54 The Food of Fishes. 



of vegetation it contained (thirty-one percent.). A sin- 

 gle 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 

 inquiiiatus^ wire-worms, minute curculios, Cryptocephalus 

 4:-maculatus^ Diabrotica Vl-guUata^ Colorado potato beetles, 

 flea-beetles, plant-bugs (Pentatomidae), crickets (Nemo- 

 bius), locusts, katydids {Phaneroptera curvicauda)^ grass- 

 hoppers and case-flies. 



The vegetable food, as far as determined, consisted of 

 Oeratophyllum, Nais Aexilis and confer void Algae. Frag- 

 ments of Polyzoa were noticed. Coptotomus interrogatus^ 

 Gyrinid larvae,* Tropisteriius lirnhatus and other Hydro- 

 philidae, larval and adult, a large Nepa, larvae of Palin- 

 genia hilineataand other May-flies, of Agrionsand dragon- 

 flies were among the aquatic insects taken. 



The Crustacea were limited to small crawfishes (two per 

 cent.), a trace of Allorche'stes, 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 diff"er- 

 ence of locality and not to difference of time represented 

 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 Entomostraca) ac- 

 cessible 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. 



