88 The Food of the Synaller Fresh - Water Fishes. 



Phenacobius sc-opiferus, Cope. 



This species occurs not very abundantly tliroughout the State, 

 from Galena to extreme Southern Illinois. It has been taken by us 

 almost invariably in swift and shallow streams. 



The mouth is small and inferior, provided with fleshy lips 

 somewhat resembling a sucker's in form. The gill-rakers and 

 pharyngeal teeth are as usual in this group and the intestine is 

 contained once and a half in the length of the head and body. 



The nine specimens studied were from five localities, distributed 

 from Galena to Union county. The food was almost purely insects, 

 only two per cent, being unrecognized vegetation. Seventy-six per 

 cent, consisted solely of Chironomus larvte, and six per cent, of 

 case-worms. Adult chironomids, taken by two of the specimens, 

 amounted to two per cent. A few Cyclops found in a single 

 specimen were the only Crustacea eaten by these fishes. 



The peculiar character of this food, almost precisely that of a 

 darter, is evidently related to the habitat of the fish.* 



Semotilus corporalis, Mitch. Chub. 



This is a widely distributed and very abundant fish, perhaps the 

 commonest species in the small creeks; but is less abundant in 

 lakes and ponds. 



The head and mouth are unusually large for a minnow; the 

 intestine is six-sevenths the length of the head and body; and the 

 gill-rakers are of the usual form. 



Twenty-two specimens, from widely separated localities, give a 

 ratio of seventy-six per cent, of animal food, four per cent, being 

 fishes (partly Cyprinidae), thirteen per cent, vegetation, and three 

 per cent, worms. Insects make a little over half the whole, about 

 one-half of them terrestrial. No Chironomus larvte were found 

 in the food of these fishes. Of neuropterous larvae only a trace 

 occurred, aqviatic Coleoptera were noted in two, and Corixain one. 

 Grasshoppers (Acrididae) made ten per cent, of the whole and were 

 eaten by three of the specimens. Five had taken crawfishes, 

 which made twelve per cent, of the entire food. No Entomostraca 

 were noted, with the exception of one per cent, of Cyclops 



*For a discussion of this matter, see Bulletin 3 of this series, p. 25. 



