The Food of Fishes. 
Food of the Young. 
Finding that the food of most fishes differs with age, T 
have grouped the young according to size, and averaged 
the food for each group separately — the first group con- 
sisting usually of those under an inch in length, the 
second of those from one to two, etc. 
Two perch under an inch in length had eaten nothing 
but Entomostraca — about equal quantities of Cyclops 
and Daphnias. It was not until the specimens reached an 
inch and a half in length that insects of any considerable 
size appeared in the food. A single smaller fish had eaten 
a few minute larvae of Chironomus, but otherwise the 
food at this age consisted wholly of Entomostraca. 
About thirty-four per cent, of the food of nine speci- 
mens ranging from II to two inches in length consisted of 
insects, and sixty-six per cent, of crustaceans. The only 
insects recognized were the larvae and pupae of Chirono- 
mus (eleven per cent.), small water-bugs — Corixa tumi- 
da, Uhl., C. alternata, Say, etc. (twenty-three per cent.) — 
and a trace of larvae of May-flies (Ephemeridae). The 
Crustacea were chiefly Cladocera and Copepoda — thirty- 
six per cent, and twenty-four per cent, respectively. Four 
of the nine had eaten small quantities of a small amphi- 
pod crustacean, Allorchestes dentata, which is very abun- 
dant north, and has, in fact, about the same distribution 
in the State as the perch itself. The Cladocera were 
chiefly Daphniidae (twenty-seven per cent.), including 
Daphnia pidex, L., Simocephalus americamis, Birge, and 
Bosmina longirostris. Specimens of Chydorus and Pleu- 
roxus made up the principal part of the nine per cent, of 
Lynceidae eaten. The Copepoda were all Cyclops and 
Diaptomus. 
Four specimens two and a half inches long, all taken at 
Peoria in November, 1878 , had eaten nothing but Hemip- 
tera (twelve per cent.) and Neuroptera ( eighty-eight per 
cent.). The Hemiptera were all Corixa alternata, and the 
Neuroptera were nearly all the extremely common larva 
of one of our most abundant May-flies (Paling enia hilin- 
eata, Say). Larvae of small dragon-flies (Agrionini) 
made five per cent, of the food. The simplicity of the 
