282 ENTOMOLOGY 



feeders, however, seem not to pass through this stage, but to 

 adopt the limophagous habit as soon as they cease to depend 

 upon Entomostraca. 



" Terrestrial insects, dropping into the water accidentally 

 or swept in by rains, are evidently diligently sought and 

 largely depended upon by several species, such as the pirate 

 perch, the brook minnow, the top minnows or killinshes 

 (cyprinodonts), the toothed herring and several cyprinoids 

 (Semoiiius, Pirnephales and Notropis). 



" Among aquatic insects, minute slender dipterous larvae, 

 belonging mostly to Chiroiioiiius, Corethra and allied genera, 

 are of remarkable importance, making, in fact, nearly one 

 tenth of the food of all the fishes studied. They are most 

 abundant in Phenacobius and Ethcostoma, which genera have 

 become especially adapted to the search for these insect forms 

 in shallow rocky streams. Next I found them most generally 

 in the pirate perch, the brook silversides, and the stickleback, 

 in which they averaged forty-five per cent. They amounted 

 to about one third the food of fishes as large and important 

 as the red horse and the river carp, and made nearly one fourth 

 that of fifty-one buffalo fishes. They appear further in con-' 

 siderable quantity in the food of a number of the minnow 

 family (Notropis, Pirnephales ; etc.), which habitually fre- 

 quent the swift waters of stony streams, but were curiously 

 deficient in the small collection of miller's thumbs (Cottidae) 

 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 larvae of 

 Gyrinidae and Hydrophilidae ; whereas the adult surface beetles 

 themselves (Gyrinus, Dineutes, etc.) whose zigzag-darting 

 swarms no one can have failed to notice were not once en- 

 countered in my studies. 



