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Full text of "Practical zoology"

PRACTICAL 
ZOOLOGY 



HEGNER 




Cornell University Library 
QL 48.H46 



Practical zoology. 




3 1924 003 391 038 



WW Vk Cornell University 

-'-Bkf Library 



The original of this book is in 
the Cornell University Library. 

There are no known copyright restrictions in 
the United States on the use of the text. 



http://www.archive.org/details/cu31924003391038 



PRACTICAL ZOOLOGY 



THE MACMILLAN COMPANY 

NEW VORK ■ BOSTON • CHICAGO ■ DALLAS 

ATLANTA • SAN FRANCISCO 

MACMILLAN & CO., Limited 

LONDON • BOMBAY ■ CALCUTTA 
MELBOURNE 

THE MACMILLAN CO. OF CANADA, Ltd. 

TORONTO 



PRACTICAL ZOOLOGY 



BY 



ROBERT W. HEGNER, Ph.D. 

ASSISTANT PROFESSOR OF ZOOLOGY IN THE UNIVERSITY OF MICHIGAN : 
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 " 



Nefo Iforfe 

THE MACMILLAN COMPANY 

1915 



All rights reserved 



Copyright, 1915, 
By THE MACMILLAN COMPANY. 



Ret up and electrotyped. Published September, 1915. 



Notbjooti $resB 
J. 8. Gushing Co. — Berwick & Smith Co. 

Norwood, Maso., U.S.A. 



PREFACE 

This 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-XVIII, 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 interest 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. 



VI 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 Armor, Michigan, 
January, 1915. 



TABLE OF CONTENTS 

PAGE 

Preface v 

CHAPTER I 
Where Animals Live i 

CHAPTER II 

The Grasshopper 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). Protection (16). Sensations (16). Ner- 
vous system (17). Reproduction (18). Metamorphosis (19). 
Relation to man (20). 

CHAPTER III 

Some Insect Adaptations 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). 



Vlll TABLE OF CONTENTS 

CHAPTER VI 

PAGE 

Insects of the Household 57 

Silver fish (57). Cockroaches (57). Ants (58). Cheese 
skipper (59). Meal worm (60). Carpet beetle (60). Clothes 
moth (60). 

CHAPTER VII 

Beneficial Insects ......... 62 

Silkworm (62). Honeybee (63). Cochineal, lac, etc. (65) 
Food for man (67). Scavengers (67). Pollinization of 
flowers (68). Predaceous insects (70). Parasitic insects 
(70- 

CHAPTER VIII 

The House Fly and Disease ...... 73 

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 IX 

Mosquitoes and Disease ....... 86 

How germs are carried (86). What the germs are (86). 
The Malarial Mosquito (87). Anopheles the guilty 
mosquito (88). Losses due to malaria (89). Breeding habits 
of anopheles (90). Enemies of mosquitoes (90). Control of 
mosquitoes (90). Example of mosquito control (92). Driving 
away mosquitoes (92). The 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). 



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 . . . . . .111 

Where spiders live (in). Spiders with and without webs 
(in). Types of webs (in). How webs are built (113). 
Spinning organs (113). How insects are captured (114). 
Sense organs (114). Respiration (114). Reproduction (114). 
Aerial 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 (1 19") . 

CHAPTER XIII 

The Relations of Arachnids to Man 121 

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 

PAGE 

The Crayfish 130 

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 137 

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 Bivalves . . . -145 
Habitat (145). Locomotion (146). The protective shell 
(146). Structure of the shell (148). Movement of valves 
of shell C148). 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 . . . . .158 
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. . . 168 
Need of moisture (168). Burrows (168). Locomotion 
(168). Food (171). Digestion (171). Circulation and ex- 



TABLE OF CONTENTS XI 



cretion (171). Respiration (172). Sensations (172). Ner- 
vous system (172). Reproduction (173). Economic impor- 
tance (173). Segmentation (174). Body cavity (1 74) . 
Leeches (175). Fresh-water segmented worms (176). Marine 
segmented worms (176). Characteristics and classification 
of the Annelida (177). 

CHAPTER XX 

The Roundworms . . . . . . . . .178 

"Horsehair snakes" (178). Intestinal parasites (178). 
Trichina (179)- Hookworm (179). Elephantiasis (181). 
Other roundworms (181). Characteristics and classification 
(182). 

CHAPTER XXI 

The Flatworms 183 

Planaria (183). Parasitic flatworms (185). The liver 
fluke (186). The tapeworm (188). Characteristics and 
classification (191). 

CHAPTER XXII 
The Echinoderms ......... 192 

Symmetry (192). Starfishes (193)- Brittlestars (195) 
Sea urchins (196). Sea cucumbers (196). Sea lilies (197). 

CHAPTER XXIII 

The Ccelenterates . 198 

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 211 

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 toman (215). Characteristics and classifica- 
tions (217)- 



Xll TABLE OF CONTENTS 

CHAPTER XXV 

PAGE 

The Protozoa . . . . . . . . . .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 ..... 245 
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 (269J. Internal organs (269). Devel- 
opment (269). Other cyclostomes (270). The brook lam- 
prey (270). 

CHAPTER XXIX 
The Structure and Activities of Fishes .... 271 
Habitat (272). Form of body (272). Locomotion (272). 
Protection (273). Sensations (274). Respiration (275). 
Reproduction (275). 



TABLE OF CONTENTS xm 

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 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 XXXIII 

The Reptilia 3°9 

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 

PAGE 

(354). Precocial and altxicial birds (357)- Birds' eggs (358). 
Incubation (358). Growth of the young (359). 

CHAPTER XXXV 
Some Common Birds of North America .... 361 
Ancient birds (361 ). Flightless birds (363). Water birds 
(364). Land birds (369). 

CHAPTER XXXVI 

The Relations of Birds to Man 376 

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

CHAPTER XXXVII 
Bird Protection ......... 382 

1. The Destruction of Birds (383 ). The destruction of 
birds by man (383). Cats (387). Squirrels (388). Rats and 
mice(388). Ha\vks(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 . . . 398 
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 ....... 419 

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



TABLE OF CONTENTS XV 

PAGE 

(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 ..... 450 
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 . . 461 
The need of protection (461). Protective measures (464). 
The propagation of wild life (465). 



CHAPTER XLII 
The Conservation of Our Natural Resources . . . 469 

CHAPTER XLIII 

The Progress of Zoology 47 2 

Index 482 



PRACTICAL ZOOLOGY 

CHAPTER I 
WHERE ANIMALS LIVE 

If 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 
satisfying 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 aeroplane. 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 terrestrial 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 aerial has been applied. The 
most notable aerial 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. 

Subkingdom 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, Polyps, 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. — Clams, Snails. 60,000. 
Phylum 9. Arthropoda. — Crabs, Insects, Spiders. 

400,000. 
Subkingdom II. Vertebrata. — Animals with backbones. 

30,000. 
Phylum 10. Vertebrata. — Fishes, Amphibians, Reptiles, 

Birds, 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 

The Habits, Physiology, Anatomy, and Economic 
Relations of a Typical Insect 

About 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 such a 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 



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. — Wings. — 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 




Fig. 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. i). 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. 

Flying. — 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. 

Legs. — 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, b) ; others are flattened out and bordered with 
bristles, making them effective swimming organs (c) ; some are 
short and shovel-shaped for digging in the earth (d) ; a few enable 



THE GRASSHOPPER 



II 



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 : (i) 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 
really represents three 
that are fused together. 
If the undersurface of 
this segment is ex- 
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 lies beneath the claws. Of particu- 
lar interest are the two hind legs of the grasshopper, since these 




Fig. 



Legs of insects showing relation be- 
tween structure and function. 

a, grasping leg of praying-mantis ; b, running 
leg of a beetle ; c, leaping leg of a grasshopper : 
d, digging leg of mole-cricket ; c, swimming leg 
of beetle. (After Sedgwick.) 



12 



PRACTICAL ZOOLOGY 




5 .S -3" 



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, 
lb) and lower lip or labium (Fig. 3, lab). 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 maxillae (Fig. 3, mx) which 
are made up of several pieces and serve principally to hold the 
food between the mandibles. Both the labium and maxillae 
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 oesophagus 
(Fig. 3, ce), into a large thin-walled portion, the crop (Fig. $,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, vent), 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, red). 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, an). 

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 
blood is a fluid containing 
corpuscles. These corpus- 
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 




Fig. 4. — Diagram of an insect show- 
ing the heart (h), aorta (a), and direction 
of the blood-flow (by arrows). (After 
Kolbe.) 



THE GRASSHOPPER 15 

is no complex arrangement of tubes, as in human beings. Near 
the upper part of the body is a rather long contractile tube 
called the heart (Fig. 3, hi), 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 Blood. — 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 tracheae, 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 air is 
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 



1 6 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 
antennae, 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 result in 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 oesophagus 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, Isg, psg, sgn) con- 



1 8 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 




Fig. 



-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 



19 



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 as a 
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 





Fig. 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 (Aptera) 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 larvae, grow in size for a time, and then enter a 
stage of rest, when they are spoken of as pupa?. During the 
pupal stage the adult insect develops within the pupal covering 
and finally breaks out fully formed. The larva; of butterflies 
and moths are called caterpillars; those of beetles, grubs; and 
those of flies, maggots. The pupae 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 



21 



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 atinter- 





FiG. 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 




Fig. 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. 




Fro. p. — 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 water in a tumbler. 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 
damsel flies, possess filamentous or leaf-like 
projections called tracheal gills, by means 
of which the air mixed with water is collected in the air tubes 
and then carried throughout the body. 

Securing Food. — Mouth 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 




Fig. 10. — Young of 
may fly showing 
tracheal gills (k). 
(After Sedgwick.) 



26 



PRACTICAL ZOOLOGY 



parts of the mosquito (Fig. n, 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 oesophagus. In some suck- 
ing insects there is a special 
reservoir, called a sucking stomach 






V'l iff 



Fig. ii. — A, mouth parts of a mosquito. 

II, hypopharynx ; Lb, lower lip ; Lbr, upper lip ; Md, mandible ; Mx, maxilla. 
(After Becker.) 

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

(Fig. ii, 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 maxillae are very long, forming a 
tubelike proboscis (Fig. n, B, Mx) which is coiled beneath 
when not in use, and the jaws arc extremely small or 
entirely absent. 



SOME INSECT ADAPTATIONS 



27 




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

Legs. — 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 
(//) 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 (?> 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 antenna comb. 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 (eb 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. 




Fig. 13. — A, Kallima, the leaf-butterfly, flying; a, at rest. 

B, Siderone, another leaf-butterfly, flying ; b, 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 



3° 



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. 

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 




Fig. 14. — A walking 
stick. (From Davenport.) 



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 wav 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 
S 100,000,000. The common schools of the countrv cost in 190:2 
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 moie 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 in 

32 



INSECTS INJURIOUS TO VEGETATION 



33 




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 A 

country. 1 

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 like number, apple trees and 




Fig. 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. 
— We often read 
in the daily 
papers or in gov- 

Entomology with reference to its biological and economic as- 



Fig. 16. — The chinch bug: A, adult ; B, nymph; 
C, eggs (enlarged) ; D, beak through which the bug 
sucks its food. (After Riley.) 



iFolsom, J. W., 
pects. 

D 



34 



PRACTICAL ZOOLOGY 




17. — Chinch bugs 
1 plant. (Photo 



O'Ka 

eggs 



eminent 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. 

Methods of Control. — 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 



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. 
i8,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 




Fir,. 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. 




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



The larva: 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 



pupa;, 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. 

Cabbage 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 

1S60, when it first 
appeared near 
Quebec, Canada. 
By 1S6S 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. 
The larva; (Fig. 20, 
C) are velvety green 
in color and resemble the foliage so closely as to be hardly 
distinguishable from it. When full-grown thev are about one 
and one fourth inches long. Spraying or dusting with Paris 
green will kill the larva;, 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 




Fig. 



butterfly : A, adult ; 
D, pupa or chrysalis. 



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. 2i, 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 
insects must be made by 
the horticulturists, for no 
other vegetation seems so 
liable to attack as the 
fruit trees and the fruit they bear. The San Jose scale 
insect (Fig. 22) is perhaps the most important of all fruit- 
tree pests. It appeared in 1880 near San Jose, 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- 




Fig. 21. — Insects injurious to garden 
vegetables: A, pea weevil; B, cucumber 
beetle ; C, squash bug ; D, celery caterpillar, 
the larva of the black swallow-tail butterfly. 
(After various authors.) 



40 



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 




Fig. 22. — San Jose 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. 




Fig. 23. — A stable made by ants for plant lice or aphids. (From Cornell 

Leaflet.) 



Plant 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 



PRACTICAL ZOOLOGY 



aphids arc 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. 

Codling Moth. 
— There is one 
fruit enemy with 
which every one 
is acquainted, the 
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 larva? 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- 




Fic 24. — Codling moth 
apple ; c, pupa or chrysali 
283, U. S. Dept. Agric.) 



a, adult ; b. larva in 
(From Farmers' Bui. 



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. 




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

Tussock Moth. — The white-spotted tussock moth is very 
common in various parts of the country. The caterpillar (Fig. 
25, C) is a 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 






A, female ; B, larva 
(After Howard.) 



C, pupa between leaves. 



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

Gypsy Moth. — 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 
i86y, 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. The adults 
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 




Fig. 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. 

Leopard Moth. — 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 
larva? 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 larva;, 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. 

Methods or 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 larva? 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. 1 

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. 

'Howard, L. O., Circular is, 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 

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. 1 
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 botflies, 
fleas, lice, and ticks. Man, as well as the lower animals, is 
attacked by them. 

1 Osborn, H., Insects Affecting Domestic Animals. 
48 




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



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 




Fig. 29. 



- Larva; (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 larvae 
which hatch from them (Fig. 28, B) fasten themselves by means 

E 






5° 



PRACTICAL ZOOLOGY 




of rows of hooklets to the lining of the stomach (Fig. 20). As a 
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 larvae 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 eggs of 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 
mucus. They are 
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 larvae 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 




Fig. 30. — Ox botfly or heel fly: A, adult; B, 
eggs attached to hair; C, larva or grub; D, grub 
just beneath air-hole in skin of an ox. (After 
Ransom.) 



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 larvae (Fig. 30, 
C) act very differently, however. They bore their way through 
the walls of the oesophagus 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 



5- 



PRACTICAL ZOOLOGY 



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

The jigger flea, 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 




Fig. 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 thev 
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 larvae 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 




Fig. 32. — Cat and dog flea: A, adult; B, Egg; 

Howard.) 



C, larva in cocoon. (After 



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. 

Lice. — A fourth group of degen- 
erate parasitic insects is made up of 
the sucking lice. These also are 
wingless. They possess mouth parts 
adapted for sucking blood from the 
Fig. 33. — Sheep tick. En- poultry, cattle, sheep, and other 

larged and I natural size (in small d tic ammals which the y para- 

circle). (Photo by O Kane.) - " 

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 



55 



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 






A, chicken louse ; 



— Four different kinds of lice, 
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., X. 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." ' 




Fig. 35. 
A, silver fish or fish moth ; 



— Insects of the household. 
B, cockroach ; C, red ant. 
and Riley.) 



(After Sedgwick 



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 

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



INSECTS OF THE HOUSEHOLD 



59 



large black ants are simply visitors from 
casionally in search of food. The little 
however, lives in large nests or colonies in 
floors. If the nests can be found, they 
otherwise the ants must be trapped with 
sponges containing sweetened water; the 
into boiling water and then " set " again, 
ing method has been used in California to 



outside that enter oc- 
red ant (Fig. 35, C), 
the walls or under the 
should be destroyed, 
pieces of meat or with 
latter can be dropped 
Recently an interest- 
destroy the Argentine 




Fig. 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 larvae 
are maggots. Thorough cleaning, followed by fumigation, will 
destroy these insects. 



6o 



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, larvae, 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 larva:, which are oval, hairy-coated, and about 
one fourth of an inch long (Fig. 37, B), feed on the wool in carpets, 




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 larva? (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 6 1 

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. 






Fig. .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. 




Fig. 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 



6 4 



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 





Fig. 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 larva?. Bees swarm in 
early summer, when the hive 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 




Fig. 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 



66 



PRACTICAL ZOOLOGY 




Fig. 42. — Types of insect galls. 

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



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, Linnaeus, 
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- 
bseus 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. 




Fig. 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 (0) 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- 




Fig. 44. — A, fig insect whose introduction has made Smyrna tig culture possible 

in California. (After Westwood.) 

B, plum blossom; 0, ovary; p, petal; se, sepal; sta, stamen; si, 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, 
and man indirectly 
with larger and better 
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 1900 this fig could not be 




Fig. 45. — Predaceous insects. 
A, tiger beetle ; B, European ground beetle im- 
ported to prey upon the gypsy and brown-tail 
moths. (After Bruner and Howard.) 



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 
of cases, feed upon 
other insects, and 
since as a general rule 
insects are injurious, 
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 




Fig. 46. — Australian ladybird beetle and fluted 
scale, 
a, larva; of beetle feeding on scale ; b, pupa of 
beetle ; c, adult beetle ; d, orange twig showing 
scales and beetles. (After Marlott.) 



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. 





Fig. 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 XXV.) 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 ^niou to about 
j-^5- 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 various industries, 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. 





i 




D 

Fig, 48. — Disease germs — bacteria. 

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 109. 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- 



jrtSt 




Fig. 40. — 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. 






7 6 



PRACTICAL ZOOLOGY 



How Germs are Carried. — 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 legs, 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 




Fig. 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 line 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 II y 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 (Fig. 51a). 




Fig. si a. — Plate of 



gelatine, showing colonies of bacteria in footprints of 
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 T15 wo 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. 1 

Dysentery. — Similar in some respects to the typhoid bacillus 
is the bacterium that causes summer diarrhcea or dysentery in 
children. The germ (Bacillus dysenteria) 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 diarrhcea 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. 

1 Hewitt, C, G., House-Flies 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. 1 

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. 



So 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, characterised 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 ma}- 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 J z of an inch long. Within 
twenty-four hours the eggs hatch and the maggots that emerge 
(Fig- Sib, 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 b, B). About four days later the adult fly 
emerges from the pupal covering (Fig. 51 b, C). These adults are 
ready to lay eggs in about two weeks, so that the life cycle from 
egg to e gg lasts a little over three weeks. During the summer, 



THE HOUSE FLY AND DISEASE 8 1 

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 phcebes, are known to catch them; predaceous insects, like 




Fig. 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 muscce) kills enormous numbers of 
them; it is, 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- 



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 
the manure, when accessible to flies, 





^iiiii 



Fig. 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 is safe 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. 1 

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 i and October 31, and at least once every week between 
November 1 and May 3 1 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. 

'Hewitt, C. G., House-Flics 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 the}'- 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. n, 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 XXV.) 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. 




Fig. 53. — A, position of malaria mosquito (Anopheles) when at rest. 

B, position of common house mosquito (Culex) when at rest. (After Howard.) 



The Malarial Mosquito 

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 




Fig. 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 Protozoon named 
Plasmodium vivax and causes " chills and fever " every third 
day. (2) Quartan fever is due to Plasmodium malaria; it 
causes " chills and fever " every fourth day. (3) Pernicious, 
tropical, or a j stivo-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 moscjuitoes are more common than A nopheles mosquitoes 




Fig. 55. — Pupa of house mosquito Fig. 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), 
larva; (Fig. 54, A and B), pupa; (Fig. 55), and adults differ also 
in various 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 
larvae, 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 larvae 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 larvae change to pupa; (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 larvae and pupae 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 



91 



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 




Fig. 57. 



Oiling 



a pond near a railroad track where mosquitoes breed. 
(After Herms.) 



larvae 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 (larvae and pupae). Many different substances have been 



92 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 larvae 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 People of the United Slates 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 1 90 1 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 
larvae and pupae 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 from a 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. 1 

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.' 

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 400 containing larvae 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 
larvas 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 

98 



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. 




Fig. 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 



IOO 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 
37V0 °f 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 18S1 is employed for cattle and sheep in 
infected districts with good results. In France alone, between 
the years 1882 and 1007, 8,000,000 sheep and 1,300,000 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, beetles, 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 (i) 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, aerial, 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 
larvae 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 
Linnaeus (1707-1778). He divided the animal kingdom into a 



104 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. 

Horse 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, Eqaus 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 Eqtndce. 

This family and several others, including the family TapiridcB, 
which contains the tapirs, and the family Rhinocerotidm, which 
contains the rhinoceroses, belong to the order Pcrissodactyla. 
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 Rodcntia 
(gnawing animals, like the rabbit and mouse), the order Carniv- 
ora (flesh-eating animals, such as the cat and dog), the order 



CLASSIFICATION 105 

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 
vertebra, 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- 
idce. The Hominida 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 Linnasus. 

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 
calif ornianus , 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 
antenna?, three pairs of legs, and usually wings. The crayfish is 
not an insect, for it has two pairs of antennae, five pairs of legs, 
and no wings. The spiders are not insects since they have four 
pairs of legs and no antennae, 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 body 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 i. Aptera. — 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 antenna;, (5) grasshoppers with long antenna; 
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, etc. 

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. Lepidoptera. — 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 109 

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 antennae; 
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. Diptera. — 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 



HO PRACTICAL ZOOLOGY 

is a bug, but only those belonging to the order Hemiptera 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 Jackson. — 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 : — 

i. 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 



Ill 



PRACTICAL ZOOLOGY 




Fig. sy. — 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 5q, 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 

22 




Fig. 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, ca:cal 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. 6i, 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 a thread. 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 piir of appendages, the chelicerae (Fig. 60, ig). 
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 trachea? similar to those of insects (see p. 15), 
but in addition they possess book lungs which are present only 
in spiders. 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 



US 




it 



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. 

Aerial Spiders. — 
On sunny days in au- 
tumn large numbers 
of fine threads, the 
so-called gossamer 
threads, may be seen 
floating about over 
fields and meadows. 
On some of these threads, 
find a small (young) spider 
creature's own construction, 




Fig. 6i. — Parts of a spider's body. 

A, ventral view of posterior end of abdomen 
showing three pairs of spinnerets (is, m.s., and s.s.). 

B, foot showing claws and bristles. 

C, front of head showing eyes (2) and jaws (3 
and 4). 

D, a thread from a spider's web. (After Warbur- 
ton.) 



if we examine them, we shall 
This aerial vehicle is of the 
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 






n6 



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 aerial journey begins. Perchance the little ship will be 
stranded — agreeably to the wish of its navigator — in some spot 




Fig. 62. — A, crab-spider; B, jumping-spider ; C, young spider preparing for an 
aerial 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 ARACHNIDS 



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 





Fig. 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 top of 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. 



uS 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 




Fig. 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 chelicerae, 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 



119 



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- 





acu/eus. )/ "vesicle 

Fig. 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: (i) they have no an- 
tennae; (2) there are no true jaws; (3) the first pair of append- 
ages are nippers, termed cheliceras; and (4) the body can usu- 





Fig. 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 bigeminiim, from sick cattle 
to healthy cattle in the South. How serious this disease is may 



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 18S9. 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 




Fig. 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 ^V of an 
inch long and have only three pairs of legs. When cattle brush 



THE RELATIONS OF ARACHNIDS TO MAN 



F/ELD No. 2 


F/ELD No. 3 


F/ELD No. <Z 


CORA/, 

COWPEAS. 


COTTON 
FOLLOWED BY 
CRIMSON CLOVER, VETCH 
BUR CLOVER OR RYE. 


OATS, 

COWREAS, 
BERMUDA, 
BUR CLOVER. 






•^ 






WHEN FEED BECOMES 

SHORT ptOVE THE HERD 

FROM THIS F/ELD TO 

FIELD No. 3 


FEBR. IS, 
MOVE THE HERD TO 
FIELD No. •? 


BECOMES THE MEW 
PASTURE. 








W//> 








vM 


) 


\ 


HOUSE 






F/ELD A/o. / 




PASTURE. 


OCT. 16 


", MOVE HERD TO FIELD No. S 


PLANT IN O/ 


ITS AND FOLLOW W/TH COW PEAS. 



Fig. 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 




Fig. 60. — Arachnida parasitic on domestic animals. 
A, chicken mite; B, fowl tick ; C, scab mite. (After Salmon.) 



-J ¥ 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 -3- 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 




Fig. 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 
supposed to be 
caused by a minute 
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 



Arachnida parasitic on man. 



A, harvest mite or chigger ; B, itch mite; C, fol- 
licle mite. (From Sedgwick.) 



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 sub-cylindrical, 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 




Fig. 72. — A millipede. (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 maxillae. One pair of antenna; and either simple or aggre- 
gated eyes are usually present. The breathing tubes (tracheae) 
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 
ol 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. 




Fig. 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) tracheae, 
(4) excretory organs (malpighian tubules) opening into the in- 
testine. 

The two principal orders are as follows: — 

Order 1. Diplopoda. — Millipedes. 

Order 2. Chilopoda. — 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 differ 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 



131 



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. 



Cefihalothorax 
Carapace ____ , Rostrum 



AntennulG 




Walking leqs 

Fig. 74. — External anatomy of a lobster. (After Caiman.) 

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. 

Color. — 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." 



132 



PRACTICAL ZOOLOGY 







Sensitiveness to Surroundings. — Crayfishes are made aware 
of the state of their surroundings by their sense organs. When 
they are hiding, the antennae are usually protruded and waved 
back and forth. There are two pairs of these organs; the first 



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 larvae, 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, g), 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 cephalo thorax, 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, 10 and 11) 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 oesophagus '(Fig. 75, 20) into the stomach 
(Fig. 75, 21). 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, 2Q) 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 
branchiae 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 
maxilla:. 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 a period 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. 




Fig. 76. 



Cotton field damaged by crayfishes after three plantings. 
Fisher.) 



(After 



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 




jr IG . 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 



i.tf 



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, 
Branchi pus . 




Fig. 78. — Photograph of hermit crab in snail shell. (From Caiman.) 



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 




Fig. 70. — 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 




Fig. 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. Si, 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 antennae are protruded 
and moved, serving as swimming organs. 

Antenna; are also used as swimming organs by Cyclops (Fig. 
8 1, 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 



141 



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. 






Fig. 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 antenna; (feelers) , one pair of mandibles (jaws), 
and two pairs of maxilla?. 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. Malacostraca. — Pill Bugs, Sow Bugs, Beech 
Fleas, Shrimps, Crayfish, Lobsters, and Crabs. 

REFERENCES 

The Life of Crustacea, by W. T. Caiman. — 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. Flegner. — 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 




Fig. 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 shells is 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 




Fig. S3. — The external parts of a mussel, 
is the inner face of an empty shell 



Behind 



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. 
(From Shipley and MacBride.) 



water, it will not at 
first show any signs 
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, g). 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 



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 





HI "N ? , W ?S^ JJm ' ~ *^SP 




vg 



Pg 
Fig. 



■ Internal organs of a mussel. 



brain ; 

gill; 



a, anus; aa, anterior aorta; aam, anterior adductor muscle; b, 
ds, dorsal siphon ; ec, excretory canal ; ep, excretory pore ; f, foot ; 
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 



PRACTfCAL 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, 10) and in some species fit 
together by means of toothlike pro- 
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 
anterior, the other near the posterior 
edge of the shell (Fig. 84, aam, pain). 
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). The mantle cavity 
communicates with the water surrounding the mussel by means 
of two tubes or siphons, one above the other, formed by the 




Fig 



section of 



1, right auricle; 2, epi- 
branchial chamber; 3. ven- 
tricle ; 4, vena cava ; 5, non- 
glandular part of kidney; 6, 



glandular part of 
7, intestine in foot 
cardium ; 9, shell ; 
me n t o f shel 1. 
Howes.) 



kidney ; 
8, peri- 
10, liga- 

(After 



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 



150 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, b). 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, Ip). The cilia 
covering these palps drive food particles into the mouth and 
down the oesophagus. 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 oesophagus into the saclike stomach (Fig. 84, s), where it 
is acted upon by digestive juices from the liver (Fig. 84, I). 
That part not absorbed by the walls of the stomach enters the 
intestine (Fig. 84, i) 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. If a 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, sti) 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 setoe (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 







Fig. 86. — A. A young mussel or glochidium. ad, adductor muscle; by, 
byssus; s, setas ; 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 Ostrea 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 archaeological 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 larvae 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 
larvae 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 




Fig. 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 




Fie. 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. jacobins), 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) in the 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 
them to reach their 
food which is, of 
course, abundant 
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. 




: ^^MMm^m0^' 



Fig. 



Diagram showing the structure of a snail. 



A., anus; At., respiratory aperture, the entrance to 
mantle cavity indicated by arrow; D., intestine ; 
F., foot; Fii., tentacles; Ko., head; M., mouth; Mh., 
mantle cavity ; Mt., mantle ; R.Mt, free edge of 
mantle; Sch., shell. (From Schmeil.) 



i6o 



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, FiL); the 
upper, longer tentacles bear each an eye. These eyes, however, 
are probably not organs of sight, but simply serve to distinguish 
between lights of different intensities, or since snails are active 



« B 




9 if k 1 

Fig. 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, oesophagus; 11, opening to salivary gland ; 12, fold behind radular pocket. 
(From Lang. J 



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, j) 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, Mh.). Air is 




Fig. 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, Umax maximua, are a nuisance in green- 
houses because of their attacks on plants. 



l62 



PRACTICAL ZOOLOGY 



Fresh-water Snails. — The land snails 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 









Fig. 92. — Shells of common snails. 

A, helicodiscus ; B, planorbis ; C, polygyra ; D, physa ; E, pleurocera ; 
F, goniobasis ; G, lymniea. (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, Lymnoea, 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. Lymnaa (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. 







B D 

Fig. Qi. — 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 Lymncea 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- 





fVnfjj ^ 



A, the squid. 

B, the octopus 



A, 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 




Fig. 



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 



1 66 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 debris. 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. Gastropoda. — 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 MacmiUan Co., N. Y. City. 
See references to Chapter XVII. 



CHAPTER XIX 

THE EARTHWORM AND OTHER SEGMENTED 
WORMS 

Or all the animals that are called worms only a few are true 
worms; most of them are the larvae of insects. The true worms 
are divided into three phyla : (i) 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 Platyhdminthes, 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, bw). An examination of a 

168 



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. mm) running around the body just beneath the 
skin, and a layer of longitudinal muscles {long, mus) underneath 
the circular ones. It is evident that when the circular muscles 
near the anterior end contract, the body becomes thinner and 




nc : ! bw 

lnv Inv 

Fig. 06. — Diagram of the internal anatomy of the earthworm. 

bw, body wall ; dv, dorsal vessel ; i, intestine ; iw, intestinal wall ; lnv, 
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 



170 



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* 



neph 




n.co 



Fig. q7. ■ 



coel 
rent, v 
sub.n.vess 

Diagram of a cross section of an earthworm. 



circ.mus, circular muscle libers; coel, caslom ; 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, seta?; sub.n.vess, subneural vessel; typh, typhlosole ; vent.v, 
ventral vessel. (From Marshall and Hurst.) 

sharp bristles, the setae, which extend obliquely backward from 
the sides and under part of the body (Fig. 97, set). There are 
four pairs of these seta? 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 arc of special serv- 



THE EARTHWORM AND OTHER SEGMENTED WORMS 171 

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 oesophagus, 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 the food. Next it enters 
the intestine, where the digestion and absorption chiefly take 
place (Fig. 96, i). 

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, w, pv, Inv, snv). Waste products pass 
into the blood as it circulates and are excreted by organs 
called nephridia (Fig. 96, n). 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, nc) 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 
various 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 
great is the economic impor- 
tance of earthworms . One acre 
of ground may contain over 
fifty thousand earthworms. 
The feces of these worms are 
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 




Section through the upper 
held showing the work of 



Fig. 98. — 
stratum of < 
earthworms. 

A and B, arable soil thrown up by 
earthworms; C, marl and cinders buried 
by worm castings ; D, subsoil not dis- 
turbed by the earthworms. (From 
Schmeil.) 



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 vertebra;. 

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 
ccelom. 

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 
pharynx. 

The medicinal leech, Hirudo medic inalis 
(Fig. 99), is only four inches long, but it 
is capable of great contractions and elon- 
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. 




Fig. 99. 



— The medicinal 
leech. 

1, mouth; 2, posterior 
sucker; 3, sensory papilla?. 
(From Shipley and Mac- 
Bride.) 



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. 100, 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 
on each segment. It 
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 



w 

m 




Fig. 100. -- A, a fresh-water worm, Nais. 
B, a marine worm, Nereis. (After Oersted.) 



THE EARTHWORM AND OTHER SEGMENTED WORMS 177 

Chatopoda 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. Setae are usually present. 

Most of the annelids belong to the two following classes : — 

Class 1. Chatopoda. — Annelids with setae. This class 
may be subdivided into two subclasses: (1) the Polychata, like 
Nereis (Fig. 100, B), with many setae and fleshy outgrowths, the 
parapodia, and (2) the Oligochczta, like the earthworm, with few 
setae and no parapodia. 

Class 2. Hirudinea. — Leeches. Annelids without setae 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 



7.- 



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. 



Fig. ioi. — 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.) 



i So 



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 
larvae 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, 




Fig. 102. — Trichina. A, Larva?, 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 anaemic, and also subject 
to tuberculosis because of the injury to the lungs. It is 



THE ROUNDWORMS 18 1 

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 batt- 
er of ti, a parasite in the blood of man. The larvae of this species 
are about j^ 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 larvae with the blood of the infected 
person. The larvae 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 40 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 A scar is 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- 




Fig. 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. IT. — 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 

Fig. 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, /), 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). 

183 



184 



PRACTICAL ZOOLOGY 



Because of the great amount of coloring matter in its body the 
internal organs are difficult to make out. 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, j) ; this facilitates 
the capture of food. The food 
is digested in the intestinal 
trunks (Fig. 105, i h /■>, h) 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, en), and two 
lateral longitudinal nerve cords 
{In), connected by transverse 
nerves. From the brain, nerves pass to various parts of the 
anterior end of the body, imparting to this region a highly 




atworm. 



en, brain ; e, eye ; g, ovary ; ii, i 2 , i3, 
branches of intestine; In, lateral 
nerve ; m, mouth ; od, oviduct ; ph, 
pharynx; t, testis; u, uterus; v, yolk 
glands; vd, vas deferens; d", penis; 
?, vagina; cf ? , common genital pore. 
(After V. Graff.) 



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 easilyTn figure 105T 

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 1 ), while the 
posterior part de- 
velops a new head 
(C, C 1 ). A cross- 
piece (D) will gen- 
erate both a head 
at the anterior end, 
and a new tail at 
the posterior end 
(D-D 4 ). The head 
alone of a plana- 
rian will grow into 
an entire animal 
(E-E 3 ). Pieces cut 
from various parts 
of the body will 
also regenerate 
completely. No 
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 five. 

Parasitic Flatworms. — Besides Planaria and other free- 
living flatworms that belong to the class Turbellaria, there are 
two classes of parasitic flatworms, the Tr'ematoda or flukes and 
the Cestoda or tapeworms. 




Regeneration of planaria. 



A, normal worm ; B, B 1 , regeneration of anterior 
half ; C, C 1 , regeneration of posterior half ; D, cross- 
piece of worm ; D 1 , D 2 , D 3 , D 4 , regeneration of same ; 
E, old head ; E 1 , E 2 , E 3 , regeneration of same ; F, F>, 
regeneration of new head on posterior end of old head. 
(From Morgan.) 



i86 



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., 

and is occasionally found in man. 
Figure 107 shows the shape and 
most of the anatomical features 
of a mature worm. The mouth 
(0) 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 
the sheep's body with the feces. 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- 




Fig. 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 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 






-c 




Fig. 108. — Stages in the life-history of the liver fluke. 

a, miracidium (ciliated embryo) ; b, sporocyst containing rediae (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 redias soon break through the wall of 
the sporocyst and by means of germ cells (Fig. 108, c, K) usu- 
ally give rise to one or more generations of daughter rediae (Fig. 
108, c, R), after which they produce a third kind of larva known 
as a cercaria (Fig. 108, c, C). The cercariae (Fig. 108, d) leave 
the body of the snail, swim about in the water for a time, and 



PRACTICAL ZOOLOGY 



then encyst on a leaf or blade of grass. If the leaf or grass is 
eaten by a sheep, the cercarias 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 larva? do not find 
the particular kind of snail, and the 
cercariae to which the successful larvae 
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, Tania 
solium, is a common 
parasite which lives as 
an adult in the alimen- 
tary canal of man. A 
nearly related species, 
Fig. ioq. — A, tapeworm. The lengths of parts Tania saginata, is also 

omitted in the 6gure are indicated. a parasite of man. 

B, head or scolex of tapeworm. (From Shipley 

and MacBride.) lama, 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. 109, B, 2) and suckers (j) on 
the scolex. Behind the scolex is a short neck (4) followed by a 





THE FLATWORMS 



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 excret 




v&s.def 



nerul- 



por.gen: 

o'v glvit scMd ou 

Fig. 1 10. — A proglottid of a tapeworm. 

can.excret, longitudinal excretory canals with transverse connecting vessels; 
gl.vit, vitelline or yolk-glands; nerv.l, 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 no. 

The eggs of Tania solium develop into six-hooked embryos 
(Fig. in, a) while still within the proglottis. If they are then 
eaten 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- 



190 



PRACTICAL ZOOLOGY 



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 larvae are more dangerous. For example, the larva; 

of the tapeworm, Tama echinococcus (Fig. 112, A), which lives 




Fig. hi. — 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.) 




Fig. 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, Tania ccenurus. 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. Trematoda. — Parasitic animals like the liver 
fluke. 

Class 3. Cestoda. — 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 

The Echinodcrmata 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 right 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 




Fig. 113. — A, the oral surface of a starfish. 

B, a spine bearing three pedicellaria:. 

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. 



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 

1 '■''■'' 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 
stomach inside out. The 
everted edge of the stomach 
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. 



Fig. 114. — Diagram of starfish eating 
a mussel. (From Cambridge Natural 
History.) 



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. 




Fig. 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. 




Fig. 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 freight, 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 " beche de mer " or " trepang " and are used for food. The 
trade mounts into hundreds of thousands of dollars annually. 



''MS 

A ■■■> 
- -JjA 


lv<£c MmmSI X\\JMffi"'' '"'\ ^Sr 




it • '*.,«■ '. * • • . ' ' • 


mB 




^pr 



Fig. 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., N. Y. 
City. 



CHAPTER XXIII 

THE CCELENTERATES 

The animals known as corals, jellyfishes, polyps, sea anem- 
ones, sea fans, sea pens, and hydroids belong to the phylum 
Cmlenterata. They are all radially symmetrical, like the echi- 




FlG. 



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). 



THE CCELENTERATES 



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. 




Fig. 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 T hypostome ; m, mouth; m.e, 
mature egg ; m.t, mature testis ; n, 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 



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 
(/). Both the body and tentacles vary at different times in 
length and thickness. One or more buds (b) are often found 
extending out from the body, and in September and October 
reproductive organs may also appear. The male organs (testes, 
Fig. 119, y.l) 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. 

Habitat. — 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, n ; 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. If a 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 



20I 



trate the skin of other animals (Fig. 120, B, C, D). The explo- 
sion is probably due to internal pressure, and may be brought 




Fig. 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 of Labor among 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 cell 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. 

The Ectoderm of Hydra. — 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 Hydra. — The entoderm, the inner layer 
of cells, is primarily digestive, absorptive, and secretory. The 



THE CCELENTERATES 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.l) and escape into the surrounding water. The eggs arise in 
the ovary (Fig. 119, y.e) and usually only one egg develops in 
a single ovary. 

The egg (Fig. 119, m.e) 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 I, 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 coordinate properly. 

Division of Labor among Individuals of a Colony. — When- 
ever animals live together in colonies, there is almost certain to 



THE CCELENTERATES 



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- 
productive zooids; and still others 
give rise to egg-producing medusae. 

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 a central 
stem. These hydroids are of particular biological interest 
because of their method of reproduction. Reference to Figure 




Fig. 121. — The Portuguese 
man-of-war, a colonial ccelen- 
terate. (After Agassiz.) 



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- 






Fig. 122. — A, part of a colonial ccelcnterate. 1, ectoderm; 2, entoderm; 
3, mouth; 4, ccelenteron; 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 CCELENTERATES 



207 



colony and swim away as jellyfish or medusae. The medusa? 
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 
medusae, which give rise to germ cells and thus constitute the 
sexual generation. 

Jellyfish. — Some jellyfishes or medusae belong to the 
class Hydrozoa along with Hydra and the hydroids just de- 




Fig. 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. Medusae 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 Ccelenierata. Coral polyps live in colonies, and 
each member of the colony builds for itself a sort of skeleton 




Fig. i: 



■ 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 CCELENTERATES 



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 





Fig. 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. 



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 
role in protecting the shore from being worn down by the waves. 
They have also built up thick strata of the earth's crust. 




Fig. 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 gastro vascular cavity, and are provided with 
stinging cells, the nematocysts. 

The three classes of ccelenterates are as follows: — 

Class 1. Hydrozoa. — Fresh-water Polyps, Hydroid Zo- 
ophytes, many small Medusa? 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 

The 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 (esc). 
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 



212 



PRACTICAL ZOOLOGY 



and carbon dioxide and other excretory substances are given 
off by it. 




Fig. 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. 
Gcmmidcs (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 





? VZc. 



PC 

JLlj° 




Fig. 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 ; fl.p, 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. 

M 




Fig. i2g. 
A, spicules ; B, spongin ; C, 



— Parts of the bodies of sponges. 

a reproductive body or ge'mmule ; 
(After various authors.) 



D, collar cells. 



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 (In) into chambers 
lined with flagellated cells ( C) , and from here through excurrent 
canals (Ex) into the gastral cavity (PG) and out through the 
osculum (O). 



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, 




Fig. 130. — Looking for sponges through a glass-bottom pail. (From Bui. 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 



2l6 



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 




Fig. 131. — Bringing in a load of sponges. (From Bui. 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, Eu- 
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. Demospongi/E. — 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 

What we learned in Chapter IX 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, o.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 



219 



m~ 



(Fig . 1 3 2 , tr) , 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. 

Food. — The food of 
Paramecium consists prin- 
cipally of minute plants 
and animals. The cilia 
in the oral groove (Fig. 
132, o.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 (/.!)) 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. 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). 




-Fig. 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 ; o.g, oral 
groove ; p, pellicle ; tr, trichocyst layer. The 
arrows show the direction of movement of the 
food vacuoles. (From Jennings.) 



2 20 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. 

The Nucleus. — 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 grow and 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 -X 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- 



2 2 2 



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 




Fig. 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 y^ 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, /), which 
is difficult to find in living Ameba, 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. 

Food. — The food of Ameba consists of very small aquatic 
plants and animals. The ingestion or taking in of food occurs 
without the aid of a mouth. 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, 5), and then the endosarc flows into it. In this 
way the entire animal glides slowly along. There is, however, 
no permanent anterior end. 

Reproduction. — 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 Ameba 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 
down the carbon dioxide, thus setting free 
the oxygen, and to unite the carbon with 
water, forming a substance allied to starch, 
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- 
zoic. 

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 




Fig. 134. — Euglena. 

am, pyrenoid ; chr, 
chromatophores ; cv, 
contractile vacuoles; e, 
stigma, or eyespot ; m, 
mouth ; n, nucleus ; r, 
reservoir. (From 
Bourne.) 



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- 




Fig. 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 



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 




Fig. 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 Mastigamcba (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 j-J-j 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 mosquitoes 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. 

If 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 into 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. ^CIII'i P- I2I )> an d Spiroclimta 
gallinarum, which attacks poultry. " / ' 

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. 

Hydrophobia 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. Trvpanosomes 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 229 

soon follows infection, and later general debility sets in. The 
victim exhibits an increasing tendency to sleep, gradually wastes 
away, and finally dies. 

Yellow Fever. — 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. 

Spirochetes. — Spirochetes are corkscrew-shaped organ- 
isms about 2tW °f an mcn l° n g (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 Spirochceta pallidula. 

Syphilis likewise causes ulcerating sores. The organism re- 
sponsible for this disease has been known for only a few years. 
It is Spirochceta 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. 101) occurs in some 
parts of Europe. Another spirochsete, Spirochceta obermeieri, 
is the organism that causes it. 

Kala Azar or Dumdum 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 donovani. 

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 (algae), 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 23 1 

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 10 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 Carchesmm, 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. 

Volvox. — 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,* 

and 9). 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 
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 




B 

Fig. 1,37. — Colonial protozoa. 
A, uroglena ; B, volvox. (After Kollikcr.) 



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: — 

Class 1. Rhizopoda. — With pseudopodia, as in Ameba. 

Class 2. Mastigophora. — With flagella, as in Euglena. 

Class 3. Sporozoa. — Without locomotor organs in adult 
state. Produce spores, as in malarial parasite. 

Class 4. Infusoria. — 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 i. Pisces. — Fishes (Fig. 138, A and B). 

Class 2. Amphibia. — Frogs, Toads, and Salamanders (Fig. 
138, C and D). 

Class 3. Reptilia. — Lizards, Snakes, Crocrodiles, and Tur- 
tles (Fig. 138, E and F). 

Class 4. Aves. — Birds (Fig. 138, G). 

Class 5. Mammalia. — 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 




Fig. 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 oesophagus 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 tracheae 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 cravfish 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 (b) 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 Physical Basis of Life. — Protoplasm is 
known as the physical basis of life since every organism, whether 




Fig. 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 ; pi, 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. Amcba (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 Mclazoa these activities are distributed among many cells, a 
condition known as division of labor among cells or specializa- 
tion. 



AN INTRODUCTION TO THE VERTEBRATES 24 1 

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 Protoplasm. — 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). 

Kinds of 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 

(i) 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, E). 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 
preexisting 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 








Fig. 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 cell from the cerebellum of man. (From 
Dahlgren and Kepner.) 



244 PRACTICAL ZOOLOGY 

The Origin 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 preexisting 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 XXVII 
THE FROG, A TYPICAL VERTEBRATE 

Frogs 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, 
(9) muscular activity, (10) nervous activ- 
ity, (11) sense organs, (12) reproduction. 

Digestion. — The worms and insects 
used as food by the frog are captured by 
its sticky tongue (Fig. 141) and drawn into 
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. 




Fig. 141. — Diagrams 
showing the movements 
of a frog's tongue when 
an insect is captured. 
(From Cambridge Nat- 
ural History.) 



THE FROG, A TYPICAL VERTEBRATE 



247 



Food passes from the mouth through the tubelike oesophagus 
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 




Fig. 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 



24S 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 the intestinal 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 behi nd, th us 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 while corpuscles. 
The red corpuscles owe their color to the presence of haemoglobin. 
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 162 1. 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 '» »./?»// 1 4\ \ cc 

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- 
illaries. 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. 




Fig. 143. 



\ h # t- 

I 

sc 

— Diagram of the arterial system of 
the frog, ventral view. 

ao", aortic arch; au', right auricle; au", 
left auricle ; br, brachial arterj' ; c.c, carotid ; 
c.gl, carotid gland; c.il, common iliac; cce, 
cceliaco-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 ; 
lg", left lung; m, anterior mesenteric; m.i, 
posterior mesenteric ; oc, occipital ; pc , 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, Ig"), where it gets rid of carbon dioxide and re- 
ceives oxygen. Another part of the blood is carried to the 
kidneys (Fig. 143, k) 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 internal respiration of the cells. 

In the frog, respiration takes place to a considerable extent 
through the skin, 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 



2SI 



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 : — 





Oxygen 


Nitrogen 


Carbon 
Dioxide 


Water 


Inspired air .... 
Expired air .... 


20.96% 
16.02% 


79.00% 
79-°°% 


0.04% 
4-38% 


Trace 

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 haemoglobin 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. 

Excretion. — 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 ureter, 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, 
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- 
M. G M. g 




P.G 



will 



P. G 



Fig. 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 coordination 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 vertebrce 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 scapula, 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, 




Fig. 145. — Skeleton of the frog. 

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 
tibiofibula, 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 immovable, 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- 
mius bends the hind leg and extends the foot; (3) the adductor 
magnus bends the thigh ventrally ; (4) the rectus interims 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. 




add.brev, adductor brevis ; add.long, adductor longus; add. mag, adductor 
magnus ; del, deltoid ; FE, femur; gstr, gastrocnemius; hy.gl, hyoglossus; 
l.alb, linea alba; obl.int, obliquus internus ; obl.ext, obliquus externus; 
pet, pectoralis ; per, peronsus; 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.) C 2 57) 



2 5 8 



PRACTICAL ZOOLOGY 




Fig. 147. — Nervous system and sense organs in the head of the 



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, 1), 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.n), 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 nervchis 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 vertebrae. 

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 (m.f) into a reacting organ, such as a muscle (M). These 




Fig. 148. — Diagram of the spinal corrl 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; 
eg, 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 
(m.f); those leading to the spinal cord are termed sensory fibers 
(s.f). The sensory cell or receptor receives the stimulus and 
produces the nerve impulse; the motor cell, the adjuster, 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 lie 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, o.s) are supplied by the olfactory 
nerves (o.n) 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 (t). 

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 lens 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. 




A 

Fig. 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, archincphric duct; 7, cloaca; 8, orifice 
of ureter; 9, proctodeum; 10, allantoic bladder; 11, rectum; 12, kidney; 
13, testis; 14, adrenal body. 

B, female. 1, oesophagus; 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 archincphric 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 




Fig. 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. 



26 4 



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. 

Egg Laying. — 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 




Fig. 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. 

Embryology. — 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 (Fig. 150, A-D). The 
chromosomes split and one half of each is drawn to either end 



bl.coel. 



eet 



bl.cot.1 




stdm 



D E 

Fig. 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, md.f ; yk.pl, 
yolk-plug. 

C. Section of egg in stage B to show germ-layers, bl.ccel, blastoccel ; blp, 
blastopore ; ect, ectoderm ; end, entoderm ; ent, enteron ; mes, mesoderm ; 
neb., notochord; yk.pl, yolk-plug. 

D. Older embryo, br.cl, branchial arches; stdm, stomodauim; t, tail. 

E. Newly hatched tadpole, br.l, br.2, gills; e, eye; pedm, proctodeum ; 
sk, sucker; stdm, stomodaeum; t, tail. (From Parker and Haswell.) 



of the spindle (E, F, G). Each group of chromosomes then be- 
comes the center of a new nucleus (F£, 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 



2 66 



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 




Fig. 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 (eiit), 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 algae and other vegetable 
matter. The external gills grow out into long, branching tufts 
(Fig. 153, 20). 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 

The phylum Pisces which contains the fishes may be divided 
into four subclasses as follows : — 

Subclass i. Cyclostomata. — Lamprey Eels and Hagfishes. 

Subclass 2. Elasmobranchii. — Sharks and Rays. 

Subclass 3. Teleostomi. — True Fishes. 

Subclass 4. Dipnoi — 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. 13S, 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, 
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 larvae which differ in many 
respects from the adult, and were at one time considered a dis- 
tinct species of animal. The larvas 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 




Fig. 154. — The mouth of the 
lamprey eel. (From Forbes.) 



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- 




Fig. 155. — Diagram of a fish (perch) with parts named. 

a, anal fin; br, branchiostegal rays; ch, cheek; cp, caudal peduncle; dl, 
spinous dorsal fin ; 62, soft dorsal fin ; d2r, 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 ; o, 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 



272 



PRACTICAL ZOOLOGY 




Fig. 156. — Front 
view of a fish (Spanish 
mackerel). (From 
Dean.) 



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 
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 

. ' * - ° ' Fig. 157.— Diagram 

steamer by its screw (Fig. 157). The tail is showing how the tail 

made more effective by the presence of the of . a fi " h is llscd in 

... - ' . swimming. (After 

caudal lin, which offers more resistance to 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 






W 



Fig. 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 




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 an armor. 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, 

&«%^v^M$L A ) have a similar origin- 

♦13b? %o# > ^S , <ff » Color. — The colors of 

5^«$3S4S& the fish are more impor - 
<^#Ctoi#^ VK&u tant as a protection than 

iMT?*J^i(si*J*« «3^® the scales Slnce the y tend 

"^fep^^^^^D^SSf jjtP to conceal the animal 

t&flBl&^TfSNt The red > oran g e - y dlow > 
m^^M^m^M®^ and black pig ments p res - 

' ° y C. i- ent in the skin (Fig. 1 59) 

Fig. 159. — Pigment bodies in the skin of may give the fish these 
a fish. (After Cunningham.) , , . , , J 

colors or else blend to 
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. In a 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 double 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 




Fig. 160. 



Photographs of three stages in the growth of the trout. (Fron 
Bui. 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 

The 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 




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 tor- 
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) 




Fig. 162. — Sting ray. (From Jordan 
and Evermann.) 




Fig. 163. — A, sturgeon ; B, paddlefish. ; C, gar pike; D, sucker; 

E, carp. (From 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 



r--'- |M3M^ .-5. T 


^^T 


"'■*-& 


■ 




Hr 


&.' -fP^. 


*& 







Fig. 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- 



2$2 



PRACTICAL ZOOLOGY 




Fig. 165. —A, flying fish ; B, cave fish ; C, re mora ; 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 bullhead 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 
one of the head of a horse. It can cling to 
objects with its prehensile tail. The male 
protects the eggs in a brood pouch. 

The remora (Fig. 165, C) is a fish that 
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- 




Fig. 166. — The sea 
horse, a, anus; b.a, 
branchial aperture; 
m.p, brood pouch. 
(From the Cambridge 
Natural History.) 



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 Dipnoi or lungfishes 
(Fig. 167). There are only five species of these alive at the 
present time. One occurs in Australia, three in Central Africa, 




Fig. 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 





h -*??te. ' '.,- •i'.'-- ~''f- V. .v.- .. ,■ • .■•v v -. 'IV 



«3SF 




Fig. 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 muskaUunge 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 



s* ill 
»> 

.-4 Sj 






-/■*: ,r -ir>'* ■ ■ v ■■■ - '■.''■■ •■-♦ 


Mi 








SB?,* 

5 



Fig. 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 jewjish 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 



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 



.■As 







«•** H 0-"A Hi 



c "Nfe -; %j ;§fW 

Haw ™" n \-: , ' , ''-"''XVw 

f ^^^ 

Fig. 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 



2QO 



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 iqo8 was 41,615,277 pounds, valued at $1,042,683. The 
Bureau of Fisheries distributes millions, of fry every year. 







Bpp^ 



fa 



Fig. 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 
larva; 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 




Fig. 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- 




FlG. 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 




Fig. 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 vear. 

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. 




Fig. 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 1S66. 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. 

" In 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 



2 9 4 



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. S. BUREAU 
OF FISHERIES FROM JUNE 30, 1908, TO JUNE 30, 1909 



Species 


Eggs 


Fry 1 

786,626,000 


FlNGERLINGS 2 


Total 


1. Flatfish .... 






786,626,000 


2. Pike perch 


457,8so.ooo 


187,050,000 




644,900,000 


3. Whitefish .... 


142,220,000 


277,445,000 




419,665,000 


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 


223,661,283 


6. Cod 




i53,53 6 ,ooo 




i53.53 6 >°oo 


7. Blueback salmon 


100,000 


93.409.49 6 




93,509,49 6 


S. Lake trout 


22,806,000 


27,188,177 


i,345, 100 


51,339, 2 77 


g. Brook trout . 


905,000 


5,821,322 


3. 7 -'3. 489 


10,449,811 


10. Rainbow trout . . 


286,150 


292,408 


2,026,463 


2,605,021 


n. Large-mouth black 










bass .... 




3^.5oo 


540,962 


573,462 


12. Small-mouth black 










bass .... 




262,674 


111,924 


374,59 s 



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 

1 Fry are fish up to the time the yolk sac is absorbed and feeding begins. 

2 Fingerlings arc 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 stations 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. 



296 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 1S71 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 



297 



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 




Fig. 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 : — 

1. Annual report of the commissioner. 

2. Fish culture: 

(a) Methods. 

(b) Distribution of fish and eggs. 

(c) Fish diseases and parasites. 



298 PRACTICAL ZOOLOGY 

3. Aquatic biology : 

(a) Economic investigations. 

(b) 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 



The toads, frogs, salamanders, and a few other animals belong 
to the class Amphibia. 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 




Fig. 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. 

299 



300 



PRACTICAL ZOOLOGY 



The hellbender and mud puppy (Fig. 177) occur in streams in 
the eastern United States. 

The crimson-spotted 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 
larvae, worms, and small mollusks. The eggs are laid in April, 




Fig. 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. 170) 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. 1 So), 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 



*i^|ggj$j# 




^ v '^^fe ? ^^^^^PPPj 


mam 







Fig. 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. 



3° 2 



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 




Fig. 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 



3°3 



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. 181). 

The tree frogs 
(Fig. 182) are 
often erroneously 
called tree toads. 
They have adhe- 





■ : 1 






it 


* 


: ** ^.•V%f.^ 


&«at*- 






l'«#fr 


* 


* »^WsJv- ;V * 


j*SM • 




v % -"> 




* 

•* 




*&.. ■■ • 


54 


">-' * 




■vi:: -.I'v-. :jPs- 






Hi 
It 


pliS 



Fig. 181. — Green frog. (Photo, of living animal 
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 
to pigments in the 
skin, usually brown, 
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 




Fig. 1S2. — Tree frog. (Photo, of living ani- 
mal furnished by American Museum of Natural 
History.) 



3°4 



PRACTICAL ZOOLOGY 




branching cells which may spread out or contract, as shown in 
Figures 183-185. When expanded, the pigment covers a larger 

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 
Nv^ ~3^ |%^J X^L/S the reflection of light 

^-' v ->- i — 3F^-*vsJ m£y~- H^Q J 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- 
phibia. 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 
parts to any con- 
siderable extent, 
except in the 
early stages. As 
Fig. 185. —A pig- a general rule, 

ment cell of a frog . 

in a further state of the younger tad- 
contraction. (After p ie S regenerate limbs or tail more readilv 

Verworn.) J 

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 



Fig. 1S3. — A pigment cell of a frog ex- 
tended. (After Verworn.) 





Fig. 1S4. — A pigment cell of a 
frog in state of contraction. 



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 asstivate. 

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. As a 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 



3°° 



PRACTICAL ZOOLOGY 



four times its stomach capacity." This capacity may be judged 
from the fact that sixty-rive 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 



Fig. 




(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 
bad 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 Mar)' 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 Tbad, 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 




Fig. 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. 

3°9 



3io 



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 




Fig. 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, 
suprapy^al ; r, radius; sc, scapula; t, tibia; u, ulna; xp, xiphiplastron. 
(From Zittel.) 

most striking thing about a turtle is its protective shell (Fig. 18S). 
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 31 1 

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, and a 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. 



312 



PRACTICAL ZOOLOGY 





Fig. 190. — Musk turtle. (Photo, of living animal furnished by 
American Museum of Natural History.) 




Fig. 191. — Diamond-back terrapin. (Photo, of living animal 
furnished by American Museum of Natural History.) 



3*4 



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 (seep. 106). 




Fig. 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 



315 



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 
the Atlantic coast. 
Persistent persecu- 
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 turtles (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, 




Fig. 193. — Box tortoise. (Photo, of living 
animal furnished by American Museum of Natural 
History.) 



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. 




Fig. 



■ Giant tortoise. (Photo, of living animal. By permission. 
Copyright iqio by Sturgis and Walton Co.) 



The common box 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 giant 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 



3*7 



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 




Fig. 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 




Ui.^ 



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 green 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 homed " toads " (Fig. 198) of the western United States 
are reaUy 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 




Fig. 197. — Iguana. (Photo, furnished by American Museum of Natural 
History.) 




Fig. ryS. — Horned " toad." (Photo, of living animal. From 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. 




Fig. 15 



• 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. 



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. 




Fig. 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 surf ace 
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, 



THE REPTILIA 



3 2 3 




o 

I 



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. 









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Fie. 202. — Carter 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 ail 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. 




Fig. 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- 



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 



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Fig. 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 




Fig. 205. — Python. (By permission. Copyright by Sturgis and Walton Co.) 




Fig. 206. — Rattlesnake. (Photo, by Hegner.) 



32* 



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- 
(Jes 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- 
nected by ducts 
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 




Fig. 207. — Poison apparatus of rattlesnake. 
(Photo, furnished by American Museum of Natural 
History.) 



THE REPTILTA 



329 




33° 



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 treatment for snake bite is the administering of 
alcohol and sucking the wound. Neither of these is of much 




Fig. 200. — Copperhead snake. (Photo, of living animal furnished by 
American Museum of Natural History.) 

benefit. The first thing that should be done is to 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. In a 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. 



33- 



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 




Fie 



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 established 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. 



Upperl%ndilleS£',0r^r-y- 



Eye, /ft 9 " JfaiH** 

Forepead, \'\^-^<^' „-/^/' £ 
Nostril. \">fev. >^'/ r> / at 7 

/..-Pack 

\25w ---»■* Scopu/ars 

5<3~^X }- Lesser \ • 

L\^..TTediafi Kj/wf Corerts 
tf^^L.-Grea-ter) 
k^l--\~ -*-* - ( .- Secondaries 
^Rump 



Lower FTantlibTj?) 
Lore-' 

Chin f 

Throat!-;''' 

Ear'' : 

-3-c-astl^ 

Wind 




,- i r_y' ^.Upper Tail Coverts 
i§S?^ 1 72// 



Fig. 2ii. — Diagram showing names applied to the parts of a bird's body 
(From Wright.) 




Fig. 2i2. — Pigeons in flight. (Photo, by Hegner.) 

334 



CHAPTER XXXIV 
THE STRUCTURE AND ACTIVITIES OF BIRDS 

Birds 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 vertebras 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. When devoid of their feathers, 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 




Fig. 213. — Skeleton of the 
common fowl, male. 

1, premaxilla; 2, nasal; 
3, 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, fibu 
22, patella ; 23, tarsometa- 
tarsus ; 24, first toe; 25, 
second toe ; 26, third toe ; 
27, fourth toe; 28, spur; 
29, pubis; 30, ischium; 31, 
clavicle ; 32, coracoid ; 33, 
Shipley and MacBride.) 



keel of sternum; 34, xiphoid process. (From 



336 



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 




Fig. 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. 



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 




Fie. 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; 
n, arocari ; 0, 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. 10). When brought forward, the 
wings are bent at the wrist joint, with the narrow edge in front, 
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. — 
While on the ground birds 
walk, run, or hop, and when 
in trees, they cling to the (b) 




Fig. 216. — The structure of feathers 
I. Contour feather. a, quill; 



vane ; 
II. 



Contour feather. 

, shaft. 

Part of shaft (a) with two barbs 



III. Two barbules bearing hooklets 



(c). (From Coleman.) 



twigs with their claws. Their 

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 Various Purposes (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, 



34° 



PRACTICAL ZOOLOGY 



curved claws for capturing their prey. Birds that spend most 
of their time in flight, like the swift, possess weak feet. Usually 



MD Mf PD 03 



01 Ri BW Ml Hz Hi 




Anatomy of the pigeon. 



A, nostril; AD, ad-digital primary feather; B, external auditory meatus; 
BW, bastard wing; C, oesophagus; CA, right carotid artery; D, crop; DA, 
aorta; E, keel of sternum; F, right auricle; G, right ventricle; HV, hepatic 
vein; HI, 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; Ml, preaxial metacarpal; 
M2, middle metacarpal ; M3, postaxial metacarpal ; N, cloacal aperture ; 
Nl, preaxial digit; O, bursa Fabricii ; Ol, proximal phalanx of middle digit; 
02, distal phalanx of middle digit; P, pancreas; PA, right pectoral artery; 
PD, predigital primary ; PV, portal vein ; PI, first pancreatic duct ; P2, second 
pancreatic duct; P3, third pancreatic duct; Q, pygostyle ; R, rectum; RC, 
radial carpal bone ; RX, rectrices ; Rl, 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 




Fig. 218. — Paths of migration of the golden plover. (From Cooke.) 



342 



PRACTICAL ZOOLOGY 




Fig. 2ig. — Nest of prairie horned lark on the ground in a field. The 
darkly spotted egg is that of a cowbird. (Photo, by Hegner.) 




Fig. 220. — K-illdeer 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 Perching. — 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 vertebrae 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). 




Fig. 221. — Eggs of whippoorwill laid on dead leaves 
on the ground in the woods. (Photo, by Hegner.) 



344 



PRACTICAL ZOOLOGY 





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Fig. 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 




Fig. 22,j. — Bank swallow on its nest al 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 






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Fig. 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 ioo° 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 
follicles. The central 
axial rod of the feather 
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 



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Fig. 225. — Nest and eggs of the white-rumped 
shrike (butcher bird). The nest was built in a 
hawthorn tree 10 feet from the ground. (Photo. 
by Hegner.) 



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. 



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Fig. 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 only a 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 in theshape 
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- 
tain peculiarities in the in- 
ternal organs of birds may 
be pointed out here (Fig. 
217). The food is not 
masticated, as there are no 
teeth present . It is stored 
in an enlargement of the oesophagus, 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- 




FlG. 227. — Downy woodpecker at en- 
trance to nest-hole in a dead poplar tree. 
Her bill is filled with insects which she has 
captured on near-by trees and is about to 
feed to her young within the hole. (Photo. 
by Hegner.) 



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. 
It is an enlargement of the 
windpipe containing a valve 
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 




t*^. 



Fig. 228. — One young cowbird in a 
vireo's nest. The three young vireos 
were crowded out by the young cowbird. 
(Photo, by Hegner.) 



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 




Fig. 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 
August they fly to 
Labrador, where they 
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 



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Fig. 230. — Nest and eggs of Florida galinule. 
When disturbed the sitting bird slid down the 
rushes in the foreground into the waters of the 
marsh. (Photo, by Hegner.) 



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 




Fig. 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 




Fig. 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.) 









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Fig. 233. — Young blue jays. Young of this type are said to be altricial. 
They are naked and blind when hatched. (Photo, by Hegner.) 



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 




Fig. 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 plovers, 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 




Fig. 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 




Fig. 2.36 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 bv 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. 



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new 




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ftil^VvS 




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Fig. 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 Eggs. — 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, 236 A, 236 B). — 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. Appleton and Co., N. Y. City. 




Fig. 2,37. — The fossil remains of the oldest extinct bird known (Archteop- 
teryx). (From Zittel.) 



360 



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, 
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- 
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 

361 




Fig. 238. — Skeleton of the extinct 
moa. (After Owen.) 



362 



PRACTICAL ZOOLOGY 



Archceopteryx whose fossil remains were found in the rocks in 
Bavaria (Fig. 237). Its jaws were provided with teeth, its tail 




Fig. J3Q. — 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 




Fig. 240. — A group of penguins or rock-tiappers. (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 escape 
ing many of its ferieirrfe?\}by 
running, but most of the'fiight- 
less birds are an easy prey 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 rheasor 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- 
arctic regions. 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 




Fig. 241. — Pelican. (Photo, 
by Sanborn.) 



3 6 4 



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 




Fig. 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. 

Diving Birds. — 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 Swimmers. — 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 







M&i 




w ■ ''-'Jam 


«s»v, t?s&^m ** "** 7' //'/Ha 



Fig. 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. 



3 66 



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 




Fig. 244. — Bald eagl< 
by Plegner.) 



Fig. 245. — Screech owl at entrance 
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 wood 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 Bitterns. — 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, Rails, 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 Birds. — 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 whose 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, 




Fig. 246. — Nest and three eggs of the 
great horned owl. (Photo, by Hegner.) 



3 68 



PRACTICAL ZOOLOGY 




Fig. 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. 



f ijPWBHIiiirC" ") 












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Fig. 248. — Nighthawk sitting on her two eggs which were laid 
on a pebbly hillside. (Photo, by Hegner.) 



SOME COMMON BIRDS OF NORTH AMERICA 



369 




Fig. 249. — Chimney swift sitting 
on nest which was attached to the 
inside of a chimney twenty feet from 
the top. (Photo, by Hegner.) 



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 Birds. — The grouse, 
bob whites, pheasants, and tur- 
keys are the true game birds. 
The game birds are, as a rule, 
terrestrial, but many of them 
roost or feed in trees. Their 
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 
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 
white eggs. The young 
are naked when born, and are fed by regurgitation. 

Birds 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. 




Fig. 250. — Chimney swift clinging beside her 
nest down in a chimney. (Photo, by Hegner.) 



37° 



PRACTICAL ZOOLOGY 




Fig. 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 




Fig. 252. 



Nests of a colony of cliff swallows built on the side of a cliff near 
a river. (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 
cliffs. Two or three 
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, 




Fig. 253. — Cliff swallows building their nests 
underneath the eaves of a barn. (Photo, by 
Hegner.) 



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 
digging out grubs from 
beneath the bark. Most 
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. 

NlGHTHAWKS, WhIPIOORWILLS, SWIFTS, AND HUMMING 

Birds. — 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 




Fig. 254. — Phoebe building a nest above 
the window on the front porch of a house. 
(Photo, by Hegner.) 



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. 




Fig. 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 




Fig. 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. 
Perching Birds. — 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 MacmiUan Co., N. Y. City. 
(See also end of Chapter XXXIV.) 



CHAPTER XXXVI 
THE RELATIONS OF BIRDS TO MAN 

Birds 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 

376 



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 




Fig. 257. — Ostrich. (From Evans.) 



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 



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 



Fig. 258. — Food of nestling house 
wren. 



Fig. 259. — Food of adult house 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 in numbers. 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 

merit 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 XXXVII 

BIRD PROTECTION 1 

It 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. 



i. 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, 
money, or sport. It is 
only since civilized man 
reached this country that the great auk has become extinct, 
and that the passenger pigeon (Fig. 260), which roamed in 

1 A large part of this chapter is quoted direct from Forbush's Useful Birds and 
their Protection. 

382 




Fig. 260. — Passenger pigeon. (The bird 
with the long tail.) (Photo, by Hegner.) 



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, 
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 




Fig. 261. — Egret, nest, and young. 
(From Peabody and Hunt.) 



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. 



3 86 



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 
drowned or driven 
a w ay. T h o u- 
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- 




Fig. 262. — Woodcock on nest. (Photo, by Hegner.) 



BIRD PROTECTION 



387 



stacks 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. 




Fig. 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 larvae 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 i 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 for a 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 to save our wild animals from extinction (see Chap.XLI). 



BIRD PROTECTION 



391 



3. Methods of Attracting Birds 

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 





Tupelo. 



Barberry. 





Bnyberry. 



Greenbrier. 
Fig. 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 




Fig. 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- 




Fig. 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. 




Fig. 267. 



- House wren carrying a stick into a nesting box. 
(Photo, by Hegner.) 



The wren, although a very small bird, can use a relatively 
large house (Fig. 267). It should be about 8X6X6 inches 
inside. Near the top of one end an opening if 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 chickadee is almost exactly the size of 
the wren, but uses a smaller house. A box 3X.3X7 inches 



BIRD PROTECTION 



395 




Fig. 268. — Nest of house wren in nest- 
ing box shown in Fig. 267. (Photo, by 
Hegner.) 



inside, with an entrance 

1 J 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. 

The chickadee in its 

natural haunts rears its 

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 

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 X 6 
X 6 inches inside. 

Fig. 269. — Bluebird with a grasshopper for its The entrance IS in 

young. (Photo, by Hegner.) Qne end f rom 2 to 




396 



PRACTICAL ZOOLOGY 



i\ 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 
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 9X7X7 inches inside. The entrances should be 25 
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 




I-'ic. 270. — Screech owl. (Photo, by Hegner.) 



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-XXXVI. 



CHAPTER XXXVIII 
THE STRUCTURE AND ACTIVITIES OF MAMMALS 

Mammals are popularly known as " animals " or beasts. 
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 aerial 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 AND ACTIVITIES OF MAMMALS 399 



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 




Fig. 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, Ap), 
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 







Fig. 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. 



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 



Fig. 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 
palate 
tongue 







gullet 




bile 


sac 


bile duct 




\ 


transverse colon 







opening of bile 

and pancreatic ducts 

small intestine 




^ J- passage from nose to throat 

W 

_ cavity of mouth 

hLs— { throat cavity 

v-'X. 

^mJv — opening of windpipe 

\ ^ 



pylorus 



„^ T fj^^vla--- pancreatic duct 



appendix' 



Fig. 274. — Parts of the alimentary canal of 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 oesophagus, 
stomach, small intestine, large intestine, and rectum. The 



404 



PRACTICAL ZOOLOGY 



rr k 



principal glands are the salivary glands connected with the 
mouth, and the liver and pancreas connected with the small 

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- 




Fig. 275. — Diagrammatic section 
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.) 



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. 
2 7 5 , II) , which in some cases continues throughout life (Fig. 275,1). 

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, 
12), (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 
out by the permanent teeth, 
which last throughout the 
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 




Fig. 276. — Teeth of dog. 

i 2, second incisor; c, canine; pm 1, 
pm 4, first and fourth premolars ; ml, first 
molar. (From Shipley and MacBride.) 



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 nostrils. 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 

~VH ^-— w^__ EH 




Fig. 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- 



4o8 



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 




wAw 



Fig. 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 



meatus 

the drum 

of the ear 

{Tympanic 

Membrane) 




the loops 

(Semicircular 
Canals) 



the 
shell tube 
(Cochlea) 



the anvil the stirrup 

Eustachian tube 
Fig. 27g. — 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. 

Touch. — 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. 



4IO 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 411 



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 

collar bone 



knee cap 



vertebrae 



shoulder blade 
breast bone 




wrist bones 



Fig. 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 cross a 
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. 




Fig. 



- 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). 




Fig. 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 
area of about two hundred 
million square miles, five- 
eighths of which is covered 
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: (i) the law of 
definite habitats, (2) the law of dispersion, and (3) the law of 
barriers and highways. 

The Law or Definite Habitats. — 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 




Fig. 2S3. — The Norwegian lemming. 
(From Ingersoll.) 



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 activating. 

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 role 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 or 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. 

The Law of Barriers and Highways. — 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. 

Cosmopolitan 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. 



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 E. 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 




Fig. 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, 




Fig. 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, 




Garden mole. (Photo, by Brownell.) 



but a number are subterrestrial {i.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 disfigure a 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 




Fig. 287. A bat in a sleeping position, 
by Brownell.) 



(Photo. 



Bats. — The bats 
are easily distin- 
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 
other and with the 
hind feet, and usually 
the tail, by a thin 
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. 

2S7). 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- 

FlG. 288. — A flying " fox. 
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. 




Fig. 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 i) 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 




tr^-y- 



Fig. 290. — Striped hyrena 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 ot,her 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 hyaenas (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 
abundant through- 
out the forested 
regions of North 
America, where 
not exterminated. 
It is omnivorous, 
being especially 
fond of fish, blue- 
berries, and honey. 
(Fig. 291 




Fig. 291. — Grizzly bear. (From Ingersoll.) 



The grizzly bear of the Rocky Mountains 
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. 



426 



PRACTICAL ZOOLOGY 




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 




Fig. 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. 



1 JJBiiii 


By; 




I 







Fig. 2g4. — 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 proiect- 

1 J Fig. 2Q$. — Wildcat. (Photo, by 

ing upward from each ear. It 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 tiger, 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 a ton. 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. 



43° 



PRACTICAL ZOOLOGY 




Fig. 296. — The walrus. (From Flower 
and Lydekker.) 



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, 
and the absence of canines, 
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 tree 
squirrels (Fig. 
297) are the gray, 
fox and red squir- 
rels ; these are 
all excellent 

Climbers, and be- Fig. 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. 




Fig. 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 




Fig. 299. — Striped gopher at entrance to hole in ground. 
(Photo, by Hegner.) 



43 2 



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- 




Fig. 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). 



THE ORDERS OF MAMMALS 



433 




Fig. 301 



-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 



434 



PRACTICAL ZOOLOGY 



and vegetables are carried in the pouches, and such quantities 
are destroyed as to make these rodents quite injurious to crops. 




Fig. 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 this family. 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 antcatcrs 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. 




Fig.. 



-Porcupine. (Photo, by Brownc'll.) 



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. 



43 6 



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 




Fig. 304. — Stomach of a ruminant opened to show internal structure. 

a, oesophagus; 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 (ft), 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. 



■ 




Fig. 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 



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Fig. 306. — Elk or wapiti. (From 0. S. Dept. of Agric.) 



parks. The Virginia or white-tailed deer (Fig. 318) is the best 
known and most widely distributed of all our species. It is an 
inhabitant of forests. 

The pronghom 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. 




Fig. 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 



44© 



PRACTICAL ZOOLOGY 




Fig. 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. 



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. 




Fig. 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 




Fig. 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 
teeth are numerous and conical in shape. 

Toothed Whales. — 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 inhale (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 




Fig. 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 lemurs (Fig. 312) are quadrupeds and small or moderate 
in sizef they are covered with fur, and usually possess a long 
tail. 



444 



PRACTICAL ZOOLOGY 



The South 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. 



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Fig. 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: (i) gibbons, (2) orang-utans, (3) go- 
rillas, and (4) chimpanzees. 




Fig. 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-utans (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 




Fig. 



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 chimpanzee (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 Hominidce contains the single living species, 
Homo sapiens, or man. Man differs from the other primates 




Fie. 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 



44 8 



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 : 
(i) the Negroid races, (2) the Mongolian, and (3) the Cau- 




FlG. 316. — The Borncan 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, 




Fig. 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. 



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. Goals 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. In sum- 
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 sheepon which deer and elk 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 




Fig. 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. As a 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. 



45 6 



PRACTICAL ZOOLOGY 



The three fur animals still fairly abundant in the United 
States are the muskrat, the mink, and the skunk. Of these the 
muskral is most likely to retain its numbers, since it multiplies 
rapidly and, properly protected, is in no danger of extinction 




Fig. 3ig. — Skunk. (From Ingerso 



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. 




Fig. 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. 




Fig. 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. 




Fig. 322. — Apple tree injured by meadow mice. (From Lantz.) 



REFERENCES 

See end of Chapter XXXY1II. 



CHAPTER XLI 
THE PROTECTION AND PROPAGATION OF WILD LIFE 

Ideas 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 
of land. 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 1911, 1,486,228 hunting licenses were 
issued in twenty-seven of our states. Many persons, however, 

461 



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, 
81 17 useful blackbirds, 5291 quail, 5066 snipe, and 4948 plover. 
His grand total of slaughter was 139,628 game birds and sundries, 
representing twenty-nine species, several of them not game and 
useful." 1 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 T730 the last buffalo east of the Alleghenies had 
been killed. By 1810 none were to be found east of the Missis- 
sippi. 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. 1 

" 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 (1913) 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. 

I KnowUon, 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 Canon 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." l 

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 

1 Hornaday, Wild Life Conservation. 



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 190S, 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. 

" In 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 them. 

" 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. — Charles Scribner's 

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. 



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 has 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 47 1 

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 resume 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. 

Linnaeus (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, Linnaeus, 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, Sy sterna 
Natures. 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, i.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 (1S04-1892) 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). 




Fig. 32.3. — Charles Darwin. 
(From Davenport.) 



THE PROGRESS OF ZOOLOGY 475 

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 preexist- 
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 




Fig. 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, larvae, pupae, 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 



PRACTICAL ZOOLOGY 




Fig. ,3 2 S- — Louis Pasteur. (From Pcabody 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 




Fig. .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. 



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. 

aerial habitat, 2. 

Agassiz Association, 390. 

aigrettes, 349, 384, 3S5. 

air, bladder, 275; sac, 349. 

albatross, wandering, 365. 

alimentary canal, 12, 13 (see digestion 
and digestive system). 

alligator, 332. 

alternation of generations, 205-206. 

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, * 

antea'ter, 434. 

antelope, pronghorn, 438-439. 

antenna;, of crayfish, 131, 133 
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. 



-59- 



of 



aphid, 41-42. 

Aptcra, 19, 108. 

aqueous humor, 408. 

Arachnida, 107; classification of, 119- 
120; relations of, to man, 121-127. 

Araneida, 120. 

Arcella, 225. 

Archceopkryx, 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, 74, 231 ; non-pathogenic, 

74 ; pathogenic, 74. 
badger, 427, 454, 455- 
barb, 339, 346. 
barbule, 339, 346. 
barnacle, 138, i5g-140. 
barriers, law of, 417. 
basal disk, of Hydra, 199. 
basket star, 195. 
bass, black sea, 2SS; 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. 



4S3 



484 



INDEX 



beaver, dam, 433; family, 432. 

beche-de-mer, 1Q7. 

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, 35-3S, 37; scarab, 68; 
tiger, 69; vedalia, 71; whirligig, 25. 

bighorn, 439, 440. 

bile, 247. 

binary division, of Ameba, 223 ; of Para- 
mecium, 221. 

Biological Survey, United States, 390, 
466. 

birds, 7; altricial, 357, 359; anatomy 
of, 340, 34S ; ancient, 361 ; as de- 
stroyers of injurious animals, 377-380 
attracting, 391-397; baths for, 392 
beaks of, 338; beneficial, 378-3S0 
call notes of, 349 ; commercial value 
of, 376-377; destruction of, 382-389; 
diving, 364; domesticated, 380-381; 
eggs of, as food, 376 ; feeding on moths, 
45; feet, 337, 339; flightless, 363; 
game, 369, 376; houses for, 393-397; 
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, 359; protection of, 
382-397; relations of, to man, 376- 
381 ; shore, 367 ; skeleton of, 335, 336 ; 
songs of, 349; structure of, 335~349; 
water, 364; wings of, 335. 

bisexual reproduction, 262. 

bison, 439, 462. 

bittern, 350, 357, 366. 

bivalve, 147 (see mussel). 

blackbird, 375, 379, 380. 

blackhead. 152. 

bladder, of frog, 247, 252. 

blood, of crayfish, 134; of grasshopper, 
14-15 (see circulation). 

blood corpuscle, 14. 

bloodsucker, 175. 

bluebird, 373, 383; feeding young, 395; 
house for, 395".5Q6- 

bluegill, 287. 

blue jay, 353. 

blue racer, 325. 



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, 15. 

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, 2S1. 

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. 
ccphalothorax, 131. 



INDEX 



48s 



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. 

Chmtopoda, 177. 

chameleon, 319. 

cheetah, 429. 

chickadee, 304-305. 

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, 79. 

chromatin, 263, 265. 

chromosome, 263, 265. 

chrysalis, 20. 

cicada, 24, 25. 

cilia, of Paramecium, 218, 219; on gills 
of mussel, 149. 

circulation, of crayfish, 132, 134 ; of 
earthworm, 171-172; of frog, 248; of 
grasshopper, I4-15 ; of man, 406; of 
mussel, 151. 

circulatory system, 238 ; of grasshopper, 
H-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, 
102 ; 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, n; of mammal, 
401. 

cobra, 331. 

cochineal, 65. 

cochlea, 409. 

cockroach, 57-58. 

cocoon, 20; of earthworm, 173. 

cod, 289. 



Ccelenkrata, 7, 198-210. 

ccelom, 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, 400. 

coloration, aggressive, 31 ; protective, 
30 ; warning, 30. 

columella, of snail shell, 159. 

commensalism, 139. 

conjugation, 221. 

conservation of our natural resources, 
469-471. 

contractility, 241. 

control, of house fly, So-83 ; of insect 
pests, 34, 46-47- 

convolutions of brain, 407, 408. 

coot, 367. 

copperhead, 330, 331. 

coral, 7, 208-2 10 ; organ pipe, 209 ; 
polyp, 208 ; precious, 209 ; reef, 208. 

cormorant, 365, 366. 

corpuscles, blood, of frog, 248; of 
mammals, 406 (see circulation). 

cosmopolitan animals, 417-418. 

cougar, 429, 454. 

covey, 369. 

cowbird, 349, 356, 380. 

coxa, 11. 

coyote, 454. 

crab, 7; blue, 137. 138; edible, 137, 138; 
fiddler, 137, 13S; 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, 33i~333- 



4 S6 



INDEX 



crop, of bird, 34S ; of earthworm, 171; 

of grasshopper, 12, 1.3. 
crow, 375, 370, 389. 
Crustacea, 107, 137-144. 
cuckoo, 371, 380. 
Culex mosquito, 87. 
cuticula, of insects, 16. 
Cuvier, 473. 

Cyclops, 140, 141; and disease, 143, 181. 
cyclostomes, 235, 268, 270. 
cysticercus, 189, 190. 

daddy longlegs, 120. 

Daphnia, 140, 141. 

Darwin, 4, 173, 474. 

Decapod a, 137. 

deer, 436, 438, 45 2-453, 465-466. 

Demos pongice, 217. 

dengue, carried by mosquitoes, 96. 

dentine, 404, 405. 

Dero, 176. 

development, 269 (see embryology, and 
metamorphosis). 

devilfish, 166. 

diaphragm, 402, 407. 

Diffiugia, 225. 

digestion, in crayfish, 133 ; in earth- 
worm, 171; in frog, 246 ; in grass- 
hopper, 13; in Hydra, 203; intra- 
cellular, 203 ; in mammals, 403 ; in 
mussel, 150; in Paramecium, 219. 

digestive glands, of crayfish, 134 (see 
liver). 

digestive system, 237-238 (see digestion). 

digits, 255. 

dimorphism, 205. 

Diplopoda, 129. 

Dipnoi, 284. 

Diptcra, 100. 

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 

dogfish shark, 278. 

dolphin, 442. 

domestic animals, parasites of, 48-56. 

domesticated birds, 380. 

dove, 360, 380. 

drone honeybee, 63. 



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. 

Echiuodcrmata, 7, 192-197. 

ectoderm, of frog, 265, 266; of Hydra, 
199, 202. 

ectosarc, 222, 22^. 

eel, 235 ; mud, 301, 302 ; true, 282, 283 ; 
vinegar, 178. 

eggs, of bird, 354, 35S; of fish, 275, 276; 
of frog, 264 ; of grasshopper, 18 ; of 
Hydra, 199, 204; of mussel, 151; of 
turtle, 311. 

egret, 3S3, 384. 

Elasmobrauchii, 278-279. 

elephant, 442, 450. 

elephantiasis, 96, 181. 

elk, 437-138, 452. 

embryo, of frog, 2O4, 265. 

embryology, of frog, 264, 267 ; of Hydra, 
204 ; of insects, 19. 

enamel, 404, 405. * 

endosarc, 222, 223. 

endoskeleton, 254, 255 

Entameba, 226, 228. 

entoderm, of frog, 265, 266; of Hydra, 
199, 202. 

Enlomostraca, 144. 

epiphragm, 158. 

Euglcna, 224. 

Eusponzia, 212, 216. 

eustachian tube, 409. 

excretion, 220; in earthworm, 171-172; 
in frog, 252; in grasshopper, 15-16; 
in mammals, 407; in mussel, 151. 

excretory system, 238; in Planaria, 184 
(see excretion). 

exoskclctun, of crayfish, 131 ; of croco- 
dile, a^i ; of grasshopper, 16. 

eye, of crayfish, 132, 133; of fish, 271, 



INDEX 



487 



274; of frog, 258, 261; of insect, 17; 

of lamprey eel, 260 ; of man, 408; of 

snail, 160; of spicier, 114. 
eyelashes, 409. 
eyelid, 261. 
eyespot, of Euglena, 224; of Planaria, 

183. 

falcon, 370. 

family, 104. 

fangs, 328. 

fat, 399. 

feathers, 339, 346, 377. 

feces, 219. 

feet, of birds, 337, 339. 

femur, 256 (see skeleton). 

fertilization, in earthworm, 173; in fish, 

276; in frog, 264; in Hydra, 203; in 

mammal, 410. 
fever, dumdum, 229 ; recurrent, 229 ; 

relapsing, 229; Texas, 228; yellow, 

229. 
fig insect, 69. 
Filaria, 181. 
filoplumes, 347. 
fingerling, 294. 
fins, 271, 273. 
fish, 7, 27S-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, 2S3 ; 

relations to man, 285-298; relations 

to mussels, 152. 
fishing industry, 293. 
fission, of Hydra, 203. 
flagella, of Euglena, 224 ; of sponge, 

211. 
flamingo, 367. 
flatworms, 183-191. 
flea, and bubonic plague, 98 ; cat and 

dog, 52, 53; house, 53; jigger, 52; 

water, 140, 141. 
flesh, 256. 
flounder, 288, 290. 
fluke, liver, I86-188. 
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. 



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, 294. 
fur, 455. 

gall, insect, 66, 67. 
gallinule, 351, 357. 
game, protection of, 466 ; slaughter of, 

462. 
ganglia, 17 (see nervous system), 
gapes, 181. 
gar pike, 280, 281. 
gastral cavity, of sponge, 211, 213. 
gastric, juice, 247; mill, 134. 
gastrocnemius muscle, 256, 257. 
Gastropoda, 158, 167. 
gastro vascular 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, 191. 

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, 149. 
giraffe, 436, 



488 



INDEX 



gizzard, of bird, 34S; of earthworm, 171. 

gland, ductless, 253; of frog, 252; mam- 
mary, 419 ; mucous, 253 ; poison, 253 ; 
salivary, 2$^ ; 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, 439- 

goat, 418, 439, 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, aerial, 2 ; fresh-water, 3 ; law 
of, 416-417 ; of Hydra, 200; of 
mammals, 398; parasitic, 3; sea 
water, 3 ; terrestrial, 2. 

haddock, 289. 

haemoglobin, 248. 

hair, contour, 400 ; of insects, 16; of 
mammals, 399, 400; woolly, 400. 

hake, 289. 

halibut, 288. 

Harvey, 248. 

harvestman, 118. 

hawk, 388, 407; chicken, 379; Cooper, 
379; hen, 379; red-tailed, 347, 355, 
356, 357, 379; roughleg, 379. 



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, 405. 

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. 

HominidcE, 447-449. 

Homo, 447. 

honeybee, 63-64 ; colony of, 205 ; legs 

of, 27-2Q. 

honeycomb, 64, 65. 

honevdew, 42. 

hoof, 401. 

hookworm, 179, 182. 

hopperdozer, 22. 

horns, 401. 

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, 5. 

hyaena, 424, 425. 

hydatid, 190, 191. 

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, 22S. 

Hydrozoa, 210. 

Hymcnoptera, 109. 



INDEX 



489 



Iguana, 3 ig, 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, 71-7 2 ; 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. 389- 
jellyfish, 7, 207. 
jewfish, 2S8. 
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. 



laws, game, 464. 

leeches, 175. 

legs, of grasshopper, io-ll ; of honeybee, 

27-29. 
lemming, 415-4I6. 
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. 
Linnaeus, 67, 103, 473. 
lion, mountain, 429. 
liver, of frog, 247, 253; of mussel, 147, 

151- 
lizards, 319-322. 
llama, 450. 

lobster, 130, 131, 142. 
locomotion, of Amcba, 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. 
Lymncea, 162, 163. 
lymph, 250. 
lymphatic system, 406. 
lynx, 428. 

mackerel, 288, 289. 
macronucleus, 219. 

maggot, 20. 

Malacostraca, 144. 

malaria, S7-93, 227. 

Malpighian tubules, 12, 16. 

Mammalia, 7, 234. 

mammals, 39S-459 ; aquatic, 398; ar- 
boreal, 39S; circulation in, 406; claws 
of, 401 ; color of, 400 ; digestion in, 
403; domesticated, 450-451; ear of, 
409 ; egg laying of, 419~42o ; excretion 
in, 407 ; eye of, 408 ; flesh-eating, 423- 



49° 



INDEX 



430; flying, 422-423; fur-bearing, 
455-457; game, 451-45,3 ; geographical 
distribution of, 416; gnawing, 430-434, 
45S-459; habitats of, 308, 416; 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, 419-449 ; 
pouched, 42O-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, 149. 

mantle cavity, 148. 

marten, 425, 455. 

martin, house for, 396. 

massasauga, 328. 

Masligameba, 225, 226. 

Mastigophora, 233. 

mating, of birds, 354. 

maxillae, of crayfish, 134 ; of grasshopper, 
13- 

maxillipedes, 134. 

mayfly, 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, 19-2o; of mussel, 152. 

Melazoa, 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, 295. 

mimicry, 30. 

mink, 427, 454, 455. 

miricidium, 187. 

mite, 119, 121; chicken, 124; face, 126 ; 



follicle, 126; gill, 127; harvest, 125, 
126; itch, 125,126; scab, 124, 125. 

mitosis, 263, 2D4. 

moa, 361, 362. 

moccasin, water, 329, 330. 

mockingbird, 380. 

molar teeth, 405. 

mole, 421. 

mole-cricket, 24, 25. 

Mollusca, 7, 157, 15S ; 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, S6-97 ; control of, 90-96; 
eggs of, 87, 90; enemies of, 90; and 
intestinal worms, rS 1 ; larva of, 87, 
90; malarial, 87-93, 227 ; mouth parts 
of, 26 ; pupa of, 88, 90 ; yellow fever, 
93-y6. 

moth, anatomy of, 26 ; clothes, 60 ; cod- 
ling, 42; fish, 57, 58; gypsy* 44-46; 
leopard, 45, 46 ; silkworm, 62 ; tus- 
sock, 43, 44. 

mother-of-pearl, 148. 

mouth, of Euglena, 224 ; of frog, 246 ; 
of Hydra, 199 ; of lamprey eel, 268, 
269; of mussel, 147, 150; of Para- 
mecium, 21S, 219; of Plan-aria, 1S3. 

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. 

Muller, 474. 

muscle, 247, 256. 

muscular system, 238, 256, 257. 

museums, 479. 

muskallunge, 286. 

muskrat, 456. 

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, H6-148. 

Myriapoda, 107, 128-129, 



INDEX 



491 



nail, 401. 

Nais, 176. 

nasal cavities, 258, 261. 

Nautilus, 165, 166. 

nectar, 64. 

Nemathelminlhcs, 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, 407-40S; central, 
256; of earthworm, 169, 170, 172; of 
frog, 256-261; functions of, 259; of 
grasshopper, 12, 17-18; peripheral, 
256 ; of Plan-aria, 184 ; sympathetic, 
260; of turtle, 311. 

nests, of birds, 354. 

neuron, 259, 260. 

Neuropt-era, 108. 

newt, 300. 

nighthawk, 368, 372. 

Nosema, 230. 

nostril, 275. 

nucleus, 219, 220, 222, 223, 239, 240. 

nudibranch, 163, 164. 

nutrition, holophytic, 224; holozoic, 224. 

nymph, 19. 

octopus, 164, 166. 

oesophagus, of crayfish, 132, 134 ; of 
frog, 247; of grasshopper, 12, 13; of 
mussel, 147, 150. 

olfactory capsules, 254. 

olfactory organs, 17, 160 (see sense 
organs) . 

Oligocholia, 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. 

Orthoptera, 108. 

osculum, 2ii, 212 . 

osprey, 385. 



Oslrea, 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, 439, 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, 429. 

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, 7I-72 ; Protozoa, 226, 
227 ; worms, 80. 

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. 

Pclecypoda, 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, 14S. 

periwinkle, 163, 164. 

peroneus muscle, 256, 257. 

petrel, stormy, 365. 



492 



INDEX 



pewee, wood, 345. 
Phahngidea, 120. 

pharynx, of earthworm, 171 ; of Planar ia, 
184. 

phylum, 104. 

phccbe, 372. 

Pkysa, 162. 

physiology, 16. 

pickerel, 286. 

pig. 45 1- 

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, 08-100. 

plaice, 288. 

Planaria, I83-185, 191. 

plankton, 230. 

Planorbis, 162, 163. 

Plasmodium, 88,226, 227. 

Platyhclminthcs, 7, 191. 

Plcuroccra, 162. . 

plover, migration of, 351. 

plumes, of birds, 377. 

poison, of spider, 114, 118. 

poison apparatus, of rattlesnake, 328. 

poisonous, Amphibia, 305; reptiles, ^^3- 

pollen, basket, 27, 28; brush, 27, 28; 
comb, 27, 28. 

pollination of flowers by insects, 68-70. 

pollock, 289. 

Polychata, 177. 

Polygyra, 162. 

polymorphism, 205. 

polyp, 7, 205. 

porcupine, 435, 436. 

pores, of sponge, 211, 213. 

Porifera, 7. 

Portuguese man-of-war, 205. 

prairie chicken, 383. 

prawn, 130, 142. 

predaceous, insect, 70-71 ; mammal, 

453-455- 
prehallux, 256. 
-premolar teeth, 405. 
primates, 443-449. 
proboscis, of housefly, 76 ; of moth, 26 ; 

of Planaria, 183, 184. 
proglottides, 188, 189. 



propagation of wild life, 465-468. 

protection of wild life, 461-464. 

protective coloration, 16, 29-31 (see 
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, 429. 

pumpkin seed, 287. 

pupa, 20. 

pupil, in eye of frog, 262 (see eye). 

python, 326, 327. 

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, 32S. 

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, 101. 

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, 1S-19 ; of Hydra, 
203; of liver fluke, 1S6-188; 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 



493 



Repiilia, 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 Jose scale, 39-41, 40. 

sapsucker, 379. 

sartorius muscle, 256, 257. 

sawfish, 278, 279. 

scale insects, cottony maple, 46 ; fluted, 
7O-71 ; lac, 65 ; Sa*n Jose, 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, 207-2O8; cucumber, 196, 
197; horse, 283; lilies, 197 ; lion, 106, 
429 ; pen, 209 ; urchin, 7, 196. 

seal, 414, 429, 430. 

secretion, 220, 252; internal, 253. 

segmentation, 174. 

semicircular canals, 409. 

seminal vesicle, 262, 263. 

sense organs, of earthworm, 172 ; of fish, 
274-275 ; of frog, 261 ; of grasshopper 
16; of insects, 16-17; OI lamprey eel. 



269; of mammals, 408-410 ; of mussel, 
150; of snail, 160; of spider, 114; of 
turtle, 311. 

septa, of earthworm, 169, 174. 

setse, of earthworm, 170. 

shark, 278. 

sheep, 450, 451; botfly of, 50; liver 
fluke of, I86-188; 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, 2 3°- 

silver fish, 57, 58. 

siphon, of mussel, 146, 148. 

skate, 278. 

skeletal system, 238. 

skeleton, of bird, 33s, 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 



INDEX 



389; grasshopper, 380; vesper, 374, 
375- 

spawn, 276, 295. 

species, 104. 

spermatozoa, 2O3 ; of Hydra, 203 ; of 
mussel, 151 (see reproduction). 

spicules, of sponge, 214, 215. 

spider, 7, 111-118; aerial, 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- 

"3- 

spinal cord, 258, 259, 260. 

spinnerets, of spider, 115. 

spiracle, of frog, 267. 

spirochsets, 228, 229. 

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, 2H-212; 
solitary, 212; spicules of, 214, 215; 
spongin of, 214, 215. 

spongin, 214, 215. 

spores, of malaria parasite, 226. 

sporocyst, 187. 

Sporozoa, 227, 2,i$. 

sporulation, 223, 224. 

squid, 164, 165. 

squirrels, 388, 414; ground, 431; flying, 
432; tree, 430. 

stapes, 409. 

starfish, 7, 193-194 ; relation of, to oyster, 
155. 

statocyst, of snail, 160. 

Slentor, 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, 279, 280. 

sucker, 280, 281 ; of liver fluke, 186. 

sunfish, 287. 

swallow, 380; bank, 344, 355; cliff, 370, 
371. 



swan, 366, 381. 

swift, chimney, 369, 370, 374, 387. 
swimmeret, of crayfish, 132, 135. 
Sycolypus, 163, 164. 

symmetry, 192. 

sympathetic nervous system, 12, 17-18, 

260. 
Syngamus, 181, 182. 
Synura, 231. 
syphilis, germ of, 229. 

Tmida, 188. 

tail, of bird, 339. 

tapeworm, 7, I88-191. 

tapir, 41S, 441. 

tarantula, 117. 

tarpon, 286, 287. 

tarsus, of grasshopper, n. 

taste, in fish, 275; in insects, 17; in 

mammals, 410 (see sense organs). 
teeth, of frog, 246; of mammals, 404- 

406 ; milk, 405. 
Tcleostomi, 279-284. 
tendon, 256. 

tentacles, of Hydra, 199, 200; of jelly- 
fish, 207; of snail, 159, 160. 
tern, 352, 357, 365. 
terrapin, 313, 315, sSi- 
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, n. 
tibiolibula, 25O. 
tick, 1 19 ; fowl, 124 ; sheep, 53~54 ; 

spotted fever, 126; Texas fever, 121- 

122. 
tiger, 429. 
tissues, 241-242. 

toad, 100, 305-307; horned, 319, 320. 
tongue, of frog, 246 ; of lamprey eel, 268, 

269 
tortoise, 315, 316. 
tortoise shell, 317, sm. 
touch, in fish, 275; in insects, 17; in 

mammals, 409 (see sense organs). 
trachea, of mammals, 400. 



INDEX 



495 



tracheae, of grasshopper, 15; of spider, 
114. 

tracks, of mammals, 4io-413. 

Trematoda, 185, 191. 

trepang, 197. 

Trichina, 179, 180. 

trichocyst, 21S, 219. 

trochanter, n. 

trout, 276, 285, 286, 289, 291, 295. 

Trypanosoma, 226, 228. 

tuberculosis, germs of, 74, 79. 

Tubifex, 176. 

tuna, 288. 

Turbellaria, 185, 191. 

turbot, 2S8. 

turkey, 369, 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, 2 20,222, 223; food, 

219. 
valves, of mussel, 146, 148. 
ventral nerve cord, of earthworm, 

172. 
ventricle, of frog, 249 ; of mussel, 147, 

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, 17 (see eye and sense 

organs) . 



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, iri-113. 

weevil, alfalfa, 35, 36; bean, 39; cotton 
boll, 35, 36 ; pea, 39. 

whales, 442-443. 

whippoorwill, 343, 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, So; 
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 ; practical, 471 ; 
progress of, 472-481. 



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chosen with reference to this end. Structure and classification are not 
neglected, but they are made subordinate to function, because the lat- 
ter is more significant for boys and girls of high school age. The 
activities of plants and animals and their use by man are shown to be 
closely related to human welfare, for example, the use of plants for 
food and clothing ; the relation of mosquitoes to malaria and yellow 
fever and of flies to typhoid fever; the work of bees and silkworms; 
the importance of birds as destroyers of insects ; the work of bacteria 
as the friends or as the foes of man, etc. 

The significant character of the book is further emphasized by sim- 
plicity of style, abundant half-tone illustrations, chapter summaries, and 
interesting laboratory exercises. Text and laboratory manual are com- 
bined in one. In the appendix are found valuable suggestions for 
teachers and pupils concerning laboratory equipment, special topics, 
notebooks, and reference books. 



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