CRAYFISH, LOBSTERS, CRABS, SHRIMPS, ETC. 113 



Crayfish, or crawfish, as they are more commonly called, 

 are found in most fresh water ponds and streams. The 

 common species in the eastern United States belong to the 

 genus Cambarus, those on the Pacific Coast to the genus Astacus. 

 Some species live in holes in the ground, digging deep enough 

 to reach water, or at least considerable moisture. The earth 

 that is removed in digging the burrows is sometimes built up 

 to form short chimneys above the ground. This burrowing 

 habit is often the cause of serious damage to the levees along 

 the rivers, particularly along the Mississippi River. In the 

 southern United States crayfish often occur in such 

 numbers that they become important pests in the corn and 

 cotton fields. In badly infested areas there may be as many 

 as 10,000 or 12,000 holes to the acre. From these holes the 

 crayfish issue in the evenings or on rainy mornings and feed 

 on the young tender plants. They may be easily killed by 

 placing a little carbon bisulphid in each hole. 



In some sections of the country crayfish are used for food 

 and are considered a great delicacy, those on the west coast, on 

 account of their size, being particularly in demand. Recent 

 attempts have been made to introduce these larger species 

 into waters where only the smaller ones occur naturally. 

 In Europe the crayfish have been used for food for centuries 

 and in France "crayfish farming" has been successfully 

 practiced for many years. 



CLASSIFICATION 



The class Crustacea is divided into two sub-classes, the 

 Entomostraca and the Malacostraca. 



Sub-class Entomostraca. Entomostraca are mostly small, 

 comparatively simple forms with little differentiation of the 

 appendages. Four orders are included in this class. The 

 order Phyllopoda comprises mostly fresh water species with 

 leaf-like appendages. The "fairy shrimps, " common in fresh 

 water pools in the early spring, are among the largest examples. 

 The species of A rtemia, an abundant Phyllopodin salt and brack- 

 ish or fresh water, are of great interest to biologists on account 



8 



