150 THE ANIMALS AND MAN 



is found in most fresh-water ponds and streams of the United 

 States west of Massachusetts. Crayfishes may be taken 

 by a net baited with dead fish, or may be caught in a trap 

 made from a box with ends which open in, and baited with 

 dead fish or animal refuse of any sort. They should be 

 brought alive into the schoolroom and kept in a moist 

 chamber. Observe live specimens to see the characteristics 

 of locomotion, and the use of the pincers and the mouth- 

 parts in taking food. 



In meadows where water stands for certain seasons of 

 the year there may be noticed many scattered holes with 

 slight elevations of mud about them. These are mostly 

 the burrows of crayfish. During the dry season the ani- 

 mal digs down until it reaches water, or at least a damp 

 place, where it rests until wet .weather brings it to the sur- 

 face once more. One of these burrows followed in the 

 process of digging a mining shaft extended vertically down 

 to a distance of twenty-six feet, where the crayfish was 

 tucked snugly away. 



The eggs are carried by the female on her abdominal 

 appendages. Previous to laying them she rubs off, with 

 the fifth pair of legs, all the dirt from the appendages and 

 smears them with a sticky secretion. When the eggs are 

 laid, which is during the last of March or April in the Cen- 

 tral States, they are caught on the sticky pleopods, where 

 they remain attached in clusters. After some weeks the 

 young crayfishes issue from the eggs. In general appearance 

 they are not very unlike the adults. They grow very rapidly 

 at this stage. As the animal is enclosed in a hard shell, 

 growth can take place only during the period just following 

 the moult, for the crayfish casts its hard shell periodically, 

 and it is while the new shell is forming that it does its grow- 

 ing. When it moults it casts not only the exo-skeleton, but 

 also the lining of part of the alimentary canal. After the 

 females have hatched their young many of them die in the 



