amined, three pads

will be found, each belonging to one of the fused segments. There
are therefore five tarsal segments — the usual number in all in-
sects. The final tarsal segment bears a pair of curved claws which
make it possible for the grasshopper to cling to rough objects,
whereas the pads on the underside of the tarsal segments enable
the animal to walk on smooth surfaces. The pad belonging to
the last tarsal segment lics beneath the claws. Of particu-
lar interest are the two hind legs of the grasshopper, since these

PRACTICAL ZOOLOGY

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THE GRASSHOPPER 13

are used for leaping. They are built on the same plan as the
others, but the femur is very much enlarged, to accommodate the
muscles which are used when the animal jumps.

Food and Mouth Parts. — Grasshoppers feed on all sorts of
plants and possess a set of rather complicated mouth parts for
holding and grinding up pieces of vegetation. These mouth
parts are movably attached to the underside of the head. The
food is held by an almost rectangular flap, in front, and a bilobed
flap, behind, which are known as the upper lip or labrum (Fig. 3,
1b) and lower lip or labium (Fig. 3, Jab). Between these flaps
are two pairs of grinding organs, the true jaws or mandibles
(Fig. 3, md), which consist each of a single thick piece and are
grooved, and the auxiliary jaws or maxille (Fig. 3, mx) which
are made up of several pieces and serve principally to hold the
food between the mandibles. Both the labium and maxille
bear short, jointed filaments which are supplied with organs of
taste, touch, or smell. By means of these organs the insect is
able to choose between the available food material. Biting
mouth parts, such as those of the grasshopper, are the simplest
sort found among insects.

Digestion. — While the food is being masticated by the jaws,
it is mixed with a secretion (saliva) produced by a pair of sali-
vary glands (Fig. 3, s.gl); this secretion passes out through a
salivary duct (Fig. 3, s.d). The saliva acts upon the starch in
the food, changing it into a more digestible substance called
glucose — a change very similar to that which takes place in
our own digestive process. The masticated food mixed with
saliva then enters the alimentary canal. This is really a tube
which runs through the body and is separated into several well-

‘marked regions by constrictions.

First, the food passes through a small tube, the cesophagus
(Fig. 3, @), into a large thin-walled portion, the crop (Fig. 3, cr) ;
here the saliva continues its action upon the starchy materials
in the food. In most insects the crop is followed by a thick
grinding organ lined with teethlike projections, but this is ab-

14 PRACTICAL ZOOLOGY

sent in the common Carolina locust. Next, the partially digested
food enters the stomach or ventriculus (Fig. 3, vet), where it is
acted upon by juices secreted by six spindle-shaped pouches
(Fig. 3, gas.c) which open into the anterior end of the stomach.
From the stomach food passes into the intestine (not all of this
is shown in Fig. 3), the final portion of which is known as the
rectum (Fig. 3, rect). The digested food is absorbed by the
walls of the alimentary canal
and the undigested material
passes out of the body
through the anal opening
(Fig. 3, a7).
Circulation.— The di-
gested food absorbed by
the intestinal wall enters
the blood which fills the
body cavity, and is car-
ried in the blood stream
to all parts of the body,
where it is assimilated ; that
is, is changed into living
matter to take the place of
that which is continually,
being used up by the activi-
ties of the animal. The
Fic. 4.— Diagram of an insect show- blood is a fluid containing
ing the heart (4), aorta (a), and direction corpuscles. These corpus-
of the blood-flow (by arrows). (After 5 C
Kolbe.) cles are not reddish in color,
as in human beings, but are
usually colorless. The fluid of the blood is also generally color-
less, but it is sometimes yellowish or greenish. It has just

recently been discovered that the sex of many young insects
(caterpillars) can be determined by the color of the blood, that
of the males being yellow, and that of the females green.

The circulatory system of the insect is very simple and there

THE GRASSHOPPER 15

is no complex arrangement of tubes, asin human beings. Near
the upper part of the body is a rather long contractile tube
called the heart (Fig. 3, #t), into which the blood surrounding it
flows through pairs of openings. By contractions, the blood is
forced forward out of the heart and into the spaces of the body in
which the various internal organs lie. All of these organs are
in this way continually bathed with a fresh supply of blood, as
illustrated by the arrows in Figure 4.

Functions oF BLroop.—In man the blood carries food
material, waste substances, and oxygen from one part of the
body to another, but in insects there is a complex system of
tubules, known as trachez, which carry oxygen directly from the
outside to the various parts of the body and so the blood is
relieved of this duty.

Respiration. — We are accustomed to think of breathing as
taking place through the nose or mouth, but in insects airis
taken in through pores, called spiracles, or stigmata, which occur
at intervals on the sides of the body. The grasshopper is pro-
vided with ten pairs of these breathing pores; two in the thorax
and eight in the abdomen. Connected with these openings are
the tubes within the body which branch many times, becoming
very minute. The taking in and forcing out of air, a process
known as respiration, is brought about by regular expansions
and contractions of the abdomen. In certain grasshoppers
there had been found to be from thirty-four to ninety-two
respiratory movements per minute. Such a system as that
just described is in the grasshopper and many other insects
assisted by rows of air sacs; thus an abundant supply of oxygen
is assured at all times, a fact that in part accounts for the re-
markably rapid growth of these animals.

Excretion. — Waste matters in solution that result from the
breaking down of the living matter during the activities of the
insect are collected by a group of long thin tubes which are coiled
about in the body cavity (Fig. 3) and enter the forward end of
the intestine. These tubes, of which there may be as many as

16 PRACTICAL ZOOLOGY

one hundred and fifty in the grasshopper, perform functions
similar to those of the kidneys of other animals. They are
known as Malpighian tubes, being named after the Italian
naturalist, Malpighi (1628-1694).

In the preceding paragraphs we have described many of the
processes that take place within the body of an insect. This
study of function is known as physiology. We have also dis-
cussed the organs concerned with these processes; the study of
structure constitutes the science of morphology. There are still,
however, several systems of organs which perform functions
necessary for the insect to cope successfully with its surround-
ings. These are concerned with protection (exoskeleton), the
reception and transmission of stimuli (sense organs and nervous
system), and the continuity of the race (reproductive system).

Protection. — The outside covering of the grasshopper and
other insects, the exoskeleton, is known as the cuticula and con-
sists of a substance called chitin. Chitin protects the insect
from mechanical injury as well as from contact with water and
other liquids. It is formed by the part of the living matter just
beneath it. This chitinous covering may be assisted by hairs,
scales, and spines which, however, may serve other purposes
as well as that of defense. Frequently the exoskeleton is colored
in such a way as to conceal the insect amid its surroundings; this
is known as protective coloration. For example, a green katydid
is difficult to see when resting on a green leaf. As a further
means of protection some insects possess glands which produce
evil-smelling or distasteful substances sufficient to prevent at-
tacks from dangerous birds and lizards.

Sensations. — Insects, like human beings, receive impressions
from the outside world by means of special structures called
sense organs. We may distinguish organs of sight, touch, smell,
taste, and hearing. These organs are scattered about on various
parts of the body and connected with the central nervous system,
but the most important ones are borne by the head.

THE GRASSHOPPER 17

The visual organs comprise two compound eyes (Fig. 1) and
three simple eyes or ocelli. The compound eyes are built up of
hundreds of similar parts, each of which forms a portion of an
image and thus all together they produce a sort of mosaic. The
ocelli probably serve chiefly to distinguish light from darkness.

The organs of touch, taste, and smell are represented by various
forms of bristles which usually lie in minute cavities and are
connected with the nervous system. Tactile or touch bristles
and often olfactory or smelling organs are located on the
antennz, whereas those concerned with taste are, as might be
expected, distributed over the mouth parts.

The grasshopper has besides all these a pair of very interesting
auditory or hearing organs situated one on either side near the
forward end of the abdomen. They consist of a light membrane
so constructed as to vibrate, and receive and transmit sound
waves. These auditory organs enable the grasshoppers to
communicate with each other; thus the male Carolina locust
is often seen poising in the air with rapidly vibrating wings, and
making a crackling sound by rubbing the front and hind wings
together.

Nervous System. — The stimuli received by the sense organs
are carried to the central nervous system by means of nerves, and
impulses are sent out by the central nervous system in the same
way. The insect in this manner becomes aware of the conditions
of its surroundings, and the impulses sent out resultin appropriate
movements. The nervous system is essentially a double thread
united at intervals by a mass of nervous substance called a gan-
glion. The brain (Fig. 3, br) is the foremost mass of this sort.
From the brain one part of the double thread passes down on
either side of the cesophagus and unites below with another
ganglion (Fig. 3, soe. gl). Then follows a chain of eight gan-
glia lying near the lower part of the body in the median line.
Those in the thorax (Fig. 3, g. 2, g. 3) are the largest of these,
since they must control the wings and legs. The delicate
sympathetic nervous system (Fig. 3, asg, fg, /sg, psg, sgn) con-

c

18 PRACTICAL ZOOLOGY

trols the swallowing movements, regulates digestion and breath-
ing, and controls the salivary glands and circulation.
Reproduction. — Grasshoppers do not live very long and the
race must therefore be continued from year to year by the pro-
duction of new individuals. The processes involved are those
connected with the formation of eggs and the development of
the eggs and young until the adult stage is reached. The
eggs, or female germ cells, arise within the egg tubes of the
female insects. Before they are laid they are penetrated by the

———
TS eS

MSERRNILET Win nm

Fic. 5. — Rocky Mountain locusts laying eggs. (After Riley.)

male germ cells which arise in the reproductive organs of the
male (Fig. 3, tes); this union of male and female germ cells is
known as fertilization. During July and August these eggs
are formed into masses of from thirty to one hundred, covered
with a sort of jelly, and deposited in a hole in the ground about
an inch below the surface (Fig. 5). Here they remain through-
out the winter. The following spring the young emerge from
the egg in a form resembling their parents in many ways, but
differing from them in the size of the head and absence of wings
(Fig. 6). As the young grow, the exoskeleton becomes too tight
for them, so they shed it (molt) at intervals and acquire a new

THE GRASSHOPPER ime)

one. At each molt the shape of the body changes and the
wings, which soon appear, grow larger, until finally the adult
condition is reached (Fig. 6, 6). The changes that occur‘during
this period of growth constitute what we know as metamorpho-
sis, and the young in the case of the grasshopper is known asa
nymph.

Metamorphosis. — The development of the insect within the
egg, a study called embryology, is too complex to be considered
here, but we can discuss with profit the growth of the young

Fic. 6.—Six successive stages in the metamorphosis of a grasshopper.
(After Emerton.)

after they hatch and the changes that take place from this time
until the adult condition is reached.

A few wingless insects (A ptera) emerge from the egg in the
form of the adults and do not change much, except in size,
throughout life. Another larger group, of which the grass-
hopper is an excellent example (Fig. 6), hatch as nymphs, re-
sembling their parents in general form, but thereafter undergo
various changes until they have reached their full size. This is
direct metamorphosis, the term direct referring to the fact that
there are no interruptions due to resting periods, but the insects
are active throughout life. The majority of insects, however,

20 PRACTICAL ZOOLOGY

undergo indirect metamorphosis. They hatch from the eggs
as wormlike larve, grow in size for a time, and then enter a
stage of rest, when they are spoken of as pup. During the
pupal stage the adult insect develops within the pupal covering
and finally breaks out fully formed. The larve of butterflies
and moths are called caterpillars; those of beetles, grubs; and
those of flies, maggots. The pup of butterflies and moths are
popularly known as chrysalids. The chrysalis is often covered
by a cocoon spun by the larva.

Relations to Man. — Grasshoppers are valuable for the pur-
pose of studying structure and function. They are important
also because of the injuries they inflict upon crops in order to
satisfy their hunger. There are plenty of noxious weeds that
the grasshoppers might devour with benefit both to themselves
and to the farmer, but they persist in destroying many kinds
of useful plants instead.

The most notorious grasshoppers in this country are the
Rocky Mountain or migratory locusts. These insects were
particularly destructive in the states of the western part of the
Mississippi Valley in the years 1873 to 1876. Their native
breeding grounds are in the highlands of Montana, Wyoming,
and Colorado, but when the locusts become excessively abun-
dant, they spread eastward, flying with the wind, as much as
two hundred or three hundred miles in a single day. Their
ravages in the seventies were described by a commission of men
appointed by Congress to report upon them as follows: —

“ Falling upon a cornfield, the insects convert in a few hours
the green and promising acres into a desolate stretch of bare,
spindling stalks and stubs. ... Their flight may be likened
to an immense snow-storm, extending from the ground to a
height at which our visual organs perceive them only as minute,
darting scintillations, leaving the imagination to picture them
indefinite distances beyond. ... In alighting, they circle in
myriads about you, beating against everything animate or in-
animate, driving into open doors and windows, heaping about

THE GRASSHOPPER 20

your feet and around your buildings, their jaws constantly at
work, biting and testing all things in seeking what they can
devour.”

Since then Rocky Mountain locusts have appeared at inter-

Fic. 7.— Three grasshoppers injurious to vegetation.
A, Red-legged locust. (After Riley.)

B, Differential locust. (After Sanderson and Jackson.)
C, Southern lubber grasshopper. (After Sanderson.)

vals in destructive numbers in Minnesota, North Dakota, and
neighboring states, but have never been a real plague. Practi-
cally nothing can be done to prevent the injuries done by such
vast hordes of migrating insects.

Other grasshoppers, though not so notorious as the Rocky

22 PRACTICAL ZOOLOGY

Mountain locusts, are of considerable economic importance,
appearing in some localities every year in such abundance as to
become very destructive to crops. Of these may be mentioned
the red-legged locust of the eastern United States (Fig. 7, A),
the California devastating locust in California, the differential
locust of the Mississippi Valley (Fig. 7, B), the huge lubber

Fic. 8. — Two hopperdozers, tied together, at work. (After Lugger.)

grasshoppers of Florida and the Western plains (Fig. 7, C), and
the American acridium of the Southern States.

Several methods of controlling these non-migratory locusts
have been devised; fall plowing buries their eggs so that they
do not produce young; poison bran mash may be scattered in
the fields to kill both young and adults; and a contrivance
called a hopperdozer (Fig. 8) catches thousands of leaping in-
dividuals in its pans of kerosene as it is dragged over infested
fields.

THE GRASSHOPPER 23

REFERENCES

The Anatomy of the Carolina Locust, by R. E. Snodgrass. — Washington
Agricultural College, Pullman, Washington.

Elementary Studies in Insect Life, by S. J. Hunter. — Crane and Co.,
Topeka, Kansas.

College Zoology, by R. W. Hegner. — The Macmillan Co., N. Y. City.

CHAPTER III
SOME INSECT ADAPTATIONS

Our knowledge of the activities of the grasshopper and the
structure of this insect will enable us to understand the modi-
fications that serve to adapt other insects to their various modes
of life. The number of these adaptations is legion and we shall
therefore have to select a few of the most interesting ones that
can be observed in the laboratory.

Fic. 9.—A, a back-swimmer. Notice the oar-like hind legs. (After Weed.)

B, a mole-cricket with front legs fitted for digging. (After Barret.)

C, young of the Cicada with front legs fitted for digging. (After Marlatt
and Riley.)

Locomotion. — First, as regards locomotion, we may refer to
the insects that spend their lives in the water or underground.
Many aquatic insects are excellent swimmers, with legs specially
constructed for use as oars. This is true of the whirligig

24

SOME INSECT ADAPTATIONS 25

beetles, diving beetles, and back swimmers (Fig. 9, A). Insects
like the mosquitoes (Fig. 53) and the water skaters, on the other
hand, remain on top of the water, where they are sustained upon
the surface film by their long slender legs, just as is a needle
which is carefully placed on top of the waterinatumbler. In-
sects that burrow in the ground possess legs fitted for digging; for
example, the mole-cricket (Fig. 9, B) and the young of the
cicada (Fig. 9, C). Many insects, like the
flea (Fig. 32), do not fly because they lack
wings, but others cannot fly even with wings,
either because these organs are too small
for the weight of the body (Fig. 26) or, as
is the case with some beetles that are found
under stones and logs, their wings have
grown together so that they cannot be
spread.

Respiration. — The breathing methods
or respiration of aquatic insects are often
very different from those of their relatives
living on land. Since these insects live
under the water, they must either come to
the surface for air (Fig. 55), or else get their
air from the water. Many of them, like
the young of the may flies (Fig. 10) and

Fic. 10. — Young of
may fly showing
damsel flies, possess filamentous or leaf-like tracheal gills (&).

projections called tracheal gills, by means i a ae

of which the air mixed with water is collected in the air tubes
and then carried throughout the body.

Securing Food. — Movutnu Parts. — Adaptations for the
purpose of getting food are especially important, since those
insects with biting mouth parts, like the grasshopper, can be
destroyed by spraying their food with a poison such as Paris
green; whereas those with piercing and sucking mouth parts
feed only on juices from within the plants or animals they at-
tack, and must be destroyed in some other way. The mouth

26 PRACTICAL ZOOLOGY

parts of the mosquito (Fig. 11, A) may serve as an example of
the sucking mouth parts. The upper and lower lips form a
tube in which the long, sharp mandibles and maxilla move
when a puncture is made. The juices are drawn into the ali-
mentary canal by the suction
caused by a muscular enlargement
of the cesophagus. In some suck-
ing insects there is a special
reservoir, called a sucking stomach

. B
Fic. 11.— A, mouth parts of a mosquito.

H, hypopharynx; Lod, lower lip; Ldér, upper lip; Md, mandible; Mx, maxilla.
(After Becker.)

B, internal anatomy of a moth showing the proboscis (Mx) and sucking
stomach (V’). (After Newport.)

(Fig. 11, B, V’), in which juices are stored until needed. The
sucking apparatus of the butterflies and moths differs from that
of the mosquito. Here the maxille are very long, forming a
tubelike proboscis (Fig. 11, B, Mx) which is coiled beneath
when not in use, and the jaws are extremely small or
entirely absent.

SOME INSECT ADAPTATIONS 27

Fic. 12. — Legs of the worker honey-bee. (After Cheshire.)

Lrcs. — Among the most interesting of all adaptations for
food-getting are those exhibited by the legs of the worker honey-
bee. These are shown in Figure 12 and may be described

28 PRACTICAL ZOOLOGY

briefly as follows: The first pair of legs (Fig. 12, C) possess
the following useful structures. The femur and the tibia
({i) are clothed with branched hairs for gathering pollen. From
the distal end of the tibia of one of these is the pollen brush (b
in C and E), the curved bristles of which are used to brush up
the pollen loosened by the coarser spines; on the other side is
a flattened movable spine, the velum (v in C and E), which fits
over a curved indentation in the first tarsal joint or metatarsus
(p in C). This entire structure is called the antenna cleaner,
and the row of teeth (F) which lines the indentation is known as
the antennacomb. Figure H shows in sections how the antenna
(a) is cleaned by being pulled between the teeth (c) on the meta-
tarsus (/) and the edge (s) of the velum (v). On the front of
the metatarsus is a row of spines (cb in C), called the eye brush,
which is used to brush out any pollen or foreign particles lodged
among the hairs on the compound eyes.

The middle legs (Fig. 12, D) are provided with a pollen brush
(b), but, instead of an antenna cleaner, a spur (s) is present at
the distal end of the tibia. This spur is used to pry the pollen
out of the pollen baskets on the third pair of legs and to clean
the wings.

The last pair of legs (Fig. 12, A and B) possess three very
remarkable structures, the pollen basket, the wax pinchers
(wp in B), and the pollen combs (at p in B). The pollen basket
consists of a concavity in the outer surface of the tibia with rows
of curved bristles along the edges (ti in A). By storing pollen
in this basketlike structure, it is possible for the bee to spend
more time in the field, and to carry a larger load each trip. The
pollen basket in cross section is shown in Figure 12, G. The
pollen combs (at p in B) serve to fill the pollen baskets by
combing out the pollen which has become entangled in the
hairs of the thorax, and transferring it to the concavity in the
tibia of the opposite leg. At the distal end of the tibia is a row
of wide spines; these are opposed by a smooth plate on the prox-
imal end of the metatarsus. The term wax pinchers (wp in B)

SOME INSECT ADAPTATIONS 29

has been applied to these structures, since they are used to re-
move the wax plates from the abdomen of the worker. All of
these structures can easily be observed in the laboratory with the
aid of a microscope.

Fic. 13.— A, Kallima, the leaf-butterfly, flying; a, at rest.
B, Siderone, another leaf-butterfly, flying; 6, at rest. (From Davenport.)

Coloration. — Finally, insects, as well as many other animals,
are often adapted to their surroundings by their colors. Colors
are very highly developed among insects, and while some do not
seem to be of any particular use to their possessors, it is easy to
determine the distinct value of others. Many insects, both

30 PRACTICAL ZOOLOGY

adults and young, in general resemble their surroundings. Thus
the green caterpillar of the cabbage butterfly (Fig. 20) is very
difficult to see against the green of the leaves and no doubt es-
capes from many of its enemies because
of its general protective resemblance.

One of the most famous of all but-
terflies is the Kallima (Fig. 13) which
is found in India. When at rest this
insect clings to the side of a twig with
its wings held together over its back.
In this position it resembles a dead leaf
and is no doubt overlooked by its
enemies, the birds and lizards. Any
animal that looks like some special ob-
ject, as in this case, is said to possess
special protective resemblance. An in-
teresting insect of this sort that is often
abundant in this country is the walk-
ing stick (Fig. 14), which is long and
slender and colored like the bark of a
tree. When it clings to a twig and
extends its front legs in a line with its
body, it is effectively concealed from its
enemies by its special resemblance to
the twig.
meee pee ee Certain other animals are very

brightly colored and are, therefore, quite

conspicuous amid their surroundings. It has been found,
however, that such animals are often distasteful to their nat-
ural enemies, and, being conspicuous, are readily recognized,
and thus the animals that might otherwise prey upon them are
warned of their inedible qualities. The potato beetle, the lady-
bird beetle, and the hornet are all supposed to be warningly
colored.

The term protective mimicry has been applied to cases such

SOME INSECT ADAPTATIONS 31

as that of the relation between the milkweed butterfly and its
near relative the viceroy butterfly. The milkweed butterfly
seems to be inedible to birds and is warningly colored. Its
cousin, the viceroy, which is eaten by birds, resembles the
milkweed butterfly so closely that one must examine the two
with care to distinguish one from the other. The viceroy is
supposed to mimic its larger relative and thus escape by being
mistaken for its inedible model.

Sometimes the colors of an animal are not only protective but
aggressive, since they effectively conceal their owner while it is
creeping upon its prey. A green snake among green leaves can
thus get close to its victim without being seen. No sure cases of
aggressive coloration are known among insects.

REFERENCES

Entomology, by J. W. Folsom. — P. Blakiston’s Son and Co., Philadelphia.
Textbook of Entomology, by A. S. Packard. — The Macmillan Co., N. Y.
City.

CHAPTER IV
INSECTS INJURIOUS TO VEGETATION

Extent of Injury. — People who live in towns and cities oc-
casionally hear of the destruction to crops caused by such in-
sects as the army worm and chinch bug, and notice the fact that
the leaves of trees are sometimes eaten away by beetles and cater-
pillars. Most of them do not realize, however, that every kind
of crop raised by the farmer, every kind of fruit tree cultivated
by the fruit grower, and every sort of forest and shade tree is
constantly being attacked by destructive insects and their value
considerably lessened on this account. We suffer financially
because the smaller crops cause higher prices, and when we learn
that about 10 per cent of every crop is destroyed by insects, we
can estimate in a general way how much we spend annually in
feeding these voracious creatures. The average annual damage
done by insects to crops in the United States was conservatively
estimated by Walsh and Rilev to be $ 300,000,000 — or about
$50 for each farm. A recent estimate by experts puts the
yearly loss from forest insect depredations at not less than
$ 100,000,000. The common schools of the country cost in 1902
the sum of $235,000,000, and all higher institutions of learning
cost less than $ 50,000,000, making the total cost of education
in the United States considerably less than the farmers’ loss from
insect ravages. It costs the American farmer more to feed his
insect foes than it does to educate his children.

Furthermore, the yearly losses from insect ravages aggregate
nearly twice as much as it costs to maintain our army and navy,
more than twice the loss by fire, twice the capital invested a

32

INSECTS INJURIOUS TO VEGETATION

manufacturing agricul-
tural implements, and
nearly three times the
estimated value of the
products of all the fruit
orchards, vineyards, and
small fruit farms in the
country.!

Even after the crops are harvested they are still
open to the attack of meal worms and other insects
that feed on stored grain and manufactured food-
stuffs.

There are many thousands of insects that de-
serve to be mentioned, but our space is limited
and we must therefore refer to only a few that
affect us most directly. Each sort of plant is in-
fested with many kinds of insects, but usually only
a few of these are very destructive. Thus corn is
attacked by about two hundred different insect
enemies, clover by a iike number, apple trees and

Fic. 16.—The chinch bug: A, adult; B, nymph;

Fic. 15.— A, moth of
the army worm.
B, the army worm.
(After Riley.)

apples by four

hundred, and oak
\\ trees by probably
a thousand.
Army Worm.
Cc D

—wWe often read
in the daily

C, eggs (enlarged); D, beak through which the bug

sucks its food. (After Riley.) papers or in gov-

1Folsom, J. W., Entomology with reference to its biological and economic as-

pects.
D

34 PRACTICAL ZOOLOGY

F } G

Fic. 17.—Chinch bugs on
a corn plant. (Photo — by
O'Kane.)

ernment bulletins of the insects that
are destructive to field crops, such
as the army worm and the chinch
bug. The army worm (Fig. 15, B)
is a black and yellow striped cater-
pillar about one and one half or two
inches long when full-grown. It is
the larval stage (caterpillar) of an in-
conspicuous dull-brown moth (Fig.
15, A). These caterpillars may
occur anywhere east of the Rocky
Mountains and sometimes become
so abundant that they must migrate
in search of food. At such times
they crawl along in vast armies
feeding, usually at night, upon the
leaves and stalks of grains and
grasses, the heads of which they
generally cut off. The crops over
large areas are in this way totally
destroyed, with a tremendous loss to
the farmer and indirectly to the
final purchaser of the food manu-
factured from grain.

Metuops oF ContTROL. — Fortu-
nately army worms are killed in
enormous numbers by their natural
enemies or they would soon make
the world uninhabitable. The ta-
china flies (Fig. 47, B) are their
worst enemies. These little insects
lay their eggs on the body of the
army worm (Fig. 47, C) and the
maggots which hatch from these

eggs burrow into the worm and finally kill it.

INSECTS INJURIOUS TO VEGETATION 35

The most effective method of protecting a field from invasion
is to plow a deep furrow with steep sides around it and then pul-
verize the soil in the furrow so that the worms cannot climb out.
As a result they collect in the bottom, where they can be crushed
or killed by a dose of kerosene.

Chinch Bug. — Another important enemy of field crops is the
chinch bug (Figs. 16 and 17), an insect about one fifth of an inch
long, with a black body and white wings folded over the back.
This insect has been principally injurious to small grains and corn
in the Central and North Central States, the total damage during
the years 1850 to 1909 being estimated at $350,000,000. The
bugs travel from field to field on foot, although they possess wings,
and like the army worm may be stopped in their march by a
steep furrow plowed in their path. A narrow strip of coal tar
is also an effective barrier to their progress.

Other Insects Injuring Field Crops. — Other notorious pests
of field crops are the grasshoppers (see Chap. II); the cut-
worms (Fig. 18, A), which have a habit of gnawing off the stems of
‘»plants just at the surface of the ground; the Hessian fly (Fig.
18, B), which attacks the stalks of wheat and causes an average
loss of about 10 per cent each year; the green bug (Fig. 18, C),
a plant louse which sucks the juices of oats, wheat, barley, and
corn, stunting or killing the plants; the corn-ear worm (Fig.
18, D), which eats into the ears of corn, destroying from 2 to
3 per cent of the crop annually with an estimated cash value
of from thirty to fifty million dollars; the alfalfa weevil (Fig.
18, E) in the West; and the cotton boll weevil (Fig. 18, F) of
the South, which damages cotton every year to the extent of
about twenty million dollars.

Insects Injuring Garden Vegetables. — Potato BEETLE. —
We are perhaps more familiar with insects that injure garden
vegetables, such as the potato beetle and cabbage butterfly, than
with those that destroy field crops. The potato beetle (Fig. 19)
was, up to the year 1885, a harmless insect, living in the Colorado
region. It fed upon certain common weeds, but when the Irish

36 PRACTICAL ZOOLOGY

potato was introduced it transferred its activities from weeds
to cultivated potato plants. Since then it has spread all over

he 3

=r CEE:

Fic. 18.—Insects injurious to field crops: A, cutworm; B, Hessian fly ;
C, green bug or aphid (at the left) being parasitized by a minute wasp; D, cot-
ton bollworm or corn-ear worm; E, alfalfa weevil; F,

cotton boll weevil.
(After various authors.)

this country and has become a pest that must be fought con-
stantly. There are two broods of beetles per year in most parts

INSECTS INJURIOUS TO VEGETATION 37

of the United States. The yellow eggs are laid in groups of
twenty to seventy-five on the undersurface of potato leaves.

Fic. 19.— Potato beetle. Adult and young on plant, and adult enlarged.
(Photo by O'Kane.)

The larvee which hatch from the eggs feed on the leaves until
they are full-grown, then they burrow into the ground, change into

38 PRACTICAL ZOOLOGY

pup, and finally emerge as adults. Paris green, an arsenical
preparation, has proved to be a practical and effective
remedy, for when sprinkled on the potato plants this poison
is taken into the beetle’s stomach with the leaves and quickly
kills it.

CaBpaceE Worm. — The cabbage worm (Fig. 20, C) is the
caterpillar of the cabbage butterfly. It is not indigenous to this
country but was unintentionally introduced from Europe about
1860, when it first
appeared near
Quebec, Canada.
By 1868 it had
reached the Gulf
States; since then it
has made its way all
over the country.
The cabbage butter-
fly (Fig. 20, A) is
white with black
near the tip of the
fore wings, and is
about two inches
across when the
wings are expanded.

Fic. 20.— Cabbage butterfly: A, adult; B, eggs; The larve (Fig. 20,
C, larva; D, pupa or chrysalis.

C) are velvety green
in color and resemble the foliage so closely as to be hardly
distinguishable from it. When full-grown they are about one
and one fourth inches long. Spraying or dusting with Paris

‘green will kill the larvae, but some people are afraid to do this
for fear of being poisoned when they eat the cabbage. This
fear, however, is unfounded, since one would have to eat twenty-
eight entire heads at one sitting to feel any poisonous effects
from the Paris green. Many cabbage worms are annually de-
stroyed by parasites, one of which, a Braconid fly, is especially

INSECTS INJURIOUS TO VEGETATION 39

interesting because it was imported from Europe in 1883 for
this very purpose and has ‘“‘ made good.”

Other Garden Pests. — Every sort of garden vegetable must
struggle against the ravages of its own particular set of insects.
Peas and beans are eaten into by the pea weevil (Fig. 21, A) and
bean weevil, which cause injuries in this country amounting to
several millions of dollars
each year; the striped cu-
cumber beetles (Fig. 21,
B) attack young cucum-
ber and melon plants; the
squash bugs (Fig. 21, C)
devour our squash vines;
and the celery caterpillar
(Fig. 21, D), the larva of
one of our most beautiful
swallow-tail butterflies,
eats the celery leaves be-
fore the stalks are ready
for the table.

Insects Injuring Fruits.
—San JosE SCALE. — Per-
haps the greatest struggle
of all against destructive ve
a Fic. 21.—Insects injurious to garden
insects must be made by vegetables: A, pea weevil; B, cucumber
the horticulturists, for no beetle; C, squash bug; D, celery caterpillar,

‘ the larva of the black swallow-tail butterfly.
other vegetation seems so (After various authors.)
liable to attack as the
fruit trees and the fruit they bear. The San José scale
insect (Fig. 22) is perhaps the most important of all fruit-
tree pests. It appeared in 1880 near San José, California, and
from there became distributed over the United States on young
trees. The adult female insect is only a fraction of an inch long
and lies underneath a small, grayish scale formed by concentric
circles and produced by a waxy secretion from the insect. Be-

4o PRACTICAL ZOOLOGY

cause of their small size and protective covering, these scale
insects often are not noticed until they become so numerous as
to be very destructive. Their powers of reproduction are re-
markable; it has been estimated that the progeny of a single

Fic, 22. — San José scales on bark of tree. Small circle above, natural size ;
small circle below, highly magnified. (Photo by O'Kane.)

female would number over three billion in a single season if all
were to survive. Scale insects possess very long, slender pierc-
ing mouth parts, which are inserted into the plant to suck out
the sap. Not only does the tree become weakened because
of the loss of sap, but it is also poisoned by a secretion injected

INSECTS INJURIOUS TO VEGETATION 41

into it by the scale insect. Two principal methods have been
devised to destroy scale insects. One method is to spray the
infested plants, during the winter when they are dormant, with
a strong solution of lime-sulphur mixture or kerosene oil; the
other is to cover the fruit trees one by one with a sort of tent,
and generate beneath this hydrocyanic acid gas, which quickly
kills the scale insects. Among other scale insects that are in-
jurious to fruit trees may be mentioned the oyster-shell scale
and scurfy scale.

Fic. 23. A stable made by ants for plant lice or aphids. (From Cornell
Leaflet.)

Piant Lice (Figs. 18, C, and 23).—Closely related to the
scale insects is another group of sucking insects, the aphids or
plant lice. The woolly apple aphis is a very destructive pest in
young apple orchards. It works mostly upon the roots and thus
often escapes notice until the trees are badly injured. The com-
mon apple aphis of Europe also attacks young apple trees, caus-
ing the leaves to curl up and drop off. Associated with the

42 PRACTICAL ZOOLOGY

aphids are always to be found ants which feed upon the drop
of ‘‘ honeydew ”’ secreted by the plant lice. The relations be-
tween various kinds of aphids and ants are often very complex.
Sometimes the ants cover the aphids with a protecting ‘‘ shed ”
of mud (Fig. 23), and it has been shown that the eggs of the corn-
root louse are collected by ants in the autumn and stored in their
underground nests, where they are cared for until spring when
the newly hatched aphids are carried to the roots of the corn.
This relationship, termed symbiosis, is mutually beneficial; the
aphids are pro-
tected by the ants,
and the ants are
repaid for their
trouble with hon-
eydew.

Copiinc Motu.
— There is one
fruit enemy with
which every one

Fic. 24.— Codling moth: a, adult; b, larvain js acquainted, the
apple; c, pupa or chrysalis. (From Farmers’ Bul. :
283, U. S. Dept. Agric.) codling moth,

which is respon-
sible for the ‘“‘wormy”’ apple (Fig. 24). The eggs of this moth are
laid near the apple blossoms, and when the larve hatch, they crawl
to the nearest young apple, into which they burrow. Most of the
injured fruit drops to the ground, and when trees are not sprayed
with poisonous mixtures, almost every apple is destroyed. The
annual loss in the United States due to this pest is about twelve
million dollars.

Insects Injuring Shade Trees. — A problem that has been
getting more and more serious within recent years is that of
protecting the shade trees of city streets and parks. It is now
absolutely necessary for the city forester, or those in charge of
parks, to be acquainted with the insect pests that feed upon the
leaves of trees and to know how to control them. This is es-

INSECTS INJURIOUS TO VEGETATION 43

pecially true in New England and other Eastern States, where
such injurious insects as the gypsy moth, brown-tail moth, and
elm-leaf beetle have recently overrun the country, killing most of
the trees in their path. In other parts of the country the tus-
sock-moth caterpillars, leopard-moth caterpillars, and thousands
of others are a continual menace to the shade trees, and they
must be fought consistently if we do not want our streets to be
shorn of their beautiful vegetation.

Fic. 25. — The white-marked tussock-moth: A, adult male; B, adult female
(wingless) ; C, caterpillar showing white tussocks on its back; D, pupe in
cocoons; E, adult females laying eggs on bark of tree.

Tussock Motu. — The white-spotted tussock moth is very
common in various parts of the country. The caterpillar (Fig.
25, C) isa little over an inch long, has a bright red head, and four
tufts of white bristles, the “ tussocks,” on its back. The adult
male (Fig. 25, A) is an inconspicuous, dull-colored moth with a
white spot near the margin of each wing. The adult female

44 PRACTICAL ZOOLOGY

(Fig. 25, B) has no wings and consequently does very little travel-
ing. She lays her eggs on the cocoon from which she emerges
(Fig. 25, E) and covers them with a protective coat of white
froth which soon becomes hard and brittle. These egg masses
are easily seen on the bark of trees and can be destroyed by
painting them with creosote. As a general rule, collecting and
destroying the eggs of insects is not a very effective way to con-
trol them, but in the case of the tussock moth, potato beetle, and
a few others, children can be of immense civic service if they
band together to fight these insects in this way. The caterpillars
may be poisoned by spray-
ing the infested trees with
Paris green, and can be
prevented from crawling
from one tree to another

ww? A B c

Fic. 26.— Gypsy moth: A, female; B, larva; C, pupa between leaves.
(After Howard.)

by banding trees near the base with a sticky substance like
tangle-foot.

Gypsy Motu.— The gypsy moth (Fig. 26) has been ex-
tremely injurious to shade trees in certain of the Eastern States.
It was introduced from Europe at Medford, Massachusetts, in
186g, but did not become really abundant until about twenty
years later. Within the past two decades millions of dollars
have been spent in an effort to check the spread of the moths and
destroy those specimens already present. The caterpillar (Fig.
26, B) is hairy, and about two inches long. It feeds on all sorts of
leaves including pine needles, and does not restrict its diet to one

INSECTS INJURIOUS TO VEGETATION 45

or a few plants, as do so many other kinds of insects. Theadults
are brownish and inconspicuous, with a spread of wings of an
inch and one half. The female (Fig. 26, A) is too heavy to fly
and therefore lays her eggs near where she emerges from her
cocoon. Methods of control are therefore similar to those em-
ployed for the tussock moth. Many birds feed on the moths

Fic. 27.— The leopard moth: A, female; B, male; C, larva in burrow; D,
pupal skin from which moth has emerged. (From Insect Life.)

and caterpillars, notably the cuckoo, Baltimore oriole, bluejay,
and yellow-throated vireo. The United States Bureau of Ento-
mology has been trying for years to introduce predaceous and
parasitic insects that will kill off the gypsy moth, but so far has
been only partially successful. Perhaps more effective than
these is a disease called flasherie which kills off vast numbers of
caterpillars each year. It is interesting to note that Pasteur
many years ago in France studied a similar disease of the silk-
worm and was able thereby to save the silk industry of that

46 PRACTICAL ZOOLOGY

country. Incidentally, this study was part of a series of studies
which led to a cure for hydrophobia.

Leoparp Moru.— The caterpillar of another moth, the
leopard moth (Fig. 27), is an important shade-tree pest, but with
very different habits from those of the gypsy moth. The leopard
moth was also introduced from Europe. Both the adults and
larve are spotted like a leopard. The male moth (Fig. 27, B)
expands a little more than an inch and the female (Fig. 27, A)
over two inches. The larve, which are about two inches long
(Fig. 27, C), burrow into the wood of trees that are weakened by
the weather or by some other insect. Serious attacks can be
prevented by digging out the boring caterpillars as soon as they
appear, or by collecting the adults as they congregate in the
evening beneath electric street lights.

OTHER SHADE-TREE Pests. — A few of the multitudes of
shade-tree insects are the elm-leaf beetle, the elm-bark louse, tent
caterpillars, fall webworm, elm, maple, and locust borers, and
cottony maple scale. Certain trees are less liable to attack than
others. For example, the tulip tree and the hardy catalpa are
practically immune from insect injury; oak trees suffer some
damage; the Norway maple, white oak, and honey locust, each
have one somewhat serious enemy; the linden, horse chestnut, and
soft maple have at least one notorious insect pest; and the elm,
cottonwood, and black locust are the most seriously injured of all.

MEeEtTHopS oF ConTROL. — A great deal can be done to check
the spread of shade-tree pests by planting different kinds of trees
near each other, rather than massing many of one kind together.
Since each insect is usually restricted to one kind of food, the
planting of different sorts of trees will prevent the spread of insects
from one tree to another. This should always be kept in mind
when planting a row of trees. For example, the forest tent cat-
erpillar is a serious enemy of the sugar maple, but not of the soft
maple ; hence if these trees are placed alternately in a row, wan-
dering tent caterpillars would have difficulty in getting from one
sugar maple to another. It. takes many years for a tree to reach

INSECTS INJURIOUS TO VEGETATION 47

the size when it is most valuable, and the importance of preserv-
ing the shade trees of our city streets cannot be too strongly
emphasized.

It is highly desirable that citizens should band together in
the interest of good shade. A most excellent plan was recently
urged by one of the Washington newspapers. It advocated a
tree protection league, and each issue of the paper through the
summer months contained a coupon which recited briefly the
desirability of protecting shade trees against the ravages of in-
sects, and enrolled the signer as a member of the league, pledging
him to do his best to destroy the injurious insects upon the city
shade trees immediately adjoining his residence. This was
only one of several ways which might be devised to arouse
general interest. The average city householder seldom has more
than half a dozen street shade trees in front of his grounds, and
it would be a matter of comparatively little expense and trouble
for any family to keep these trees in fair condition. It needs
only a little intelligent work at the proper time. It means the
burning of the webs of the fall webworm in May and June; it
means the destruction of the larve of the elm-leaf beetle about
the bases of the elm trees in late June and July; it means the
picking off and destruction of the eggs of the tussock moth and
the bags of the bagworm in winter, and equally simple opera-
tions for other insects, should they become especially injurious.
What a man will do for the shade and ornamental trees in his
own garden he should be willing to do for the shade trees ten feet
in front of his fence.?

REFERENCES

Economic Entomology, by J. B. Smith. —J. B. Lippincott Co., Philadelphia.

Injurious Insects, by W. C. O’Kane. — The Macmillan Co., N. Y. City.

Insect Pests of Farm, Garden, and Orchard, by E. D. Sanderson. — John
Wiley and Sons, N. Y. City.

Bulletins and Circulars published by the Bureau of Entomology, U.S. De-
partment of Agriculture.

1Howard, L. O., Circular 15, Bureau of Entomology, U. S. Department of
Agriculture.

CHAPTER V

INSECTS PARASITIC ON DOMESTIC ANIMALS AND

MAN

DOMESTICATED animals are those whose ancestors were once
wild, but which have been tamed because of their usefulness to

Fic. 28. — Horse botfly: A,
egg attached to hair; B, larva
showing spines; C, adult female.
(After Osborn.)

man. Insects may affect domestic
animals in a number of different
ways; first, by occasional attack
for the purpose of obtaining food;
second, by occasional attacks which
simply give irritation to the ani-
mal, as in the case of certain species
of flies; third, by living as parasites
during part of their existence, as
in bots; fourth, by living as para-
sites throughout their lifetime, as
with the lice; and, fifth, by living
as messmates or scavengers upon
the bodies of the animals without
deriving nutriment from them, as,
probably, some species of bird lice.!
Practically all of these insects are
parasites and are modified in struc-
ture and habits because of their
parasitic methods of life. Of the
hundreds of different kinds of in-

sect parasites the four most important groups are the bottlies,
fleas, lice, and ticks. Man, as well as the lower animals, is

attacked by them.

1 Osborn, H., nsects Affecting Domestic Animals.

48

PARASITIC INSECTS 49

Botflies. — The botflies are all heavy-bodied insects resem-
bling small bumblebees. Their mouth parts are very weak, and
it is probable that no food is eaten by the adults. The horse

botfly (Fig. 28, C) is about half an inch long, and brownish

Fic. 29.— Larve (bots) of the horse botfly attached to the wall of a horse's
stomach. (Photo by Osborn.)

yellow in color. It attaches its yellowish eggs to the hair on
the shoulders, legs, or belly of the horse (Fig. 28, A). These
eggs are licked off and swallowed by the horse, and the larve

which hatch from them (Fig. 28, B) fasten themselves by means
Eg

50 PRACTICAL ZOOLOGY

of rows of hooklets to the lining of the stomach (Fig. 29). Asa
result of the presence of several hundred “ bots,” the horse suffers
because of interference with its digestion, and from the irritation
caused by the insects. When full-grown, the larve pass out of
the alimentary canal with the excretions and pupate in the
ground. The eggs are plainly visible when attached to the hairs
of the animal; the hair should be shaved off or moistened
with kerosene, which
kills the eggs.

The sheep botfly
resembles the horse
botfly in general ap-
pearance but differs
from it in its habits.
The eggsof the sheep
botfly hatch within
the body of the fly
and the living young
are deposited during
June and July in the
upper nasal passages
of the sheep, where
they feed upon

Fic. 30.— Ox botfly or heel fly: A, adult; B,
eggs attached to hair; C, larva or grub; D, grub MuCUS. They are

just beneath air-hole in skin of an ox. (After
Ransom.)

provided with short,
stiff spines which
enable them to move forward, and with mouth hooks by
means of which they can attach themselves to any place se-
lected. Sometimes these disgusting larve even make their
way through the skull and into the brain, causing “ staggers,”
a disease that results in death. A mixture of tar and grease
smeared on the sheep’s nose is partially successful in warding
off the attacks of these flies. When the sheep actually become
parasitized, the bots may be dislodged by causing the animals
to sneeze them out, the sneezing being induced with powdered

PARASITIC INSECTS 51

lime or by tickling the inside of the nostrils with a feather dipped
in turpentine.

The ox heel fly has still a different life history. The eggs
(Fig. 30, B) are fastened to the hair near the heels of cattle and
licked off as are those of the horse botfly. The larve (Fig. 30,
C) act very differently, however. They bore their way through
the walls of the cesophagus and through the body, until after
about six or eight months they finally lie just beneath the skin
of the back, where they make a breathing hole through the
hide (Fig. 30, D). When full-grown, they are about two thirds
of an inch long; they then burrow out and drop to the ground,
where they complete their life history. The heel fly causes
losses of three kinds; first, loss in milk and flesh; second, damage
to hides from being punctured; and third, loss in trimming out
damaged meat from dressed carcasses. The loss of milk due
to these insects may be as high as twenty-five per cent; the loss
in flesh is estimated at from one to five dollars per animal; and
that to the hide at about sixty-five cents each. The entire
annual loss to the sixty million cattle in the United States, of
which about fifteen million are infested, is estimated at from
fifty-five to one hundred and twenty million dollars. The most
successful method of dealing with the bots is to remove them
one by one from the backs of the cattle by squeezing them partly
through the breathing pores made in the hide and then extract-
‘ing them with tweezers.

Human beings may under abnormal conditions be attacked
by bots. There are a number of cases on record, but they are
so rare that no one need be afraid of becoming a victim.

Fleas. — The flea is a degenerate insect with an extremely
small head and no wings. Unlike most of its relatives, its body
is very narrow and deep instead of broad and flat; this enables
it to glide easily among the hairs or feathers of its host. Its
legs are adapted for leaping, and the biting mouth parts of the
larva are adapted for feeding upon particles of decaying animal
and vegetable matter, Fleas are present on a great many kinds

52 PRACTICAL ZOOLOGY

of animals, including the dog, cat, rabbit, pigeon, and poultry,
and are often a nuisance to man.

The jigger fica, or chigoe (Fig. 31) is a common pest of man
in tropical and subtropical countries. When ready to lay eggs,
the female burrows into the skin, usually of the feet, causing a
swelling which may become a dangerous ulcer. The best way to
get rid of this uncomfortable parasite is to prick out the entire

D

Fic. 31.— The jigger flea or chigoe: A, larva; B, adult; C, side view of
adult after a meal; D, front view of same; E, head and legs much magnified.
(After Karsten and Guyon.)

insect, being careful not to break the body so as to free the eggs,
as this might lead to serious trouble.

The cat and dog flea (Fig. 32) is very common in houses almost
all over the world. It is a minute reddish brown insect with a
row of black, toothlike spines on each side of the head. The
eggs (Fig. 32, B) are laid in the fur of the infested animal, but they
are not very firmly attached and when the cat or dog walks about,
they are widely scattered. A kitten thus infested is said to have
left fully a teaspoonful of eggs upon the dress of a lady in whose

PARASITIC INSECTS 53

lap it had been held for a short time. The eggs hatch in about
ten days; the larve are full-grown in twelve days, and the adult
emerges two weeks later. :

The house flea is very much like the cat and dog flea but lacks
the spines on the side of the head. House fleas usually conceal
themselves in bedding and clothing, venturing out, particularly
at night, to feed upon the blood of their victims. Their eggs
are laid in dusty crevices or under carpets. “The careful removal
of dust will decrease their numbers and a thorough dusting of

Fic. 32.— Cat and dog flea: A, adult; B, Egg; C, larva in cocoon. (After
Howard.)

their breeding places with insect powder (pyrethrum) will
destroy them, but no amount of cleanliness will protect a human
being who enters an infested building. Recently fleas have
become of special world-wide importance because of their rela-
tion to the transmission of bubonic plague. (See Chapter X,
page 98.)

Ticks. — Many more or less degenerate insects are called
“ticks,” although this name really belongs to certain small
relatives of the spider possessing four pairs of legs. The
ticks are parasitic on certain birds, sheep, and horses. Of these
the sheep tick (Fig. 33) is especially important. This insect is
about one fourth of an inch long and spider-like in appearance,
with strong sucking mouth parts but no wings. It moves about

54 PRACTICAL ZOOLOGY

readily through wool and sucks the blood from its host. The
loss of blood and the irritation caused by ticks hinders the
proper development of sheep and when lambs are attacked death
often occurs. To destroy ticks, sheep should be dipped after
shearing in solutions containing kerosene, tobacco, tar, etc.
Such practice not only kills the ticks
but it also destroys lice and scab
” mites if these are present.
bs Lice. — A fourth group of degen-
- SS erate parasitic insects is made up of
the sucking lice. These also are
wingless. They possess mouth parts
adapted for sucking blood from the
Fic. 33.—Sheep tick. En- poultry, cattle, sheep, and other
Pe Pagy Sena ese domestic animals which they para-
sitize, and also from man. Some
kinds of lice have biting mouth parts with which they feed on
pieces of feathers. The commonest bird louse is the chicken
louse (Fig. 34, A), a pale yellow insect about one twenty-
fifth of an inch long. The eggs or ‘“ nits” are fastened to
the feathers, and the young, which hatch ten days later,
begin at once to feed on the feathers. The irritation caused by
the sharp claws of the lice often causes the fowls to dust them-
selves in the road or a dust box provided for them, thus removing
the lice. A mixture of sulphur and lime will help to rid both the
poultry house and the poultry themselves of their parasites.
Sucking lice occur on a great many domestic animals, and
some, like the ox louse and hog louse, are often very injurious.
Those best known are the three that sometimes infest human
beings, the head louse, crab louse, and body louse (Fig. 34, B,C,
and D). These lice are small, gray or yellowish in color, and
elongate oval in shape. They fasten their eggs or ‘nits’ to
the hairs of the body and live among them. Lice are, of course,
present only on unclean persons, and may be removed easily.
They are sometimes very numerous on men crowded together

PARASITIC INSECTS 58

in camps or prisons. The irritations they produce cause what is
known as Pediculosis or Phthiriasis, after the scientific name of
the insect. Lice may move from one person to another, so that
cleanliness will not always prevent their appearance. The

Fic. 34. — Four different kinds of lice.

A, chicken louse; B, head louse; C, crab louse; D, body louse. (After
Piaget and Denny.)

best remedies for the head louse are a fine-tooth comb and a
thorough greasing of the hair, which chokes the lice. The body
lice which infest clothing may be killed by boiling the garments
in water, baking them, or dipping in gasoline. Wherever irrita-
tions of the skin occur, an application of a mercurial ointment or

56 PRACTICAL ZOOLOGY

of tincture of larkspur should be made. Savages effectually
destroy lice by covering their bodies with grease, oil, or paint.

REFERENCES
Our Insect Friends and Enemies, by J. B. Smith. — J. B. Lippincott Co.,

Philadelphia.
Injurious Insects, by W. C. O'Kane. — The Macmillan Co., N. Y. City.
Insects Affecting Domestic Animals, by Herbert Osborn. — Bulletin 5,

Bureau of Entomology, U.S. Department of Agriculture.

CHAPTER VI
INSECTS OF THE HOUSEHOLD

ALMOST every house is invaded at some time during the
summer by insects other than the house fly which seems to be
always present. Some of these insects, like the house fly, stable
fly, mosquito, flea, and bedbug, will be described in Chapters
VIII, IX, and X in connection with the transmission of disease
germs. The other household insects either simply make them-
selves a general nuisance, like the cockroach and the silver fish,
or contaminate food, as do the ants, meal worm, and cheese skip-
per, or destroy clothing, rugs, carpets, etc., like the carpet
beetle and clothes moth.

Silver Fish. — The silver fish (Fig. 35, A) is one of the simplest
of all insects. It has no wings, but is not degenerate, since
neither it nor its ancestors ever possessed wings. The silvery
appearance of its body, which is due to very small scales, sug-
gested its common name. Starchy substances serve as food
material and this is gnawed at night or under cover, since the
silver fish always works in the dark. Very little if any damage
is done by these insects, but one doesn’t like to have the house
overrun with them. They may be destroyed by dusting pyre-
thrum powder in their hiding places.

Cockroaches. —— Four different kinds of cockroaches are com-
mon in this country, the American cockroach, the Oriental cock-
roach (Fig. 35, B), the Australian roach, and the German roach
or ‘croton bug.”’ All of them are very flat, soft-bodied insects
able to creep into small crevices, and provided with slender legs
fitted for running. They work at night and have a preference
for kitchens, where they feed on all sorts of scraps, leaving a

57

58 PRACTICAL ZOOLOGY

disagreeable odor behind them. “‘ Moist articles are preferred,
and a warm, wet dishrag which is not washed after using has
almost irresistible attractions. If there was only one roach in
a kitchen and I wanted that roach, I would place just such a rag
on the middle of the floor soon after dark, and I would expect
that roach there before ten o’clock. This applies more particu-
larly to the large Oriental roach or ‘ black beetle,’ which is very
heavy, does not climb much, and prefers moist places.’ }

Fic. 35. — Insects of the household.

A, silver fish or fish moth; B, cockroach; C, red ant. (After Sedgwick
and Riley.)

To rid a house of roaches one must use several remedies and
persist in their use for some time. Two of those often recom-
mended are (1) a mixture of sugar or chocolate with borax, and
(2) plaster of Paris and flour. The sugar or chocolate attracts
the roaches and the borax kills them. The plaster of Paris and
flour mixture should be placed on a saucer with a saucer of water
near by. Eating the mixture makes the roaches thirsty and
causes them to drink water; the plaster becomes hardened in
their intestines, and death results.

Ants. — Ants often become very troublesome in houses. The

1Smith, J. B., Our Insect Friends and Enemies.

INSECTS OF THE HOUSEHOLD 50

large black ants are simply visitors from outside that enter oc-
casionally in search of food. The little red ant (Fig. 35, C),
however, lives in large nests or colonies in the walls or under the
floors. If the nests can be found, they should be destroyed,
otherwise the ants must be trapped with pieces of meat or with
sponges containing sweetened water; the latter can be dropped
into boiling water and then “ set” again. Recently an interest-
ing method has been used in California to destroy the Argentine

Fic. 36.— Insects of the household.
A, cheese skipper; B, meal worm; C, beetle into which meal worm develops.

(After Chittenden.)
ant. Pans of slow-acting poison were set out. The ants not
only fed on this themselves, but carried it to their young, and,
as a result, entire colonies were exterminated.

Cheese Skipper. — Articles of food are also rendered unfit
to eat by insects which burrow into them. The cheese skipper
(Fig. 36, A) breeds in soft cheese and the fatty parts of hams
and bacon. The adults are minute, grayish flies, and the larve
are maggots. Thorough cleaning, followed by fumigation, will
destroy these insects.

60 PRACTICAL ZOOLOGY

Meal Worm. — The yellowish or brownish meal worm (Fig. 36,
B and C) that sometimes appears in oatmeal and other meals
is the larva of a dark, oblong beetle. Heating the meal will kill
the eggs, larve, and adults.

Carpet Beetles. — Perhaps the most exasperating of all house-
hold pests are the carpet beetles or “ buffalo moths” and es-
pecially the clothes moths. The adult buffalo moth is a dark,
white-mottled beetle (Fig. 37, A) about three sixteenths of an.
inch long. Its larvae, which are oval, hairy-coated, and about
one fourth of an inch long (Fig. 37, B), feed on the wool in carpets,

I'ic. 37. — Insects of the household.

A, carpet beetle; B, larva of carpet beetle; C, clothes moth; D, larva of
clothes moth. (After Riley.)

usually working underneath and following a crack in the floor.
When an attack has been discovered, the carpet should be taken
up and sprayed with gasoline, and the cracks of the floor should
be scrubbed with hot suds and then treated with gasoline.
Clothes Moth. — Clothes moths (Fig. 37, C) are small grayish
insects that lay their eggs in woolens or furs. The larve (Fig.
37, D) which eat these animal textiles are to be feared only in the
summer in the North, but they are busy throughout the year in
the South. A few precautions will prevent serious injury,
Winter clothes laid away over summer should be taken out
occasionally, hung in the sunlight, and thoroughly beaten or
brushed to free them from the intruders. | Moth balls help keep

INSECTS OF THE HOUSEHOLD 61

out the moths, and clothing tightly sealed in boxes or paper
bags will not be attacked.

REFERENCES
Insects Injurious to the Household, by G. W. Herrick. The Macmillan Co.,
New York City.
Bulletins and Circulars published by the Bureau of Entomology, U.S. De-
partment of Agriculture.

CHAPTER VII
BENEFICIAL INSECTS

So much has been written about injurious insects that it seems
as though none are of value to man. This is not at all true, since
many insects pollinize flowers, others act as scavengers, and
a few produce lac, cochineal, tannic acid, medicines, and even
food for human beings. Besides these the silkworm and honey-
bee have become almost indispensable because of the silk, honey,
and wax they furnish.

Fic. 38. — Silkworm: A, caterpillar; B, cocoon; C, adult female moth.
(From Shipley and MacBride.)

Silkworm. — The silkworm (Fig. 38, A) is really a domesti-
cated animal, just as much as the horse, dog, or cat. It is the
caterpillar of a moth and has a life history as follows: The
female moth (Fig. 38, C) lays about three hundred eggs on pieces
of cloth or paper provided for it. When the caterpillars hatch,
they begin to feed at once on leaves of the mulberry, osage
orange, or lettuce. At the end of about six weeks they begin to
spin their cocoons (Fig. 38, B). The fluid which forms the silk
is produced in the silk glands of the caterpillars; it passes out
through the spinneret and hardens on coming into contact with

the air. The caterpillars first attach the thread to near-by
62

BENEFICIAL INSECTS 63

objects and then form an oval structure about themselves
by winding round and round a single thread a thousand feet
in length or thereabouts. The adult moth develops within
this cocoon and emerges in about two weeks if undisturbed.
To get the silk, however, it is necessary to kill the animal within
the cocoon, since if this is not done, the moth destroys one end
of it when it comes out. After killing the animal quickly in
boiling water or by dry heat, the loose silk is cleared away, the
end of the thread found and unwound. Over one hundred
million dollars are invested in silk industries in this country.

Fic. 39. — Honeybees.
A, worker; B, queen; C, drone. (After Phillips.)

Honeybee. — The honeybee is also a domesticated animal,
but it even now often returns to its former wild state, making its
home in a hollow “ beetree.’”’ The number of bees in a pros-
perous hive is about sixty thousand. Most of these are sexually
undeveloped females, called workers (Fig. 39, A); a few are
males or drones (C), and one is the queen (B). The queen lays
all the eggs, the drones fertilize the eggs, and the workers carry
on all the activities of the hive. The wax out of which the
honeycomb is built is secreted by the glands on the undersur-
face of the abdomen of the workers (Fig. 40, A). The wax cells

64 PRACTICAL ZOOLOGY

are used for rearing the young and storing honey. Honey is not
collected from flowers, but is manufactured from the nectar of
flowers. Worker bees lap up the nectar with their tongues and
suck it into a honey sac within the body, where it is stored until
they return to the hive. Then the nectar is disgorged into the
wax cells and left until all but eighteen to twenty per cent of the
water contained in it has evaporated. The cell is then sealed
with a cap of wax. The flavor
of honey depends upon the
kind of flowers visited by the

Fic. 40. — Worker honeybees.
A, removing wax scale; B, carrying pollen. (After Casteel.)
bees. In a single season a hive of bees will produce about
thirty pounds of comb honey, which nets the bee keeper from
ten to fifteen cents per pound.

Among the other duties of the worker bees, besides those of
building honeycomb and manufacturing honey, are the cleaning
of the hive, ventilating the hive, guarding the hive, carrying
water to the hive for the young in warm weather, feeding the
young, and gathering pollen (Fig. 40, B). Pollen grains are
the very small fertilizing elements in flowers. Pollen is gathered
by the legs of the workers (p. 27, Fig. 12), stored in wax cells,
and furnishes the principal food of the larve. Bees swarm in
early summer, when the bive is in danger of overcrowding.
The workers rear a second queen when the hive becomes
crowded, and the old queen then leaves the hive with a few
thousand workers and founds a new colony.

BENEFICIAL INSECTS 65

Cochineal, Lac, etc. — Of less value to man than the products
of the silkworm and the honeybee are cochineal, lac, tannic acid,
and medicines. The coloring matter known as cochineal is made
from a scalelike insect that lives on cactus plants in Mexico and
Central America. Lac is derived also from scale insects which

le Bina aie

Fic. 41. — A modern beehive. (Photo by Hegner.)

occur principally in the Orient. It forms the base of many fine

polishes and lacquers of India, China, and Japan. Part of the

tannic acid used in the manufacture of leather is extracted from

the swellings on certain plants, called galls (Fig. 42), which are

caused by insects. The black coloring matter in some kinds
F

66 PRACTICAL ZOOLOGY

Fic. 42. — Types of insect galls.

A, willow cone gall; B, blackberry knot gall; C, goldenrod gall; D, oak gall.
(From Beutenmuller.)

BENEFICIAL INSECTS 67

of inks comes from insect-made galls. While formerly many in-
sects were used as ingredients in medicaments, now only a few
are thus employed. Of these the blister beetles are the most
important, especially the Spanish fly, which is collected in vast
numbers, dried, and powdered; it has the property of producing
blisters when applied to the human skin.

Food for Man. — Although it is of very little importance, it is
interesting to note that certain insects have at various times and
in various places been used as food by man. Grasshoppers are
eaten by the savages in many countries; when fried, they ‘are
said to have a sweet flavor, while in a stew with milk they re-
call oysters.”” The eggs of a water bug are in some localities
in South America gathered, dried, and baked into a cake by the
natives, and in tropical countries young ants often serve as food
for uncivilized mankind.

Scavengers. — The benefits derived from insects which act
as scavengers are very little appreciated. To determine their
effectiveness one has only to place a small dead animal in a field.
Flies find the carrion almost immediately, lay their eggs on it,
and the maggots which soon hatch from these eggs immediately
begin to devour it. The great Swedish naturalist, Linneus,
once said that a fly could devour the carcass of a horse more
quickly than could a lion. The burying beetles also attack
dead bodies, digging out the earth from underneath and slowly
burying them in the ground.

Other insects feed upon dead and decaying vegetable matter,
reducing such obnoxious substances as the excrement of horses
and cattle to harmless material that soon becomes mixed with
the soil. In fact “if all the insect scavengers were removed at
one time and all dead animal and vegetable material left to other
decays, the foulness and noxious odors that would be thus let
loose are beyond all description.”

The most interesting of all the scavenger insects are the
“tumblebugs ” (Fig. 43). The young of these beetles live in
animal excrement and the adults are often found in the fields

68 PRACTICAL ZOOLOGY

rolling large balls of dung to some burying place for the purpose
of laying their eggs in it and thus storing up a food supply for
their offspring. One of these dung beetles is the Sacred Scara-
beeus which was held in high veneration by the ancient Egyptians
and was used as a model for gems, was painted on sarcophagi,
and carved in stone.

Fic. 43. — Scarab beetles, or tumblebugs, rolling an egg-ball of dung. Egyptian
sculptures of sacred scarab. (After Brehm.)

Pollinization of Flowers. — Another indirect benefit derived
by man from insects is the result of the relation between bees,
wasps, etc., and flowers. Before seeds can be produced, the
pollen grains which are borne by’ the stamens of the flower
(Fig. 44, B, sta) must become attached to the style (s) of the same
kind of flower, where it fertilizes the ovule () from which the seed
develops. It has been found by experiments that when the
pollen from one flower fertilizes the ovules of another flower (a
process known as cross-pollination), better seed and more seed

BENEFICIAL INSECTS 69

is formed than when the pollen of a flower fertilizes the ovules
of the same flower (self-pollination). Many plants are cross-

Fic. 44. — A, fig insect whose introduction has made Smyrna fig culture possible
in California. (After Westwood.)

B, plum blossom; 0, ovary; p, petal; se, sepal; sfa, stamen; s/, stigma;
s, style. (After Bailey.)

pollinated only by insects and would not produce good seed if
insects did not fly from one flower to another and thus distribute
the pollen grains that
become attached to
their bodies. In some
cases the insects seem
to realize what they
are doing, since they
deliberately transfer
pollen from the sta-
men to the pistil. The
plants are benefited
directly by the pro-
duction of better seed,

es Fic. 45. — Predaceous insects.
and man indirectly A, tiger beetle; B, European ground beetle im-

with larger and better ported to prey upon the gypsy and brown-tail
moths. (After Bruner and Howard.)

crops. In return, the
insects take nectar from the flowers as their transportation
charges.

The dependence of plants upon insects is well illustrated by
the Smyrna fig. Prior to the year 1go0o this fig could not be

70 PRACTICAL ZOOLOGY

grown in the orchards of California, but since then the causes
have been found, and the remedy applied with satisfactory re-
sults. The figs did not ripen because their flowers were not
pollinized. When pollination was found to be accomplished by
a minute insect (Fig. 44, A), this insect was introduced into the
fig-growing districts of California and a successful new industry
established.

Predaceous Insects. — Beneficial from another standpoint
are predaceous and
parasitic insects. A
predaceous animal is
one that feeds directly
upon another. Most
insects feed on vege-
tation, that is, are
herbivorous, but a
goodly number devour
animal matter and
are carnivorous (Fig.
45). The latter per-
haps in the majority

ies of cases, feed upon

Fic. 46.— Australian ladybird beetle and fluted .
seat other insects, and
a, larve of beetle feeding on scale; 6, pupa of since as a general rule

beetle; c, adult beetle; d, orange twig showing ; Se ee

ee eee insects are injur
scales and beetles. (After Marlott.) eae Ne
it is safe to conclude

that predaceous insects are beneficial, although they may
occasionally destroy useful animals.

Rivaling in interest the establishment of the fig industry in
California is that of the salvation of the orange and lemon trees
of the same region. Kellogg gives the facts in this case in the
following words: ‘In 1868 some young orange trees were
brought to Menlo Park (near San Francisco) from Australia.
These trees were undoubtedly infested by the fluted scale (Fig.
46), which is a native of Australia, These scale immigrants

BENEFICIAL INSECTS 71

throve in the balmy California climate, and particularly well
probably because they had left all their native enemies far be-
hind. By 1880 they had spread to the great orange-growing
districts of southern California, five hundred miles away, and
in the next ten years caused enormous loss to the growers.
In 1888 the entomologist Koebele, recommended by the gov-
ernment division of entomology, was sent at the expense of the
California fruit growers to Australia to try to find out and send
back some effective predaceous or parasitic enemy of the pest.

Fic. 47. — Parasitic Insects.

A, parasitic Ichneumon fly laying eggs in the cocoon of a tent caterpillar; B,
parasitic tachina fly; C, part of an army worm with tachina fly eggs attached
to it. (After Fiske.)

As a result of this effort, a few Vedalias (Fig. 46) were sent to
California, where they were zealously fed and cared for, and soon,
after a few generations, enough of the little beetles were on hand
to warrant trying to colonize them in the attacked orange groves.
With astonishing and gratifying success the Vedalia in a very
few years had so naturally increased and spread that the ruth-
less scale was definitely checked in its destruction, and from
that time to this has been able to do only occasionally and in
limited localities any injury at all.”

Parasitic Insects. — Parasitic insects (Fig. 47) are those that

72 PRACTICAL ZOOLOGY

live in or are carried about on the bodies of other animals. Some
of them are harmful, such as lice, but others are beneficial because
they parasitize and kill other injurious insects. As a rule the
parasites are very small. They lay one or more eggs in or upon
the body of their victim, the host, and the young insect that
soon emerges from the egg feeds slowly upon the substance
within the host’s body. It finally reaches the adult stage and
leaving the remains of its victim behind, escapes in search
of new prey. At the present time many insect pests, such as
the army worm, tussock moth, and gypsy moth, are partially
held in check by parasites, and the Bureau of Entomology of
the Department of Agriculture is making all possible efforts
to introduce into this country parasites from foreign lands in
the hope of finding some that will equal the performances of
the predaceous Vedalia lady beetle.

REFERENCES
Our Insect Friends and Enemies, by J. B. Smith. — J. B. Lippincott Co.,
Philadelphia.
Bulletins and Circulars published by the Bureau of Entomology, U. S.
Department of Agriculture.

CHAPTER VIII
THE HOUSE FLY AND DISEASE

No animal has been subjected to a more careful study within
recent years than the house fly. The reason for this is that the
house fly distributes the germs of various diseases, thus causing
the death of thousands of human beings every year. As we
shall see later (Chaps. IX and X), the house fly is not the
only guilty insect, but its abundance makes it especially im-
portant.

Disease Germs. — The disease germs that are carried by flies
and other insects must be described before it is possible to dis-
cuss properly their method of transmission. These germs are
either plants called Bacteria or animals called Protozoa. (See
Chapter X XV.) In either case they are exceedingly small, so
minute in fact that many of them can only be seen with the
highest magnifications of the compound microscope and some,
like the yellow-fever germ, have never been seen.

Bacteria. — The bacteria (Fig. 48) are of various shapes and
sizes, being as a rule spheres (micrococci), straight rods (bacilli),
or bent rods (spirilla). They range in size from zz}y5 to about
zday Of an inch in length. Some bacteria are able to move, but
many must be carried from place to place. Bacteria increase
in number by reproduction, just as do the grasshopper and other
living things. The body of the bacterium divides in the middle
into two, a process known as binary fission. Then each part
grows rapidly and divides again. In some cases bacteria become
full-grown and divide every half hour. How many offspring
would be produced in twenty-four hours by such a bacterium

73

74 PRACTICAL ZOOLOGY

can be estimated by any one who is mathematically inclined.
Bacteria, like other living things, must have food (which con-
sists of mineral matter and plant or animal substances), mois-
ture, and usually free oxygen. Fortunately, only a few bacteria
cause diseases; these are called pathogenic. The others, or non-
pathogenic bacteria, act as scavengers in the earth, furnish food
for plants, and are used in variousindustries, such as in the manu-
facture of linen and cheese. Bacteria are almost everywhere;
they are in every breath of air we breathe, in most of the water
we drink, and are abundant in the earth.

ij

A sd :
2

Fic. 48. — Disease germs — bacteria. A
A, typhoid; B, tuberculosis; C, cholera; D, anthrax; E, a blood corpuscle
engulfing a germ.

How To Destroy Bacteria. — It is necessary to know how
to destroy or prevent the increase of bacteria in order to protect
ourselves from the pathogenic kinds. Cleanliness will of course
dispose of most of those that rest upon the surfaces of our bodies.
Within the body, juices and white blood corpuscles are contin-
ually at work destroying many of those that manage to get in.
Various agents are employed for controlling bacteria. Sub-
stances called antiseptics prevent their growth; disinfectants or
germicides kill pathogenic forms; and all kinds are killed by

THE HOUSE FLY AND DISEASE 75

sterilization. We base our methods of control upon our knowl-
edge of the agents harmful to bacteria. Sunlight is their great-
est destroyer, whereas they grow best in the dark. Heat stops
their multiplication at tog.4° F., and cold at 60.8° F. Many of
them are killed at 32° F., but unfortunately the bacteria causing
typhoid fever and Asiatic cholera are not, and hence may be dis-

wy
LIT Privy
Wry
aie PAO RARARAHAN
; RB RINN
if

Fic. 49. — Foot of the house fly.

A, end of foot showing claws and bristles; B, opposite side of foot showing
fleshy lobes, the pulvillus; C, part of pulvillus much enlarged showing
hooked hairs. (After Smith.)

tributed in ice. It is evident that the cooling of foods, such as
milk, will prevent the multiplication of germs and hence keep
them from spoiling, and that surgeons’ instruments may be
rendered aseptic, that is, free from bacteria, by heating or boiling.
Gases, such as formaldehyde, and liquids, such as bichloride of
mercury and carbolic acid, are commonly used as disinfectants.

76 PRACTICAL ZOOLOGY

How Germs Are CarriEpD. — The house fly is important
because it carries on its body or in its alimentary canal many of
the pathogenic bacteria. Flies very easily become soiled with
particles of filth in which millions of bacteria live, and this filth
is transferred to any object upon which they alight. Most of the
germs are carried upon the /egs, or are taken into the alimentary
canal and vomited or deposited as excreta. That the legs are
very easily soiled is due to the presence upon them of numerous
hairs among which the germs become lodged (Fig. 49). Hairs

a Diy

INO,
J es
By

Fic. 50.— The lapping organ at the tip of the proboscis of the house fly.
(After Smith.)

on other parts of the body may likewise catch groups of bacteria.
The number of bacteria on a single fly has been found to average
about 1,250,000.

The mouth parts of the house fly also aid in the distribution of
germs. They are modified for lapping and form a sort of pro-
boscis. This is a fleshy organ about as long as the head, with
two lobes at the top covered with very fine ridges (Fig. 50).
Within the proboscis is a tube leading to the stomach. Solid
food, such as sugar, must be liquefied before it can be swallowed.
The fly does this by pouring out upon it a little saliva and then

THE HOUSE FLY AND DISEASE 77

rasping it with the lobes of the proboscis. If the fly chances to
feed on substances containing bacteria, these are taken into the
alimentary canal and later may be extruded through the mouth,
or deposited in the excreta which forms “ fly specks.”” The con-
clusion is evident: a fly that has access to substances containing
bacteria cannot help but become soiled by them and later
transfer them to other objects, such as articles of food (Tig. 51 a).

Fic. 51 a.—Plate of gelatine, showing colonies of bacteria in footprints of a
house fly. , (After Underwood.)

Germ Diseases Transmitted by House Flies. — After having
shown that the house fly carries bacteria, we must inquire as to
what sorts of diseases may be caused by these bacteria. Lack
of space makes it impossible to give the evidence upon which our
statement is made, but there is convincing proof that the germs
of typhoid fever, Asiatic cholera, summer diarrhoea, tubercu-
losis, yaws, ophthalmia, smallpox, and tropical sore are carried
by flies. The relation between flies and typhoid fever is well

78 PRACTICAL ZOOLOGY

known and so important that the house fly is now often spoken
of as the typhoid fly.

Typhoid Fever. — The typhoid fever germ is a bacillus ( Bacil-
lus typhosus) about zytya of an inch long (Fig. 48, A). It
occurs principally in the intestine, lungs, blood, and bladder of
man, and is taken into the alimentary canal with water, ice,
milk, and other foods. Typhoid bacilli are discharged from the
body in the excretory matter and in sputum. It is therefore
very important that all excretory matter from typhoid fever
patients be screened from flies or treated so as to kill the germs.
In certain cases the patient may have, to all appearances, com-
pletely recovered and yet continue excreting the typhoid bacilli.
These cases are known as “‘ carriers’ and the number of such
“carrier ’’ cases who continue to carry the typhoid germs in their
bodies is gradually increasing as the matter is being more care-
fully investigated. It is being discovered that many of the
inexplicable outbreaks of typhoid fever are due to the presence
of one of the chronic carriers. The presence of an unrecognized
“carrier ’’ excreting infected matter, the occurrence of large
numbers of flies, and their access to food or milk are all the
factors that are required to initiate an epidemic of typhoid
fever, and not a few epidemics are now being traced to the con-
currence of these factors.!

Dysentery. — Similar in some respects to the typhoid bacillus
is the bacterium that causes summer diarrhoea or dysentery in
children. The germ (Bacillus dysenteri@) resembles that of
typhoid in size and shape, and is taken into the system with
water and foods in the same way. The bacilli are especially
active in the intestines, where they cause serious disturbances,
often resulting fatally. It has been shown quite clearly that the
number of cases of summer diarrhoea corresponds very closely
to the number and activity of house flies. During wet seasons,
which are unfavorable for the multiplication of flies, the number
of cases of dysentery is much smaller than during dry seasons.

‘ Hewitt, C. G., House-Flics and how they spread Disease.

THE HOUSE FLY AND DISEASE 79

Tuberculosis.— It has been known for many years that flies
carry the bacillus of tuberculosis (Fig. 48, B), and everything
seems to point to the conclusion that the disease is at least to
some extent spread by them. Flies are attracted by sputum,
and when they chance to alight on that of tuberculous persons,
they take the bacilli into their intestines. Here the germs may
remain for days, during which the flies distribute them in their
excreta. The chief danger is from carelessness in the disposal
of sputum from tuberculous patients, since flies may easily carry
the germs to food. Some idea of the losses from tuberculosis
in this country may be judged from the following statistics.’

In 1906, 138,000 persons died from tuberculosis in the United
States, or at the rate of 164 per 100,000 population. Based
upon these facts, it is estimated that about 5,000,000 of those
now living in the United States will die of the disease. It is
claimed that the disease alone costs the United States from
$400,000,000 to $1,000,000,000 each year (Fisher).

It is estimated by the United States Bureau of Animal Indus-
try that 2 per cent of hogs in the United States are tubercular,
and that losses of stock in the United States, due to tuberculosis,
amount to $23,000,000 annually. Of 400,000 cattle tested in
the United States 9.25 per cent were tubercular.

Asiatic Cholera. — Asiatic cholera is a disease common in
India, from which place it frequently spreads throughout the
world. Several epidemics have occurred in America, and New
Orleans and other seaports are often threatened. The germ
that causes cholera is a spirillum bent in the form of a comma
(Fig. 48, C.) It gains entrance to the human body in food or
drink and lodges in the intestines. The method of spreading
cholera germs is therefore very similar to that of the typhoid
bacilli. The house fly is an important carrier and preventive
measures should be taken accordingly.

Other Diseases. — Not so much is known about the other
diseases that may be caused by germs distributed by flies. Cer-

1 Marshall, C. E., Microbiology.

80 PRACTICAL ZOOLOGY

tain tropical diseases are doubtless transmitted by insects.
Yaws, a disease caused by a spiral parasite, is probably carried
by house flies which infest the victims. The possibilities of
spreading the infection are obvious.

Another tropical disease, opthalmia, characterized by inflamed
eyes, is no doubt carried by flies, since hosts of these insects swarm
about the eyes of infected individuals.

Besides the germ diseases mentioned above, house flies prob-
ably distribute certain parasitic worms that occur in the intestines
of human beings. The eggs of such animals as the tapeworm are
very minute and are known to be sucked up by house flies.
These eggs may then be deposited by the fly upon the food of
man, and young tapeworms may be hatched and liberated in the
human stomach or intestines. The eggs of worms may also be
carried on the legs or proboscis of the flies.

Methods of Control.— To control the infectious diseases
spread by house flies it is necessary to prevent so far as possible
the multiplication of the insects and also to prevent those flies
that cannot be destroyed from distributing the germs. The
destruction of the flies is the best way to attack the problem,
but before we can do this intelligently we must know the life
history of the insect.

Breeding Habits of House Flies. — The eggs of house flies are
laid principally in horse manure, but may also be deposited in the
excreta of other animals, in decaying vegetables, fruit, and
grain, and in various kinds of garbage. The flies begin to breed
in June and continue to multiply until October. One fly deposits
about five hundred eggs, each about 3! of an inch long. Within
twenty-four hours the eggs hatch and the maggots that emerge
(Fig. 51 6, A) begin to feed upon the liquids surrounding them.
It takes the larva about five days to become full-grown; then it
pupates (Fig. 51 6, B). About four days later the adult fly
emerges [rom the pupal covering (Fig. 51 6, C). These adults are
ready to lay eggs in about two weeks, so that the life cycle from
egg to egg lasts a little over three weeks. During the summer,

THE HOUSE FLY AND DISEASE 81

manure piles contain an enormous number of maggots; an
average of fifteen hundred to every pound of manure has been
recorded.

Enemies of House Flies. —In the late autumn there is a
notable decrease in the number of flies and in winter none are
present except in warm situations. The question has often
been asked, What becomes of the flies in the winter, and where
do the flies come from in the spring? House flies, like all other
animals, have many enemies. Numerous birds, such as vireos
and pheebes, are known to catch them; predaceous insects, like

Fic. 51 b. — The house fly.
A, larva or maggot; B, puparium; C, adult. (After Howard.)

the wasps, destroy many of them; toads, frogs, and lizards
devour them whenever they get a chance; and the house centi-
pede (Fig. 52, A) is a constant enemy. These animals are all
attacking the flies during the summer. As autumn approaches
a fungous plant (Empusa musce) kills enormous numbers of
them; itis, in fact, their worst enemy. ‘This plant is responsible
for the death of the flies that are often found attached to window-
panes and surrounded by a grayish ring which consists of the
seedlike reproductive bodies of the plant (Fig. 52, B). A large
proportion of the flies die a natural death, but the vigorous
young crawl into crevices, where they pass the winter in a quies-
G

82 PRACTICAL ZOOLOGY

cent state. Like the woodchucks, certain bears, frogs, etc., they

hibernate during the cold, unfavorable months.
Prevention of Breeding. — The best means of decreasing the
number of house flies is undoubtedly to prevent them from breed-
ing. This means that the materials in

which flies lay their eggs and develop

should be protected from them in

some way. Horse manure is the

principal breeding material. Either

fly-proof receptacles or chambers

should be provided for manure, or
Y the manure, when accessible to flies,
Mg

Fic. 52. — Enemies of the house fly.

A, centipede; B, dead fly surrounded by spores from a fungous plant which has
killed it. (After Folsom.)

should be treated with some substance which kills the maggots.
A small amount of chloride of lime thrown over the manure
will do this, or an application of iron sulphate solution, in
the proportion two pounds of iron sulphate to one gallon of

THE HOUSE FLY AND DISEASE 83

water. These do not interfere much with the manurial
properties of the manure, and the horses will be more fit for
work if their stable is not infested with flies.

A second breeding place that needs attention is the old-fash-
ioned insanitary privy, where germs are gathered by flies and then
distributed over our food, and on the faces and feeding bottles of
infants. Wherever extra sanitary precautions have been taken,
a decrease in the death rate of infants due to intestinal diseases
has always resulted. Local authorities thus have a serious
responsibility in enforcing sanitary measures.

The third common breeding place of the house fly is in all
sorts of refuse, such as in unprotected garbage cans, city dumps,
etc.

It is possible to diminish the number of flies by catching the
adults in flytraps or with sticky fly paper, or by poisoning them.
An excellent method of killing flies is with a solution of two
tablespoonfuls of formalin in a mixture of one half a pint of sweet
milk and one-half a pint of water. This should be exposed in
shallow dishes with a piece of bread in the center on which the
flies may alight.

Prevention of Distribution of Germs. — The best means of
preventing the transference of germs are, first, the protection of
infected matter from flies, and, second, the protection of food, both
liquid and solid, and the protection of the faces of infants and in-
valids from flies. The necessity of preventing flies from gaining
access to excreta, infected or non-infected, is too obvious to need
insisting upon, nor should flies have access to tubercular sputum
or purulent discharges. The screening of food, of hospitals,
of the sick room, and of infants is a measure which should
be adopted as a matter of course rather than a hygienic
necessity.

It issafe to say that, if measures were taken to prevent flies from
breeding by doing away with possible breeding places, and also
to prevent their transferring infection from infected material,
the house fly would cease to be a serious factor in the carriage

84 PRACTICAL ZOOLOGY

of typhoid fever, tuberculosis, and intestinal diseases of
infants.!

Control by Departments of Health. — Public nuisances may
be abated by most health authorities and the breeding places
thus abolished. The rules issued in the District of Columbia
for this purpose have been summarized as follows: !

All stables in which animals are kept shall have the surface
of the ground covered with a water-tight floor. Every person
occupying a building where domestic animals are kept shall
maintain in connection therewith a bin or pit for the reception
of the manure, and, pending the removal from the premises of
the manure from the animal or animals, shall place such manure
in said bin or pit. This bin shall be so constructed as to exclude
rain water, and shall in all other respects be water-tight except
as it may be connected with the public sewer. It shall be pro-
vided with a suitable cover and constructed so as to prevent the
ingress and egress of flies. No person owning a stable shall keep
any manure or permit any manure to be kept in or upon any
portion of the premises other than in the bin or pit described,
nor shall he allow any such bin or pit to be overfilled or need-
lessly uncovered. Horse manure may be kept tightly rammed
into well-covered barrels for the purpose of removal in such
barrels. Every person keeping manure in the more densely pop-
ulated parts of the District shall cause all such manure to be
removed from the premises at least twice every week between
June 1 and October 31, and at least once every week between
November 1 and May 31 of the following year. No person shall
remove or transport any manure over any public highway in
any of the more densely populated parts of the District except
in a tight vehicle which, if not inclosed, must be effectually
covered with canvas, so as to prevent the manure from being
dropped. No person shall deposit manure removed from the
bins or pits within any of the more densely populated parts of
the District without a permit from the health officer.

1 Hewitt, C. G., House-Flies and How They Spread Disease.

THE HOUSE FLY AND DISEASE 85

Example of a City Fly Campaign. — As an example of what
may be accomplished in a city against the house fly we can cite
the results of a fly campaign that was carried on in Cleveland,
Ohio, during the years 1912 and 1913. Interest was created in
the public schools by the teachers and among the rest of the
people through the newspapers. First, the over-wintering flies
were attacked. Two hundred thousand fly swatters were dis-
tributed and ten cents per hundred flies was paid as a bounty.
Fifty thousand mother flies were killed in this way, at a compar-
atively low cost. The citizens soon became sensitive to the
presence of flies and as their numbers increased with the advance
of summer, dealers in meats and provisions, and the proprietors
of lunch rooms and restaurants were obliged to clean up the
breeding places and kill off the adult flies if they wished to keep
their customers. Many of the school children aided in the cam-
paign. The boys joined the Junior Sanitary Police Force for
the purpose of discovering unsanitary conditions in yards, alleys,
and vacant lots, and the girls were organized as Sanitary Aides
with the duty of decreasing the number of flies in stores where
food was kept. ‘‘ Before the close of the school year streets
were cleaned, alleys and vacant lots ceased to be dumping
grounds for filth, and the rubbish from back yards gave way to
gardens of flowers and vegetables.” ! Any city can carry out
a similar campaign, and many of them, in fact, are doing so.

REFERENCES

Microbiology, edited by C. E. Marshall. — P. Blakiston’s Son and Co.,
Philadelphia.

House-Flies and How They Spread Disease, by C. G. Hewitt. — Cambridge
University Press, England.

Bulletins and Circulars published by the Bureau of Entomology, U. S. De-
partment of Agriculture.

1 Dawson, J., Eliminating a City’s Filth and Flies.

CHAPTER Ix
MOSQUITOES AND DISEASE

In many parts of the world mosquitoes are even more impor-
tant than house flies as carriers of disease germs, but this has
been known for only a few years. Two of the most dangerous
of all diseases, malaria and yellow fever, are transmitted from
one person to another only by mosquitoes, and several other
diseases, such as dengue and elephantiasis, are spread, at least
in part, by these insects. Besides this, mosquitoes are probably
responsible for the transmission of germs with which we are not
yet acquainted.

How Germs are Carried.-- The mosquito differs from the
house-fly in several important respects. In the first place, its
mouth parts are fitted for piercing (Fig. 11, A), and it is thus
able to penetrate the skin and suck blood directly from the body.
Any germs that chance to be in the blood of the victim are thus
taken into the alimentary canal of the mosquito and may be
injected into the blood of the next person bitten. The house
fly carries germs upon its body or in its alimentary canal, and '
is not itself diseased; it is called a passive carrier. The mos-
quito, on the other hand, is an active carrier. Its blood stream
becomes filled with the germs, which are transported to the
salivary glands, where they are stored up until the insect bites;
then they pass with the saliva into the wound and infect the
person bitten.

What the Germs Are.— These germs are not bacteria, as are
those carried by the house fly, but minute animals called Protozoa.
(See Chapter X XV.) Those which cause malaria are visible
with the compound microscope, but the germs of yellow fever

86

MOSQUITOES AND DISEASE 87

have never been seen and we can only judge of their nature by
comparing the disease they cause with other similar diseases.

Fic. 53. — A, position of malaria mosquito (Anopheles) when at rest.
B, position of common house mosquito (Culex) when at rest. (After Howard.)

THe MarariaL Mosguito

Malarial fever is caused by minute parasitic Protozoa which
attack the blood corpuscles causing “ chills and fever.” This
was first demonstrated by a French army surgeon in Algiers
in 1880. Three kinds of malaria are recognized: (1) ‘Tertian

Fic. 54. — A, position of larva of malaria mosquito at surface of water.

B, position of larva of common house mosquito at surface of water.

C, raft of eggs of mosquito floating on surface of water.

D, eggs of house mosquito; E, eggs of malaria mosquito. (After Howard.)

88 PRACTICAL ZOOLOGY

fever is the commonest; it is caused by a Protozoén named
Plasmodium vivax and causes “ chills and fever” every third
day. (2) Quartan fever is due to Plasmodium malari@; it
causes ‘chills and fever’’ every fourth day. (3) Pernicious,
tropical, or estivo-autumnal fever is caused by Plasmodium
falciparum and produces “ chills and fever” at irregular inter-
vals. Not all mosquitoes carry these germs, only those belong-
ing to a group with the scientific name Anopheles. Fortunately
Culex mosquitoes are more common than Anopheles mosquitoes

Fic. 55.— Pupa of house mosquito Fic. 56. — Pupa of malaria mosquito at sur-
at surface of water. face of water. (After Howard.)

and are comparatively harmless. The two kinds can be dis-
tinguished by the position of the body when at rest; Anopheles
holds its body at an angle, whereas Culex takes up a horizontal
position, as shown in Figure 53. The eggs (Fig. 54, D and E),
larve (Fig. 54, A and B), pupa (Fig. 55), and adults differ also
in varlous ways, such as size and structure.

Anopheles the Guilty Mosquito. — To prove that the Anoph-
eles mosquitoes are guilty of transmitting the malarial fever
parasite an English physician had some of these insects sent to
him from a malarial district. He allowed them to bite him and
in due time he became a victim of the fever. Two other English

MOSQUITOES AND DISEASE 89

physicians visited certain marshes in Italy where malaria was
common and lived there for three months. Mosquitoes are not
active by day but are nocturnal in habit. These physicians
therefore went about outdoors freely during the daytime, but
as evening approached, went indoors, where they were careful
to protect themselves from being bitten. Neither of the men
was bitten and neither of them contracted the disease, whereas
their neighbors who did not protect themselves at night were
afflicted with the fever as usual.

Losses Due to Malaria. — It is rather difficult to determine
exactly the losses due to malaria. The annual death rate from
malaria in the United States is about twelve thousand. There
are, however, about three million cases every year, and since the
productive capacity of a man suffering from the disease is
reduced from fifty to seventy-five per cent, the loss is really
appalling. But this does not include everything, for there is a
loss to the country rising from the fact that many regions that
are excellent for agricultural purposes cannot be developed
because of the presence of malaria. After an investigation of
this disease in the five states of Louisiana, Mississippi, Alabama,
Georgia, and South Carolina, the following report was sub-
mitted:

We must now consider briefly what 635,000 or a million
cases of chills and fever in one year mean. It is a self-evident
truth that it means well for the physician. But for laboring
men it means an immense loss of their time together with the
doctors’ fees in many instances. If members of their families
other than themselves be affected, it may also mean a loss of time
together with the doctors’ fees. For the employer it means the
loss of labor at a time perhaps when it would be of greatest
value. If it does not mean the actual loss of labor to the em-
ployer, it will mean a loss in the efficiency of his labor. To the
farmers it may mean the loss of their crops by want of cultiva-
tion. It will always mean the non-cultivation or imperfect
cultivation of thousands of acres of valuable land. It means a

go PRACTICAL ZOOLOGY

listless activity in the world’s work that counts mightily against
the wealth-producing power of the people. Finally it means
from two to five million or more days of sickness with all its
attendant distress, pain of body, and mental depression to some
unfortunate individuals of those five states (Herrick).

Breeding Habits of Anopheles. — As in the case of the house
fly, the breeding habits of the mosquito furnish the key for its
destruction. Many kinds of mosquitoes lay their eggs in masses
that float on the surface of the water (Fig. 54, C), but Anopheles
deposits them singly, often close together (Fig. 54, E). The
larve, which hatch from the eggs in about three days, remain in
the water, feeding on the green scum on the surface. Their posi-
tion in the water differs from that of other species, since they lie
parallel to the surface (Fig. 54, A), whereas the larve of other
mosquitoes hang from the surface at an angle (Fig. 54, B). At
the posterior end of the body is a short breathing tube which is
thrust through the surface film. In about two weeks the
full-grown larve change to pupe (Fig. 55). These must also
remain near the surface, since they breathe through two tubes
that look like ears and project from the thorax. The pupal
stage lasts about four days, and then the adults emerge.
The adults are active at night and only the females bite.
During the winter mosquitoes hibernate in crevices as do
the house flies.

Enemies of Mosquitoes. — Mosquitoes fall a prey to many
natural enemies. The adults are devoured by certain night-
flying birds, such as the nighthawk, by dragon flies (the so-called
mosquito hawks), by spiders and toads, and by bats which fly
about at dusk just when the mosquitoes begin to get active.
The larve and pupe are destroyed in countless numbers by
insect-eating animals that live in the water, especially by small
fish and by the large carnivorous insects, such as water scorpions,
water beetles, and water boatmen. But while these enemies
certainly decrease the number of mosquitoes, they are not able to
prevent them from becoming a pest.

MOSQUITOES AND DISEASE oI

Control of Mosquitoes. — The Anopheles mosquito will breed
wherever there is a small accumulation of water. Small creeks
through meadow land, the ditches and gutters or drains along
railroad and other embankments, and the shallow overgrown
edges of ponds or swamp areas are favorite breeding places (Fig.
56). Pools containing grassy or other vegetation are nearly
always infested, and ponds with lily pads, dock, sagittaria, and
other plants of a similar character, are danger points. The

Fic. 57. — Oiling a pond near a railroad track where mosquitoes breed.
(After Herms.)

larve need only a mere film of water, and this being found over
a leaf or at a grassy edge, protects them from the usual natural
enemies. . . no other mosquito has as wide a range of breeding
places as have the species of Anopheles (Smith).

Two methods may be used to prevent mosquitoes from breed-
ing in such places. The best method is to remove all receptacles
in which water may collect and to drain all wet places. The
other method is to treat the breeding places so as to kill the wig-
glers (larve and pupe). Many different substances have been

Q2 PRACTICAL ZOOLOGY

tried with this end in view; the one used most in this country
is a low grade of kerosene oil. An ounce of oil will spread over
about fifteen square feet of surface, and the film thus formed will
destroy all wigglers and many of the adults which come to drink
or lay eggs. Such a film will persist for about ten days. Oil
may be applied to small bodies of water with a watering pot and
to larger surfaces with a spray pump.

Example of Mosquito Control. — As an example of the results
of work carried on in this way the antimalarial campaign waged
in Havana during the American occupation of 1901 to 1902 may
be cited. An Anopheles brigade of workmen was organized
under the sanitary officer, Doctor Gorgas, for work along the
small streams, irrigated gardens, and similar places in the sub-
urbs, and numbered from 50 to 300 men. No extensive drain-
age, such as would require engineering skill, was attempted, and
the natural streams and gutters were simply cleared of obstruc-
tions and grass, while superficial ditches were made through
the irrigated meadows. Among the suburban truck gardens
Anopheles bred everywhere, in the little puddles of water, cow
tracks, horse tracks, and similar depressions in grassy ground.
Little or no oil was used by the Anopheles brigade, since it was
found in practice a simple matter to drain these places. At the
end of the year it was very difficult to find water containing
mosquito larvee anywhere in the suburbs, and the effect upon
malarial statistics was striking. In 1900, the year before the
beginning of the mosquito work, there were 325 deaths from
malaria; in 1901, the first year of the mosquito work, 171 deaths;
in 1902, the second year of mosquito work, 77 deaths. Since
1902 there has been a gradual though slower decrease, as follows:
1903, 51; 1904, 44; 1905, 32; 1906, 26; 1907, 23.)

Driving Away Mosquitoes. — Mosquitoes not only carry the
germs of many diseases, but they are at all times disagreeable
companions, often rendering the most charming localities unin-

1 Howard, L. O., Economic Losses to the Peo ple of the United States through Insects
that Carry Disease.

MOSQUITOES AND DISEASE 93

habitable during the summer. Various preventives have been
devised to drive them away. Mixtures of camphor, oil of cit-
ronella, and cedar oil when applied to the face and hands will
protect one for a few hours; dense smoke will drive them away;
and several sorts of gases will expel them from houses, such as
burning sulphur, orange peel, or insect powder (pyrethrum).
Mosquito bites may be relieved by an application of moist soap,
ammonia, alcohol, or glycerin.

THE YELLOW FEVER Mosquito

In 1901 the mosquito known to science as Stegomyia calo-
pus was proved to be the carrier of yellow fever. This mos-
quito lives in tropical and semi-tropical countries, and differs
from the ordinary Culex and Anopheles mosquitoes in its habit
of biting in the daytime. It will breed in any kind of water
and in small amounts, so that the methods of destroying the
larve and pupe are like those employed for the Anopheles
mosquito. Outbreaks of yellow fever have occurred in many
cities in this country. Philadelphia suffered a severe epidemic
in 1793; New Orleans lost 8000 in the epidemic of 1853; in
1878 there were 125,000 cases and 12,000 deaths in the Southern
States.

Control in New Orleans. — The last serious outbreak took
place in New Orleans in 1905, and its history serves to illustrate
the value of the methods of attacking the problems that were
then just recently acquired. . The presence of yellow fever in the
city was first recognized about the 12th of July, and the plan of
campaign adopted was based on the theory that mosquitoes
carried the disease. By the 12th of August the increase in the
new cases and deaths rendered it practically certain that the
disease was as widespread as during the terrible epidemic of
1878. There had been up to that time 142 deaths froma total
of 913 cases, as against 152 deaths from a total of 519 cases in
1878. The work for the rest of the summer was continued with

94 PRACTICAL ZOOLOGY

great energy and the measures were based almost entirely upon
a warfare against the yellow fever mosquito. The disease be-
gan almost immediately to abate, and the result at the close of
the season indicated 460 deaths, as against 4046 in 1878, a
virtual saving of over 3500 lives.!

Control in Panama Canal Zone.— One of the most
interesting examples of the eradication of disease by the
destruction of mosquitoes is the campaign of the United
States Government in the Panama Canal Zone which was
begun in 1904.1

In Panama, as in Havana, the population had depended prin-
cipally upon rain water for domestic purposes, so that every
house had cisterns, water barrels, and such receptacles for catch-
ing and storing rain water. The city was divided into small dis-
tricts with an inspector in charge of each district. This inspector
was required to cover his territory at least twice a week and to
make a report upon each building with regard to its condition
as to breeding places of mosquitoes. All the cisterns, water
barrels, and other water receptacles in Panama were covered as
in Havana, and in the water barrels spigots were inserted so that
the covers would not have to be taken off. Upon first inspection,
in March, 4000 breeding places were reported. At the end of
October less than goo containing larve were recorded. This
gives one a fair idea of the consequent rapid decrease in the
number of mosquitoes in the city. These operations were
directed primarily against the yellow fever mosquito, and
incidentally against the other common species that inhabit rain-
water barrels. Against the Anopheles in the suburbs the same
kind of work was done as was done in Havana, with exception-
ally good results.

The same operations were carried on in the villages between
Panama and Colon. There are some twenty of these villages,
running from 500 to 3000 inhabitants each. Not a single in-

1 Howard, L. O., Bulletin 78, Bureau of Entomology, U. S. Department of Agri-
culture.

MOSQUITOES AND DISEASE 95

stance of failure has occurred in the disinfection of these small
towns, and the result of the whole work has been the apparent
elimination of yellow fever and the very great reduction of
malarial fever.

The remarkable character of these results can only be judged
accurately by comparative methods. It is well known that
during the French occupation there was an enormous mortality
among the European employees, and this was a vital factor in
the failure of the work.

Control by School Children. — That children can be of im-
mense service in freeing a city from mosquitoes as well as from
house flies (see Chap. VIII) is illustrated by certain events that
took place in San Antonio, Texas. Yellow fever appeared in
this city in November, 1903, and although its presence was
denied by the inhabitants, efforts were made by certain enlight-
ened people to eradicate it as soon as possible by destroying all
the mosquitoes. In this campaign the aid of the school children
was enlisted with excellent results.

The best recent literature on the subject of fighting mosquitoes
was procured and furnished to the teachers, and a circular letter
was sent to them outlining a proposed course and offering a cash
prize for the best model lesson on the subject. Teachers became
deeply interested. A crude aquarium, with mosquito eggs and
larve was kept in every schoolroom, where the pupils could
watch them develop, and large magnifying glasses were fur-
nished in order that they might study to better advantage.
The children were encouraged to make drawings on the black-
board of mosquitoes in all stages of development. Lessons were
given and compositions were written on the subject. Competi-
tive examinations were held, and groups of boys and girls were
sent out with the teachers on searching expeditions to find the
breeding places. Rivalry sprung up between the ten thousand
public school children of the city in the matter of finding and
reporting to the health office the greatest number of breeding
places found and breeding-places destroyed. Record was kept

96 PRACTICAL ZOOLOGY

on the blackboards in the schools for information as to the
progress of the competition, and great enthusiasm was stirred
up. In addition to these measures, a course of stereopticon
lectures was arranged, which the pupils attended in groups of
about one thousand.

The result of this work, it is pleasing to say, was a decided
diminution of mosquitoes in San Antonio. There was some
opposition from the people, but on the whole the movement was
very popular. One result of this work was that, whereas pre-
viously there had been from fifty to sixty deaths a year from ma-
laria, this mortality was reduced seventy-five per cent the first
year after the work was begun, and in the second year it was
entirely eliminated from the mortality records of San Antonio.

In organizing community work against mosquitoes, the school
children hereafter must be counted upon as a most important
factor. Almost every child is a born naturalist, and interest in
such things comes to children more readily than anything else
outside of the necessities of life. They are quick-witted, wonder-
fully quick-sighted, and as finders out of breeding places they
usually cannot be approached except by adults of special train-
ing. One of the first steps that a community should take is,
therefore, to arouse the interest of the children in the public
schools (Howard).

Mosquitoes and Other Diseases. — There are many other
tropical diseases caused by minute living things that are probably
transmitted by mosquitoes, although we have yet to learn how
guilty these insects really are. A great many scientists are now
employed in the study of these diseases and we may hope that
as a result of their studies the tropics in the near future will be
as healthful as any other part of the world. The cause of dengue
or breakbone fever is not known, although it is supposed to be a
germ similar to those present in malaria and _ yellow fever.
Whatever it is, it is known to be transmitted by mosquitoes.
Elephantiasis is a disease caused by minute worms (see Chap.
XX) which occur in vast numbers in the blood of human

MOSQUITOES AND DISEASE 97

beings, causing immense swellings of various parts of the body.
These parasitic worms are probably injected into the body of the
victim when an infected mosquito bites him.

REFERENCES
Malaria — Cause and Control, by W. B. Herms. — The Macmillan Co.,
N. Y. City.

The Mosquitoes of North and Central America and the West Indies, by
Howard, Dyar, and Knab.— Carnegie Institution of Washington.
Bulletins and Circulars published by the Bureau of Entomology, U. S. De-

partment of Agriculture.

CHAPTER X
OTHER INSECTS THAT TRANSMIT DISEASE GERMS

THE insects other than house flies and mosquitoes that trans-
mit disease germs are principally blood-sucking flies, fleas, bed-
bugs, and lice. The relations of many of these insects to disease
are very little known, but in a few years we may expect the jury
of scientists either to convict or acquit those now under indict-
ment.

Fleas and Bubonic Plague. — The connection between fleas
and bubonic plague is now well known. This disease is caused
by a very small bacterium which causes fever, glandular swellings,
and often death. Many epidemics are recorded in history; in
the sixth century about half of the people in the Roman Empire
died of it; in India from 1901 to 1904 it caused about two mil-
lion deaths; and in China, Egypt, South Africa, and in our own
seaports epidemics have occurred or have been threatened.
Careful studies of the plague have proved that the bacteria
causing it are chiefly carried from diseased rats to man by a kind
of flea which is now known as the plague flea.

Control of Plague in San Francisco. — In the neighborhood
of San Francisco the California ground squirrels have also be-
come diseased by plague germs that have been transferred to
them by rat fleas. The spread of the disease throughout North
America through the agency of ground squirrels, rats, and fleas
is thus made possible.

“ During the last few years San Francisco has been fighting
an outbreak of plague that in other days would have been
nothing less than a national calamity. But with modern

methods of handling it, based on knowing what it is, what causes
08

OTHER INSECTS THAT TRANSMIT DISEASE GERMS 99

it, and how it is spread, the authorities there have been able not
only to hold the disease in check, but practically to stamp it
out with the loss of comparatively few lives.

“A small army of men was employed, catching rats in every
quarter of the city. Dr. Rucker reports that fully a million rats
were slain in this campaign. Their breeding places were de-
stroyed by making cellars, woodshed, warehouses, etc., rat-
proof and removing all old rubbish. Garbage cans were installed
in all parts of the city, as it was required that all garbage be
stored where rats could not feed upon it, and altogether every
effort was made to make it as uncomfortable as possible for the
rats.

Fic. 58. — Sucking insects that carry disease germs.

A, tsetse fly, which carries the germs of sleeping sickness; B, stable fly ; C, bed-
* bug. (After Howard.)

“The marked success attending this work abundantly con-
firms the soundness of the theory upon which it was based, and
serves as another example of the way in which science is teaching
us how to prevent or control many of our most serious diseases.”
(Doane.)

Blood-sucking Flies and Disease. — Blood-sucking flies are
known to transmit the germs of sleeping sickness, and probably
carry those of infantile paralysis (polyomyelitis) and anthrax.
Sleeping sickness is prevalent in certain parts of tropical Africa.
It is caused by a minute protozoan parasite and is transmitted

I0O PRACTICAL ZOOLOGY

from one person to another by the tsetse fly (Fig. 58, A). In-
fantile paralysis is a disease that is often epidemic in this coun-
try. The results of recent investigations have proved that it
may be transmitted from a diseased monkey to a healthy one by
bites of the common stable fly, and it seems very probable that
these flies also transmit it from one human being to another.
The stable fly (Fig. 58, B) is frequently abundant around houses
and is often mistaken for the house fly; bites often credited to
the latter are really made by the stable fly, since the house fly
cannot pierce the skin (see page 76).

Anthrax is the most widely spread of all infectious diseases.
It occurs almost all over the world, and attacks man, horses,
rabbits, and other mammals, but especially cattle and sheep.
The bacillus (Fig. 48, D) is comparatively large, being about
ssyy Of an inch long. Anthrax is especially interesting, since it
was the first disease proved (by Pasteur and Koch) to be caused
by bacteria. Blood-sucking flies are probably concerned in the
transmission of the anthrax germs, since the bacilli often enter
the body in wounds and are found in the blood of most of the
infected animals. Vaccination according to the methods de-
vised by Pasteur in 1881 is employed for cattle and sheep in
infected districts with good results. In France alone, between
the years 1882 and 1907, 8,000,000 sheep and 1,300,coo cattle
were vaccinated.

Bedbug and Disease. — The guilt of the bedbug, so far as
the transmission of disease germs is concerned, has not been
fully determined. Bedbugs (Fig. 58, C) are thoroughly domes-
ticated, living only in human dwellings. During the day they
hide in cracks, but at night they sally forth to suck the blood of
any unfortunate being that they chance to find. Gasoline, cor-
rosive sublimate, or turpentine, if injected into their hiding
places, will kill them. Bedbugs are accused of transmitting the
germs of leprosy, Oriental sore, and the dumdum fever or kala-
azar of the tropics.

Sucking Lice and Disease. — The sucking lice that occasion-

OTHER INSECTS THAT TRANSMIT DISEASE GERMS 101

ally parasitize human beings (see p. 54) are, like the bedbug,
in an uncertain position. It is evident that their mode of life is
such as to make the transmission of germs by them an easy
matter. Recent reports seem to prove that body lice (Fig. 34,
D) are the only carriers of the germs of relapsing or recurrent
fever which occurs occasionally in America, but is prevalent in
Central Africa.
REFERENCES
Insects and Disease, by R. W. Doane. — Henry Holt and Co., N. Y. City.

Medical Entomology by Riley and Johannsen.— Comstock Pub. Co.,
Ithaca, N. Y.

CHAPTER XI

CLASSIFICATION IN GENERAL AND OF INSECTS IN
PARTICULAR

WHEN one has a large number of different kinds of objects be-
fore him, it is but natural for him to try to arrange them in some
orderly fashion. If a person unacquainted with insects were
given several hundred of them, he would have little difficulty
in separating them into groups of butterflies, bectles, flies, etc.,
which would, at least approximately, coincide with the groups
in which these insects are placed by scientists. What such a
person does is to pick out some characteristic that seems to be
general, such as the large, beautifully colored wings of the butter-
fly or the hard, sheathlike wings of the beetle.

Artificial Classification. — A study of the habitats of insects has
shown that (1) some live on the surface of the ground; (2) some
burrow in the ground; (3) some live in the waters of ponds
and streams; (4) some fly about in the air much of the time;
(5) and many live on or in the bodies of other animals. We can
classify these insects according to their habitats as terrestrial,
subterrestrial, aquatic, aérial, and parasitic, but a group col-
lected from any one habitat will exhibit among themselves a
great diversity in characteristics. This sort of classification is
called artificial.

Natural Classification. — A natural classification attempts to
place every animal in its proper place according to its kinship
with other kinds of animals. The grouping of insects employed
in the preceding chapters is artificial since, for example, under the
heading of insects of the household we mentioned among others

102

CLASSIFICATION 103

the meal worm (a beetle) and carpet beetle, the black and red ants,
the cheese skipper (a fly), house fly, and stable fly, and the
clothes moth. The adults of these insects would unhesitatingly
be placed with their proper relatives by any one, — the ants in
one group, the beetles in another, etc., but a very close examina-
tion is necessary in many cases before we can actually determine
the correct position of an animal with regard to other kinds of
animals.

General Knowledge of Principal Groups. — Thus far we have
discussed insects almost exclusively, although it has been neces-
sary for us to mention other animals, such as birds, horses, dogs,
cats,and man. That there is a very great difference between
insects and these other animals is quite obvious and even those
who have never studied the way animals are grouped are familiar
in a general way with the popular names applied to many of the
larger assemblages. Thus children speak of insects, worms,
fishes, reptiles, and birds without realizing the significance of
the terms.

Structure and Life Histories in Classification. — The error
is commonly made of calling anything that resembles an earth-
worm in general appearance a worm, but we have seen that the
young of many insects, that is, larvae, are wormlike. These
larve are commonly called worms, but of course are very far
removed from the earthworm in the scale of life, since they later
become highly organized insects, whereas the earthworm re-
mains a worm as long as it lives. A comparison between the
structure of the earthworm and the insect larva would reveal
many fundamental differences, and a study of their life histories
would quickly prove that the two are really very distant relatives.
This shows that we must be acquainted with both an animal’s
structure and its life history before we can be certain of its rela-
tions to other animals.

System of Classification Used by Scientists. — The system of
classification now in use was devised by the Swedish naturalist
Linneus (1707-1778). He divided the animal kingdom into a

I04 PRACTICAL ZOOLOGY

number of large groups called phyla. The animals in each phy-
lum were subdivided into groups called classes; the classes into
subgroups, the orders ; the orders into families ; the families into
genera; and the genera into species. Each species consists of
a group of closely similar individuals. By referring to animals
familiar to every one it will be possible to make the system of
classification used by scientists perfectly clear.

Horsre AS AN EXAMPLE OF SPECIES. — The common horse,
although represented by over sixty domesticated races, belongs
to a single species which is known to scientists as Equus caballus.
The term “ caballus” is used only for the common horse, but
the term Equus is also employed when writing of certain near
relatives of the horse, such as the zebra, Equus zebra.

Equus is known as the generic name, and the horse and zebra
are said to belong to the same genus. The horse and zebra, to-
gether with a number of other horselike animals, make up the
genus Equus. A genus may be defined as a group of similar
Species.

As in the case of the horse, every species is referred to in
scientific writings by two terms: the generic name comes first
and is written with a capital; the specific name second with a
small letter. These two terms are often followed by the name
of the scientist who first applied the name to any particular
animal,

The genus Equus, the extinct genus Protohippus, and several
other genera are grouped together into one family, the horse
family Equide.

This family and several others, including the family Tapiride,
which contains the tapirs, and the family Rhinocerotide, which
contains the rhinoceroses, belong to the order Perissodactyla.
All of the animals in this order have an odd number of toes, and
each toe bears a hoof.

The order Perissodactyla belongs with the order Rodentia
(gnawing animals, like the rabbit and mouse), the order Carniv-
ora (flesh-eating animals, such as the cat and dog), the order

CLASSIFICATION I05

Primates (monkeys, apes, and man), and a number of other
orders in one class, the class Mammalia. The members of this
class are called mammals, and all have certain characteristics
in common; among these are a covering of hair, and the
presence of milk glands from which the helpless young obtain
food.

The animals in the class Mammalia and in the classes contain-
ing the birds, reptiles, fish, and eels resemble one another in the
possession of a backbone, made up of a series of bones called
vertebrae, and are hence grouped together in the phylum Verte-
brata. ‘The vertebrates are the only animals that possess a back-
bone.

The rest of the animals in the animal kingdom are arranged in
a similar way and we may recognize ten phyla in all as indicated
on page 6.

The system described above may be applied to man as
follows :

George Washington was an individual; he belonged, with
other men, to the species sapiens of the genus Homo. This
genus, together with another of somewhat questionable relation-
ships, the extinct Pithecanthropus, constitutes the family Homin-
ide. The Hominide are included with ten other families of
monkey-like animals in the order Primates. Fifteen related
orders, of which the Primates form one, are placed in the class
Mammalia. The class Mammalia with four other classes make
up the phylum Vertebrata. The scientific name of man is writ-
ten Homo sapiens Linneus.

Reasons for Existence of Classification. — There are several
important reasons why a classification of animals exists. In the
first place it seems natural for us to group similar things to-
gether, and this has been done ever since the time of the Greek
naturalist Aristotle (384-322 B.c.) who gave us the first valuable
writings on animals. For example, we are all the time uncon-
sciously classifying human beings, grouping them into nations,
such as the English, French, German, etc., or into races, as the

106 PRACTICAL ZOOLOGY

white, black, red, etc., or, according to locality, into Eastern,
Northern, Southern, etc.

Besides this we are able by means of our system to learn the
name of an animal new to us; and if it is one that has never
before been named and recorded, we can soon learn this,
give it a name, and add it to the list. Furthermore, scientists
are at all times making detailed studies of the animals already
known and are constantly rearranging them so as to establish
their kinship.

Value of Classification as Mental Training. — The study of
classification if carried out in the laboratory will influence one’s
entire life. It will teach one to make observations and com-
parisons and to do so with accuracy. It will also teach the value
of arranging facts systematically — a lesson which, once learned
regarding animals, will be applied to other things throughout
life.

Necessity of Scientific Terms. — Many people do not under-
stand why scientific terms are necessary, since our common ani-
mals are known by plain English names, such as horse and robin.
Science, however, does not recognize the boundaries of nations
but is world-wide, and we must be able to understand the writings
of the Germans, French, and others, as well as those in our own
language. For this reason scientific terms are the same all over
the world. They are Latin in form, and derived chiefly from
the Latin and Greek.

In many cases the scientific term is simply the Latin name of
the animal ; for example, the American toad is known everywhere
as Bufo americanus, bufo meaning toad in Latin, and ameri-
canus, American. Some animals are named because of their
geographical distribution, like the California sea lion, Zalophus
californianus, which lives in that region. Or the name may de-
scribe the animal in some way. The rufus in the wildcat’s
name, Lynx rufus, is descriptive of the animal’s rufus color,
and the sapiens in the name of man, Homo sapiens, is the Latin
word meaning wise and describes his mental condition. And

CLASSIFICATION; 107

finally scientists often name species of animals after some one
who has become an authority in the subject; for example, one
of our common hawks was named Buteo swainsoni in honor of
the bird student Swainson.

Classification of Insects. — It would seem as though the value
of our system of classification could be thoroughly tested by
means of the insects, since this group of about four hundred
thousand known species of animals constitutes a single class,
the Insecta. The class Insecta is included in the phylum Arthro-
poda along with three other classes, the Crustacea (crayfish,
lobster, etc.), Myriapoda (thousand-legged worms, etc.), and
Arachnida (spiders, mites, etc.). These classes are also larger
than most other classes in the animal kingdom, and hence the
arrangement of the members of this one phylum Arthropoda
might be expected to be rather difficult. But while it is true
that we still do not know exactly where a few of the arthropods
belong, most of them fit into their places without difficulty.

CHARACTERISTICS OF THE CLass INSEcTA.— The members of
the class Insecta are characterized by the presence of one pair of
antenne, three pairs of legs, and usually wings. The crayfish is
not an insect, for it has two pairs of antenne, five pairs of legs,
and no wings. The spiders are not insects since they have four
pairs of legs and no antenne, and the thousand-legged worms
are not insects because they have a great many pairs of legs and
no wings. All of these animals belong to the phylum Arthro-
poda, however, because they have an outer covering or exoskele-
ton of chitin instead of a backbone, have a bedy divided more
or less distinctly into similar parts (segments) arranged in a
linear series, and possess paired, jointed appendages (legs, etc.)
on some or all of the segments.

ORDERS OF INsEcts. — Insects have been divided into eight
orders according to (1) the presence or absence of wings, and
their number and structure when present, (2) the structure of
the mouth parts (biting or sucking), and (3) the character of
the metamorphosis. Although some of the orders would have

108 PRACTICAL ZOOLOGY

to be divided into two or more if we were going to study insects
in detail, the main orders of insects with their characteristics,
are as follows.

Order 1. Aprera. — Fish Moths and Springtails.

Primitive insects without wings or rudiments of wings; biting
mouth parts; and no metamorphosis.

The fish moth or silver fish is the commonest species (see p. 57,
Fig. 35, A). The snow flea is sometimes a pest in maple sugar
camps, since large numbers often get into the sap.

Order 2. ORTHOPTERA. — Grasshoppers, Crickets, etc.

Insects with four wings; the fore wings straight and leathery;
the hind wings folded like a fan; biting mouth parts; metamor-
phosis direct.

The principal families of the Orthoptera are the (1) cock-
roaches, (2) mantids, (3) walking sticks, (4) grasshoppers or
locusts with short antenne,(5) grasshoppers with long antenne;
and (6) crickets. :

Order 3. NEUROPTERA. — May Flies, Dragon Flies, etc.

Insects with two pairs of membranous wings; biting mouth
parts; metamorphosis direct or indirect.

The group of insects included here are the May flies, dragon
flies, stone flies, caddice flies, lacewing flies, and white ants or
termites.

Order 4. Hemiptera. — Chinch Bugs, Scale Insects, ete.

Insects with four wings, or degenerate and without any wings;
the fore wings of some thickened at the base; sucking mouth
parts; metamorphosis direct. .

These are the true bugs. The wingless species are the sucking
lice, bedbugs, and many scale insects. The winged species in-
clude the cicadas, tree hoppers, spittle insects, water striders,
chinch bugs, squash bugs, and stink bugs.

Order 5. LrpipopTera. — Butterflies, Skippers, and Moths.

Insects with four membranous wings covered with scales;
usually sucking mouth parts; metamorphosis indirect.

These insects are noted for their brilliant colors. The butter-

CLASSIFICATION 10g

flies and skippers are active during the day, that is, they are
diurnal, and the moths at night (nocturnal). The members of
the three main groups can be distinguished by their antenne;
those of the butterflies end in a knob, of the skippers in a knob
with a recurved point, and of the moths without the knob but
often with bristles on the sides.

Order 6. Drprera. — House Flies, Mosquitoes, etc.

Insects with the two fore wings present, but the two hind
wings represented by knobs; sucking mouth parts; metamor-
phosis indirect.

Some of the Diptera are degenerate and without wings, such
as the bird lice, fleas, and sheep tick; the winged species include
the house flies, mosquitoes, crane flies, midges, gnats, horse
flies, botflies, and flower flies.

Order 7. COLEOPTERA. — Beetles.

Insects with four wings, the fore wings (called elytra) sheath-
like and covering the membranous hind wings; biting mouth
parts; metamorphosis indirect.

This is a very large order in number of species. Some of the
common families are the tiger beetles, ground beetles, whirligig
beetles, burying beetles, click beetles, scarabid beetles, June
bugs, potato beetles, ladybird beetles, bark beetles, weevils,
meal-worm beetles, Spanish flies, and fireflies.

Order 8. Hymenoptera. — Ants, Bees, Wasps, etc.

Insects with four membranous wings; mouth parts both for
biting and sucking; sting often present; metamorphosis in-
direct.

This is another very large order. Some of the principal fam-
ilies are the ants, bees, wasps, sawflies, gallflies, ichneumon
flies, and chalcid flies.

It is evident from the above list that in many cases one could
not tell from the common names where the insects belong. For
example, the true flies are the Diptera, but some of the members
of almost every other order are called flies, such as the May flies,
butterflies, fireflies, and sawflies. To most people an insect

I1o PRACTICAL ZOOLOGY

is a bug, but only those belonging to the order Henne are
true bugs.
REFERENCES
Entomology, by J. H. Comstock. — Ithaca, N. Y.
American Insects, by V. H. Kellogg. — Henry Holt and Co., N. Y. City.

Elementary Entomology, by Sanderson and paeESOn. — Ginn and Co.,
Boston.

CHAPTER XII
SPIDERS AND OTHER ARACHNIDS

Where Spiders Live. — Spiders are considered “‘ insects ”’ by
many people, but they can be distinguished easily from them by
the presence of four pairs of legs instead of only three, and by
the union of the head and thorax into one piece, called the ceph-
alothorax. There are probably four or five hundred different
kinds of spiders living in the neighborhood of any city of the
United States. They are to be found in all sorts of places.
Many species live almost entirely around houses, making their
webs in the corners of the rooms, in the cellars, or outside in
window corners, crevices in walls, etc. Other species make
’ their homes under stones and sticks lying on the ground. Plants
of all kinds are alive with spiders, some preferring grass, and
others bushes or trees.

Spiders with and without Webs. — We always associate
spiders with spider webs, but a great many species which are
called hunting spiders do not build webs. They have nests,
but run about catching insects wherever they chance to find them
or lie in some place of concealment until insects come within
their reach.

Types of Webs. — The cobweb spiders build webs for catch-
ing insects, and live either in the web or in a nest close to it.
Cobwebs are of four principal kinds: —

1. The flat webs are closely woven of long threads crossed by
finer ones in all directions, and connected with a tubular nest
where the spider hides, and from which it runs out on the upper
side of the web after insects that may fall upon it.

2. The netlike webs are made of smooth threads in large

meshes, sometimes in a flat or curved sheet held out by threads
if IIt

nigy 6 PRACTICAL ZOOLOGY

Tic. 59.— Photograph of a spider at the center of its web. (After Burlend.)

in all directions. The spider lives on the underside, back down-
ward.
3. The round webs are made of threads radiating from a

common center and crossed by circular loops and spirals, part of
which are adhesive (Fig. 59).

SPIDERS AND OTHER ARACHNIDS 113

4. The webs of certain species are composed in part of loose
bands of silk (Emerton).

How Webs are Built. — An orb web, such as that shown in Fig-
ure 59, is spun in the following manner: A thread is stretched
across the space selected for the web; then from a point on
this thread other threads are drawn out and attached in radiat-
ing lines. These threads all become dry and smooth. On this
foundation a spiral is spun of sticky thread (Fig. 61, D). The

Fic. 60.— Internal anatomy of a spider.

1, mouth; 2, sucking stomach; 3, ducts of liver; 4, so-called malpighian
tubules; 5, stercoral pocket; 6, anus; 7, dorsal muscle of sucking stomach;
8, cecal prolongation of stomach; 9, cerebral ganglion giving off nerves to eyes;
10, subcesophageal ganglionic mass; 11, heart with three lateral openings or
ostia; 12, lung sac; 13, ovary; 14, 15, 16, 17, silk glands; 18, spinnerets;
19, distal joint of chelicera; 20, poison gland; 21, eye; 22, pericardium; 23,
vessel bringing blood from lung sac to pericardium; 24, artery. (From the
Cambridge Natural History.)

spider stands in the center of the web or retires to a nest at one
side and waits for an insect to become entangled in the sticky
thread; it then rushes out and spins threads about its prey until
all struggles cease.

Spinning Organs. — The spinning organs of spiders, called
spinnerets, are three pairs of projections near the posterior end
of the body on the ventral surface (Fig. 61, A). The spinnerets
are pierced by hundreds of microscopic tubes through which a
fluid passes from the silk glands (Fig. 60, 14, 15, 16, 17), which

I

114 PRACTICAL ZOOLOGY

hardens in the air, forming athread. The silk glands are situated
in the abdomen and cause the large size of this part of the body.

How Insects are Captured. — The webs of the cobweb spiders
catch many small animals, mostly insects, but the spider itself
never seems to become entangled in its own web. This is prob-
ably because of the peculiar structure of the foot (Fig. 61, B).
The hunting spiders live principally on insects. The struggles
of the captured animals are soon stopped by a poisonous secre-
tion which is injected into them. This poison is formed in
poison glands situated in the head (Fig. 60, 20),and forced out
through the first pair of appendages, the chelicerz (Fig. 60, 79).
When the captured insect has become quiet, the spiders suck
out the juices into the alimentary canal by means of a sucking
stomach (Fig. 60, 2).

Sense Organs. — Spiders are, of course, aided by sense organs
in obtaining their food. Hairs that are sensitive to touch are
generally distributed over the body. The eyes, however, are the
principal organs of sense. There are usually eight (Fig. 61, C),
and they differ in size and arrangement in different species.
Spiders apparently can see objects distinctly only at a distance
of four or five inches.

Respiration. — Since spiders are terrestrial animals, they
must be able to breathe in the air. For this purpose they are
supplied with trachez similar to those of insects (see p. 15),
but in addition they possess book lungs which are present only
inspiders. The book lungs (Fig. 60, 12), of which there are usu-
ally two, are sacs, each containing generally from fifteen to
twenty leaf-like horizontal shelves through which the blood
circulates. Air, entering through the external openings, is thus
brought into close relationship with the blood.

Reproduction. — The eggs of spiders are inclosed in a silk
cocoon which varies much in shape and color in different species.
Some spiders hang it in the web, others attach it to plants or
stones, and others carry it with them, either in the mandibles
or attached to the spinnerets. The young remain in the cocoon

SPIDERS AND OTHER ARACHNIDS TI5

until they are able to run about, and after coming out of the
cocoon keep together for a short time, sometimes in a web which
they make in common, sometimes in a web made by the mother,
and in some species on
the mother’s back, but
they soon scatter and
hunt their own food or
make cobwebs, accord-
ing to the habits of the
species (Emerton).

Spiders are among
the most interesting of
all animals because
of their remarkable
methods of building
their webs, of dis-
tributing themselves,
and of capturing their
prey.

Aérial Spiders. —
On sunny days in au-

tumn large numbers 3 ,
& A, ventral view of posterior end of abdomen
of fine threads, the showing three pairs of spinnerets (is, m.s., and s.s.).

so-called, gossamer e aa ed oe ae and jaws (3
threads, may be seen and 4).

floating about over ee a thread from a spider’s web. (After Warbur-
fields and meadows.

On some of these threads, if we examine them, we shall
find a small (young) spider. This aérial vehicle is of the
creature’s own construction, having been produced in the
following manner: Having ascended some elevated spot, such
as a clod of earth, the spider spins a few short threads, which
are fastened to the ground. These it grasps in order to ob-
tain a firm hold. Next it once more presses the silk glands
against the supporting surface, and elevates its abdomen. In

Fic. 61.— Parts of a spider’s body.

116 PRACTICAL ZOOLOGY

this way a thread is formed, which, soon being seized by the
wind, is drawn out longer and longer, blown hither and thither,
and thrown into tangles, so that finally a small raft is produced.
At last the wind lifts both the raft and its maker up into the air,
and the aérial journey begins. Perchance the little ship will be
stranded — agreeably to the wish of its navigator — in some spot

Fic. 62.— A, crab-spider ; B, jumping-spider; C, young spider preparing for an
aérial voyage ; D, house-spider. (After Emerton.)

where the latter may enjoy its winter rest in security, in order
in the following year to spread its species (Fig. 62, C) (Schmeil).

Water Spider. — The water spider of Europe lives under
water. Its abdomen has a velvety covering of hairs, and just
as a layer of air remains adherent to a velvet rag dipped in water,
so this spider always carries a large silvery air bubble down with
it below the water. There it spins a dwelling not unlike a small

SPIDERS AND OTHER ARACHNTDS 117

diving bell, which it anchors by threads to water plants, and fills
with air in the aforesaid manner. Thus the animal lives in air
in the midst of the water! (Schmeil).

Trapdoor Spider. — The nests of the trapdoor spider, often
seen in collections of curios, usually come from California. The
spider which makes the nest is blackish brown in color and meas-
ures a little over an inch in length. A cylindrical tunnel is dug
in the ground, the walls of which are made firm by gluelike

Fic. 63.— A, tarantula; B, trapdoor spider. (From Coleman.)

saliva, and then lined with silk (Fig. 63, B). The entrance to
this tunnel is covered by a hinged door. From this place of con-
cealment the spider ventures out after its prey, returning at the
first sign of danger. The topof the door resembles the surround-
ing earth, so that the nests are hard to find. If the spider is dis-
covered, it holds the door shut from within and is dislodged with
difficulty.

Tarantulas. — Certain large, hairy spiders that live in warm
parts of the world are commonly called tarantulas (Fig. 63, A).
These spiders are supposed to be very poisonous, but most of
the stories told about them are not true, since they very seldom
bite, and if they do, the injury is probably no worse than the sting
of a bee.

118 PRACTICAL ZOOLOGY

Spider Bites. — In the North there is no danger at all from
spider bites. Spiders if captured are so busy trying to escape
that they rarely attempt to bite. They use poison to kill in-
sects, but scientists have allowed themselves to be bitten by all
kinds of spiders without any harmful results whatever. Evi-
dently a dose of poison that will paralyze an insect has no effect

~

Fic. 64.— A harvestman. (From Sedgwick.)

upon a man. It is therefore perfectly safe to handle any living
spiders if you so desire.

Harvestmen. — The harvestmen or daddy longlegs (Fig. 64)
resemble spiders in many ways. They possess small bodies and
very long, slender legs. During the daytime they remain quietly
in some place of concealment, but at night they venture forth in
search of insects whose juices they suck just as do the spiders.

Scorpions. — Scorpions are rapacious arachnids measuring
from half an inch to eight inches in length (Fig. 65). They live
in tropical and subtropical regions, hiding in crevices or in pits
in the sand during the daytime, but running about actively at
night. They capture insects and spiders with their pinchers,
tear them apart with their chelicere, and devour the pieces.
Larger animals are paralyzed by the sting on the end of the tail.
This sting does not serve as a weapon of defense unless the
scorpion is hard pressed, and is not used, as is often stated,
to sting itself to death, since the poison has no effect upon
its own body.

SPIDERS AND OTHER ARACHNIDS TIg

Mites and Ticks. — The mites and ticks are small arachnids
living on vegetation, in the water, or as parasites on men and
other animals. They will be more fully discussed in the next
chapter.

King Crab. — The king or horseshoe crab (Fig. 66) is a pecul-
iar arachnid that lives in the sea and was for a long time con-

SI Pedipalp
” Lateral eyes

Metasome

x
aculeus. VA “‘vestele
a fa J

Fic. 65. — Scorpion: A, dorsal view; B, ventral view. (After Kraepelin.)

sidered a crustacean. The head and thorax form a large horse-
shoe-shaped piece and the tail is a single long spine. The king
crab lives in burrows in the sand and feeds on worms, snails, and
other small marine animals.

Characteristics and Classification of Arachnida. — The mem-
bers of the class Arachnida differ markedly from one another,

120 PRACTICAL ZOOLOGY

but agree in several important respects: (1) they have no an-
tenne; (2) there are no true jaws; (3) the first pair of append-
ages are nippers, termed chelicere; and (4) the body can usu-

Fic. 66.— The king or horseshoe crab: A, dorsal view; B, ventral view. (From
Shipley and MacBride.)

ally be divided into an anterior part, the cephalothorax, and a
posterior part, the abdomen.

Of the twelve orders of Arachnida only four need be mentioned,
since they contain most of the living species.

Order 1. ARANEIDA. — Spiders.

Order 2. SCORPIONIDEA. — Scorpions.

Order 3. PHALANGIDEA. — Harvestmen, or Daddy Long-
legs.

Order 4. ACARINA. — Mites and Ticks.

REFERENCES
The Spider Book, by J. H. Comstock. — Doubleday Page and Co., N. Y.
City.
Common Spiders, by J. H. Emerton. — Ginn and Co., Boston.

CHAPTER XIII
THE RELATIONS OF ARACHNIDS TO MAN

ARACHNIDS are indirectly of importance to man as destroyers
of injurious insects and because of their injuries to vegetation,
but principally because some of them transmit disease germs
from one animal to another, very much as do the house fly, mos-
quitoes, and certain other insects. (See Chapters VIII, IX,
and X.)

Arachnids Destroy Insects. — Spiders, harvestmen, and -
scorpions are all carnivorous and feed principally upon insects.
The number of injurious insects they destroy annually can hardly
be estimated, but it must be very large, considering the abun-
dance and voraciousness of spiders.

Spider Silk. — The silk with which spiders build their nests
and webs is of excellent quality but difficult to obtain. It must
be collected from individual spiders in captivity, and each spider
yields only about an ounce. The silk is, nevertheless, sometimes
woven into cloth. More important than this, however, is the
use of the delicate silk threads as cross hairs in telescopes.

Mites and Ticks. — The mites and ticks are the arachnids
that act as parasites on man and domestic animals and sometimes
distribute disease germs. Those discussed in the following para-
graphs are the tick which causes Texas fever in cattle, the ticks
and mites that attack chickens, the mites that cause mange and
scab of domestic animals, and the spotted-fever tick, follicle mite,
itch mite, and chiggers that parasitize man.

Texas-fever Tick. The Texas-fever tick transmits a pro-
tozoan parasite, named Piroplasma bigeminum, from sick cattle

to healthy cattle in the South. How serious this disease is may
121

122 PRACTICAL ZOOLOGY

be judged from the fact that it causes an annual loss of about
sixty million dollars to the people living in the fever district.
The relations between the tick and Texas fever were definitely
established by Theobald Smith of the Bureau of Animal Industry,
U.S. Department of Agriculture, in 1889. The protozoan para-
sites occur in the blood corpuscles of sick cattle. The ticks suck
the blood of these cattle and of course take the parasites into

Fic. 67. — Texas-fever tick.

A, adult female ready to lay its eggs.
B, adult female and egg mass. (After Graybill.)

their alimentary canals. When completely gorged with blood,
they drop to the ground ready to lay their eggs. The parasites
do not remain in the alimentary canal of the tick, but penetrate
into other regions, including the reproductive organs. They are
thus present in the eggs laid by the tick.

Each female tick deposits about 2000 eggs on the ground
(Fig. 67). The young or “ seed ticks,” which hatch from these
eggs in a few weeks, are parasitized, since the eggs from which
they developed contained parasites. They are about 45 of an
inch long and have only three pairs of legs. When cattle brush

THE RELATIONS OF ARACHNIDS TO MAN 123
FIELD No.2 FIELD No.3 FIELO No. ¢
CORN, COTTON OATS,
COWPEAS. FOLLOWED BY COWPEAS,
CRIMSON CLOVER VETCH BERMUDA,
BUR CLOVER OR RYE. BUR CLOVER.
—_}—_> —_+-—_>
WHEN FEED BECOMES FEBR./5, 2 BECOMES THE NEW
SHORT MOVE THE HERD| MOVE THE HERD 70 PASTURE.
FROM THIS FIELD TO FIELD No.F
FIELD No.3
f HOUSE
| FIELD No.1
PASTURE.

OCT. 1S, MOVE HEROD 70 FIELD No. 2
PLANT /N OATS ANDO FOLLOW WITH COWPEAS.

Fic. 68. — Plan which will eradicate the Texas-fever tick from pastures.

Graybill.)

(After

against the grass blades or weeds to which the young ticks are
clinging, the ticks fasten themselves to the bodies of the animals
and begin to suck their blood. During this process parasites
from the tick’s body are transferred to the blood of the cattle.

124 PRACTICAL ZOOLOGY

In this way the disease germs are transmitted from one animal
to another.

The control of the Texas-fever tick is very simple. The adult
ticks die after laying their eggs, and the young die if they do not
gain access to cattle within a few months. A pasture may thus
be freed from ticks if left vacant for a few months (Fig. 68).
Ticks may also be removed from cattle by dipping the animals
in vats containing substances such as crude petroleum or arseni-
cal mixtures which kill the ticks.

Chicken Mites. — Poultry in this country may be attacked by
chicken mites and fowl ticks. The mites (Fig. 69, A) are about

Fic. 69. — Arachnida parasitic on domestic animals.

A, chicken mite; B, fowl tick; C, scab mite. (After Salmon.)

zy Of an inch long, and red in color when filled with blood, but
at other times gray. They suck the blood of the poultry usually
at night and hide in crevices during the daytime. A thorough
cleansing of the chicken house and an application of a twenty
per cent kerosene emulsion will destroy most of the mites. In
many parts of the country the chicken mite is considered the
most serious poultry pest.

Fowl Ticks. — The fowl ticks (Fig. 69, B) are also a serious
pest in the warmer parts of this country. They resemble the
chicken mite in shape, but are almost 4 of an inch in length and

THE RELATIONS OF ARACHNIDS TO MAN 125

of a brownish or bluish-black color. Since they are principally
active at night, the fowls may escape them by resting on perches
hung from the ceiling with wires or iron rods.

Mites which Cause Scab and Mange. — Certain mites (Fig.
69, C) cause diseases known as scab or mange on sheep, horses,
dogs, and other animals. The sheep scab mite is the most im-
portant and must be fought instantly wherever sheep are reared.
The scabs are caused by the working of the mites in the skin

Fic. 70.—A sheep injured by the scab mite. (From Farmers’ Bulletin.)

(Fig. 70). These mites may be killed by dipping the sheep in
the same manner as that suggested for eradicating the sheep
tick (see p. 54).

Itch Mite. — The mites that attack man are comparatively
unimportant. The itch mite (Fig. 71, B ) is very closely related
to the sheep scab mite. It is a minute, whitish mite which lives
in the skin and causes intense itching. Cleanliness will prevent
infection, and sulphur ointment will eradicate the ticks.

Harvest Mites or Chiggers. — The harvest mites or chiggers
(Fig. 71, A) lie in wait in the grass or on shrubs until some luck-

126 PRACTICAL ZOOLOGY

less man or other animal comes along to which it can attach itself.
It burrows under the skin, causing itching and sores. Sulphur
ointment is the best remedy.

Face Mites. — Face or follicle mites (Fig. 71, C) are rather
long, slender arachnids that live in the sweat glands or hair folli-
cles in the skin of
man and some other
animals. They are
supposed to cause
the formation of
blackheads. That
these mites may have
something to do with
the spread of leprosy
and the origin of
cancer has also been
suggested.

Spotted-fever Tick.
— The most serious
disease of man that
is spread by ticks
in this country is
spotted fever. This
fever occurs in Idaho

and Montana and is
Fic. 71. — Arachnida parasitic on man. suppose d to be

A, harvest mite or chigger ; B, itch mite; C, fol- caused by a minute
licle mite. (From Sedgwick.) :
protozoan parasite.
The tick transmits these parasites from one animal to another
when it bites.

“Red Spiders ”’ on Plants. — In several cases plants are badly
injured by mites. The “red spiders” frequently become so
numerous in greenhouses, and sometimes outside, that the
plants whose juices they suck are seriously damaged. These
mites are very resistant to fumigation, but may be destroyed by

THE RELATIONS OF ARACHNIDS TO MAN 127

spraying the under surface of the leaves with a mixture of one
ounce of flowers of sulphur to one gallon of water.

Gall Mites. — Certain mites that resemble the follicle mites
in appearance cause a common disease of the pear and apple
called pear-leaf blister, and are known as gall mites.

REFERENCES

Bulletins and Circulars published by the Bureau of Entomology and the
Bureau of Animal Industry, U. S. Department of Agriculture.

CHAPTER XIV
THE MYRIAPODA OR CENTIPEDES AND MILLIPEDES

Millipedes. — The myriapods are terrestrial arthropods
commonly known as centipedes and millipedes or wireworms.
The body of a millipede is subcylindrical, and consists of from
about twenty-five to more than one hundred segments, accord-
ing to the species. Almost every segment bears two pairs of

Fic. oe salinede. (After Koch.)

appendages (Fig. 72), and has probably arisen by the fusion of
two segments. The mouth parts are a pair of mandibles and a
pair of maxillee. One pair of antenn and cither simple or aggre-
gated eyes are usually present. The breathing tubes (trachee)
arise in tufts from pouches which open just in front of the legs.

The millipedes move very slowly, in spite of their numerous
legs. Some of them are able to roll themselves into a spiral or
ball. They live in dark, moist places and feed principally on
vegetable substances.

Centipedes. —- The body of a centipede is flattened dorso-
ventrally, and consists of from fifteen to over one hundred and
fifty segments, which bear each one pair of legs. Centipedes
are swift-moving creatures. Many of them live under the bark
of logs or under stones (Fig. 73). The poisonous centipedes of

128

THE MYRIAPODA OR CENTIPEDES AND MILLIPEDES 129

tropical countries may reach a foot in length, and their bite is
painful and even dangerous to man.

Fic. 73.— A group of animals that live under bark. At the right a centipede.
At the left a pill bug, a sow bug, and a snail. (After Davenport.)

Characteristics and Classification. — The chief distinguishing
characteristics of the Myriapoda are: (1) a distinct head with
one pair of tentacles and one pair of mandibles, (2) numerous
body segments bearing similar leglike appendages, (3) trachee,
(4) excretory organs (malpighian tubules) opening into the in-
testine.

The two principal orders are as follows: —

Order 1. Drpropopa. — Millipedes.

Order 2. CuHILopopa. — Centipedes.

CHAPTER XV
THE CRAYFISH

THE crayfish is a typical member of the class Crustacea of the
phylum Arthropoda. It is large enough for study and easily
obtained for laboratory use. Crayfishes inhabit fresh-water
lakes, ponds, and streams, and although those in one part of the
country may difler slightly from those in other localities, the dif-
ferences are of minor importance, and one description will fit
them all. Near the seacoast the lobster is often available for
study. Lobsters are larger, but in most other respects resemble
the crayfishes.

Habitat. — The crayfish is usually found concealed under
rocks or logs at the bottom of ponds and streams. Here it lies
with its head toward the entrance to its hiding place. When
crawling about or swimming in the open water, its hard shell
helps protect it from fish, while its color, which resembles the
bottom, tends to make its detection difficult. Crayfishes may
be captured easily by hand, with a net, or by fishing for them
with a string baited with a piece of meat. They thrive in an
aquarium, and their entire life history may be observed in the
laboratory. The yearly decrease in the number of lobsters
available for food, and the steadily increasing demand for cray-
fishes, will undoubtedly soon make it worth while to raise the
latter for market.

Means of Protection. — The crayfish is protected from its
enemies in several ways. The tendency to lie concealed in a
crevice during the day and to feed only at night protects it from
certain animals like the kingfisher which might otherwise find it.

130

THE CRAYFISH I31I

EXOSKELETON. — The shell or exoskeleton is a sort of armor
encasing the body. As in the insect this consists of the sub-
stance called chitin, but is made stronger by the addition of cal-
careous salts. Crayfishes do not thrive well in water that does
not contain this mineral matter. From time to time the exo-
skeleton is shed to allow the growing body to expand. The new
shell is at first soft and the animal tries to hide until it becomes
hard. The body, like that of the insect, would be very unwieldy
if joints were not present (Fig. 74). In these joints the chitin
is thin and flexible. The two principal parts of the body differ

Abdomen Cenhalothorax Eye

Carapace :
ervical groove | Rostrum

Pleonods
(Swim merets)

Cheliped
(First leg)

Walking leqs

Fic. 74. — External anatomy of a lobster. (After Calman.)

in their flexibility; the foremost or anterior portion corresponds
to the head and thorax of the insect combined, and is named the
cephalothorax. A furrow, the cervical groove, indicates where
these two parts are united.

Cotor. — The color of the crayfish is likewise a means of
protection, since it closely matches the bottom of the body of
water in which the animal lives. It is in the shell and is formed
by green, brown, blue, and red pigments; the color of the body
depends upon which color is present in the greatest quantity.
When cooked, these pigments all turn red and the whole body
becomes “‘ as red as a boiled lobster.”

PRACTICAL ZOOLOGY

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of the state of their surroundings by their

When

organs.
they are hiding, the antenne are usually protruded and waved

nse

se

There are two pairs of these organs; the first

back and forth.

THE CRAYFISH 133

pair, which are called antennules (Fig. 75, 1), consist each of
two many-jointed filaments and act as organs of touch, and
smell or taste. In the base of each antennule is a cavity con-
taining a calcareous particle; this structure, the statocyst, is an
organ of equilibrium, enabling the animal to maintain an upright
position in the water.

Each antenna of the second pair (Fig. 75, 2) is a much longer
jointed filament, which serves both as a tactile organ and for
detecting changes in the chemical constitution of the water.

Enemies may also be located by means of the two compound
eyes (Fig. 75, 28) which are placed on stalks and can be moved
in all directions. They resemble in structure those of the in-
sects. The crayfish uses them to locate the insect larve, snails,
small fish, tadpoles, and other small moving animals that it uses
as food.

Locomotion. — Ordinarily the crayfish creeps along upon its
stiltlike legs. There are five pairs of these, but the first pair,
the pinchers (Fig. 75, 9), are seldom used to walk with, being
held in readiness as weapons of offense and defense. When
alarmed, the crayfish walks backwards, and if it becomes neces-
sary for it to escape quickly, it bends its flexible, scoop-shaped ab-
domen underneath the body and thus .swims backward very
rapidly in jerks. At the end of the abdomen are two fin-shaped
appendages which, like blunt oars, aid in propelling the animal
when the abdomen is bent forward under the body. The vital
organs of the crayfish are mostly in the cephalothorax, the ab-
domen being filled with the muscles used in swimming.

Food and Digestion. — The food that the crayfish needs to
keep its body going and growing consists by preference of small
living animals, but these may be flavored with pieces of plants
and other animal and vegetable substances to be found in quiet
waters. The large pinchers are used to hold and cut the food
into pieces, and the small pinchers on the second and third
pairs of legs (Fig. 75, 0 and rr) carry the pieces to the mouth.
Here the six pairs of mouth parts work together, the two pairs of

134 PRACTICAL ZOOLOGY

maxilla or auxiliary jaws and maxillipeds or foot jaws holding
the food while it is being crushed by the true jaws or mandibles
(Fig. 75, 3).

The food is not thoroughly ground up, however, until it has
passed through the cesophagus (Fig. 75, 20) into the stomach
(Fig. 75, 27). Here it encounters a number of tooth-like
structures which are moved by powerful muscles and form
the gastric mill. After being ground up in the gastric mill the
food is mixed with digestive juices poured into the stomach by
two digestive glands.

Absorption and Circulation. — The digested food is absorbed
by the intestinal walls and passes into the blood surrounding the
intestine; and the undigested food matter is cast out through the
anal opening (Fig. 75, 6). The blood into which the digested
food passes resembles that of insects (see p. 14), but besides
transporting food and waste products, it must also carry
oxygen and carbon dioxide, as does human blood. There is a
well-developed heart (Fig. 75, 29) which pumps blood into six
arteries leading to various parts of the body. As in insects,
the body cavity in which the vital organs lie is filled with blood
which passes out of the ends of the arteries. Circulation is com-
pleted by the entrance of the blood into the heart again.

Respiration. — The crayfish breathes very differently from
insects. It is a typical aquatic animal, and its respiratory sys-
tem consists of gills resembling those of a fish. These gills or
branchiz are attached to the bases of the legs and lie within
the branchial chambers. These chambers are formed by an ex-
tension of the exoskeleton on each side of the thorax, which pro-
tects the delicate filamentous gills from injury. A constant
stream of fresh water is forced through these chambers from be-
hind forward by the movements of the oarlike part of the second
maxillz. The gill filaments are supplied with circulating blood
which takes up some of the oxygen that is mixed with the water
and gives off carbon dioxide to the water.

Reproduction. — Often crayfishes are caught which have

THE CRAYFISH 135

bunches of eggs fastened to the appendages beneath the abdo-
men. These eggs or “ berries” are laid during the month of
April, and become attached to the abdominal appendages (the
swimmerets) by a sticky secretion. They are carried about
and thus protected by the mother until they hatch; then the
young still cling to their parent for about two weeks, after which
they lead a separate existence. The life of a crayfish extends
over aperiod of about three years. Many crayfishes are de-
stroyed by man, by otters and minks, by fish, and by king-
fishers, but the eggs and young are well protected, the continued
existence of the race thus being assured.

Fic. 76. — Cotton field damaged by crayfishes after three plantings. (After
Fisher.)

Relations to Man. — Crayfishes, as, mentioned above, may
sometimes be “‘ farmed” in order to supply the demand for food
which cannot be satisfied by the lobster industry. At the pres-
ent time, however, they are of very little value from this stand-

point.

136 PRACTICAL ZOOLOGY

The injuries done by crayfishes take place in rather restricted
localities. Earthen dams, dikes, and fills are sometimes harmed
by their burrows, and in the Houston clay lands of Mississippi
and Alabama certain areas are so badly infested by burrowing
crayfishes that the raising of crops with profit is impossible.
The area damaged by these crayfishes is about one thousand
square miles. In some places there are over ten thousand of
their holes per acre. Cotton and corn plants are cut away by
the animals and taken into their burrows to be used as food
(Fig. 76).

The most practical and economical means of coping with the
crayfish problem is to combine poisoning with killing the crus-
taceans by mechanical means. During rainy weather and at
twilight in the spring after the crayfish become active, the area
to be planted with cotton or corn should be visited frequently,
and as many as possible of the crayfish killed before seeding time.
After the majority have been secured the remaining occupied
burrows should be treated with poison, preferably carbon bi-
sulphide (Fisher).

REFERENCES
The Crayfish, by Thomas Huxley.
Introduction to Zoology, by R. W. Hegner. — The Macmillan Co., N. Y.
City.
The American Lobster, by F. H. Herrick. — Bulletin U. S. Fish Commis-
sion, Vol. XV.

CHAPTER XVI
CRUSTACEA IN GENERAL

THE crayfish belongs to the order Decapoda, so-called be-

cause its members possess ten walking legs (five pairs). Most

Fic. 77.—A, edible or blue crab; B, fiddler or soldier crab. (From
Paulmier.)

of the larger Crustacea are decapods; they not only are the most

important so far as our food supply is concerned, but many of

them are of great interest because of their peculiar habits and
137

138 PRACTICAL ZOOLOGY

structural modifications. The lobsters, shrimps, prawns, spider
crabs, hermit crabs, edible crabs, and fiddler crabs are all dec-
apods. The rest of the Crustacea are for the most part small
and inconspicuous. The barnacles have a very remarkable
life history. Some of the other species, like the sow bugs, have
become terrestrial in habit. Most crustacea live in the sea; a
great many species, however, live in fresh water, including the
one-eyed Cyclops, the water flea, Daphnia, and the fairy shrimp,
Branchipus.

Fic. 78. — Photograph of hermit crab in snail shell. (From Calman.)

Crabs. — The crabs differ from the crayfish in having a very
small abdomen which is folded under the large, broad cephalo-
thorax as in the blue or edible crab (Fig. 77, A). The spider
crabs are curious-looking creatures with long, stiltlike legs which
carry them over the rough sea bottom with ease. One species
living in Japan is said to measure twenty feet from tip to tip of
the first pair of legs. The fiddler crabs (Fig. 77, B) are curious

CRUSTACEA IN GENERAL 139

little animals which run about sideways, moving one of their
pinchers, which is larger than the other, in the manner of a fiddle
bow.

The hermit crab (Fig. 78) is not satisfied with the protection
afforded by its exoskeleton, but searches about until it finds an
empty snail shell, into which it inserts its abdomen. This pro-
tecting shell is then carried about until the hermit crab has out-
grown it, when it is cast off and a new and larger one found.
Often the shell becomes covered with a colony of polyps. These
polyps are transported from place to place by the crab, and in

Fic. 79. — A common shrimp. (From Davenport.)

return they pay their fare by stinging any of the crab’s enemies
that may attack it. Such a relation is similar to that described
between the plant lice and the ants (p. 42) and is known as
commensalism (con, together; mensa, table), meaning living at
the same table.

Shrimps (Fig. 79) and prawns are long-tailed decapods that
resemble the crayfish; they are important as a food supply for
man.

Barnacles. — The barnacles (Fig. 80) are marine Crustacea
that were for a long time placed in the same group with the
oysters because of their shell. A study of their life history,
however, proved them to be Crustacea. The young when they
hatch from the egg look something like young crayfishes. When
they have reached a certain size, they attach themselves to rocks,
whales, turtles, or the bottoms of ships, and form a shell about
themselves. Here they spend the rest of their lives drawing

140 PRACTICAL ZOOLOGY

water into their shell by movements of their feet and eating the
minute plants and animals contained in this water.
Fresh-water Crustacea. — In fresh water, besides the cray-
fish, one is likely to encounter the fairy shrimp, the water flea,
and cyclops. The fairy shrimp, Branchipus (Fig. 81, C), is a
beautifully colored, almost transparent crustacean, one of the

Fic. 80. — Several oysters to whose shells are attached many barnacles (near the
center) and mussels (below and at the sides). (From Bulletin U.S. Fish Com.)
simplest of them all. It is often abundant in the spring in
ponds that later dry up. Here it swims slowly about on its back,

propelling itself by its leaf-like appendages.

The water flea, Daphnia (Fig. 81, B), has a narrow body, re-
sembling a flea in this respect. It is protected by a heavy shell,
from the anterior end of which the large antenne are protruded
and moved, serving as swimming organs.

Antenne are also used as swimming organs by Cyclops (Fig.
81, A). Individuals of this little one-eyed creature are present
by the million in almost every fresh-water pond. During the
summer the female carries a pair of brood pouches full of eggs

CRUSTACEA IN GENERAL I4I

with her, one on either side of the abdomen. The single eye of
this crustacean suggested the race of mythical giants of Sicily
after which it was named.

Fic. 81. — Common crustacea.

‘A, cyclops; B, a water flea; C, the fairy shrimp; D,a sow bug. (After
Smith.)

The commonest terrestrial Crustacea are the little pill bugs,
sow bugs, or wood lice (Fig. 81, D; Fig. 73) which are usually abun-
dant under boards and stones. Their bodies, like that of the cock-
roach, are much flattened, enabling them to creep into narrow
crevices. Although they live on land, they require a moist at-
mosphere. They feed on decaying vegetable matter.

142 PRACTICAL ZOOLOGY

Relations of Crustacea to Man. — The most obvious relation
between the Crustacea and man exists in the case of those species
that are used for food. A great many different species are util-
ized in this way in various parts of the world; those most impor-
tant in this country are crayfishes, lobsters, shrimps, and edible
crabs.

The crayfishes are not used extensively as food although the
difficulty of obtaining lobsters has attracted attention to these
smaller relatives, and it is probable that the raising of cray-
fishes for market will soon become a flourishing industry.

Lobsters have long been used as food. They are especially
abundant along the coast of Maine, but occur in lesser numbers
at other points on our northeastern coast. Lobsters have been
captured so persistently, however, that a great decrease in size
has taken place, so that where formerly individuals weighing
twenty-five pounds were not rare, now they seldom weigh over
two pounds. Many efforts have been made to control the catch-
ing of lobsters so as to conserve the supply, but thus far with
little success.

The blue or edible crab (Fig. 77, A) comes next to the lobster
as an important article of food for man. It occurs along the
Atlantic and Gulf coasts, where, just after shedding its exoskele-
ton, it is known as the soft-shelled crab. In this condition it is
considered more valuable than when the shell is hard.

The shrimps (Fig. 79) and prawns are smaller than the lobster
and crab, and hence of less importance as a food supply for man,
though they are captured and eaten in great numbers.

Value as Food for Fish. — Although the Crustacea used as
food by man in the United States are valued at several millions
of dollars annually, still their indirect value as food for fish is
probably greater. The smaller Crustacea furnish perhaps the
principal item in the fish bill of fare. They are extremely
abundant everywhere; at one time there may be more than
250,000 in a single cubic yard of lake water and an equal number
in an equal amount of sea water. Their effect upon the abun-

CRUSTACEA IN GENERAL 143

dance of mackerel has recently been studied with the following
results: The number of fish depends upon the number of Crus-
tacea that are available for food. These Crustacea feed upon
minute plants, mostly diatomes, that float about near the sur-
face of the sea, and their abundance must depend upon the
abundance of these plants. The plants require sunlight for their
growth and multiplication, so that the amount of sunlight con-
trols the number of plants. Actual observations have shown
that a season of bright sunshine is followed by good fishing, and
a cloudy one always results in a poor. catch of mackerel. The
relations here indicated remind one of those pointed out by Dar-
win between bees and clover (see p. 4).

Injuries Due to Crustacea. — Very few Crustacea are injurious
to man. The damage done by the crayfish has already been
noted (p. 135). Several species make burrows in wood and
often do considerable damage to the timbers in piers. Wood
that is placed in situations open to attack by little Crustacea is
commonly treated with creosote.

One species, Cyclops, is the means of transmitting the para-
sitic guinea worm which causes the appearance of dangerous
abscesses on the legs of people living in tropical Africa. The
young worms that chance to fall into water penetrate the body
of the Cyclops where they live. Sometimes a parasitized crus-
tacean is swallowed by man, as may easily happen in drinking
water from a pond. In the alimentary canal of man the worms
are freed, after which they bore their way through his body until
they reach the legs, where they produce the abscesses.

Characteristics and Classification. —- The Crustacea are ar-
thropods most of which live in the water and breathe by means
of gills. The body is divided into head, thorax, and abdomen,
or the head and thorax may be fused, forming a cephalothorax.
The head usually consists of five segments fused together; it
bears two pairs of antenne (feelers), one pair of mandibles (jaws),
and two pairs of maxille. The thorax bears a variable number
of appendages, some of which are usually locomotory. The ab-

144 PRACTICAL ZOOLOGY

dominal segments are generally narrow and more mobile than
those of the head and thorax ; they bear appendages which are
often reduced in size.

A convenient method of classifying the Crustacea is to place
them in two subclasses.

Subclass I. Entomostraca. — Fairy Shrimps, Water Fleas,
Cyclops, and Barnacles.

Subclass II. Matracostraca. — Pill Bugs, Sow Bugs, Beech
Fleas, Shrimps, Crayfish, Lobsters, and Crabs.

REFERENCES

The Life of Crustacea, by W. T. Calman. — Methuen and Co., London,
England. :

Higher Crustacea of New York City, by F. C. Paulmier. —N. Y. State
Education Department, Albany.

College Zoology, by R. W. Hegner. — The Macmillan Co., N. Y. City.

The Sea Beach at Ebb Tide, by A. F. Arnold. — The Century Co., N. Y.
City.

CHAPTER XVII
THE MUSSEL OR CLAM AND OTHER BIVALVES

Habitat. — When we inquire into the details of everyday life
of animals, we soon learn that a struggle is all the time taking
place between each individual and others of its kind, between it
and individuals of other species, and between it and its physical

Fic. 82. — Digging soft-shell clams on a mud-flat. (From Davenport.)

and chemical surroundings. But there are some animals that
live in the same general habitat that seem to get along together
peacefully. Two examples are the crayfish and the fresh-water
mussel or clam. Both inhabit the same ponds or streams and
may live within a few inches of each other on the bottom; both
must live in water containing calcium carbonate from which part
of their shellsis built up. Perhaps they live in peace because the
crayfish hides under a rock while the mussel plows through the
L 145

146 PRACTICAL ZOOLOGY
mud or sand, or because both are so well protected by their shells
that neither can injure the other. Most of the mussel-like ani-
mals live in the sea; one of these, the long-neck or soft-shell clam,
is an important article of food and is dug out of the sands or
mud between high-tide and low-tide lines in great numbers and
sold in fish markets (Fig. 82). The fresh-water mussel and the
long-neck clam dif-
fer in certain re-
spects, but their
general activities
and structure are
similar, and either
makes good mate-
rial for study in
the laboratory.
Locomotion. — If
a living mussel is
placed on the sandy
® bottom of a body of
Behind water, it will not at
first show any signs

Fic. 83. — The external parts of a mussel.
is the inner face of an empty shell.

1, points of insertion of anterior protractor

(above) and retractor muscles (below) of the shell;
2, of anterior adductor muscle; 3, of posterior pro-
tractor of the shell; 4, of posterior adductor mus-
cle; 5, lines formed by successive attachment of
mantle; 6, umbo; 7, dorsal siphon; 8, ventral
siphon; 9, foot protruded; 10, lines of growth.

of life, but if we
wait long enough, it
will slowly open the
two valves of its

shell and protrude
a wedge-shaped,
whitish portion of the body, the foot (Fig. 83, 9). The foot is
gradually extended and forced into the sand, the body is slowly
drawn into an upright position, and a large portion of it is
soon buried in the bottom. Here the mussel may remain at
rest for some time, or it may slowly plow its way through the
sand, mud, or gravel by alternately extending its foot and then
drawing the rest of the body after it.

The Protective Shell. — The body of the mussel is exceedingly

(From Shipley and MacBride.)

THE MUSSEL OR CLAM AND OTHER BIVALVES 147

soft, but it is well protected by the shell. This shell consists of
two parts called valves (Fig. 83), and hence mussel-like animals
have received the name of bivalves. Each valve is built up of
concentric layers of calcium carbonate (Fig. 83, 10) extracted

aa \ 1
rpo ‘ ‘ ; of pe

1 Se

¢

b ; ep gg k ma
pe
Fic. 84. — Internal organs of a mussel.

@, anus; aa, anterior aorta; aam, anterior adductor muscle; b, brain;
ds, dorsal siphon; ec, excretory canal; ep, excretory pore; f, foot; g, gill;
gg, genital gland; i, intestine; k, kidney; 1, liver; lp, labial palp,; m, mouth;
ma, mantle; pa, posterior aorta; pam, posterior adductor muscle; pc, peri-
cardium; pg, pedal ganglion; pw, pericardial wall; r, rectum; ra, right
auricle; rpo, reno-pericardial opening; s, stomach; v, ventricle; vg, visceral
ganglion; vs, ventral siphon. (After Jammes.)

from the water by the animal and added to the shell by a mem-
brane just under the shell, known as the mantle (Fig. 84, ma).
The oldest part of the valve is that near the hinge where the
lines of growth are shortest; this part is the umbo (Fig. 83, 6).
One cannot tell the age of a mussel by counting the lines of

148 PRACTICAL ZOOLOGY
growth, since there may be more than one growth period during
the year.

Structure of the Shell. — If we break a part of the shell, we
find that the inner surface produces an iridescent sheen in the
light; this is the nacreous layer or mother-of-pearl. Between
this layer and the outside is a stratum of calcium carbonate
crystals, the prismatic layer; and on
the outer surface is a thin, horny layer,
the periostracum, which protects the
other layers from being dissolved
away by the carbonic acid in the
water.

Movement of the Valves of the
Shell.— The two valves of the shell
are held together at the upper, dorsal
edges by an elastic, ligamentous hinge
(Fig. 85, ro) and in some species fit
together by means of toothlike pro-

Fic. 85. Cross section of
a mussel.
1, right auricle; 2, epi-

branchial chamber; 3, ven-
tricle; 4, vena cava; 5, non-
glandular part of kidney; 6,
glandular part of kidney;
7, intestine in foot; 8, peri-

jections. The elasticity of the hinge
tends to force the valves open, but
they are held closed or allowed to
spring open, to any desired extent by
a pair of strong bands of muscles, the
adductors, which extend across from
one valve to the other, one near the

cardium; 9, shell; 10, liga-
ment of shell. (After
Howes.)

anterior, the other near the posterior
edge of the shell (Fig. 84, aam, pam).
When an animal dies, the adductor
muscles relax and the valves open. This is why the shells of
dead mussels are always open.

Water Current in the Mussel. — When closed or nearly closed,
there is within the shell a rather large cavity in which the body
lies; this is the mantle cavity (Fig. 85).
communicates with the water surrounding the mussel by means

The mantle cavity

of two tubes or siphons, one above the other, formed by the

THE MUSSEL OR CLAM AND OTHER BIVALVES 149

mantle at the posterior end and extruding a little from the shell
(Fig. 83, 7 and 8). If a little powdered carmine is placed near
the openings of these tubes, it will be drawn into the lower and
expelled from the upper one. (See arrows in Figure 84.) This
indicates that a current of water is continually entering, passing
through the mantle cavity within, and then flowing out again.
It is easy to understand from this how the mussel gets its food.
Very small particles of animal or vegetable matter floating about
in the water are drawn into the mantle cavity through the lower
incurrent opening (siphon) and waste matters pass out through
the upper excurrent opening (siphon). Oxygen is also taken
from this fresh current of water and carbon dioxide passes out
through the excurrent siphon.

Principal Parts of the Body. — To study the mechanism which
creates these currents one must open up the shell by cutting the
large adductor muscles; this is easily accomplished by inserting
a sharp knife near either end of the hinge. The parts of the body
remind one of the leaves of a book with the valves of the shell
representing the covers (Fig. 85). Just within the shell on
either side is a thin flap, the two lobes of the mantle that se-
crete material which forms the shell (Fig. 84, ma). Inside of
the mantle cavity hang down the thick, muscular foot in the
center (Fig. 85, 7) and a pair of leaf-like gills on either side.
Some of the inner organs are inclosed by the foot and the rest
are contained in the soft mass above it.

Respiration. — The gills are delicate structures, each consist-
ing of two thin layers of gill filaments connected by longitudinal
crosspieces which break it up into tubes (Figs. 84, g, and 85).
If we cut off a small piece of the gill of a living mussel, an opera-
tion that does not cause pain to the animal, and examine it under
a compound microscope, we shall find it covered with minute
hairlike projections, the cilia, which are waving back and forth.
A little powdered carmine placed in the water near the piece of
gill will be driven in one direction by these cilia. Considering
the fact that all the gill filaments are covered with cilia, it is

I50 PRACTICAL ZOOLOGY

easy to understand what produces the current of water entering
and passing out through the siphons. These cilia always pro-
vide a fresh supply of water from which oxygen and food are ob-
tained, thus enabling the sluggish mussel to live successfully
without moving about for its food and oxygen. In one respect
the mussel and crayfish are similar; both create currents of water
which allow them to breathe when resting quietly in one place,
but the crayfish must go out after its food and is therefore active,
whereas the mussel draws the food to itself and may therefore
be as lazy as it pleases.

Sensitiveness to Surroundings. — The mussel has no distinct
head, although it possesses near the mouth the nervous ganglia
called the brain (Fig. 84, 0). Its sense organs are also poorly
developed. These are all indications that the animal is de-
generate. Nevertheless it copes successfully with its enemies
and its physical surroundings, which is about as much as can be
said of any of the animals, not excluding man.

If the water in which the mussel is living is charged with an
injurious chemical substance or if the edges of the siphons are
touched, the siphons are drawn in and the shell closed. The
animal thus protects itself from injurious substances in the water
and from mechanical injury, and the results of the experiments
indicate that the edges of the siphons bear sense organs of touch.
The sense organs which detect chemical changes in the water are
supposed to be two yellowish patches, called osphradia, situated
just beneath the posterior adductor muscle and hence near where
the incoming stream of water enters. No eyes are present, al-
though casting a shadow upon an individual lying in the sun
causes a retraction of the siphons and proves it to be sensitive
to different light intensities.

Digestion. —The mouth lies near the anterior adductor
muscle (Fig. 84, m) and is provided with a pair of leaf-like pro-
cesses on either side, the labial palps (Fig. 84, /p). The cilia
covering these palps drive food particles into the mouth and
down the cesophagus. The digestive apparatus is not very dif-

THE MUSSEL OR CLAM AND OTHER BIVALVES 151

ferent from that of the crayfish. The food passes through the
short cesophagus into the saclike stomach (Fig. 84, s), where it
is acted upon by digestive juices from the liver (Fig. 84, J).
That part not absorbed by the walls of the stomach enters the
intestine (Fig. 84, 71) which is coiled about in the foot. The in-
testine passes through a cavity (the pericardial cavity, Fig. 84, pc)
just beneath the hinge of the shell and terminates in the anal
opening just above the posterior adductor muscle (Fig. 84, a).

Circulation. — As in the crayfish, the digested food is ab-
sorbed by the walls of the intestine and passes into the blood.
There is a heart in the pericardial cavity consisting of a muscu-
lar portion, the ventricle (Fig. 84, v), which forces the blood
through the anterior and posterior aortas (aa and pa), and a
pair of auricles (ra) which receive the blood after it has circu-
lated throughout the body, and deliver it to the ventricle. Dur-
ing this circulation, part of the blood passes through the gills,
where it receives a fresh supply of oxygen and is relieved of its
carbon dioxide, and part enters the walls of the excretory
organ, the kidney (k), just beneath the pericardial cavity,
where the waste materials it bears are excreted. Thus are
the functions of digestion, circulation, respiration, and excre-
tion carried on.

Reproduction. — Reproduction in mussels is quite a remark-
able process because of the peculiar habits of the young. The
adults are either male or female, and the ovaries of the female
and testes of the male are situated in the foot (Fig. 84, gg).
The male fertilizing elements, the spermatozoa, arise in the testes,
pass out through the genital opening (ep), and are carried from
the animal’s body in the current of water flowing out of the dor-
sal siphon. Ifa female mussel is near, the water containing sper-
matozoa is drawn into her mantle cavity through the ventral
siphon, and the eggs which have dropped from the female geni-
tal opening into the gills become fertilized. The developing
eggs remain in the gills for a long time, finally changing into a
young stage known as a glochidium.

152 : PRACTICAL ZOOLOGY

The glochidium has a shell (Fig. 86, A, sh) consisting of two
valves which are hooked; these may be closed by a muscle (ad)
when a proper stimulus is applied. A long, sticky thread called
the byssus (by) extends out from the center of the larva, and
bunches of setz (s) are also present.

In the mussel Anodonta, the eggs are fertilized usually in
August, and the glochidia which develop from them remain in
the gills of the mother all winter. In the following spring they
are discharged, and if they chance to come in contact with the
external parts of a fish, this contact stimulus causes them to

al A rid B

Fic. 86. — A. A young mussel or glochidium. ad, adductor muscle; by,
byssus; s, sete; sh, shell. (After Balfour.)

B, the gills of a fish in which are embedded many young mussels forming
“ blackheads.”’ (After Lefevre and Curtis.)

seize hold of the fish’s gills by closing the valves of their shell.
The glochidium probably chemically stimulates the skin of the
fish to grow around it, forming the well-known “ worms” or
“blackheads” (Fig. 86, B). While thus embedded, the glo-
chidium receives nourishment from the fish and undergoes a stage
of development (metamorphosis), during which the foot, muscles,
and other parts of the adult are formed. After a parasitic life
of from three to twelve weeks, within the tissues of the fish, the
young mussel is liberated and takes up a free existence.

One result of the parasitic habit of larval mussels is the disper-

THE MUSSEL OR CLAM AND OTHER BIVALVES- 153

sal of the species through the migrations of the fish. Only in
this way can we account for the rapid colonization of certain
streams by mussels, since the adult plows its way through the
muddy bottom very slowly.

The Oyster. — The oyster is the best-known relative of the
mussel principally because of its use as food. Oysters are
widely spread, being found on all seacoasts. Those occurring
in different localities often belong to different species; those on
the Atlantic coast are known by the name Osérea virginiana,
and the principal species in Europe as Ostrea edulis. In Japan
lives a species that sometimes grows to be three feet long.

The adult oyster is unable to move from place to place. It
lies on the bottom of the sea, near the coast, attached by its left
valve, which is the larger. This attached condition probably
explains the absence of the foot in the oyster, since this loco-
motor organ could be of no use to a stationary animal. The
lack of the foot renders the oyster soft and is really responsible
for the oyster’s edible quality. The mussel, on the other hand, is
not relished as a food because of the toughness of its muscular
foot. In general structure the oyster differs very little from the
mussel.

“ Few realize what an enormous business the oyster trade has
become in the United States. The value of it is stated to be
over thirteen million dollars annually, twenty-five million bush-
els of oysters being taken from the Chesapeake alone. The
edibility of the oyster has been known from early times, for vast
heaps of empty oyster-shells, known as kitchen middens, occur
in various parts of the world. Some of them are of such size
and extent as to warrant the belief that their formation must
have required centuries. Shell mounds are found along the
coasts of Florida and are of some archeological value. The
cultivation of oysters, as recorded by Pliny, dates from the first
century B.C.

“The poet Gay’s opinion of the first man who ever ate an
oyster is expressed thus: —

154 PRACTICAL ZOOLOGY

“The man had sure a palate cover’d o’er
With brass or steel, that on the rocky shore
First broke the oozy.oyster’s pearly coat,
And risk’d the living morsel down his throat.’

“The methods employed in oyster farming resemble those of
agriculture, in that the bed is prepared, seed is sown, superfluous
and foreign growths are weeded out, enemies are driven off, and
the crop is harvested at stated seasons. The oyster is ovovivip-
arous; that is, it retains its eggs until they are partly matured.
These are held in the gills and mantle folds until the time of
spawning, which begins in May and lasts through the summer
months. The larve are ejected as ciliated spheres, called spat,
and swim freely about for some time, often several days, before
finding a resting spot. The oyster grower secures many of the
larve by placing in their way substances to which they can at-
tach themselves. The American culturist strews his carefully
prepared beds with empty oyster-shells, on which the spat settle,
and the seed is thus secured; for the spat, once fastened, lose
the power of locomotion and become fixed. At the end of a
year the shells which hold the young oysters (now about an inch
long and called “ fry ”’) are taken up, and the fry are thinned out
and replanted, or are sold to other oyster farmers.

‘“ During the period of their growth the oysters are sometimes
transplanted several times. At the end of three to five years
they have attained marketable size, and the beds are then har-
vested and prepared for another crop. Some oystermen have
several acres of bottom under cultivation. These areas are
obtained by purchase or grant from the state, and their limits
are as defined as are the fenced-off acres of upland meadows.
The business of the oyster culturist is to plant the young oysters
and watch their development, keeping the beds thinned that the
oysters may not be too crowded for their normal and symmetrical
growth, and protecting them from their enemies, of which there
are many.

‘The principal enemies of the oyster are the starfish and the

THE MUSSEL OR CLAM AND OTHER BIVALVES§ 155

predaceous mollusks, Urosalpinx and Nassa. Whole beds have
been known to be destroyed in a single night by the visitations
of starfishes, hence a constant watchfulness is required on the
part of the oysterman. Policing the oyster farms is another of
his cares, for pirates abound, and a bed may be robbed in the
night as easily as an orchard may be despoiled of its fruit.
Oyster culture is carried on extensively in Long Island Sound,
on the coasts of New Jersey and Virginia, and in the Chesapeake
Bay. The oysters from certain localities are esteemed more
than others, the flavor of the oyster being very dependent upon

Fic. 87. — A, soft-shell clam. _
B, razor-shell clam. (From Arnold.)

the purity of the water and on the organisms upon which it feeds.
It has been definitely shown that oysters grown in contaminated
waters have been the agents of transmitting disease, notably
typhoid fever and cholera” (Arnold).

Soft-shell Clam. — Among the other interesting relatives of
the fresh-water mussel that one sees at the seacoast are the soft-
shell or long-neck clam, the razor-shell clam, the hard-shell
clam, and the scallop. The soft-shell clam (Fig. 87, A) lies
buried in the mud or sand between tide marks with its long
neck, its siphon, stretched up toward the surface. Food is abun-
dant on these mud flats and is obtained, as is that of the

156 PRACTICAL ZOOLOGY

mussel, by the cilia which draw the water loaded with minute
particles of animal and vegetable matter into the body through
the siphon. The commercial value of the clam is not as great
as that of the oyster, but is nevertheless considerable.
Razor-shell Clam. — The razor-shell clam (Fig. 87, B) also
lives in burrows in the sand and obtains its food just as the soft~
shell clam does. It is a remarkably rapid digger, being able to
burrow down into the sand about as fast as one can follow with

Fig. 88. — A, hard-shell or little-neck clam.
B, scallop shell. (From Arnold.)

a spade. The shell is long and slender, hence its popular name,
razor-shell clam.

Hard-shell Clam. — The hard-shell clams are very abundant
on our eastern coast. One species, Venus mercenaria (Fig. 88,
A), is commonly known in hotels and restaurants as the “ little-
neck’? clam. It received its specific name (mercenaria) because
the purple patch on the margin of the shell furnished “ wam-
pum,” the money used by the Indians.

Scallop. — Scallop shells are among the most beautiful of
seashells, and are well known to every one who visits the sea-
coast (Fig. 88, B). The valves of scallops are rounded and or-

THE MUSSEL OR CLAM AND OTHER BIVALVES 157

namented with radiating ribs. Near the umbo are two projec-
tions, the “ ears,” characteristic of all the shells of the genus
Pecten to which the scallops belong.

The outline of Pecten has been considerably employed in con-
ventional designs for mural decorations; indeed, the figure of a
well-known Mediterranean pecten (P. jacobius), found com-
monly in Palestine, became an emblem of religious significance
during the middle ages. Returning crusaders fastened to their
garments a specimen of ‘St. James’s shell” as an evidence of the
fact that they had been to the Holy Land, and the design of the
shell came to be adopted upon many coats of arms and also in
the insignia of various orders of devout and adventurous knights
of the middle ages (Arnold).

Classification of Mussels and Clams. — The mussels, clams,
scallops, and similar bivalves belong to the class Pelecypoda of
the phylum Mollusca. They possess a shell consisting of two
valves, a bilobed mantle, and leaf-like gills. There is no head
and no rasping organ (radula, see p. 161) inthe mouth. They are
all aquatic and mostly marine. The four orders into which the
class is divided are separated largely on the characteristics of the
gills. They are very similar and so need not be given here.

REFERENCES
The Cambridge Natural History, Vol. III. — The Macmillan Co., N. Y.
City.
Bulletins of the U. S. Fish Commission.
The Sea Beach at Ebb Tide, by A. F. Arnold. — The Century Co., N. Y.

City.

CHAPTER XVIII
A LAND SNAIL AND OTHER MOLLUSKS

INCLUDED with the bivalves in the phylum Mollusca are four
other classes. Two of these, the Amphineura and Scaphopoda,
are comparatively rare; the third, the Cephalopoda, is repre-
sented by some very interesting marine species like the octopus
and chambered nautilus; and the fourth, the Gastropoda, is
abundantly represented almost everywhere by the snails and
slugs. The activities and structure of snails may best be illus-
trated by a consideration of a common land snail.

Life on Land. — Mollusks are naturally aquatic animals, and
when certain of them forsook the water for a life on land, their
habits and structures changed in order to meet the terrestrial
conditions. In the first place the evaporation of water from
the body had to be retarded. This is accomplished partly by the
shell and partly by the layer of viscid substance, the mucus,
which covers the skin. However, in spite of these protections
from evaporation, land snails can exist only in a moisture-laden
atmosphere, becoming active only during damp weather and on
dewy nights, when there is no sun to dry up their bodies. When
placed in a dry vessel, snails withdraw into their shells and re-
main inactive until they are moistened; such an experiment
may be carried out in any laboratory. In prolonged dry weather
the mucus secreted by the edge of the mantle forms a thin mem-
brane, the epiphragm, across the opening of the shell, which
prevents desiccation.

Protection. —THE SHELL.— Snails are protected by their
shells not only from evaporation but also from mechanical in-
jury and from many enemies. The shell is coiled about a cen-

158

A LAND SNAIL AND OTHER MOLLUSKS 159

tral axis, the columella. The oldest part, as in the bivalves, is
the tip where the growth rings are the smallest. It is built
large enough to accommodate the entire animal. When prop-
erly stimulated, the snail is retracted into its shell by a muscle
attached to the columella. The composition of the shell is like
that of the mussel, and on account of the necessity of obtaining
calcium carbonate with which to build it, snails are only able
to live in regions where chalky or limestone soil exists.
Locomotion. — The food of the snail consists of bits of leaves.
It must therefore be able to crawl about and must possess the
proper sense organs
for becoming aware
of its surroundings.
Snails are notori-
ously slow-moving
creatures, but while
they move only at
a “snail’s pace,”
still this is rapid
enough to enable Fic. 89. — Diagram showing the structure of a snail.

Sch.

them to reach their A., anus; At., respiratory aperture, the entrance to
¢ mantle cavity indicated by arrow; D., intestine;
food which 1S, of F., foot; Fu., tentacles; Ko., head; M., mouth; Mh.,
ity; ; f
abundant mantle cavity; Mt., mantle; R.Mt., free edge o:
oe mantle; Sch., shell. (From Schmeil.)
everywhere.

The locomotor organ of the snail is a simple mass of muscle,
the foot (Fig. 89, F), similar to that of the clam. It is used very
differently, however. The foot glides along by means of a series
of wavelike contractions which start at the posterior end and
move forward. No matter how smooth or rough the surface
over which the animal is moving, the speed is always the same.
This is explained by the fact that as the snail moves along it
secretes near the anterior end of its foot a band of slime or mucus
upon which the rest of the foot glides along. Thus the amount
of friction is always the same regardless of the roughness of the

surface.

160 PRACTICAL ZOOLOGY

Sensitiveness to Surroundings. — The sense organs that make
the snail aware of the character of its surroundings, enabling it
to find food and escape its enemies, are situated on the head.
Unlike the mussel, the snail possesses a very distinct head. The
head bears two pairs of tentacles or “ horns” (Fig. 89, Fi.); the
upper, longer tentacles bear each aneye. These eyes, however,
are probably not organs of sight, but simply serve to distinguish
between lights of different intensities, or since snails are active

1
1 i cre \
9 7 et ss
Fic. 90. — The snout of a snail cut vertically and lengthwise to show the

mouth and rasping organ.

1, dorsal wall of head; 2, mouth; 3, jaw; 4, radula; 5, cartilage of tongue;
6, muscular wall of pharynx; 7, muscles running from pharynx to ventral
wall of head; 8, space in head for withdrawal of tongue; 9, pocket for radula;
10, esophagus; 11, opening to salivary gland; 12, fold behind radular pocket.
(From Lang.)

at night, may be adapted to dim light. If touched, these tenta-
cles are quickly drawn in, being introverted like the fingers of a
glove. Food may be located at some distance, giving us reason
to think that snails have a sense of smell; the smaller pair of
tentacles is supposed to bear the olfactory organs. <A third
sort of sense organs, a pair of statocysts, lie in the head and con-
trol the equilibration of the animal.

Method of Feeding. — The particles that constitute the

A LAND SNAIL AND OTHER MOLLUSKS 161

snail’s food are rasped from the plants by a thin, filelike band
covered with minute backwardly pointed teeth. This organ,
the radula (Fig. 90, 4), is protruded from the mouth and drawn
across the plant, thus scraping off very fine particles. A sort of
jaw is also present (Fig. 90, 3) which aids the radula by cutting
off pieces of the plant for the radula to work upon.
Respiration. — The terrestrial habit of the snail requires an
entirely different breathing apparatus from that of its aquatic
relatives, and instead of a mantle cavity filled with water its
mantle cavity has become a sort of lung (Fig. 89, W/h.). Air is

Fic. 91. — Flashlight photograph of earthworm and slug crawling on a pave-
ment at night. (From Davenport.)

taken into and expelled from this cavity, and the exchange of
oxygen and carbon dioxide takes place between the air inhaled
and the blood in the numerous blood vessels that are present in
the lining of the mantle cavity.

Slugs. — Besides the ordinary land snails there are a few
terrestrial gastropods that are so peculiar as to deserve special
mention; these are the slugs (Fig. 91). Slugs may be found
under boards or stones in damp places. They are apparently
without a shell, but there is a thin, horny plate embedded in the
mantle which is the last remnant of what was no doubt in the
slug’s ancestors a fully developed shell. Some slugs, especially
the introduced species, Limax maximus, are a nuisance in green-
houses because of their attacks on plants.

M

162 PRACTICAL ZOOLOGY

Fresh-water Snails. — The land shails and slugs belong to the
order Pulmonata, but in this order are also included the fresh-’
water snails that are so common in ponds and sluggish streams.
Pond snails are very easily collected and kept in aquaria.
Their habits and structures differ but slightly from their ter-
restrial relatives. They are not truly aquatic, since they must

ely,

D E F G
Fic. 92. — Shells of common snails.

A, helicodiscus; B, planorbis; C, polygyra; D, physa; E, pleurocera;
F, goniobasis; G, lymneza. (From various authors.)

come to the surface from time to time to breathe. Often threads
of mucus are formed which extend from the bottom to the sur-
face of the water, up which the snails travel when they wish a
fresh supply of air. The shells of pond snails are less liable to
injury than those that live on land and are correspondingly
thinner.

Three common fresh-water snails are Physa, Lymnea, and
Planorbis. Physa (Fig. 92, D) lives in ponds and brooks and
feeds on vegetable matter. It is a sinistral snail, since if the
shell is held so that the opening faces the observer and the spire

A LAND SNAIL AND OTHER MOLLUSKS 163

points upward, the aperture will be on the left. Lymnea (Fig.
92, G) is a very common pond snail. Its shell is coiled in an
opposite direction from that of Physa and is called dextral.

Fic. 93. — Marine gastropods.

A, sycotypus; B, a nudibranch; C, the oyster drill; D, littorina or periwinkle.
(From Davenport.)

Planorbis (Fig. 92, B) differs from Physa and Lymnea in having
a shell coiled in one plane like a watch spring.

Marine Gastropods. — The majority of the marine gastropods
have shells, but many of them do not; some of the latter are

164 PRACTICAL ZOOLOGY

called nudibranchs. The periwinkle (Fig. 93, D) is a very com-
mon shelled snail on the North Atlantic seashore. It was
introduced from Europe, where in many localities it is used as
an article of food by the natives.

The oyster drill (Fig. 93, C) and several other marine snails
make a practice of boring through the thick shells of oysters and
other bivalves with their radulas and taking out the soft body
of the victims through the hole.

The term nudibranch is applied to certain shell-less marine
gastropods. The nudibranchs (Fig. 93, B) resemble the ter-

Fic. 94. — A, the squid.
B, the octopus; .1, at rest; B, in motion. (After Merculiano.)

restrial slugs; they do not breathe air, however, but take oxy-
gen from the water by means of naked gills, or through the
mantle.

The shelled marine Gastropoda usually breathe by means of
gills. In Sycotypus (Fig. 93, A), for example, there is a trough-
like extension of the collar, the siphon, which leads a current of
water into the mantle cavity where the gill is situated.

A LAND SNAIL AND OTHER MOLLUSKS 165

Cephalopods. — The cephalopods are all marine mollusks.
The commonest species along our eastern coast is the squid (Fig.
94, A). Squids are spindle-shaped animals that swim about
freely by means of a pair of fins that wave gently up and down,
or propel themselves rapidly in any direction by means of a jet
of water forcibly driven from a movable tube, the siphon, sit-
uated just beneath the head. Their food consists of small fish,
Crustacea, and other squids which are captured and held by
means of ten tentacles provided with suckers. The squid’s

3

Fic. 95. — The chambered nautilus.

1, last completed chamber of shell; 2, hood part of foot; 3, shell muscle;
4, mantle cut away to expose, 5, the pinhole eye; 6, outer wall of shell, partly
cut away to show chambers; 7, siphon; 8, lobes of foot; 9, funnel. (After
Kerr.)

eyes should be mentioned, for they are very large and resemble
somewhat those of human beings.

The relatives of the squid that are perhaps most interesting
are the chambered nautilus and the octopus. There are only a
few living species belonging to the genus Nautilus. The cham-
bered or pearly nautilus, Nautilus pompilius (Fig. 95), lives on
the bottom of the sea near certain islands of the South Pacific.
The shell is spirally coiled in one plane and is composed of com-
partments of different sizes, which were occupied by the animal

166 PRACTICAL ZOOLOGY

in successive stages of its growth. The compartments are filled
with gas and are connected by a calcareous tube in which is a
cylindrical growth of the animal called the siphon (Fig. 95, 7).
The gas in the compartments counterbalances the weight of the
shell.

The paper nautilus, Argonauta argo, is a sort of octopus, the
female of which secretes a delicate, slightly coiled shell. The
true octopus or devilfish (Fig. 94, B) lives in the Mediterranean
Sea and West Indies. It may reach a length of over ten feet
and a weight of seventy-five pounds. Devilfishes have been
accused of serious attacks on man, but are probably not so bad
as generally supposed.

The Relations of Mollusks to Man. — The bivalves are of
great economic importance because of their value as food. The
oyster is, of course, the most valuable (see p. 153). The other
bivalves that are commonly eaten by human beings are the
soft-shell clam, razor-shells, hen clams, mussels, and scallops.

‘Certain large snails are considered a delicate article of food,
especially by the French. Squids are eaten by some people,
particularly the Chinese and Italians.

As SCAVENGERS. — The fresh-water mussels are considered
inedible, but their beneficial qualities do not depend upon their
food value. They are, first of all, excellent scavengers. All
sorts of animal and vegetable particles that pollute the water are
drawn into the mantle cavity and thence into the mouth. For
this reason, a couple of mussels in a fresh-water aquarium are
almost indispensable in keeping the vessel in good condition.

PEARL Buttons. — The shells of mussels are used extensively
in the manufacture of pearl buttons, and so freely have these
mollusks been captured in the upper Mississippi River for this
purpose, and for the pearls they sometimes contain, that the
United States Bureau of Fisheries is making strenuous efforts
to restock the depleted waters by artificially rearing bivalves.
Recently a biological station has been built at Fairport, Iowa,
largely with this end in view.

A LAND SNAIL AND OTHER MOLLUSKS 167

PEARLS. — Pearls are interesting and valuable products of
bivalves. The most famous pearl fisheries are those of Ceylon.
The pearl oysters (really mussels) are taken by the thousand
and allowed to decay. Their shells are then washed out and
thrown away and any pearls that may be present are picked out
of the slimy débris. Pearls are built up around some foreign
substance within the shell such as a grain of sand or more prob-
ably around the remains of a parasitic worm. The mantle of
the mussel secretes the pearl substance in layers, just as the
shell is formed. Only a small proportion of the pearls formed by
mussels are ever taken, since many of them drop out of the shell
and are lost in the bottom and others disappear when the
mussels die.

Characteristics and Classification of Mollusks. — Mollusks
are soft-bodied animals usually protected by a shell of calcium
carbonate. They are unsegmented. The locomotor organ is
in most of them a muscular foot. The main part of the body
lies in a cavity, the mantle cavity, and is covered by an envelope,
the mantle. Three of the five classes contain common and well-
known species.

Class 1. GasTropopa. — Snails, Slugs, and Nudibranchs.

Class 2. PELEcYPoDA. — Bivalves, such as Clams, Mussels,
Oysters, and Scallops.

Class 3. CEPHALOPODA. — Squids, Cuttlefishes, Octopods, .
and Nautili.

REFERENCES

College Zoology, by R. W. Hegner. — The Macmillan Co., N. Y. City.
See references to Chapter XVII.

CHAPTER XIX

THE EARTHWORM AND OTHER SEGMENTED
WORMS

OF all the animals that are called worms only a few are true
worms; most of them are the larve of insects. The true worms
are divided into three phyla: (1) the segmented worms or Anne-
lida, like the earthworm; (2) the roundworms, or Nemathel-
minthes, like the trichina that sometimes infests pork; and (3)
flatworms, or Platyhelminthes, like the tapeworm.

Need of Moisture. — The earthworm is the most common
member of the phylum Annelida, and is abundant almost every-
where if the soil is suitable. The skin of the earthworm is soft
and naked, like that of the snail or slug; it is covered with a
thin, slimy fluid and requires damp soil or damp atmosphere or
else it will dry up. For this reason earthworms are never found
in dry, sandy soil, and appear above ground only on dewy
nights (Fig. 91), or in cloudy weather, or after a rain. Earth-
worms are not rained down, as many people suppose, but are
rained up out of their burrows.

Burrows. — The body of the earthworm is cylindrical, and
long and slender; it is well adapted to the animal’s burrowing
activities, since the earth offers little resistance to its “‘ vermi-
form” shape. The burrows are scarcely larger than the diam-
eter of the body and extend, as a rule, only for about two feet
underground, although burrows six feet long are sometimes dug.

Locomotion. — In traveling within the burrow as well as
on the surface, and in digging the burrows, the movements of
the body are similar. The anterior end is extended and the
rest of the body drawn up to it. This is accomplished by the

muscles in the body wall (Fig. 96, dw). An examination of a
108

THE EARTHWORM AND OTHER SEGMENTED WORMS 169

cross section of an animal (Fig. 97) will reveal a thick body wall
made up principally of two layers of muscles, a layer of circular
muscles (circ. mus) running around the body just beneath the
skin, and a layer of longitudinal muscles (Jong. mus) underneath
the circular ones. It is evident that when the circular muscles
near the anterior end contract, the body becomes thinner and

Fic. 96. — Diagram of the internal anatomy of the earthworm.

bw, body wall; dv, dorsal vessel; i, intestine; iw, intestinal wall; Inv,
lateral neural vessel; n, nephridium; nc, nerve cord; pv, parietal vessels; s,
septa; snv, sub-neural vessel ; t, typhlosole; vv, ventral vessel. (After Jammes.)

therefore extends, and when they relax and the longitudinal
muscles contract, the rest of the animal is drawn forward by the
shortening caused thereby. The division of the body into
rings or segments aids in the activities of these muscular layers.

Use or BrisTLes In Locomotion. — The question naturally
arises as to what keeps the anterior end of the body from being
drawn back by the contraction of the longitudinal muscle. A
similar question, why is it so difficult to drag an earthworm

I70 PRACTICAL ZOOLOGY

out of its burrow, may be answered at the same time. If a
worm be drawn through the fingers from the front backwards,
it will feel smooth to the touch, but if drawn from the back for-
wards, it will feel rough. This is due to the presence of strong,

dors.”

Pe.
fF i", a
oe ei ty

sub..vess
Fic. 97. — Diagram of a cross section of an earthworm.

circ.mus, circular muscle fibers; coel, celom; dors.v, dorsal vessel; epid,
epidermis; ext.neph, nephridiopore; hep, chlorogogen cells; long.mus, longi-
tudinal muscles; neph, nephridium; nephrost, nephrostome; n.co, nerve-
cord; set, sete; sub.n.vess, subncural vessel; typh, typhlosole; vent.v,
ventral vessel. (from Marshall and Hurst.)

sharp bristles, the seta, which extend obliquely backward from
the sides and under part of the body (Fig. 97, set). There are
four pairs of these sete in each segment, and they may be moved
by sets of muscles situated just within the body wall. They
are moved from behind forward like legs and are of special serv-

THE EARTHWORM AND OTHER SEGMENTED WORMS I7I

ice when used in climbing up in the burrows, since the body of
the animal fits its burrow so snugly.

DIGGING THE Burrow. — When digging in soft earth, the
worm simply forces its way through by alternate extensions
and contractions of the body, but in harder soil it must eat its
way through. The body of the worm is like a double tube
(Fig. 97), a small one represented by the straight alimentary
canal within the larger one, the body wall. The earth that is
eaten in digging passes into and directly through the alimentary
canal, reaching the surface in the form of castings. The cast-
ings of earthworms are the dark heaps of earth so often to be
seen on the ground after damp weather.

Food. — Digging in this way not only results in a burrow for
the worm, but provides food for it as well, since the soil con-
tains the decaying vegetable matter or humus upon which it
feeds, and the animals are careful to make their burrows in soil
containing a good supply of humus. Besides this, other food
is gathered usually at night when the worms are active. The
animals crawl out on the surface, and holding fast to the top
of their burrows with their tails, explore the neighborhood for
pieces of leaves which they drag into their holes. These leaves
when decomposed serve as food for the worms.

Digestion. — The alimentary canal, as usual in higher animals,
may be separated into distinct parts, and is accompanied by
glands which secrete juices that are discharged into it. The
food, after being sucked in by the muscular pharynx, passes
into the cesophagus, where it is mixed with a secretion from the
calciferous glands; this secretion neutralizes the acids in the
food. It then enters the crop, a thin-walled storage place.
From the crop it passes into the muscular gizzard, where it is
ground up, a process often aided by minute solid particles, like
grains of sand, that are swallowed with thefood. Next it enters
the intestine, where the digestion and absorption chiefly take
place (Fig. 96, 4).

Circulation and Excretion. — A complicated system of blood

172 PRACTICAL ZOOLOGY

vessels carries the blood about the body and with it the digested
food (Fig. 96, dv, vw, pv, Inv, snv). Waste products pass
into the blood as it circulates and are excreted by organs
called nephridia (Fig. 96, 7). Almost every segment contains
a pair of these organs. They open into the cavity surrounding
the alimentary canal by a ciliated funnel (Fig. 97, nephrost)
which draws waste matter out of the fluid within the body cavity.
The nephridia are well supplied with blood vessels, and in some
way extract from the blood circulating through them the ex-
cretory substances. These are then expelled from the body
through pores, one to each nephridium, which open on either
side near the ventral surface of the body (Fig. 97, ext. neph).

Respiration. — Oxygen is as necessary for the vital processes
of the earthworm as it is for those of higher animals, but there
are no well-defined respiratory organs. The oxygen passes
through the outer membrane of the body wall into the blood,
and carbon dioxide passes out of the blood in the same way.

Sensations. — As might be expected, the earthworm has no
well-developed sense organs, like eyes or ears, but nevertheless
it exhibits many of the ordinary sensory reactions characteristic
of more complex creatures. Thus if a light is thrown upon it
at night or if the earth is disturbed near by, it will retreat at
once into its burrow. This proves that its sensitiveness to light
and to tactile stimuli is sufficient to cause it to seek safety in
flight. The senses of taste and smell are probably also present,
since a preference for certain kinds of food, such as cabbage
leaves, and carrots, is often shown. Minute sense organs have
been found at the surface of the body. These seem more abun-
dant at the anterior and posterior ends.

Nervous System.— The nervous system which connects
with these sense organs consists of a brain lying above the
pharynx and a ventral nerve cord (Fig. 96, xc) which is situ-
ated between the body wall and the alimentary canal in the
median central portion of the body, and extends almost the
entire length of the animal. This nerve cord becomes enlarged

THE EARTHWORM AND OTHER SEGMENTED WORMS 173

in each segment, forming a ganglion from which nerves pass to
varlous parts of the body.

Reproduction. — Earthworms are hermaphroditic animals;
that is, every individual is provided with both male and female
reproductive organs. When the time for egg laying approaches,
the eggs of the worm are inclosed in a cocoon which is secreted
by a glandular thickening of the body near the anterior end, the
clitellum. They are then fer-
tilized by the spermatozoa
from another worm and de-
posited in the earth, where
they hatch into young worms,
resembling their parents ex-
cept in size.

Economic Importance. —
Charles Darwin, in his book
on the Formation of Vegetable
Mold through the Action of
Worms, has shown, by careful
observations extending over
a period of forty years, how

Fic. 98. — Section through the upper
great is the economic impor- stratum of a field showing the work of

earthworms.
tanceofearthworms. Oneacre :
A and B, arable soil thrown up by

of ground may contain over earthworms; C, marl and cinders buried
fifty thousand earthworms. by worm castings; D, subsoil not dis-
turbed by the earthworms. (From
The feces of these worms are schmeil.)
the little heaps of black earth,
called ‘castings,’ which strew the ground, being especially
noticeable early in the morning. Darwin estimated that more
than eighteen tons of earthy castings may be carried to the sur-
face in a single year on one acre of ground, and in twenty years
a layer three inches thick would be transferred from the subsoil
to the surface. By this means objects are covered up in the
course of a few years. Darwin speaks of a stony field which
was so changed that “after thirty years (1871) a horse could

174 PRACTICAL ZOOLOGY

gallop over the compact turf from one end of the field to the
other, and not strike a single stone with its shoes” (Fig. 98).

The continuous honeycombing of the soil by earthworms
also makes the land more porous and insures the better pene-
tration of air and moisture. Furthermore the thorough working
over of the surface layers of earth helps to make the soil more
fertile.

Segmentation. — Before leaving our study of the earthworm
several characteristics should be emphasized. The first of
these is segmentation. The most successful animals on the
earth, the Arthropoda, Vertebrata, and Annelida, have their
bodies built on the segmented plan. The linear row of seg-
ments, the somites, or metameres, as they are often called, are
very clearly visible in the earthworm, the centipede, and in the
abdomen of insects, crayfishes, and scorpions, but are not so
obvious in vertebrates. All of these animals, however, have
their internal organs segmentally arranged; this is most evident
in the case of the nervous system of arthropods and annelids,
in the nephridia of the earthworm, and in the backbone of man
and other vertebrates which consists of a row of similar bones,
the vertebre.

Of all these animals the earthworm is the best for the demon-
stration of both external and internal segmentation, since each
external ring indicates a single segment and corresponds to a
set of internal parts that are repeated in almost every segment.
These internal parts are a pair of nephridia, a ganglion of the
nerve cord, series of muscle bands, a part of the alimentary
canal, and a section of the body cavity separated from the cavity
in other segments by transverse partitions, the septa (Fig. 96, s).

Body Cavity.— The body cavity is another characteristic
of the annelids and higher animals that is worthy of mention;
and it is best discussed in connection with the earthworm, where
it is very simple. The body-cavity, or ccelom, is filled with a
liquid which aids in the distribution of nutritive substances,
and bears waste materials for the nephridia to carry from the

THE EARTHWORM AND OTHER SEGMENTED WORMS 175

body. An animal with thick body walls needs organs for
getting rid of excretory substances and for carrying the germ
cells (eggs and spermatozoa) out of the body; the nephridia
and egg and sperm ducts develop in con-
nection with the ccelom. In insects and
other arthropods the body cavity is filled
with blood and is not considered a true
coelom.

Leeches. — The best-known segmented
worms besides the earthworms are the
leeches or “‘ bloodsuckers,’’ a name applied
to them because they suck blood from
fishes and other aquatic animals and from
human beings who wade about or swim
in the water. They do not poison people
nor inflict any injury except a very slight
wound. Leeches are characterized by
a flattened, segmented body, and two
suckers, one at the posterior end for
clinging to its prey and the other at the
anterior end, in which the mouth is
situated. Many leeches are provided
with jaws for biting through the skin;
then the blood is sucked into the ali-

mentary canal by means of a muscular

harynx. Fic. 99. — The medicinal
ee leech.

Fe:
fer

The medicinal leech, Hirudo medicinalis ;

‘ ‘ i " 1, mouth; 2, posterior
(Fig. 99), is only four inches long, but it sucker; 3, sensory papille.
is capable of great contractions and elon- : ae Shipley and Mac-
gations. It moves along by means of its :
suckers in loops like a measuring worm or swims through the
water by undulating movements. One meal of blood is suffi-
cient to last a leech for as long as a year. Formerly leeches
were used by physicians to “ bleed” human beings, but this

practice has been. discontinued.

176

PRACTICAL ZOOLOGY

Fresh-water Segmented Worms. — Smaller and less con-
spicuous segmented worms are abundant in fresh-water ponds

and streams.

The tube worm, Tubifex, is a reddish colored
creature that makes tubes in the mud on the
bottom of slow-running brooks. The duckweed
worm, Dero, frequents the surface of ponds, where
it constructs a shelter for itself by fastening to-
gether leaves of the duckweed or other plants.

Some of the fresh-water worms have the inter-
esting method of reproducing by fission. This is
true of Nais (Fig. too, A), a little worm whose
body sometimes becomes pinched in two, each
part then growing into an entire animal. This is
one sort of asexual reproduction, or reproduction
without the use of germ (sex) cells. Sexual repro-
duction, the opposite form, is brought about
by the sex cells, the eggs and spermatozoa.

Marine Segmented Worms. — Most of us have
no opportunities to see the worms that live in the
sea, but many of
these are very inter-
esting animals. The
sandworm or clam-
worm, Nereis (Fig.
100, B), is a common
marine annelid that
swims freely about in
the water by means
of pairs of oarlike
appendages, one pair

Fic. too. — A, a fresh-water worm, Nais. on each segment. It

B, a marine worm, Nereis. (After Oersted.)

also possesses four

eyes and a number of tentacles on the head, which bear sense
organs of touch and smell. Because of the large number of
bristles on its appendages Nereis and its relatives are called

THE EARTHWORM AND OTHER SEGMENTED WORMS 177

Chetopoda or bristle-foot worms. Many of the marine worms
live in tubes somewhat like certain fresh-water species. Serpula,
for example, builds itself a crooked tube of calcium carbonate and
fastens it to the rocks near shore. Into this tube the worm
quickly withdraws when an enemy threatens.

Characteristics and Classification of the Annelida. — Anne-
lids are segmented worms, the body consisting of a linear series
of more or less similar parts. Many of the internal organs are
also segmentally arranged, notably the blood vessels, excretory
organs, and nervous system. Sete are usually present.

Most of the annelids belong to the two following classes : —

Class 1. CH#TopopA.— Annelids with sete. This class
may be subdivided into two subclasses: (1) the Polycheta, like
Nereis (Fig. 100, B), with many sete and fleshy outgrowths, the
parapodia, and (2) the Oligocheta, like the earthworm, with few
setee and no parapodia.

Class 2. Hirupinea.— Leeches. Annelids without sete or
parapodia, but possessing anterior and posterior suckers.

REFERENCES

The Formation of Vegetable Mould, etc., by Charles Darwin. — D. Appleton
and Co., N. Y. City.

General Biology, by G. N. Calkins. — Henry Holt and Co., N. Y. City.

Introduction to Zoology, by R. W. Hegner. — The Macmillan Co., N. Y.
City.

CHAPTER XX
THE ROUNDWORMS

THE unsegmented roundworms (phylum Nemathelminthes,
Fig. 101) are much more important to man than the segmented
annelids, since many of them live as parasites in the bodies of
human beings. The roundworms that are most easily obtained
are the vinegar “‘ eels.”’ These minute worms are abundant in
moldy vinegar, and when examined under the microscope, give
one a very good idea of what a roundworm looks like. They
are not injurious, and no one need be afraid to use vinegar con-
taining them.

“Horsehair Snakes.’’— Sometimes long, slender animals
are found wriggling about in watering troughs or in pools of
water, and because of their resemblance to a horsehair are
known as “ horsehair snakes.” By many they are thought
to be horsehairs that have become alive, but this is, of course,
absurd, for horsehairs placed in water will never change into
worms. The name Gordius has been applied to these animals
because they are often tangled up like the Gordian knot which
Alexander the Great severed with his sword so long ago. The
young spend part of their lives as parasites in the bodies of
aquatic insects. When these insects are devoured by other
animals, the worms are liberated in their intestines, where they
live until full grown and then escape into the water.

Intestinal Parasites. — Several kinds of roundworms may
occur in the intestines of human beings, especially children.
Some of these, also called threadworms, are from one-fourth to
one-half inch long and look like white cotton threads. Others
are reddish-white in color and much longer — from four to

178

THE ROUNDWORMS 179

twelve inches. As a rule no serious
trouble is caused by them. The usual
symptoms are disordered digestion,
restlessness at night, and grinding of
the teeth.

Trichina. — A very serious parasite
belonging to this group is the trichina
(Fig. 102), which causes the disease of
human beings, pigs, and rats called
trichinosis. The parasites enter the
human body through the eating of
inadequately cooked meat from an
infected pig. The larvae soon become
mature in the human intestine, and
each mature female deposits probably
about 10,000 young. These young
burrow through the intestinal wall and
encyst in the muscular tissue in vari-
ous parts of the body. As many as
15,000 encysted parasites have been
counted in a single gram of muscle.

There is no remedy when one is
once parasitized by these worms, but
prevention is quite simple; never eat
pork that has not been thoroughly
cooked. Pigs acquire the disease by
eating offal or infested rats.

Hookworm.— Another serious para-
site of man is the hookworm (Fig.

Fic. 101. — Anatomy of a female round-
worm, Ascaris.

1, pharynx; 2, intestine; 3, ovary; 4, uterus;
5, vagina; 6, genital pore; 7, excretory tube;
8, excretory pore. (From Shipley and Mac-
Bride.)

180 PRACTICAL ZOOLOGY

103, D). One of the most recent discoveries with regard
to this parasite is that the shiftlessness of the ‘“‘ poor whites”
of the South is to a certain degree the result of its attack. The
larve of the hookworm develop in moist earth and usually find
their way into the bodies of human beings by boring through the
skin of the foot. The hookworm is prevalent in many localities
where the people go barefoot. The larval hookworms enter the
veins and pass to the heart; from the heart they reach the lungs,

Fic. 102.—Trichina. A, Larve, among muscle fibers not yet encysted.
B, A single larva encysted.
C, Piece of pork, natural size, containing many encysted worms.
D, Adult trichina, much enlarged. (After Leuckart.)

where they make their way through the air passages into the
windpipe and thence into the intestine. To the walls of the
intestine the adults attach themselves and feed upon the blood of
their host. When the intestinal wall is punctured, a small amount
of poison is poured into the wound by the worm. This poison pre-
vents the blood from coagulating, and therefore results in a con-
siderable loss of blood, even after the worm has left the wound.

The victims of the hookworm are anemic, and also subject
to tuberculosis because of the injury to the lungs. It is

THE ROUNDWORMS 181

estimated that 2,000,000 persons are afflicted by this parasite.
The hookworm disease can be cured by thymol (which causes
the worm to loosen its hold) followed by Epsom salts. The most
important preventive measure is the disposing of human feces
in rural districts, mines, brickyards, etc., in such a manner as
to avoid pollution of the soil, thus giving the eggs of the para-
sites contained in the feces of infested human beings no oppor-
tunity to hatch and develop to the infectious larval stage.

Elephantiasis. — Another injurious species is Filaria ban-
croftt, a parasite in the blood of man. The larve of this species
are about z}p of an inch long. During the daytime they live
in the lungs and larger arteries, but at night they migrate to
the blood vessels in the skin. Mosquitoes, which are active
at night, suck up these larve with the blood of the infected
person. The larve develop in the mosquito’s body, becoming
about one twentieth of an inch long, make their way into the
mouth parts of the insect, and enter the blood of the mosquito’s
next victim. From the blood they enter the lymphatics and
may cause serious disturbances, probably by obstructing the
lymph passages. This results in a disease called elephantiasis.
The limbs or other regions of the body swell up to an enormous
size, but there is very little pain. No successful treatment has
yet been discovered, and the results are often fatal. It is said
that from 30 per cent to 4o per cent of the natives of certain
South Sea islands are more or less seriously afflicted. The
parasitic guinea worm has already been described as a parasite
of the crustacean, Cyclops (see p. 140).

Other Roundworms. — Parasitic roundworms also attack
other animals and plants. One of them, Syngamus (Fig. 103, C),
causes the disease known as gapes in poultry and game birds.
The birds swallow the young worms, which soon become mature
in the windpipe. The stomach worm of sheep (Fig. 103, B) is
the most important worm that parasitizes these animals. It
lives in the fourth stomach of sheep and goats and causes the
death of many animals, especially lambs. The nodular worm of

182 PRACTICAL ZOOLOGY

sheep (Fig. 103, A) causes the production of numerous small
nodules in the walls of the large intestines. These are some-
times mistaken by government inspectors in slaughterhouses
as evidences of tuberculosis. Dogs are frequently attacked by
worms of the genus Ascaris to which the parasitic roundworm
of man also belongs. Breeders of fancy dogs lose many valuable
animals because of the attacks of these worms. Other round-

A B
o
Fic. 103. — Parasitic roundworms.

A, nodular worm of sheep; B, stomach worm of sheep; C, worms that cause
gapes in poultry; D, hookworm.

worms live in the soil and cause growths called galls to form on
the roots of plants.

Characteristics and Classification. — The roundworms or
threadworms belong to the phylum Nemathelminthes. They are
usually long and slender and more or less cylindrical. They are
unsegmented, both externally and internally, and hence easily
distinguished from the annelids or segmented worms. Many
roundworms are parasitic in habit, but others live in water or
decaying vegetable and animal substances.

REFERENCES

Cambridge Natural History, Vol. II. — The Macmillan Co., N. Y. City.
Bulletins of Bureau of Animal Industry, U. S. Department of Agriculture.

‘CHAPTER XXI
THE FLATWORMS

THE flatworms are, like the roundworms, chiefly parasitic,
and hence of the utmost importance to man. The fresh-water
flatworm, Planaria, will be chosen first for study, since it is very
abundant, can easily be studied in the laboratory, and is com-
paratively simple. Planarians and leeches are often confused,
since both are frequently found clinging to the underside of
logs or stones in ponds and streams. They can be distin-
guished quite readily, however, since the leech is segmented and
has suckers, whereas the flatworm is unsegmented and devoid
of suckers.

4
Fic. 104. — A fresh-water flatworm, planaria.

1, eye; 2, side of head; 3, proboscis; 4, pharynx sheath; 5, genital pore.
(From Shipley and MacBride.)

Planaria. — The shape of Planaria is indicated in Figure 104.
The animal moves along over stones or other objects by means of
muscular contractions or swims through the water with the aid
of the cilia which cover it. At the anterior end are two eye-
spots (Fig. 104, 1), sensitive to light, and two sensory pits, one
on either side of the head (2), situated in earlike projections.
On the ventral surface a trifle back of the middle is the mouth

opening (3). .
I

184

PRACTICAL ZOOLOGY

Because of the great amount of coloring matter in its body the

internal organs are difficult to make out.

Fie:

105. — Anatomy of a flatworm.

cn, brain; e, eye; g, ovary; ij, is, iz,
branches of intestine; In, lateral
nerve; m, mouth; od, oviduct; ph,
pharynx; t, testis; u, uterus; v, yolk
glands; vd, vas deferens; 3, penis;
?, vagina; ¢9, common genital pore.

(After V. Graff.)

nerves.

They may be de-
scribed briefly with the aid of
a diagram (Fig. 105). A mus-
cular pharynx can be extended
from the mouth as a proboscis
(Fig. 104, 3); this facilitates
the capture of food. The food
is digested in the intestinal
trunks (Fig. 105, 71, 72, 73) by se-
cretions from their walls and is
absorbed by the walls. Since
branches from these penetrate
all parts of the body, no circu-
latory system is necessary to
carry nutriment from one place
to another. The excretory
matter is collected and carried
to the outside by a pair of longi-
tudinal, much-coiled tubes, one
on each side of the body; these
are connected near the anterior
end by a transverse tube, and
then open to the exterior in
two small pores on the dorsal
surface.

Planaria possesses a well-de-
veloped nervous system, con-
sisting of a bilobed mass just
beneath the eyespots called the
brain (Fig. 105, cv), and two
lateral longitudinal nerve cords
(In), connected by transverse

From the brain, nerves pass to various parts of the

anterior end of the body, imparting to this region a highly

THE FLATWORMS 185

sensitive nature. Reproduction is by fission, as in Nais (p. 176),
or by the sexual method, and each individual possesses both
male and female ‘organs, i.e. is hermaphroditic. The reproduc-
tive organs may be located easily in Figure 105.
REGENERATION. — Planarians show remarkable powers of
regeneration. If an individual is cut in two (Fig. 106, A), the
anterior end will
generate a new tail
(B, B!), while the
posterior part de-
velops a new head
(C, C}). A cross-
piece (D) will gen-
erate both a head
at the anteriorend,
and a new tail at
the posterior end
(D-D‘). The head
alone of a plana-
rian will grow into

an entire animal Fic. 106. — Regeneration of planaria.

(E-E). Pieces cut A, normal worm; B, B, regeneration of anterior
from various parts half; C, C1, regeneration of posterior half ; D, cross-

4 piece of worm; D!, D2, D3, D4, regeneration of same ;
of the body will &, old head; E', E2, E%, regeneration of same; F, F',
also reg enerate regeneration of new head on posterior end of old head.

(From Morgan.)
completely. No icsitiled ih

difficulty is experienced in grafting pieces from one animal upon an-
other, and many curious monsters have been produced in this way.

The power to renew lost parts by regeneration is of great
importance to these animals, since their soft bodies are often
injured by the rocks in the streams among which they live.

Parasitic Flatworms. — Besides Planaria and other free-
living flatworms that belong to the class Turbellaria, there are
two classes of parasitic flatworms, the Trematoda or flukes and
the Cestoda or tapeworms.

186

PRACTICAL ZOOLOGY

The Liver Fluke. — The liver fluke is a flatworm which lives
as an adult in the bile ducts of the liver of sheep, cows, pigs, etc.,

Fic. 107. — Anatomy of the liver
fluke.

D, anterior part of intestine
(posterior part not shown); Do,
yolk-glands; Dr, ovary; O, mouth;
Ov, uterus; S, sucker; T, testes.
(After Sommer.)

the sheep’s body with the feces.

and is occasionally found in man.
Figure 107 shows the shape and
most of the anatomical features
of a mature worm. The mouth
(O) is situated at the anterior end
and lies in the middle of a mus-
cular disk, the anterior sucker. A
short distance back of the mouth
is the ventral sucker (.S); it serves
as an organ of attachment. Be-
tween the mouth and the ventral
sucker is the genital opening
through which the eggs pass to
the exterior. The excretory pore
lies at the extreme posterior end
of the body.

The alimentary canal resembles
that of Planaria, and the repro-
ductive organs, as the figure
shows, are very complex. One
liver fluke may produce as many
as five hundred thousand eggs,
and since the liver of a single
sheep may contain more than
two hundred adult flukes, there
may be one hundred million eggs
formed in one parasitized animal.
The eggs pass through the bile
ducts of the sheep into its intes-
tine, and finally are carried out of
Those eggs that encounter

water and are kept at a temperature of about 75° F. continue
to develop, producing a ciliated larva (Fig. 108, a), which es-

THE FLATWORMS 187

capes through one end of the eggshell and swims about. This
larva is called a miracidium. It swims about until it encounters
a certain fresh-water snail, but if no snail is found within eight
hours, the larva dies.

When a snail is reached, the larva bores its way into the soft
parts of the body. Here in about two weeks it changes into a

Fic. 108. — Stages in the life-history of the liver fluke.

a, miracidium (ciliated embryo); b, sporocyst containing redie (R); c, a
redia; C, cercaria; D, gut; K, germ-cells; R, redia; d, cercaria. (From
Sedgwick.)

saclike sporocyst (Fig. 108, b). Each germ cell within the
sporocyst develops into a second kind of larva, called a redia
(Fig. 108, b, R; c). The rediz soon break through the wall of
the sporocyst and by means of germ cells (Fig. 108, c, A) usu-
ally give rise to one or more generations of daughter rediz (Fig.
108, c, R), after which they produce a third kind of larva known
as a cercaria (Fig. 108, c, C). The cercarie (Fig. 108, d) leave
the body of the snail, swim about in the water for a time, and

188 PRACTICAL ZOOLOGY

then encyst on a leaf or blade of grass. If the leaf or grass is
eaten by a sheep, the cercariz escape from their cyst wall and
make their way from the sheep’s alimentary canal to the bile
ducts, where they develop into mature flukes in about six weeks.

The great number of eggs produced
by a single fluke is necessary, because
the majority of the larve do not find
the particular kind of snail, and the
cercariz to which the successful larvee
give rise have little chance of being
devoured by a sheep. The genera-
tions within the snail, of course, in-
crease the number of larvae which
may develop from a single egg. This
complicated life history should also
be looked upon as enabling the fluke
to gain access to new hosts. The liver
fluke is not so prevalent in the sheep
of this country as in those of Europe.

The Tapeworm. —
The tapeworm, Tenia

Doan kts neers

a
i

1

'

1
&
a
©
i

‘

‘

‘

v

solium, is a common
parasite which lives as
an adult in the alimen-
tary canalof man. A
nearly related species,

Fic. 109. — A, tapeworm. The lengths of parts Tenia Saginata, 18 also

omitted in the figure are indicated. ; a parasite of man.
B, head or scolex of tapeworm. (From Shipley , :
and MacBride.) Tenia, as shown in

Figure 109, is a long
flatworm consisting of a knoblike head, the scolex (Fig. 109, B),
and a great number of similar parts, the proglottides, arranged
in a linear series. The animal clings to the wall of the alimen-
tary canal by means of hooks (Fig. tog, B, 2) and suckers (3) on
the scolex. Behind the scolex is a short neck (4) followed by a

THE FLATWORMS 189

string of proglottides which gradually increase in size from the
anterior to the posterior end. The worm may reach a length of
ten feet and contain eight or nine hundred proglottides. Since
the proglottides are budded off from the neck (Fig. 109, B, 5),
those at the posterior end are the oldest.

The anatomy of the tapeworm is adapted to its parasitic
habits. There is no alimentary canal, the digested food of the

can.excrel Can.exrcrel
t

neru.L-

\

x
schla ou

Fic. 110. — A proglottid of a tapeworm.

ob ghvit

can.excret, longitudinal excretory canals with transverse connecting vessels ;
gl.vit, vitelline or yolk-glands; nerv.1, longitudinal nerves; ov, ov, ovaries;
por.gen, genital pore; schld, shell-glands; uter, uterus; vag, vagina; vas.def,
vas deferens. The numerous, small, round bodies are the lobes of the testes.
(After Leuckart.)

host being absorbed through the body wall. A mature pro-
glottid is almost completely filled with reproductive organs;
these are shown in Figure rio.

The eggs of Tenia solium develop into six-hooked embryos
(Fig. 111, a) while still within the proglottis. If they are then
caten by a pig, they escape from their envelopes (b) and bore
their way through the walls of the alimentary canal into the
voluntary muscles, where they form cysts (c). A head is de-
veloped from the cyst wall (d) and then becomes everted (e).
The larva is known as a bladder worm or cysticercus at this
stage. If insufficiently cooked pork containing cysticerci is
eaten by man, the bladder is thrown off, the head becomes fas-

Igo PRACTICAL ZOOLOGY

Fic. 111. — Stages in the development of a tapeworm.

a, egg with embryo; b, free embryo; c, rudiment
of the head as a hollow papilla on wall of vesicle; d,
bladder-worm (cysticercus) with retracted head; e, the
same with protruded head. (From Sedgwick.)

tened to the wall
of the intestine,
and a series of
proglottides is de-
veloped.

The adult tape-
worms found in
the alimentary
canal of man and
other animals in-
terfere seriously
with the digestion
and absorption of

food, but the larva are more dangerous. For example, the larve
of the tapeworm, Tenia echinococcus (Fig. 112, A), which lives

Fic. 112. — A, an adult hydatid tapeworm.
B, brain of a lamb infested with young gid bladder worms.
C, diagram of part of an hydatid. (After Blanchard.)

THE FLATWORMS 191

as an adult in the dog, may form large vesicles in man, known
to physicians as hydatides (Fig. 112, C), which may break with
serious or even fatal results. The organism which causes “ gid”
or “staggers” in sheep (Fig. 112, B) is the larva of the dog
tapeworm, Tenia cenurus. It becomes lodged in the brain or
spinal cord. Goats, cattle, and deer are also attacked by the
same species.

Characteristics and Classification. — The flatworms belong
to the phylum Platyhelminthes. They are unsegmented like the
roundworms, but can be distinguished from the latter by the
flattened condition of the body. The alimentary canal has only
one external opening, the mouth. Food substances enter the
mouth, and undigested particles are also cast out of this opening.
In the tapeworm there is no mouth at all, the food being absorbed
by the general body wall. All flatworms are hermaphroditic,
since each individual is provided with both male and female
reproductive organs. The parasitic habit of many flatworms
has led to complicated life histories such as that of the liver fluke.

The three classes of the phylum are as follows: —

Class 1. TURBELLARIA. — Free-living animals like Planaria.

Class 2. TReEMATODA. — Parasitic animals like the liver
fluke.

Class 3. CrEsTopa. — Parasitic animals like the tapeworm.

REFERENCES

Cambridge Natural History, Vol. II. — The Macmillan Co., N. Y. City.
Bulletins published by the Bureau of Animal Industry, U. S. Department
of Agriculture.

CHAPTER XXII
THE ECHINODERMS

Tue Echinodermata or “ spiny-skinned animals” are repre-
sented only by marine species. The common names applied to
these animals are starfishes, brittle stars, sea urchins, sand dol-
lars, sea cucumbers, and sea lilies. Echinoderms form quite
a conspicuous part of the fauna of the seashore, but they are
very seldom seen inland except in museums and curio cabinets.
Their structure is very complex and very different from that of
other animals, so much so that the term ‘‘ aberrant ” is often ap-
plied to the group. It will hardly pay us therefore to use much
space in describing them or to spend much time in their study.

Symmetry. — The most notable thing about ‘the echinoderms
is their symmetry. All of the animals that we have studied
thus far are bilaterally symmetrical. Animals are either sym-
metrical or asymmetrical, and the symmetrical animals are
either bilateral or radial.

The bodies of bilaterally symmetrical animals are so con-
structed that the chief organs are arranged in pairs on either side
of an axis passing from the head or anterior end to the tail or
posterior end. There is only one plane through which their
bodies can be divided into two similar parts. An upper or
dorsal surface and a lower or ventral surface are recognizable,
as well as night and left sides. Bilateral symmetry is charac-
teristic of the most successful animals living at the present time,
including all of the vertebrates and most of the invertebrates.

The starfishes and other echinoderms are built on an entirely
different plan. Their bodies are made up of similar parts that
radiate from a central axis; that is, they are radially symmetri-
cal. These parts number in echinoderms either five or a multiple

192

THE ECHINODERMS 193

of five. Radial symmetry is best suited to sessile animals,
since the similarity of the parts enables them to obtain food or
to repel enemies from all sides.

Starfishes. — The starfishes are common along many sea-
coasts, where they may be found usually upon the rocks with

Fic. 113. — A, the oral surface of a starfish.

B, a spine bearing three pedicellarie.
C, tube feet expanded and contracted. (From Cambridge Natural History.)

the mouth down. On the surface are many spines of various
sizes, and on the under side are five grooves, one in each arm,
from which two or four rows of tube feet extend (Fig. 113).
The skeleton is made up of calcareous plates or ossicles bound
together. The arms, however, are not rigid, but they may be
bent slowly by a few muscle fibers in the body wall. The
tube feet are also supplied with muscle fibers.
oO

194 PRACTICAL ZOOLOGY

The water-vascular system is peculiar to’ echinoderms. Sea
water is forced into this system of canals by cilia. The most
interesting structures of the water-vascular system are the tube
feet by means of which the starfish moves from place to place
and holds its food.

The food of the starfish consists of fish, oysters, mussels,
barnacles, clams, snails, worms, Crustacea, etc. When a mussel
is to be eaten, the animal
seizes it with the tube feet
“and places it directly
under its mouth, folding
its arms down over it in
umbrella fashion (Fig. 114).
The muscles which run
around the arms and disk
in the body wall contract
; ; and partially turn the

Fic. 114. — Diagram of starfish eating stomach inside out. The
a mussel. (From Cambridge Natural everted edge of the stomach
History.) ‘

is wrapped round the prey.
Soon the bivalve is forced to relax its muscles and allow the
valves to open. The edge of the stomach is then inserted
between the valves and applied directly to the soft parts of the
prey, which is thus completely digested. When the starfish
moves away, nothing but the cleaned shell is left behind. If
the bivalve is small, it may be completely taken into the
stomach, and the empty shell later rejected through the mouth.

Oyster beds are seriously affected by starfishes. One star-
fish which was placed in a dish containing clams devoured over
fifty of them in six days. Formerly starfishes were taken, cut
in two, and thrown back; this only increased the number, since
each piece regenerated an entire animal. They are now often
captured in a moplike tangle, to the threads of which they
cling. They are then killed in hot water or thrown out on the
shore above high-water mark and left to die in the sun.

THE ECHINODERMS 195

Brittle stars.— The arms of the brittle stars and basket
fish (Fig. 115) are noticeably different from those of the starfish.
They are slender, and exceedingly flexible, but easily broken off ;
hence the name brittle star.

The food of the brittle stars consists of minute organisms

Fic. 115. —A basket star. (From Clark.)

and decaying organic matter lying on the mud of the sea bot-
tom. It is scooped into the mouth by special tube feet. Loco-
motion is comparatively rapid. The arms are bent laterally,
and enable animals belonging to certain species to “run,” or
climb, and probably to swim.

196 PRACTICAL ZOOLOGY

Sea Urchins. — The common sea urchin is almost spherical
in shape, and covered with long spines, from among which the
tube feet extend (Fig. 116). It lives principally on rocky shores,
but it has such relatives as the sand dollars, which are flat like a
silver dollar and bury themselves in the sand.

7 FI SN
IS REIS

Tic. 116. — A sea urchin. (From Clark.)

Sea Cucumbers. — Sea cucumbers (Fig. 117) are so-called
because of their resemblance to the garden vegetables of that
name. They are not hard and spiny like their relatives, but have
a thick, soft body wall. The tube feet around the mouth are
modified as tentacles for obtaining food.

Their food consists of organic particles extracted from the
sand or mud. Some species are said to stretch out their sea-
weedlike tentacles, on which many small organisms come to
rest. ‘‘ When one tentacle has got a sufficient [reight, it is
bent round and pushed into the mouth, which is closed on it.

THE ECHINODERMS 197

It is then forcibly drawn out through the closed lips so that all
the living cargo is swept off.”

Among the South Pacific islands sea cucumbers are known
as ‘‘ béche de mer ” or “ trepang ” and are used for food. The
trade mounts into hundreds of thousands of dollars annually.

Fic. 117. — A sea cucumber. (From Clark.)

Sea Lilies. — The sea lilies or crinoids are now less abun-
dant than the other echinoderms, but were very numerous in
bygone eras, as indicated by their fossil remains so often found
in limestone. They live usually at moderate depths and are
therefore not seen so frequently along the coast.

REFERENCES
Cambridge Natural History, Vol. I. — The Macmillan Co., N. Y. City.
College Zoology, by R. W. Hegner. — The Macmillan Co., N. Y. City.
The Sea Beach at Ebb Tide, by A. F. Arnold. — The Century Co., Nao
City.

CHAPTER XXIII
THE CC:LENTERATES

Tue animals known as corals, jellyfishes, polyps, sea anem-
ones, sea fans, sca pens, and hydroids belong to the phylum
Celenterata. They are all radially symmetrical, like the echi-

widros

Fic. 118. — Hydras attached to water plants. (From Jammes.)

noderms, but very much less complex. Only a few of them live
in fresh water, but one of these, named Hydra, after the myth-
ological nine-headed dragon which was slain by Hercules, is
abundant in ponds and streams, where it may be found at-

tached by one end to aquatic vegetation (Fig. 118).
198

THE CQ@LENTERATES 199

Hydra. — Hydras are easily seen with the naked eye, being
from 2 to 20 mm. in length. They may be likened to a short,
thick thread unraveled at the unattached distal end.

ACTIN = a

Gags

Fic. 119. — Diagram showing the structure of hydra.

b, bud; b.d, basal disk; bl, blastula; ec, ectoderm; en, entoderm; g,
gastrula; gv.c, gastro-vascular cavity; hy, hypostome; m, mouth; mee,
mature egg; m.t, mature testis; mn, nematocysts; p.b, polar bodies; t, tentacle;
y.e, young egg; y.t, young testis. All the structures shown do not occur on a
single animal at one time.

The body is really a tube (Fig. 119) usually attached by a
basal disk (b.d) at one end, and with a mouth opening (m) at

7

200 PRACTICAL ZOOLOGY

the distal or free end. Around the mouth are arranged from six
to ten smaller tubes, closed at their outer end, called tentacles
(4). Both the body and tentacles vary at different times in
length and thickness. One or more buds (6) are often found
extending out from the body, and in September and October
reproductive organs may also appear. The male organs (testes,
Fig. 119, yd) are conical elevations on the distal third of the
body; the female organs (ovaries, Fig. 119, y.e, m.e) are knob-
like projections near the basal disk.

Hasitat. —In spite of their simplicity Hydras are able to
maintain themselves in the same habitat as that of aquatic
insects, fish, frogs, etc., although they often fall a prey to these
animals. When taken out of the water, Hydra shrinks into a
shapeless lump, but when returned to the liquid, it soon becomes
extended and regains its shape. Microscopic examination will
show that its body is not supported by a skeleton of any kind
and therefore must be held up by the water.

PROTECTION. — The protection afforded most animals by an
exoskeleton is secured by Hydra with the aid of stinging organs,
the nematocysts (Fig. 119, 7; 120, B), that lie embedded in the
surface, but are discharged when properly stimulated. Not only
do these nematocysts protect the animal, but they also assist in
capturing food. Ifa hungry Hydra is placed in a small amount
of water containing small Crustacea such as Cyclops (see p.
141, Fig. 81), sooner or later a crustacean will strike a tentacle,
and instead of continuing its progress will stop suddenly as
though shot. And shot it really is, since the contact of its body
with the Hydra’s tentacle was all that was necessary to explode
the nematocysts and paralyze the Cyclops. As soon as the Cy-
clops is captured the other tentacles bend over and help push it
into the mouth.

AcTION OF NeMAtocysts.— The nematocyst acts in the
following manner: Within it there is an inverted coiled, thread-
like tube with barbs at the base. When the nematocyst ex-
plodes, this tube turns rapidly inside out and is able to pene-

THE CCELENTERATES 201

trate the skin of other animals (Fig. 120, B,C, D). The explo-
sion is probably due to internal pressure, and may be brought

Fic. 120. — Parts of the body of hydra highly magnified.

A, two cells containing muscle fibers ; B, two stinging cells or nemato-
cysts; the lower one exploded; C, part of a tentacle showing groups of nema-
tocysts; D, an insect larva shot full of nematocysts ; E, nematocysts coiled
around the spines on limb of a small animal; F, glandular cells from the
basal disk. (After various authors.)

about by various methods, such as the application of a little
acetic acid or methyl green. Many animals when “shot” by
nematocysts are immediately paralyzed and sometimes killed

202 PRACTICAL ZOOLOGY

by a poison called hypnotoxin which is injected into them by
the tube.

Two kinds of smaller nematocysts are also found in Hydra.
One of these is cylindrical and contains a thread without barbs
at its base; the other is spherical and contains a barbless thread
which, when discharged, aids in the capture of prey by coiling
around the spines or other structures that may be present
(Fig. 120, E).

Division or Lazor amMonc CELLS. — From a zoological
standpoint Hydra is of special importance because it is one of
the simplest of all the Metazoa or many-celled animals and gives
us an excellent opportunity to study the division of labor
among the different parts of the body.

The bodies of all complex animals including man are not con-
tinuous masses of the fundamental living substance, the pro-
toplasm, but are broken up into millions of very small parts
called cells. Each cell is separated from every other cell by
means of partitions called cell walls. The term cel/ was first ap-
plied to these units of structure because when they were first
noticed in cork they reminded their discoverers of the cells of
monks in a monastery. These cells of which the bodies of ani-
mals are built up differ in size and shape, but as a rule the size
of the animal depends on the number of cells rather than upon
their size. The body of Hydra contains thousands of these cells
arranged in two layers as indicated in Figure 119.

Tue EctopermM or Hypra. — The outer layer, the ectoderm,
is primarily protective and sensory, and is made up of two prin-
cipal kinds of cells: some are shaped like inverted cones, and
possess long contractile fibrils at their inner ends (Fig. 120, A);
these enable the animal to expand and contract. The others
lie among the bases of these muscular cells; they give rise to
the three kinds of nematocysts or stinging cells and to nerve
cells and germ cells.

THE ENTODERM oF HyprRA. — The entoderm, the inner layer
of cells, is primarily digestive, absorptive, and secretory. The

THE CE@LENTERATES 203

digestive cells are large, with muscle fibrils at their base and
whiplike threads, called flagella, or fingerlike processes, called
pseudopodia, at the end which projects into the central cavity.
The flagella create currents in the central cavity and the pseudo-
podia capture solid food particles. The glandular cells are small
and without muscle fibrils (Fig. 120, F).

Between the ectoderm and entoderm is an extremely thin
layer of jellylike substance called mesoglea.

Digestion. — Digestion takes place in the central or gastro-
vascular cavity (Fig. 119, gv.c) and probably also within the
entoderm cells. The gland cells of the entoderm secrete a
fluid into the gastrovascular cavity. This fluid dissolves the
food. Digestion is aided by the currents set up by the flagella
of the entoderm cells and by the churning resulting from the
expansion and contraction of the body. Part of the food is
evidently engulfed by the pseudopodia of the entoderm cells
and undergoes intracellular digestion. The dissolved food is
absorbed by the entoderm cells; part of it, especially the oil
globules, is passed over to the ectoderm, where it is stored
until needed.

Reproduction. — Hydra reproduces asexually by budding and
by fission, and sexually by the production of eggs and sperma-
tozoa. Budding (Fig. 119, b) is quite common, and may easily
be observed in the laboratory. The bud appears first as a
slight bulge in the body wall. This pushes out rapidly into a
stalk, which soon develops a circlet of blunt tentacles about its
distal end. When full grown, the bud becomes detached and
leads a separate existence.

Fission is less common. The distal end of the animal divides
first; then the body slowly splits down the center, the halves
finally separating when the basal disk is severed.

The processes concerned in sexual reproduction are the pro-
duction of spermatozoa and eggs, the fertilization of the egg,
the development and hatching of the egg, and the growth of the
young larva. The spermatozoa arise in the testis (Fig. 119,

204 PRACTICAL ZOOLOGY

m.f) and escape into the surrounding water. The eggs arise in
the ovary (Fig. 119, y.c) and usually only one egg develops in
a single ovary.

The egg (Fig. 119, m.c) is fertilized by a spermatozoon; it
then divides into a number of cells and is known as an embryo
(Fig. 119, bl; g). The embryo separates from the parent and
falls to the bottom of the pond, where it remains unchanged for
several weeks. At the end of this time the eggshell breaks
away and the embryo escapes. A circlet of tentacles arises
at one end; a mouth appears in their midst; and the young
Hydra thus formed soon grows into the adult condition.

Regeneration. — The power of animals to restore lost parts
was first discovered in Hydra by Trembley in 1744. This in-
vestigator found that if Hydras were cut into two, three, or
four pieces, each part would grow into an entire animal.

Regeneration may be defined as the replacing of an entire
organism by a part of the same. It takes place not only in
Hydra, but in some of the representatives of almost every
phylum of the animal kingdom. Hydra, however, is a species
that has been quite widely used for experimentation. Pieces
of Hydra that measure } mm. or more in diameter are capable
of becoming entire animals.

The benefit to the animal of the ability to regenerate lost
parts is obvious. Such an animal, in many cases, will succeed
in the struggle for existence under adverse conditions, since it
is able to regain its normal condition even after severe injuries.
Physiological regeneration takes place continually in all animals;
for example, new cells are produced in the epidermis of man to
take the place of those that are no longer able to perform their
proper functions. In man, various tissues are capable of re-
generation; for example, the skin, muscles, nerves, blood vessels,
and bones. Lost parts are not restored in man because the
growing tissues do not codrdinate properly.

Division of Labor among Individuals of a Colony. — When-
ever animals live together in colonies, there is almost certain to

THE C@LENTERATES 205

be division of labor among the individuals. This has been
noted in the honeybee (p. 63), where the females of the
colony are of two kinds, queens and workers. Other social
insects, such as ants, wasps, and
termites, exhibit similar differences
among the members of a colony.
Division of labor likewise exists in
communities of human beings, but
the structural differences are not as
great as in many of the, lower ani-
mals. When division of labor oc-
curs among the members of a colony,
the form of the individual is usually
modified so as to be suited to the
function it performs. A colony con-
taining two kinds of members is said
to be dimorphic; one containing
more than two kinds, polymorphic.
Some of the most remarkable cases
of polymorphism occur among the
hydroids. The “ Portuguese man-
of-war”’ (Fig. 121), for example,
consists of a float with a sail-like
crest from which a number of polyps
hang down into the water. Some
of these polyps are nutritive, others
are tactile; some contain batteries

of nematocysts, others are male re- Be. aiden = Tene eases
productive zooids; and still others man-of-war, a colonial ccelen-
: terate. (After Agassiz.)
give rise to egg-producing meduse.
Alternation of Generations. — Most of the relatives of Hydra
live in the sea. Some of them are much branched, plantlike
animals that look like a colony of Hydras attached to acentral
stem. These hydroids are of particular biological interest

because of their method of reproduction. Reference to Figure

206 PRACTICAL ZOOLOGY

122 will make the following description clear. The hydralike
members of the hydroid colony arise asexually by budding and
serve to capture and digest food. Occasionally buds of a dif-

Fic. 122. —A, part of a colonial ccelenterate. 1, ectoderm; 2, entoderm;
3, mouth; 4, cceelenteron; 5, ccenosarc; 6, perisarc; 7, hydrotheca; 8, blasto-
style; 9, medusa-bud; 10, gonotheca.

B, free-swimming medusa: 1, mouth; 2, tentacles; 3, reproductive
organs; 4, radial canals; 5, statocyst.

C, larva (planula). (From Parker and Haswell.)

ferent sort are formed, these undergo a second budding, but
the buds thus produced do not remain attached to the colony.
When they reach their full size, they separate from the parent

THE C@LENTERATES 207

colony and swim away as jellyfish or meduse. The meduse
produce eggs and spermatozoa. The eggs are fertilized by the
spermatozoa, and these fertilized eggs develop into hydroid
colonies. This rather complicated life history is described here
for the purpose of illustrating the phenomenon of alternation
of generations, also known as metagenesis. The asexual genera-
tion is represented by the budding colony; this produces the
medusz, which give rise to germ cells and thus constitute the
sexual generation.

Jellyfish.— Some jellyfishes or meduse belong to the
class Hydrozoa along with Hydra and the hydroids just de-

Fic. 123. — A jellyfish swimming. (From Jammes.)

scribed, but most of them are placed in the class Scyphozoa.
The mesoglea (see p. 203) of these animals is very thick, giving
them a jellylike consistency. Medusz are for the most part
disk-shaped with a fringe of tentacles around the edge and oral
arms hanging down around the mouth (Fig. 123). They swim
slowly about in the sea by means of gentle undulations of the
body.

Sea Anemones. — Sea anemones are cylindrical animals with
a crown of tentacles often so beautifully colored as to resemble

208 PRACTICAL ZOOLOGY

flowers (Fig. 124). They fasten themselves to stones, wharves,
and other solid objects and very seldom move when once fixed.
Small animals are captured by the tentacles as in Hydra and
carried into the mouth.

Coral. — Corals are perhaps the most interesting members of
the phylum Celenterata. Coral polyps live in colonies, and
each member of the colony builds for itself a sort of skeleton

Fic. 124. — Sea anemones. (From Coleman.)

out of calcium carbonate which it extracts from the water.
These skeletons constitute what we call coral.

Coral polyps build fringing reefs, barrier reefs, and atolls.
These occur where conditions are favorable, principally in
tropical seas, the best known being among the Maldive Islands
of the Indian Ocean, the Fiji Islands of the South Pacific Ocean,
the Great Barrier of Australia, and in the Bahama Island
region.

A fringing or shore reef is a ridge of coral built up from the
sea bottom so near the land that no navigable channel exists
between it and the shore. Frequently breaks occur in the reef,

THE C@LENTERATES : 209

and irregular channels and pools are created which are often
inhabited by many different kinds of animals, some of them
brilliantly colored.

A barrier reef is separated from the shore by a wide, deep
channel. The Great Barrier Reef of Australia is over 1100

Fic. 125. — Different kinds of coral.

A, organ-pipe coral; B, dead men’s fingers; C, precious red coral ;
D, sea-pen. (From Sedgwick.)

miles long and incloses a channel from 10 to 25 fathoms deep
and in some places 30 miles wide. Often a barrier reef entirely
surrounds an island.

An atoll is a more or less circular reef inclosing a lagoon.
Several theories have been advanced to account for the produc-
tion of atolls. Charles Darwin, who made extensive studies of

coral reefs and islands, is responsible for the subsidence theory.
P

210 PRACTICAL ZOOLOGY

According to Darwin, the reef was originally built up around an
oceanic island which slowly sank beneath the ocean, leaving the
coral reef inclosing a lagoon.

Besides producing islands and reefs, corals play an important
réle in protecting the shore from being worn down by the waves.
They have also built up thick strata of the earth’s crust.

Fic. 126. — Whitsunday Island in the South Pacific, an atoll built by corals.
(After Darwin.)

Characteristics and Classification. — The ccelenterates are
aquatic animals, mostly marine. They are radially symmetri-
cal, have a single gastrovascular cavity, and are provided with
stinging cells, the nematocysts.

The three classes of coelenterates are as follows: —

Class 1. Hyprozoa.— Fresh-water Polyps, Hydroid Zo-
ophytes, many small Medusz or Jellyfishes, and a few stony
Corals.

Class 2. ScypHozoa.— Most of the large Jellyfishes.

Class 3. ANTHOZOA. — Sea Anemones, most stony Corals,
Sea Fans, Sea Pens, and precious Corals.

REFERENCES
Cambridge Natural History, Vol. I. — The Macmillan Co., N. Y. City.
College Zoology, by R. W. Hegner. — The Macmillan Co., N. Y. City.
The Structure and Distribution of Coral Reefs, by Charles Darwin. — D.
Appleton & Co., N. Y. City.

CHAPTER XXIV
THE SPONGES

TuE ordinary bath sponge is the skeleton of an animal that
lives in the sea. Formerly sponges were considered plants
because of their irregular and plantlike habits of growth, but
their animal nature was finally established about 1857.

The fresh-water sponge lives in ponds and streams and may
be found attached to the undersurface of rocks, dead leaves,
or sticks (Fig. 127, A). It forms incrustations a fraction of an
inch thick, ‘or compact masses, and is gray or green in color.

Unfortunately the fresh-water sponge has a very complicated
structure (Fig. 128, C) and is therefore not suited for laboratory
work.
A Simple Sponge. — Most of the sponges live in the sea, and|
some of these are quite simple. For example, Leucosolenia
(Fig. 127, B), which grows on the rocks just below low-tide mark,
consists of a tube with side branches. The way the various
physiological processes are carried on may be explained by means
of Figure 128, A. One end of the sponge is fastened to the
rock; the other end contains an opening, the osculum (osc).
The cells lining the gastral cavity (G.C) are provided with whip-
like projections called flagella (Fig. 129, D), which beat back
and forth and create a current of water just as do the cilia in
the mussel (see p. 148). This water is drawn in through pores in
the body wall (Fig. 128, p) and passes out through the osculum
in the direction of the arrows shown in the figure. Food par-
ticles are drawn into the gastral cavity with the water and en-
gulfed by the cells. Waste matters pass out through the osculum
suspended in the water. Oxygen is taken in by the body wall

211

212 PRACTICAL ZOOLOGY

and carbon dioxide and other excretory substances are given
off by it.

Sn
Swe

Fic. 127. — Types of sponges.
A, fresh-water sponge; B, a simple colonial marine sponge; C, a simple solitary
marine sponge; D, a bath sponge. (After various authors.)
Reproduction. — New individuals are produced by budding,
by the formation of gemmules, or by means of fertilized eggs.
Gemmules (Fig. 129, C) are little balls of cells that are formed

THE SPONGES 213

in the autumn just before the death of the adult sponge. In the
spring they develop into new sponges. They are of value in

nf,

é Cs €

Fic. 128. — Types of canal systems of sponges.

A, ascon type; B, sycon type; C, rhagon type. The arrows indicate the
direction of the current of water. The thick black line in A and B represents the
gastral layer; the dotted portion, the dermal layer.

ap.p, apopyle ; fi.¢, flagellated chamber; GC, gastral cavity (cloaca) ; in.c, in-
current canal; osc, osculum; pr.p, prosopyle; C, flagellated chambers; DP,
dermal pores; Ex, excurrent canals; GO, openings of excurrent canals; In, in-
current canals; O, osculum; PG, gastral cavity; SD, subdermal cavity. (From
Minchin.)

carrying the race through a period of adverse conditions, such
as the winter season. Only a few sponges reproduce in this way.

Grantia.— A sponge slightly more complex than Leucoso-
lenia is Grantia (Fig. 127, C). Grantia also lives along the coast

214 PRACTICAL ZOOLOGY

attached to rocks just below low-tide mark. Its body wall is
folded as shown in Figure 128, B. This folding increases the
amount of surface of the body wall and consequently the num-
ber of cells. The result is a greater number of flagella, an in-
creased current of water, and more food.

Fic. 129. — Parts of the bodies of sponges.

A, spicules; B, spongin; C, a reproductive body or gémmule; D, collar cells.
(After various authors.)

Flow of Water in Fresh-water Sponge. — The fresh-water
sponge is comparatively complex. Water passes through the
pores (Fig. 128, C, DP) into a cavity (SD) just beneath the
outer wall, then by way of incurrent canals (77) into chambers
lined with flagellated cells (C), and from here through excurrent
canals (x) into the gastral cavity (PG) and out through the
osculum (QO).

THE SPONGES 215

Spicules and Spongin. — The body wall of most sponges is
supported by spicules of calcium carbonate or of silica (Fig.
129, A), and a few like the bath sponge have a skeleton of fibers
consisting of a substance called spongin (Fig. 129, B).

The Relations of Sponges to Other Organisms and to Man. —
Sponges are used as food by very few animals, since they are
protected by spicules and by excretions of poisonous ferments, |

Fic. 130. — Looking for sponges through a glass-bottom pail. (From Bul. U.S.
Fish Com.)

making them distasteful. Nudibranch mollusks (see p. 164)
feed on them to a certain extent.

The cavities of sponges offer shelter to many animals, es-
pecially Crustacea and ccelenterates; this may lead to a sort of
partnership called commensalism. For example, certain hermit
‘crabs protect themselves from attack by surrounding their
shells with obnoxious sponges.

Oysters and other bivalves are often starved by sponges

216 PRACTICAL ZOOLOGY

which cover their shells and take away their food supply. Oys-
ter culturists seek to prevent this by growing the bivalves in
frames which are pulled up during a rain, thus killing the sponges
with fresh water.

The origin of flint is in part due to the activities of sponges.
It has been estimated that to extract one ounce of silicious
spicules at least a ton of sea water must pass through the
canal system of the sponge. The spicules aid in the formation

+ Mime ~ aces

es ee

Fic, 131. — Bringing in a load of sponges. (From Bul. U.S. Fish Com.)

of flint, this substance being always associated with the remains
of sponges and other organisms having silicious skeletons.

Of the commercial sponges, the common bath sponge, Lu-
spongia (Fig. 127, D), is the most important. The best bath
sponges come from the Mediterranean coast, Australia, the Ba-
hamas, Florida, and the north coast of Cuba. They are gathered
(Figs. 130, 131) by means of long hooks, by divers, or by dredg-
ing. They are allowed to decay, are washed, dried, and then
sent to market.

The depletion of the sponge supply by unwise fishing has

THE SPONGES 217

resulted in an attempt to regulate the industry by governmental
control. Sponge culture is now carried on successfully in Italy
and Florida. Perfect specimens are cut into pieces about one
inch square, and “ planted ”’ on stakes on clean, rocky bottoms
free from cold currents. These grow into marketable size in
five or six years.

Characteristics and Classification. — Sponges are mostly
marine animals with bodies that are radially symmetrical but’
often irregular in shape. The body wall is permeated by many
pores, and usually supported by a skeleton of spicules or spongin.
Sponges are separated into three classes according to the com-
position and shape of their skeletal elements.

Class 1. CALCAREA.— With calcareous spicules, like Grantia.

Class 2. HExacTINELLIDA. — With silicious spicules, like
Venus’s Flower Basket.

Class 3. DEmosponcl£. — With silicious spicules or spon-
gin, like the Bath Sponge.

REFERENCES

Cambridge Natural History, Vol. I. — The Macmillan Co., N. Y. City.
Bulletins published by the U. S. Fish Commission.

CHAPTER XXV
THE PROTOZOA

Waat we learned in Chapter [X regarding the minute animals
that cause disease such as malarial fever should be enough to
teach us the importance of the one-celled animals, the Protozoa,
in the affairs of men. Such species as that which causes malaria
are, however, not suitable for laboratory study since they can
hardly be seen even with a compound microscope and are not
available in a living condition. On the other hand, there are
many animals consisting of a single cell which can be procured
in abundance by simply bringing pondweeds or dry hay into the
laboratory, placing it in a shallow dish, covering it with water,
and then allowing it to decay for a few days. The scum that
collects on the surface of such a “ culture” or “ infusion ” will
be found to contain many kinds of Protozoa, and the surround-
ing water will swarm with other species.

Paramecium. — The best species to begin with is the slipper
animalcule, Paramecium caudatum. Paramecia are large
enough to be seen with the naked eye if a proper background is
provided. They are cigar-shaped animals with a depression
called the oral groove (Fig. 132, 0.g) extending from the forward
end obliquely backward. The mouth (m) is situated near the
end of this oral groove.

The motile organs are thin, threadlike cilia which beat back
and forth and propel the animal forward or backward, and draw
food particles into the mouth.

Just beneath the surface is a layer of spindle-shaped cavities
filled with a semifluid substance. These are called trichocysts

218

THE PROTOZOA

(Fig. 132,¢r),and are prob-
ably weapons of offense
and defense. When a lit-
tle acetic acid is added
to the water, they ex-
plode, discharging long
threads.

Foop. — The food of
Paramecium consists prin-
cipally of minute plants
and animals. The cilia
in the oral groove (Fig.
132, 0.g) create a current
of water which forces the
food particles down the
gullet (g). At the end
of the gullet a food vac-
uole (f.v) is produced;
this when fully formed
separates from the gullet
and is swept away by the
rotary streaming move-
ments of the fluid within
the body. This carries
the food vacuole around a
definite course, as shown
by the arrows in Figure
132.

PHYSIOLOGICAL PRo-
cEssES. — Digestion takes
place without the aid of
a stomach.

219

-Fic, 132. — Paramecium viewed from the oral

surface.

L, left side; R, right side.

an, anus; ec, ectosarc; en, endosarc; f.v,
food vacuoles; g, gullet; m, mouth, ma, ma-
cronucleus; mi, micronucleus; 0.g, oral
groove ; p, pellicle; tr, trichocyst layer. The
arrows show the direction of movement of the
food vacuoles. (From Jennings.)

After a food vacuole has become embedded

in the body an acid secretion enters through its walls and dis-
solves part of the food. Undigested particles, the feces, are
ejected at a definite anal spot (Fig. 132, an).

220 PRACTICAL ZOOLOGY

The digested food, together with the water and mineral matter
taken in when the food vacuole was formed, are absorbed by the
surrounding protoplasm, and pass into the body substance of the
animal, no circulatory system being present. These particles
of organic and inorganic matter are then assimilated; that is,
they are rearranged to form new particles of living protoplasm,
which are deposited among the previously existing particles.
The ability to thus manufacture protoplasm from unorganized
matter is one of the fundamental properties of living substance.

The energy for the work done by Paramecium comes from the
breaking down of complex molecules of protoplasm by oxidation
or “ physiological burning.” This is known as katabolism or
dissimilation. The products of this slow combustion are the
energy of movement, heat, secretions, excretions, and the prod-
ucts of respiration.

The acid that is poured into the gastric vacuole by the sur-
rounding protoplasm is of use to the animal and is known as a
secretion.

Materials representing the final reduction of substances in
the process of katabolism are called excretions. These are de-
posited either within or outside of the body. A large part of the
excretory matter passes through the general surface of the body,
but the two contractile vacuoles are also excretory in function.

A contractile vacuole is present near either end of the body.
Each communicates with a large portion of the body by means of
a system of radiating canals, six to ten in number. These canals
collect fluid from the surrounding protoplasm and pour it into
the vacuole. The vacuoles contract alternately at intervals of
about ten to twenty seconds and their fluid contents are dis-
charged to the outside. The contractile vacuoles are also res-
piratory, since carbon dioxide is probably also discharged from
them. Oxygen dissolved in water is taken in through the sur-
face of the body. As in higher animals this gas is necessary for
life.

Tue Nuctevus. —In stained specimens of Paramecium a

THE PROTOZOA 221

highly colored body can be distinguished near the center of the
animal. This is called the nucleus. Every cell possesses a nu-
cleus. Reactions take place between the nucleus and the sur-
rounding protoplasm, and that these reactions are important is
proved by the fact that a cell deprived of its nucleus will not live
very long.

REPRODUCTION. — Paramecium reproduces only by simple
binary division. This process is interrupted occasionally by a
temporary union (conjugation) of two individuals. In binary
fission the nucleus first divides and then the animal is divided
into two by a constriction. The entire process occupies from
about half an hour to two hours. The daughter Paramecia
grow rapidly and divide again at the end of twenty-four hours or
even sooner, depending on the temperature, food, and other ex-
ternal conditions. It has been estimated that one Paramecium
may be responsible for the production of 268,000,000 offspring
in one month.

Sometimes when two Paramecia come together in conjugation,
they remain attached to each other with their ventral surfaces

_ opposed, and a protoplasmic bridge is constructed between them.
As soon as this union is effected, the nuclei pass through a series
of complicated stages, during which part of the nucleus of each
animal passes over into the other. This has been likened to the
process of fertilization in higher animals. Then the two Para-
mecia separate and continue to growand multiply by binary fission.
The causes and results of conjugation are not well understood.

REACTIONS TO STIMULI. — The reactions of Paramecium to
changes in the water are quite interesting. It will swim away
from salt if this is added to the water, but will swim into a drop
of #; per cent acetic acid and stay there. It avoids a high tem-
perature and swims against running water. These reactions
prove that the animal is capable of being stimulated and of re-
sponding to these stimuli. :

Life Activities of One-celled Animals and Many-celled Animals
Compared. — If we now compare the life activities of Parame-

222 PRACTICAL ZOOLOGY

cium with those of the other animals we have studied, we find that
they are similar in nature but are carried out by a single cell.
Paramecium moves about, protects itself, captures food,
digests food, circulates the digested food, assimilates it, pro-
duces secretions, excretes waste products, takes in oxygen,
gives off carbon dioxide, responds to stimuli, and reproduces
itself. The activities mentioned are all fundamental properties

Fic. 133. — Ameba.

1, nucleus; 2, contractile vacuole; 3, pseudopodia; 4, food vacuoles; 5 grains
of sand. (After Gruber.)

of the living substance, protoplasm. In Paramecium they are
performed by a single cell without organs of any kind. In Hydra
they are performed by many cells, and division of labor has taken
place ; that is, some cells are set aside for the performance of one
function and others for other functions.

Ameba. — Ameba is a representative of another type of one-
celled animals. It is only about 4,5 inch in diameter, and is
therefore invisible to the naked eye. Under the compound

THE PROTOZOA 223

microscope it looks like an irregular, colorless particle of ani-
mated jelly. Two regions are distinguishable in its body, the
ectosarc and the endosarc. The ectosarc (Fig. 133, 3) is the
outer colorless layer. It is firmer than the endosarc and is free
from granules. The endosarc is the large central mass of granu-
lar protoplasm. Within it lies the nucleus (Fig. 133, 1), which
is difficult to find in living Amebe, but can easily be made out
in animals that have been properly killed and stained. A con-
tractile vacuole may be seen in favorable specimens.

Foop. — The food of Amebda consists of very small aquatic
plants and animals. The ingestion or taking in of food occurs
without the aid of amouth. Food may be engulfed at any point
on the surface of the body, but it is usually taken in at what may
be called the temporary anterior end; that is, the part of the
body toward the direction of locomotion. A small amount of
water is taken in with the food, so that there is formed a vacuole
whose contents consist of a particle of nutritive material sus-
pended in water. The whole process of food taking occupies
one or more minutes, depending on the character of the food.

PHYSIOLOGICAL ACTIVITIES. — The various physiological ac-
tivities, such as digestion, assimilation, excretion, respiration,
and reactions to stimuli, are similar to those in Paramecium.

Locomotion. — Ameba has no cilia such as cover the body of
Paramecium, and moves in an entirely different way. The
ectosarc bulges out into a fingerlike projection, the pseudopo-
dium (Fig. 133, 3), and then the endosarc flows into it. In this
way the entire animal glides slowly along. There is, however,
no permanent anterior end.

Repropuction. — Reproduction is by binary fission and by a
process known as sporulation. There is a limit with regard to
the size that may be attained by Ameba and when this limit is
reached, the animal divides into two parts. First, the nucleus
divides; then the animal elongates, a constriction appears near
the center, and division into two daughter cells finally takes
place.

224 PRACTICAL ZOOLOGY

Sporulation is apparently a rare process of multiplication
in Ameba. First, the pseudopodia are drawn in and the animal
becomes spherical. By successive divisions of the nucleus from
five hundred to six hundred daughter nuclei are produced. Cell
walls then appear, dividing the Ameba into as many cells as there
are nuclei. These cells break away and
grow into Amebe in about three weeks.

Euglena. — A third type of Protozoon
that may occur abundantly in laboratory
cultures is the little greenish, spindle-
shaped animal known as Euglena (Fig.
134). The principal interests Euglena has
for us are its methods of locomotion and nu-
trition. At the anterior end of Euglena
there is a long, whip-like filament which
bends to and fro, drawing the animal along.
This filament is called flagellum.

For its nutrition, Euglena probably does
not ingest solid particles by means of its
mouth (Fig. 134, m) and gullet, but manu-
factures its own food by the aid of the
green substance (chlorophyll) contained in
it (chr). As in plants, this chlorophyll is

: able, in the presence of light, to break
am, pyrenoid; chr, , pay oh .

chromatophores; ev, down the carbon dioxide, thus setting free
contractile vacuoles; €, the oxygen, and to unite the carbon with

stigma, or eyespot; m, 4
mouth; n, nucleus; r, | water, forming a substance allied to starch,
oe ea (From called paramylum (am). This mode of
nutrition is known as holophytic. Euglena
differs from most animals in its method of nutrition, since the
majority of them ingest solid particles and are said to be holo-

z01c.

Other Fresh-water Protozoa. — Paramecium, Ameba, and Eu-
glena are only three of the more common Protozoa to be found in
- fresh water. A great many others will be seen on the slides

Fic. 134. — Euglena.

THE PROTOZOA 225

prepared in the laboratory, but only a few can be mentioned here.
Two rather common ciliated species are Vorticella and Stentor.
Vorticella is bell-shaped and attached to some object by a con-

Fic. 135. — Types of protozoa.

A, stentor; B, arcella; C, difflugia; D, globigerina, etc., in gray chalk; E, mas-
tigameba. (After various authors.)

tractile stalk. Stentor (Fig. 135, A) is trumpet-shaped and may

be either attached or free-swimming. Some of the amebalike

species are protected by shells. The doughnut-shaped Arcella

(Fig. 135, B) and the pear-shaped Difflugia (Fig. 135, C) are
Q

226 PRACTICAL ZOOLOGY

often found in fresh water, and in the sea the snail-like shells of
Globigerina and many others occur in great abundance (Fig.
135, D). Two common flagellated Protozoa of the Euglena type

D

Fic, 136. — Parasitic protozoa.

A, a cyst of monocystis full of spores; B, a cyst of plasmodium with spores
escaping; C, the germs which cause syphilis; D, entameba which causes
dysentery ; E, the germ which causes sleeping sickness. (After various authors.)

are Mastigameba (Fig. 135, E) and Chilomonas. Mastigameba
looks something like an Ameba with a flagellum at one end.
Chilomonas possesses two flagella.

THE PROTOZOA 227

Parasitic Protozoa. — And now we come to what are the most
important of all Protozoa, the parasitic species. The easiest of
these to obtain for purposes of study is known as Monocystis
and lives in the reproductive organs (seminal vesicles) of the
earthworm. It is about >t of an inch long and moves about
somewhat like an Ameba. A very characteristic stage in its
life history is that of the formation of spores (Fig. 136, A).
Many of these spores are formed by a single animal, and each
spore grows into a full-grown individual. Protozoa that repro-
duce in this way are known as Sporozoa.

The Malarial Parasite. — Perhaps the best-known Sporozoon
is that which causes malarial fever and goes by the scientific
name Plasmodium vivax. An account of how this parasite is
transmitted from one person to another by mosqyitoes has al-
ready been given (Chap. IX, p.’88). The spores when they
are injected into the blood by the bite of the mosquito are
slender, spindle-shaped bodies (Fig. 136, B). Each spore pene-
trates a blood corpuscle, becomes ameboid in shape, and feeds
upon the substance of the corpuscle until it is demolished. The
nucleus then divides several times, forming twelve or sixteen
daughter nuclei, each of which becomes the center of a new spore.
Soon the corpuscle wall breaks and the spores escape. This
breaking down of the corpuscles causes a chill. The new spores
enter other corpuscles and pass through a similar series of stages.

Tf the blood of a malarial fever patient is sucked up by an
Anopheles mosquito, part of the spores become eggs in the stom-
ach of the insect and part of them produce spermatozoa.
The eggs are fertilized by the spermatozoa; the fertilized eggs
become spindle-shaped and bore their way into the wall of the
stomach, where they form little tumorlike swellings. In each
of these a great many spores arise. They break out finally (Fig.
136, B) and make their way imto the salivary glands of the mos-
quito and are then ready to be injected into the blood of another
human being.

Pathogenic Protozoa. — Protozoa that cause diseases, like

228 PRACTICAL ZOOLOGY

the malarial parasite, are said to be pathogenic. Pathogenic
_ Protozoa are all parasitic, living in the alimentary canal, blood,
or other parts of the body. Many of them are known to attack
man and other ‘animals, but there is still a great deal to be learned
about them. Two of the species that cause diseases in domestic
animals are Piroplasma bigeminum, which is responsible for
Texas fever in cattle (see Chap. anes P, 121), and Spirocheta
gallinarum, which attacks poultry. of)

Human diseases that are definitely known; to be caused by
Protozoan parasites or are connected in some way with these
minute germs are malarial fever, yellow fever, syphilis, yaws,
recurrent fever, African tick fever, sleeping sickness, amebic
dysentery, kala azar, hydrophobia, smallpox, and intestinal
catarrh.

AmEBIC DySENTERY. — Minute amebalike organisms, named
Entameba histolytica (Fig. 136, D), are the cause of amebic dysen-
tery, and are always found in the alimentary canal of patients
suffering from this disease.

HYpDROPHOBIA AND SMALLPOX. — Other ameboid organisms
accompany hydrophobia and may destroy the nerve cells of the
brain. In smallpox similar ameboid organisms attack and de-
stroy the epithelial cells of the skin. Whether or not these
structures are the direct cause of the disease mentioned or are
merely accessories is not known, but they are to be looked upon
as dangerous until they are proved to be harmless.

SLEEPING SICKNESS. —-In certain parts of tropical Africa
flagellated Protozoa of the genus Trypanosoma (Fig. 136, E)
cause the disease called sleeping sickness. Trypanosomes are
also parasitic in rats and other animals. The species affecting
man is carried from one person to another by a certain species
of tsetse fly (see p. 99, Fig. 58, A). The parasite, after gain-
ing access to the blood of a human being, multiplies with remark-
able rapidity. The nervous system of the patient is affected
either directly or by a poison secreted by the parasites. The
disease may last several months or even years. Irregular fever

THE PROTOZOA 2209

soon follows infection, and later general debility sets in. The
victim exhibits an increasing tendency to sleep, gradually wastes
away, and finally dies.

YELLOW Frver.—- As stated in Chapter IX (p. 86) we do
not know what is the cause of yellow fever, but it is doubt-
less a germ of some kind, probably similar to the malarial fever
parasite.

SPIROCHATES. — Spirochetes are corkscrew-shaped organ-
isms about z3'55 of an inch long (Fig. 136,C). They are usually
considered Protozoa, but their exact nature is not certainly
known. Many of the most terrible of all diseases are caused by
these minute living things.

Yaws is a disease of the tropics characterized by the presence
of ulcerating sores on various parts of the body. It is caused
by Spirocheta pallidula.

SYPHILIS likewise causes ulcerating sores. The organism re-
sponsible for this disease has been known for only a few years.
It is Spirocheta pallida. Recently a drug known as dichlorhy-
drate-diamido-arseno-benzol has been discovered which seems
to be an absolute cure for the disease.

RELAPSING or RECURRENT FEVER (see p. ror) occurs.in some
parts of Europe. Another spirochete, Spirocheta obermeieri,
is the organism that causes it.

Kara Azar or DumpuM FEVER (see p. 100) is a chronic dis-
ease in many parts of Asia and about the Mediterranean Sea.
It is characterized by irregular fever, an enlarged spleen, and
emaciation. The parasite that causes it is known as Leish-
mania donovant.

Control of Pathogenic Protozoa. — All of the diseases caused
by pathogenic Protozoa are difficult to cure, and it is therefore
important that their infectious nature be understood by every
one, so that healthy people will not carelessly expose them-
selves and that diseased individuals will be careful not to dis-
tribute the parasites. Many of the protozoan parasites are
transmitted by insects or mites and ticks, and methods of con-

230 PRACTICAL ZOOLOGY

trolling these germ carriers have been described in Chapters
VIII, IX, X, and XIII. The control of the other diseases is
largely a matter of care and cleanliness.

Protozoan Parasites of Domestic Animals. — The most im-
portant disease of domestic animals caused by a protozoon in this
country is the Texas fever of cattle, described in Chapter XIII
(p. 121). Besides this parasite there are a number of different
species of trypanosomes, similar to that which causes sleeping
sickness in man, that produce diseases in cattle, horses, and
other domestic animals in various parts of the world.

The silkworm disease, pebrine, which appeared in the south
of France at about the middle of the nineteenth century is
“especially interesting because of the fact that Pasteur’s studies
revealed its cause and devised methods for its control, thus pav-
ing the way for the control of infectious diseases in man. Pas-
teur advised the silkworm raisers to destroy all diseased cater-
pillars and eggs and to raise silkworms only from eggs that were
free from parasites. This advice was followed and resulted in
freeing the silk industry in France from the disease. The para-
site is known as Nosema bombycis.

Protozoa in Drinking Water.— Our drinking water comes
from three main sources. Rain water is pure except for the
organisms that the rain drops gather in the air. Ground water,
which comes from springs, wells, and infiltration basins, is usually
free from Protozoa. Surface water from streams, lakes, ponds,
and reservoirs contains more Protozoa than either rain water or
ground water, and standing water is, as a rule, more crowded
with them than running water.

The organisms that float passively in the water without seek-
ing the shore or bottom constitute a group known as plankton.
An examination of the waters of a typical river (the Illinois
River) revealed 528 different species of plankton. These were
mostly plants (alge), Protozoa, wheel animalcules, and Ento-
mostraca (see p. 144). One hundred and eighty-five of the
528 species recorded were Protozoa, and every cubic meter of

THE PROTOZOA 231

water contained an average of 112,000,000 protozoan individ-
uals (Kofoid).

The numbers of Protozoa in different kinds of water are in-
dicated by the following statistics (Whipple).

A flowing brook contained ro per cubic centimeter.

A reservoir contained 97 per cubic centimeter.

A pond contained 666 per cubic centimeter.

The trouble caused by the Protozoa is chiefly due to their odor
and taste. Besides this, Protozoa may cause temporary intes-
tinal disorders in people not accustomed to a certain kind of
water. On the other hand, some Protozoa undoubtedly aid in
purifying water of Bacteria; for example, the flagellate Bodo
greatly reduces the number of typhoid fever germs by using
them for food.

Some of the common species of Protozoa that cause trouble are
Uroglena (Fig. 137, A), which has a fishy or oily odor; Synura,
with an odor of ripe cucumbers and a bitter and spicy taste; and
Bursaria, with an odor resembling that of a salt marsh.

The water in reservoirs may be purified by the use of copper
sulphate (blue vitriol). About one part of copper sulphate to
from five to twenty million parts of water should be used. This
should be placed in a bag and dragged through the water behind
a boat until all is dissolved and thoroughly distributed. Copper
sulphate is poisonous, but the amount used is so small as to be
harmless.

Colonial Protozoa. — Protozoa are said to be one-celled ani-
mals, but many species live more or less firmly fastened together
in groups or colonies. In some cases the members of the colony
are rather loosely united, as in Carchesium, a near relative of
Vorticella, which occurs in groups fastened together by thin
stalks. Other species may consist of many members embedded
in a gelatinous matrix, such as Uroglena (Fig. 137, A), a relative
of Euglena.

Votvox. —In one species, Volvox globator (Fig. 137, B), the
members of the colony are connected with one another by strands

232 PRACTICAL ZOOLOGY

of protoplasm. Volvox is particularly interesting because it
illustrates very clearly the division of labor between cells that
. are set aside for reproduction, the germ cells, and those that
carry on the rest of the activities
of the animal, the body cells or
somatic cells. Certain repro-
ductive cells of the Volvox
colony grow very large, divide
into a number of cells, and thus
form new colonies. Other re-

productive cells increase in size,
some of them becoming eggs, and
others dividing to form many
spermatozoa
(Fig. 137, B, 3
and @). The
eggs are fer-
tilized by the
spermatozoa,
and after a
period of rest
develop into
new colonies.
The new col-
onies thus
formed escape
from the par-
ent colony and
continue the
race, whereas

Fic. 137. — Colonial protozoa.
A, uroglena; B, volvox. (After Kélliker.) the old col-
onies die a nat-

ural death. It is evident that unless germ cells were formed
the Volvox race would soon disappear, and it is also clear that
there is here a continuity of germ cells from one generation to

THE PROTOZOA 233

another; that is, the germ cells of one generation, the parent
colony, survive to produce the body and germ cells of the
daughter colonies. A distinction between germ cells and body
cells can be made in all the higher animals including man, and,
as in Volvox, the parents produce germ cells (eggs and_ sper-
matozoa) which give rise to the body and germ cells of the young.

Characteristics and Classification. — Protozoa are one-celled
animals which in many cases form colonies. They live in fresh
water, salt water, damp earth, and as parasites in or on the
bodies of other animals. They vary in shape from the shapeless
Ameba to the highly organized Vorticella. Locomotion takes
place by means of cilia and pseudopodia. The various physio-
logical processes occur in Protozoa just as they do in higher or-
ganisms, but within a single cell and without definite organs.

The Protozoa are separated into classes according to the pres-
ence or absence of locomotor organs and the character of these
when present. Four classes are usually recognized: —

Class1. RutIzopopa. — With pseudopodia, as in Ameba.

Class 2. MasticopHora. — With flagella, as in Euglena.

Class 3. Sporozoa.— Without locomotor organs in adult
state. Produce spores, as in malarial parasite.

Class 4. InFusortIA. — With cilia, as in Paramecium.

REFERENCES

The Protozoa, by G. N. Calkins. — The Macmillan Co., N. Y. City.

Protozoology, by G. N. Calkins. — Lee, Febiger and Co., Philadelphia.

Introduction to the Study of the Protozoa, by E. A. Minchin. — Edward
Arnold, London, England.

CHAPTER XXVI
AN INTRODUCTION TO THE VERTEBRATES

THE animals that remain to be discussed all belong to the
phylum of back-boned creatures, the Vertebrata. There are
only about thirty thousand species of these as compared with
over four hundred thousand Invertebrates, but their large size
and intimate relations with man make them of comparatively
greater importance. Unlike the invertebrates, the vertebrates
are well known to us, although there are many of them that never
come within our ordinary, everyday experiences. The verte-
brates may be divided into five classes, which are as follows,
beginning with the lowest forms: —

Class 1. Pisces. — Fishes (Fig. 138, A and B).

Class 2. AmpuipiA. — Frogs, Toads, and Salamanders (Fig.
138, C and D).

Class 3. Reptitia. — Lizards, Snakes, Crocrodiles, and Tur-
tles (Fig. 138, E and F).

Class 4. Aves. — Birds (Fig. 138, G).

Class 5. Mammaria.— Hairy Quadrupeds, Whales, Seals,
Bats, Monkeys, and Man (Fig. 138, H).

Most of us have seen examples of all these different classes
of vertebrates. The horse is a typical mammal; the hen or
pigeon a typical bird; the snake, turtle, and crocodile typical
reptiles; the frogs and toads typical amphibians, and fish are, of
course, a common article of food. Although we thus have an idea
of the different types of vertebrates, they are mostly domesti-
cated animals, and we do not see very many different kinds of
wild vertebrates unless we are fortunate enough to live where
there are aquaria containing fish and other aquatic animals, or

234

AN INTRODUCTION TO THE VERTEBRATES 235

Fic. 138. — Types of vertebrates.

A, a cyclostome (eel); B, a fish; C, an amphibian (frog); D, an am-
phibian (salamander); E, a reptile (lizard); F, a reptile (turtle) ; G, a bird;
H, a mammal (armadillo). (From various authors.)

236 PRACTICAL ZOOLOGY

zoological gardens with living wild animals, or museums with
exhibits of stuffed animals. Many of us have had a chance to
see a few different kinds of wild creatures in circuses and have
therefore some idea of their appearance.

According to some authorities we should not study any ani-
mals that we cannot see in the laboratory, but while it is cer-
tainly true that we remember what we see better than what we
read about, still we can obtain by means of descriptions and pic-
tures rather accurate ideas of animals we have never seen on the
basis of what we know of familiar creatures. In the same way
does our knowledge of the lakes, rivers, and creeks, the hills and
the plains enable us to study intelligently similar forms in
Africa and other foreign lands which we have never seen. It is,
therefore, the plan of our discussion of the classes of verte-
brates to point out first the peculiarities in the structure of the
animals which adapt them to their surroundings, and then with
the aid of pictures to describe a few of the more important mem-
bers of each class.

The activities of these different groups of vertebrates are often
very diverse, and the structures that adapt them to their differ-
ent habitats are quite varied; nevertheless the plan of structure
is similar in all. The best example of the vertebrates that is
small enough to be used conveniently in the laboratory, and that
can be obtained for large classes without prohibitive labor and
expense, is undoubtedly the frog. Fish answer these require-
ments also, but their construction differs more widely from that
of man than does the anatomy of the frog. It is desirable that
we learn as much as possible about man from our study of the
lower animals, and the best method of beginning is to study the
most available vertebrate, comparing its structures and physio-
logical processes with those of human beings. The frog will
therefore be discussed quite fully in the succeeding chapter.

The Body as a Machine. — The body of a vertebrate, such as
the frog or man, may be considered a sort of machine consisting
of many complex parts. There are, of course, many differences

AN INTRODUCTION TO THE VERTEBRATES 237

between a living animal and a machine like a clock, but just as
a boy takes a clock apart to see what makes it go, so if we wish to
know what enables an animal to perform its various activities,
we must dissect it and examine its various parts.

Organs and Systems of Organs. — The principal parts of an
animal, such as the eye, the stomach, or the arm, we call organs.
Many organs are usually necessary for the performance of a
single function; for example, the proper digestion of food in a
complex animal requires a large number of organs collectively
known as the alimentary canal and its appendages. These
organs constitute the digestive system. Similarly, other sets of
organs are associated for carrying on other functions. The
principal systems of organs and their chief functions are as
follows: —

(1) Digestive system — Digestion and absorption of food.

(2) Circulatory system — Transportation of food, oxygen,
and waste products.

(3) Respiratory system — Taking in oxygen and giving off
carbon dioxide.

(4) Excretory system — Elimination of the waste products
of metabolism.

(5) Muscular system — Motion and locomotion.

(6) Skeletal system — Protection and support.

(7) Nervous system — Sensation and correlation.

(8) Reproductive system — Reproduction.

(1) The digestive system has for its functions the changing
of solid food into liquids and the absorption of these liquids into
the blood. This system consists usually of a tube, the alimen-
tary canal, with an opening at either end of the body. Con-
nected with this tube are a number of glands. Solids taken in
as food are usually broken up in the mouth, where they are mixed
with juices from the salivary glands; the mixture then passes
through the cesophagus into the stomach, where chemical diges-
tion, aided by secretions from the gastric glands, takes place;
it then enters the intestine, which absorbs the dissolved material

238 PRACTICAL ZOOLOGY

through its walls. Undigested solids travel’ onward into the
rectum and are cast out through the anus as feces.

(2) The circulatory system transports the absorbed food to all
parts of the body. It also carries oxygen to the tissues, and
carbon dioxide and other waste products away from the tissues.
These substances are transported by fluids called blood and
lymph, which are usually confined in tubes, the blood vessels,
and in irregular spaces known as sinuses. The blood consists of
a plasma and corpuscles. It is forced to the various parts of the
body by the contractions of a muscular organ called the heart.

(3) The respiratory system takes in oxygen (inspiration) and
gives off carbon dioxide (expiration). In many animals, like
the earthworm, the oxygen and carbon dioxide pass through the
moist surface of the body, but in higher animals there is a special
system of organs for this purpose. Aquatic animals usually
possess gills which take oxygen from the water. Terrestrial
animals generally take air into cavities in the body, such as the
lungs of man and the trachez of insects.

(4) The excretory system is necessary for the elimination of
waste products which are injurious to the body. These waste
products result from the oxidation of the protoplasm. Various
names are applied to the organs of excretion, such as nephridia
and kidneys.

(5) The muscular system enables animals to move about in
search of food and to escape from their enemies. Many animals,
like the oyster, have the power of motion, but not of locomotion.
The muscles would be of slight efficiency were it not for the hard
skeletal parts to which they are attached and which serve as
levers.

(6) The skeletal system is either external (exoskeleton) or
internal (endoskeleton). The hard shell of the crayfish is an
example of an exoskeleton; the bones of man form an endoskele-
ton. In either case the skeleton not only supports and protects
certain soft parts of the body, but it also provides places for
the attachment of muscles.

AN INTRODUCTION TO THE VERTEBRATES 239

(7) The nervous system in higher animals consists of two
parts: (a) central and (8) peripheral. The brain and spinal
cord constitute the central nervous system. The organs of
special sense, such as sight, smell, taste, hearing, touch, tempera-
ture, and equilibrium, and the nerves connected with them, and
all other nerves connecting the central nervous system with
various parts of the body, constitute the peripheral nervous
system. Efferent (motor) nerve fibers conduct impulses from
the brain and nerve cord to an active organ like a muscle or
gland. ;

(8) The reproductive system consists of the germ cells, and
the organs necessary for furnishing yolk and protective envelopes,
and for insuring the union of the eggs and spermatozoa. The
essential reproductive organs in complex animals are usually
the ovaries, which contain the eggs, and the testes, in which the
spermatozoa ripen. The accessory organs are generally ducts
..leading to the exterior, glands connected with these ducts, and
organs for transferring the spermatozoa from the male to the
female.

Structure of Organs. — We cannot understand how an organ
performs its duty unless we have a knowledge of the structure
of the organ. We shall not attempt to learn all there is known
about organs, but just enough to understand their activities. In
the first place the entire body, as previously stated (p. 202), is
either a single cell (Protozoa, p. 218), a colony of cells (colonial
Protozoa, p. 231), or a many-celled organism with the cells
closely bound together (Metazoa). We have seen how the vari-
ous physiological processes are performed by a single cell (Fig.
139), as in Paramecium (p. 218), and also how in many-celled
animals like Hydra (p. 202) groups of cells are set aside for
carrying on different functions, that is, division of labor has
taken place. This is true of all many-celled animals.

Protoplasm. — The substance of which every cell is com-
posed is called protoplasm. As in Paramecium (p. 219) every
cell contains a central body, the nucleus. The nucleus is a

240 PRACTICAL ZOOLOGY

specialized kind of protoplasm; it is sometimes called nucleo-
plasm to distinguish it from the rest of the protoplasm, which
is designated cytoplasm.

PROTOPLASM THE PuysicaL Basts or Lire. — Protoplasm is
known as the physical basis of life since every organism, whether

Fic. 139. — Diagram of a typical cell.

as, astrosphere; c, centrosome; ch, chromatin; cr, chromidia; ec, ecto-
plasm; en, entoderm; k, karyosome; 1, linin; m, mitochondria; me, meta-
plasm; nm, nuclear membrane; p, plastid; pl, plasmosome or nucleolus;
s, cytoplasm; v, vacuole.

plant or animal, has this substance as a basis. We should there-
fore know something more about it. Ameba (Fig. 133) consists
of naked protoplasm. The outer layer is very clear, and rather
firm like stiff jelly; the inner mass is granular and more watery.
The activities of Ameba are those of animals in general, but in
the Melazou these activities are distributed among many cells, a
condition known as division of labor among cells or specializa-
tion.

AN INTRODUCTION TO THE VERTEBRATES 241

THE FUNDAMENTAL PROPERTIES OF PROTOPLASM. — The
fundamental properties exhibited by Ameba are : —

(1) Irritability, the ability of responding to changes in the
surroundings.

(2) Contractility, as indicated by the changes in the shape of
the body.

(3) Metabolism, that is, the change of food into protoplasm
and the use of this protoplasm to furnish energy — processes
that involve digestion, absorption, circulation, assimilation,
oxidation, secretion, and excretion.

(4) Growth, which is the result of an excess of the building-
up process (anabolism) over the breaking-down process (katab-
olism) ; and

(5) Reproduction.

These are not only fundamental properties of Ameba, but of
protoplasm in general.

Composition OF PRroTopLtasm.— The substances of which
protoplasm is composed are chiefly oxygen, carbon, hydrogen,
and nitrogen. These substances do not differ from those in
lifeless bodies but they are so combined as to form. the peculiar
substance protoplasm which occurs only in living things.

Tissues. — The division of labor among the cells of the many-
celled animals has resulted in changes in the size, shape, and
structure of the cells. For example, muscle cells are the agents
of active movement and therefore their contractile powers are
strengthened and their other properties correspondingly weak-
ened. Groups of cells that are associated for the performance
of certain functions are called tissues. We have already noted
in the case of Volvox (p. 231) the distinction between the repro-
ductive or germ cells and the somatic or body cells, and have
seen that the reproductive cells are of two kinds, female cells or
eggs (Fig. 140, A) and male cells or spermatozoa (Fig. 140, B).

Kinps or Tissues. — The body cells form tissues of many
kinds, but these can be classified according to their functions and

structure into four groups :—
R

242 PRACTICAL ZOOLOGY

(1) Movements are performed by muscular tissue. This
tissue is made up of muscle cells, either voluntary or involun-
tary. The voluntary muscle cells form muscles that are con-
trolled by the will of the animal; they are cross-striated (Fig.
140, FE). Involuntary muscles cannot be controlled; they are
smooth and non-striated (Fig. 140, F).

(2) The perception of changes in the surroundings and the
conduction of impulses are functions of nervous tissue. Nerve
cells are peculiar structures consisting of a nucleated central
body, from which branches and nerve fibers extend (Fig. 140, G).
These nerve fibers may be several feet in length, extending, for
example, from the lower part of the backbone in man to the toes.

(3) The various parts of the body are bound together by
connective tissues, such as tendons, and held upright and pro-
tected by supporting tissues, such as bone and cartilage (Fig.
140, D). The substances in these tissues are largely of non-
living fibers, plates, and masses produced by living cells.

(4) The body surface and the surfaces and linings of organs
are composed of epithelial tissues. The epithelial tissues cover-
ing the body serve as a protection, and contain nerve endings,
glands, hairs, etc. (Fig. 140, C).

Living and Lifeless Things. — Living things differ from life-
less things in being

(1) of definite size, and not of any size like water which may
exist as a particle of vapor or as an ocean;

(2) of definite form, and not of varied form like water,

(3) of definite organization into cells ;

(4) capable of growth by the addition of new particles among
preéxisting particles ;

(5) able to reproduce others of their kind; and

(6) able to move. The movement of a thing is usually
enough to indicate that it is alive, but many living things, such
as a hen’s egg, are unable to move ; hence in many cases we must
consider the other five characteristics first listed in order to de-
termine whether a thing is alive or not.

AN INTRODUCTION TO THE VERTEBRATES 243

D

Fic. 140. — Various kinds of cells.

A, female germ cell, ovum of a cat; B, male germ cell, spermatozoon of a
snake; C, ciliated epithelium; D, cartilage; E, striated muscle fiber; F,
smooth muscle fibers; G, a nerve cellfrom the cerebellum of man. (From
Dahlgren and Kepner.)

244 PRACTICAL ZOOLOGY

The Ofigin of Life. — Scientists have speculated for centuries
regarding the place where life originated upon the earth. Ac-
cording to the theory of spontaneous generation animals were
supposed to originate directly from inorganic substances; for ex-
ample, frogs and toads from the muddy bottom of ponds under the
influence of the sun, and insects from dew. The brilliant experi-
ments of Redi (1668), Pasteur (1864), and Tyndall (1876) over-
threw this theory completely, and scientists now believe that
living organisms originate only from preéxisting organisms.
Where life first began is still unknown, but the meeting point of
sea and land is the most probable place of origin. From here the
fresh water, deep sea, and land were gradually peopled.

This general view of protoplasm, cells, tissues, organs, and
systems of organs will make more intelligible the discussion of the
life processes of the frog presented in the next chapter.

REFERENCES

Comparative Anatomy of Vertebrates, by J. S. Kingsley. —Henry Holt and
Co., N. Y. City.

The Cell, by E. B. Wilson. — The Macmillan Co., N. Y. City.

Histology, by Dahlgren and Kepner. — The Macmillan Co., N. Y. City.

College Zoology, by R. W. Hegner. — The Macmillan Co., N. Y. City.

CHAPTER X XVII
THE FROG, A TYPICAL VERTEBRATE

Frocs live in or near fresh-water lakes, ponds, and streams,
and are distributed over the entire North American continent
as well as in other parts of the world. Frogs have many
enemies, being preyed upon by snakes, turtles, cranes, herons,
other frogs, and man. They have no means of protection and
must therefore remain concealed from their enemies or escape
by rapid locomotion. Those who have looked for frogs amid the
water plants in a pond or in the grass and rushes along the banks
of streams will readily admit that their colors effectively conceal
them from view. If they are approached too closely, they have
an excellent refuge, the water, into which their hind legs quickly
propel them. As is the case with the snails, the skin of the frog
is naked and covered with mucus which impedes evaporation.
Because of this naked skin frogs must live in very damp places
or near enough to water so that they can take a plunge occasion-
ally or else their skins will become dry and they will perish.

Movements. — The ordinary movements of the frog are
those employed in leaping, diving, crawling, burrowing, and
maintaining an upright position. Some of these movements
are due to internal causes such as hunger, but many of them are
the responses to external stimuli. Frogs are sensitive to light,
and tend to congregate in shady places. They also seem to be
stimulated by contact, as shown by their tendency to crawl
under stones and into crevices.

The frog leaps on land and swims in the water. The hind
legs are large and powerful. When the frog is on land, the
hind legs are folded up, and a sudden extension propels the

245

246 PRACTICAL ZOOLOGY

body through the air. Likewise in swimming the hind legs are
alternately folded up and extended, and during their backward
stroke the toes are spread apart so as to offer more resistance to
the water. Frequently frogs float on the surface with just the
tip of the nose exposed and with the hind legs hanging down. If
the frog is disturbed in this position, the hind legs are flexed, a
movement which withdraws the body, the fore legs direct the frog
downward, and the hind legs are extended, to complete the dive.

Croaking. — Frogs croak most during the breeding season, but
they are heard also at other times of the year, especially in the
evening or when the atmosphere becomes
damp. Croaking may take place either in
air or under water. In the latter case the
air is forced from the lungs, past the vocal
cords, into the mouth cavity, and back
again.

Physiological Processes. — The physio-
logical processes of the frog will be consid-
ered in the following order: (1) digestion,
(2) absorption, (3) assimilation, (4) circu-
lation, (5) respiration, (6) excretion, (7) se-
cretion, (8) the skeleton and its functions,
(g) muscular activity, (10) nervous activ-
ity, (11) sense organs, (12) reproduction.

Fic. 141.— Diagrams DicEsTIoN. — The worms and insects
ee ae used as food by the frog are captured by
an insect is captured. its sticky tongue (Fig. 141) and drawn into
ae Nat- the mouth by this organ or pushed in with

the forefeet. The conical teeth that are
present in the upper jaw do not masticate the food as do man’s,
but simply hold it. In man the salivary glands add their secre-
tions to the food as it is being masticated and this saliva con-
verts the starch in the food into sugar. There are no salivary
glands in the frog and hence this process of salivation is entirely
omitted.

THE FROG, A TYPICAL VERTEBRATE 247

Food passes from the mouth through the tubelike esophagus
into the stomach (Fig. 142, M). The walls of the stomach are
thick and muscular and contain a great many glands for the
secretion of gastric juice. These glands are stimulated by the
presence of food, and the gastric juice they secrete acts upon the

Fic. 142. — Internal anatomy of the frog.

B, bladder; D, intestine ; E, ovaries; H, heart; L, liver; Lg, lungs; M, stomach.
(From Ecker.)

food particles in such a way as to dissolve them. This solution
of food material in preparation for absorption is the object of
digestion.

The food next passes into the intestine where the pancreatic
juice from the pancreas, and the bile, which is stored up by the

248 PRACTICAL ZOOLOGY

liver in the gall bladder, are added to it. Both the pancreatic
juice and bile aid in dissolving the food, and they are helped
more or less by secretions from glands in theintestinal wall. The
movements of the food through the alimentary canal are due
chiefly to what are called peristaltic waves ; the circular muscles
in the walls relax ahead and contract behind, thus forcing the food
along.

ABSORPTION. — The digested food passes into the cells of the
intestinal wall, where it is more or less changed, and then trans-
ferred to the blood or lymph. This is the process of absorption.
Very little is known about absorption in the frog. In human
beings the absorbed food, part of it having passed through the
liver, is carried to the heart, whence it is pumped through the
body.

ASSIMILATION. — The extraction of the digested food from the
blood stream by the cells of the body, and the formation of new
protoplasm with it, constitute the process of assimilation. Life-
less things cannot grow in this way, but must increase in size by
the addition of substances on the outside.

CircuLation. — The blood which circulates throughout the
body carries the digested food and distributes it to the cells,
bears oxygen from the breathing organs to the tissues and carbon
dioxide away from the tissues to the breathing organs, and trans-
fers waste products from all parts of the body to the excretory
organs.

Blood is a fluid containing red corpuscles and white corpuscles.
The red corpuscles owe their color to the presence of hemoglobin.
This substance combines with oxygen in the breathing organs
and gives it out again to the tissues. The white corpuscles re-
semble Ameba in shape and are hence said to be ameboid. They
act as scavengers, engulfing foreign bodies such as germs and
broken-down tissues that may find their way into the blood
stream.

The discovery that the blood circulates was made by an English
physician, William Harvey, in 1621. Since then it has been

THE FROG, A TYPICAL VERTEBRATE

249

shown that the entire blood supply passes from the heart through-
out the body and back again to the heart in from twenty to thirty

seconds. This means that
the six quarts of blood in
the body of a man pass
three or four thousand
times per day throughout
the tissues of the body.
The heart (Fig. 143) of
the frog is a conical organ
consisting of a muscular
ventricle and two thin-
walled auricles. In man
there are two ventricles
instead of one. Tubes,
the arteries, carry the
blood from the heart to
the tissues, and others,
the veins, carry it back to
the heart. The muscular
ventricle by its contrac-
tions forces blood into the
arteries. The walls of the
arteries are elastic and
by their pressure force
the blood along until it
reaches the finest of all
the blood tubes, the cap-
allaries. The capillaries
unite the ends of the ar-
teries with the ends of the
veins and the blood from
the former passes through
them into the veins and
thence back to the heart.

Fic. 143. — Diagram of the arterial system of
the frog, ventral view.

ao’’, aortic arch; au’, right auricle; au’’,
left auricle; br, brachial artery; c.c, carotid;
c.gl, carotid gland; c.il, common iliac; ce,
coeliaco-mesenteric; coe’, coeliac; cu, cuta-
neous; d.ao, dorsal aorta; fm, femoral; g,
gastric; h, hcemorrhoidal; hp, hepatic; hy,
epigastrico-vesical; k, kidney; 1, lingual;
1g’’, left lung; m, anterior mesenteric; mii,
posterior mesenteric; oc, occipital ; pe’, pan-
creatic; p.cu, pulmocutaneous; pul, pulmo-
nary; re, renal; sc, sciatic; sp, splenic; tr.a,
truncus arteriosus; ts, testis; v, vertebral.
(After Howes.)

250 PRACTICAL ZOOLOGY

The movement of the blood through capillaries can be observed
very easily in the web of the frog’s foot.

Part of the blood of the frog is forced by the heart into the
lungs (Fig. 143, /g’’), where it gets rid of carbon dioxide and re-
ceives oxygen. Another part of the blood is carried to the
kidneys (Fig. 143, &) and is there relieved of its waste products.
The blood returning from these and other organs is carried either
through the liver to the right auricle or directly to this auricle,
with the exception of that from the lungs, which enters the left
auricle. From the auricles the blood is sucked through valves
into the ventricle when this muscular portion expands after a
contraction.

There are many spaces in the frog’s body filled with a colorless
fluid called lymph, which contains colorless corpuscles. Lymph
passes from one space into another, enters the blood, and it is
always gently flowing over the tissues, thus aiding the blood in
the performance of its functions.

RESPIRATION. — By respiration is meant the transfer of oxy-
gen from the air to the blood and from the blood to the cells of
the body, and of carbon dioxide from the cells to the blood and
from the blood to the air. We are accustomed to consider breath-
ing as the act of respiration, but this is only external respiration
and not so essential as the zuternal respiration of the cells.

In the frog, respiration takes place to a considerable extent
through the skzm, both in water and in air, but it is carried on
principally by the lungs (Fig. 142, L, L’). During inspiration
air passes through the nostrils into the mouth cavity. The
nostrils are then closed and the air is forced through a slit, the
glottis, into a short tube, the larynx, and thence into the lungs.
Air is expelled from the lungs (expiration) into the mouth
cavity by the contraction of the muscles of the body wall.

The lungs are pear-shaped sacs with thin, elastic walls. The
area of their inner surface is increased by folds which form minute
chambers called alveoli. Blood capillaries are numerous in the
walls of these alveoli.

THE FROG, A TYPICAL VERTEBRATE 251

In an average human being the lungs can hold about 330 cubic
inches of air, but at each inspiration only about 30 cubic inches
of this is renewed. The fresh air drawn in differs from the ex-
pired air as follows :—

C. BK
| OxyGEN NITROGEN Dot WatTER
Inspired air 20.96 % 79.00 % 0.04 % Trace
Expired air 16.02% 79.00 % 4.38% 0.60%

The inspired air therefore loses oxygen, which is nearly re-
placed in expired air by carbon dioxide. This change is due to
the passage of oxygen from the hemoglobin in the red blood cor-
puscles, and the transference of carbon dioxide from the blood
corpuscles into the lung cavities. The oxygen obtained by the
blood in this way is carried to the tissues and delivered to the
cells.

We may explain why the cells must have oxygen as follows:
Every action of an animal uses up part of the protoplasm in the
body, and just as coal furnishes the power for the work done by
a steam engine so food supplies the protoplasm for doing the
work of the animal. The breaking down of the protoplasm is
caused by the union of oxygen with it, producing a kind of slow
combustion or oxidation. The burning of substances like wood
in air is an example of rapid combustion, and the rusting of iron
an example of slow combustion. In every case oxygen unites
chemically with the substances.

Oxidation within the cells results in the performance of work,
and the breaking down of the protoplasm is accompanied by the
production of carbon dioxide and nitrogenous waste substances.
The carbon dioxide is carried to the lungs by the blood and there
excreted. The nitrogenous substances are carried chiefly to
the kidneys. The processes included in the taking up of oxygen
by the protoplasm of the cells and the giving off of carbon dioxide
constitute what is known as internal respiration.

252 PRACTICAL ZOOLOGY

One result of combustion is the production of heat. In man
and other mammals and birds the body is kept at an even tem-
perature by the oxidation of protoplasm regardless of how cold
the surrounding air is. These animals are ‘‘ warm-blooded.”
The frogs and other vertebrates and the invertebrates are all
“cold-blooded,” since the little heat that is produced is lost
rapidly. Their bodies are usually about the same temperature
as their surroundings.

EXxcrETIon. — The waste products resulting from the oxida-
tion of protoplasm are carried by the blood to the excretory or-
gans. The cells of these organs take the waste matter from the
blood and excrete it. Some of it is excreted by the skin, liver,
and intestinal walls, but most of it is taken from the blood in the
two kidneys.

The kidneys contain a great many coiled tubes (uriniferous
tubules) into which the excretions pass. From these tubes they
are carried into one large tube, the wreter, in each kidney, and
from these into a thin-walled sac, the bladder (Fig. 142, B).
From time to time the walls of the bladder contract and force
the excretory matter out of the body through the anal opening.
Excretions are poisonous to the animal and must be removed
from the body. If an animal’s excretory organs do not perform
their functions properly, serious sickness results.

SECRETION. — We have found that excretions are of no use to
the body, but are really injurious and must be cast out to avoid
sickness. Secretions, on the other hand, are of use to the animal ;
in fact, life would be impossible without them, since, for example,

(a3

without saliva, gastric juice, pancreatic juice, and bile, digestion
would be impossible and starvation would result, even where
food is abundant.

Secretions are produced within special secretory cells. When
a number of these cells are grouped together by connective
tissue, the resulting organ is designated a gland. Glands of vari-
ous complexity are present in the body of the frog. In the skin
are simple, saclike mucous glands and poison glands (Fig. 144).

THE FROG, A TYPICAL VERTEBRATE 253

As their names indicate, some of these glands manufacture
mucus, others poison. These substances are secreted into the
central cavity of the gland and then forced out upon the skin
through a thin tube or duct. The glands in the walls of the stom-
ach, which secrete gastric juice, are simple in structure, but
unlike the glands in the skin are sometimes branched. Other
glands are more complex, some resembling a bunch of grapes, like
the salivary glands in man. The liver and pancreas have al-

Fic. 144. — A section through the skin of a frog.

M.G, mucous gland; P.G, poison gland. (From Holmes.)

ready been mentioned as secreting digestive juices; they are
likewise very complex.

A few glands in both the frog and man have no ducts leading
to the alimentary canal or elsewhere, but their secretions pass
directly from their cells into the blood. These are known as
ductless glands and their products as internal secretions. Glands
with ducts, like the liver and pancreas, may also form internal
secretions.

The spleen is a rounded, reddish, ductless gland that lies near
the end of the intestine in the frog. The function of its internal
secretion is not fully known, Other ductless glands are the

254 PRACTICAL ZOOLOGY ,

thyroid and thymus situated in the neck region, and the adrenal
bodies extending along the ventral surface of the kidneys. The
removal of any of these glands, as a rule, is followed by irregu-
larities in the work done by the various organs of the body and
sometimes ends fatally. On the whole, internal secretions are
extremely important for the proper functioning of the various
parts of the body. They seem to act as regulative agents, and
thus secure the codrdination of the different functions. All
glands are not for secretive purposes only, but, like the kidney,
may excrete waste products.

The Skeleton and its Functions. — The skeleton of an animal
supports the softer parts, furnishes points of attachment for
muscles, and protects various organs. Most of the invertebrates
possess exoskeletons such as that of the insect or crayfish. The
vertebrates, on the other hand, are provided with an internal
framework or endoskeleton. This consists of bone and cartilage.
That bone contains cartilage can easily be determined if a piece
is placed in hydrochloric acid. The acid dissolves out the
mineral constituents which give the bone rigidity, leaving the
cartilage, which furnishes pliancy and elasticity.

The skull and vertebral column are often spoken of as the
axial skeleton, and the bones which support the appendages
(arms and legs) as the appendicular skeleton. The accompany-
ing figure (Fig. 145) shows the bones in the skeleton of a frog.

The bones of the skull form a brain case or cranium which
protects the brain, and auditory and olfactory capsules which
protect the sense organs of hearing and smell respectively.
Besides these, the bones of the face (jaw bones, etc.) and of the
throat (hyoids) are included in the skull.

The backbone or vertebral column serves as a central axis. It
consists of a series of bones called vertebre which are held
together by ligaments, but move upon one another so that the
body can be bent. Each vertebra bears a dorsal arch which
surrounds and protects the spinal cord.

The bones which unite the fore limbs to the body constitute

THE FROG, A TYPICAL VERTEBRATE 255

the pectoral girdle. The principal ones are the breastbone or
sternum, the shoulder blades or scapule, and the collar bones or
clavicles.

The bones of the fore limbs are very similar to those of man
and other vertebrates. They are the arm bone or humerus,

the forearm or radio-ulna, the wrist containing six small bones,
and the hand with a row of bones in each of the five digits.

The hind limbs are attached to the vertebral column by the
pelvic girdle consisting of three bones on each side closely fused

256 PRACTICAL ZOOLOGY

together. Each leg contains a thigh bone or femur, a leg bone or
libiofibula, four small ankle bones, five rows of bones in the
digits, and an extra digit bone, the prehallux.

Various kinds of joints are represented in skeleton of the ver-
tebrates. Some of these are tmmovable, such as those of the cra-
nium; others are movable. The fore limbs and hind limbs form
ball-and-socket joints with the pectoral and pelvic girdles; the
knee and elbow joints work like a hinge; the bones of the wrists
and ankles form gliding joints; and the bones of the forearm
(radius) in some vertebrates form a sort of pivot at the elbows.

Muscular Activity.— As already pointed out the muscles
consist of specialized contractile cells and are the agents of
active movement. The ‘ flesh” of vertebrates is largely mus-
cle. As a rule these muscles are attached by one or both ends
to bones either directly or by means of bands of connective
tissue, the tendons. Movements depend upon the attachment
of the muscles and the kinds of joints between the bones.

Most of the large muscles of the frog are used in leaping and
are consequently in the hind limbs (Fig. 146).

A few of these are as follows: (1) The sartorius bends the
hind leg, drawing it forward and ventrally; (2) the gastrocne-
mus bends the hind leg and extends the foot; (3) the adductor
magnus bends the thigh ventrally ; (4) the rectus internus major
bends the hind leg; and (5) the peroneus extends the hind leg
and foot. The pectoralis major moves the fore limbs.

These are all voluntary muscles. Most of the muscles of the
interior organs are involuntary; those in the wall of the bladder
are excellent examples of this type and can be examined easily.

Nervous Activity.— The nervous system of vertebrates is
more complex than that of any other animals. In fact, man
owes his dominance over other animals to the great develop-
ment of his brain. The central nervous system consists of the
brain and spinal cord; the peripheral nervous system consists
of the cerebral and spinal nerves; and a sympathetic system is
also present.

vastint

sar.

Sf. add mag EN
ig add mag a <

Y
Pl t rs sem ler
wectint may

’ str

TLFI

AG

eib.ant 1.266 post

Wa 4 i eeb.ank
i}

va

‘ tthant

ay
NA N
Fic. 146. — Muscles of the frog, ventral view. »)

add.brev, adductor brevis; add.long, adductor longus; add.mag, adductor
magnus; del, deltoid; FE, femur; gstr, gastrocnemius; hy.gl, hyoglossus;
lalb, linea alba; obl.int, obliquus internus; obl.ext, obliquus externus;
pet, pectoralis; per, peronzus; rct.abd, rectus abdominis; rect.int.maj, rectus
internus major; sar, sartorius; sem.ten, semi-tendinosus; tib.ant, tibialis
anticus; tib.post, tibialis posticus. (From Parker and Haswell.) (257)

PRACTICAL ZOOLOGY

sg

eure nara, |e

sc

Fic. 147. — Nervous system and sense organs in the head of the frog.
1, cerebrum; 2, mid-brain; 3, optic lobes; 4, cerebellum; 5, medulla.
e, eye; fv, first vertebra; gpn, glosso-pharyngeal nerve; hn, first spinal
nerve; ie, internal ear; no, nasal opening; on, olfactory nerve; os, olfactory
sacs; p, pneumogastric nerve; sc, spinal cord; sv, second vertebra; t, tympa-
num; tn, trigeminal nerve. (After Jammes.)

THE FROG, A TYPICAL VERTEBRATE 259

The brain is made up of three primary vesicles, a fore-brain,
mid-brain, and hind-brain. The fore-brain gives rise to a pair
of cerebral hemispheres (Fig. 147, r), the mid-brain to a pair of
optic lobes (3), and the hind-brain to the cerebellum (4) and
medulla oblongata (5). It is not certain what the functions of
the cerebral hemispheres are in the frog; they are the seat of
intelligence and voluntary control in higher animals. The
brain as a whole controls the actions produced by the nerve
centers of the spinal cord. ‘The higher centers of the brain
are comparable to the captain of a steamer who issues orders to
the man running the engine when to start and when to stop,
and who has his hand on the wheel so as to guide the course of
the vessel.”

The ten pairs of nerves that arise from the brain of the frog
are known as cranial nerves. Some of these are sensory, others
motor in function. They are distributed to the nose (Fig. 147,
o.m), eye, inner ear, skin and muscles of the face, muscles of the
jaws, tongue, and pharynx, and to the throat, lungs, heart,
stomach, and intestine. Many of the vertebrates possess two
more pairs of cranial nerves than the frog.

The spinal cord is a thick tube directly connected with the
brain (Fig. 147, s.c); it passes through the neural arches of the
vertebral column. It is composed of a central mass of gray
matter (Fig. 148, g.m), consisting mainly of nerve cells, and an
outer mass of white matter (w.m) made up chiefly of nerve fibers.

The relation of the spinal nerves to the spinal cord and the
paths taken by nervéus impulses are indicated in Figure 148.
There are ten pairs of spinal nerves in the frog. Each arises by
a dorsal root (Fig. 148, d.r) and a ventral root (v.r) which spring
from the horns of the gray matter of the cord. The two roots
unite to form a trunk, which passes out between the arches of
adjacent vertebre.

The functions of nervous tissue are perception, conduction,
and stimulation. These are usually performed by nerve cells,
called neurons, The reflex is considered the physiological unit

260 PRACTICAL ZOOLOGY

of nervous activity. The apparatus required for a simple reflex
in the body of a frog is shown in Figure 148. A sensory cell
lying at the surface of the body (s) sends a fiber (s.f) into the
spinal cord, where it branches out; these branches are in physio-
logical continuity with branches from a motor cell (v.c) lying
in the ganglion of the spinal cord. The motor cell (v.c) sends
fibers (#.f) into a reacting organ, such as a muscle (Af). These

Fic. 148. — Diagram of the spinal cord showing the paths taken by nervous
impulses. The direction of the impulses is indicated by arrows.

c.c, central canal; col, collateral fibers; c.cort, cell in the cerebral cortex;
c.g, smaller cerebral cell; d.c, cells in dorsal horn of gray matter; d.r, dorsal
root; g, ganglion of dorsal root; g.c, ganglion cell in dorsal ganglion; g.m,
gray matter; M, muscle; m.c, cell in medulla oblongata; m.f, motor fiber;
S, skin; s.f, sensory fiber; sp.c, spinal cord; v.c, cells in ventral horn of gray
matter; v.r, ventral root; w.m, white matter. (After Parker.)

fibers extending to the reacting organ are called motor fibers
(mf); those leading to the spinal cord are termed sensory fibers
(sf). The sensory cell or receptor receives the stimulus and
produces the nerve impulse; the motor cell, the adjustor, receives,
directs, and modifies the impulse; and the muscle or other organ
stimulated to activity is the effector. Within the spinal cord are
association cells (c.d) whose fibers serve to connect structures
within one ganglion or two succeeding ganglia.

The SyMPATHETIC SYSTEM consists of two principal trunks,
which lic one on either side of the vertebral column. The nerves

THE FROG, A TYPICAL VERTEBRATE 261

of the sympathetic system are distributed to the internal organs
which are thus intimately connected.

Sense Organs. — The principal sense organs of the frog are
the eyes, ears, and olfactory organs. Certain structures on the
surface of the tongue, and on the floor and roof of the mouth,
probably function as organs of taste, and the many sensory
nerve endings in the skin receive contact, chemical, temperature,
and light stimuli.

The nasal cavities (Fig. 147, 0.5) are supplied by the olfactory
nerves (0.z) which extend from the olfactory lobe of the brain.
The importance of the sense of smell in the life of the frog is not
known.

There is no external ear in the frog. The inner ear (Fig. 147,
i.e) lies within the auditory capsule, and is supplied by branches
of the auditory nerve. The middle ear is a cavity which com-
municates with the mouth cavity through the Eustachian tube,
and is closed externally by the tympanic membrane (f).

The vibrations of the tympanic membrane produced by sound
waves are transmitted to the inner ear through a rod, the col-
umella. The sensory end organs of the auditory nerve are stim-
ulated by the vibrations, and the impulses carried to the brain
give rise to the sensation of sound. The inner ears serve also
as organs of equilibration. Frogs from which they are removed
cannot maintain an upright position.

The eyes of the frog resemble those of man in general structure
and function (Fig. 147, e), but differ in certain details. The
eyeballs lie in cavities (orbits, Fig. 145) in the sides of the head.
They may be rotated by six muscles (Fig. 147) and also pulled
into the orbit. The upper eyelid does not move independently.
The lower eyelid consists of the lower eyelid proper fused with the
third eyelid or nictitating membrane. The /ezs is large and al-
most spherical. It cannot be changed in form nor in position,
and is therefore fitted for viewing distinctly objects at a certain
definite distance. Movements are noted much oftener than
form. The amount of light that enters the eye can be regulated

262 PRACTICAL ZOOLOGY

by the contraction of the pupil. The retina of the eye is stimu-
lated by the rays of light which pass through the pupil, and the
impulses which are carried through the optic nerve to the brain
give rise to sensations of sight.

Fic. 149. — Urinogenital organs of the frog.

A, male. 1, fat body; 2, mesentery; 3, efferent ducts of testis; 4, ducts of
seminal vesicle; 5, seminal vesicle; 6, archinephric duct; 7, cloaca; 8, orifice
of ureter; 9, proctodeum; 10, allantoic bladder; 11, rectum; 12, kidney;
13, testis; 14, adrenal body.

B, female. 1, esophagus; 2, mouth of oviduct; 3, left lung; 4, fat body;
5, left ovary; 6, archinephric duct; 7, oviduct; 8, allantoic bladder; 9, cloaca;
10, aperture of oviduct; 11, aperture of archinephric duct; 12, proctodeum;
13, mesentery; 14, kidney. (After Howes.)

Reproduction. — With one or two possible exceptions all ver-
tebrates are bisexual. Individuals differ regarding their sex,
being either males or females, instead of being all of one sort like
the earthworm which is hermaphroditic and contains reproductive
organs of both sexes. The male frogs can be distinguished from
the females externally by the greater thickening of the inner

THE FROG, A TYPICAL VERTEBRATE 263

digit of their fore legs. The sex organs within the bodies of the
two sexes are very different; they are essentially like those in all
other vertebrates including man.
The germ cells of the male, the spermatozoa, arise in two oval
organs, the testes (Fig. 149, A, 13). When mature, they pass

AT

Fic. 150. — Diagrams representing the essential phenomena of mitosis.

A, a cell with resting nucleus; B, the centrosomes are separating; the
chromatin forms a convoluted thread or spireme; C, the spireme is broken
up into a number of V-shaped chromosomes; D, the chromosomes are ar-
ranged at the equator of the spindle; E, division of the chromosomes; F, di-
vergence of the chromosomes; G, chromosomes collecting at the poles of the
spindle; commencement of division of the cell body; H, I, complete division
of the cell, and reconstitution of the nuclei. (From Bourne.)

through tubules (3) into the kidney (12) and from there through
the kidney ducts, the ureters, to the seminal vesicle (5), where
they are stored until the eggs of the female are ready to be fer-
tilized. Then they pass out through the anal opening.

264 PRACTICAL ZOOLOGY

The eggs arise in the two ovaries of the female (Fig. 149, B, 5),
make their way into a pair of tubes, the oviducts (7), and from
there into the distensible uterus. Here they remain until they
are ready to be laid, when they pass out through the anal
opening.

Ecc Laytnc. — The eggs of the frog are laid in water in the
spring. As soon as they emerge from the female they are fer-
tilized by spermatozoa poured over them by the male. Then

6 7 8
& &
Fic. 151. — Stages in the early development of the frog’s egg. (From Ecker.)

the jelly which surrounds them swells in the water and effec-
tively protects them from injury.

EmpryoLtocy.— The development of the egg which takes
place within this coat of jelly is known as embryology and the
partially developed egg is an embryo. One of the most remark-
able of all natural phenomena is the development of a complex
adult animal from an apparently simple egg. To understand
how this takes place we must study the changes that go on
within the egg.

When laid, the egg is a single cell. The spermatozoon is also
a single cell. These two cells unite in fertilization and become
fused into one. The nucleus of the egg and the nucleus of the
spermatozoon approach each other and also fuse into a single
nucleus.

The single cell thus formed, the fertilized egg, now proceeds to
divide into two cells. Inside of the egg the single nucleus di-
vides, by a process called mitosis, into two. During mitosis (Fig.

THE FROG, A TYPICAL VERTEBRATE 265

150) the nuclear wall breaks down, a spindle-shaped structure of
threads with a starlike aster at each end is formed, and the prin-
cipal nuclear substance, called chromatin, forms a certain num-
ber of rodlike bodies, the chromosomes (Be 150, A-D). The
chromosomes split and one half of each is drawn to either end .

Sos enero
ome memane EO

Fic. 152. — Development of the embryo of the frog.

A. Section of blastula. bl.ccel, blastoccel; mi, micromeres; mg, macro-

meres.
B. Formation of medullary groove, md.gr, and medullary fold, mdf; yk.pl,

yolk-plug.
C. Section of egg in stage B to show germ-layers. bl.cel, blastoccel; blip,
blastopore; ect, ectoderm; end, entoderm; ent, enteron; mes, mesoderm;

neh, notochord; yk.pl, yolk-plug.
D. Older embryo. br.cl, branchial arches; stdm, stomodxum; tt, tail.

E. Newly hatched tadpole. br.1, br.2, gills; e, eye; pedm, proctodeum;
sk, sucker; stdm, stomodeum; t, tail. (From Parker and Haswell.)

of the spindle (E, F, G). Each group of chromosomes then be-
comes the center of anew nucleus (H, I). In this way the single
nucleus forms two.

Externally a constriction appears around the diameter of the
egg and the egg is pinched into two equal parts which remain

266 PRACTICAL ZOOLOGY

fastened together. Each of these two cells is provided with one
of the two nuclei formed by the division of the single original
nucleus. This first cell division is followed by the division of
each of the two cells, as shown in the figure (Fig. 151). The

Fic. 153. — Stages in the growth and metamorphosis of the frog tadpole.
(From Mivart.)
cells divide again and again until there are hundreds of cells in
the egg.

These cells become arranged in layers, an outer layer, the
ectoderm (Fig. 152, C, ect), an inner layer, the entoderm (ent), and
a middle layer, the mesoderm (mes). The cells in each layer
differ from those in the others both in their appearance and in

THE FROG, A TYPICAL VERTEBRATE 267

their history, and since the layers are the germs which give rise
to the organs of the body, they are called germ layers.

This embryo moves about within the egg by means of cilia,
but these soon disappear after hatching. The tadpole, after
breaking out of the egg, lives for a few days on the yolk in its
alimentary canal, and then feeds on alge and other vegetable
matter. The external gills grow out into long, branching tufts
(Fig. 153, 2a). Four pairs of internal gills are formed later, and
when the external gills disappear, these function in their stead,
the water entering the mouth, passing through the gill slits, and
out of an opening on the left side of the body, called the spiracle.

The hind limbs appear first (Fig. 153, 5). Later the fore limbs
break out (6). The tail decreases in size as the end of the larval
period approaches (7) and is gradually resorbed. The gills are
likewise resorbed, and the lungs develop to take their place as
respiratory organs. Finally the form resembling that of the
adult frog is acquired (8).

REFERENCES

The Biology of the Frog, by S. J. Holmes. — The Macmillan Co., N. Y. City.
The Frog Book, by M. C. Dickerson. — Doubleday, Page and Co., N. Y.
City.

CHAPTER XXVIII
THE LAMPREY EELS AND OTHER CYCLOSTOMES

Tue phylum Pisces which contains the fishes may be divided
into four subclasses as follows : —

Subclass 1. CycLtostomata. — Lamprey Eels and Hagfishes.

Subclass 2. ELasmoprancuit. — Sharks and Rays.

Subclass 3. TELEOSToMI. — True Fishes.

Subclass 4. Dipno1— Lungfishes.

The simplest group of fishlike animals are the lamprey eels
and hagfishes. These animals are very seldom seen, since they
are aquatic and most of them live in the sea. The species most
easily obtained for study in the laboratory is the sea lamprey
(Fig. 138, A). This fishlike creature inhabits the waters along
the Atlantic coast of North America, the coasts of Europe, and
the west coast of Africa. It swims about near the bottom by
undulations of its body, or when in a strong current, progesses
by darting. suddenly forward and attaching itself to a rock by
means of its suctorial mouth. In the spring it ascends the rivers
to spawn.

Form of Body. — The body of the lamprey reaches a length of
three feet. The skin is not protected by an exoskeleton such as
the scales of the true fishes, but is covered with slimy secretions
from the numerous glands embedded in it. As an aid in swim-
ming the posterior part of the body is provided with a tail fin
and two dorsal fins.

Mouth and Food. — One of the most striking features of the
lamprey is its circular, suckerlike mouth, devoid of jaws (Fig.
154). At the bottom of this sucker is a pistonlike tongue which

when drawn in creates a partial vacuum, enabling the animal to
268

THE LAMPREY EELS AND OTHER CYCLOSTOMES 269

attach itself to solid objects. On and around the tongue are
horny teeth used for rasping the food. Lampreys are parasites,
living on the blood of other animals, principally fish. They
make a hole in the victim’s body and suck out the blood.

Respiration. — Lampreys breathe
in the water by means of gills.
There are seven pairs of circular
respiratory openings just back of
the eyes (Fig. 138, A); each open-
ing is the entrance to a sac in which
the gills are situated. Water enters
and is forced out through the same
openings, and, as in the crayfish,
the blood in the gill filaments ex-
changes its load of carbon dioxide
for a fresh supply of oxygen that
is mixed with the water.

Sensations. — Lampreys are able :
to see, hear, smell, taste, and feel, F!6- 154. — The mouth of the

i i lamprey eel. (From Forbes.)
but none of their senses is very
highly developed. The eyes are poor; the ears have only two
semicircular canals instead of the usual three; there is a single
nostril situated on top of the head between the eyes; and a few
taste cells inside the pharynx.

Internal Organs. — The internal organs are likewise primi-
tive. The skeleton is entirely of cartilage; there is no distinct
stomach; the heart has only one auricle and one ventricle; and
the brain is very simple, resembling that of the embryo of higher
vertebrates.

Development. — The development of the lamprey is very
interesting. The eggs produce larve which differ in many
respects from the adult, and were at one time considered a dis-
tinct species of animal. The larvee lie buried in mud and sand,
and food particles are drawn into the mouth by means of a cur-
rent of water produced by cilia. In the winter of the third or

270 PRACTICAL ZOOLOGY

fourth year the larval lamprey undergoes a metamorphosis, dur-
ing which the structure and habits of the adult are acquired.

Other Cyclostomes. — The other lampreys and the hagfishes
resemble the sea lamprey in most respects. They live in the
mud of the sea bottom and are of considerable economic impor-
tance because of their parasitic habits. All kinds of fish are at-
tacked by them, but principally shad, sturgeon, cod, mackerel,
and flounders. <A hole is rasped through the body wall just
beneath the pectoral fins and the blood sucked out. Lampreys
are used as food by man, but they are not numerous enough to
be of any great value.

The Brook Lamprey.— In many of the North American
brooks lives a very small brook lamprey, but since the adults
probably eat no food and the young live on minute animals and
plants, they are of no economic importance. However, if they
can be caught, they can be kept alive in the laboratory for a long
time and thus furnish excellent material for study.

REFERENCES

Fishes, by D. S. Jordan. — Henry Holt and Co., N. Y. City.
Bulletins of the U. S. Fish Commission.

CHAPTER XXIX
THE STRUCTURE AND ACTIVITIES OF FISHES

FIsHES are rather easy to study since specimens can be ob-
tained in fish markets for examination in the laboratory. The
common perch is perhaps the best species because of its conven-

a2
KiB,

Yom

Fic. 155. — Diagram of a fish (perch) with parts named.

a, anal fin; br, branchiostegal rays; ch, cheek; cp, caudal peduncle; d1,
spinous dorsal fin; d2, soft dorsal fin; dr, rays of second dorsal fin; d2s,
spines of second dorsal fin; dcp, depth of caudal peduncle; dp, depth (of
body); e, eye; id, insertion of dorsal fin; io, interopercle; md, lower jaw, or
mandible; mx, maxillary; n, nose, or snout; np, nape; 0, opercle; p, pectoral
fin; pmx, premaxillary; po, preopercle; so, subopercle; v, ventral fin.
(After Forbes.)

ient size and general distribution. Every one who has ever had

the opportunity has “‘ gone fishing,” and knows something about

the differences between different species. A great many peculiar

fishes, however, live in the sea or are confined to restricted parts
271

Fic. 156. — Front
view of a fish (Spanish
mackerel). (From

PRACTICAL ZOOLOGY

of the world, so that they are very seldom
seen. The general needs of fishes and methods
of supplying them may be discussed to ad-
vantage with the perch as a basis (Fig. 155).

Habitat. — Fishes are all aquatic. Some of
them are restricted to the salt water of the
sea, others to fresh water, and a very few
are, like the salmon, able to swim from the
sea into fresh water or from fresh water into
the sea without suffering any injury.

Form of Body. — Since the water offers
more resistance than air to movement through
it, and since fish as a rule must move rapidly

Dean.) to catch their food and

escape their enemies, it is not strange that
the fish’s body is long and slender, pointed
at the ends, and compressed from side to
side. This form offers very little resistance
to the water (Fig. 156). Variations in form
depend upon the habits of the fish. For
example, the flatfishes, or flounders (Fig.
171), have thin bodies which adapt them for
life on the sea bottom; the eels (Fig. 165, D)
have a long, cylindrical body which enables
them to enter holes and crevices, and the
porcupine fish possesses a covering of heavy
spines which stick straight out when it in-
flates itself and protect it from its enemies.

Locomotion. — The principal locomotor
organ is the tail, which is lashed from one
side to the other, forcing the fish ahead,
much as a boat is propelled by sculling or a
steamer by its screw (Fig. 157). The tail is
made more effective by the presence of the
caudal fin, which offers more resistance to

Vic. 1§7.—Diagram
showing how the tail
of a fish is used in
swimming. (After
Pettigrew.)

THE STRUCTURE AND ACTIVITIES OF FISHES 273

the water. The other fins aid the fish in maintaining an upright
position and help it to steer the body up or down, straight
ahead, or from one side to the other.

The shapes and positions of the fins differ in different species;
for example, the caudal fin of the perch (Fig. 155) is bilaterally
symmetrical and is adapted to swimming straight ahead, whereas
that of the sturgeon (Fig. 163, A) is longer above than below
and tends to force the body downward to the bottom, where this
species obtains its food.

Fishes may often be seen suspended in the water and almost
motionless. This they are able to do because of the presence

Cc

Fic. 158. — Fish scales.

A, placoid; B, ganoid; C, ctenoid; D, cycloid. (From Parker and
Haswell.)

of an air bladder within the body which decreases their weight
until they are exactly as heavy as the amount of water they dis-
place.

Protection. — The enemies of the adult fish are principally
other fish, birds such as kingfishers, herons, gulls, and terns, and
flesh-eating mammals like the otter. From most of these the
fish escape by swimming away rapidly, but from ordinary physi-
cal injury they are protected by an exoskeleton of scales or
bony plates.

ScALES. — The scales are of several kinds; those most com-
monly seen are thin, oval structures (Fig. 158, C and D) which

T

274 PRACTICAL ZOOLOGY

are arranged in oblique rows on the fish’s body and overlap each
other like the shingles on the roof of a house (Fig. 155). In such
fish as the gar pike (Fig. 163, C) the scales are very thick and
strong and diamond-shaped (Fig. 158, B); very few animals are
able to penetrate such anarmor. Sharks and rays (Figs. 161 and
162) possess a covering of toothlike scales (Fig. 158, A), which
actually develop into teeth in the mouth region. The spines
of some fishes develop from scales, and bony plates such as those
of the sturgeon (Fig. 163,
A) have a similar origin.

Cotor.— The colors of
the fish are more impor-
tant as a protection than
the scales since they tend
to conceal the animal
amid its surroundings.
The red, orange, yellow,
and black pigments pres-
ent in the skin (Fig. 159)

Fic. 159. — Pigment bodies in the skin of may give the fish these

a fish. (After Cunningham.) eclabs -or-elee blend 46

form other colors. The structure of the scales may also produce
certain colors due to reflection and iridescence.

Usually the colors are arranged in a definite pattern consisting
of transverse or longitudinal stripes and spots of various sizes.
Coral-reef fishes have long been famous for their brilliant colors,
and many fresh-water fishes of the temperate zone exhibit
bright hues distributed so as to form striking and intricate
patterns (e.g. the rainbow darter). A few fish are able to change
their colors so as to match the bottom on which they lie; this is
true of the flounder (Fig. 171).

Sensations. — Fishes possess all of the five senses, but the
sense organs differ somewhat from those of land animals.

The eyes (Fig. 155, e) are usually without lids, since the water
keeps the eyeball moist and free from foreign matter. The pupil

THE STRUCTURE AND ACTIVITIES OF FISHES 275

is large so as to allow more light to enter —a necessity under
water where the light is not strong. Fishes probably cannot see
in the air.

There is no outer or middle ear, but only the membranous
labyrinth is present, since the water transmits the sound waves
directly to the inner ear.

Unlike the lamprey eel, there are two nostrils in the fishes,
each of which is a sac connected with the water through a pair
of openings in front of each eye, and containing many sense cells
of smell in their walls.

The sense of taste is not well developed. Fishes swallow their
food whole or in large pieces, and a few sense cells that are present
in the walls of the mouth are sufficient.

The entire skin, but especially that of the lips, is provided with
tactile sense cells.

Respiration. — Respiration in fishes is typically aquatic, taking
place in the gills. Ina few fish the air bladder may also serve as
a respiratory organ. The sharks (Fig. 161) possess rows of gill
slits on either side of the head, but in most fishes the gills are pro-
tected from injury by a gill cover, the operculum (Fig. 155, 0).

The four pairs of gills usually present are supported by four
pairs of gill arches. Each gill bears a dcuble row of branchial
filaments which are abundantly supplied with capillaries. The
afferent branchial artery brings the blood from the heart to the
gill filaments; here an exchange of gases takes place. The
carbonic acid gas with which the blood is loaded passes out of
the gill, and a supply of oxygen is taken in from the continuous
stream of water which enters the pharynx through the mouth
and bathes the gills on its way out through the gill slits. Be-
cause oxygen is taken up by the capillaries of the gill filaments,
a constant supply of fresh water is necessary for the life of the
fish. If the fish is deprived of water entirely, respiration is pre-
vented, and the fish dies of suffocation.

Reproduction. — As in the frog, the eggs of most fish (Fig.
160, A) are deposited in the water by the female fish and then

276 PRACTICAL ZOOLOGY

fertilized by the spermatozoa (milt) of the male which are poured
over them. At this time the fish are said to be spawning. Very
few of the eggs succeed in producing adult fish, since they are
eaten by numerous animals and destroyed by fungous plants
and by being smothered by sand and mud on the bottom. The
young fish lives for a time on the yolk stored up in the egg (Fig.
160, B); later it begins to feed on small crustaceans and insects

Fic. 160. — Photographs of three stages in the growth of the trout. (From
Bul. U. S. Fish Com.)

(Fig. 160, C), and finally on larger crustaceans, insects, mollusks,
and other fish.

Many fish migrate long distances to lay their eggs. For ex-
ample the chinook salmon (Fig. 172, D) lives in the sea along the
Pacific coast from Monterey Bay, California, and China, north
to Bering Straits. It enters the fresh-water streams to spawn,
especially the Sacramento, Columbia, and Yukon rivers. The
ascent takes place in the spring and summer, beginning in
February or March in the Columbia River. The salmon do not
feed during this migration, but swim at first slowly and then
more rapidly until they reach the small, clear mountain streams
often more than a thousand miles from the sea. Spawning

THE STRUCTURE AND ACTIVITIES OF FISHES 277

occurs from July to December, according to the temperature of
the water, which apparently must be below 54° Fahrenheit.
The eggs are deposited upon the gravelly bottoms of the streams,
after which both males and females die; consequently an indi-
vidual spawns only once in its lifetime. The eggs hatch in about
seven weeks, and the young remain on the spawning ground for
six weeks. They then float slowly downstream and may be four
or five inches long when they reach the sea.

REFERENCES

Fishes, by D. S. Jordan. — Henry Holt and Co., N. Y. City.

The Fishes of North and Middle America, by Jordan and Evermann. —
Bulletin No. 47, U. S. National Museum, 4 volumes.

Bulletins published by the U.S. Fish Commission.

CHAPTER XXX

SOME COMMON FISHES OF NORTH AMERICA

Subclass 2. Elasmobranchii

Tue sharks (Fig. 161) and rays (Fig. 162) are characterized
by a cartilaginous skeleton, toothlike scales (Fig. 158, A), a
slitlike mouth on the ventral side of the head, and gill openings
not covered by an operculum. The sharks resemble the true
fish in shape, whereas the rays are very much flattened. Sharks

Fic. 161. — A, dogfish shark; B, sawfish. (After Goode.)

are usually less than ten feet long and, contrary to general be-
lief, feed upon crustaceans, squids, and fish rather than upon
human beings. Occasionally the great white shark which lives
in the tropics and reaches a length of thirty feet may become a
man eater.

The rays or skates have their bodies greatly flattened and are
thus adapted to a life on the bottom. The sting ray (Fig. 162)

278

SOME COMMON FISHES OF NORTH AMERICA ,279

occurs off the coast of Florida. Its name is derived from the
sting inflicted by a spine at the base of its whiplike tail. The
sawfish (Fig. 161, B) is a’ray with its head extending forward
as a long, sawlike projection.
The saw of a fifteen-foot fish
is about five feet long; it is
used to defend the fish or to
capture its food. The for-
pedo ray possesses electric
organs on either side of its
head which can give a shock
strong enough to stop rather
large animals.

Subclass 3. Teleostomi

The true fishes or TELEOS-
Tomi have a skeleton con-
sisting entirely or partly of
bone and an operculum
covering the gills. About
twelve thousand species are
known from the entire world
and over three thousand
species occur in North
America.

The sturgeon (Fig. 163, A)
is a rather primitive fish that
resembles a shark in the shape of the body. Its tail fin is larger
above and its mouth is on the ventral surface. It feeds on the
bottom, using its snout for stirring up the mud and the sensitive
filaments (barbels) near the mouth for finding food. Sturgeons
are economically important; their flesh is excellent for food;
their eggs are made into a much-prized table delicacy called
caviar; and their air bladders are used as isinglass.

A near relative of the sturgeon is the paddlefish (Fig. 163, B)

Fic. 162. — Sting ray. (From Jordan
and Evermann.)

I'ic. 163. —A, sturgeon; B, paddlefish; C, gar pike; D, sucker;
E, carp. (Prom Goode.) (280)

SOME COMMON FISHES OF NORTH AMERICA 281

which lives in the rivers of the Mississippi Valley. This peculiar
fish reaches a length of six feet and a weight of one hundred and
sixty pounds, but the specimens usually taken weigh no more
than fifty pounds. Its large, paddle-shaped snout is regarded
as a sense organ, and its use is still unknown. The food of the
paddlefish consists largely of minute plants and animals, of
which enormous numbers are devoured. The paddlefish is
good to eat, but its roe (eggs), from which caviar is made, is
more valuable than its flesh.

The gar pike (Fig. 163, C) is another primitive fish that looks
very much like the fossil remains of ancient fish sometimes found

Fic. 164. — Photograph of a catfish. (From Shufeldt.)

in the earth’s crust. It has a remarkably strong armor of
scales and a long snout fitted with formidable teeth. The fish-
ing industry is injured by gar pikes which kill great numbers of
valuable fish, especially the young.

The suckers (Fig. 163, D) are very abundant in many North
American streams. Their lips are protractile and fleshy, being
used for obtaining worms, insects, etc., from the bottom. Suckers
are not considered very good to eat, but because of their abun-
dance are of considerable economic importance.

The German carp (Fig. 163, E) has become established in many
parts of the country since it was introduced in 1872. It is able
to live in muddy water, breeds rapidly, and will eat almost any-

282 PRACTICAL ZOOLOGY

H)
y
i

chaos csc cermnanticees
2 Benen
my HS
Rantied ae ay ,
Caan

ROEM

— >
%)

Y Mh
inane

Fic. 165. — A, flying fish; B, cave fish; C, remora; D, eel.
(From Jordan and Evermann.)

SOME COMMON FISHES OF NORTH AMERICA 283

thing. Carp are accused of destroying the eggs of other fishes,
of driving other fishes away by stirring up mud, and of eating
aquatic vegetation and thus depriving wild ducks of their food.

Catfishes (Fig. 164) are scaleless fish that, like the sturgeon,
live on the bottom and find their food by means of sensitive fila-
ments (barbels). The bwllhead is a small catfish known to every
fisherman. The Mississippi catfish sometimes reaches a length
of five feet and a weight of over one hundred pounds. It is a
valuable food fish.

A discussion of many of our food and game fishes will be found
in the next chapter.

A few fish are worthy of space here because of their peculiar-
ities. Some of the cave fishes (Fig. 165, B) found in the river
Styx of the Mammoth Cave and in other
subterranean streams are blind.

Certain species of fish living in warm seas
have greatly enlarged pectoral fins (Fig. 165,
A) which enable them to rise out of the
water and “ fly” for as much as an eighth
of a mile.

The true eels (Fig. 165, D) have very long,
cylindrical bodies shaped like that of the
lamprey eel, with which they should not be
confused.

The sea horse (Fig. 166) is a fish only a
few inches long, with a head that reminds A
one of the head of a horse. It can cling to Fic. 166.— The sea
objects with its prehensile tail. The male oe Sapa bie

ranchial aperture;
protects the eggs in a brood pouch. m.p, brood pouch.

The remora (Fig. 165, C) is a fish that ee
clings to the body of a shark with its dorsal
fin which is modified as a sucker; it thus secures transportation
and possibly food when the shark has a meal.

In the deep sea are many fishes with phosphorescent organs
distributed over the body; these may serve to illumine the sur-

284 PRACTICAL ZOOLOGY

roundings or to lure other fish within reach of the sharp teeth.
When these fish are drawn up to the surface, the gas in the air
bladder, being relieved of most of its pressure, expands and often
forces part of the alimentary canal out of the mouth.

Subclass 4. Dipnoi

The third subclass of fishes contains the Drpnor or lung fishes
(Fig. 167). There are only five species of these alive at the
present time. One occurs in Australia, three in Central Africa,

Fic. 167. — Photograph of a living African lungfish. (Photo. provided by
American Museum of Natural History.)

and one in South America. All of them are able to live in
marshes, swamps, and other bodies of stagnant water because
their air bladders function as a lung. They are therefore not
dependent upon fresh water, but can breathe air.

REFERENCES
See end of Chapter XXIX.

CHAPTER XXXI
THE RELATIONS OF FISH TO MAN

THE fishes constitute a group of animals that are practically
always beneficial to man. Fish are caught sometimes for pleas-
ure alone, as an exhilarating form of recreation; and the species
that are fished for in this way are called game fishes. More often
fish are caught as an article of food, and such are called the food
fishes.

Game Fishes. — Every one is familiar with many of the fresh-
water game fishes. Among the common species are the perches,
trout, pike, muskallunge, and basses.

FRESH-WATER GAME FisHEs. — The yellow perch (Fig. 155)
inhabits the fresh-water streams and lakes of the northeastern
United States, and ranges west to the Mississippi Valley. It is
perhaps the best pan fish among American fresh-water fishes,
and in many localities it is taken largely for market. It is not
a good game fish, but for the food market it has one advantage
—it is easy to catch. The perch has been introduced success-
fully into several small lakes in Washington, Oregon, and Cali-
fornia. It can be artificially propagated, but other fish, such as
whitefish, lake trout, and pike perch, are of greater commercial
importance and are, therefore, preferred for propagative pur-
poses to the yellow perch.

The trout family contains a number of our finest game fishes.
The brook or speckled trout prefers clear, cool streams with a
swift current and a gravelly bottom. The mountain or cut-
throat trout is a large species inhabiting the streams and lakes
of the Rocky Mountain region. The rainbow trout (Fig. 170, A)

is also a western species. It is a good game fish and takes the
285

286 PRACTICAL ZOOLOGY

fly readily. In weight it averages about two or three pounds.
The steelhead or salmon trout is found in the streams along the
Pacific coast. Like the salmon it migrates upstream to spawn.
Its average weight is about eight pounds. Thousands of steel-
head trout are taken each year for canning purposes, especially
in the Columbia River. They are also considered excellent
game fish.

The common pike or pickerel (Fig. 168, A) inhabits all suitable
fresh waters of northern North America, Europe, and Asia. It is

Fic. 168. — A, pike; B, tarpon. (From Goode.)

extremely voracious, feeding on other fishes, frogs, aquatic birds,
and many other aquatic animals. The pike is an excellent game
fish, but its flesh is not very good. The muskallunge resembles
the pike in form and habits. It is found in the Great Lakes region
and is a king among fresh-water game fishes, reaching a length
of over seven feet and a weight of almost a hundred pounds.
The bass family comprises about thirty species, most of which
are good game fishes and also excellent for the table. Some of

THE RELATIONS OF FISH TO MAN 287

the most common species are the crappie, the rock bass, the
bluegill, the common sunfish or pumpkin seed (Fig. 169), the
small-mouthed black bass, and the large-mouthed black bass.
The small-mouthed black bass is considered “ inch for inch and
pound for pound, the gamest fish that swims.”’ The male bass
in May or June makes a nest by clearing away a place near shore

Fic. 169. — Photograph of a living sunfish. (After Shufeldt.)

where there are good-sized stones. Eggs are then laid and fer-
tilized, and the male guards them during the hatching period of
five or six days. The male continues to protect the young
until they reach a length of an inch and a quarter. Black bass
are successfully propagated in artificial ponds by the Bureau of
Fisheries.

SALT-WATER GAME FisHES. — Many salt-water fish also are
caught principally for purposes of recreation. Among these are
the tarpon, sea bass, and tuna. There are four or five species
of tarpon inhabiting the tropical seas. The common tarpon

288 PRACTICAL ZOOLOGY

(Fig. 168, B) is a famous game fish on the coast of Florida, and
is called the “ silver king.”

The striped bass is a fine game fish occurring along the coast
of eastern North America. It has also been successfully intro-
duced along the coast of California. The jew/ish or black sea
bass is the giant game fish of the California coast. It can be
taken with a sixteen-ounce rod, and there are many records of
specimens captured by this method weighing over three hundred
pounds.

The tuna is called the tunny or horse mackerel on our eastern
coast, but is the tuna of California. Tunas are eagerly sought
with hook and line, and many that weighed over one hundred
pounds have been landed by this means.

Food Fishes. — It is, of course, a matter of personal opinion as
to which of the food fishes is the best. The value of a species
does not depend upon its edible qualities, however, so much as
upon its abundance. The common herring is the most important
of the food fishes in the Atlantic. Herring swim about the
North Atlantic in immense shoals, often covering half a dozen
square miles and containing as many as three billion individuals.
On the New England coast herring are smoked, salted, pickled,
packed as sardines, or used for bait in codfishing.

Another group of important food fishes that occur in the sea
belong to the mackerel family. Fifteen species of mackerel in-
habit the salt waters of North America. The common mackerel
(Fig. 170, B) occurs in the North Atlantic, swimming about in
enormous schools. It feeds on small aquatic animals, such as
Crustacea, and furnishes food for other fishes. It is also a valu-
able food fish for man. The Spanish mackerel is also a common
food fish of the North Atlantic.

The flounder family contains flatfishes known as flounders
(Fig. 171), halibuts, soles, plaice, and turbots. They are flat-
tened from side to side, and thus adapted for life on the sea
bottom. Frequently they are colored on the upper surface so
as to resemble the sand or other material surrounding them.

THE RELATIONS OF FISH TO MAN 289

The young flatfish resembles an ordinary fish when it hatches,
but soon begins to broaden laterally and swim on its side, while
the eye on the lower side moves around to the upper side. The

Fic. 170. —A, rainbow trout ; B, mackerel; C,cod. (From U.S. Fish Manual.)

common halibut and the winter flounder are important American
food fishes.

Many of our most important food fishes, the pollocks, cod-
fishes, haddocks, and hakes, belong to the codfish family. “ From

U

290 PRACTICAL ZOOLOGY

the earliest settlement of America the cod has been the most
valuable of our Atlantic coast fishes. Indeed, the codfish of
the Banks of Newfoundland was one of the principal induce-
ments which led England to establish colonies in America.”
The total weight of the codfishes landed at Boston and Glouces-
ter in 1908 was 41,615,277 pounds, valued at $1,042,683. The
Bureau of Fisheries distributes millioris. of fry every year.

Fic. 171. — Flounder. (From U. S. Fish Manual.)

Fresh-water Food Fishes. — The food fishes mentioned thus
far are all marine species. There are, however, a great many
fresh-water fishes of commercial importance. Some of these are
mentioned in Chapter XXX; namely, the sturgeons, paddle-
fishes, suckers, carp, and catfishes. Others are the whitefish,
lake trout, pike perch, and salmon.

The common whitefish (Fig. 172) occurs throughout the Great
Lakes region. During the winter it prefers deep water, but
in the spring it migrates to the shallow water to secure insect
larvae which become abundant at that time. It migrates to
shallow water again in the autumn to spawn. The mouth is on
the under side, and the crustaceans, mollusks, and other animals
used as food are picked up from the bottom. The eggs are laid

THE RELATIONS OF FISH TO MAN 291

over honeycomb rock, and since many of them are covered by
sediment or fall prey to mud puppies, yellow perch, crayfishes,
and other enemies, very few develop into adult fish. Because

Fic. 172. — Whitefish. (From U. S. Fish Manual.)

of this fact the government each year gathers, rears, and dis-
tributes millions of whitefish eggs. Whitefishes are captured
in deep water by means of gill nets which hold the fish just be-

Fic. 173. — Lake trout. (From U. S. Fish Manual.)

hind the gill covers. The average weight is about four pounds,
but they may become as heavy as twenty pounds.

The lake trout (Fig. 173) is another important food fish of
the Great Lakes region. It is the largest of our trouts, averag-

292 PRACTICAL ZOOLOGY

ing about eighteen pounds, but occasionally attaining a weight
of over one hundred pounds. Lake trout are captured usually
in gill nets. They are omnivorous, but show special preference
for lake herring. The spawning season ranges from September

Fic. 174. — Pike perch. (From U. S. Fish Manual.)

to November, according to the latitude. Millions of eggs are
cared for and distributed by the government each year.

The wall-eyed pike or pike perch (Fig. 174) is another well-
known and valuable species. It is common in the Great Lakes
region and is extensively propagated by the Bureau of Fisheries.

Tic. 175. — Salmon. (From U.S. Fish Manual.)

The Canning of Salmon. — Quite a number of species of
salmon are used for purposes of canning, especially on the Pacific
coast. ‘“‘ The canning of salmon, that is, the packing of the

THE RELATIONS OF FISH TO MAN 293

flesh in tin cases, hermetically sealed after boiling, was begun on
the Columbia River in 1866. In 1874 canneries were established
on the Sacramento River, in 1876 on Puget Sound and on the
Frazer River, and in 1878 in Alaska. At first only the quinnat
salmon was packed; afterwards the red salmon and the silver
salmon, and finally the humpback, known commercially as
pink salmon.

“The output of the salmon fishery of the Pacific coast
amounts to about fifteen millions per year, that of Alaska con-
stituting seven to nine millions of this amount. Of this amount
the red salmon constitutes somewhat more than half, the quinnat
about four fifths of the rest.

“Tn almost all salmon streams there is evidence of considera-
ble diminution in numbers, although the evidence is sometimes
conflicting. In Alaska this has been due to the vicious custom,
now done away with, of barricading the streams so that the fish
could not reach the spawning grounds, but might all be taken
with the net. In the Columbia River the reduction in numbers
is mainly due to stationary traps and salmon wheels, which leave
the fish relatively little chance to reach the spawning grounds.
In years of high water doubtless many salmon run in the spring
which might otherwise have waited until fall.

“The key to the situation lies in the artificial propagation of
salmon by means of well-ordered hatcheries. By this means the
fisheries of the Sacramento have been fully restored, those of the
Columbia approximately maintained, and a hopeful beginning
has been made in hatching red salmon in Alaska’ (Jordan).

The Value of the Fishing Industry. — The value of the fishing
industry may be judged from statistics obtained at Boston and
Gloucester, where about seven eighths of all the fish captured
offshore along the Atlantic coast are brought by the fishermen.
During the calendar year, 1908, 181,465,000 pounds of fish, worth
to the fishermen $4,629,000, were landed at these two cities.
The most important species were the cod, haddock, hake, pol-
lock, halibut, and mackerel. The salmon fisheries of Alaska are

204 PRACTICAL ZOOLOGY

even more valuable. The total quantity taken in 1908 was
198,952,814 pounds, valued at $10,683,051. Fifty canneries
and forty salting establishments were operated, and 12,183 per-
sons were employed to catch, prepare, and transport the canned,

pickled, fresh, and frozen fish. ©

SOME OF THE FISH AND EGGS DISTRIBUTED BY U. 5.

BUREAU

OF FISHERIES FROM JUNE 30, 1908, TO JUNE 30, I909

SPECIES | Eccs Fry! FINGERLINGS ? TOTAL

1. Flatfish | 786,626,000 786,626,000
2. Pike perch . . «| 457,850,000] 187,050,000 644,900,000
3. Whitefish . : | 142,220,000] 277,445,000 419,065,000
4. White perch . - | 24,500,000 318,760,000 2,650 | 343,262,650
5. Yellow perch . | 10,000,000] 213,610,410 50,873 | 223,061,283
Ox Codhen ay Ge oye | 153,530,000 153,530,000
7. Blueback salmon 100,000} 93,409,490 93,509,490
8. Lake trout 22,806,000] 27,188,177) 1,345,100 | 51,339,277
g. Brook trout 905,000) 5,821,322] 3,723,489 | 10,449,811
1o. Rainbow trout 286,150 292,408] 2,026,403 2,605,021

11. Large-mouth black
bass eee: 32,500) 540,962 573,402

12. Small-mouth — black
bass 262,674 IT1,Q24 3745598

The Artificial Propagation of Fishes. — In many places the

fish have been captured in such great numbers that laws regu-
lating the fishing industry have been passed. The federal and
state governments have also for many years operated fish hatch-
eries, where the eggs of important fishes are kept during their
development. In nature very few eggs are allowed to develop
because of the attacks of fungi and of animals such as other
fishes, crayfishes, and wild fowls. On the other hand, a large
percentage of the eggs collected and cared for in fish hatcheries

‘Fry are fish up to the time the yolk sac is absorbed and feeding begins.
? Fingerlings are fish between the length of one inch and the yearling stage.

THE RELATIONS OF FISH TO MAN 295

develop. They are distributed either as well-developed eggs
or as young fish, and are planted in the waters from which the
adult fishes were taken, and also in waters where the fishes are
not native.

In 1909 the Bureau of Fisheries operated 35 hatcheries and
84 subhatcheries, auxiliaries, and egg-collecting stations; these
were located in 32 states and territories. The regular hatcheries
may be classified as follows with reference to the fishes propa-
gated: marine species, 3; river fishes of the eastern seaboard, 5 ;
fishes of the Pacific coast, 5; fishes of the Great Lakes, 7; fishes
of the interior regions, 15. The total output of fish and eggs in
1909 Was 3,107,131,911. During the year applications were
received for fish for planting in 10,111 different bodies of water.
A summary of distributions is given in the table on page 294.

Besides this, 568,150 eggs were shipped to Argentina, France,
and Germany.

The Artificial Propagation of the Lake Trout. — The methods
employed in artificially propagating fish may be illustrated by an
account of the lake trout. Adult lake trout are captured chiefly
during the spawning season in September, October, and Novem-
ber in gill nets, pound nets, or by hook and line. Government
employees called spawn takers accompany the fishermen on
their trips to collect the eggs of the fish captured or else the
fishermen themselves are forced to collect the eggs for the
government. The ripe females are selected and their eggs
squeezed out by the spawn takers, a process known as stripping.
The eggs are allowed to fall into a milk pan. They are then
fertilized by squeezing some of the milt (spermatozoa) from a ripe
male into the pan and stirring up the eggs with the tail of the
fish. When the pan is half full, the eggs are washed and trans-
ferred to a five-gallon pail. Each pail holds about 75,000 eggs.

The eggs thus obtained may be kept at field statvons for several
days or shipped directly to the hatchery. In either case they are
placed on shallow trays, each holding 10,000 eggs, and eighteen
of these trays are placed in a box with moss packed around them.

206 PRACTICAL ZOOLOGY

When the boxes reach the hatchery, the trays are removed and
the eggs transferred to other trays that fit into the hatching
troughs. Each of these trays holds 6000 eggs, and one hatch-
ing trough when filled contains 5,000,000 eggs. Cold water is
kept continually flowing over the eggs at the rate of seven
gallons per minute. Every three days the trays are carefully
examined and all eggs that are dead or are attacked by fungous
diseases are picked out.

The eggs begin to hatch in from 75 to 90 days according to
the temperature of the water. They are shipped to the waters
in which they are to be planted shortly before they hatch, or
else they are allowed to hatch and the young fry are planted.

The methods of propagation depend upon the habits of the
fish and the weight of the eggs. Fishes that do not care for
their eggs or young, like the lake trout and whitefish, can be
propagated as described above. Other species, like the black
bass, lay a lesser number of eggs, but guard them. Such fish are
kept in ponds and protected during the spawning season.
Eggs like those of the lake trout are heavy and must be
spread out in thin layers on trays, but the comparatively light
eggs of such fish as the whitefish are hatched in glass jars,
each jar containing five quarts or 200,000 eggs. Water
must flow through these trays or jars continually.

Work of the United States Bureau of Fisheries. — The United
States Bureau of Fisheries was organized in 1871 as an independ-
ent institution, but in 1903 it was included in the new Depart-
ment of Commerce and Labor. It consists of three principal
divisions: (1) Fish Culture, (2) Scientific Inquiry, and (3) Sta-
tistics and Methods of the Fisheries.

Some idea of the work done along fish cultural lines may be
gained from the preceding paragraphs on the artificial propaga-
tion of fishes. The efforts of the bureau have not been limited
to fish, however, but the propagation of lobsters, oysters,
sponges, fresh-water mussels, and diamond-back terrapins has
been studied and in most cases successfully accomplished.

THE RELATIONS OF FISH TO MAN 2907

The bureau owns two large seaside laboratories where in-
quiries of a scientific nature are being made every summer.
One of these is at Woods Hole, Mass. (Fig. 176), the other at
Beaufort, North Carolina.

Surveys of offshore fishing grounds, the study of deep-sea
fishes, and general explorations of the sea are constantly being

Fic. 176. — The Laboratory Building of the U. S. Bureau of Fisheries at
Woods Hole, Mass.

made with the aid of two steamers, the Albatross and the Fish
Hawk.

About 70 large volumes have been published by the bureau. :
These volumes contain papers on various subjects which may be
classified as follows : —

t. Annual report of the commissioner.

2. Fish culture:

(a) Methods.
(b) Distribution of fish and eggs.
(c) Fish diseases and parasites.

208 PRACTICAL ZOOLOGY

3. Aquatic biology:
(a) Economic investigations.
(6) Explorations and surveys, the methods, apparatus, etc.
(c) Descriptions of species and faunal lists.
(d) Morphological, physiological, and pathological studies.
4. Commercial fisheries and related industries.
Papers on any of these subjects are mailed free of charge to
any one asking for them so long as there are any copies on hand.

REFERENCES
See end of Chapter XXIX.

CHAPTER XXXII

THE AMPHIBIA

Tue toads, frogs, salamanders, and a few other animals belong
to the class Ampiibia. The toads and frogs are easily recog-
nized, but the salamanders are often confused with the lizards
among the reptiles. Lizards, however, are covered with scales,
and salamanders are naked. The eggs of amphibians are usually

e Sets eS Ee « z z
Fic. 177. — Photograph of living mud puppy. (From Report N. Y. Zool.
Soc.)

laid in the water, like those of the frog, and the young spend their
larval life in the water breathing by means of gills. Some am-
phibians remain in the water throughout life, but most of them
forsake the water as soon as they lose their gills and acquire
lungs, and they may be found in damp places.

Tailed Amphibians. — The salamanders, mud puppies, and
newts are tailed amphibians. The largest of these is the giant
salamander of Japan, which reaches a length of over five feet.

209

300 PRACTICAL ZOOLOGY

The hellbender and mud puppy (Fig. 177) occur in streams in
the eastern United States.

The crimson-s potted newt (Fig. 178) is common in the ponds of
the northern and eastern portions of the United States. It is
about three and one half inches long and has a row of crimson
spots on either side. Its food consists principally of insect
larvee, worms, and small mollusks. The eggs are laid in April,

Fic. 178. — Crimson-spotted newt. (Photograph of living animal furnished
by American Museum of Natural History.)

May, or June, and a sort of “ nest” of aquatic vegetation is
constructed for each egg. The young live for a time on land
under stones and logs, but return to the water after several
years, becoming aquatic adults. In western North America
occurs another species of newt.

The tiger salamander (Fig. 179) is an inhabitant of fresh water
all over this country. It is dark-colored, marked with yellow
spots, and reaches a length of from six to nine inches. If
forced to breathe air, the tiger salamander loses its gills, but if
water is always at hand, the gills persist throughout life as func-

THE AMPHIBIA 301

tional respiratory organs. Salamanders in general feed on
worms, insects, crustaceans, and other small animals.

Several of the salamanders have legs that are very small or
else absent altogether. One of these, known as the ‘“‘ mud eel ”’
(Fig. 180), inhabits the ponds and rivers of the South from
Texas to North Carolina. It burrows in the mud of ponds and
ditches or swims by undulations of the body. The fore limbs of

Fic. 179. — Tiger salamander. (Photograph of living animal furnished by
American Museum of Natural History.)

the mud eel are very small and the hind limbs are entirely
lacking.

Tailless Amphibians. — The tailless amphibians, the toads
and frogs, are much more numerous than their tailed relatives.
They are all very similar in structure, although the different
species vary in size and general appearance. In North America
there are about fifty-six species. Some of them (toads and tree
frogs) live on land, but others (water frogs) spend a large part
of their time in the water. The terrestrial species possess only
slightly webbed hind feet or no webs at all. They crawl or hop
on land, burrow in the earth, or climb trees. Dark, moist hiding
places are usually required, and most of them take to water only
during the breeding season.

302 PRACTICAL ZOOLOGY

The leopard frog (pp. 245-267) is the most common of the
water frogs, but it has a number of relatives in this country
worth mentioning. Of these the bullfrogs are the largest,
reaching a length of six or eight inches. They possess a

ir
|
| q

|
|
{
\

Fic. 180. — Mud eel. (Photograph of living animal from Report N.Y.
Zool. Soc.)

deep, bass voice like that of a bull, and when a number are
engaged in a nocturnal serenade, they can be heard for a con-
siderable distance. Bullfrog tadpoles do not become frogs the
first year as do those of the leopard frog, but transform during
the second or even the third year.

THE AMPHIBIA 303

The green frog
lives in eastern
North America.
It can be distin-
guished from the
bullfrog by the
presence of two
folds of skin along
the sides of the
back (Fig. 18r).

The tree frogs
(Fig. 182) are
often, erroneously

called tree toads. Fic. 181. — Green frog. (Photo. of living animal
They have adhe- furnished by American Museum of Natural History.)

sive disks on their toes and fingers, which enable them to climb
trees, and are provided with large vocal sacs which give them
a correspondingly
loud voice.

The common tree
frog is about two
inches long. It has
the power of slowly
changing its color
so as to produce a
perfect harmony
between itself and
its surroundings.
These colors are due

Fic. 182. — Tree frog. (Photo. of living ani- to pigments in the
mal furnished by American Museum of Natural skin, usually brown,
Heyy) black, yellow, or red,
which are contained in cells called chromatophores (Fig. 184).
The power of changing its colors is possessed by most Amphibia,

but especially by the tree frogs. The black chromatophores are

304

PRACTICAL ZOOLOGY

branching cells which may spread out or contract, as shown in
When expanded, the pigment covers a larger

Figures 183-185.

Fic. 183. — A pigment cell of a frog ex-

tended.

phibia.

(After Verworn.)

area and consequently
gives the skin a darker
color. The yellow pig-
ment is contained in spher-
ical golden cells. The
green color results from
the reflection of light
from granules in the skin
through the golden cells.
Most of the color changes
are due to changes in the
concentration of the black
and yellow pigments.
Regeneration.—The
power of regenerating lost
parts is remarkably well
developed in many Am-

For example, the hand of a two-year-old axolotl was

cut off, and in twelve weeks a complete hand was regenerated

in its place.

The newt has been

observed to regenerate both limbs

and tail.

The frogs and toads are

apparently unable to regenerate lost

Fic. 185. — A pig-
ment cell of a frog
in a further state of
contraction. (After
Verworn.)

parts to any con-
siderable extent,
except in the
early stages. As
a general rule,
the younger tad-

Fic. 184. — A pigment cell of a
frog in state of contraction.

poles regenerate limbs or tail more readily

than older specimens.

Amphibians have a

distinct advantage in the possession of the power of regenera-
tion; for although an encounter with an enemy may result in

THE AMPHIBIA 305

the loss or the mutilation of limb or tail, new parts rapidly grow
out, and they are not permanently inconvenienced by the loss.

Hibernation. — Many Amphibia bury themselves in the mud
at the bottom of ponds in the autumn, and remain there in a dor-
mant condition until the following spring. During this period
of hibernation the vital processes are reduced. No air is taken
into the lungs, since all necessary respiration occurs through
the skin; and no food is eaten, but the physiological activities
are carried on by means of nutriment stored in the body. The
temperature of all cold-blooded vertebrates — lampreys, sharks,
rays, fish, amphibians, and reptiles — varies with the surrounding
medium. Frogs cannot, however, be entirely frozen, as is often
stated, since death ensues if the heart is frozen. In warm coun-
tries many Amphibia seek a moist place of concealment in which
to pass the hotter part of the year. They are said to estivate.

Poisonous Amphibia. — The poison glands of the leopard
frog have already been mentioned (p. 253). The toads and
certain salamanders and newts are also provided with poison
glands. Asa means of defense the poison is very effective, since
an animal that has once felt the effects of an encounter with a
poisonous amphibian will not soon repeat the experiment. No
amphibians, however, are harmful to man.

The Common Toad.— One of the commonest and most
valuable of all amphibians is the toad (Fig. 186). This much-
detested animal is not responsible for all the evil things laid up
against it. It does not cause warts to appear on the hands that
touch it; it is not poisonous; and it will not, if killed, make the
cows give bloody milk, as is often believed in the country. On
the other hand, toads are not only perfectly harmless to man, but
are among the most beneficial of all animals because they de-
stroy harmful insects and slugs. They live in our gardens if
they can find a damp and hidden retreat, and they sally forth
toward evening in search of insects and other small animals,
most of which are injurious to vegetation. In twenty-four hours
the toad consumes “‘a quantity of insect food equal to about

x

300 PRACTICAL ZOOLOGY

four times its stomach capacity.’’ This capacity may be judged
from the fact that sixty-five gypsy-moth caterpillars have been
found in one stomach, fifty-five army worms in another, and
seventy-seven thousand-legged worms in a third.

One method, therefore, of ridding a garden or an estate of
injurious insects is to establish a number of toads in it. In

Fic. 186. — Amcrican toad. (Photo. of living animal from Davenport.)

England and France toads are purchased for this purpose. This
method will certainly be successful, but it is far better to spread
the knowledge of the toad’s real status and thus prevent the
destruction of these beneficial creatures.

Toads become strongly attached to one locality and will re-
turn to it year after year at the end of the breeding season.
In the spring they migrate to the nearest body of water in which
to lay their eggs. A toad lays about ten thousand eggs, almost
all of which hatch. The tadpoles are destroyed by birds, fish,
and large water insects, so that only a few ever have a chance to
change into toads. Those that do succeed in reaching the
adult stage should certainly be protected.

THE AMPHIBIA 307

The results of a campaign of education are well shown by an
experiment carried on by Professor Hodge at Worcester, Mass.
Professor Hodge reports as follows : —

“ While walking once around a small pond I counted 200 toads
dead or mangled and struggling in the water, and learned next
day that two boys had killed 300 more, carrying them off in an
old milk can to empty on a man’s doorstep. This 500 does not
represent probably one tenth of the number killed by the chil-
dren that spring (1897) around this one pond. A ‘ civilization’
in which such abuses of nature are possible ought to be eaten
alive by insects, and something must be fundamentally wrong
with a system of public education that does not render such a
thing impossible. My first impulse was to get a law passed and
appeal to the police, but the wiser counsel of a friend prevailed,
and I was induced to try education of the children instead.
Accordingly, a prize of $10 was offered to the Worcester school
child who would make the best practical study of the ‘ Value of
the Common Toad.’ This was offered March 31, 1898, and
there was no evidence that a single toad was harmed at the pond’
the following April and May. I would’ have been well satisfied
had such a result been attained in five years. The fact that it
came within thirty days reveals the possibility of nature study
when united to human interest.”

The Economic Importance of Amphibia. — Only certain frogs,
toads, and salamanders are abundant enough to be of any par-
ticular economic importance. These, however, are probably
without exception mostly beneficial because of the injurious
insects and other animals they destroy. The common toad is
the most beneficial of all, but others are also valuable.

Besides their importance as destroyers of insect pests certain
amphibians, especially bullfrogs, are eagerly sought as an article
of food. In certain states attempts have been made to prevent
the wholesale destruction of frogs, and some efforts have been
made to carry on frog “‘ farming,” but these have not been very
successful in close quarters because the frogs eat each other, and

308 PRACTICAL ZOOLOGY

their food of small animals can be obtained for them only with
difficulty.

Finally the fact should be mentioned that many of the things
we know about the physiology of animals have been learned
from experiment on frogs, in fact the frog seems to have been
“especially designed as a subject for biological research.”’

REFERENCES

The Biology of the Frog, by S. J. Holmes. — The Macmillan Co., N. Y. City.

The Frog Book, by Mary C. Dickerson. — Doubleday, Page and Co., N. Y.
City.

Nature Study and Life, by C. F. Hodge. — Ginn and Co., Boston, Mass.

The Habits, Food, and Economic Importance of the American Toad, by
A. H. Kirkland. Bulletin 46, Hatch Experiment Station, Amherst,
Mass.

CHAPTER XXXIII
THE REPTILIA

THE word “reptile” means to most people a slimy, poisonous
creature, but as a matter of fact reptiles are not slimy and very
few of them are poisonous. There are four large groups of rep-
tiles, and the members of any one group differ strikingly from
those of the others. They are the turtles, snakes, lizards, and

Fic. 187. — Diagrams of the extinct reptiles, called pterodactyls, in various
positions. (From Seeley.)
crocodiles. Reptiles live in all sorts of habitats, in the sea and in
fresh water, in the ground, on the ground, and in trees. In pre-
historic times there were reptiles that could fly (Fig. 187), but
none of them exist now.
309

310 PRACTICAL ZOOLOGY

TURTLES

Turtles are favorable reptiles for laboratory study because
of their size, because they are easily obtained, and because they
are not so generally abhorred as are most other species. The

Fic. 188. — Skeleton of a turtle, ventral aspect; plastron removed to one
side.

c, costal plates; co, coracoid; e, entoplastron; ep, epiplastron; f, fibula;
fe, femur; h, humerus; hpp, hypoplastron; hyp, hyoplastron; jl, ilium;
js, ischium; m, marginals; nu, nuchal; pb, pubis; psc, precoracoid; py,
suprapygal; 1, radius; sc, scapula; t, tibia; u, ulna; xp, xiphiplastron.
(From Zittel.)
most striking thing about a turtle is its protective shell (Fig. 188).
In most species this covers almost the entire body, and the
legs, head, and tail can be drawn into it. Such an animal does

not need to run away at the approach of an enemy, and the turtle

THE REPTILIA 311

is extremely slow in its movements. The shell of the turtle
consists of bone. It does not really cover the body since it lies
beneath a coat of horny shields.

Method of Feeding. — Of great service to an animal of the
turtle’s habits of sluggish locomotion is the long, flexible neck
which enables it while lying quietly in one place to reach out
in any direction for the insects and other small animals upon
which it feeds. Some turtles live entirely upon vegetation,
which of course can be obtained without rapid locomotion.
The large mouth is toothless, but the margins of the jaws are
edged with horny plates adapted to cutting. The snapping
turtle can bite off a finger and large specimens can even ampu-
tate a hand.

Internal Organs. — The turtle’s digestive system differs very
little from that of the frog. Its heart also consists of the same
parts, two auricles and one ventricle, but the ventricle is divided
into two chambers by a perforated partition. The young of the
turtle as well as the adults breathe with lungs, no gills being
present.

Nervous System. — Slight advances in the development of the
nervous system over that of the frog are evident in the turtle.
The cerebral hemispheres of the brain are larger, anda distinction
can be made between an outer gray layer and a central white
portion. The cerebellum is also larger, indicating an increase in
the power of correlating movements.

Sense Organs. — The eyes are small, with an iris which is
often colored. The sense of hearing is fairly well developed,
and turtles are easily frightened by noises. The sense of smell
enables the turtle to distinguish between various kinds of food
both in and out of the water. The skin over many parts of the
body is very sensitive to touch.

Egg Laying. — Turtles are bisexual. Their eggs are whitish,
spherical, or oval in shape, and covered with a more or less hard-
ened shell. They are laid in the earth or sand a few inches from
the surface, where they are left to hatch.

PRACTICAL ZOOLOGY

312

(OD pur seg ‘Aepayqnog Aq WS8uAsdog = ‘;ewrue SUIAT] JO “OJOYg) *ay}4n} Surddeusg — ‘6g1 ‘org

a Se ap EEE > --

Fic. 190. — Musk turtle. (Photo. of living animal furnished by
American Museum of Natural History.)

Fic. 191. — Diamond-back terrapin. (Photo. of living animal
furnished by American Museum of Natural History.)

314 PRACTICAL ZOOLOGY

Habitat.— Turtles are usually present in all fresh-water streams
and ponds with muddy bottoms. In some parts of the country
certain species live on land, and some parts of the sea are inhab-
ited by others. The names turtle, tortoise, and terrapin are often
confused, illustrating the value of scientific terms (see p. 106).

Fic. 192. — Soft-shelled turtle. (Photo. of living animal. Copyright by
Doubleday, Page and Co.)

Fresh-water Turtles. — The common turtles living in muddy-
bottomed streams and in ponds are the snapping turtle, mud
turtle, painted terrapin, pond turtle, and soft-shelled turtle.

The common snapping turtle (Fig. 189) is a voracious, car-
nivorous animal feeding on fish, frogs, water fowl, etc., and
does not hesitate to attack man with its formidable beak, often

THE REPTILIA a8

inflicting severe wounds. It must be fierce in order to protect
itself, since its shell is very small and offers little protection for
the body.

The common musk turtle (Fig. 190) has a shell three or four
inches long, a large head, and broadly webbed feet. Like the
snapping turtle it is voracious and carnivorous. The disagree-
able odor it emits
when captured has
given it its name.

The painted terra-
pin loves to sun
itself upon a log
or protruding rock,
from which it slides
off into the water
when disturbed. Its
shell, which is beau-
tifully colored, is
sometimes cleaned,
varnished, and used
as an ornament.

The diamond-back
terrapin (Fig. 191) is
famous as an article
of food. It lives in
the salt marshes of

‘ Fic. 193.— Box tortoise. (Photo. of living
the Atlantic coast. animal furnished by American Museum of Natural

Persistent persecu- History”)

tion by market hunters has caused a great decrease in the
number of these animals and a corresponding increase in their
value. The price has risen from twenty-five cents for a large
specimen to seventy dollars per dozen for small ones.

The soft-shelled turiles (Fig. 192) are thoroughly aquatic and
have large, strongly webbed feet. The body is flat, the neck is
long and very flexible, the nose terminates in a small proboscis,

316 PRACTICAL ZOOLOGY

and the shell is leathery without shields and with only a few
scattered bones. These turtles are voracious and carnivorous,
and when attacked, they are very vicious. The shells as well as
other parts of the animals are used as food and are regularly sold
in the markets.

Terrestrial Turtles.— The turtles that are terrestrial in habit
include the box turtle, gopher tortoise, and giant tortoise.

Fic. 194. — Giant tortoise. (Photo. of living animal. By permission.
Copyright 1910 by Sturgis and Walton Co.)

The common bow turtle (Fig. 193), which occurs in the North-
eastern States, lives in dry woods and feeds on berries, tender
shoots, earthworms, and insects. The lower part of the shell
is hinged transversely near the center so that it can be closed
completely when the animal is in danger.

The grant tortoises (Fig. 194) are interesting not only because of
their great size, but also because they are living representatives
of the fauna of past ages. Some of those captured on the Galap-

THE REPTILIA 317

agos Islands weigh over three hundred pounds and are probably
over four hundred years old. These giant tortoises live on
cacti, leaves, berries, and coarse grass. They have been perse-
cuted for food and for scientific purposes so persistently that
extermination in a wild state seems certain within a few years.
Sea Turtles. — The sea turtles are the giants of the turtle
class. The green turtle (Fig. 195), so called because of the green

tia

Fic. 195. — Green Turtle. (Photo. of living animal furnished by American
Museum of Natural History.)

color of its fat, sometimes has a shell four feet in length, and
weighs 500 pounds. It is famous as an article of food, and is
common in the markets of the large cities of the eastern United
States. It feeds largely on aquatic vegetation, and probably
eats fish and other animals also.

The hawk’s-bill or tortoise-shell turtle (Fig. 196) has the shields
of its carapace arranged like the shingles on a roof. These
shields of which a large specimen yields about eight pounds, are
the “ tortoise shell” of commerce. The shields are detached
either after the turtles have been killed and immersed in boiling

PRACTICAL ZOOLOGY

318

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‘yeuu’e Suray jo ‘oJ0Yg) [9414 [IIq-s, Yep — “961 “Og

|
ij

THE REPTILIA 319

water or after the living animals have been suspended over a
fire. In the latter case the animals are liberated and allowed to
regenerate a new covering of shields. The regenerated shields,
however, are not of commercial value. Hawk’s-bill turtles are
smaller than grecn turtles, reaching a weight of about thirty
pounds and a shell length of thirty inches. They are carnivo-
rous, feeding largely on fish and mollusks.

The leathery turtle is the largest of all living turtles, sometimes
attaining a weight of a thousand pounds. It has a leathery
covering over the shell instead of horny shields. It inhabits
tropical and semitropical seas and goes to land only to deposit
its eggs. The limbs are modified as flippers for swimming.
The flesh is not used for food.

LIZARDS

The lizards resemble salamanders in their general outlines, but
as already noted (p. 299), they are covered with an exoskeleton of
scales. Among the common species living in this country are the
chameleons, iguanas, horned “ toads,” gila monsters, and skinks.

The chameleon lives in southeastern United States and in Cuba.
It is able to change its color very rapidly so as to match its sur-
roundings, thus concealing itself and gaining protection.

From southwestern United States southward huge iguanas
(Fig. 197) are commonly seen lying on stone fences or on the
limbs of a tree sunning themselves. They reach a length of six
feet, feed on insects and other small animals, and are considered
very good to eat by the natives of tropical America.

The horned “ toads” (Fig. 198) of the western United States
are really lizards. Their bodies are provided with a very heavy
covering of scales and spines, which, besides protecting them
from enemies, prevents the evaporation of water, thus enabling
them to live in hot, dry, desert regions. ~ Specimens can be kept
in the laboratory if placed in a warm, dry place. They feed on
insects in their natural habitat and will thrive on meal worms
in captivity.

320 PRACTICAL ZOOLOGY

Fic. 197. Iguana. (Photo. furnished by American Museum of Natural
History.)

Fic, 198. — Horned “ toad.’ (Photo. of living animal. Irom Davenport.)

THE REPTILIA 321

_ The common lizards of the eastern and central United States
are called skinks (Fig. 199). Young skinks have a blue tail and
black body, with five long yellow stripes on the sides. The adult
females retain these colors, but the males acquire a bright red
head and a dull, olive-brown body.

Fic. 199. — Skinks. (Photo. of living animals furnished by American Museum
of Natural History.)

The only poisonous lizard in this country is the gila monster
of Arizona and New Mexico (Fig. 200). This reptile is about
one foot in length and heavy bodied. Its bright red and black
colors make it quite conspicuous (warning coloration, see p.
30), but its poisonous nature is an excellent protection from
enemies. Gila monsters are, as a rule, not harmful to man.
Their grooved poison teeth (fangs) are in the lower jaw so the
animal must turn over on its back before the poison will flow

down into a wound.
Y

322 PRACTICAL ZOOLOGY

The glass “ snake” (Fig. 201) is a lizard without limbs and
with a very brittle tail. It may easily be confused with the
true snakes, but is distinguished from them by the presence of
ear openings and movable eyelids.

Fic. 200. — Gila monster. (Photo. of living animal. From Metcalf.)

SNAKES

The snakes are degenerate reptiles entirely without legs except
in a few examples like the python, on which spearlike remnants
occur. The exoskeleton of scales is shed several times a year and
a fresh, clean covering acquired. Snakes require a rough surface
for locomotion on land. They press the scales on the ventral
surface against the ground, and by sidewise undulations draw the
body forward. Snakes that normally live in the water are able
to swim rapidly by similar undulations, and most of the terrestrial
species can also swim.

The eyelids of the snake are not movable as are the lizard’s,

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324 PRACTICAL ZOOLOGY

but they are fused over the eyeball. In the center is a trans-
parent part through which the reptile receives light waves.
Ear openings are lacking and the sense of hearing is consequently
very feeble. The long forked tongue, however, which is often
erroneously considered injurious, is very sensitive to vibrations
and probably serves as an auditory organ.

As in the amphibians and lizards, the teeth are sharp, conical
structures fitted for holding struggling animals. They are
curved inward and help the snake force the food down the throat.
A snake can swallow objects much thicker than its own body;
this is due to the elasticity of the body and to the fact that the
jaws are loosely fastened together.

Most of the snakes lay eggs, but in a few cases, for instance the
common garter snake, the eggs hatch within the body of the
mother and the young are then born. There is no reason for be-
lieving the popular story that snakes swallow their young to
protect them and then disgorge them again when the danger is
past.

Fic. 202. — Garter snake. (Photo. of living animal. From Davenport.)

Harmless Snakes. — Only a few of the snakes inhabiting
North America are poisonous; most of them are either of no
special importance or else beneficial. The commonest snakes

THE REPTILIA 325

are the grass or garter snakes (Fig. 202) which occur all over this
country. The body is olive color with three long yellow stripes;
this renders it rather inconspicuous and enables it to creep upon the
frogs, toads, fishes, and earthworms which serve it as food, with-
out being seen (aggressive coloration, see p. 30). The eggs
of the garter snake hatch within the body and the young emerge
in August.

Contrary to general belief, most of the water snakes are as harm-
less as the garter snakes. Like the frogs, they live in swampy
places, and escape into the water when approached closely.
The common water snake is frequently called “‘ water mocca-
sin,” but these two species are quite different.

Fic. 203. — Black snake or ‘‘ blue”’ racer. (Photo. by Hegner.)

Among the other harmless snakes that one is apt to encounter
are the black snake or “ blue” racer (Fig. 203), which lives in dry,
open situations and feeds on small animals such as mice, frogs,
and young birds; the milk snake, which is wrongly accused of
stealing milk from cows; the hog-nosed snake, commonly known
as the “ puff adder,” “ spreading viper,” or “‘ blow snake,” be-

(a9

326 PRACTICAL ZOOLOGY

cause of its habit of trying to frighten an enemy by expanding
its neck like a cobra and hissing; and the king snake, which feeds
on other snakes, hence its name.

Constrictors. — There are no very large snakes in North
America, but in tropical South America the boa constrictor (Fig.
204) reaches a length of eleven feet, and the water boa or ana-
conda a length of over seventeen feet. The largest of all snakes

Fic. 204. — Boa constrictor. (By permission. Copyright by Sturgis and
Walton Co.)

is the regal python of Burma (Fig. 205), which may grow to be
thirty feet long. All of these large snakes are constrictors; that
is, they capture birds and mammals and squeeze them to death
in their coils. Very few of them are dangerous to man.
Poisonous Snakes.— The only poisonous snakes in this
country are the rattlesnakes, copperhead, water, moccasin,
harlequin snake, Sonoran coral snake, and a few small species in-

THE REPTILIA 327

Fic. 205.— Python. (By permission. Copyright by Sturgis and Walton Co.)

Fic. 206. — Rattlesnake. (Photo. by Hegner.)

328 PRACTICAL ZOOLOGY

habiting the southern part of the United States that are prac-
tically harmless.

The rattlesnakes (Fig. 206) occur almost all over the United
States, but are particularly abundant in the deserts of the south-
west. The largest species, the diamond-back rattlesnake, occurs
in the Southeastern States, and reaches a length of over eight
feet. The banded rattlesnake is a resident of the Eastern States;
the massasauga inhabits the Central States; and the horned
rattlesnake is common in the deserts of the Southwest.

The rattles of these snakes are strings of bell-shaped pieces
of exoskeleton, each piece representing what was once the end
of the tail. The skin is shed several times a year, but the bell-
shaped “ button ” at the end of the body does not come off, being
added to the rattles already present. Rattles are often lost so
that the age of the snake cannot be determined by counting
them. The rat-
tles are used to
warn other ani-
mals of the pres-
ence of the snake;
when vibrated,
they produce a
buzzing sound.

The poison ap-
paratus of the rat-
tlesnake (Fig. 207)
consists of a pair
of poison glands
lying above the
roof of the mouth,
which are con-

Tic. 207.— Poison apparatus of rattlesnake.
(Photo. furnished by American Museum of Natural nected by ducts

History. : :
Si with a pair of

long, hollow teeth, the fangs, situated near the outer end of the
upper jaw. When the snake strikes, the jaws are opened very

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330 PRACTICAL ZOOLOGY

wide and the fangs are thrust into the victim. Then certain
muscles force the poison from the poison glands through the
hollow fangs into the wound. Extracting the fangs from one of
these snakes does not render it harmless for long, since there
are a number of pairs of small teeth held in reserve, which soon
grow into functional fangs.

The common érealment for snake bite is the administering of
alcohol and sucking the wound. Neither of these is of much

Fic. 209. — Copperhead snake. (Photo. of living animal furnished by
American Museum of Natural History.)

benefit. The first thing that should be done is fo stop the flow
of blood toward the heart by applying a ligature above the
wound. Then incisions should be made through the wound to
get rid of as much poison as possible, and a solution of potassium
permanganate should be injected about the wound to destroy
the venom. An antivenin has been produced which when in-
jected into the body destroys the venom in the blood, but unfor-
tunately the poison from every kind of snake requires a different
sort of antivenin.

The water moccasin (Fig. 208) is a very poisonous snake. It
lives in the swampy lands of the Southeast, and reaches an

THE REPTILIA » 331

average length of four feet. This species, the copperhead, and
rattlesnakes are all known as pit vipers because of the presence
of a deep pit between each eye and the nostril. These pits are
so small, however, that a snake must be examined rather closely in
order to determine whether or not they are present. Hence one
must rely on other characteristics to identify them at a distance.

The copperhead (Fig. 209) is another poisonous snake of the
southeastern United States. It occurs on the plantations and in
or near forests, and is about two and one half feet long.

The harlequin snake and coral snake are so small as to be of
very little importance, but their relative, the cobra-de-capello
of the Orient, is a very dangerous reptile. Ina single year (1908)
about twenty-thousand natives were killed by cobras in India.

CROCODILES AND ALLIGATORS

Crocodiles and their near relatives look very much like large
lizards (Fig. 210). They are adapted for life in the water, with
the toes of the hind feet more or less webbed, and the tail com-
pressed laterally, making it an effective swimming organ. The
exoskeleton of the crocodile consists of a thick, leathery skin,
covered with horny scales and horny plates, and is, therefore, a
good protection from injury. Several of the internal organs of
these reptiles are worth mentioning here. The ventricle of the
heart is completely divided into two parts by a partition (see p.
311), and the body cavity is divided into two chambers as in
mammals, the anterior chamber containing the lungs.

The American crocodile occurs along the streams from Florida
southward into South America. Its head is broad at the base
and narrow at the snout, whereas that of the alligator is wider
at the snout. The crocodile reaches a length of fourteen feet.
When in the water it floats at the surface with just its eyes and
the nostrils at the end of the snout protruding. It can thus
both see and breathe without itself being seen. The crocodile
of Africa is a very dangerous man eater and kills hundreds of
natives every year.

332 PRACTICAL ZOOLOGY

There are only two species of alligators in the world; one lives
along the streams of southeastern United States, the other is
restricted to China. The alligator has a broad snout, but other-
wise resembles the crocodile in general appearance. Its habits
also are similar. The twenty to forty eggs are laid in a mound
of muck and left there to hatch.

The crocodiles of India are known as gavials. Their snouts
are long and slender, and their bodies attain a length of more

ee

D “

I'tc. 210. — Alligators. (Photo. by Hegner.)

than twenty feet. Usually they are satisfied with fish as food,
but they sometimes attack man.

The Economic Importance of Reptiles. — The food of reptiles
consists of both animals and plants. The animals eaten belong
to practically all classes. Many of the snakes live almost en-
tirely upon birds and mammals. Frogs, fish, and other reptiles
are favorite articles of food. Most of the smaller species of rep-
tiles feed upon worms and insects. In general it may be stated
that reptiles do very little damage in destroying animals and
plants for food, but they are often of considerable benefit, since
they kill large numbers of obnoxious insects and other forms.

The turtles and tortoises rank first as food for man. Es-

THE REPTILIA 333

pecially worthy of mention are the green turtle, the diamond-
back terrapin, and the soft-shelled turtle. It seems possible that
turtle farms might prove commercially successful in some parts
of this country if éstablished on land useless for other purposes.
Certain lizards, such as the iguana of tropical America, are
a valuable addition to the food supply in their localities.

The skins of the crocodilians are used rather extensively for
the manufacture of articles that need to combine beauty of sur-
face with durability. The alligators in this country have de-
creased so rapidly because of the value of their hides that they
will be of no great economic importance unless they are con-
sistently protected or grown on farms. Of less value are the
skins of certain snakes. Tortoise shell, especially that pro-
cured from the horny covering of the carapace of the hawk’s-bill
turtle, is widely used for the manufacture of combs and orna-
ments of various kinds.

As previously stated, the poisonous snakes of the United
States are of very little danger to man. In tropical countries,
especially India, venomous snakes cause a larger death rate
than that of any other group of animals. The gila monster,
which is one of the few poisonous lizards, and the only one in-
habiting the United States, very seldom attacks man, and
probably never inflicts a fatal wound.

REFERENCES

The Reptile Book, by R. L. Ditmars. — Doubleday, Page and Co., N. Y.
City.

Reptiles of the World, by R. L. Ditmars. — Sturgis and Walton Co., N. Y.
City.

be,

Forehead \ /

Mos teil. 1S
UpperMandible>k

L ower andiblexs

Lesser

= ON -Median | Wing Coverts

Throati-7* -Greater,
Lar? 2y-2-¢ Secondaries
Lreast : . \> é eZ Rump ;
Wa ph ~~) Ye L-— Tper Tai! Coverts

Tail

Fic. 211. — Diagram showing names applied to the parts of a bird’s body
(From Wright.)

Fic. 212. — Pigeons in flight. (Photo. by Hegner.)
334

CHAPTER XXXIV

THE STRUCTURE AND ACTIVITIES OF BIRDS

Birps are to the majority of people the most interesting of
all vertebrates. They are easily distinguished from any other
animals by the presence of feathers. Besides this, most birds
possess wings and are able to fly. Their excellent locomotor
powers have enabled birds to become distributed all over the
world and to establish themselves in every habitable region.

The Body Built for Flight. — The body of a bird is in general
built for flight (Fig. 211). Its shape is such as to offer the least
resistance to movement through the air, and its bones are closely
united, giving the rigidity required by a body supported only by
air (Fig. 212). In the first place, although the vertebre in the
neck move freely upon one another, those of the back are closely
united, forming a firm axis (Fig. 213). The thorax is strongly
supported by ribs which are entirely of bone and are held to-
gether by projections called uncinate processes. The long wing
bone, although able to move freely, is more firmly connected
with the shoulder girdle than is the bone of the fore limb in
other vertebrates. Finally, the breastbone or sternum bears a
projection or keel to which the enormous wing muscles are at-
tached, and many of the bones are hollow and therefore decrease
the specific gravity of the body. These features are all corre-
lated with the flying habits of the birds.

The Wings as Organs of Flight. — The principal organs of
flight are, of course, the wings. Whendevoidof theirfeathers, the -
wings of a bird seem quite ineffective, but the bones within them
are very strong and closely knit together. These bones are
similar to those in the fore limbs of other vertebrates except the

335

Fic. 213. — Skeleton of the
common fowl, male.

1, premaxilla; 2, nasal;
8, lachrymal; 4, frontal;
5, mandible; 6, lower tem-
poral arcade; 7, tympanic
cavity ; 8, cervical vertebra;
9, ulna; 10, humerus; 11, ra-
dius ; 12, carpo-metacarpus;
13, first phalanx of second
digit; 14, third digit; 15,
second digit; 16, ilium; 17,
ilioischiatic foramen;
18, pygostyle; 19, femur;
20, tibiotarsus; 21, fibula;
22, patella; 23, tarsometa-
tarsus; 24, first toc; 25,
second toe; 26, third toe;
27, fourth toe; 28, spur;
29, pubis; 30, ischium; 31,

clavicle; 32, coracoid; 33, keel of sternum; 34, xiphoid process.

Shipley and MacBride.)

336

(From

THE STRUCTURE AND ACTIVITIES OF BIRDS 337

cyclostomes and fishes, but they are modified somewhat by the
omission of several of the digits and the union of certain of the

E

ue
RA

Fic. 214. — The most important forms of birds’ feet.

a, clinging foot of a swift; b, climbing foot of woodpecker; c, scratching
foot of pheasant; d, perching foot of ouzel; e, foot of kingfisher; f, seizing
foot of falcon; g, wading foot of stork; h, running foot of ostrich; i, swimming
foot of duck; k, wading foot of avocet; 1, diving foot of grebe; m, wading
foot of coot; n, swimming foot of tropic-bird. (From Sedgwick.)

bones that remain. To this axis of bones and muscles and ten-

dons the long wing feathers are attached.
Z

338 PRACTICAL ZOOLOGY

These feathers convert the narrow wings into broad surfaces
that enable the bird to make powerful strokes against the resist-
ance of the air. The body of the bird is much heavier than the

Fic. 215. — The most important forms of birds’ beaks.

a, flamingo; b, spoonbill; c, yellow bunting; d, thrush; e, falcon; f, duck;
g, pelican; h, avocet; i, black skimmer; k, pigeon; 1, shoebill; m, stork;
D, arocari; o, stork; p, bird of paradise; q, swift. (From Sedgwick.)

atmosphere and, unlike that of a land animal in walking, it must
be sustained as well as propelled when flying. | Downward
strokes of the wings prevent the bird from falling just as a

THE STRUCTURE AND ACTIVITIES OF BIRDS 339

swimmer keeps at the surface by the movements of his arms.
These same strokes of the bird are made at such an angle that
the wings form an inclined plane, thereby propelling the body
forward (see insect flight, p. ro). When brought forward, the
wings are bent at the wrist joint, with the narrow edge in Miront,
so that very little resistance is encountered.

Steering the Body during
Flight. — The wings also in
part steer the bird through
the air, since a more powerful
stroke on one side swerves
the body toward the other
side, just as does a stronger
pull on one oar of a boat.
Steering is, however, largely
done with the tail, which
serves as a rudder, directing
the body upward or down-
ward and from side to side
according to the position in
which it is held.

How the Feet are Used. — F's. 216. — The structure of feathers.
While on the ground birds I. Contour feather, a, quill; ¢,

vane; e, shaft.
walk, Tun, Or hop, and when II. Part of shaft (a) with two barbs
i RECS, they cling KO ie py Two barbules bearing hooklets
twigs with their claws. Their (¢). (From Coleman.)
hind limbs must therefore be
adapted for these various purposes, as well as for obtaining
food, for building nests, and for fighting with other animals.

FEET ARE ADAPTED TO VaRrIouS PurRposES (Fig. 214). — In
birds that ordinarily perch on limbs the feet are strong and fitted
for grasping. Swimming birds have their toes entirely or par-
tially connected by webs. Wading birds have long legs and long,
slender toes which prevent them from sinking into the mud.
The toes of the birds of prey are very strong and bear sharp,

340 PRACTICAL ZOOLOGY

curved claws for capturing their prey. Birds that spend most
of their time in flight, like the swift, possess weak feet. Usually

>

on RE BW Ms M2 Ne 8
0 MP PD O2 =
PC le eu oe See Me
Bo *
Su : SLL

Fic. 217. — Anatomy of the pigeon.

A, nostril; AD, ad-digital primary feather; B, external auditory meatus;
BW, bastard wing; C, cesophagus; CA, right carotid artery; D, crop; DA,
aorta; E, keel of sternum; F, right auricle; G, right ventricle; HV, hepatic
vein; H1, left bile-duct; H2, right bile-duct; I, distal end of stomach; IA,
right innominate artery; IV, posterior vena cava; JA, left innominate artery;
JV, right jugular vein; K, gizzard; L, liver; M, duodenum; MD, mid-digital
primary feathers; MP, metacarpal primaries; M41, preaxial metacarpal;
M2, middle metacarpal; M3, postaxial metacarpal; N, cloacal aperture;
N1, preaxial digit; O, bursa Fabricii; 01, proximal phalanx of middle digit ;
O02, distal phalanx of middle digit; P, pancreas; PA, right pectoral artery;
PD, predigital primary; PV, portal vein; P1, first pancreatic duct; P2, second
pancreatic duct; P83, third pancreatic duct; Q, pygostyle; R, rectum; RC,
radial carpal bone; RX, rectrices; R1, ulnar digit; S, ureter; SA; right sub-
clavian artery; SV, right anterior vena cava; T, rectal diverticulum; U,
kidney; UC, ulnar carpal bone; V, pelvis; W, lung; X, humerus; Y, radius;
Z, ulna. (From Marshall and Hurst.)

there is one toe behind and three in front, but in many wood-
peckers there are two in front and two behind, an arrangement
which doubtless enables them to cling to the bark of trees more

THE STRUCTURE AND ACTIVITIES OF BIRDS 341

Fic. 218, — Paths of migration of the golden plover. (From Cooke.)

342 PRACTICAL ZOOLOGY

Fic. 219. — Nest of prairie horned lark on the ground in a field. The
darkly spotted egg is that of a cowbird. (Photo. by Hegner.)

Fic. 220. — Killdeer plover standing over her nest and four eggs among

the pebbles near a small stream. (Photo. by Hegner.)

THE STRUCTURE AND ACTIVITIES OF BIRDS 343

easily. An examination of the bones in a bird’s foot shows at
once that birds walk on their toes, that is, are digitigrade, and
not on the sole (plantigrade), as in man.

ACTION OF TOES WHILE PEeRcHING. — When at rest, the birds
often maintain themselves for hours perched on a limb, with the
toes holding the body upright. This would soon tire the muscles
if it were not for a special mechanism which automatically causes
the toes to grasp the perch. The tendon which bends the toes
passes over the
back of the ankle
joint. The weight
of the body bends
this joint, draws
the toes around
the perch, and au-
tomatically holds
the bird firmly in
place.

How the Beak
is Used. — Birds,
like turtles, are
toothless, and the
jaws are covered
by horny sheaths
which constitute
the beak. The
beak of the bird performs many of the functions of human
hands: it is used to obtain food, build nests, preen the
feathers, care for the young, etc. The bird must be able to move
its head freely if the beak is to succeed in accomplishing all
these duties. It is able to do this because the neck is compara-
tively long and the vertebre in it move easily upon one another.

BEAKS ARE ADAPTED TO VARIOUS PURPOSES. — Just as the
feet differ in different birds according to the habits of the species,
so the beaks are much modified for particular purposes (Fig. 215).

Fic. 221. — Eggs of whippoorwill laid on dead leaves
on the ground in the woods. (Photo. by Hegner.)

344 PRACTICAL ZOOLOGY

Fic. 222. — The bank of a stream showing the entrances of a kingfisher’s tun-
nel at the left and that of a bank swallow at the right. (Photo. by Hegner.)

Birds preen themselves by pressing a drop of oil from the oil
gland, which lies just above the tail, and spreading it over their

Fic. 223. — Bank swallow on its nest at the end of a tunnel in the
bank of a stream. (Photo. by Hegner.)

THE STRUCTURE AND ACTIVITIES OF BIRDS 345

feathers. Besides this general function beaks are used in many
different ways: that of the woodpecker is chisel-shaped and
fitted for digging into the wood of trees; the beak of the sparrow
that eats seeds is short and thick for crushing its food; insect-
eating birds, like the thrush, possess beaks that are longer and
not so strong; birds, like the swift, that catch insects in the

Fic. 224. — Nest and eggs of the wood pewee. The nest was built on a hori-
zontal branch of a tree 15 feet from the ground. (Photo. by Hegner.)

air have small beaks but very capacious mouths; wading birds
possess long beaks for obtaining food under water and in the
mud; and birds of prey are provided with strong, curved beaks
for tearing flesh. These are but a few of the many different
forms and uses that might be described.

Birds are Warm-blooded Animals. — The feathers are of the
utmost importance to the bird, since flight is impossible without
them. While this is their most obvious function, there are sev-
eral others just as important. Birds and mammals are warm-

346 PRACTICAL ZOOLOGY

blooded animals in contrast to all the rest of the animals, which
are cold-blooded. Warm-blooded animals consume so much
food that a bodily temperature usually greater than that of the
surrounding air is maintained. This heat is the result of the
oxidation within the cells, and the temperature is practically
constant no matter how warm or cold it is outside. Feathers
prevent the body heat from escaping by forming many air spaces
at the surface. The
temperature of the
bird’s body ranges
from 100° to 112° F.,
whereas that of man
is normally only 98.6°
F.

Feathers. — How
wonderfully effective
feathers are for the
purposes for which
they are used can
easily be determined
by examining one in
the laboratory (Fig.
216). Feathers are
embedded in pits in
the skin, the feather

Fic. 225. — Nest and eggs of the white-rumped !
shrike (butcher bird). The nest was built in a follicles. The central

hawthorn tree 10 feet from the ground. (Photo. axial rod of the feather
by Hegner.)

is the stem, and on
each side of this is a vane. The quill is that part of the stem
without vanes. If the vane is examined closely, it will be
found to consist of a great number of parallel rods, the
barbs. Each barb resembles in appearance an entire feather,
since on each side there is a row of slender projections, the
barbules. Hooklets are present on these barbules. These
hooklets hold the barbs together, and thus the entire vane

THE STRUCTURE AND ACTIVITIES OF BIRDS 347

becomes a pliable but also resistant structure, which is
strong but light and admirably adapted for purposes of flight.

Beneath the large feathers are smaller down feathers which
have a slender stem and hookless barbs. The down feathers are
very effective in preventing the escape of the body heat.

ORGS

Fic. 226. — Red-tailed hawk about to sit on her eggs. The nest was in a
birch tree 40 feet from the ground. The bird is taking her own picture by
sitting on a string which was attached to the shutter of a camera placed in a
near-by tree. (Photo. by Hegner.)

Certain hairlike feathers occur about the mouth and some-
times on other parts of the body; these are known as filoplumes.
Feathers are not embedded in all parts of the skin, but those
parts of the body without them are covered by feathers from
other regions.

Molting. — All birds change their feathers frequently. The
young, when newly hatched, are either naked or covered with
down. They soon outgrow this, just as young children outgrow
their clothes, and in the course of a week or two true feathers

348 PRACTICAL ZOOLOGY

begin to appear, and only a few spots of down remain to show
where the baby clothes still show through the contour feathers,
The first plumage is worn onlya short time; then it gives way
to a second plumage. The loss of one set of clothing and the
acquirement of another is called ‘‘molting.”’ In adult birds
molting is annual or semi-annual. All birds shed their feathers
in the autumn, after they have finished their household duties
for the season, and they
put on their heavy woolen
winter clothing intheshape
of a beautiful new set of
plumage. In the spring
many birds change their
clothes again, and at this
time acquire the gorgeous
ornaments that are every-
where noticeable just be-
fore the breeding season,
such as the elegant plumes
of the snowy heron, known
as “‘aigrettes” (Fig. 261).
Internal Organs. — Cer-
ie tain peculiarities in the in-
Fic. 227. — Downy woodpecker at en- ternal organs of birds may
ee ae eas naa aman ae be pointed out here (Fig
captured on near-by trees and is about to 217). The food is not
feed to her young within the hole. (Photo. masticated, as there are no
by Hegner.) u
teeth present. Itisstored
in an enlargement of the cesophagus, the crop, where it is
macerated. In the stomach it is acted upon by digestive juices
from a glandular portion and ground up in the muscular gizzard.
Frequently small stones are swallowed to aid in grinding up the
food.
The heart is comparatively large, and instead of a ventricle
partly divided in two, as in reptiles, there are two entirely sepa-

THE STRUCTURE AND ACTIVITIES OF BIRDS 349

rate ventricles. Birds are more active than amphibians or rep-
tiles, besides being warm-blooded, and they must therefore have
a highly developed heart for producing rapid circulation and an
especially favorable means of oxygenating the blood. Accord-
ingly we find the respiratory system highly organized. In addi-
tion to the lungs there are nine large air sacs within the body-
cavity which are connected with the lungs and which, besides
increasing the amount of air in the body, also decrease the spe-
cific gravity of the bird
and make flying easier.
Furthermore, many of the
air spaces in the hollow
bones communicate with
the air sacs.

Bird Songs and Call
Notes. — Connected with
the respiratory system is
the vocal organ or syrinx
with which birds produce
their call notes and songs.
This organ lies just where
the windpipe divides, send-
ing a branch to each lung. Fic. 228.— One young cowbird in a
It is an enlargement of the vireo’s nest. The three young vireos

: % ee were crowded out by the young cowbird.
windpipe containing a valve (photo. by Hegner.)
which vibrates when air
is forced out of the lungs and which can be tightened by muscles,
thus regulating the number of vibrations and consequently the
pitch of the sound produced.

These sounds may be divided into two kinds, call notes and
songs. Call notes form the principal language of the birds,
since anxiety, fear, and other emotions can be expressed by
them. Songs, on the other hand, are heard most frequently dur-
ing the nesting season. Usually only the males are able to sing.
The importance of learning the call notes and songs of birds

350 PRACTICAL ZOOLOGY

cannot be too strongly emphasized since they are among the
most beautiful sounds in nature, and besides, birds are so effec-
tively concealed most of the time by the foliage of the trees that
we hear many more than we are able to see.

Bird Migration. — The remarkable powers of locomotion
possessed by birds enable them to move from one part of the
country to another with comparative ease. As a result, when

Fic. 229. — Nest and eggs of least bittern. The nest was built among the
reeds above the water in a marsh. (Photo. by Hegner.)

winter approaches in temperate regions most of the birds gather
together in flocks and migrate to the warmer southern countries.
Those that remain in one locality throughout the year, like the
great horned owl and English sparrow, are called permanent
residents; those that pass through on their way south in the
autumn and on their way north in the spring, like most of the
warblers, are called migrants; and those that leave in the autumn
and return the following spring, remaining with us to nest, we
call summer residents.

Formerly, birds were supposed to hibernate during the winter
in caves, hollow trees, or, in the case of swallows, in the mud at

THE STRUCTURE AND ACTIVITIES OF BIRDS 351

the bottom of lakes and ponds. This is now known to be in-
correct, and when birds disappear in the fall, they depart to spend
the winter in a more congenial southern climate.

Migration means moving from one place to another, and the
idea of distance is emphasized. Birds are the most famous of
all animals from the standpoint of their migrations. As winter
approaches in the north temperate zone, they gather together
in flocks and move southward, returning on the advent of the
following spring.
Birds that breed
farther north spend
the, winter in parts
of the temperate zone.

One of the most
remarkable of all
migratory birds is the
golden plover. These
plovers arrive in the
“barren grounds ”
above the Arctic Cir-
cle the first week in

June (Fig. 218). In Fic. 230. — Nest and eggs of Florida galinule.

t When disturbed the sitting bird slid down the
August they fly ” rushes in the foreground into the waters of the
Labrador, where they marsh. (Photo. by Hegner.)

feast on the crowberry

and become very fat. After a few weeks, they reach the coast
of Nova Scotia, and then set out for South America, over twenty-
four hundred miles of ocean. They may or may not visit the
Bermuda Islands and the West Indies. After a rest of three or
four weeks in the West Indies or northern South America
the birds depart and are next heard from on their arrival in
southern Brazil and Argentine. Here they spend the summer,
from September to March, and then disappear. Apparently
they fly over northern South America and Central America,
and over the central portion of North America, reaching their

352 PRACTICAL ZOOLOGY

breeding grounds in the Arctic Circle the first week in June.
The elliptical course they follow is approximately twenty thou-
sand miles in length, and this remarkable journey is undertaken
every year for the sake of spending ten weeks in the bleak, tree-
less, frozen wastes of the Arctic Region.

Most birds migrate on clear nights at an altitude sometimes
of a mile or more. Each species has a more or less definite

Fic. 231. — Nest and eggs of the black tern. The eggs were laid in a
slight cavity in the muck of a marsh lined with a few dry stems. (Photo. by
Hegner.) ;

time of migration, and one can predict with some degree of ac-
curacy the date when it will arrive in a given locality. The
speed of migration is, as a rule, rather slow, and a daily rate of
twenty-five miles is about the average.

During their migrations, birds are often killed in great num-
bers by striking against objects, such as the Washington Monu-

THE STRUCTURE AND ACTIVITIES OF BIRDS 353

ah

Fic. 232. — Four young killdeers just hatched. They were able to run
about as soon as hatched. Notice their resemblance to their surroundings.
These young hatched from the eggs shown in Fig. 220. (Photo. by Hegner.)

Fic. 233. — Young blue jays. Young of this type are said to be altricial.
They are naked and blind when hatched. (Photo. by Hegner.)

2A

354 PRACTICAL ZOOLOGY

ment, lighthouses, and telegraph wires. Over fifteen hundred
birds were killed in one night by dashing against the Statue of
Liberty in New York Harbor. Birds may also be driven out to
sea or be killed by severe storms.

Many theories have been advanced to account for the mi-
gration of birds, such as the temperature and condition of the

Fic. 234. — Eggs of ostrich, hen, and humming bird, showing comparative size.
(Photo. by E. R. Sanborn.)

food supply. Other theories attempt to explain how birds find
their way during migration. The best of these seems to be the
“ follow-the-leader ” theory. According to this, birds that have
once been over the course find their way by means of landmarks,
and the inexperienced birds follow these leaders.

Mating. — Mating takes place soon after the birds return in
the spring. A few birds, like the birds of prey, remain mated
throughout life, but most of them select new mates each spring.

Nest Building. — The nests are built in almost every con-
ceivable location, and those of one species resemble one another
but differ from those built by other species. Some birds, like
the prairie horned lark, build a nest on the ground (Fig. 219);

THE STRUCTURE AND ACTIVITIES OF BIRDS 355

the ployers, such as the killdeer, scrape a little hollow in the
ground in a field or near a stream, making very little effort to
form a real nest (Fig. 220); and many birds, for example the

Fic. 235. — Two young red-tailed hawks, 10 days old, in nest shown
in Fig. 226. (Photo. by Hegner.)

whippoorwill and certain sea birds, make no nest at all, but
lay their eggs on the bare ground’'(Fig. 221).

A few species make their homes in burrows in the ground;
of these the kingfisher (Fig. 222), bank swallow (Fig. 223), and
burrowing owl are common examples.

Nests built in bushes or trees must be able to withstand the
fury of storms and are consequently more strongly constructed.

356 PRACTICAL ZOOLOGY

Mud, vegetable fibers, bark, twigs, horsehair, and thistledown
are common nesting materials (Figs. 224, 225, 226).

The woodpeckers secure a nesting place safe from most in-
truders by digging a hole in a tree (Fig. 227). No actual nest

Fic. 236 A. — Two young red-tailed hawks 17 days old. One is
behind a limb. (Photo. by Hegner.)
is made by them, but the eggs are laid directly upon the chips
at the bottom of the hole.

One bird is worthy of special mention; this is the cowbird or
lazy bird. The cowbird resembles the European cuckoo in its
nesting habits. It does not build a nest at all, but lays its eggs
in the nests of other birds (Fig. 219), usually of those smaller
than itself, and then leaves them to be cared for by the foster

THE STRUCTURE AND ACTIVITIES OF BIRDS 357

parents (Fig. 228). Often the young cowbirds are stronger and
thus starve out the rightful owners of the nest.

Many birds nest in marshy situations and are consequently
very seldom seen by most people. They are the marsh wrens,
gallinules, rails, grebes, terns, loons, bitterns, and many others.

Fic. 236 B. — Two young red-tailed hawks 27 days old and almost
ready to fly. (Photo. by Hegner.)

Their nests are built of dry rushes and other plants and sus-
pended among the rushes above the water, or are made on the
soggy ground of decaying vegetation (Figs. 220, 230, 231).
Precocial and Altricial Birds. — It is necessary to distinguish
between precocial and altricial birds in discussing the eggs and

358 PRACTICAL ZOOLOGY

young. The young of precocial birds are able to run about like
young chickens soon after they are hatched'(Fig. 232). The
eggs of these birds must be correspondingly large in order to
contain food material (yolk and white) enough to enable the
young to reach such an advanced stage in development. The
killdeer, nighthawks, bobwhites, and ducks are common pre-
cocial birds.

The young of altricial birds, on the other hand, hatch in a
very immature condition (Fig. 233) and must remain in the nest
a long time until their feathers are grown and they become strong
enough to walk or fly. Most of our common birds are of this sort.

Birds’ Eggs. — The eggs of birds are covered by a hard shell
of calcium carbonate (Fig. 234). Eggs are single cells, their
enormous size being due to the accumulation of food material
within them. The shell is either pure white, as in many of the
birds like woodpeckers and kingfishers that lay eggs in dark
places, or variously colored and covered with specks, spots, and
lines of different hues. Colored eggs are adapted to their sur-
roundings, since they are less conspicuous amidst the green vege-
tation than white eggs would be.

NuMBER OF Ecos. — The number of eggs laid in a single
nest, called a “clutch” or “ set,” is usually the same for in-
dividuals of one species, but differs in different species. The
passenger pigeon lays one egg; the mourning dove lays two;
the red-tailed hawk two or three; the robin three or four; the
blue jay four or five; the bank swallow six; the flicker and king-
fisher six or eight; and the game birds, like the bobwhite, from
a dozen to twenty.

Incubation. — The eggs must be kept warm or incubated in -
order to develop; this is accomplished by the bird sitting on
them. Sometimes the female alone performs this duty; some-
times both birds take turns; and in a few instances, like that of
the ostrich, the male alone incubates the eggs. The period of
incubation lasts from ten or twelve days among the smaller
birds to over a month in the case of the largest species.

”

THE STRUCTURE AND ACTIVITIES OF BIRDS 359

Growth of the Young (Figs. 235, 236A, 236B). — The young
hatch with a covering of down (precocial birds) or practically
naked (altricial birds). They devour large quantities of food,
principally insects, and grow rapidly. The feathers gradually

grow in, but are often different from those of the parents in
color.

REFERENCES

A Dictionary of Birds, by A. Newton and H. Gadow. — Adam and Charles
Black, London, England.

Key to North American Birds, by E. Coues. — Estes and Lauriat, Boston,
Mass.

Bird-Life, by F. M. Chapman. — D. ESE and Co., N. Y. City.

Fic. 237. — The fossil remains of the oldest extinct bird known (Archeop-
teryx). (From Zittel.)

3600

CHAPTER XXXV

SOME COMMON BIRDS OF NORTH AMERICA

Lack of space prevents us from giving a full account of the
twelve thousand or more different kinds of living birds known

at the present time, DP

and students must
therefore be referred
to books concerned
only with birds. Of the
twelve thousand de-
scribed species about
850 are known to oc-
cur in North Amer-
ica. A single state may be
inhabited by three hundred
species; for example, 326 dif-
ferent kinds of birds have
been recorded from the state
of Michigan. The number in
any particular locality de-
pends largely upon the amount
of water, swamps, and forests
in that vicinity; an average
number, is about 200; 267
have been observed in the vi-
cinity of Ann Arbor, Michigan.

Ancient Birds. — The birds
that lived on the earth thou-

Fic. 238. — Skeleton of the extinct
moa. (After Owen.)

sands of years ago differed from those alive to-day in many re-

spects.

The most ancient of these is the reptile-like bird called

362 PRACTICAL ZOOLOGY

Archeopteryx whose fossil remains were found in the rocks in
Bavaria (Fig. 237). Its jaws were provided with teeth, its tail

Fic. 239. — The kiwi, a wingless bird living in New Zealand. (From Evans.)

was long with feathers arranged along the sides, and its wings
bore claws. The fossil remains of other toothed birds have

Fic. 240. — A group of penguins or rock-happers. (From Evans.)

been discovered in the earth’s crust, notably in the state of
Kansas.
The moas (Fig. 238) have probably become extinct within the

SOME COMMON BIRDS OF NORTH AMERICA 363

past five hundred years. The remains of these peculiar birds
have been found in great numbers in caves and refuse heaps in
New Zealand, to which country they appear to have been con-
fined. Twenty or thirty species are known from these remains.
They range in size from that of a turkey to nearly ten feet
high. They were flightless, but
possessed enormous hind limbs.

Flightless Birds. — Many
birds, like the extinct moas,
possess only rudimentary wings
and therefore are unable to fly.
The ostrich succeeds in es¢ap+:
ing many of its enemies -by
running, but most of’ the'flight-
less birds are an easy préy for
man and other animals. They
have either become extinct, like
the great auk, or are nearly
all exterminated. In South
America occur some flightless
birds called rheas or New World
ostriches because of their re-
semblance to true ostriches.

Two other kinds of flight-
less birds are worthy of men-
tion: the kiwis of New Zealand
and the penguins of the Ant-
arcticregions. The kiwis (Fig.
239) are very strange-looking because their wings are so small
that they are entirely covered by the hairlike body feathers,
and the absence of tail feathers gives the bird a peculiar stumpy
appearance.

The penguins (Fig. 240) are adapted for life in the water.
The fore limbs are modified as paddles for swimming; the feet
are webbed; the cold water can be shaken entirely from the

Fre. 241. Pelican. (Photo:
by Sanborn.)

364 PRACTICAL ZOOLOGY

feathers; and a layer of fat just beneath the skin serves to
keep in bodily heat. They feed on fishes and other marine
animals. On shore they stand erect, side by side. They nest
in colonies, laying one or two eggs either among the rocks or
in a burrow.

Water Birds. —It is convenient to divide the seventeen
orders of Northern American birds into two groups — water
birds and land birds. Water birds are those that live near

Fic. 242. — Great blue heron spreading its wing. (Photo. by Hegner.)

ponds and streams or on the seacoast. Most of them spend
much of their time swimming about on the surface or wading
near shore. Their food consists of water plants, insects, worms,
and other small animals captured in the water or extracted
from the muddy bottom.

Divinc Birps.— The grebes and loons are called diving
birds because of their ability to swim under water. Usually
these birds are awkward on land since their bodies are built
for swimming and their feet are webbed.

SOME COMMON BIRDS OF NORTH AMERICA 365

LoNG-WINGED SwimmMers.— The gulls and terns spend a
large part of their time in the air and possess long wings. They
live near bodies of fresh water, or more often on the seacoast
or on islands.

TUBE-NOSED SwiMMERS.— These are marine birds with
tubular external nostrils, fully webbed toes, and long, narrow

Fic. 243. — Nest and eggs of ruffed grouse among the leaves under
a log in the woods. (Photo. by Hegner.)

wings. They are strong fliers, gregarious, and come to land
rarely except to lay their eggs. The wandering albatross and
stormy petrels are well-known examples.

PELICANS AND CorMoRANTS. — These birds have long legs,
long, slender necks, elongated bills, and feet fitted for wading or
swimming. ;

366 PRACTICAL ZOOLOGY

The pelicans (Fig. 241) possess a huge membranous pouch
between the branches of the lower jaw, with which they scoop
up small fish. The common cormorant, or shag, occurs on the
Atlantic coast of Europe and North America and breeds on the
rocky shores of Labrador and Newfoundland. In China and
a few other countries cormorants are trained to catch fish and
are of considerable value to their owners.

Ducks, GEESE, AND Swans. — Every one is familiar with
these birds, but very few have ever seen their nests, since they

Fic. 244.— Bald eagle. (Photo. Fic. 245. — Screech owl at entrance
by Hegner.) to nest cavity in an oak tree. (Photo.
by Hegner.)

are built principally among vegetation in marshy places where
people seldom disturb them. The most beautiful of all our
ducks is the woud duck. This bird which ranges over the
entire United States prefers to live near small streams, lakes,
and ponds. Its eggs, from six to fifteen in number, are laid in
cavities in the trunks or limbs of trees. The wood duck is one of
our game birds that is decreasing so rapidly in numbers that it
seems on the verge of extinction, and drastic action must be
taken by the federal and state governments if this species is not
to vanish entirely.

Herons AND BitrerNs. — The herons and bitterns possess
long legs fitted for wading, broad wings, and short tails.

SOME COMMON BIRDS OF NORTH AMERICA 367

They are found in the warmer regions of the globe and feed
chiefly on fishes. The great blue heron (Fig. 242) is a large
species occurring in all parts of North America. It is about
four feet long and has an extent of wings of about six feet.
Its large flat nest is built of coarse sticks usually in the
top of a high tree; four to six greenish blue eggs are laid.

FLAMINGOES.— The
flamingoes are gregarious
birds, congregating in
thousands on mud flats,
where they build — their
conical mud nests. They
are rosy vermilion in gen-
eral color. One species
occurs in Florida.

Cranes, RaAILs, AND
Coots. — Cranes are large
birds with long legs and
neck. They live in grassy
plains and marshes. Rails
and coots are also marsh
inhabitants, but much
smaller. The coots are fre-
quently called mud hens,
and sometimes hell-divers,
because of their ability to
dive quickly.

SHoRE Brrps. — Plovers, snipes, and sandpipers are called
shore birds because they frequent the shores of ponds, lakes, and
streams, where they probe the soft mud for the small animals
that constitute their food. The killdeer (Fig. 220) is an inter-
esting species twhose name resembles its loud call note. It
scratches a slight cavity in the ground near a stream or in a
neighboring field and lays four large, dark-spotted eggs. The
young can run about soon after hatching. The eggs, young,

Fic. 246. — Nest and three eggs of the
great horned owl. (Photo. by Hegner.)

368 PRACTICAL ZOOLOGY

Fic. 247. — Belted kingfisher. (Photo. by Hegner.)

and adults are all so much like their surroundings in color that
it is very difficult to see them.

Fic. 248. — Nighthawk sitting on her two eggs which were laid
on a pebbly hillside. (Photo. by Hegner.)

SOME COMMON BIRDS OF NORTH AMERICA = 369

Land Birds. — Birds are more abundant in the vicinity of
ponds and streams than anywhere else, but many of them live
mostly on land, going to water
only when thirsty. These may
be called land birds.

GaME Brirps.— The grouse,
bobwhites, pheasants, and tur-
keys are the true game birds.
a cae birds are, as a rule, Fic. ae swift sitting
terrestrial, but many of them on nest which was attached to the
roost or feed in trees. Their inside of a chimney twenty feet from

the top. (Photo. by Hegner.)

nests are usually made on the
ground in grass or leaves, and generally a large number of
eggs, from six to eighteen, is laid (Fig. 243). The members of
one family often remain together as a “ covey,” and in some
species the coveys unite to form large flocks. The wild turkey

is the largest American
m| game bird.

PIGEONS AND DOVES.
— The mourning dove
is a common North
American species often
mistaken for the pas-
senger pigeon which is
now extinct. It makes
a flimsy nest of a few
twigs and lays two
whiteeggs. Theyoung
are naked when born, and are fed by regurgitation.

Brrps oF Prey. — Vultures, falcons, eagles, hawks, kites,
and owls are called birds of prey because of their habit of prey-
ing upon small birds and other animals.

The vultures live on carrion, and in warm countries are valu-
able as scavengers. The California vulture or condor is one of
the largest of all flying birds.

2B

L =|
Fic. 250. — Chimney swift clinging beside her
nest downinachimney. (Photo. by Hegner.)

370 PRACTICAL ZOOLOGY

Fic. 251. — Three young chimney swifts in their nest. (Photo. by Hegner.)

The falcons, hawks, eagles, and kites vary in size from the
little sparrow hawk to the large bald eagle, our national bird
(Fig. 244). Some of them are injurious because they rob the
henyard and destroy other birds, but most of them are decidedly

Fic. 252. — Nests of a colony of cliff swallows built on the side of a cliff near
ariver. (Photo. by Hegner.)

SOME COMMON BIRDS OF NORTH AMERICA 371

beneficial because they destroy mice, rabbits, and other ob-
noxious animals.

The owls are the nocturnal birds of prey. They possess
large rounded heads, strong legs, feet armed with sharp claws,
strong hooked bills, large eyes directed forward and surrounded
by a radiating disk of feathers, and soft, fluffy plumage which
renders them noiseless during flight (Fig. 245). Owls feed upon
insects, mice, rats, and other small mammals, birds, and fish.
The indigestible parts
of the food are cast
out of the mouth in
the form of pellets.
Most species are bene-
ficial to man.

The great horned owl
is one of the largest
North American spe-
cies. It nests in old
squirrels’ and hawks’
nests, in hollow trees,

or in crevices in rocky Fic. 253. — Cliff swallows building their nests
cliffs. Two or three underneath the eaves of a barn. (Photo. by
a Hegner.)

large white eggs are

laid (Fig. 246). Its food consists principally of birds and
mammals, especially rabbits, and its harmful and_ beneficial
qualities are about equal.

Parrots. — Only one species of parrot, the Carolina paroquet,
occurs in the United States. Parrots and paroquets live in
forests and feed on fruits and seeds. They have shrill voices,
and can, with few exceptions, be taught to talk. The African
parrot learns to talk most readily.

Cuckoos AND KINGFISHERS. — The majority of cuckoos do
not build a nest, but lay their eggs in the nests of other birds.
This is not true, however, of the North American species. The
black-billed and yellow-billed cuckoos of this country are long,

372 PRACTICAL ZOOLOGY

slender birds of solitary habits and with peculiar vocal powers
which have given them their common name. The belted king-
fisher (Fig. 247) lays its five to eight white eggs at the end of a
horizontal hole about six feet deep dug by the birds usually in
the bank of a stream. The kingfisher captures small fish by
hovering over a stream and then plunging into the water and
securing the unsuspecting
prey in its bill.

WOODPECKERS. —
About fifty species of
woodpeckers occur in
North America. The
downy (Fig. 227), hairy,
and red-headed wood-
peckers, the flicker, and
the yellow-bellied sap-
sucker are the best known.
Woodpeckers use their
chisel-shaped bills for ex-
cavating holes in trees,
at the bottom of which
their eggs are laid, or for

Fic. 254. — Phebe building a nest above digging out grubs from
the window on the front porch of a house. beneath the bark. Most
(Photo. by Hegner.)

of them are of great bene-
fit because of the insects they destroy, but the yellow-bellied
sapsucker is harmful, since it eats the cambium of trees and
sucks sap.

NIGHTHAWKS, WHIPFOORWILLS, SWIFTS, AND HUMMING
Brrps. — The whippoorwill inhabits the woods and thickets
of eastern North America. It is most active after sundown and
early in the morning, when it captures its insect food on the wing.
The two eggs are laid on the leaves in the woods (Fig. 221).

The nighthawk (Fig. 248) has a range similar to that of the
whippoorwill. During the day it perches on a limb, fence

#4

SOME COMMON BIRDS OF NORTH AMERICA 373

post, or on the ground, but in the evening it mounts into the
air after its insect prey. The two eggs are laid on the bare
ground, usually on a hillside or in an open field; often they are
deposited on the gravel roofs of city buildings.

Fic. 255. — A family of bluebirds. Three qf the young are on the stick
near the father bird. The mother bird is on top of the fence post. (Photo.
by Hegner.)

The humming birds, which are confined to the New World,
have been appropriately called feathered gems, or, according
to Audubon, “ glittering fragments of the rainbow.” Only one
species, the ruby-throated humming bird, is found east of the
Mississippi River. This beautiful little bird is only three and
three-quarters inches in length. It hovers before flowers, from
which it obtains nectar, small insects, and spiders. The nest,
which is saddled on the limb of a tree, is made of plant down and

374 PRACTICAL ZOOLOGY

so covered with lichens as to resemble its surroundings very
closely. Two tiny eggs are laid (Fig. 234). The young are fed
by regurgitation.

The chimney swift breeds commonly in eastern North America.
This species formerly made its nest in hollow trees, but now usu-
ally frequents chimneys. When in the open air, it is always on
the wing, catching insects or gathering twigs from the dead
branches of trees for its nest. The twigs are glued together with

SM ANG

Fic. 256. — Vesper sparrow on nest in a field. (Photo. by Hegner.)

saliva and firmly fastened to the inside of the chimney, forming
a cup-shaped nest (Figs. 249, 250, 251). Certain species of
Chinese swifts make nests entirely of a secretion from the sal-
ivary glands, producing the birds’ nests eaten for food in China.

Prercuinc Birps. — Over one half of the twelve thousand
species of birds belong to this group. They are divided into
sixty-four families, twenty-five of which have representatives
in this country. It is impossible to give an adequate account of
them here because of lack of space, so the student is urged to
refer to books devoted especially to birds. Some of the common

SOME COMMON BIRDS OF NORTH AMERICA 375

birds belonging to the order of perching birds are the flycatchers,
larks, crows and jays, blackbirds and orioles,, sparrows, swallows,
warblers, wrens, thrushes, and bluebirds. The accompanying
photographs illustrate phases of the home life of some of these
birds (Figs. 252-256).
REFERENCES
Handbook of Birds of Eastern North America, by F. M. Chapman. —
D. Appleton and Co., N. Y. City.

Bird-Craft, by M. O. Wright. — The Macmillan Co., N. Y. City.
(See also end of Chapter XXXIV.)

CHAPTER XXXVI

THE RELATIONS OF BIRDS TO MAN

Birps are principally beneficial to mankind. They are things
of beauty and add happiness to our lives by their songs. They
are largely responsible for the destruction of insect pests and
other obnoxious animals, and they destroy countless numbers
of weed seeds. The value of domesticated birds as producers
of meat, eggs, and feathers is estimated in millions of dollars.

Commercial Value. — With the exception of the domesticated
species, birds are now of very little commercial value. In some
localities they are persecuted to a considerable extent for their
eggs, which are used as food. This is true of certain gulls,
terns, herons, murres, ducks, and albatrosses. Egging is not
carried on now as much as formerly, since many of the col-
onies of birds have been driven away from their breeding places,
or the government has prohibited the practice. In 1854 more
than five hundred thousand murres’ eggs were collected on the
Farallone Islands and sold in the markets of San Francisco in
two months.

Game birds have been and still are in certain localities a
common article of food. Most of them, however, have been
so persistently hunted by sportsmen and market men that they
are now of no great commercial importance. Several species,
like the wood duck and heath hen, have been brought to the
verge of extinction. The repeating shotgun, introduction of
cold-storage methods, and easy transportation facilities soon
depleted the vast flocks of prairie chickens and other game
birds of the Middle West. One New York dealer in 1864 re-
ceived twenty tons of these birds in one consignment. The

370

THE RELATIONS OF BIRDS TO MAN 377

hunting and transportation of game birds is now regulated by
law in most localities.

The use of birds’ skins and feathers as ornaments has been for
many years a source of income for many hunters, middlemen,
and milliners. Laws and public sentiment are slowly overcom-
ing the barbarous custom of killing birds for their plumes,
and it is hoped that the women of the country will soon cease
to demand hats trimmed with the remains of birds.

Ostriches are now commonly reared for their feathers, and there
is no more objection to the use of their plumes for ornament
than there is to the use of hens’
‘eggs for food. Ostrich feathers
are now procured almost entirely
from domesticated birds (Fig.
257). In 1904 there were in
South Africa over three hundred
and fifty thousand tame os-
triches which yielded an annual
income of about $18 each.
Ostrich farming is now success-
fully carried on in California,
Arizona, Arkansas, North Caro-
lina, and Florida. The feathers
are clipped without pain to the
birds; those from a single adult
weigh about one pound. Os-
triches in the natural state live
in desert regions and _ travel
about in groups, usually of from
four to twenty. They are very
suspicious and flee from any signs of danger. Their speed is
remarkable, reaching sixty miles an hour, and their single stride
may measure more than twenty-five feet.

The Value of Birds as Destroyers of Injurious Animals. —
Within the past two decades detailed investigations have been

Fic. 257. — Ostrich. (From Evans.)

378 PRACTICAL ZOOLOGY

carried on by the United States Department of Agriculture,
state governments, and private parties in order to learn the
relations of birds to man with regard to the destruction of in-
jurious animals. The results of these researches may be found
in government publications or in books such as Weed and Dear-
born’s Birds in their Relation to Man, and Forbush’s Useful
Birds and their Protection.

NESTLING ADULT.
Fic. 258. — Food of nestling house Fic. 259. — Food of adult house wren.
wren. (U. S. Dept. of Agric.)

A very large proportion of the food of birds consists of insects.
Figures 258 and 259 show diagrammatically the food of nestling
and adult house wrens, birds that are very common about gar-
dens. Practically all of the insects devoured by birds are
injurious to plants or animals and consequently harmful to
man.

Another large element in the food of birds consists of small
mammals, such as field mice, ground squirrels, and rabbits.
For many years hawks, owls, and other birds of prey have been
killed whenever possible, because they were supposed to be in-
jurious on account of the poultry and game birds they captured.
Careful investigations have shown, however, that at least six
species are entirely beneficial; that the majority (over thirty

THE RELATIONS OF BIRDS TO MAN 379

species) are chiefly beneficial; that seven species are as bene-
ficial as they are harmful; and that only the gyrfalcons, duck
hawk, sharp-shinned hawk, Cooper’s hawk, and goshawk are
harmful.

As examples of beneficial birds of prey may be mentioned (1)
the rough-leg hawk, which feeds almost entirely on meadow mice
during its six months’ sojourn in the United States, (2) the red-
tailed hawk, or “ hen hawk,” sixty-six per cent of whose food
consists of injurious mammals and only seven per cent of poul-
try, and (3) the golden eagle, which is highly beneficial in cer-
tain localities because of the noxious rodents it destroys. The
Cooper’s hawk is the real ‘“‘ chicken hawk ’’; its food is made up
largely of poultry, pigeons, and wild birds, but it also includes
the harmful English sparrows.

The beneficial qualities of birds are well shown by Dr. S. D.
Judd from a seven years’ study of conditions on a small farm
near Marshall Hall, Maryland. Modern methods of investi-
gation led Dr. Judd to the following conclusions : —

“At Marshall Hall the English sparrow, the sharp-shinned,
and Cooper hawks, and the great horned owl are, as everywhere,
inimical to the farmers’ interests and should be killed at every
opportunity. The sapsucker punctures orchard trees exten-
sively and should be shot. The study of the crow is unfavorable
in results so far as these particular farms are concerned, partly
because of special conditions. Its work in removing carrion
and destroying insects is serviceable, but it does damage to game,
poultry, fruit, and grain that more than counterbalances this
good, and it should be reduced innumbers. The crow blackbird
appears to be purely beneficial to these farms during the breeding
season and feeds extensively on weed seed during migration,
but at the latter time it is very injurious to grain. More de-
tailed observations are necessary to determine its proper status
at Marshall Hall.

“The remaining species probably do more good than harm,
and except under unusual conditions should receive encourage-

380 PRACTICAL ZOOLOGY

ment by the owners of the farms. Certain species, such as
flycatchers, swallows, and warblers, prey to some extent upon
useful parasitic insects, but, on the whole, the habits of the in-
sectivorous birds are productive of considerable good. Together
with the vireos, cuckoos, and woodpeckers (exclusive of the sap-
suckers), they are the most valuable conservators of foliage on
the farms. The quail, meadow lark, orchard oriole, mocking
bird, house wren, grasshopper sparrow, and chipping sparrow
feed on insects of the cultivated fields, particularly during the
breeding season, when the nestlings of practically all species eat
enormous numbers of caterpillars and grasshoppers.

““The most evident service is the wholesale destruction of
weed seed. Even if birds were useful in no other way, their
preservation would still be desirable, since in destroying large
quantities of weed seed they array themselves on the side of the
Marshall Hall farmer against invaders that dispute with him,
inch by inch, the possession of his fields. The most active weed
destroyers are the quail, dove, cowbird, red-winged blackbird,
meadow lark, and a dozen species of native sparrows. The
utility of these species in destroying weed seed is probably at
least as great wherever the birds may be found as investigation
has shown it to be at Marshall Hall.”

Domesticated Birds. — Birds have for many centuries been
under the control of man, and have produced for him hundreds of
millions of dollars’ worth of food and feathers every year. The
common hen was probably derived from the red jungle fowl of
northeastern and central India. The varieties of chickens that
have been derived from this species are almost infinite.

The domestic pigeons are descendants of the wild, blue-rock
pigeon which ranges from Europe through the Mediterranean
countries to central Asia and China. Breeders have produced
over a score of varieties from this ancestral species, such as
carriers, pouters, fantails, and tumblers. Young pigeons,
called squabs, constitute a valuable article of food.

Of less importance are the geese, ducks, turkeys, peacocks,

THE RELATIONS OF BIRDS TO MAN 381

swans, and guinea fowls. The geese are supposed to be derived
from the graylag goose, which at the present time nests in the
northern British Islands. Most of our domestic breeds of ducks
have sprung from the mallard. This beautiful bird inhabits
both North America and temperate Europe and Asia. The
common peacock of the Indian peninsula, Ceylon, and Assam
has been domesticated at least from the time of Solomon. It
has been distributed by man over most of the world. The swan
is, like the peacock, used now chiefly as an ornament. The
mute swan of Central Europe and Central Asia is the common
domesticated species. The guinea fowl is a native of West
Africa. Farmers usually keep a few of them to “ frighten away
the hawks.”

The turkey is a domesticated bird that has been brought under
control within the past four centuries. Our Puritan ancestors
found the wild turkey abundant in New England. It was
introduced into Europe early in the sixteenth century and soon
became a valuable domestic animal. In its wild state, it is now
almost extinct except in some of the remoter localities. Our
domestic turkeys are descendants of the Mexican wild turkey.

REFERENCES

Birds in their Relation to Man, by C. M. Weed and N. Dearborn. — J. B.
Lippincott Co., Philadelphia, Penn.

Useful Birds and their Protection, by E. H. Forbush. — Published by the
Massachusetts State Board of Agriculture.

Game Birds, Wild-Fowl and Shore Birds, by E. H. Forbush. — Published
by the Massachusetts State Board of Agriculture.

Bulletins and Circulars published by the Bureau of the Biological Survey,
U. S. Department of Agriculture.

(See also end of Chapters XXXIV and XXXV.)

CHAPTER XX XVII
BIRD PROTECTION!

Ir has been evident for some time that the number of birds
has been rapidly decreasing, and efforts have been made to learn
the cause of this so that protective measures could be under-
taken. The enemies of birds are chiefly man and other animals.

1. THe DestrucTION OF BiRDS

The Destruction of
Birds by Man. — Man
is responsible for the ex-
tinction of many species
of birds or for their dis-
appearance from great
tracts of country. He
cuts down the forest and
drives out the larger
wood birds. He de-
stroys the birds that
injure his crops or flocks.
He introduces animals
which destroy birds,
and he shoots for food,

Fic. 260.— Passenger pigeon. (The bird money, or sport. It is
with the long tail.) (Photo. by Hegner.)

only since civilized man
reached this country that the great auk has become extinct,
and that the passenger pigeon (Fig. 260), which roamed in

1A large part of this chapter is quoted direct from Forbush’s Useful Birds and

their Protection.

382

BIRD PROTECTION 383

countless millions over our continent, has been swept away.
It is since then that the prairie chicken, once found in the east,
and so plentiful in Kentucky that it was considered fit food
for slaves and swine only, has been pushed toward the far West.
The wild turkey has been nearly driven out of the Atlantic
States by man. The white egret and the Carolina parrot have
almost disappeared. The bartramian sandpiper or upland
plover, the wood duck, and the woodcock must follow if not fully
protected. Man exterminates birds for money, little recking
that he is killing the goose that lays the golden egg.

The greatest enemies of game birds, and, therefore, the great-
est factors in their extermination, are the epicures, — the
people who buy birds to eat. The market men merely supply
the existing demand. The call for game birds has been so in-
sistent and the price paid for them so extravagant that the
market men have often organized to defeat legislation for the
protection of game. Observing people who have frequented
the markets have read from the butcher’s stall the story of the
decrease of game birds. Within thirty years, tons of passenger
pigeons have stood in barrels in the Boston market, and men now
living can remember when the eastern markets were glutted
with quail and prairie chickens. The war of extermination
waged on game birds is a blot on the history of American civil-
ization. It is paralleled only by the destruction of birds for
millinery purposes, which has some shockingly cruel aspects.

Here again the dealers — the milliners — are not so much
to blame as the public, for the former cater to the wants of
women only as fashion dictates. Though civilized we still cling
to our rings, beads, and feathers, — the ornaments of the sav-
age. Within thirty-five years the skins of bluebirds, scarlet
tanagers, and Baltimore orioles have been in good demand in
Massachusetts for hat ornaments.

The brutal savagery which is characteristic of this phase of
bird destruction has been well illustrated in the extermination
of the egrets of the United States (Fig. 261). Twenty-five

384 PRACTICAL ZOOLOGY

years ago these beautiful birds were abundant in some Southern
States; stragglers occasionally came north as far as New Eng-
land. They are shy birds during most of the year, feeding
chiefly in deep swamps and along lonely watercourses. In the
breeding season they gather into heronries, commonly called
“ rookeries,”’ where they build their nests. Then much of their
shyness disappears under the stress of providing for and pro-

: tecting their young. Un-
fortunately for them, their
nuptial plumes are perfect
in the breeding season.
Fashion demanded the
plumes. Nesting time was
the plume hunter’s oppor-
tunity. There was little
difficulty, then, in secur-
ing the birds by shooting
them when they were sit-
ting on the nests or hover-
ing over their helpless
young. So the old birds
were shot, the plumes
stripped from their backs,

Pie gor Spear youre: and the young left. to

starve in the nests or to
become the prey of hawks, crows, or vultures.

Visitors in Florida, in 1878, observed great flights of these
birds along the lakes and rivers of the southern counties.
One heronry was estimated to contain three million birds. Ten
years later they were rare everywhere, and now they are prac-
tically extirpated. They have been pursued along the coasts
of Mexico and into Central and South America. The search
is extending into all countries where they may be found. Half-
savage Indians and negroes are enlisted in the slaughter, sup-
plied with guns and ammunition, and sent wherever they can

BIRD PROTECTION 385

find the birds. The misery and suffering entailed can be im-
agined. Thus are the “stub” plumes, “ aigrettes,’ and
“ospreys”’ procured. They are not manufactured, and what-
ever their color when sold, they were originally stripped from the
back, head, or neck of some white heron or egret. The absolute
extinction of these plume-bearing species is assured unless women
will stop wearing the plumes.

A similar slaughter took place among the sea birds along the
Atlantic coasts. The birds were shot down on their breeding
grounds and their wings cut off. Many human lives have been
lost by reason of this nefarious business. In 1905 a warden
employed by the National Association of Audubon Societies
to protect the birds was murdered by plume hunters. The
reader will be spared further details of this barbarous trade.

The. number of birds killed in the United States each year
before the business was checked by law and public sentiment
cannot be estimated, but some figures can be given. A single
local taxidermist handled thirty thousand bird skins in one year.
A collector brought back eleven thousand skins from a three
months’ trip. About seventy thousand bird skins were sent
to New York from a small district on Long Island in about four
months. American bird skins were shipped to London and
Paris. We may judge of the demand there for birds from the
fact that from one auction room in London there were sold in
three months over four hundred thousand bird skins from
America and over three hundred and fifty thousand from India.
One New York firm had a contract to supply forty thousand
skins to a Paris firm.

The danger to birds multiples with the increase of population.
Gunners and sportsmen shoot birds mainly to supply the mar-
kets or for recreation; but many persons shoot birds, large or
small, merely for sport or practice. Certain kinds of foreigners
‘shoot small birds for sport, and eat, them. These people go
out in squads, and each man shoots at every bird within range,

whether sitting or flying.
2c

386 PRACTICAL ZOOLOGY

Boys with shotguns, air rifles, and various destructive weapons,
shoot at anything that offers a fair mark. The improve-
ment in firearms and the reduction in their price go hand in
hand with the constant increase in the number of people able
to bear arms, the augmentation of the number of crack shots,
and the accession to the number of dogs trained to hunt birds.

Snares are still much used, even where forbidden by law.
Children, especially boys, destroy the nests and eggs of birds,
thus constituting a considerable check on bird increase. The
mania for collecting birds’ eggs is widespread. Some boys use
the nests of birds for targets and their eggs for missiles in the
same spirit in which the same young savages murder the toads
about a pond.

There are many indirect ways in which man reduces the num-
bers of birds. Marshes are drained, and the sustenance of
marsh birds destroyed. Reservoirs are made, and the haunts
of land birds overflowed. The building of dams for manufac-
turing purposes
holds back the
waters of rivers,
so that heavy
rainfalls in the
breeding season
flood the nests of
many marsh
birds, destroying
eggs and young.
Thus rails, bit-
terns, and marsh

wrens are
Fic. 262, — Woodcock on nest. (Photo. by Hegner.) drowned or driven

away. Thou-
sands of birds and their nests are burned by fires in the woods.
Swifts are sometimes suffocated in numbers by coal fires built
in nesting time. Lighthouses and electric light towers are ob-

BIRD PROTECTION 387

stacles on which many birds are dashed to death in their noc-
turnal migrations. Telegraph, electric light, trolley car, and
telephone wires are all deadly and their number is constantly
increasing. Thousands of woodcocks (Fig. 262) and many
other birds are killed by flying against them. Wire fences are
nearly as fatal to grouse and other low-flying birds.

Last but perhaps not least among the causes which decrease the
number of birds about the centers of population there must be
enumerated the clearing up of underbrush, shrubbery, vines, and
thickets. Many birds of the tangle are driven out when this
cover is destroyed and replaced by well-kept lawns and fields.

Fic. 263. — Cat with bird in its mouth. (After Forbush.)

Cats. — We have already introduced into this country a
terrible scourge to birds, — the domestic cat (Fig. 263). The
statement that the mature cat in good hunting ground kills,
on the average, fifty birds a year, is certainly within bounds.
Kittens and half-grown cats do not catch many birds, but the
old cat that wanders off into the fields and woods is terribly
destructive. John Burroughs says that cats probably destroy
more birds than all other animals combined.

388 PRACTICAL ZOOLOGY

Squirrels. — Some individual squirrels are habitual nest
robbers. This includes all species, but the red squirrel is the
worst culprit. Where squirrels have the nest-robbing habit,
they may do more harm among birds than any other mammal
except the cat. They are active, can climb to almost any bird’s
nest, and can defend themselves when attacked by the parent
birds. Red squirrels and gray squirrels will rob nests either on
the ground or in trees, taking eggs or young as they find them.
The chipmunk usually molests only those nests that are on or
near the ground.

Rats and Mice. — Rats and mice kill some birds. Probably
the tree-climbing, white-footed or deer mouse is one of the great-
est enemies that birds have among these smaller mammals,
but under natural conditions it is held in check by owls.

Hawks. — A very few species of hawks are probably the most
destructive native natural enemies of birds. All other hawks
kill comparatively few. The sparrow hawk, a great insect killer,
kills fewer birds than the others, and is regarded as a friend to
the farmer; but there are three species of pernicious hawks:
the American goshawk, the Cooper’s hawk, and the sharp-
shinned hawk. The goshawk is an uncommon or periodical
winter visitant, but the other two are fairly common, and in-
dividually are probably the most destructive of all the natural
enemies of birds. They are slaty or bluish above, with rather
short, rounded wings, and long tails. When flying at any
height, they progress by alternate periods of flapping and soar-
ing. They may be known by their shape and by their manner
of flight.

Owls. — All the owls kill birds, but most species kill but few.
They live mainly on mammals, particularly rodents like mice,
rabbits, and hares, on the increase of which they constitute an
effectual check.

Crows and Jays. — The crows, jays, and magpies have ac-
quired a world-wide reputation as nest robbers. The common
crow and the blue jay manage to live up to their reputation.

BIRD PROTECTION 389

The American crow is a most deadly enemy to birds from the
size of the chipping sparrow to that of the night heron, ruffed
grouse, and the black duck, for it continually steals the eggs
and young of such birds and poultry.

The well-known blue jay is destructive to the eggs of the
smaller birds, whose nests it robs systematically, and it has
frequently been seen to kill the young. The robin and other
larger birds will drive the jay away from their nests, but it
often succeeds in robbing them by stealth. Vireos, warblers,
and sparrows it regards very little, and plunders their nests
without noticing their agonized cries.

These birds, on the other hand, possess many useful traits.
Crows are valuable as grasshopper killers, and they are de-
structive to the gypsy moth. Jays eat the eggs of the tent-
caterpillar moth and the larve of the gypsy moth and other
hairy caterpillars.

The English Sparrow. — The house or “ English ” sparrow
is the only one of the smaller birds that has repeatedly been
seen to destroy the nests of other birds, break their eggs, kill
their young, mob them, and drive them away from their homes.
It occupies the houses of bluebirds, martins, swallows, and
wrens, and the nests of barn swallows, cliff swallows, and bank
swallows, and by persistency and force of numbers drives the
owners away.

Snakes. — All the common snakes, except, perhaps, the little
green snake, eat birds and eggs. Birds exhibit great dread of
snakes, but the brown thrasher or the catbird will attack them
bravely in defense of their young. Some birds seem to be in-
capacitated by terror when a snake appears at the nest, and
are rendered incapable of any effectual defense. The common
black snake is the greatest enemy the birds have among native
snakes, for it climbs trees with the greatest ease, and is so
swift that it is able to catch young birds when they first leave
the nest and sometimes it strikes down an anxious parent.

390 PRACTICAL ZOOLOGY

2. THE PROTECTION OF BIRDS

Protection from Natural Enemies. — In Part 1 of this chapter
we have considered the enemies of birds. One method of pro-
tecting birds is to destroy their natural enemies whenever pos-
sible. It is rather difficult to decide whether certain bird ene-
mies should be killed or not, but there can be no doubt as to the
destruction of cats and English sparrows. Other enemies, like
Cooper’s hawks and sharp-shinned hawks, should be killed on
sight. Many animals, such as squirrels, crows, and jays, which
rob birds’ nests or kill the young, should not be exterminated,
but their numbers should be reduced.

Protection from Man. — The first and most important step
in protecting birds from their human enemies is to create a
public sentiment in favor of birds, by teaching their value and
the necessity for conserving them. But many people cannot be
taught these things and must be prevented by law from destroy-
ing birds. The Biological Survey of the United States Depart-
ment of Agriculture has published and is constantly distributing
many reports on the food habits and utility of birds. The
Audubon societies and the National Association of Audubon
Societies send out illustrated leaflets concerning birds to teachers
and others, and is directly interested in getting legislatures to
pass proper laws for the protection of birds. Many other so-
cieties such as those for the Prevention of Cruelty to Animals,
the American Rescue League, the League of American Sports-
men, and the Agassiz Associations also lend their influence in
the same direction.

Many laws have been passed protecting song birds, and others
are on the statute books protecting game birds during certain
seasons or fora period of years. Besides this, tracts of land have
been purchased in various parts of the country for the purpose
of providing a refuge for birds and other animals. Reservations
of this sort should be maintained in every state in the Union if
we wish tosave our wild animals from extinction (see Chap. XLI).

BIRD PROTECTION 391

3. METHODS oF ATTRACTING BrrDs

It is usually an easy matter to attract wild birds to the vicinity
of one’s home. First of all, birds need food before they can

il

Z,
Whit
as Age
Bigs
4

Bayberry.

Greenbrier.

Fic. 264. — Plants that attract birds. (After Forbush.) |

carry on any of their nesting activities. The food of birds con-
sists largely of insects, seeds, and berries. Insects are present
almost everywhere and, as a rule, seeds are abundant; conse-

392 PRACTICAL ZOOLOGY

quently, trees or shrubs that bear berries eaten by birds should
be planted (Fig. 264). Among these may be mentioned the
mountain ash, sumac, raspberries, elder, virginia creeper, mul-
berry, barberry, cherry, dogwood, and red cedar.

In winter the permanent residents or winter visitors sometimes
have difficulty in finding enough food to keep them warm and
will welcome any help from human friends. Grain scattered

Fic. 265. — A bird bath. (Photo. by Hegner.)

about on the snow will attract tree sparrows, juncos, and others.
Pieces of pork rind or of suet tied to a limb of a tree will tempt
the appetites of woodpeckers, nuthatches, and chickadees.

Water is needed by birds both to drink and for bathing, of
which they are very fond. This is especially true during the
hotter days of summer. If there is a water tap on the lawn, a
very good bird bath can be constructed by making an inden-
tation a few inches deep and three feet long and lining this with
round stones set in clay (Fig. 265). In such a place as this
many different kinds of birds make their toilets on warm summer
days.

BIRD PROTECTION 393

Bird Houses. — Many birds make their homes in hollows in
trees, fence posts, and similar places. Where no nesting sites
of this kind occur, houses should be made and put up to attract
those birds that otherwise would seek homes elsewhere.

Bird houses should be made of rough, weathered lumber and
should not be painted. They may be covered with bark, but
care must be taken to have the bark tightly fastened to the
boards, or it will furnish excellent homes for insect pests. Lum-

Fic. 266. — Clay bird houses. (Photo. by Hegner.)

ber with the bark left on is extremely useful and makes houses
of the best type.

A section of the hollow limb of a tree makes a home most
nearly like that which the bird naturally uses. This section
should be plugged at both ends and an entrance made in the side.
When a hollow limb is not obtainable, a limb may be bored out.
Where pottery is taught, excellent houses of clay may be made
which will serve admirably for wrens (Fig. 266).

The position of the house is important and should be con-
sidered for each bird. The boxes must be well fastened in a
sheltered position, shielded both from the sun and from too close
observation. The natural enemies must also be considered,

394 PRACTICAL ZOOLOGY

and plans must be made to keep the cats, sparrows, and jays
from disturbing the nests. If the house is in a tree or on a
post, a little barbed wire coiled around the post about five feet
below it will protect it from cats; jays and sparrows cannot get
at the nest if there is no perch.

Fic. 267.— House wren carrying a stick into a nesting box.
(Photo. by Hegner.)

The wren, although a very small bird, can usé a relatively
large house (Fig. 267). It should be about 8 & 6 X 6 inches
inside. Near the top of one end an opening 14 inches in diam-
eter should be made for the entrance. A perch is not necessary,
and is better left off, as it allows the English sparrows and other
depredators to get at the contents (Fig. 268). The house
should be placed in a tree or on the side of a building 7 to 15 feet
from the ground. It is safest when nailed to a building where
it is out of reach of cats.

The little black-capped chickadce is almost exactly the size of
the wren, but uses a smaller house. A box 3 X 3 X 7 inches

BIRD PROTECTION

inside, with an entrance
1% inches in diameter on
one side near the top,
makes a very acceptable
chickadee home. This
house should be placed
with its long diameter
perpendicular to the earth,
in a tree or against a
building, about 10 feet

from the ground.

ae : : Fic. 268. — Nest of house wren in nest-
The chickadee in its ing box shown in Fig. 267. (Photo. by

natural haunts rears its Hegner.)

young in the hollow of a tree. The nest is made of soft moss,
a few feathers, and the hairs of different animals. From six
to ten eggs are laid — pure white with a reddish tint, and

Fic. 269. — Bluebird with a grasshopper for its
young. (Photo. by Hegner.)

spotted with red-
dish brown at the
larger end.
Chickadees are
with us the entire
year. Their nests
are built about the
first of May, and
two broods may be
reared in a season.
The bluebird is
larger than the
chickadee and wren,
and needs a larger
home. Its house
should be 10 X6
x 6 inches inside.
The entrance is in
one end, from 2 to

396 PRACTICAL ZOOLOGY

2% inches in diameter. Place the house in a position similar to
that of the wren. The top of a post is a favorable site.

The bluebird’s natural nesting place is a hollow in a stump,
fence post, or tree (Fig. 269). It often makes use of a tin can
lodged in a fence corner, and is partial to the old deserted nest
holes of woodpeckers. The nest consists of soft grasses. Five
light blue eggs are
usually laid, and two
or three broods are
reared during the
nesting season.

Bluebirds may be
looked for about the
last of March. They
mate about the last
week in April. Bird
houses for them should
therefore be in place
by the end of March.
Care must be taken
to protect the blue-
birds from the Eng-
lish sparrows, which

Fic. 270. — Screech owl. (Photo. by Hegner.)

are ever ready to drive out the real owners and appropriate
the house.

Unlike the other birds mentioned in this article, the martin
is sociable and seems to enjoy the company of its fellows. Its
house may be built with compartments which will allow several
pairs to occupy it at the same time. The compartments should
be about 9 X 7 X 7 inches inside. The entrances should be 23
inches in diameter, near the top of the compartments. Many
elaborate and beautiful houses are possible, as the martins are
not afraid of homes constructed by human beings. The house
should be placed on top of a building or on a tall post.

Suitable nesting places for the screech owl (Fig. 270) are not

BIRD PROTECTION 397

common, and a bird house, if carefully made, may attract a
tenant. It should be 16 X 8 X 8 inches inside, and may have
the top left open for an entrance or a hole 4 inches in diameter
in one side near the top. Screech owls do not build nests, but
lay their eggs on the rubbish found at the bottom of holes in
trees. It would therefore be well to line the house with leaves
to tempt any visitors to remain. The sides of the house should
be covered with bark to make it resemble the tree in which it is
placed.

REFERENCES
See end of Chapters XXXIV-XXKVI.

CHAPTER XXXVIII

THE STRUCTURE AND ACTIVITIES OF MAMMALS

AMMALS are popularly known a imals ”’ or beasts.
M S popularly k s “animals” beast

We are all familiar with the domesticated species such as the
dog, cat, horse, cow, etc. and with many of the wild forms. The
term mammals was applied to the group because the young,
which are born in a very immature condition, are fed with milk
from the mammary glands of the mother. There are about
7500 species of living mammals, but only a small proportion
of these occur in this country. Mammals range in size from
the mouse at one extreme to the whale at the other extreme.
Among the simpler species are the egg-laying mammals of Aus-
tralia and the opossum and kangaroo which carry their young
about with them in a pouch. Other well-known species are
the moles, shrews, bats, dogs, cats, seals, rabbits, rats, ant
eaters, armadillos, camels, deer, horses, elephants, whales,
monkeys, apes, and man.

Habitats. — There is great diversity among the members of
the phylum Mammalia, due chiefly to their various modes of
life. Most of them live on the ground, but many are aquatic,
others arboreal, and a few aérial in habit. The whales, dolphins,
seals, walruses, and sea cows are aquatic, living almost without
exception In the sea. They are not aquatic in the same sense
that fish are, however, since they cannot take oxygen from the
water, but must come to the surface to breathe.

Among the arboreal mammals are the monkeys, squirrels,
and sloths. Some of the squirrels can even “fly” through
the air for short distances, but as in the case of the flying
dragon flight here is really only sailing through the air on

398

THE STRUCTURE

outstretched mem-
branes. The bats,
however, possess
wings and are as much
air inhabitants as the
birds.

A few species, like
the mole, pass almost
their entire existence
underground, and the
ground squirrels,
woodchucks, prairie
dogs, and similar spe-
cies live part of the
time in burrows.

Protection. —Mam-
mals, like birds, are
warm-blooded animals
and must be protected
not only from their
natural enemies and
from the ordinary
hard knocks of life,
but also from weather
conditions, such as
extreme cold, which
would not injure such
cold-blooded creatures
as the frog and turtle.
Heat is kept in the
body in various ways.
Mammals that live in
cold water, like the
whale, possess a very
thick layer of fat, the

AND ACTIVITIES OF MAMMALS 399

M

R= —
0 a
GH.

Tic. 271. — Longitudinal section through a hair
in its follicle.

Ap, muscle; Co, dermis; F,F’, fibrous layers

of follicle; Ft, fat; GH, membrane; HBD, se-

baceous gland; HP, hair papilla; M, pith; O,

cuticle; R, cortical layer; Sc, horny layer of
epidermis; Sch, hair shaft; SM, epidermis;
WS, WS’, layers of root-sheath. (From Wie-

dersheim.)

400 PRACTICAL ZOOLOGY

blubber, just beneath the skin, which prevents the escape of the
body heat. The more usual method of protection from the cold
is a thick covering of hair.

Hair. — All mammals possess hairs and may be distinguished
from all other animals by these peculiar structures. The hairs
project out from pits in the skin, called hair follicles (Fig. 271).
The hair shaft (Sch) broadens at the base, extending around
a highly vascular papilla (HP) at the bottom of the pit. When
hairs are shed, new hairs usually arise to take their place.
Secretions from the sabaceous glands (HBD) keep the hairs
glossy.

The two main types of hairs are (1) contour hairs which are
long and strong and (2) woolly hairs which are shorter and
constitute the under fur. In some animals the woolly hairs
have a rough surface, as in the sheep, which causes them to co-
here and gives them their felting quality. Certain of the
stronger hairs may be moved by muscular fibers (Fig. 271, Af),
which are responsible for the erection of spines or the gristling
of the other hairs.

The air spaces between the hairs prevent the escape of heat
Since air is a bad conductor of heat. Besides protecting the
body from loss of heat the hairy covering also prevents to a
large extent injury due to blows. Human beings are almost
entirely covered by hair, except on the soles of the feet and palms
of the hands. This covering is of practically no service except
the thick growth on the head.

Color. — As a rule mammals are not very highly colored, but
many of them are characterized by stripes, as in the zebra and
tiger, or spots, as in the leopard. The dull colors of mammals
and the stripes or spots are all supposed to aid in concealing the
animals amid their surrounding and thus to protect them
from their enemies. Animals like the Arctic fox that live in the
colder regions of the earth change color in the winter, becoming
white. This change is of advantage, since it renders them in-
conspicuous against the background of snow.

THE STRUCTURE AND ACTIVITIES OF MAMMALS 401

Claws, Nails, Hoofs, and Horns. — Mammals protect them-
selves from their enemies when in actual combat by means of
their teeth, claws, nails, horns, and hoofs. The claws, nails,
and hoofs are all modifications of the horny covering on the
upper surface at the end of the digits (Fig. 272). The foot may
rest partially or entirely on these structures, as in the case of the

a
!

Fic. 272. — Diagrammatic longitudinal sections through the distal ends of
the digits of mammals.

A, spiny anteater; B, dog; C, man; D, horse.
1-3, phalanges; b, torus; N, nail plate; S, sole horn; W, bed of claw or
nail. (From Wiedersheim.)

horse, but, as a rule, it is partly supported on the pads just be-
neath them. The horns of the rhinoceros and the horn sheaths
of cattle are, like claws and hoofs, formed from the outer layer
of the skin, the epidermis, but in many other animals the horns
are of bone, and even in cattle the central core of the horn is
bone. Some animals, like the deer and prong-horned antelope,
shed their horns annually and a new set gradually grows to take
their place; others, like cattle and sheep, normally keep one
pair of horns throughout life. In many cases only the male

individuals of a species possess horns.
2D

402 PRACTICAL ZOOLOGY

Locomotion. — The habitat of an animal determines to a
large extent its method of locomotion. Whales swim about easily
in the water, but are helpless on land. Seals and walruses are
likewise excellent swimmers, but their flippers and heavy bodies
make locomotion on land very slow and awkward. Most of the

spinal cord spinal column
chest cavity
— diaphragm
abdominal cavity
Fic. 273. — Longitudinal section through the trunk of a human body (side

view). (From Peabody and Hunt.)

mammals walk, run, or hop, but a few of them can sail through
the air for short distances, and the bats can actually fly.
Internal Organs. — The body cavity in which the internal
organs lie is in mammals divided into two parts by a transverse
muscular partition called the diaphragm. The anterior portion

THE STRUCTURE AND ACTIVITIES OF MAMMALS 403

(upper portion in man) contains the heart and lungs. The
posterior cavity is filled with the abdominal viscera (Fig. 273).

Digestion. — The digestive system is similar to that of other
vertebrates in general structure, consisting of an alimentary

nasal cavity #p passage from nose to throat
cavity of mouth

throat cavity

palate

tongue
-opening of windpipe

pylorus

bile duct

transverse colon pancreatic duct

live

opening of bile
and pancreatic ducts

small intestine

Fic. 274. — Parts of the alimentary canalof man. (From Peabody and Hunt.)

canal and the glands connected with it (Fig. 274). The alimen-
tary canal begins with the mouth cavity in which are the
tongue and teeth, then follow in succession the cesophagus,
stomach, small intestine, large intestine, and rectum. The

404

PRACTICAL ZOOLOGY

principal glands are the salivary glands connected with the
mouth, and the liver and pancreas connected with the small

Fic. 275. — Diagrammatic section of various
forms of teeth.

I, incisor or tusk of elephant with pulp cav-
ity open at base; II, human incisor, during de-
velopment, with pulp cavity open at base ; III,
completely formed human incisor, opening of
pulp cavity small; IV, human molar with broad
crown and two roots; V, molar of ox, enamel
deeply folded and depressions filled with cement.

Enamel, black; pulp, white; dentine, hori-
zontal lines; cement, dots. (From Flower and
Lydekker.)

intestine. These glands
secrete digestive juices,
and other smaller glands
in the walls of the
stomach and intestine
share in this duty.

Teeth. —The teeth
of mammals are among
their most interesting
possessions since they
vary so much in the
different species and in-
dicate what kind of
food is eaten by their
owners. Most mam-
mals are provided with
teeth, but the whale-
bone whales, the egg-
laying species, and ant-
eaters are without them
in the adult stage, and
in some forms they have
never been found, even
in the embryo.

The teeth are em-
bedded in sockets in
the bone, and arise from
the mucous membrane
of the mouth. The
principal forms of teeth
and the relations of the
materials composing
them are shown in Fig-

THE STRUCTURE AND ACTIVITIES OF MAMMALS 405

ure 275. The enamel (in black) is the outer hard substance;
the dentine (horizontal lines) constitutes the largest portion of
the tooth; and the cement (dotted) usually covers the part of the
tooth embedded in the tissues of the jaw. The central pulp cav-
ity of the tooth contains nerves, blood vessels, and connective
tissue. Teeth have an open pulp cavity during growth (Fig.
275, II), which in some cases continues throughout life (Fig. 275, I).

The teeth of fishes, reptiles, and amphibians are usually all
similar, but in mammals there are commonly four kinds in each
jaw: (1) the chisel-shaped
incisors in front (Fig. 276,
i 2), (2) the conical canines
(c), (3) the anterior grind-
ing teeth or premolars (pm 1
—pm 4), and (4) the pos-
terior grinding teeth or mo-
lars (m 1).

In most mammals the first
set of teeth, known as the
milk dentition, is pushed Fic. 276. — Teeth of dog.

out by the permanent teeth, i2, second incisor; ¢, canine; pm4,
which last. throughout the 2m Stsiandfeurth premolars: md fs
life of the animals. The
milk molars are followed by the premolars, but the permanent
molars have no predecessors.

The relation of the form of the teeth to the food habits of the
animal may be shown by the following examples. The dol-
phins have a large number of sharp, conical teeth adapted for
capturing fish; the carnivorous animals, like the dog (Fig. 276),
are provided with large canine teeth for capturing and killing
their prey, small and almost useless incisors, and molars with
sharp edges for cutting or crushing; herbivorous mammals,
like the ox, possess broad incisors for biting off plants, no canines,
and large grinding molars; gnawing mammals, like the rabbit,
have incisors that grow throughout life, but are worn down by

406 PRACTICAL ZOOLOGY

gnawing, thereby maintaining a serviceable length and a keen
cutting edge; insect-eating mammals, such as the shrew, seize
insects with their projecting incisors and cut them into pieces
with the pointed cusps on their premolars and molars; and man
and other omnivorous animals are provided with teeth fitted
for masticating both animal and vegetable matter.

Circulation. — The heart in mammals is more highly devel-
oped than in any other vertebrate. The ventricle is divided
into two chambers that are perfectly distinct. The pure blood
(in the pulmonary veins), passing from the lungs, enters the left
auricle, passes thence into the left ventricle, whence it is driven
(through the aorta) over the body. After having traversed
all the parts of the body and become richly loaded with carbonic
acid gas, it returns to the heart, entering the right auricle, and
passing thence into the right ventricle, whence it is pumped
through the pulmonary arteries back into the lungs. Thus by
the division of the heart into two halves the arterial is com-
pletely separated from the venous blood.

The blood corpuscles are unlike those of the lower vertebrates,
being smaller, round instead of oval, biconcave, and without
nuclei. The lymphatic system is of considerable importance
in mammals. The fluid portion of the blood, which, because
of the blood pressure, escapes through the walls of the capil-
laries into the spaces among the tissues, is collected into lymph
vessels. These vessels pass through so-called lymph glands
and finally empty into the large veins in the neck. The lym-
phatics which collect nutriment from the intestine are called
lacteals.

Respiration. — Mammals breathe air by means of lungs.
The trachea or windpipe is held open by incomplete rings of
cartilage ; and the larynx, or voice box, is supported by a num-
ber of cartilages, and across its cavity extend two elastic folds
called the vocal cords.

The lungs are conical in shape, and lie freely in the thoracic
cavity. Air is drawn into them by the enlargement of the

THE STRUCTURE AND ACTIVITIES OF MAMMALS 407

cavity. This is accomplished both by pulling the ribs forward
and then separating them and by means of the diaphragm. The
diaphragm is normally arched forward (up in man, Fig. 273),
and when it contracts, it flattens, thus enlarging the thoracic
cavity. The increased size of this cavity results in the expan-
sion of the lungs, because of the air pressure within them, and
the inspiration of air through the nostrijs. Air is pumped out
of the lungs (expiration) by the contraction of the elastic lung
vesicles and of the thoracic wall and diaphragm.

Excretion. — Waste products are cast out of the body by the
kidneys and skin. The kidneys are the principal excretory

Hyp IT Po VIVE

Fic. 277. — Brain of dog. Side view.

I-XII, cranial nerves; B.ol, olfactory lobe; HH, cerebellum; Hyp, hypo-
physis; Med, spinal cord; NH, medulla oblongata; Po, pons Varolii; VH,
cerebrum; Wu, cerebellum. (From Wiedersheim.)
organs. The urine which they extract from the blood is carried
by two slender tubes, the ureters, into a thin-walled, muscular
sac, the urinary bladder. At intervals the walls of the bladder
contract, forcing the urine out of the body through the urino-
genital aperture. In the skin of man are numerous sweat glands
and sebaceous glands which aid the kidneys in excreting waste
material.

Nervous System. — The nervous system is very highly de-
veloped in mammals. The brain (Fig. 277) differs from that
of the lower vertebrates in the large size of the cerebral hemi-

408 PRACTICAL ZOOLOGY

spheres and cerebellum. The cerebral hemispheres are marked
by depressions which divide the surface into lobes or convolu-
tions not present in birds. In man the cerebrum constitutes
nine-tenths of the bulk of the brain, and the convolutions are
very deep.

Sense Organs. — THE EYE (Fig. 278). — The eyes lie within
protective cavities, the orbits. In the center of each eye there

Pf
Hf
R’ IX
Stk Sree N
wAw ed
Fic. 278. — Section through human eye.

A, choroid; B, image on retina; G, vitreous body; H, cornea; L, lens;
N, retina; p, pupil; Pf, object; R, iris; Sn. optic nerve; Stb, Stk, ciliary
muscle and ciliary fold; wAu, sclerotic. (From Schmeil.)

is an aperture for the entrance of light, forming the pupil.
This aperture contracts in a bright light and dilates in a faint
light. Directly behind the pupil is a lens-shaped body, the
crystalline lens. The space in front is filled with a watery fluid,
the aqueous humor; that behind the lens with a gelatinous
substance, the vitreous body. The eye is constructed on the
same plan as the camera of the photographer. On the retina,
as on the sensitive plate of the camera, there is formed an in-
verted and diminished image of the external world, and the
retina, being composed of nerve terminations sensitive to light,

THE STRUCTURE AND ACTIVITIES OF MAMMALS 409

transmits the image to the brain by way of the optic nerve.
The eyelids and eyelashes protect the eyes from injury.

THE Ear. — The ear (Fig. 279) is the organ of hearing. In
most mammals external, funnel-shaped projections catch the
sound waves. These waves enter the ear passage and induce

the hammer 7m the loops
, (Semicircular
Canals)
meatus
the drum
of the ear the
(Tym panic
Membrane) nell Tube
(Cochiea)

the anvil the stirrup

Eustachian tube
Fic. 279. — Middle and inner human ear. (From Peabody and Hunt.)

vibrations in the tympanic membrane, which are transmitted
to the small bones of the ear lying in the cavity of the tympanum.
The end of the innermost of the small ear bones (stapes) is
applied to a fine membrane of the inner ear, or labyrinth, which
lies in a corresponding bony cavity. This membrane in its turn
receives the vibrations and transmits them to a fluid contained
in the labyrinth. Thence the vibrations reach the terminations
of the auditory nerve, and are conveyed to the brain, where they
enter into the consciousness in the form of tones or noises.

Toucu. — Sensations of touch are conveyed by the whole
skin; as special organs of touch we may enumerate the tips of
the fingers, the lips with the special bristles, the wing mem-
brane in bats, as well as the tongue.

410 * PRACTICAL ZOOLOGY

SMELL. — The nose is the organ of smell. Its cavities are
lined with a membrane that is supplied with nerve endings from
the olfactory nerve. These are stimulated by substances in
the air that enter the nose during inspiration.

TasTE. — Organs of taste are present on the tongue and
enable mammals to determine the nature of the food they eat.

The Skeleton. — The skeleton of mammals (Fig. 280) con-
sists almost entirely of bone. It serves the same purposes as
does that of the frog (p. 254), but of course it differs some-
what in details of structure. The bones are similar in number
and position in all mammals, but they are modified according to
the habits of the species. A comparison of the bones in various
kinds of mammals and in other vertebrates makes a very
interesting study.

Reproduction. — Mammals are separated into male and fe-
male individuals. The essential organs of the male are two tes-
tes in which the spermatozoa arise and the ducts which carry the
spermatozoa to the outside. The female organs in which the
eggs are produced are the two ovaries. Connected with these
ovaries is an egg duct, the oviduct, into which the fully grown egg
passes. Here it is fertilized by a spermatozoon. In most cases
the eggs develop within the egg tubes of the mother. The young
embryo becomes connected with the wall of the egg tube by a
strand of membranes and blood vessels called the placenta.
Through the placenta, nourishment from the blood of the
mother is carried to the growing young. The interval between
fertilization and the birth of the young which develop from the
fertilized egg is known as the period of gestation. This period
varies in different species; in the rabbit it is thirty days. From
one to eight or ten young may be produced at a birth, and, in
the case of rabbits, several litters may be born during the year.

Animal Tracks. — The study of mammals in their native
haunts is rather difficult since most of them are so badly perse-
cuted by man that they conceal themselves as soon as they be-
come aware of the presence of human beings. We have already

THE STRUCTURE AND ACTIVITIES OF MAMMALS 4II

noted (p. 349) that the study of birds is often interfered with
by the leaves of trees which hide them. As a remedy it was

upper jaw bone

lower jaw bone
vertebrae
collar bone

shoulder blade
{\— breast bone

wrist bones
-hip bone

femur
knee cap

Fic. 280. — Skeleton of man. (From Peabody and Hunt.)

suggested that the call notes and songs of birds should be learned,
since we could thus recognize the birds, even if we could not see

412 PRACTICAL ZOOLOGY

them. There is also a remedy in the case of mammals, and that
is the study of animal tracks.

By an animal track is meant the footprint of an animal.
When these footprints continue for some distance, they consti-
tute a trail. Broken twigs and other signs are also of service
in deciding what kind of animal was present and what it was
doing. The character of the track depends somewhat on the
way the animal walks. The bears and man, for example, walk
upon the entire surface of the digits; they are called plantigrade.
Cats and dogs rest only upon the outer parts of the digits (digiti-
grade), and the hoofed mammals such as the horse are sup-
ported on the ends of the digits (unguligrade).

The snow records the movements of animals very clearly, and
consequently winter is the best time to study animal tracks
(Fig. 281). Hard, dry snow, like a daily newspaper, is only a
temporary medium, but tracks made in loose, wet snow may
last for weeks or months. Wet sand, clay, or mud are also good
recorders of animal tracks, but they can be found, as a rule, only
near bodies of water.

To determine the kind of animal one is tracking it is necessary
to know something of the habits of the animals, the structure
and size of their feet, and their methods of locomotion. Thus
the tracks of the mink, least weasel, and wolverine are shaped
alike, but that of the weasel is only an inch long whereas that of
the wolverine is five inches long, and the track of the mink may
end in a hole in the ice. The direction in which an animal was
moving may be determined by the claws.

Tracks frequently indicate emotions such as fear, dislike,
or anger. Fear or caution are most often expressed. For ex-
ample, a rabbit came through a forest and was forced to crossa
frozen creek before it could reach a swamp it wished to enter.
The distance between its tracks as it neared the creek decreased
from over three to less than two feet. It finally landed backward
at the edge of the forest, facing its track to see if it was being pur-
sued. Here it stayed long enough to melt the snow under its

THE STRUCTURE AND ACTIVITIES OF MAMMALS 413

paws. Then it bounded across the creek, covering about five
feet at each leap. Again it landed facing the track it had made.
Being satisfied that it had escaped observation, it entered the
swamp at a leisurely pace.

Fic. 281. — Tracks in the snow showing where a musk rat has come from and
returned to the water. (From Dugmore.)

Hibernation. — The problem of maintaining life during the
winter is solved by most birds by migrating. Mammals, on the
other hand, usually remain active, like the rabbit, or hibernate.
During hibernation the temperature of the body decreases and
the animal falls into a profound torpor. A cold-blooded animal,
like the frog, can be almost entirely frozen without being injured,
but warm-blooded animals must protect themselves from the

414 PRACTICAL ZOOLOGY

cold. They therefore seek a sheltered spot, such as a burrow in
the ground, in which to spend the winter. Furthermore, at this
time the fur of mammals is very thick and consequently helps
to retain the body heat.

The temperature of the body of hibernating animals becomes
considerably lower than normal; for example, a ground squirrel
which hibernated in a temperature of 35.6° F. had a body tem-
perature exactly the same. Respiration almost ceases; the heart
beats very slowly; and no food is taken into the body, but the
fat masses stored up in the autumn are consumed, and the animal
awakens in the spring in an emaciated condition.

The woodchuck is the most profound sleeper of our common
mammals. It feeds on red clover in the autumn, goes into its
burrow about October 1, and does not come out until April 1.
The bear does not sleep so profoundly, for if there is plenty of
food and the temperature is mild, he will not hibernate at all.
When the bear does hibernate, he scoops out a den under a log
or among the roots of a hollow tree. The raccoon and gray
squirrel sleep during the severest part of the winter; the skunk
spends January and February in his hole; the chipmunk wakes
up occasionally to feed; and the red squirrel is abroad practi-
cally all winter. Many other mammals hibernate for a greater
or less period of time.

Migration. — Comparatively few mammals migrate; this
may be due in part to their inadequate means of locomotion.
Among those that do migrate are the fur seal, reindeer, caribou,
bison, bat, and lemming. The fur seals in American waters
breed on the Pribilof Islands in Bering Sea, where they remain
from about May 1 to September 15. They then put out to sea,
spending the winter months making a circuit of about six thou-
sand miles.

The reindeer of Spitzbergen migrate regularly to the central
portion of the island in summer and back to the seacoast in the
autumn, where they feed upon seaweed. The bisons used to
range over a large part of North America, making regular spring

THE STRUCTURE AND ACTIVITIES OF MAMMALS 415

and fall migrations. They covered an area of about thirty-six
hundred miles from north to south, and two thousand miles from

east to west. Similar migrations are made by the caribou in
Newfoundland (Fig. 282).

Fic. 282. — The Newfoundland caribou in migration. (From Dugmore.)

The lemmings of Scandinavia (Fig. 283) are celebrated for
their curious migrations. They are small, gnawing animals about
three inches in length. “ At intervals, averaging about a dozen
years apart, lemmings suddenly appear in cultivated districts
in central Norway and Sweden, where ordinarily none live, and
in a year or two multiply into hordes which go traveling straight

416 PRACTICAL ZOOLOGY

west toward the Atlantic, or east toward the Gulf of Bothnia,
as the case may be, regardless of how the valleys trend, climbing
a mountain instead of going around it, and, undeterred by any
river or lake, keep persistently onward until finally some sur-
vivors reach the sea, into which they plunge and perish.”” They
are said to march in “ par-
allel lines three feet apart”
and “gnaw through hay
and corn stacks rather
than go around.”

Geographical Distribu-
tion.-— The various species
of mammals and other
animals are rather defi-
nitely restricted to certain
regions on the earth’s sur-
face. The earth has an
ee area of about two hundred
ie million square miles, five-
es nn dev maser a “eM ~~ eichths of which is covered
Bis chee ae ae lemming. —_ by the sea. This vast ter-

ritory is not uniform, but
presents a great number of sets of conditions. The principal
habitats are the solid earth, the liquids upon the earth, and the
atmosphere. The facts of geographical distribution have led to
the formulation of the three following laws: (1) the law of
definite habitats, (2) the law of dispersion, and (3) the law of
barriers and highways.

Tue Law or Definite Hapitats. — Among the most impor-
tant physical factors that determine the habitat of an animal are
temperature, water, light, and food. The continent of North
America has been divided by scientists into definite regions,
according to the sum total of the temperature during the season
of growth; and regions of a certain temperature, though widely
separated, are liable to support similar kinds of animals. Winter

THE STRUCTURE AND ACTIVITIES OF MAMMALS 417

is met by northern animals in one of four ways: (1) by dying,
e.g. adult butterflies, (2) migrating, e.g. birds, (3) hibernating,
e.g. bears, (4) remaining active, e.g. rabbits. Animals living
in tropical regions pass the summer in many cases in a torpid
condition, and are said to be estivating.

A certain amount of water is necessary for life, as the bodies
of animals are made up of from 55 to 95 per cent water. Ani-
mals living in dry climates have thick skins, and thus evaporation
is prevented.

Light plays a leading réle in the lives of animals; many species
require it, but others shun it as much as possible, principally in
order to escape their enemies.

And finally, food conditions are most effective, since carnivo-
rous animals, e.g. lions, must live where they may obtain flesh;
herbivorous animals, e.g. deer, must live where suitable vegeta-
tion abounds; and omnivorous animals, e.g. man, where both
flesh and vegetation of certain sorts exist.

THE Law oF Dispersion. — Animals tend to migrate from
the region of their birth. It is supposed that every animal pro-
duces a greater number of offspring than can be supported in its
particular habitat, and since parents and offspring cannot oc-
cupy the same area, some individuals must either migrate or
die.

Tue Law oF BarRIERS AND HicHways. — Animals are con-
fined to certain habitats by barriers and are prevented from en-
tering a new region by mountains or lakes, by lack of food, and by
the interference of other animals. Common barriers are moun-
tains, bodies of water, open country for forest animals, and for-
ests for prairie-inhabiting species. The reverse of a barrier is a
highway. Apparently there are routes of migration which are
especially favored.

CosmMopoLITaN Groups oF ANIMALS. — Some species of ani-
mals have wide ranges, e.g. some are found inhabiting practically
every large land area on the earth’s surface. This is true of

many birds and of the bats among the mammals.
2E

418 PRACTICAL ZOOLOGY

RESTRICTED GROUPS OF ANIMALS. —In a number of cases
certain species are restricted to very limited areas. The moun-
tain goat is found only in the higher Rocky and Cascade moun-
tains of Alaska. Islands are famous for the presence of re-
stricted species. Darwin’s descriptions of the animals he found
in the Galapagos Islands read like fairy tales.

Discontinuous DISTRIBUTION. — Whenever a species occurs
in two widely separated regions, it is safe to conclude that the
distribution must once have been continuous. Examples of
discontinuously distributed animals are rare. Tapirs inhabit
tropical America and nowhere else except the Malay Archi-
pelago.

REFERENCES

Mammalia, by F. E. Beddard. — The Cambridge Natural History, Vol. X.
— The Macmillan Co., N. Y. City.

The Life of Animals, by I. Ingersoll. —-- The Macmillan Co., N. Y. City.

American Animals, by W. Stone and W. E. Cram. — Doubleday, Page and
Co., N. Y. City.

American Natural History, by W. T. Hornaday. — Charles Scribner’s Sons,
N. Y. City.

Bulletins and Circulars published by the Bureau of the Biological Survey,
U.S. Department of Agriculture.

CHAPTER XXXIX
THE ORDERS OF MAMMALS

THE seventy-five hundred species of living mammals may be
grouped into a number of orders. Some orders contain more
common or more important species than others and a few are
represented only by a few little-known animals. The groups
described in the following paragraphs are for the most part illus-
trated by species that occur in this country.

Egg-laying Mammals. — These primitive mammals are con-
fined to Australia, New Guinea, and Tasmania. Their most
conspicuous peculiar-
ity is their egg-laying
habit, since they are
the only mammals that
reproduce in this way-
The young before
hatching live on the
yolk contained in the
egg. After hatching
they are for a time
nourished by milk from
the mammary glands.

The duckbill (Fig.
284) is adapted for
life in the water. It
possesses webbed feet,
a thick covering of waterproof fur like that of a beaver, and a
duck-like bill with which it probes in the mud under water for
worms and insects. During the daytime the duckbill sleeps in

419

Fic. 284. — The duckbill. (From Shipley and
MacBride.)

420 PRACTICAL ZOOLOGY

a grass-lined, underground chamber at the end of a long burrow
in the bank, the entrance of which is under water. In this
chamber one or two eggs are laid and the young reared.
Pouched Mammals. — These mammals occur mainly in Aus-
tralia and neighboring islands, but a few are natives of America.
Their method of reproduction is peculiar. The eggs are not laid,

BP Me,

Fic. 285. — Opossum. (Photo. by Hegner.)

but hatch within the mother’s body and the young are born in an
immature condition. The mother transfers them with her lips
to a pouch on the abdomen, where they are fed upon milk from
the mammary glands.

The opossum (Fig. 285) occurs in the Southern and Middle
States. It sleeps during the day, usually in a hollow tree or
stump, but is active at night, seeking insects, eggs, young birds
and mammals, berries, nuts, etc., which constitute its food.
When disturbed, the opossum frequently feigns death or “ plays
possum.’’ Two or three litters of from six to fourteen young
each are produced per year. The young remain with the mother
for about two months, at first in the pouch and later often riding
about on her back. Opossums are used as food in the south, and
when properly roasted, are excellent.

THE ORDERS OF MAMMALS 421

The kangaroos inhabit the Australian region. They range
in size from four to five feet in height to that of a small rabbit.
The fore limbs are very small and are used principally for grasp-
ing, whereas the hind limbs and tail are strongly developed,
enabling the animals to move about rapidly by a series of leaps.
The natives of Australia hunt them both for sport and for food,
In some localities they are injurious, since they eat the grass
necessary for feeding the cattle and sheep.

Insectivores. — These are small mammals that are nocturnal
in habit and feed principally on insects which they seize with
their projecting front teeth and cut into pieces with the sharp-
pointed cusps on their hind teeth. Most of them are terrestrial,

Fic. 286. — Garden mole. (Photo. by Brownell.)

but a number are subterrestrial (7.e. burrow). The moles are
stout, with short fore legs, fore feet adapted for digging, rudi-
mentary eyes, and without external ears. The common mole
(Fig. 286) ranges from southern Canada to Florida. It burrows
just beneath the surface of the ground, and is of considerable
benefit because of the insects it destroys, though its upheaved
tunnels soon disfigurea lawn. The rate of progress underground
is astonishing. One will tunnel a foot in three minutes, and a
single specimen under normal conditions is known to have made
a runway sixty-eight feet long in a period of twenty-five hours.

422 PRACTICAL ZOOLOGY

Vin Bats. — The bats
phe are easily distin-
i oh guished from other
* mammals by the mod-
ification of their fore
limbs for flight. The
fore arm and fingers
are elongated and
connected with each
7) other and with the
d -| hind feet, and usually
Frc. 287. A bat in a sleeping position. (Photo, the tail, by a thin
by Brosacll) leathery membrane.
Because of their remarkable powers of locomotion bats are
very widely distributed, occurring on small islands devoid of
other mammals. Most of them are small and chiefly nocturnal.
During the day they go into retirement and hang head down-
ward suspended by the claws
of one or both legs (Fig.
287). At night bats fly
about actively in search of
insects. Some of them live
on fruit, and a few suck the
blood of other mammals.
The largest of the bats
are the flying ‘“ foxes,” one

species of which has a wing
expanse of five feet and a
body one foot in length (Fig.
288). The fruit bats feed
on fruit, especially figs and
guava, and move about in
companies. The brown bat
is a common species inhabit-

i ‘ fs Fic. 268. Adiying “fos.” (U.S.
ing the United States. The Dept. of Agric.)

THE ORDERS OF MAMMALS 423

true vampire bats inhabit South America. They live on the
blood of horses, cattle, and other warm-blooded animals, and
sometimes attack sleeping human beings. Their front teeth,
which are very sharp, cut the skin, and the oozing blood is
lapped up.

Dasamie Se

oe PDAS VSM ni Be DBA SEA Aen SES

Fic. 289. — Red fox. (From Stone and Cram.
Copyright by Doubleday, Page and Co.)

Flesh-eating Mammals. — The teeth of carnivorous animals
are adapted for eating meat. The front teeth, or incisors (Fig.
276), are small and of little use; the canines (c), or eyeteeth,
are very large and pointed, enabling the animal to capture and
kill its prey; the premolars (pm 1, pm 4) and the first molar in
the lower jaw (m 1) have sharp-cutting edges; the other molars

424 PRACTICAL ZOOLOGY

are broad, crushing teeth; the fourth premolar of the upper
jaw (pm 4) and the first molar of the lower jaw (m 1) bite on one
another like a pair of scissors.

TERRESTRIAL CARNIVORES. — The dog family is represented
in North America by the wolves, coyotes, and foxes. The red
fox (Fig. 289) is persistently hunted by the poultry raiser because
of its fondness for chickens, but the benefits derived from the

es

Fic. 290. — Striped hyena of Africa. (From Beddard.)

destruction of field mice, rabbits, ground squirrels, woodchucks,
and insects, which constitute the larger part of a fox’s food,
probably more than repay the loss of a few fowls. Foxes seek
their food most actively in the morning and evening twilight.
They mate in February and March, and give birth on the aver-
age to five young in April or May.

The gray wolf of the Great Plains and the Rocky Mountains is
over four feet in length and very powerful. Wolves hunt in
packs, and are able to capture deer and other large animals.
They destroy great numbers of calves, colts, and sheep, and are
shot, trapped, or poisoned whenever possible. Many states pay

THE ORDERS OF MAMMALS 425

a high bounty for wolf scalps. The young, usually five in num-
ber, are born early in May. The hyenas (Fig. 290) which live
in Africa and Asia are closely related to the “dogs” of this
country.

The best-known members of the bear family in North America
are the polar bear, black bear, grizzly bear, and the large Alaska
brown bear. The polar bear frequents the coasts of the Arctic
Ocean, feeding
principally upon
seals, walruses,
and fish. The
black, brown, or
cinnamon bear is
a smaller species
abundantthrough-
out the forested
regions of North
America, where
not exterminated.
It is omnivorous, BE
being especially Fic. 291. — Grizzly bear. (From Ingersoll.)
fond of fish, blue-
berries, and honey. The grizzly bear of the Rocky Mountains
(Fig. 291) is now rare except in the Yellowstone Park and cer-
tain other limited localities.

The marten family contains a large number of small fur-bearing
animals. The otter, mink, weasel, marten, wolverine, skunk,
and badger are well known North American species. The
otter (Fig. 292) is over three feet in length. It makes its home in
a burrow in the bank of a lake or stream and is very fond of water,
being adapted for swimming by webbed feet and a flattened tail.
Fish constitute its chief food. Otter fur is very valuable, but it
cannot be obtained now except in certain parts of Alaska, where
the natives capture the sea otter, a single skin of which is worth
in some cases one thousand dollars.

PRACTICAL ZOOLOGY

Copyright by Doubleday, Page and Co.)

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se
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a
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Fic. 292.

THE ORDERS OF MAMMALS 427

The mink, like the otter, is fond of water. Its food consists of
birds, small mammals, and fish. The weasel (Fig. 293) is much
smaller but very bloodthirsty, often killing a great many more

Fic. 293. — Weasel. (Photo. by Carlin from Stone and Cram.
Copyright by Doubleday, Page and Co.)

birds and small mammals than it can eat. The skunk is
notorious because of the powerful odor of the secretion which
it can eject from a pair of scent glands at the base of the tail.
It feeds upon poultry, but pays for its board by killing grubs
and other noxious insects. The badger inhabits western North
America, lives in a burrow in the ground, and feeds on small
mammals. The wolverine (Fig. 294) occurs in the northern

428 PRACTICAL ZOOLOGY

United States; it is a fierce, greedy animal and a great thief,
stealing bait from traps, and even the traps themselves.

Fic. 294. — Wolverine.

(Photo. by Hegner.)

The cat family includes the cat, puma, leopard, lion, tiger,
lynx, and cheetah. The principal species inhabiting North
America are the wildcat, Canada lynx, puma, and jaguar. The

wildcat (Fig. 295), also called
bay lynx, bob cat, or catamount,
is a stubtailed animal about
three feet in length, and weighs
up to eighteen pounds. It was
formerly common, but is now
restricted to the forests of thinly
settled localities. Its food con-
sists of rabbits, poultry, and
other birds and mammals. The
Canada lynx, or “ loup cervier,”
is slightly larger than the wild-
cat, and can be recognized by a
tuft of stiff, black hairs project-
ing upward from each ear. It

I'ic. 295. — Wildcat. (Photo. by
Hegner.)

THE ORDERS OF MAMMALS _. 429

occurs in the northern United States and in Canada. The
puma, cougar, mountain lion, or panther, reaches a length of
over eight feet, of which the tail constitutes about three feet.
Pumas make their homes in rocky caverns or in forests. They
prey upon many kinds of animals, frequently causing much
damage by killing young colts; but they do not attack man
unless cornered. The jaguar is the largest American cat, but
only occasionally enters the southern United States from Mexico,
where it is common. It is afraid of man, but is a dangerous
enemy of deer, horses, cattle, and other animals.

The largest living cat is the t7ger, whose body reaches a length
of ten feet; it is most abundant in southern Asia. The lion is
found in Africa and certain parts of Asia; it is slightly smaller
than the tiger. The cheetah, or hunting leopard, occurs in parts
of Asia and Africa. In India it is trained to capture game.

AQUATIC CARNIVORES. — The aquatic carnivores are greatly
modified for life in the water. The hands and feet are fully
webbed, and serve as swimming organs, and the body has ac-
quired a fishlike form suitable for progress through the water.

The sea lion family includes the sealions and fur seals. The
fur seal breeds on the Pribilof Islands in Bering Sea, but at other
times occurs along the coast of California. Fur seals are polyg-
amous, and a single old male maintains control over from six
to thirty females. One young is produced each year. The
three-year-old males, called “ bachelors,” are the ones killed for
their fur. The California sea lion is the member of this family
most often seen in captivity. Squids, shellfish, and crabs are its
principal articles of food. Its fur is short, coarse, and valueless.

The walrus family contains the Atlantic walrus and the Pacific
walrus (Fig. 296). An adult male walrus is ten or twelve feet
long and weighs almost aton. The canine teeth of the upper jaw
are very long, and are used to dig up mollusks and crustaceans
from the muddy bottoms, and to climb up on the blocks of ice
in the Arctic seas, where it lives. Walruses have been almost
exterminated for their ivory, skins, and oil.

430 PRACTICAL ZOOLOGY

The seal family contains
a number of species, among
them the harbor seal,
which inhabits the North
Atlantic.

Gnawing Animals. —
The rodents are character-
ized by their long, chisel-
shaped incisor teeth which
are adapted for gnawing,

Fic. 296. — The walrus. (From Flower and the absence of canines,
and Lydekker.) leaving a gap between the
incisors and premolars. They are all small or of moderate size
and constitute the largest order of mammals. The best-known
North American families are the rabbits and hares, the squirrels,
the beavers, the
pocket-gophers,
the rats, mice,
etc., and the por-
cupines.

The squirrel
family includes
the woodchucks,
prairie dogs, tree
squirrels, chip-
munks, ground
squirrels, and
flying squirrels.
The common trec
squirrels (Fig.
297) are the gray,
fox and red squir-

rels; these are
all excellent

climbers, and be- PIG. 207. Fox squirrel, (Photo. by Lyndon.)

THE ORDERS OF MAMMALS 431

come quite tame if unmolested. With the probable exception
of the red squirrel or chickaree they should be protected.

Fic. 298. — Chipmunk. (Photo. by Carlin.)

The chipmunks (Fig. 298), or rock squirrels, are small animals
living usually on the ground among rocks. The ground squirrels
are sometimes called gophers (Fig. 299). They are inhabitants

Fic. 299. — Striped gopher at entrance to hole in ground.
(Photo. by Hegner.)

432 PRACTICAL ZOOLOGY

of open country and dig burrows in the ground. Their food
consists of grain which they carry into their burrows in cheek
pouches. The prairie ‘‘ dogs” (Fig. 300) are burrowing rodents
that live on our western plains in colonies of from forty to one
thousand. They feed upon grass and other vegetation. The

”

woodchucks, or ground “ hogs,” also live in burrows; but are usu-

Fic. 300. — Prairie dog at the entrance to its burrow.
(Photo. by Brownell.)

ally not colonial, and prefer hillsides or pasture land for their
homes. They feed on clover and other grass. The flying
squirrels are delicate nocturnal rodents that spend the day asleep
in a nest, usually in a cavity in a tree. They possess a thin
fold of skin between the fore and hind limbs on either side,
which, when spread out, acts like a parachute to sustain the
animal in the air.

The beaver family contains the largest gnawing animals in
North America. They are adapted for life in the water, possess-
ing webbed hind feet and a broad, flat tail. The dams of wood,
grass, and mud made by beavers are constructed for the purpose
of forming ponds in which houses are built with underwater
entrances (Fig. 301).

ORDERS OF MAMMALS

Fic. 3or.—A beaver dam. (Photo. furnished by American Museum of Nat-
ural History.)

The members of the pocket-gopher family possess large cheek
pouches, which open outside of the mouth, and strong fore feet

provided with large claws suitable for digging (Fig. 302). Grain
2F .

434 PRACTICAL ZOOLOGY

and vegetables are carried in the pouches, and such quantities
are destroyed as to make these rodents quite injurious to crops.

Fic. 302. — Pocket gopher. (Photo. by Hegner.)

The rat family includes the muskrats, lemmings, meadow mice,
white-footed mice, and rats. About one-fourth of our mammals
belong to thisfamily. They are all small, the muskrat being one
of the largest American species. The common house mouse, the
Norway rat, and black rat have all been introduced into this
country from the Old World.

The members of the porcupine family are characterized by the
presence of spines, which normally lie back, but can be elevated
by muscles in the skin (Fig. 303).

Toothless Mammals. — The toothless mammals are mainly
inhabitants of South America. The aifeaters possess a long,
narrow snout, and are provided with long claws on the fore feet
which are used to tear open ant hills. The tongue is long and
slender and serves to capture the ants upon which the animals

feed.

THE ORDERS OF MAMMALS 435

The sloths inhabit the tropical forests of Central and South
America. They live in the tree tops, and hang to the underside
of the branches by means of two or three long, curved claws.
Their food consists of leaves and buds.

Fic. 303.— Porcupine. (Photo. by Brownell.)

The armadillos (Fig. 138) are curious mammals with an armor
of bony plates. When disturbed, they roll up into a ball, in
which condition they are not easily injured. The nine-banded
armadillo lives in southern Texas.

Even-toed Hoofed Mammals. — This group contains the
majority of the ‘‘ game ” animals, and includes the pigs, hippo-
potami, camels, giraffes, deer, antelopes, sheep, goats, cattle, etc.

436 PRACTICAL ZOOLOGY

These animals are characterized by the presence of an even num-
ber of hoofed toes.

The term ruminant has been given to the animals belonging
to the camel, deer, giraffe, and ox families, since they ruminate
or chew their cud. The food of these animals is swallowed with-
out sufficient mastication; it is later regurgitated in small quan-
tities and thoroughly chewed. This method of feeding enables
“these comparatively defenseless animals to gather nutriment

Fic. 304. — Stomach of a ruminant opened to show internal structure.

a, csophagus; b, rumen; c, reticulum; d, psalterium; e, abomasum;
f, duodenum. (From Flower and Lydekker.)

in a short time and then retreat to a safe place to prepare it for
digestion.” A typical ruminant possesses a stomach consisting
of four chambers (Fig. 304). The food is first taken into the
rumen chamber (0), where it is moistened and softened ; it passes
back into the mouth as “ cuds ” and is ground up by the molar
teeth and mixed with saliva. When the cuds are swallowed,
they are received by a second chamber (c), then pass into a third
chamber (d), and finally into the fourth chamber (e).

The deer constitute the majority of the American hoofed
mammals. Their horns or antlers are solid, and are shed annu-
ally. The best-known species are the wapiti or elk and Virginia
deer, with round horns, and the caribou and moose, with flat
horns.

THE ORDERS OF MAMMALS 437

The moose (Fig. 305) is the largest member of the family and
possesses the most massive antlers. It inhabits the woods of the
northern United States and British America, and feeds on bark,
twigs, leaves, moss, and lichens.

Fic. 305. — Moose. (From Ingersoll.)

The woodland caribou (Fig. 282) lives in the forested parts of
northern Maine and Montana and British America. The
female caribou is our only female deer that bears antlers. The
reindeer belongs to the same genus.

The wapiti or elk is the largest round-horned deer (Fig. 306).
It is easily bred in confinement, and is common in zoological

438 PRACTICAL ZOOLOGY

lic. 306. — Elk or wapiti. (From U.S. Dept. of Agric.)

parks. The Virginia or white-tailed decr (Fig. 318) is the best
known and most widely distributed of all our species. It is an
inhabitant of forests.

The pronghorn antelopes are confined to the open country of

THE ORDERS OF MAMMALS 439

western North America. Their horns are hollow, branched,
and shed annually.

The ox family contains the gnus, Rocky Mountain goats,
sheep, goats, musk oxen, and bison. These are all ruminants,
and both males and females usually possess unbranched, hollow
horns, which fit over bony prominences on the skull and are not
shed annually. The best-known American. forms are the bison,
musk ox, bighorn, and mountain goat.

Fic. 307. — Bison. (Photo. by Hegner.)

The bison (Fig. 307), up to the year 1870, ranged over a large
part of the Great Plains and other portions of North America.
It was persistently hunted, chiefly for its hide, until most of its kind
had been killed. In 1903 it was estimated that about six hun-
dred wild individuals and one thousand captive specimens still
existed. The musk ox lives on the Arctic barrens of North Amer-
ica. It has a long, shaggy coat, and the male has a strong,
musky smell. The Eskimos use it for many purposes. The
bighorn, or mountain sheep (Fig. 308), is an inhabitant of the
slopes of the Rocky and Sierra mountains above timber line. It
seeks the more sheltered valleys in the winter. The mountain

440 PRACTICAL ZOOLOGY

Fic. 308. — Rocky mountain bighorn or mountain sheep.
(From Ingersoll.)

goal occurs in the higher Rocky and Cascade mountains to
Alaska. It is covered with long, white hair, has slender black
horns, and is an expert climber.

3

THE ORDERS OF MAMMALS 441

Odd-toed Hoofed Mammals. — The horses, tapirs, and rhi-
noceroses which belong to this order are characterized by the
presence of an odd number of hoofed toes. The horses, zebras,
and asses of the horse family have but one functional toe on each
foot, and two lateral splints. The common horse, of which over

_ sixty domesticated races exist, is not now known in a wild state.

Fic. 309. — Zebra. (From Lydekker.)

The Nubian ass is probably the parent of the domestic donkey.
The zebras (Fig. 309) are confined to Africa. The tapirs have four
toes on the fore feet and three on the hind feet. The American
members of this group have a long, prehensile nose. They feed
on soft plants and are hunted for their flesh. The rhinoceroses
are large, thick-skinned mammals with one or two epidermal
horns on the nasal and frontal bones.

442 PRACTICAL ZOOLOGY

Elephants. — There are two species of elephants. The
Asiatic elephant inhabits the jungles of India. The African
elephant lives in tropical forests and is hunted for its tusks.
Both species possess five digits on each foot; are covered by a
thick, loose skin (whence they are called pachyderms) and a thin
coat of hair; have a long, muscular proboscis with nasal open-
ings at the tip; are provided with tusks which develop from the
incisors; possess small eyes and tail and enormous ears; and
are without canine teeth. The skull is massive, and the grinding
teeth are very large.

Whales. — Whales are adapted to life in the water. They pos-
sess a very large head with elongated face and jaw bones; the
fore limbs are modified as paddles; the tail is flattened horizon-
tally and forms two lobes, the “flukes”; the eyes are small, and
there is no external ear. The nostrils form a single opening, and

Fic. 310. — The sperm whale. (From Flower and Lydekker.)

the air, which is forced from it, condenses in the cold atmosphere,
appearing like a spout of water. Beneath the skin is a thick
layer of fat, or “ blubber,” which retains the body heat. The
tecth are numerous and conical in shape.

Toornep Wuates. — The common dolphin is a toothed whale
about seven feet in length; it occurs in the Mediterranean and
in the warmer portions of the Atlantic. The sperm whale (Fig.
310) reaches a length of seventy-five feet, and is the largest
toothed whale. Its oil, spermaceti, and blubber are sought by
whalers. Cephalopods are its principal food.

WHALEBONE WHALES. —- The whalebone whales possess teeth
only in the embryo; they are provided in the adult stage with

THE ORDERS OF MAMMALS 443

numerous plates of whalebone, which are horny and frayed out
at the end. In feeding, the whale takes large quantities of water
into its mouth, and then forces it out through the sievelike
whalebone, retaining any small organisms that may have en-
tered with the water.

The sulphur-bottom whale (Fig 311) is the largest of all whales
and the largest living animal, reaching a length of ninety-five
feet, and a weight of about 294,000 pounds; it inhabits the

Fic. 311. — Skull of Greenland whale showing whalebone. (From Sedgwick.)

Pacific from California to Central America. The Greenland
whale, or bowhead, occurs in polar seas and reaches a length of
about sixty feet. One animal yields nearly three hundred barrels
of oil and about three thousand pounds of the best whalebone.

Primates. — The primates inhabit chiefly the warm parts of
the world. They are mostly arboreal in habit, and are able to
climb about among the trees because the great toe and thumb
are opposable to the digits, adapting the hands and feet for
grasping. A few primates lead a solitary life, but most of
them go about in companies. Fruits, seeds, insects, eggs, and
birds are the principal articles of food. One young is usually
produced at a birth, and it is cared for with great solicitude.

The Jemurs (Fig. 312) ate quadrupeds and small or moderate
in sizef they are covered with fur, and usually possess a long
tail.

444 PRACTICAL ZOOLOGY

The Sowth American monkeys are arboreal and of small or medium
size (Fig. 313). The tail is usually long and prehensile, aiding in
climbing. The space between the nostril openings is wide.

Fic. 312. — Ruffed lemur. (From Elliott. Courtesy American Museum of
Natural History.)

The Old World monkeys are mostly quadrupedal (Fig. 314)
and usually possess a long tail which is never prehensile; their
nostrils are separated by a narrow space, and many of them
have cheek pouches.

The anthropoid apes are the primates most nearly like man.
The tail is absent and locomotion is often bipedal. There are

THE ORDERS OF MAMMALS 445

four genera in the family: (1) gibbons, (2) orang-utans, (3) go-
rillas, and (4) chimpanzees.

BE

Fic. 313. — White throated capuchin, a South American monkey. (From
Elliott. Courtesy American Museum of Natural History.)

The gibbons (Fig. 315) are arboreal, have a slender body and
limbs, and reach a height of not over three feet.

446 PRACTICAL ZOOLOGY

The orang-ulans (Fig. 316) are confined to Borneo and Sumatra.
They live principally in the tree tops, where they construct a
sort of nest for themselves. Orang-utans are about four and a
half feet in height, and when walking, use their knuckles as well

Fic. 314. — Bengal macaque, an Old World monkey. (From Elliott. Cour-
tesy American Museum of Natural History.)

as their feet. The brain of this species is more nearly like that
of man than the brain of any other animal.

The gorilla inhabits the forests of western Africa. It is
arboreal, feeds mainly on vegetation, has large canine .teeth,
reaches a height of five and a half feet and a weight of
about five hundred pounds, walks on the soles of its feet aided
by the backs of the hands, and is ferocious and untamable.

The chimpansee (Fig. 317) also lives in West Africa. It re-
sembles the gorilla, but has shorter arms and a smoother, rounder
skull. It is easily tamed.

THE ORDERS OF MAMMALS 447

The family Hominide contains the single living species,
Homo sapiens, or man. Man differs from the other primates

Fic. 315. — The hoolock, a gibbon. (From Elliott. Courtesy American
Museum of Natural History.)

in the size of the brain, which is about twice as large as that of
the highest monkey, and in his erect, bipedal locomotion. The
hairy covering is not well developed, and the great toe is not

448 PRACTICAL ZOOLOGY

opposable. The mental development of man has enabled him
to accommodate himself to every climate, and to dominate all
other animals.

The human race may be divided into three primary groups:
(1) the Negroid races, (2) the Mongolian, and (3) the Cau-

er

Fic. 316.— The Bornean orang-utan. (From Elliott. Courtesy American
Museum of Natural History.)

casian. The Negroid races possess frizzly hair, dark skin, a
broad, flat nose, thick lips, prominent eyes, and large teeth.
They are the African Negroes, the South African Bushmen, the
Central African and Philippine Pygmies, the Melanesians,
Tasmanians, and Australians.

The Mongolian races possess black, straight hair, a yellowish

THE ORDERS OF MAMMALS » 449

skin, a broad face with prominent cheek bones, a small nose,
sunken, narrow eyes, and teeth of moderate size. They are the
inhabitants of northern and central Asia, the Lapps, Finns,

Fic. 317. — Chimpanzee. (From Elliott. Courtesy American Museum of
Natural History.)

Magyars, Turks, Eskimos, Malay, brown Polynesians, and
American Indians.

The Caucasian, or white, races possess soft, straight hair, a
well-developed beard, retreating cheek bones, a narrow promi-
nent nose, and small teeth.

2G

CHAPTER XL

THE RELATIONS OF MAMMALS TO MAN

Domesticated Mammals. — The relations of mammals to
man are varied and complex. In the first place, domesticated
mammals are of almost inestimable value to man. Cattle
raising is the most important animal industry in this country.
Next in importance to cattle are horses. Sheep are utilized
extensively for meat and wool. In some countries goats are
used as draft animals and to furnish milk and meat. In the
tropical countries of the Old World, especially in desert regions,
the camel is the most important draft animal; its hair is valuable
in the manufacture of fabrics and brushes. In parts of South
America the llama and guanaco furnish the chief means of trans-
portation. The elephant is in Asia used as a draft animal, for
hunting, and for various other purposes; in Africa it is hunted
for the ivory in its tusks.

The most common domesticated mammals are the dog, horse,
ass, ox, sheep, goat, pig, and cat. The dog was probably the first
mammal to be domesticated. Dogs have been the companions
of man for many centuries; they have become changed while
under domestication, until there are now more than two hundred
breeds. In many cases local wild species of the genus Canis
have been tamed; for example, the original Arctic sledge dogs
were half-tamed gray wolves, and the dogs kept by our north-
western Indians were tamed coyotes.

The immediate ancestors of the horse are not known, and there
are at the present time no wild horses from which it could have

45°

THE RELATIONS OF MAMMALS TO MAN 451

arisen. It has probably developed from animals inhabiting the
semiarid plains of central Asia.

The ass is the favorite beast of burden in Eastern countries.
In this country the cross between a female horse and male ass
is known as a mule. The common ass of Europe and America
is descended, through the early Egyptian domestication, from the
African wild ass.

The oxen of Europe and America were probably derived from
the aurochs of Europe. The sacred or humped cattle of India
doubtless developed from one of the wild races that still roam the
Himalayan foothills.

Sheep have been domesticated for so many centuries that their
ancestors are not known, but there are many wild sheep from
which they may have originated. Goats have also been domes-
ticated since the earliest times, and their wild relatives are
abundant in many parts of the world.

The domesticated pigs are descended from the European wild
boar and the Indian wild boar.

The common house cat has a complicated ancestral history.
Its remote ancestor was probably the Egyptian cat from which
the Mediterranean cat, the wildcat, the jungle cat, the steppe
cat, and the Indian desert cat are descended. The European
and American domesticated cats were derived either from the
Egyptian cat or the Mediterranean cat, which soon became
crossed with the wildcat. A number of crosses have been made
between the various wild and domesticated cats, resulting in
a large variety of mixed breeds.

Game Mammals. — The game mammals are those that are
pursued and taken by sportsmen. Some of the more important
game mammals of North America are the moose, wapiti, deer,
bears, mountain lions, foxes, wolves, coyotes, wildcats, and
rabbits. Some of these are exceedingly destructive, and cer-
tain states pay a bounty for their capture; others, like the deer,
are of considerable value as food, though they may be injurious
to farms in thickly populated districts. The various states pro-

452 PRACTICAL ZOOLOGY

tect many of the game animals during certain seasons of the
year and in some cases for a period of years, so as to prevent
their extermination.

The deer, including the elk, reindeer, or caribou, and moose,
are the most important of the big animals in America. Only
one of them, the reindeer, has been completely domesticated ;
other species, however, can be kept easily in parks or game pre-
serves, and the constant demand for their flesh (venison) has
suggested the possibility of rearing them for food.

The Rocky Mountain elk or wapiti (Fig. 306) at one time
ranged over most of the United States, and ten million individ-
uals were probably present then. They have been rapidly
killed off, however, until now there are only a few outside of the
Yellowstone National Park and neighboring country. Insum-
mer the herds in this Park number about thirty thousand. Par-
tial provision for winter forage has been made by the government
within the Park, but the supply is not enough, and many of the
elk perish every winter. Elk meat is superior in flavor to most
venison, but our laws prevent its sale, and so no efforts are made
to rear these animals for market, although they can certainly
be bred successfully in captivity.

The common Virginia or white-tail deer (Fig. 318) occurs
almost all over this country and is therefore adapted to various
habitats. It is claimed that there are within the United States
250,000,000 acres of land not suited to tillage or to the pasture
of horses, cattle, or sheep on which deer andelk could be profitably
reared. The chief obstacle to profitable propagation of deer in
the United States is the restrictive character of state laws govern-
ing the killing, sale, and transportation of game. Many of the
states, following precedent, lay down the broad rule that all the
game animals in the state, whether resident or migratory, are
the property of the state. A few states except game animals
that are “under private ownership legally acquired.” A few
others encourage private ownership by providing a way in
which wild animals — deer and the like — may be captured for

THE RELATIONS OF MAMMALS TO MAN 453

domestication. Generally, when private ownership of game is
recognized by law, the right to kill such game is granted, but
the owner is hampered by the same regulations as to season,
sale, and shipment that apply to wild game. One by one, how-
ever, state legislatures are coming to recognize the interests of

Fic. 318. — Virginia or white-tail deer. (From U. S. Dept. of Agric.)

game propagators, and game laws are gradually being modified
in accordance with the change of view.

Predaceous Mammals. — Predaceous mammals feed upon the
flesh of other animals; if these animals are beneficial to man,
the predaceous mammal may be considered injurious, but if the
animals preyed upon are harmful to man, the predaceous mam-

454 PRACTICAL ZOOLOGY

mal is beneficial. The harmful predaceous mammals include
the wolves and cougars, which subsist largely upon big game,
sheep, cattle, and horses, and the house cat, which destroys
millions of birds in this country annually.

The other predaceous mammals are occasionally harmful,
but usually beneficial. Coyotes and wildcats, if poultry and
sheep are properly protected, devote their attention to rabbits
and other small mammals, and insects. The mink often commits
depredations upon poultry, but more than pays for this by de-
stroying meadow mice and muskrats. The weasel has a similar
bill of fare. The skunk destroys immense numbers of mice,
grubs, and noxious insects. The badger feeds largely upon
ground squirrels and other burrowing mammals and insects.

Wolves and coyotes cause a loss to the stockmen and farmers of
the United States of several million dollars annually, and in
some of the Northern States they threaten the extermination of
deer on many of the best hunting grounds. Many methods
have been used to prevent these losses. Elk are persistent
enemies of wolves, and a few of them are able to protect the
flocks of sheep in a thousand-acre pasture. In many states
bounties are paid for killing wolves and coyotes, but this has
not resulted in their extinction. The best way of preventing
their increase is to locate their dens and destroy the young each
year. The dens are natural cavities in rocky ridges or in
hollow logs. The wolves produce from six to ten young in a
litter and the coyotes from five to nine. Traps and poisoned
meat are also employed to capture or kill the adults. The
stock in small pastures can be protected from these predaceous
mammals by fences built so that they cannot get through.

The fox (Fig. 289), from its occasional misdeeds, is looked upon
by the majority of mankind as a deep-dyed villain that devotes
its entire life to robbery and derives all its forage from the
chicken yard or duck pen. Asa matter of fact, even in localities
where foxes are abundant, it is comparatively rare that poultry
is destroyed by them. On all well-regulated farms chickens

THE RELATIONS OF MAMMALS TO MAN 455

are housed at night, and the fox necessarily turns his attention
to field mice, rabbits, ground squirrels, and insects, such as
grasshoppers, crickets, and May beetles, to the great benefit
of the farmer. Although it is true that the fox destroys a con-
siderable number of birds, yet a ruffed grouse has been known
to rear its young within 100 feet of a fox den, and the tracks of
the young birds have repeatedly been seen on the fresh earth
before the entrance. Among the food brought to the young of
this litter and left outside were rabbits, mice, and a half-grown
woodchuck, but no birds of any kind.

The fur of the fox is a very valuable article of commerce. In
January, 1908, fox skins were quoted as follows: red fox, $1.50 to
$3.50 each; cross fox, $4 to $8; silver fox, $50 to $250; and
higher prices are sometimes paid for high-grade silver-fox skins.
The silver fox is a color variety of the common red fox. Its fur
is entirely black or more or less tipped with white. The rearing
of foxes for the sake of their fur is now carried on in several
localities, and undoubtedly fox farms will increase in number and
importance as the supply of skins from wild animals decreases.

Fur-bearing Animals. — The majority of the fur-bearing ani-
mals of North America belong to the marten family. This
family includes the otter (Fig. 292), mink, weasel (Fig. 293),
marten, wolverine (Fig. 294), and badger. Most of these ani-
mals are now scarce, and furriers are forced to use the skins of
other species, such as the skunk, muskrat, raccoon, fox, lynx,
black bear, and rabbit. Of all the products derived from wild
animals, furs are the most useful and valuable. Indispensable
to primitive man, they are scarcely less important to the most
civilized, for in warmth, beauty, and durability no manufac-
tured fabrics excel them. But expanding civilization is steadily
diminishing the supply of furs, both by increasing the demand
and by encroaching upon the territory in which they are pro-
duced. Many furs, as well as ivory, whalebone, and other
natural commodities, are already so scarce that the demand for
them is met largely by the substitution of inferior products.

456 PRACTICAL ZOOLOGY

The three fur animals still fairly abundant in the United
States are the muskrat, the mink, and the skunk. Of these the
muskrat is most likely to retain its numbers, since it multiplies
rapidly and, properly protected, is in no danger of extinction

Fic. 319. — Skunk. (From Ingersoll.)

except where swamps are drained for agriculture. The mink
breeds but once a year, and close trapping has already made it
scarce over wide areas. Its choice of banks of streams and marsh-
lands as a habitat aids in its preservation, but unless given more
adequate protection it cannot long survive the high premium on

THE RELATIONS OF MAMMALS TO MAN 457

its pelt. The skunk (Fig. 319), although not yet in danger of
extinction, is likely soon to be, since its pelt has great intrinsic
value and the demand for it has not yet fully developed. Within
a few years the price of its fur will probably be more than doubled.

Fic. 320. — Apple tree killed by rabbits. (From Lantz.)

The three fur animals named are economically the most im-
portant ones, because each is widely distributed and adapted to
a variety of climatic conditions. If, as is believed, they can be
domesticated or successfully reared in captivity, their breeding
may become a means of profit in most parts of the United States.
The skunk, especially, presents possibilities of widely extended
usefulness in domestication. At present it brings to the trappers
of the United States about $31,000,000 annually.

458 PRACTICAL ZOOLOGY

Gnawing Mammals. — Gnawing mammals are, on the whole,
injurious, since they include such notorious pests as the rabbits,
rats, and mice. Rabbits are vegetarians, feeding on leaves,
stems, flowers, seeds, buds, bark, and fruit. They damage
especially clover, alfalfa, peas, cabbages, and the bark of trees.
Young fruit, forest, and ornamental trees and shrubs in nurseries
are subject to injury from rabbits, and frequently the branches
and twigs within reach are cut off, or the bark is removed near
the base of the trunk, thus girdling the tree and causing its death
(Fig. 320).

Mice feed principally on stems, leaves, seeds, bulbs, roots, and
other kinds of vegetation. A single field mouse devours in one
year from twenty to thirty-six pounds of green vegetation, and
a thousand mice in one meadow would consume at least twelve
tons annually. Damage is done to meadows: and pastures, to
grains and forage, to garden crops, to small fruits, to nursery
stock, to orchards, to forests trees, and to parks and lawns
(Figs. 321 and 322).

“The rat is the worst mammalian pest known to man.
Its depredations throughout the world result in losses amount-
ing to hundreds of millions of dollars annually. But these
losses, great as they are, are of less importance than the fact
that rats carry from house to house and from seaport to sea-
port the germs of the dreaded plague.” The amount of loss
due to rats in the United States is not known; in Germany the
loss is estimated at $50,000,000 per year. The losses in this
country are as follows: a large part of the crops of cultivated
grains is often destroyed by rats; ‘‘ the loss of poultry due to
rats is probably greater than that inflicted by foxes, minks,
weasels, skunks, hawks, and owls combined ’’; rats are a serious
pest in game preserves, feeding upon the eggs and young of pheas-
ants, etc.; fruits and vegetables both before and after being
gathered are damaged by rats; and miscellaneous merchandise
in stores, markets, and warehouses suffers injuries second only
to that done to grains. Rats eat bulbs, flowers, and seeds in

THE RELATIONS OF MAMMALS TO MAN .459

greenhouses, set fire to buildings by gnawing matches, depre-
ciate the value of buildings and furniture, and are injurious in
many other ways.

Fic. 321. — White-footed mouse and young. (Photo. by Dugmore.
Copyright by Doubleday, Page and Co.)

‘Introduction of Foreign Mammals. — There is great danger
in introducing mammals into this country. The brown rat
reached this country about 1775, and is now, as pointed out
above, our worst mammalian pest. Rabbits which were intro-
duced into Australia about 1864 soon became so numerous that
legislative action was taken for their destruction. The mon-
goose of India destroys rats, lizards, and snakes; it was intro-
duced into Jamaica and other tropical islands and at first
proved very beneficial, but later it became a great pest, de-
stroying poultry, birds, young domesticated animals, and even
fruit. These disastrous results from the introduction of foreign
species of mammals led Congress to prohibit the importation of

460 PRACTICAL ZOOLOGY

most reptiles, birds, and mammals unless special permission is
obtained from the Department of Agriculture.

Fic. 322. — Apple tree injured by meadow mice. (from Lantz.)

REFERENCES
See end of Chapter XXXVI,

CHAPTER XLI

THE PROTECTION AND PROPAGATION OF WILD LIFE

IbEAs concerning the preservation of wild life have changed
within the past forty years, for whereas formerly only sports-
men were anxious to maintain a constant supply of game for
hunting purposes, now the general public is slowly coming to a
realization that unless our birds and mammals are protected
they will soon cease to exist. It is a well-established principle
that it is our duty to preserve the wild life of to-day for the benefit
of future generations. The steps necessary for such preserva-
tion are very simple and will not subject us to any particular
hardships. Only three out of every one hundred inhabitants
of this country are interested in killing birds and mammals, and
this small proportion might still be allowed to hunt in moderation
if proper laws were passed and enforced throughout the United
States.

The Need of Protection. — There has been a constant decrease
in the number of our birds and mammals ever since this country
was colonized. Part of this decrease has been brought about
by the ordinary effects of civilization, such as the building of
cities, the cutting down of forests, and the draining and cultivation
ofland. Animals that have been driven away in this manner are,
of course, lost to us, but we cannot be held responsible for their
disappearance. Only a small proportion of them, however, have
been eliminated in this way. Each year about half a million
shotguns and five million cartridges are sold in this country for
hunting purposes. In r1o11, 1,486,228 hunting licenses were

issued in twenty-seven of our states. Many persons, however,
401

462 PRACTICAL ZOOLOGY

hunt without licenses, and adding these together with those that
hunt in the remaining states, an estimate of 2,600,000 is reached.
This army of shooters annually kills off the natural increase as
well as part of the original supply of game. The result is a
noticeable decrease from year to year. It is reasonable to
state that there is at present only about two per cent as much
game as existed here fifty years ago.

Some of these hunters are more destructive than others, and
all of them should not be condemned. The term “game hog”
has of recent years been applied to those who kill more than a
reasonable amount of game. Even worse than the game hog
is the market hunter who kills birds and mammals by the
thousands, which he sells either for food or for millinery purposes.
“In a three months’ shoot in Iowa and Minnesota, one market
hunter killed 6250 game birds. In one winter’s duck hunting
in the South, he killed 4450 ducks. During his forty years’
market hunting he killed 61,752 ducks, 5291 prairie chickens,
8117 useful blackbirds, 5291 quail, 5066 snipe, and 4948 plover.
His grand totalof slaughter was 139,628 game birds and sundries,
representing twenty-nine species, several of them not game and
useful.”! Fortunately the sale of game has been stopped by law
in many states, and will no doubt soon be discontinued through-
out the entire country.

Several of the most notorious abuses of our wild life have been
the destruction of the vast herds of bison (buffaloes) and the
enormous flocks of passenger pigeons that once inhabited this
country. The last wild buffalo of the United States outside of
the Yellowstone National Park was killed in 1897. The original
range of the buffalo extended from central New York to eastern
Oregon and from northern Mexico to Great Slave Lake, nearly
touching the Atlantic coast in Georgia and the Gulf coast in
Louisiana. By 1730 the last buffalo east of the Alleghenies had
been killed. By 1810 none were to be found east of the Missis-
sippl. In 1870 those that were left were confined to two great

1 Hornaday, Wild Life Conservation.

PROTECTION AND PROPAGATION OF WILD LIFE 463

herds, the southern of which roamed the plains of eastern Colo-
rado and New Mexico, southern Nebraska, western Kansas and
Oklahoma, and northern Texas, while the northern herd ranged
from northwestern Nebraska and western Dakota on the east to
Montana and Wyoming on the west, and northward into Canada
to the northern limit of the original range of the species.
Twenty-seven years later not one was left in the United States
except a few in captivity.!

“ The passenger pigeon presents one of the marvels of bird life.
A century ago, when the country was new and less settled,
this bird, so wonderful for its gregarious habits, existed in flocks
of such gigantic proportions that the numbers appear absolutely
incredible. Thus Wilson, one of America’s pioneer ornitholo-
gists, writing about 1808, estimated that a flock observed by
him near Frankfort, Kentucky, contained not less than 2,230,-
272,000 birds, and Audubon five years later saw them at Hender-
son in the same state passing for three successive days in a prac-
tically continuous flock; ‘the air was literally filled with
pigeons, the light of noonday was obscured as by an eclipse,’
and the rush of wings was ‘ with a noise like thunder.’ Their
nesting places were necessarily of great extent. One described
by Wilson near Shelbyville, Kentucky, was several miles in
breadth and extended through the woods for upward of forty
miles. Every tree of suitable size was loaded down with nests,
a large hemlock, for example, often holding from twenty to forty.

“With the advent of the white man in this country, and the
blessing of civilization, the war upon the pigeon has been unceas-
ing! Whenever a roosting or nesting place was discovered it
was resorted to by a small army of despoilers, and with guns,
poles, clubs, sulphur pots, and nets the work of destruction
proceeded. Frequently from fifty to one hundred dozen were
taken at a single throw of the net. At the large Michigan nesting
it was estimated that five hundred netters were at work and their
average catch was 20,000 birds apiece, while for another resort

1 The Game Market of To-day.

464 PRACTICAL ZOOLOGY

it was estimated that hardly less than 1,000,000,000, including
those dead and wounded but not secured, and the myriads of
squabs left dead in the nest, were ‘sacrificed to Mammon’
during a single year.” !

Such wanton destruction as this rapidly leads to extermination.
Many species which have been exterminated over certain areas
where they were once abundant, are still present elsewhere.
For example, in Ohio the elk, bison, white-tailed deer, beaver,
and wild turkey have all been destroyed. Other species have
been persecuted to such an extent that only a few accidental
stragglers remain in remote localities; these species have been
practically exterminated. A few animals now exist in captivity,
but the species has been exterminated in its wild state. This is
true of the passenger pigeon and Carolina paroquet. Among
the birds that have become wholly extinct within the past
seventy years are the great auk, Labrador duck, and Eskimo
curlew.

Protective Measures. — The need of protection is obvious to
every one who studies the history of our wild life, and each should
do his best to protect the animals so far as he is able. This,
however, is not sufficient, and laws must be passed to prevent
the extermination of the birds and mammals that are still left
to us. The most important laws are the Lacey bird law, the
Bayne law, the McLean-Weeks law, and the plumage law.

The Bayne law prohibits the sale of all American wild game in
New York State. The McLean-Weeks law, or federal migratory
bird law, which was passed by Congress in 1913, prohibits spring
shooting of migratory birds, provides a closed season for most of
our shore birds, and shortens the open season for water fowl.
The plumage law is part of the new (10913) tariff bill. It
stopped the importation of the feathers or skins of all wild birds
except the ostrich. The Lacey bird law, which was passed in
1900, deals with the introduction of game animals into this coun-
try and the interstate commerce in game.

1Knowlton, Birds of the World.

PROTECTION AND PROPAGATION OF WILD LIFE 465

The Propagation of Wild Life. — Besides the efforts that have
been made to protect wild life, attempts are constantly on foot
to increase the number of birds and mammals. The introduc-
tion of foreign species is unnecessary, since our native animals
will restock the country if given the opportunity. Furthermore,
foreign animals often become pests when introduced, for ex-
ample, the English sparrow in the United States, the mongoose
in Jamaica, and the rabbit in Australia.

The National Parks, such as the Yellowstone, Glacier, and
Grand Cafion National Parks, have become natural refuges for
our persecuted game animals, since here they are fully protected.
“The most conspicuous of all cases of the recognition of protection
by wild animals is to be found in the Yellowstone Park. This
feeling of security is shared by nearly all the wild animals of the
Park, but it is most strikingly displayed by the herds of mule
deer, antelope, and elk that make their home near Fort Yellow-
stone and the Mammoth Hot Springs. In winter the mule deer
and antelope are fed on hay on the parade ground, as if they were
domestic sheep and cattle. At Ouray, Colorado, bands of moun-
tain sheep pose for photographs at short range, in the town, in
a manner that to every hunter of that wild and wary species is a
profound surprise.

“The Yellowstone Park grizzlies, and black bears also, are no
exceptions to the general influence of peace and protection.
These bears are now famous for the thorough and practical
manner in which they have accepted protection, and for years
have been reaping the benefits of it. They have become con-
firmed grafters. They not only make daylight visits to the gar-
bage heaps at the hotels, but they have been known to enter
the hotels and walk about in them, looking for offerings of food.”’!

That native animals will soon become abundant under pro-
tection in localities where they were once numerous may well be
illustrated by the restocking of Vermont with white-tailed deer.
“In the beginning, the people of Vermont exterminated their

1Hornaday, Wild Life Conservation.
2H

466 PRACTICAL ZOOLOGY

original abundant stock of white-tailed deer. In 1870, the
species was, so far as known, practically extinct throughout that
state. In 1875, a few business men of Rutland decided to make
an attempt to restock with deer the open forests around that
city. Accordingly they went to the Adirondacks, procured
seven female and six male white-tailed deer, took them to a
forest six miles from Rutland, and set them free.

“Those deer took kindly to their new home, persisted and pro-
ceeded to stock the state. None were killed, save a few that
were shot contrary to law, for twenty-two years.

“In 1897, it was decided that Vermont’s deer had become
sufficiently numerous and well established so that deer hunting
might begin; but on bucks only. In that year 150 head were
killed, and during the next three years about the same number
were taken annually. In 1901, 211 were killed; in 1902, 561;
in 1905, 791; in 1907, 1600; in 1908, 2208, and in 1909, the grand
total was 5261. The total weight of venison taken was 716,358
pounds. Computed at the lowest reasonable valuation, twelve
cents per pound, the total value for 1909 would be $85,962”
(Hornaday).

Many organizations are now engaged in the propagation of
wild life. The federal government has established the Bureau
of the Biological Survey, and has protected the game within
the National Parks. The next step in the progress of the work
should be a similar protection of the game in our National
Forests. The state governments have appointed commissions
for the protection and propagation of game, and many game
farms have been established where animals are raised for the
purposes of distribution throughout the states. Besides this
there are a few private preserves in this country.

Among the national organizations interested in game protection
are the American Bison Society, the American Ornithologists’
Union, the Campfire Club of America, the League of American
Sportsmen, the National Association of Audubon Societies, and
the New York Zoological Society.

PROTECTION AND PROPAGATION OF WILD LIFE 467

Apparently it is an easy matter to get the necessary laws
passed as soon as the general public is made to realize the
present condition of our wild life. It is one of the chief func-
tions of the organizations mentioned above to distribute a knowl-
edge of the value of protecting and propagating wild animals.
It is the duty of every one to help in this work, and no chance of
aiding in this great cause should be allowed to escape. No
better example of the results of a lack of education can be
cited than that of the campaign against the hawks in
Pennsylvania.

“Tn 1885, the rural feeling against hawks and owls reached the
high-water mark in Pennsylvania. In response to the demands
of the farmers of the state, the Pennsylvania legislature enacted
a law providing a bounty of fifty cents for the heads of hawks
and owls. Naturally, great slaughter of these birds ensued.
In two years, 180,000 scalps had been brought in and $90,000
had been paid out for thern.

“The awakening came even more swiftly than the ornithologists
expected. By the end of two years from the enactment of ‘ the
hawk law,’ the farmers found their fields and orchards thor-
oughly overrun by destructive mice, rats, and insects; and again
they went clamoring to the legislature, this time for the quick
repeal of the law. With all possible haste this was brought
about; but it was estimated by competent judges that in dam-
ages to their crops ‘ the fool hawk law’ cost the farmers of the
state of Pennsylvania more than $2,000,000”’ (Hornaday).

As noted in Chapter XL, there are a number of animals
that may be considered pests. These should, of course, be
kept under control. For reasons of sentiment they should not
be entirely exterminated, but their numbers may be reduced
to such an extent that they can do very little if any real
damage.

468 PRACTICAL ZOOLOGY

REFERENCES

Wild Life Conservation, by W. T. Hornaday. — Yale University Press, New
Haven, Conn.

The American Natural History, by W. T. Hornaday.
Sons, New York.

Our Vanishing Wild Life, by W. T. Hornaday. — Charles Scribner’s Sons,
New York.

Bulletins and Circulars prepared by the Bureau of the Biological Survey,
U.S. Department of Agriculture.

Charles Scribner’s

CHAPTER XLII

THE CONSERVATION OF OUR NATURAL RESOURCES

In the preceding chapters the principal groups of animals in
the animal kingdom have been considered from several stand-
points. We have learned that animals all need certain things,
such as protection from physical injury and from their enemies,
food for furnishing the power to carry on activities and to grow,
air for the oxygen necessary to release this power by oxidation,
and the ability to reproduce others of their kind to prevent the
race from dying out. We have also learned the methods used
by different kinds of animals in satisfying these needs and the
structures and physiology of the organs employed. This
knowledge is necessary before we can understand the relations
of animals to man and how we can eliminate harmful species
and encourage beneficial species. Throughout our studies this
economic or applied phase of our subject has been emphasized.
Still another viewpoint is possible, however, and that is the
relations between animals and the community in which we live, or
between animals and the state or nation. This is a part of our
subject that kas also been emphasized in the preceding chap-
ters.

The problems presented by one city in most cases differ some-
what from those of other cities. A seacoast community may
be vitally interested in the fishing industry; in a cattle raising
country a detailed knowledge of animal parasites and their
control is essential; and birds and insects are important every-
where, but the species differ and must be dealt with accordingly.
What groups of animals should be studied in detail depends

469

470 PRACTICAL ZOOLOGY

largely therefore upon the locality, but the general principles that
have been included in our studies can be applied everywhere.

The country in which we live was at the time of its settle-
ment perhaps the most richly endowed with what are called
natural resources of any in the world. Vast areas were covered
with forests; large, rapidly flowing rivers were ready to deliver
their power to whoever wished to use it; the soil was rich in
plant food and the climate suitable for agricultural pursuits;
extensive deposits of coal and other minerals were waiting to
be mined; the rivers, lakes, and surrounding seas were alive
with fish, oysters, lobsters, and other ‘‘ sea food’; the wood-
lands and prairies abounded with bobwhites, prairie chickens,
and other game birds; the Great Plains were thickly dotted
with huge droves of bison, deer, elk, moose; other game animals
were everywhere abundant, and fur-bearing animals could be
obtained with ease.

Only within recent years has any attention been directed
toward our methods of using these “‘ inexhaustible ”’ resources.
In 1908 the congress of the governors of all the states and
territories met to consider the question of conservation which
President Roosevelt considered “as the weightiest problem
now before the nation, as nobody can deny the fact, that the
natural resources of the United States are in danger of exhaus-
tion, if the old wasteful methods of exploiting them are per-
mitted longer to continue. The enormous consumption of
these resources, and the threat of imminent exhaustion of some
of them, due to reckless and wasteful use, once more call for
common effort and common action.”

The truth of this statement can easily be established. Lum-
bering has been carried on without regard to the future. [Water
power is continually wasted because it is not utilized. In many
countries such as China, Spain, Greece, and Palestine large
tracts are bare of soil where once were flourishing fields of grain.
Similar conditions exist in some parts of the United States and
threaten to occur in others. Our principal mineral resources are

THE CONSERVATION OF OUR NATURAL RESOURCES 471

coal and iron; others are petroleum, natural gas, lead, zinc, gold,
silver, and stone. The methods of mining these minerals, and
of using them after they are mined, are extremely wasteful.
Throughout this book an attempt has been made to indicate .
the value of animals as a natural resource. The bisons have been
practically exterminated; millions of passenger pigeons have
been destroyed until not a single one remains alive to-day ; the
elk, pronghorn antelopes, mountain sheep, and other big game
animals which were formerly abundant have decreased so
greatly that now very few exist outside of zoological parks; the
alligators, the seals, and the whales have been killed without
regard to the future; our game birds and insectivorous birds
have been persecuted and hordes of insects thus let loose upon
our fields and orchards; the terns, humming birds, and egrets
are destroyed for their plumes; our waters are rapidly being
depleted of fish, oysters, lobsters, etc.; and finally even human
lives are sacrificed because of the neglect of opportunities to
promote health by preventing the dissemination of disease germs.
Practical zoology is concerned with the conservation of our
natural resources so far as they are influenced by animals. What
can be done to prevent the waste of human lives has been in-
dicated in the crusades against the house (typhoid) fly and the
yellow fever mosquito. Some of the efforts of the national,
state, and city governments to prevent the destruction of useful
animals have likewise been described in connection with the
song birds, fish, and game. Attempts to stem the tide of de-
struction have been made and are now in progress, as indicated
by the review of the work being done by some of our scientific
institutions, as presented in Chapters XLI and XLIII. This
review indicates what our thoroughly enlightened people are
trying to do for the conservation of some of our natural resources.

REFERENCES

_ The Conservation of Natural Resources in the United States, by C. R. Van
Hise. — The Macmillan Co., N. Y. City.
Our Wasteful Nation, by R. Cronau. — Mitchell Kennerley, N. Y. City.

CHAPTER XLIII

THE PROGRESS OF ZOOLOGY

It is difficult to realize at this stage in the world’s history
that what to us are well-known facts were entirely unknown to
the men of past centuries. Zoological facts that are now com-
mon knowledge had to be laboriously worked out and estab-
lished — a process that has occupied the attention of thousands
of men for many centuries. Progress at first was very slow, but
the more we know the easier it is to advance, and hence zoology
and other sciences are moving forward more rapidly now than
ever before.

Many of the most important scientific discoveries are con-
nected with the names of certain men, and perhaps there is no
better way of presenting a brief résumé of the history of zoology |
than by referring to a few of the scientists who have added the
most to our zoological knowledge.

Aristotle (384-322 B.c.). — No one knows when man began
to study animal life. The pursuit of certain forms for food, the
domestication of others, and the practice of animal sacrifice
doubtless furnished some crude and scattered notions of anatomy,
physiology, and ecology, even in remote antiquity. The first
scientific treatises that had an influence upon modern zoo-
logical ideas were not written until about three hundred and
fifty years before Christ. At this time Aristotle’s works ap-
peared, and so careful were the observations of this remarkable
man that they were considered authoritative for twenty cen-
turies.

Aristotle was the foremost pupil of Plato and the tutor of
Alexander the Great. His greatest works were on the natural

472

THE PROGRESS OF ZOOLOGY 473

history of animals, the parts of animals, and the development of
animals. They reveal a remarkable familiarity with the facts of
comparative anatomy, physiology, and embryology. He was a
critical compiler, and, from the fabric of scattered facts and
fancies which existed at his time, produced a compact and
fairly accurate account of animals.

Middle Ages. — The Middle Ages are a blank, so far as zoo-
logical progress is concerned. Superstition was rampant, and
the belief in various fabled animals was prevalent. All zoo-
logical questions were referred to the ancient authorities, and
original investigation was at a standstill. In one controversy
a series of papers was published with respect to the number of
teeth in a horse’s mouth. In this instance not one of the writers
seems to have thought of examining an animal, but all were
satisfied to quote the words of men who had died centuries
before.

Linneus (1707-1778). — After the intellectual awakening
of the sixteenth century, naturalists no longer tried to cover the
entire field of zoology, but restricted themselves to certain phases
of the subject. Thus the Swedish scientist, Linnzus, chose
systematic zoology as a specialty and attempted to describe all
the existing species of animals and plants. He succeeded in
listing 4378 in the tenth edition of his greatest work, Systema
Nature. His great influence, and the wide recognition which
was accorded his work, made the systematic side of zoology
the most active field of investigation for a long time after his
death. The aim of the systematic zoologist has been to describe
all the species of animals, and to arrange them according to a
natural system, 7.e. a system that will show their true relation-
ships to one another.

Cuvier (1769-1832). — Systematic zoology led to careful
comparisons of the structures of one species of animal with
those of others, causing the development of the science of com-
parative anatomy. One of the greatest comparative anatomists
was the French scientist, Cuvier, who extended his studies over

474 PRACTICAL ZOOLOGY

the entire animal kingdom, and added a great mass of personal
observations to the many descriptions published by his pred-
ecessors. Besides a number of treatises on comparative anat-
omy, he wrote a book on the fossil remains of animals, which
founded the science of vertebrate paleontology. Among
Cuvier’s more noted successors were the Englishmen, Richard
Owen (1804-1892) and Thomas H. Huxley (1825-1895), and
the American, E. D. Cope (1840-1897).

Johannes Miiller (1801-1858).— The study of structure,
both of adults and of embryos, was accompanied by attempts to
determine the functions of organs. Harvey made his name
immortal by the discovery of the circulation of the blood.
Haller (1708-1777) helped the science of physiology by sum-
ming up the principal facts and theories of his predecessors.
Johannes Miiller founded modern comparative physiology, and
prepared a handbook of the physiology of man, based upon the
personally verified statements of
others and upon his own obser-
vations, which to this day has no
equal. He made use of the mi-
croscope, and brought to his
work a knowledge of physics,
chemistry, and psychology.
Since his time physiological in-
vestigations have progressed
along physical and chemical
lines, and vital activities are
now explained by many in
physico-chemical terms.

Charles Darwin (1809-1882).
— The ideas of special crea-
tion and spontaneous generation
which were once widespread were
replaced during the last century by the theory of organic evolu-
tion, largely through the writings of Charles Darwin (Fig. 323).

Fic. 323. — Charles Darwin.
(From Davenport.)

THE PROGRESS OF ZOOLOGY 478

The theory of special creation is that all animals were in the
beginning created by some omnipotent being. That of spon-
taneous generation holds that animals arise directly from in-
organic substances; for example, ancient naturalists believed
that frogs and toads arose from the muddy bottom of ponds
under the influence of the sun, and that insects originated from
the dew.

Darwin’s book, The Origin of Species by Means of Natural
Selection, which appeared in 1859, placed the theory of organic
evolution on a firm foundation. At the present time practically
all zoologists believe that animals can arise only from preéxist-
ing animals by reproduction, and that by changes of some sort
complex animals have evolved from simpler species. Argu-
ments in favor of this belief have been derived from the study
of comparative anatomy, physiology, embryology, classifica-
tion, geographical distribution, and of fossil remains of animals
that are found embedded in the earth’s crust. At the present
time zoologists take for granted that evolution has occurred,
but are actively engaged in efforts to discover how it has taken
place.

Gregor Mendel (1822-1884). One method of attacking
the subject of evolution is to study heredity; that is, the study
of the similarities of and differences between parents and their
offspring. This is especially effective when animals or plants
of different kinds are bred together. At the present time the
foremost law of heredity is that discovered by Mendel (Fig. 324),
a monk who lived in an Austrian monastery. Mendel crossed
different kinds of peas and found that the offspring all re-
sembled one of the parents. When these offspring were inter-
bred, however, three fourths of their offspring resembled one
grandparent and one fourth resembled the other grandparent.
This and other facts discovered by Mendel have been found
to hold true for many animals as well as plants and constitute
what is known as Mendel’s law.

Pasteur (1822-1895). — There are two kinds of science

476 PRACTICAL ZOOLOGY

usually recognized, pure science and applied science. Pure
science deals with facts without regard to their practical value
to mankind. Applied science applies the facts of pure science

Fic. 324. — Gregor Mendel. (From Punnett.)

in such a way as to benefit mankind. Thus pure science comes
first and is necessary before anything practical can be accom-
plished. Occasionally, however, a scientist appears who is

THE PROGRESS OF ZOOLOGY 477

able to combine the two; such a one was Louis Pasteur (Fig.
325).

Pasteur was born at Dole in eastern France in 1822. He
was particularly interested in chemistry, but is most famous
because of his contributions to biology. His first investiga-
tions were concerned with the phenomena of fermentation and
decay. By proving that only living microorganisms (yeast
and bacteria) can cause fermentation, he was able to suggest a
method of preventing this process by heating substances to
a temperature high enough to kill these germs. This method of
killing germs is now known as pasteurization and has saved
billions of dollars and thousands of lives since milk and other
liquids can be preserved in this way.

Pasteur’s attention was next called to a silk-worm disease
which was killing off the silkworms in France and Italy and thus
destroying a very important industry. By long investigations
he proved that certain germs in the eggs, larve, pupe, and adults
were responsible for the trouble, and by suggesting a scientific
method of control succeeded in eradicating the disease.

The Pasteur Institutes that now exist in many cities through-
out the civilized world have for their object the treatment of
hydrophobia. This disease was found by Pasteur to attack the
nervous system of victims bitten by mad dogs and other animals.
The treatment was also discovered by him. It consists in first
burning (cauterizing) the wound with strong nitric acid and
then injecting into the patient a specially prepared solution
(virus) every day for three weeks. Of over 20,000 cases treated
in Paris less than one per cent have died.

Pasteur’s discoveries were extremely important from the
standpoint of both pure science and applied science. They
also led more or less directly to discoveries made by his con-
temporaries and followers. Among these are Lister’s treatment
of wounds by means of antiseptics and Roux’s and Behring’s
antitoxin for diphtheria.

Zoological Progress of To-day. — There are many zoologists

478

PRACTICAL ZOOLOGY

Tic.

Louis Pasteur. (From Peabody and Hunt.)

THE PROGRESS OF ZOOLOGY 479

now living who will no doubt in the next generation be ranked
with those mentioned in the preceding paragraphs. These
men, their associates, and their students are all engaged in add-
ing to the sum of human knowledge so far as animals are con-
cerned. They are for the most part at work in universities,
museums, endowed institutions, or government institutions.

The professors. in nearly all universities are encouraged not
only to distribute knowledge by teaching, but also to add to our
knowledge by carrying on original investigations. The results
of these investigations are published in scientific magazines
such as the Journal’ of Morphology, the Journal of Experimental
Zoology, the Biological Bulletin, the American Naturalist in
this country and in the many foreign magazines of a similar
nature.

Natural history museums are often considered simply places
where stuffed animals are exhibited, but the best museums em-
ploy capable scientists who spend all of their time working over
the collections and publishing the results of their researches.
Some of the large museums in this country are the National
Museum in Washington, D.C., the Museum of Comparative
Zoology in Cambridge, Massachusetts, the American Museum
of Natural History in New York City, the Philadelphia Academy
of Sciences in Philadelphia, Pennsylvania, the Carnegie Museum
‘in Pittsburgh, Pennsylvania, and the Field Museum in Chicago,
Illinois.

There are very few endowed institutions for the advancement
of science, but those that have been established within recent
years in this country have accomplished a great deal for the
progress of science, both pure and applied. The largest of these
are the Carnegie Institution in Washington, D.C., and the
Rockefeller Institute in Brooklyn, New York.

The meeting place of the sea and land is especially rich in
the number of animals that have selected it as a habitat. It is
not strange therefore to find zoologists studying at the seashore.
There are several laboratories on our eastern coast and several

480 PRACTICAL ZOOLOGY

on our western coast. The largest of these is the Marine
Biological laboratory at Woods Hole, Massachusetts (Fig. 326).
Here several hundred men and women gather every summer
for the purpose of studying the animal life of the sea and of
discussing the facts and theories of zoology.

The government institutions where scientific work is carried
on are devoted largely to applied science. Besides the work

Fic. 326. — The marine biological laboratory at Woods Hole, Mass.

done by the United States Department of Agriculture at Wash-
ington there are experiment stations scattered about through-
out the country, usually connected with the state agricultural
colleges.

The United States Department of Agriculture is the largest
institution in this country devoted to the task of adding to our
knowledge of plants and animals and of distributing this knowl-
edge among the people. During the year 1913, 14,478 persons
were employed by this department and over twenty million
dollars were spent to carry on its work. The scientific bureaus
in the department are as follows: —

THE PROGRESS OF ZOOLOGY 481

Weather bureau Bureau of animal industry
Forest service Bureau of plant industry
Bureau of soils Bureau of biological survey
Bureau of chemistry Office of experiment stations
Bureau of statistics Bureau of entomology

Office of public roads

The bureau of animal industry, bureau of biological survey,
and bureau of entomology are especially interested in animals.

Four series of publications are distributed by the Department
of Agriculture: (1) popular and semi-technical bulletins dealing
with the results of investigations; (2) the Journal of Agricul-
tural Research for scientific papers, and the Experimental Sta-
tion Record; (3) Farmers’ Bulletins containing “ specific direc-
tions for doing things’; and (4) annual reports, etc. Besides
this the newspapers throughout the country are supplied with
“brief popular statements of facts,’ and news letters are
weekly sent out to more than 50,000 crop correspondents and
farmers. Literature on almost any subject dealing with the
rearing of animals and plants and the control of pests can be
obtained free of charge by writing to the Secretary of Agriculture,
Washington, D. C.

REFERENCES
From the Greeks to Darwin, by H. T. Osborn. — The Macmillan Co., N. Y.
City.
Biology and Its Makers, by W. A. Locy. — Henry Holt and Co., N. Y. City.
Mendelism, by R. C. Punnett. —The Macmillan Co., N. Y. City.

21

INDEX

All numbers refer to pages.

Scientific names are printed in italics.

Numbers in black

type are numbers of pages on which there are figures.

absorption, in crayfish, 134; in frog, 248.

Acarina, 120.

adaptations, of insects, 24-31.

adder, puff, 325.

adrenal bodies, 254.

aérial habitat, 2.

Agassiz Association, 390.

aigrettes, 349, 384, 385.

air, bladder, 275; sac, 340.

albatross, wandering, 365.

alimentary canal, 12, 13 (see digestion
and digestive system).

alligator, 332.

alternation of generations, 205-200.

alveoli, in lungs of frog, 250.

Ameba, 222-224; food of, 223; funda-
mental properties of, 241; locomotion
of, 223; physiological activities of,
223; reproduction of, 223.

Amphibia, 7, 234, 299-308; hibernation
of, 305; economic importance of, 307;
poisonous, 305; regeneration of, 304;
tailed, 299; tailless, 301.

Amphineura, 158.

anabolism, 241.

anaconda, 326.

anal spot, of Paramecium, 219.

anatomy, of mussel, 147.

animals (see mammals).

Annelida, 7, 168, 177.

Anodonta, 152.

Anopheles mosquito, 87, 227.

ant, and plant lice, 41, 42; house, 58-59.

anteater, 434.

antelope, pronghorn, 438-4390.

antenne, of crayfish, 131,
Cyclops, 140, 141.

antennule, of crayfish, 131, 133.

Anthozoa, 210.

anthrax, 100.

anus, of grasshopper, 12, 14.

aorta, of mussel, 147, 151.

apes, 444-446.

133; of

aphid, 41-42.

A ptera, 19, 108.

aqueous humor, 408.

Arachnida, 107; classification of, 119-
120; relations of, to man, 121-127.

Araneida, 120.

Arcella, 225.

Archaeopteryx, 360, 362.

Argonauta, 166.

Aristotle, 105, 472.

armadillo, 235, 435.

army worm, 33-35.

arteries, of frog, 249 (see circulation and
circulatory system).

Arthropoda, 7; classification of, 107.

Ascaris, 179, 182.

ass, 441, 451.

assimilation, 14, 220, 248.

atoll, 209, 210.

auditory, capsule, 254; organs, of grass-
hopper, 17.

Audubon Society, 385, 390.

auk, great, 363, 464.

auricle, of frog, 249 (see circulation and
circulatory system).

Aves, 234 (see birds).

Bacteria, 73, T4, 231; non-pathogenic,
74; pathogenic, 74.

badger, 427, 454, 455.

barb, 339, 346.

barbule, 339, 346.

barnacle, 138, 139-140.

barriers, law of, 417.

basal disk, of Hydra, 199.

basket star, 195.

bass, black sea, 288; large-mouthed
black, 287; rock, 287; small-mouthed
black, 287; striped, 288.

bat, 422.

beaks, of birds, 338, 343.

bear, 414, 465; black, 425; brown, 425;
grizzly, 425; polar, 425.

483

484

beaver, dam, 433; family, 432.

béche-de-mer, 1097.

bee, and flowers, 4.

beehive, 64, 65.

beetle, Australian lady-bird, 70, 71;
blister, 67; burying, 67; carpet, 60;

cucumber, 39; diving, 25; elm-leaf,
46, 47; ground, 69; mealworm, 59,
60; potato, 35-38, 37; scarab, 68;

tiger, 69; vedalia, 71; whirligig, 25.
bighorn, 430, 440.
bile, 247.
binary division, of Ameba, 223; of Para-
mecium, 221.
Biological Survey, United States, 300,

406.
birds, 7; altricial, 357, 359; anatomy
of, 340, 348; ancient, 361; as de-

stroyers of injurious animals, 377-380;
attracting, 391-397; baths for, 392;
beaks of, 338; beneficial, 378-380;
call notes of, 349; commercial value
of, 376-377; destruction of, 382-380;
diving, 364; domesticated, 380-381;
eggs of, as food, 376; feeding on moths,
45; feet, 337, 339; flightless, 363;
game, 360, 376; houses for, 393-307;
insectivorous, 380; land, 369; mating
of, 354; migration of, 350; natural
enemies of, 390; nest-building of,
354; of prey, 369; perching, 374;
precocial, 357, 350; protection of,
382-397; relations of, to man, 376-
381; shore, 367; skeleton of, 335, 336;
songs of, 349; structure of, 335-3490;
water, 364; wings of, 335.

bisexual reproduction, 262.

bison, 439, 462.

bittern, 350, 357, 366.

bivalve, 147 (see mussel).

blackbird, 375, 370, 380.

blackhead, 152.

bladder, of frog, 247, 252.

blood, of crayfish, 134; of grasshopper,
14-15 (see circulation).

blood corpuscle, r4.

bloodsucker, 175.

bluebird, 373, 383; feeding young, 395;
house for, 395-396.

bluegill, 287.

blue jay, 353.

blue racer, 325.

INDEX

boa constrictor, 326.

body cavity, of alligator, 331; of earth-
worm, 174; of man, 402.

body cells, of Volvox, 232.

bone, 254 (see skeleton).

brain, of dog, 407; of earthworm, 172;
of frog, 258, 259; of grasshopper, 12,
17; of lamprey, 269; of man, 407;
of mussel, 147, 150; of Planaria, 184
(see nervous system).

branchial filaments, 275.

Branchipus, 140, 141.

breathing pores, of grasshopper, Is.

bristles, of earthworm, 169, 170.

brittle star, 195.

budding, of ccelenterates, 206; of
Hydra, 199, 200, 203; of sponges, 212.

buffalo, 462.

bug, bed, 99, 100; green, 35, 36; pill,
129, 141; sow, 129, 141; tumble, 67,
68.

bullhead, 283.

Bursaria, 231.

butcher bird, nest, 346.

butterfly, cabbage, 38; milkweed, 31.

byssus, 152.

Calcarea, 217.

calciferous glands, 171.

camel, 436, 450.

canals, of sponges, 213-214.

canine teeth, 405.

capillaries, of frog, 249.

carapace, of lobster, 131.

Carchesium, 231.

caribou, 415, 437.

carnivorous animals, 405, 424-430.

carp, 280, 281.

cartilage, 243, 254.

castings, of earthworm, 171, 173.

cat, 428-429, 451; as destroyer of birds,
387; flea of, 52, 53; wild, 428.

catamount, 428.

caterpillar, 20; celery, 39; tent, 46.

catfish, 281, 283.

cattle industry, 450.

cell, 202, 240, 243.

cell division, 263, 264.

cement, 404, 405.

centipede, 82, 128, 129.

Cephalopoda, 158, 165-167.

cephalothorax, 131,

INDEX

cercaria, 187.

cerebellum, of frog, 258, 259; of man,
407, 408; of turtle, 311.

cerebrum, of frog, 258, 259; of man, 407,
408; of turtle, 311.

cervical groove, 131.

Cestoda, 185, 191.

Chetopoda, 177.

chameleon, 310.

cheetah, 429.

chickadee, 394-395.

chigoe, 52.

Chilomonas, 226.

Chilopoda, 129.

chimpanzee, 446, 449.

chinch bug, 33, 34, 35.

chipmunk, 388, 414, 431.

chitin, 16, 131.

chlorophyll, in Euglena, 224.

cholera, germs of, carried by house fly,
74, 709.

chromatin, 263, 26s.

chromosome, 263, 265.

chrysalis, 20.

cicada, 24, 25.

cilia, of Paramecium, 218, 219; on gills
of mussel, 149.

circulation, of crayfish, 1382, 134; of
earthworm, 171-172; of frog, 248; of
grasshopper, 14-15; of man, 406; of
mussel, 151.

circulatory system, 238; of grasshopper,
14-15.

Civic Zoology, 6.

clam, 7, 145-153; hard-shell, 156; little-

neck, 156; long-neck, 146; razor-
shell, 155, 156; soft-shell, 155 (see
mussel).

class, 104.

classification, 6-7, 103-110; artificial,
to2; natural, 102; of animals, 6-7;

of insects, 107-110; reasons for, 105;
system of, 103; value of, 106.

clavicle, 255 (see skeleton).

claws, of grasshopper, 11; of mammal,
401.

cobra, 331.

cochineal, 65.

cochlea, 409.

cockroach, 57-58.

cocoon, 20; of earthworm, 173.

cod, 289.

485

Celenterata, 7, 198-210.

ceelom, 174.

cold-blooded animals, 252.

Coleoptera, 109.

collar-bone, 255.

colony, dimorphic, 205; of honeybee,
205; of Protozoa, 231; polymorphic,
205.

color, of fish, 274; of frog, 304; of in-
sects, 29-31; of mammals, 4oo.

coloration, aggressive, 31; protective,
30; warning, 30.

columella, of snail shell, 159.

commensalism, 139.

conjugation, 221.

conservation of our natural resources,
460-471.

contractility, 241.

control, of house fly, 80-83; of insect
pests, 34, 46-47.

convolutions of brain, 407, 408.

coot, 367.

copperhead, 330, 331.

coral, 7, 208-210; organ pipe, 209;
polyp, 208; precious, 209; reef, 208.

cormorant, 365, 366.

corpuscles, blood, of frog, 248;
mammals, 406 (see circulation).

cosmopolitan animals, 417-418.

cougar, 420, 454.

covey, 369.

cowbird, 349, 356, 380.

coxa, I1.

coyote, 454.

crab, 7; blue, 137, 138; edible, 137, 138;
fiddler, 137, 138; hermit, 138; horse-
shoe, 119, 120; king, 119, 120; soldier,
137, 138; spider, 138.

crane, 367.

cranium, 254, 255.

crappie, 287.

crayfish, 130-136; absorption in, 134;
anatomy of, 131, 132; circulation in,
134; color of, 131; digestion in, 133;
exoskeleton of, 131; food of, 133;
habitat of, 130; injuries done by, 136;
locomotion of, 133; protection of, 130;
relations of, to man, 135; reproduc-
tion of, 134-135; respiration of, 134;
sense organs of, 132.

croaking, of frog, 246.

crocodile, 331-333.

of

486

crop, of bird, 348; of earthworm, 171;
of grasshopper, 12, 13.

crow, 375, 379, 389.

Crustacea, 107, 137-144.

cuckoo, 371, 380.

Culex mosquito, 87.

cuticula, of insects, 16.

Cuvier, 473.

Cyclo ps, 140, 141; and disease, 143, 181.

cyclostomes, 235, 268, 270. 2

cysticercus, 189, 190.

daddy longlegs, 120.

Daphnia, 140, 141.

Darwin, 4, 173, 474.

Decapoda, 137-

deer, 436, 438, 452-453, 465-466.

Demos pongia, 217.

dengue, carried by mosquitoes, 96.

dentine, 404, 405.

Dero, 170.

development, 269 (see embryology, and
metamorphosis).

devilish, 166.

diaphragm, 402, 407.

Difflugia, 225.

digestion, in crayfish, 133; in earth-
worm, 171; in frog, 246; in grass-
hopper, 13; in /fydra, 203; intra-

cellular, 203; in mammals, 403; in
mussel, 150; in Paramecium, 219.

digestive glands, of crayfish, 134 (sce
liver).

digestive system, 237-238 (see digestion).

digits, 255.

dimorphism, 205.

Diplopoda, 129.

Dipnoi, 284.

Diptera, 109.

dispersion, law of, 417.

dissimilation, 220.

distribution of animals, 416-418.

division of labor among cells, 202.

dog, brain of, 407; family of, 424-425;
flea of, 52, 53; prairie, 432; teeth of,
405.

dogfhsh shark, 278.

dolphin, 442.

domestic animals, parasites of, 48-56.

domesticated birds, 380.

dove, 369, 380.

drone honeybee, 63.

INDEX

duck, 381; Labrador, 414; wood, 366.
duckbill, 419.
dysentery, 78, 228.

eagle, bald, 366; golden, 379.

ear, of fish, 275; of frog, 258, 261; of
lamprey, 269; of mammal, 409.

earthworm, 161, 168-175; anatomy of,
169,170; burrows of, 168; circulation
in, 171; digestion in, 171; economic
importance of, 173; excretion in, 171;
food of, 171; locomotion of, 168;
nervous system of, 172; reproduction
of, 173; respiration of, 172; segmen-
tation of, 174; sense organs of, 172.

Echinodermata, 7, 192-1097.

ectoderm, of frog, 265, 266; of Hydra,
199, 202.

ectosarc, 222,

eel, 235; mud, 301, 302; true, 282, 283;
vinegar, 178.

eggs, of bird, 354, 358; of fish, 275, 276;
of frog, 264; of grasshopper, 18; of
Hydra, 199, 204; of mussel, 151; of
turtle, 311.

egret, 383, 384.

Elasmobranchti, 278-279.

elephant, 442, 450.

elephantiasis, 96, 181.

elk, 437-438, 452.

embryo, of frog, 264, 265.

embryology, of frog, 264, 267; of Hydra,
204; of insects, 19.

enamel, 404, 405. bs

endosarc, 222, 223.

endoskeleton, 254, 255

Entameba, 226, i

entoderm, of frog, 265, 266; of Hydra,
199, 202.

Entomostraca, 144.

epiphragm, 158.

Euglena, 224.

Eus pongia, 212, 216.

eustachian tube, 409.

excretion, 220; in earthworm, 171-172;
in frog, 252; in grasshopper, 15-10;
in mammals, 407; in mussel, rst.

excretory system, 238; in Planaria, 184
(see excretion).

exoskeleton, of crayfish, 131; of croco-
dile, 331; of grasshopper, 16.

eye, of crayfish, 132, 133; of fish, 271,

223%

INDEX

274; of frog, 258, 261; of insect, 17;
of lamprey eel, 269; of man, 408; of
snail, 160; of spider, 114.

eyelashes, 4og.

eyelid, 261.

eyespot, of Euglena, 224; of Planaria,
183.

falcon, 370.

family, 104.

fangs, 328.

fat, 390.

feathers, 339, 346, 377.

feces, 219.

feet, of birds, 337, 330.

femur, 256 (see skeleton).

fertilization, in earthworm, 173; in fish,
276; in frog, 264; in Hydra, 203; in
mammal, 410.

fever, dumdum,
relapsing, 229;
229.

fig insect, 69.

Filaria, 181.

filoplumes, 347.

fingerling, 204.

fins, 271, 273.

fish, 7, 278-284; artificial propagation of,
294; cave, 282, 283; deep sea, 283;
flying, 282, 283; food, 288; food of,
142; game, 285; hatching of, 295;
lungs of, 284; phosphorescent, 283;
relations to man, 285-298; relations
to mussels, 152.

fishing industry, 293.

fission, of Hydra, 203.

flagella, of Euglena, 224;
21t,

flamingo, 367.

flatworms, 183-1901.

flea, and bubonic plague, 98; cat and
dog, 52, 53; house, 53; jigger, 52;
water, 140, 141.

flesh, 256.

flounder, 288, 290.

fluke, liver, 186-188.

fly, bloodsucking, 100; Hessian, 35, 36;
horse bot, 48; house, 73-85; ichneu-
mon, 71; ox heel, 50, 51; sheep bot,
50; Spanish, 67; stable, 99, 100;
tachina, 34, 71; tsetse, 99, 100.

flycatcher, 375, 380.

229; recurrent,
Texas, 228;

229;
yellow,

of sponge,

487

food, of Ameba, 223; of birds, 348; of
crayfish, 133; of earthworm, 171; of
grasshopper, 13; of house wren, 378;
of Hydra, 200; of Paramecium, 219;
of reptiles, 332; of snail, 159; of
starfish, 194.

food vacuole, 219.

foot, of mussel, 146; of snail, 159; of
starfish, 193.

fox, 454-455; Arctic, 400; flying, 422;
red, 423, 424.

frog, 245-267; bull, 302, 307; green,
303; habitat of, 245; leopard, 302;
movements of, 245; muscular activity
of, 256; nervous system of, 256-261;
physiological processes in, 246-254;
reproduction of, 262; sense organs of,
261; skeleton of, 254; tree, 303.

fry, 204.

fur, 455.

gall, insect, 66, 67.
gallinule, 351, 357.
game, protection of, 466; slaughter of,

402.
ganglia, 17 (see nervous system).
gapes, 181.

gar pike, 280, 28r.

gastral cavity, of sponge, 211, 213.

gastric, juice, 247; mill, 134.

gastrocnemius muscle, 256, 257.

Gastropoda, 158, 167.

gastrovascular cavity of Hydra, 199, 203.

geese, 366, 381.

gemmule, 212, 214.

genital gland, of mussel, 147, 151 (see
reproduction).

genus, 104.

geographical distribution, 416-418.

germ cells, of grasshopper, 18; of Volvox,
232; continuity of, 232.

germ layer, 267.

germs of disease, 73, 74.

gestation, 410.

gibbon, 445, 447.

gid, ror.

gila monster, 321, 322.

gill arches, 275.

gills, of crayfish, 134; of fish, 275; of
frog, 266, 267; of lamprey eel, 269;
of mussel, 147, 148, 1409.

giraffe, 436.

488

gizzard, of bird, 348; of earthworm, 171.

gland, ductless, 253; of frog, 252; mam-
mary, 419; mucous, 253; poison, 253;
salivary, 253; sebaceous, 399, 400,
407; sweat, 407.

glandular cells, of Hydra, 201, 203.

glass ‘‘snake,” 322, 323.

Globigerina, 225, 226.

glochidium, 151, 152.

gnawing animals, 405.

gnu, 430.

goat, 418, 430, 450, 451.

Goniobasis, 162.

gopher, pocket, 433, 434; striped, 431.

Gordius, 178.

gorilla, 446.

goshawk, 388.

Grantia, 213.

grasshopper, 8-23; blood of, 15; cir-
culation in, 14; digestion in, 13; ex-
cretion in, 15; food of, 13; habitat
of, 9; legs of, 10; locomotion of, 9;
metamorphosis of, 19; nervous sys-
tem of, 17; protection of, 16; rela-
tions to man, 20; reproduction of, 18-
19; respiration in, 15; sense organs
of, 16; wings of, 9-10.

ground hog, 432.

grouse, 365.

growth, 241.

grub, 20.

guanaco, 450.

guinea fowl, 381.

gull, 365.

gullet, of Euglena, 224; of Paramecium,
219.

habitat, aérial, 2; fresh-water, 3; law
of, 416-417; of Hydra, 200; of
mammals, 398; parasitic, 3; sea

water, 3; terrestrial, 2.

haddock, 289.

hemoglobin, 248.

hair, contour, 400; of insects, 16; of
mammals, 399, 400; woolly, 400.

hake, 289.

halibut, 288.

Harvey, 248.

harvestman, 118.

hawk, 388, 467; chicken, 379; Cooper,
379; hen, 379; red-tailed, 347, 355,
356, 357, 370; roughleg, 379.

INDEX

hearing, of grasshopper, 17 (see ear, and
sense organs).

heart, of bird, 348; of crocodile, 331; of
frog, 249; of grasshopper, 12, 15; of
insect, 14; of lamprey eel, 269; of
mammal, 406; of turtle, 311 (see cir-
culation).

hellbender, 300.

Hemiptera, 108.

hen, 380.

herbivorous animals, 4os.

hermaphroditic animals, 185, 262.

heron, great blue, 364, 367; snowy, 384.

herring, 288.

hibernation, of Amphibia, 305; of mam-
mals, 413-414.

highways, law of, 417.

Hirudo, 175.

holophytic nutrition, 224.

holozoic nutrition, 224.

Hominid@, 447-449.

Homo, 447.

honeybee, 63-64; colony of, 205; legs
of, 27-29.

honeycomb, 64, 65.

honeydew, 42.

hoof, 401.

hookworm, 179, 182.

hopperdozer, 22.

horns, 4o1.

horse, 441, 450; botfly of, 48, 49; clas-
sification of, 104.

house fly, 73-85; breeding habits of, 80;
control of, 80-83; distributor of dis-
ease germs, 73-85; enemies of, 81;
foot of, 75; germs carried by, 77;
maggot of, 80, 81; mouth parts of, 76;
proboscis of, 76; pupa of, 80, 81.

humerus, 255.

hummingbird, 373; egg of, 354.

Huxley, s.

hyena, 424, 425.

hydatid, 190, ror.

Hydra, 198, 199-204; anatomy of, 199;
cells of, 201; digestion in, 203; ecto-
derm of, 202; entoderm of, 202; habi-
tat of, 200; nematocysts of, 200; pro-
tection of, 200; regeneration of, 204;
reproduction of, 203.

hydrophobia, 228.

Hydrozoa, 210.

Hymenoptera, 109.

INDEX

Iguana, 310, 320, 333.

incisors, 405.

infantile paralysis, 100.

Infusoria, 233.

ingestion of food, 223 (see digestion).

injurious, insects, to field crops, 33-35;
to fruits, 39-42; to garden vegetables,
35-39; to the household, 57-61; to
shade trees, 42-47.

insectivores, 421.

insects, 7; and disease, 98-101; bene-
ficial, 62-72; classification of, 107;
food for man, 67; injurious, 32-61;
parasitic, 71-72; predaceous, 70-71;
scavenger, 67.

intestine, of earthworm, 171; of grass-
hopper, 12, 14; of mussel, 147, 151
(see digestion).

invertebrates, 7, 234.

irritability, 234.

jaguar, 429.

jaws, of grasshopper, 13; of snail, 160,
161 (see skeleton).

jay, 375, 380.

jellyfish, 7, 207.

jewfish, 288.

jigger, 125.

joints, 256.

kallima butterfly, 29, 30.

kangaroo, 421.

katabolism, 220.

kidney, of frog, 252; of mammal, 407;
of mussel, 147, 151 (see excretion).

killdeer, 342, 353, 355, 367.

kingfisher, 344, 355, 368, 372.

kite, 370.

kiwi, 362, 363.

labial palps, of mussel, 147, 150.

labium, of grasshopper, 13.

Laboratory, Marine Biological, 480.

labrum, of grasshopper, 13.

lac, 65.

lacteals, 406.

lamprey, brook, 270.

lamprey eel, 268-270.

lark, meadow, 380; prairie horned, 342,
354.

larva, 20.

larynx, 406.

489

laws, game, 464.

leeches, 175.

legs, of grasshopper, 10-11; of honeybee,
27-29.

lemming, 415-416.

lemur, 443, 444.

lens, 261, 408 (see eye).

Lepidoptera, 108.

Leucosolenia, 211, 212.

lice, biting, 54; body, 54, 55; chicken,
54, 55; crab, 54, 55; elm-bark, 46;
head, 54, 55; plant, 35, 36, 41-42;
sucking, 54; wood, 141.

life, origin of, 244.

Limax, 161.

Linnzus, 67, 103, 473.

lion, mountain, 429.

liver, of frog, 247, 253; of mussel, 147,

I51.
lizards, 319-322.
llama, 450.

lobster, 130, 131, 142.

locomotion, of Ameba, 223; of crayfish,
133; of earthworm, 168; of fish, 272;
of grasshopper, 9-13; of insects, 24-
25; of mammals, 402; of mussel, 146;
of snail, 159.

locust, Carolina, 9, 14, 17; differential,
21, 22; migratory, 20; red-legged, 21,
22; Rocky Mountain, 18.

locust borer, 46.

lungs, of bird, 349; of frog, 247, 250; of
mammals, 406; of snail, 159, 161; of
spider, 113, 114.

Lymnaea, 162, 163.

lymph, 250.

lymphatic system, 406.

lynx, 428.

mackerel, 288, 289.

macronucleus, 219.

maggot, 20.

Malacostraca, 144.

malaria, 87-93, 227.

Malpighian tubules, 12, 16.

Mammalia, 7, 234.

mammals, 398-459; aquatic, 398; ar-
boreal, 398; circulation in, 406; claws
of, 401; color of, 400; digestion in,
403; domesticated, 450-451; ear of,
409; egg laying of, 419-420; excretion
in, 407; eye of, 408; flesh-eating, 423—

490

430; flying, 422-423; fur-bearing,
455-457; game, 451-453; geographical
distribution of, 416; gnawing, 430-434,
458-459; habitats of, 308, 410; hair
of, 400; hibernation of, 413; hoofed,
435-441; insectivorous, 421; internal
organs of, 402; locomotion of, 402;
migration of, 414, 415; nervous sys-
tem of, 407; orders of, 419-440;
pouched, 420-421; predaceous, 453-
455; protection of, 399; reproduction
of, 410; respiration in, 406; sense
organs of, 408; skeleton of, 410, 411;
teeth of, 404; toothless, 434-435;
tracks of, 410, 413.

man, classification of, 105.

mandible, 13.

mantle, 147, 140.

mantle cavity, 148.

marten, 425, 455.

martin, house for, 396.

massasauga, 328.

Mastigameba, 225, 226.

Mastigophora, 233.

mating, of birds, 354.

maxillw, of crayfish, 134; of grasshopper,
13.

maxillipedes, 134.

mayflly, 25.

medulla oblongata, 258, 259 (see nervous
system).

medusa, 207.

Mendel, 475, 476.

mesoderm, of frog, 265, 266.

mesoglea, 203, 207.

metabolism, 241.

metagenesis, 207.

metamere, 174.

metamorphosis, direct, 19; indirect, 20;
of insect, 19-20; of mussel, 152.

Metazoa, 202, 239.

mice, 388, 458, 459.

micronucleus, 219.

migration, of birds, 350-354; of caribou,
415 ; of fish, 276; of mammals, 414-416.

milkweed butterfly, 31.

millipede, 128.

milt, 276, 2905.

mimicry, 30.

mink, 427, 454, 455.

miricidium, 187.

mite, 119, 121; chicken, 124; face, 126;

INDEX

follicle, 126; gill, 127; harvest, 125,
126; itch, 125,126; scab, 124, 125.

mitosis, 263, 204.

moa, 361, 362.

moccasin, water, 329, 330.

mockingbird, 380.

molar teeth, 405.

mole, 421.

mole-cricket, 24, 25.

Mollusca, 7, 157, 158; classification of,
167; relations to man, 166.

molting, of birds, 347; of grasshopper, 18.

mongoose, 459.

monkeys, 444, 445, 446.

Monocystis, 226, 227.

moose, 437.

morphology, 16.

mosquito, 86-97; control of, go-96;
eggs of, 87, 90; enemies of, 90; and
intestinal worms, 181; larva of, 87,
go; malarial, 87-93, 227; mouth parts
of, 26; pupa of, 88, 90; yellow fever,
93-90.

moth, anatomy of, 26; clothes, 60; cod-
ling, 42; fish, 57, 58; gypsy, 44-406;
leopard, 45, 46; silkworm, 62; tus-
sock, 43, 44.

mother-of-pearl, 148.

mouth, of Exglena, 224; of frog, 246;
of Hydra, 199; of lamprey eel, 268,
269; of mussel, 147, 150; of Para-
mecium, 218, 219; of Planaria, 183.

mouth parts, of grasshopper, 13; of
house fly, 76; of insects, 25-26; of
mosquito, 26; of moth, 26.

movements, of frog, 245.

mucus, of snail, 158.

mud puppy, 299, 300.

mule, 451.

Miller, 474.

muscle, 247, 256.

muscular system,

museums, 479.

muskallunge, 286.

muskrat, 450.

mussel, 140, 145-153; anatomy of, 147,
149; circulation in, 151; classification
of, 157; digestion in, 150; habitat of,
145; reproduction of, 151; respiration
in, 140; sense organs of, 150; shell
of, 146-148.

Myriapoda, 107, 128-129,

238, 256, 257.

INDEX

nail, 401.

Nais, 176.

nasal cavities, 258, 26r.

Nautilus, 165, 166.

nectar, 64.

Nemathelminthes, 7, 178-182.

nematocysts, 200, 201.

nephridia, 169, 170, 172.

nephrostome, 170, 172.

Nereis, 176.

nerves, cranial, 259; motor, 259; sen-
sory, 259.

nervous system, 239, 407-408; central,
256; of earthworm, 169, 170, 172; of
frog, 256-261; functions of, 259; of
grasshopper, 12, 17-18; peripheral,
256; of Planaria, 184; sympathetic,
260; of turtle, 311.

nests, of birds, 354.

neuron, 2509, 260.

Neuroptera, 108.

newt, 300.

nighthawk, 368, 372.

Nosema, 230.

nostril, 275.

nucleus, 219, 220, 222, 223, 230, 240.

nudibranch, 163, 164.

nutrition, holophytic, 224; holozoic, 224.

nymph, 19.

octopus, 164, 166.

cesophagus, of crayfish, 1382, 134; of
frog, 247; of grasshopper, 12, 13; of
mussel, 147, 150.

olfactory capsules, 254.

olfactory organs, 17,
organs).

Oligochata, 177.

omnivorous animals, 406.

ophthalmia, 80.

opossum, 420.

optic lobes, 258, 259 (see brain, and ner-
vous system).

oral groove, 218, 219.

orang-utan, 446, 448.

orbits, of eye, 408.

order, 104.

organs, 237, 239.

oriole, 375, 380, 383.

Ortho ptera, 108.

osculum, 211, 212.

osprey, 385.

160 (see sense

491

Ostrea, 153.

ostrich, 377.

otter, 425-426, 455.

ovaries, of frog, 262, 264; of Hydra, 199,
200; of mammals, 410; of mussel, 147,
151 (see reproduction).

owl, 388, 467; great horned, 367, 371,
379; screech, 366, 396.

OX, 436, 430, 451.

ox botfly, 50, 51.

oxen, musk, 439.

oxidation, 251.

oyster, 153-155, 194.

oyster drill, 163, 164.

paddlefish, 279, 280.

pancreas, 253.

pancreatic juice, 247.

panther, 4209.

Paramecium, 218-221.

paramylum, 224.

parasites, of domestic animals, 48-56;
external, 4; habitats of, 3; internal,
4; intestinal, 178; of man, 48-56;
transmission of, 229.

parasitic, insects, 71-72; Protozoa, 226,
227; worms, 8o.

Parks, National, 465, 466.

paroquet, 371, 464.

parrot, 371, 383.

Pasteur, 475, 477.

peacock, 381.

pearl buttons, 166.

pearls, 167.

pebrine, 230.

pectoral girdle, 255.

pectoralis muscle, 256, 257.

Pelecypoda, 157, 167.

pelican, 363, 365.

pelvic girdle, 255.

penguin, 362, 363.

perch, 271-277; habitat of, 272; loco-
motion of, 272; pike, 292; protection
of, 273; reproduction of, 275-277;
respiration in, 275; sense organs of,
274; yellow, 285.

perching, of bird, 343.

pericardial cavity, 147, 151.

periostracum, 148.

periwinkle, 163, 164.

peroneus muscle, 256, 257.

petrel, stormy, 365.

492

pewee, wood, 345.

Phalangidea, 120.

pharynx, of earthworm, 171; of Planaria,
184

phylum, 1o4.

pheebe, 372.

Physa, 162.

physiology, 16.

pickerel, 286.

pig, 451.

pigeon, 369, 380; flying of, 334; pas-
senger, 382, 463-464.

pike, 286; wall-eyed, 292.

pinchers, 132, 133.

Piroplasma, 121, 228.

Pisces, 234, 268.

placenta, 410.

plague, 98-100.

plaice, 288.

Planaria, 183-185, 191.

plankton, 230.

Planorbis, 162, 163.

Plasmodium, 88, 226, 227.

Platyhelminthes, 7, 191.

Pleurocera, 162. .

plover, migration of, 351.

plumes, of birds, 377.

poison, of spider, 114, 118.

poison apparatus, of rattlesnake, 328.

poisonous, Amphibia, 305; reptiles, 333.

pollen, basket, 27, 28; brush, 27, 28;
comb, 27, 28.

pollination of flowers by insects, 68-70.

pollock, 289.

Polycheta, 177.

Polygyra, 162.

polymorphism, 205.

polyp, 7, 205.

porcupine, 435, 436.

pores, of sponge, 211, 213.

Porifera, 7.

Portuguese man-of-war, 206.

prairie chicken, 383.

prawn, 130, 142.

predaceous, insect,
453-455.

prehallux, 256.

-premolar teeth, 405.

primates, 443-449.

proboscis, of housefly, 76; of moth, 26;
of Planaria, 183, 184.

proglottides, 188, 189.

70-71; mammal,

INDEX

propagation of wild life, 465-468.

protection of wild life, 461-464.

protective coloration, 16, 29-31
color).

protoplasm, 202, 239-241; composition
of, 241; properties of, 222, 241.

Protozoa, 6, 73, 86, 121, 218-233; clas-
sification of, 233; colonial, 231; in
drinking water, 230; fresh-water, 224;
parasitic, 227; pathogenic, 227.

pseudopodia, 222, 233.

pterodactyl, 309.

Pulmonata, 162.

puma, 420.

pumpkin seed, 287.

pupa, 20.

pupil, in eye of frog, 262 (see eye).

python, 326, 327.

(see

quail, 380.

rabbit, 358.

raccoon, 414.

radial symmetry, 192, 198.

radio-ulna, 255.

radula, 157, 160, 161.

rail, 367.

rat, 388, 434, 458.

rattles, of rattlesnake, 328.

rattlesnake, 327, 328.

ray, 278, 279.

rectum, of grasshopper, 12, 14 (see diges-
tion).

Redi, 244.

redia, 187.

reef, coral, 208-209.

regeneration, of Amphibia, 304; of
Hydra, 204; of Planaria, 185; of
man, 204.

reindeer, 414-415.

relapsing fever, 1o1.

remora, 282, 283.

reproduction, of Ameba, 223; asexual,
203; of crayfish, 134; of earthworm,
173; of fish, 275-277; of frog, 262-
267; of grasshopper, 18-19; of Hydra,
203; of liver fluke, 186-188; of mam-
mals, 410; of mussel, 151; of Para-
mecium, 221; of Planaria, 185; sexual,
203; of spider, 114.

reproductive system, 239 (see reproduc-
tion).

INDEX

Reptilia, 7, 234, 309-333; economic im-
portance of, 332-333; habitats of,
310; poisonous, 333.

resemblance, protective, 30.

reservations, for birds, 390.

respiration, in aquatic insects, 25; in
birds, 349; in crayfish, 134; in earth-
worm, 172; external, 250; in fish,
275; in frog, 250; in grasshopper, 15;
internal, 250, 251; in lamprey eel,
269; in mammal, 406; in mussel, 149;
in snail, 161; in spider, 114.

respiratory system, 238 (see respira-
tion).

retina, 262, 408 (see eye).

rhinoceros, 441.

Rhizopoda, 233.

rodent, 430-434.

Roosevelt, 470.

roundworms, 178-182.

ruminant, 436.

salamander, 299, 300, 301.

saliva, 13.

salivary duct, 12, 13.

salivary gland, 12. 13.

salmon, 276, 292.

San José scale, 39-41, 40.

sapsucker, 379.

sartorius muscle, 256, 257.

sawfish, 278, 279.

scale insects, cottony maple, 46; fluted,
70-71; lac, 65; San José, 39-41, 40.

scales, fish, 273.

scallop, 156.

scapula, 255.

scarlet tanager, 383.

scientific terms, 106-107.

scolex, 188.

scorpion, 118, 119.

Scyphozoa, 210.

sea, anemone, 207-208; cucumber, 106,
197; horse, 283; lilies, 197; lion, 106,
429; pen, 209; urchin, 7, 196.

seal, 414, 420, 430.

secretion, 220, 252; internal, 253.

segmentation, 174.

semicircular canals, 409.

seminal vesicle, 462, 263.

sense organs, of earthworm, 172; of fish,
274-275; of frog, 261; of grasshopper,
16; of insects, 16-17; of lamprey eel,

493

269; of mammals, 408-410; of mussel,
150; of snail, 160; of spider, 114; of
turtle, 311.

septa, of earthworm, 169, 174.

sete, of earthworm, 170.

shark, 278.

sheep, 450, 451; botfly of, 50; liver
fluke of, 186-188; mites on, 125;
mountain, 439, 440; nodular worm of,
181, 182; stomach worm of, 181, 182;
ticks on, 53, 54.

shell, of mussel, 146-148; of snail, 158,
159; of turtle, 310.

shoulder blade, 255.

shrike, 346.

shrimp, 139, 140, 141, 142.

silk glands, 113, 114, 121.

silkworm, 62-63, 230.

silver fish, 57, 58.

siphon, of mussel, 146, 148.

skate, 278.

skeletal system, 238.

skeleton, of bird, 335, 336; of frog, 254,
255-256; of lamprey eel, 269; of
mammal, 410, 411; of starfish, 193;
of turtle, 310.

skin, of frog, 250, 252-253; of crocodile,
333-

skink, 321.

skipper, cheese, 59.

skull, of frog, 254, 255 (see skeleton).

skunk, 415, 427, 454, 455, 456, 457.

sleeping sickness, 99, 226, 228.

sloth, 435.

slug, 161.

smallpox, 228.

smell, in insects, 17; in mammals, 410
(see sense organs).

snail, 7. 158-161; food of, 160; fresh-
water, 162; locomotion of, 159; ma-
rine, 163; respiration in, 161; sense
organs of, 160; shell of, 158.

snakes, black, 325; blow, 325; coral,
331; eggs of, 324; eyelids of, 322;
garter, 324, 325; grass, 324, 325; har-
lequin, 331; harmless, 324; hognose,
325; horsehair, 178; poisonous, 326;
scales of, 322; teeth of, 324; tongue
of, 324; water, 325.

sole, 288.

somite, 174.

sparrow, chipping, 380; English, 379,

494

389; grasshopper, 380; vesper, 374,
375.

spawn, 276, 295.

species, 104.

spermatozoa, 263; of Hydra, 203; of
mussel, 151 (see reproduction).

spicules, of sponge, 214, 215.

spider, 7, 111-118; aérial, 115, 116;
anatomy of, 113; bites of, 118; crab,
116; house, 116; jumping, 116; red,
126; reproduction of, 114; respiration
in, 114; sense organs of, 114; spinning

organs of, 113; tarantula, 117; trap-
door, 117; water, 116; webs of, 111-
#23.

spinal cord, 258, 250, 260.

spinnerets, of spider, 115.

spiracle, of frog, 267.

spirochets, 228, 220.

spleen, of frog, 253.

sponges, 7, 211-217: bath, 212, 216;
classification of, 217; collecting, 215-
216; colonial, 210; fresh-water, 210;

relations to other organisms, 215; re-
production of, 212; simple, 211-212;
solitary, 212; spicules of, 214, 215;
spongin of, 214, 215.

spongin, 214, 215.

spores, of malaria parasite, 226.

sporocyst, 187.

Sporosoa, 227, 233.

sporulation, 223, 224.

squid, 164, 165.

squirrels, 388, 414; ground, 431; flying,
432; trec, 430.

stapes, 409.

starfish, 7, 193-194 ; relation of, to oyster,
155.

statocyst, of snail, 160.

Stentor, 225.

sternum, 255.

sting, of scorpion, 118, 119.

stinging cells, 200, 201.

stomach, of crayfish, 132, 134; of frog,
247; of grasshopper, 12, 14; of mussel,
147, 151; sucking, of moth, 26.

struggle for existence, 4.

sturgeon, 2709, 280.

sucker, 280, 281; of liver fluke, 186.

sunfish, 287.

swallow, 380; bank, 344, 355; cliff, 370,
371.

INDEX

swan, 366, 381.

swift, chimney, 369, 370, 374, 387.

swimmeret, of crayfish, 132, 135.

Sycoly pus, 163, 164.

symmetry, 192.

sympathetic nervous system, 12, 17-18,
260.

Syngamus, 181, 182.

Synura, 231.

syphilis, germ of, 229.

Tenia, 188.

tail, of bird, 330.

tapeworm, 7, 188-1091.

tapir, 418, 441.

tarantula, 117.

tarpon, 286, 287.

tarsus, of grasshopper, 11.

taste, in fish, 275; in insects, 17; in
mammals, 410 (see sense organs).

teeth, of frog, 246; of mammals, 404-
406; milk, 405.

Teleostomi, 279-284.

tendon, 256.

tentacles, of Hydra, 199, 200; of jelly-
fish, 207; of snail, 159, 160.

tern, 352, 357, 365.

terrapin, 313, 315, 333.

terrestrial habitat, 2.

testes, of frog, 262, 263; of grasshopper,
12; of Hydra, 199, 200; of mammals,
410; of mussel, 147, 151.

thorax, 10.

threadworms, 7.

thrush, 375.

thymus gland, 254.

thyroid gland, 254.

tibia, of grasshopper, 11.

tibiofibula, 256.

tick, 110; fowl, 124; sheep, 53-54;
spotted fever, 126; Texas fever, 121-
122.

tiger, 429.

tissues, 241-242.

toad, 106, 305-307; horned, 310, 320.

tongue, of frog, 246; of lamprey eel, 268,
269.

tortoise, 315, 316.

tortoise shell, 317, 333.

touch, in fish, 275; in insects, 17; in

trachea, of mammals, 400.

INDEX

trachee, of grasshopper, 15; of spider,
II4.

tracks, of mammals, 410-413.

Trematoda, 185, 191.

trepang, 197.

Trichina, 179, 180.

trichocyst, 218, 219.

trochanter, 11.

trout, 276, 285, 286, 280, 291, 295.

Trypanosoma, 226, 228.

tuberculosis, germs of, 74, 70.

Tubifex, 176.

tuna, 288.

Turbellaria, 185, 191.

turbot, 288.

turkey, 360, 381.

turtles, box, 316; egg laying of, 311;
fresh-water, 314; green, 317; habitat
of, 314; hawk’s-bill, 317, 318; internal
organs of, 311; leathery, 319; musk,
313, 315; nervous system of, 311; sea,
317; sense organs of, 311; skeleton
of, 310; soft-shelled, 314, 315; ter-
restrial, 316; tortoise-shell, 317, 318.

tympanum, of frog, 258, 261; of mam-
mal, 409.

Tyndall, 244.

typhoid fever, germs of, 74, 78.

umbo, 146, 147.

United States Department of Agricul-
ture, 480-481.

ureter, of frog, 252.

urine, 407.

Uroglena, 231, 232.

vacuole, contractile, 220, 222, 223; food,
219.

valves, of mussel, 146, 148.

ventral nerve cord, of
ves

ventricle, of frog, 249;
151 (see circulation).

ventriculus, 12, 14.

Venus, 156.

Venus’s flower basket, 217.

vertebral column, 254, 255.

Vertebrata, 7, 234-237.

viper, spreading, 325.

vireo, 349,

visual organs,
organs).

earthworm,

of mussel, 147,

17 (see eye and sense

495

vitreous body, 408.
vocal cords, 406.
Volvox, 231, 232.
Vorticella, 225.
vulture, 369.

walkingstick, 30.

walrus, 429, 430.

wampum, 156.

wapiti, 437-438, 452.

warbler, 375, 380.

warm-blooded animals, 252.

warning coloration, 30.

water, influence on animals, 3, 417.

water skater, 25.

water vascular system, 194.

wax, 63.

weasel, 454, 455.

web, of spider, 111-113.

weevil, alfalfa, 35, 36; bean, 39; cotton
boll, 35, 36; pea, 39.

whales, 442443.

whippoorwill, 348, 355, 372.

whitefish, 290, 291.

wildcat, 106, 454.

wings, of bird, 335; of grasshopper, 9-10.

wolf, 424, 454.

wolverine, 427-428.

woodchuck, 414, 434.

woodcock, 386, 387.

woodpecker, 348, 356, 372, 380.

wool, 400.

worker honeybee, 63.

worms, bag, 47; bladder, 189, 190;
bristle-footed, 177; cabbage, 38;

clam, 176; corn-ear, 35, 36; cut, 35,
36; duckweed, 176; fall web, 46, 47;
fresh-water, 176; hook, 179, 182; in-
testinal, 178; marine, 176; meal, 59,
60; nodular, 181, 182; parasitic, 80;
round, 178-182; sand, 176; silk, 62-
63; segmented, 7, 176; stomach, 181,
182.
wren, 375, 394, 395.

yaws, 80, 229.
yellow fever mosquito, 93-97.

zebra, 441.

zooid, 205.

zoology, 6; civic, 6;
progress of, 472-481.

practical, 471;

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