26 
The Food of Fishes. 
Six specimens of Etheo stoma flabellare var. lineolata, 
from four localities, had eaten sixty-one per cent, of Chi- 
ronomus larvae, twenty-seven per cent, larvae of small 
ephemerids, and twelve per cent, of Copepoda (Cyclops). 
Boleichthys elegans , found only in the southern part of 
the State (three specimens examined), had eaten only 
dipterous larvae (thirty-seven per cent.) and ephemerid 
larvae (sixty- three per cent.). This is a larger, heavier 
species than most of the others, and, therefore, like 
Alvordius, prefers ephemerids to gnats. 
Last and least comes Microperca punctulata , repre- 
sented by nine specimens from four localities in northern 
Illinois. This smallest of the darters shares with Per- 
cina, the largest, the peculiarity of a large ratio of crus- 
tacean food, which made up sixty-four per cent, of the 
total. The principal kinds were Cyclops, Chydorus, young 
Gammarus fasciatus, Say, and young C rang onyx gracilis, 
Smith. The remaining elements were Chironomus larvae 
(thirtv-four per cent.) and a trace of ephemerids (two 
per cent.). 
It will be seen that the family, taken as a whole, divides 
into two sections, distinguished by the abundance or de- 
ficiency of crustacean food. This is easily explained by 
the fact that Percina and Microperca range much more 
freely than the other genera, being frequentlv found 
among weeds and algae in comparatively slow water with 
muddy bottom, while the others are rather closely con- 
fined to swift and rocky shallows. 
In discussing the food of the whole group, taken as a 
unit, it may best be compared with the food of the young 
of other percoids. It is thus seen to be remarkable for 
the predominance of the larvae of Chironomus and small 
Ephemeridae — the former of these comprising forty-four 
per cent, and the latter twenty-three per cent, of the 
whole food of the seventy specimens. In young black bass 
(Micropterus pallidus), on the other hand, the averages 
of nine specimens, ranging from five-eighths inch to one 
and a half inches in length, were, in general terms as fol- 
lows: Cladocera forty-two per cent., Copepoda seven 
per cent., young fishes twenty per cent., Corixa and young 
