ADAPTATIONS 



331 



degree in various extinct types of fishes. The crab and lobster 

 with claws and carapace are well defended against their enemies, 

 and the hermit crab, with its trick of thrusting its unprotected 

 body within a cast-off shell of a sea snail, finds in this instinct 

 a perfect defense. Insects also, especially beetles, are protected 

 by their coats of mail. Scales and spines of many sorts serve 

 to defend the bodies of rep- 

 tiles and fishes, while feathers 

 protect the bodies of birds 

 and hair those of most 

 mammals. 



The ways in which ani- 

 mals make themselves dis- 

 agreeable or dangerous to 

 their captors are almost as 

 varied as the animals them- 

 selves. Besides the teeth, 

 claws, and horns of ordinary 

 attack and defense, we find 

 among the mammals many 

 special structures or con- 

 trivances which serve for 

 defense through making their 

 possessors unpleasant. The 

 scent glands of the skunk 

 and its relatives serve as 

 examples. The porcupine has 

 the bristles in its fur special- 

 ized as quills, barbed and 

 detachable. These quills fill 

 the mouth of an attacking 



wolf or fox, and serve well the purpose of defense. The 

 hedgehog of Europe, an animal of different nature, being re- 

 lated 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 head (also defended by a 

 bony shield) it is as well protected as a turtle. 



The turtles are all protected by bony shields, and some of 

 them, the box turtles, may close their shields almost hermet- 

 ically. The snakes broaden their heads, swell their necks, or 

 show their forked tongues to frighten their enemies. Some of 



FIG. 191. Scorpion showing the special 

 development of certain mouth parts (the 

 maxillary palpi) as pincerlike organs for 

 grasping. On the posterior tip of the 

 body is the poison sting. 



