Food Relations of Fresh-Water Fishes. 483 



water. Next are the pirate perch, Aphredoderus (ninety-one 

 per cent.), then the darters (eighty-seven per cent.), the crop- 

 pies (seventy-three per cent.), half-grown sheepshead (seventy- 

 one per cent.), the shovel fish (fifty-nine per cent.), the chub 

 minnow (fifty-six per cent.), the black warrior sunfish (ChaBno- 

 bryttus) and the brook silversides (each fifty-four per cent.), and 

 the rock bass and the cyprinoid genus Notropis, (each fifty-two 

 per cent.) 



Those which take few insects or none are mostly the mud- 

 feeders and the ichthyophagous species, Amia (the dog-fish) 

 being the only exception noted to this general statement. Thus 

 we find insects wholly or nearly absent from the adult dietary of 

 the burbot, the pike, the gar, the black bass, the wall-eyed 

 pike, and the great river catfish, and from that of the hickory 

 shad 1 and the mud-eating minnows (the shiner, the fat-head, 2 

 etc.). It is to be noted, however, that the larger fishes all go 

 through an insectivorous stage, whether their food when adult 

 be almost wholly other fishes, as with the gar and the pike, or 

 mollusks, as with the sheepshead. The mud-feeders, however, 

 seem not to pass through this stage, but to adopt the 

 limophagous habit as soon as they cease to depend upon Ento- 

 mostraca. 



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 killifishes (cyprinodonts), 

 the toothed herring and several cyprinoids (Semotilus, Pimeph- 

 ales, and Notropis). 



Among aquatic insects, minute slender dipterous larvae, 

 belonging mostly to Chironomus, 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 Etheostoma, which genera have become 

 especially adapted to the search for these insect forms in shal- 

 low 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 



1 Dorosoma. 2 Pimephales. 



