42 The Food of Fishes. 



from the following ; and, indeed, sportsmen do not always 

 recognize the difference. 



I have examined the food of thirty-one specimens of 

 this species, fourteen of which were adults, and the re- 

 mainder young, of different ages. 



Food of the Yo ung . 



The first group, consisting of five specimens under one 

 inch in length (ranging from | to fin.), represents three 

 localities, — Crystal Lake, in McHenry county, the Illinois 

 River at Pekin, Tazewell county, and the same stream at 

 Starved Rock, in La Salle county. They were taken in 

 June, July and August of three different years. It is evi- 

 dent, therefore, that the common features of their food 

 can not well be attributed to any other fact than their sim- 

 ilar size. 



The entire food of these fishes consisted of small Crus- 

 tacea, — all Entomostraca except seven per cent., eaten by 

 a single fish, which consisted of the very young of some 

 undetermined amphipod, — probably Allorchestes. Eighty- 

 seven per cent, of the food was Cladocera, principally 

 BosTnina longirostris^ Miill. Simocephalus amiericanus,, 

 Birge, was also an important element ; and traces appear 

 of Chydorus, Pleuroxus and Eurycercus lamellatus. About 

 six per cent, of Cyclops had been eaten. 



In the food of the next group — six specimens, from \\ 

 to 1^ inches long — minute fishes and insects appear. The 

 fishes (twenty-nine per cent.) were not large enough to 

 determine. The insects (forty-six per cent.) were mostly 

 young water-bugs (Corixa), the principal part of which 

 were about half grown. The adults were all Corixa tumida^ 

 Uhl. The Entomostraca drop to twenty-five per cent., 

 about equally Cladocera and Cyclops. Among the former 

 were many specimens of Simocephalus americamis^ and a 

 few of the rare and curious Leptodora mentioned in a pre- 

 vious palmer.* The specimen in which this was found was 

 taken at Peoria, in June, 1878. All of this group were 

 taken from the Illinois River, but at different places and 

 dates. Some, taken at the same place and time as others 



*See Bull. No. 2, 111. State Lab. Nat. Hist., p. 88. 



