484 Illinois State Laboratory of Natural Uistorij. 



horse and the river carp, and made nearly one fourth that of 

 fifty-one buffalo fishes. They appear further in considerable 

 quantity in the food of a number of the minnow family (No- 

 tropis, Pimephales, etc.), which habitually frequent the swift 

 water of stony streams, but were curiously deficient in the 

 small collection of miller's thumbs (Cottidfe) which hunt for 

 food in similar situations. The sunfishes eat but few of this 

 important group, the average of the family being only six per 

 cent. 



Larvae of aquatic beetles, notwithstanding the abundance 

 of some of the forms, occurred in only insignificant ratios, but 

 were taken by fifty-six specimens, belonging to nineteen of the 

 species, — more frequently by the sunfishes than by any other 

 group. The kinds most commonly captured were larvse of 

 Gyrinida3 and Hydrophilidee; whereas the adult surface beetles 

 themselves (Gryrinus, Dineutes, etc.) — whose zigzag-darting 

 swarms no one can have failed to notice — were not once 

 encountered in my studies. 



The almost equally well-known slender water-skippers (Hy- 

 grotrechus) seem also completely protected by their habits and 

 activity from capture by fishes, only a single specimen occurring 

 in the food of all my specimens. Indeed, the true water bugs 

 (Hemiptera) were generally rare, with the exception of the 

 small soft-bodied genus, Corisa, which was taken by one 

 hundred and ten specimens, belonging to twenty-seven species, 

 — most abundantly by the sunfishes and top minnows. 



From the order Neuroptera fishes draw a larger part of 

 their food than from any other single group. In fact, nearly 

 a fifth of the entire amount of food consumed by all the adult 

 fishes examined by me consisted of aquatic larvas of this order, 

 the greater part of them larvae of day flies (Ephemerida?), prin- 

 cipally of the genus Hexagenia.* These neuropterous larvae 

 were eaten especially by the miller's thumb, the sheepshead, 

 the white and striped bass, the common perch, thirteen species 

 of the darters, both the black bass, seven of the sunfishes, the 

 rock bass and the croppies, the pirate perch, the brook sil- 

 versides, the sticklebacks, the mud minnow, the top min_ 



* The winged adults of this and related genera are often called 

 '' river flies " in Illinois. 



