No. 545] THE BIOLOGY OF THE CRAYFISH 289 



and lias also found garter snakes, Eutcenia sirtalis, in 

 the holes of Cambarus monongalensis. 



In the laboratory and in the field I have found that the 

 common box turtle catches many crayfish. 



Many birds, including the eagle, king-fisher, wild ibis 

 and turkey, have been observed with crayfish in their 

 claws ; or the remains have been seen at the nests. 



Crayfish as Injurious Creatures. 



The river species do not especially injure human in- 

 terests except in occasionally capturing a few toads, fish 

 and frogs, but the burrowing species are cited by Ort- 

 mann (38) as being very injurious, especially in the low- 

 lands of Pennsylvania, Maryland and West Virginia. 



They make mud piles which clog harvesting machines, 

 and are considered by the farmers in Maryland as such 

 pests that it is common to throw unslacked lime over the 

 fields in order to kill the unwelcome tenants. 



West Virginia farmers claim that the crayfish de- 

 stroy crops of buckwheat, corn and beans by eating the 

 young sprouts. 



Great damage is done by the burrowing species Cam- 

 barus dio genes, in burrowing into dams on ponds and 

 reservoirs, one notable instance being the levees of the 

 Mississippi (38). 



To destroy crayfish it is customary to throw un- 

 slacked lime over the fields, or to pour carbon bisulphide 

 into the holes, or to drain the infested area. 



None of these measures is efficacious, the first two 

 methods being impracticable on account of the difficulty 

 in reaching the bottom of the burrow and the second, 

 simply lowering the water level, only delays matters a 

 little. 



Value of the Crayfish. 

 At the present time, with the lobster fishery in a state 

 of decline, it seems as if the crayfish could be profitably 

 substituted for its larger cousin. 



