protected by bony shields, and some of them, the box-turtles, may close their shields almost hermetically. The snakes broaden their heads, swell their necks, or show their forked tongues to frighten their enemies. Some of them

are further armed with fangs connected with a venom gland, so that to most animals their bite is deadly. Besides its fangs the rattlesnake has a rattle on the tail made up of a

FIG. 67.-Mad tom (Schilbeodes furiosus) with poisoned pectoral spine.

succession of bony clappers, modified vertebræ, and scales, by which intruders are warned of their presence. This sharp and insistent buzz is a warning to animals of other species and a recognition signal to those of its own kind.

Even the fishes have many modes of self-defense through giving pain or injury to those who would swallow them. The cat-fishes or horned pouts when attacked set immovably the sharp spine of the pectoral fin, inflicting a jagged wound. Pelicans who have swallowed a catfish have been known to die of the wounds inflicted by the fish's spine. In the group of scorpionfishes and toad-fishes are certain genera in which these spines are provided with poison glands. These may inflict very severe wounds to other fishes, or

even to birds or man. One of this group of poison-fishes is the nokee (Emmydrichthys, Fig. 66). A group of small freshwater cat-fishes, known as the mad toms (Fig. 67), have also a poison gland attached to the pectoral spine, and its sting is most exasperating, like the sting of a wasp. The sting-rays (Fig. 68) of many species FIG. 68-A sting-ray have a strong, jagged spine on the tail, covered with slime, and armed with broad saw-like teeth. This inflicts a dangerous wound, not through the presence of specific venom, but from the danger of blood poisoning arising from the slime, and the ragged or unclean cut.

Many fishes are defended by a coat of mail or a coat of sharp thorns. The globe-fishes and porcupine-fishes (Fig. 69) are for the most part defended by spines, but their instinct to swallow air gives them an additional safeguard. When one of these fishes is disturbed it rises to the surface,

134

gulps air until its capacious stomach is filled, and then
floats belly upward on the surface. It is thus protected
The torpe-
from other fishes, though easily taken by man.
do, electric eel, electric cat-fish, and star-gazer, surprise and

FIG. 69.-Porcupine-fish (Diodon hystrix), the
lower ones swimming normally, the upper
one floating belly upward, with inflated
stomach.-Drawn from specimens from the
Florida Keys.

stagger their captors by means of electric shocks. In the torpedo or electric ray (Fig. 70), found on the sandy shores of all warm seas, on either side of the head is a large honeycomb-like structure which yields a strong electric shock whenever the live fish is touched. This shock is felt severely if the fish be stabbed with a knife or metallic The electric eel spear. of the rivers of Paraguay and southern Brazil is said to give severe shocks to herds of wild horses driven through the streams, and similar accounts are given of the clectric cat-fish of the Nile.

Among the insects, the possession of stings The is not uncommon. wasps and bees are fa

miliar examples of stinging insects, but many other kinds,
All insects have
less familiar, are similarly protected.
their bodies covered with a coat of armor, composed of a
horny substance called chitin. In some cases this chitin-

ous coat is very thick and serves to protect them effectually. This is especially true of the beetles. Some insects are inedible (as mentioned in Chapter XII), and are conspicuously colored so as to be readily recognized by insectivorous birds. The birds, knowing by experience that these insects are ill-tasting, avoid them. Others are effectively concealed from their enemies by their close resemblance in color and marking to their surroundings. These protective resem

races must be considered. In struggles of species with those of their own kind, the term rivalry may be applied. Actual warfare is confined mainly to males in the breeding season and to polygamous animals. Among those in which the male mates with many females, he must struggle with other males for their possession. In all the groups of vertebrates the sexes are about equal in numbers. Where mating exists, either for the season or for life, this condition does not involve serious struggle or destructive rivalry.

FIG. 70.-Torpedo or electric ray (Narcine brasiliensis), showing electric cells.

Among monogamous birds, or those which pair, the male courts the female of his choice by song and by display

FIG. 71.-A fur seel (Callorhinus alascanus) family on the Vostochni rookery, St. Paul Island. male.-Photograph by D. W. THOMPSON and A. W. MARRETT.