CEAYFISH, LOBSTERS, SPIDERS, A^D INSECTS 133 



surface, thus stopping more flow and the wound soon 

 heals. A crayfish with one claw smaller than the other is 

 occasionally found. The smaller claw is simply replacing 

 one that has been lost. 



Habitat and habits. — Crayfishes are widely distributed 

 over the United States except -in parts of New England and 

 may be found in most ponds, creeks, rivers, lakes, and in 

 many springs. Some species live in holes dug deep enough 

 to reach water or, at least, considerable moisture. One of 

 these burrows, traced to its bottom in digging a mine shaft, 

 extended straight downward for twenty-six feet. 



Some of the burrowing species build mud chimneys about 

 the entrances to their burrows. Those that hve in water 

 usually remain close to the bottom, where they hide during 

 the day beneath stones, sticks, or plants. 



Methods of protection. — The crayfish often escapes from 

 its pursuer in the cloud of sediment stirred up in its move- 

 ments. In addition, the great pairs of claws are very effi- 

 cient organs of defense against its lesser enemies, at least. 

 Moreover, it lives near the bottom where there are many 

 places in which to hide and its threatening attitude, when 

 hard pressed, must often frighten its enemies away. Finally, 

 the body varies a good deal in color and blends so nicely 

 with surromiding objects that it is hard to distinguish. 



Molting of the crayfish. — During the growth of this 

 animal it sheds its hard, thick covering from time to time. 

 It is evident that the body cannot expand when confined 

 in such an unyielding investment, and special provision has 

 been made for growth by casting off, or molting the hard, 

 limy skin. Before molting, a new soft skin is formed be- 

 neath the old one. When ready to molt, the carapace 

 splits along the middle line of the dorsal surface, and the 



