54 
The Food of Fishes. 
mollusks (sixteen per cent.), for the number and variety 
of land insects (fifteen per cent.), and for the large 
amount of vegetation it contained (thirty-one per cent.). 
A single small fish — the only one taken by these forty- 
five specimens — was also noticed. 
The mollusks included Planorbis, Physa, Amnicola and 
Vivipara. Among the insects were ants, caterpillars, 
flies, Anisodactylus discoideus and other Harpalids, 
Aphodius inquinatus, wire-worms, minute curculios, 
Crypt ocephalus 4- maculcitus , Diabrotica 12 -guttata, Col- 
orado potato beetles, flea-beetles, plant-bugs (Pentatoin- 
idae), crickets (Nemobius), locusts, katydids (Phane- 
roptera curvicauda) , grasshoppers and case-flies. 
The vegetable food, as far as determined, consisted of 
Ceratophyllum, Nais flexilis and confervoid Algae. Frag- 
ments of Polyzoa were noticed. Coptotomus inter ro ga- 
ins, Gyrinid larvae,* Tropisternus limbatus and other 
Hydrophilidae, larval and adult, a large Nepa, larvae of 
Palingenia bilineata and other May-flies, of Agrions and 
dragon-flies were among the aquatic insects taken. 
The Crustacea were limited to small crawfishes (two 
per cent.), a trace of Allorchestes, and a few Aselli (four 
per cent.). 
On comparing specimens from northern Illinois with 
those taken from the Illinois River in the same month, I 
find that there are no common seasonal food characters, 
and that the differences of food are therefore due to dif- 
ference of locality and not to difference of time repre- 
sented by the groups. Concerning the entire number of 
adults, we can therefore say that their food ranges 
through the whole list of the smaller mollusks, terrestrial 
and aquatic insects, and smaller crustaceans (above En- 
tomostraca) accessible in their localities, and that they 
feed largely on aquatic vegetation. A striking negative 
feature is the almost total absence of fishes in the food — 
a fact which corresponds with the relatively small size 
of the mouth. 
* Several of these little-known larvae were found in the stomachs of 
this species, — some of them in suitable condition for description. 
