74 Tlic Food of the SiimUer Frc><h - Water Fishes. 



seven of the specimens IVoin Southern Illinois lakes. A consider- 

 able quantity of unicellular Algre was also taken by one. Mol- 

 lusks, eaten by two, were reckoned at five per cent., all Physa. 

 Insects drop to fourteen per cejit., chiefly undetermined larv:e. 

 No terrestrial forms were recoi^nized. Corresponding- to the 

 greater development of the gill-rakers, we find the Entomostraca 

 assuming greater importance in the food. These were reckoned 

 at ten per cent.; three per cent, additional consisting of Oran- 

 go)iijx (jracills. 



FAMILY CYPRINID^ 



This family includes all the fishes properly known as "minnows," 

 embracing, in fact, by far the larger part of the smaller fishes of 

 the State. Both in number and in variety of species it is much 

 the most important family of fresh-water fishes. It includes, in 

 Illinois, about forty species, nearly or quite one-fourth of the 

 whole number known to occur in our territory. They occur in all 

 waters from the Mississippi River and Lake Michigan to the 

 smallest streams and ponds; but are much the most abundant in 

 creeks and rivulets. The species difl'er greatly with respect to 

 their favorite havmts, some aflfecting the principal lakes and larger 

 rivers, others occurring most commonly in clear and rapid brooks, 

 while still others are most frequent in the sluggish and muddy 

 streams of prairie regions. The principal economic interest of the 

 fishes of this family is due to the well-known fact that they fur- 

 nish an important part of the food supply of larger species. 



But little has hitherto been done upon their food in the United 

 States. In fact, I have seen nothing more accurate or comprehen- 

 sive than the following general statement made by Prof. Cope, in 

 his paper on the Cyprinid;^ of Pennsylvania:* 



" These differences of liabit are associated with peculiarities of 

 food and of the structur(^ of the digestive system. Few families 

 of vertebrates embrace as great a variety in these respects as the 

 present one. There are carnivorous, insectivorous, and graminiv- 

 orous genera, which are distinguished as among mammalia, the 

 former by the abbreviation, the last by the elongation of the ali- 



■•■■Trans. Amer. Philosophical Society, Vol. 13, New Series, page 353. 



