CRAYFISH, LOBSTERS, SPIDERS, AND INSECTS 133 



surface, thus stopping more flow and the wound soon 

 heals. A craj'fish ^\•ith (jiie claw smaller than the other is 

 occasionally found. The smaller claw is simply replacing 

 one that has l:>een lost. 



Habitat and habits. — Crayfishes are widely distributed 

 over the United States except in parts of New England and 

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

 many springs. 8ome species live in holes dug deep enough 

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

 these burrows, traced to its l^ottom in digging a mine shaft, 

 extended straight downward for twenty-six feet. 



Some of the l^urrowing species build mud chinuieys about 

 the entrances to tlieir l)urrows. Those that live in water 

 usually remain close to tlie l^ottom, where they hide during 

 the day beneath stones, sticks, or plants. 



Methods of protection. — The crayfish often escapes from 

 its pursuer ui the cloud of sediment stirred u]) 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 liottom 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 m color and l^lends so nicely 

 with surrounding ol)jects that it is hard to distinguish. 



Molting of the crayfish. — During the growth of this 

 animal it sheds its hard, thick coA^ering from time to time. 

 It is evident that the Ixjdy 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 



