132 



Order, Isopoda. 

 Oniscidje. 



Porcellio rathkei Brandt. 

 Asellidse. 



Asellus tomalensis Harford. 



The economic importance of tile smaller Crustacea is well known 

 They form one of the most important food silpijly links between the lower 

 plants and animals on the one side and the higher animals on the other. 

 A small minnow about one inch long was kept for some time and fed on 

 Amphipoda (Hyalella knickerbockeri ) . A small darter hatched from the 

 egg and cared for by Mr. W. I. Lower was fed ou Entomostraca, principally 

 Ostracoda, until it was eighty-seven days old and was about three-eighths 

 of an inch long. 



As parasites the small Crustacea frequently cause great mortality 

 among fishes, but so far only one parasitic form has been found in Winona 

 Lake and that in extremely small numbers on the gills of the Black Bass 

 (Micropterus salmoides). Examination of other fish and of the clams in 

 The lake failed to reveal other parasitic Crustacea. 



Three species of crayfish were found. Camhants propinquiis was 

 abundant in the streams flowing into the lake and also in the outlet, but 

 was extremely scarce in the lake. Cambarus diogenes and Cambarus im- 

 mimis were found only in burrows along the shore and along the edge of 

 the streams and in the adjacent low ground. The burrows are from two 

 to three feet deep and contain six to eight inches of water at the bottom. 

 \^'here the soil is homogeneovis they extend obliquely downward in almost 

 a direct course, but in the presence of stones and other obstructions they 

 wind about sometimes to a considerable extent. In digging the holes the 

 crayfish work head downvrard and bring the earth up between the chebe 

 and the first pair of walking feet and deposit it by the aid of the. second 

 pair of walking feet. Attempts were made to get the burrowers out of 

 their holes by pouring strong salt solution and also formalin into them. 

 But the crayfish would die before tliey would come to the surface. Traps 

 at the surface were also resorted to without success and the only practical 

 method of obtaining them was by means of a ditching spade which re- 

 quired no small amomit of labor. 



While the crayfish were always found in shallow water, under and 

 among stones and sticks or in burrows, it was found that they could live 



