INSECTS IN RELATION TO OTHER ANIMALS 219 



Insects in Relation to Fishes. Insects constitute the most im- 

 portant portion of the food of adult fresh water fishes, furnishing forty 

 per cent, of their food, according to Dr. Forbes, from whose valuable 

 writings the following extracts are taken. 



"The principal insectivorous fishes are the smaller species, whose 

 size and food structures, when adult, unfit them for the capture of Ento- 

 mostraca, and yet do not bring them within reach of fishes or Mollusca. 

 Some of these fishes have peculiar habits which render them especially 

 dependent upon insect life, the little minnow Phenacobius,-for example, 

 which, according to my studies, makes nearly all its food from insects 

 (ninety-eight per cent.) found under stones in running water. Next are 

 the pirate perch, Aphredoderus (ninety-one per cent.), then the darters 

 (eighty-seven per cent.), the croppies (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 

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

 the rock bass and the cyprinoid genus Notropis (each fifty- two percent.). 



"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 and the mud-eating minnows (the shiner, the 

 fathead, 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 \vith the gar and the pike, or molluscs, 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 de- 

 pend 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 killifishes (cyprinodonts) the toothed herring and several 

 cyprinoids (Semotilus, Pimephales 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 Phcnacobius and Ethcostoma, 

 which genera have become especially adapted to the search for these 

 insect forms in shallow rocky streams. Next I found them most gener- 



