broad chisel-like incisor teeth for cutting off the foliage, and teeth of very similar form are developed in the dif

ferent groups of planteating fishes. Molar teeth are found when it

FIG. 160.-Head of mosquito (female), showing the piercing needle-like mouth parts which compose the "bill."

is necessary that the food should be crushed or chewed, and the sharp canine teeth go with a flesh diet.

long neck of the giraffe en

ables it to browse on the

foliage of trees in grassless regions.

Insects like the leafbeetles and the grasshoppers, that feed on the foliage of plants, have a pair of jaws, broad but

The

sharply edged, for cutting off bits of leaves and stems. Those which take only liquid food, as the butterflies and sucking-bugs, have their mouth parts modified to form a slender, hollow sucking beak or proboscis, which can be thrust into a flower nectary,

or into the green tissue of plants or the flesh of animals, to suck up nectar or plant sap or blood, depending on the special food habits of the insect. The honey-bee has a very complicated equipment of mouth parts fitted for taking either solid food like pollen, or liquid food like the nectar of flowers. The mosquito has a "bill" (Fig. 160) composed of six sharp, slender needles for piercing and lacerating the flesh, and a long tubular under lip through which the blood can flow into the mouth. Some predaceous insects, as the praying-horse (Fig. 161), have their fore legs developed into formidable grasping organs for seizing and holding their prey.

256. Adaptation for self-defense. For self-protection, carnivorous animals use the same weapons to defend themselves which serve to secure their prey; but these as well as

other animals may protect themselves in other fashions. Most of the hoofed animals are provided with horns, struc

FIG. 163.-Section of bark of live oak tree with acorns placed in it by the Californian woodpecker (Melanerpes formicivorus bairdii).-From photograph, Stanford University, California.

tures useless in procuring food but often of great effectiveness as weapons of defense. To the category of structures useful for self-defense belong the many peculiarities of coloration known as "recognition marks." These are marks,

not otherwise useful, which are supposed to enable members of any one species to recognize their own kind among the mass of animal life. To this category belongs the

FIG. 164. Centiped. The

foremost pair of legs is modified to be a pair of

seizing and stinging organs. An adaptation

for self-defense and for securing food.

black tip of the weasel's tail, which remains the same whatever the changes in the outer fur. Another example is seen in the white outer feathers of the tail of the meadow-lark as well as in certain sparrows and warblers. The white on the skunk's back and tail serves the same purpose and also as a warning. It is to the skunk's advantage not to be hidden, for to be seen in the crowd of animals is to be avoided by them. The songs of birds and the calls of various creatures serve also as recognition marks. Each species knows and heeds its own characteristic song or cry, and it is a source of mutual protection. The fur-seal pup knows its mother's call, even though ten thousand other mothers are calling on the rookery.

The ways in which animals make themselves disagreeable or dangerous to their captors are almost as varied as the animals themselves. Besides the teeth, claws, and horns of ordinary attack and defense, we find among the mammals many special structures or contrivances which serve for defense through making their possession unpleasant. The scent glands of the skunk and its relatives are noticed above. The porcupine has the bristles in its fur specialized as quills, barbed and detachable. These quills fill the mouth of an attacking fox or wolf, and serve well the purpose of defense. The hedgehog of Europe, an animal of different nature, being related rather to the mole than to

the squirrel, has a similar armature of quills. The armadillo of the tropics has movable shields, and when it withdraws its

FIG. 165.-Flying fishes. (The upper one a species of Cypselurus, the lower of Exocœtus.) These fishes escape from their enemies by leaping into the air and sailing or "flying" long distances.

head (which is also defended by a bony shield) it is as well protected as a turtle.

FIG. 166.-The horned toad (Phrynosoma blainvillei). The spiny covering repels many enemies.

Special organs for defense of this nature are rare among birds, but numerous among reptiles. The turtles are all