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four per cent. respectively. Four of the nine had eaten small quan- 
tities of a small amphipod crustacean, Allorchestes dentata, which is 
very abundant north, and has, in fact, about the same distribution 
‘in the State.as the perch itself. The Cladocera were chiefly Daph- 
‘niide (twenty-seven per cent.) including Daphnia pulex, L., Simoce- 
phalus americanus, Birge, and Bosmina longirostris. Specimens of 
Chydorus .and Pleuroxus made up the principal part of the nine 
per cent. of Lynceide 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 Hemiptera (twelve per 
-eent.) and Neuroptera (eighty-eight per cent.). The Hemiptera were 
all Corira alternaia, and the Neuroptera were nearly all the ex- 
tremely common larva of one of our most abundant Maytlies (Palin- 
genia bilineata, Say). Uarve of small dragon-flies (Agrionini) made 
five per cent. of the food. The simplicity of the food of these speci- 
mens is probably due partly to the fact that they were all caught 
at the same time and place, and partly to the wintry weather when 
they were taken. 
_ Four specimens, from three and a half to four inches: long, rep- 
resenting two localities and dates, had eaten a greater variety of 
articles; the food, in fact, now closely approaching that of the 
‘adult. Forty-five percent. of the food was insects,—chiefly larve 
‘of May-flies—and fifty-five per cent: Crustacea,—chiefly Amphipoda 
‘and Cladocera. Other insect elements were larve of Chironomus, 
‘six per cent., and four per cent. Corixas. The Cladocera were all 
‘Daphnia, and the Amphipoda were Allorchestes dentata. A single 
‘specimen from Long L., near Pekin, Ill., had eaten an isopod 
‘crustacean (Asellus). Cypridide, another family of minute crusta- 
‘ceans, formed eight per cent. of the whole food of these specimens. 
Food of the Adult. 
The thirty mature individuals may best be treated in two groups, 
‘the first from streams and the second from Lake Michigan.. 
Four of the first group were bought in the Chicago market, in 
‘March, 1880; six were taken from the upper Fox, in May; four 
were from Calumet R. at South Chicago, taken in August, 1878, 
| ped four were caught in October of that year, from the Illhnois at 
eorla. 
. We notice, first, the entire disappearance of EKntomostraca, which 
‘are thus seen to be food proper to the young. We next observe the 
appearance of mollusca (nineteen per cent.), which are evidently no 
‘insignificant food resource of the species. Unio, Cyclas, Succinea, 
'Physa heterostropha, Say, and Valvata tricarinata, Say, are the mol- 
‘lusks recognized. Notwithstanding the lack of EKntomostraca, Crus- 
‘tacea are the most important resource of these river specimens,— 
‘constituting forty-eight per cent. of their food. Crawfishes (Cam- 
‘barus) and our common little fresh-water shrimp (Palemonetes eailipes, 
St.) compose ten per cent. of the whole; the previously noticed 
‘Allorchestes amounts to fifteen per cent., and species of Asellus, and 
“Mancasellus tenax to twenty-three per cent. The Mancaselli were all 
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