330 THE CRAYFISH AND THE ARTHROPODA 



In some localities, as along the lower Mississippi River, crayfish 

 become a pest by burrowing into earthen dams and levees and 

 starting leaks that rapidly enlarge. In Pennsylvania, Maryland, 

 and West Virginia, one of the burrowing species is reported as 

 being very annoying in lowland fields. The " chimneys " of mud 

 excavated and placed at the air holes of the burrows clog the 

 harvesting machines; and farmers claim that the crayfish come 

 to the surface and destroy the young sprouts of buckwheat, corn, 

 and beans. In attempts to combat them, it is customary to throw 

 unslacked lime upon the fields, to pour carbon bisulphide into the 

 air holes, or to drain the infested areas. None of these measures 

 is efficacious, since the first two do not reach the animals in the 

 water of their burrows while drainage merely lowers the water 

 level and thus only abates the nuisance until the animals reestab- 

 lish themselves in deeper burrows. 



With the decline of the lobster and shrimp supply of the sea- 

 shore, crayfish will probably assume increasing importance as an 

 article of food. They have long been esteemed as delicacies in 

 other countries, and in the United States there are many cities 

 having a considerable foreign population that consume quantities 

 of crayfish. Many of our streams furnish almost unlimited oppor- 

 tunities for " crayfish farming " such as has been carried on in 

 Europe for years. Or the clear streams of less settled districts, 

 like the Ozark region of Missouri and Arkansas, may yield a nat- 

 ural supply of clean and appetizing appearance. The small boy, 

 who now boils " crawdads " in a tin can by the side of a stream, 

 may, when he grows to be a man, pay a fancy price for them at a 

 city restaurant. Even at the present time, " crawfishing " is an 

 important item in the fishing industry of many localities in the 

 United States. 



Internal Organization. — The appearance of the internal 

 organs of the crayfish bears little resemblance to that of the 

 earthworm. The nervous and digestive systems are similarly 

 related, but there is no true coelome that is clearly recognizable, 

 and the circulatory, excretory, and reproductive systems differ 

 so widely that few comparisons can be instituted. Beneath the 

 skeleton is an ectodermal epithelium similar to that of the earth- 

 worm, which, in turn, is underlain by the muscles and connective 

 tissue. Between these muscles are cavities, so extensive that they 

 might be mistaken for parts of a ccelome, but in reality they are 



