502 



REPORT OF THE 



The end of an investigation of this subject is very far in the distance and yet the 

 value of such work can hardly be questioned by one who compares the money 

 expended in the rearing of fish with the amount necessary for such study. 



The early researches of Prof. S. A. Forbes, State Entomologist of Illinois, con- 

 vinced him that insects comprise the most important portion of the food of adult fresh 

 water fishes, they furnishing 40 per cent of all the food of the specimens which he 

 examined. He found the principal insectivorous fishes to be the smaller species whose 

 size and food structure when adult unfit them for the capture of Entomostraca and 

 yet do not bring them within reach of fishes or moUusca. Some of these fishes have 

 peculiar habits which render them specially dependent upon insect life. The little 

 minnow, Phcnacobiiis, which according to his studies depends for nearly all of its 

 food upon insects (98 per cent), seeks for them in running Avater. Next come the 

 pirate perch, ApJiredoderus (91 per cent), then the darters (87 per cent), the croppies 

 (73 per cent), halfgrown sheepshead (71 per cent), the shovel fish (59 per cent), the 

 chub minnow (56 per cent), the black warrior sunfish {CliaenobryttiLs) and the brook 

 silversides (each 54 per cent), and the rock bass and the Cyprinoid genus Notropis 

 (each 52 per cent). He found insects wholly or nearly absent from the adult dietary 

 of the burbot, the pike, the gar, the black bass, the wall-eyed pike, the great river 

 catfish, from that of the hickory shad and the mud-eating minnows (the shiner, the 

 fathead, etc.). He found, however, that the larger fishes all go through an insec- 

 tivprous 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, how- 

 ever, do not seem to pass through this stage, but adopt the limnophagous habit as 

 soon as they cease to depend upon Entomostraca. Terrestrial insects dropping into 

 the water accidentally or swept in by rains are also diligently sought after and 

 •largely depended upon by several species, such as the pirate perch, the brook min- 

 now, the top minnows or killifishes [Cyprinodoiits), the toothed herring and several 

 Cyprinoids {Seiiwtiiiis, Pimephales and Notropis). 



He also found that among aquatic insects slender dipterous larvae belonging 

 mostly to Chironoimis, Co7-cthea and allied genera were of remarkable importance, 

 making in fact nearly one-tenth of the food of all the fishes studied. They were 

 most abundant in PJienacobius and Etlicosloma, which genera have become especially 

 adapted to search for these insect forms in shallow rocky streams. Next they were 

 found most generally in the pirate perch, the brook silversides and the sticklebacks, 

 in which they averaged 45 per cent of the stomach contents. They amounted to 

 about one-third of the food of fishes as large and important as the red horse and the 

 river carp and made nearly one-fourth of that of 51 buffalo fishes. They appear 



