THE CRAYFISH 137 



abortive eyes, but its sense of touch is developed to a mar- 

 velous degree of delicacy. Dr. Hay says that although the 

 crayfishes may be resting quietly on the bottom of a rivulet, 

 it is impossible to capture them with a net. They feel the jar 

 in the water and dart backward with great accuracy to a pro- 

 tecting rock. In general appearance the blind crayfish differs 

 from others chiefly in having an exoskeleton which is so clear 

 that one may see the animal's stomach as a blue mass within, 

 and in being provided with antennae longer than the body. 



Crayfishes are eaten by fish large enough to swallow them, 

 and they in turn catch small fish with great facility, and also 

 insect larvae, snails, tadpoles, and even frogs. They have 

 been known to prey upon each other, and also to eat dead 

 organic matter ; but as a rule they eat plant and animal food 

 in the fresh condition. 



They are protected by their hard shells from the attacks of 

 passing fish. The color of the shell is more effective still, 

 since whatever the color of the bottom, it is closely imitated 

 in the distribution of color pigment in the shell. The usual 

 color is muddy greenish-black ; in ponds where the mud is 

 bluish, the shell is also blue. An account has been written 

 of the crayfishes found in Sandy Lake, Pennsylvania, where 

 the bottom is white marl and clay. All the crayfishes which 

 have been captured in the pond " vary in color from almost 

 pure white to pink, or in some cases to a delicate greenish 

 tint. They are practically invisible when at rest. The fisher- 

 men of the district capture them and use them for bait to 

 catch bass in other lakes where the bottom is of dark mud." 



In America crayfishes seem to be used as food chiefly by 

 the French portion of our population. Possibly the rapid 

 depletion of the lobster fisheries may cause people generally 

 to turn to the lobster's nearest edible relative. In France the 

 crayfish industry is quite extensive, there being many farms 

 on which crayfishes are raised for the market. 



