42 
The Food of Fishes. 
guish it 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 Young. 
The first group, consisting of five specimens under one 
inch in length (ranging from f 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 LaSalle 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 
cannot well be attributed to any other than their similar 
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 
Bosmina longirostris. Mull. Simocephalus americcnus , 
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 If 
to If 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 anierica- 
nus, and a few of the rare and curious Leptodora men- 
tioned in a previous paper.* 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 
* See Bull. No. 2. 111. State Lab. Nat. Hist., p. 88. 
