The Food of the Smaller Fresh- Water Fishes. 73 



Four-fifths of the food of the genus consisted of animal matter, 

 nearly one-quarter being Mollusca, including Physa, IManorbis, 

 and J\(/c((tt( sincenf. Insects make less than half, and nearly 

 half of these were of terrestrial origin. Chironomus larv;e, usually 

 so abundant in the food of insectivorous minnows, occurred here 

 in only trivial quantity. Specimens of Philhydrus were eaten by 

 three of the fislies. Corlxa alt.ei')iat<i amounted to live per cent, 

 of their food, Agrion larva' and case worms (Leptocerida') to two 

 per cent. Crustaceans were only four per cent, of the whole, 

 partly Amphipoda, but chiefly Entomostraca. The vegetable 

 food (sixteen per cent.) was chiefly Wolffia, taken by five of the 

 specimens from southern lakes. Ten individuals had, however, 

 eaten filamentous Algte. 



A' a VI ni a r y . 



Tiie only essential diflerence between these two genera exhib- 

 ited l)y the specimens studied, is th(; much larger ratios of terres- 

 trial insects captured by Zygonectes, this genus eating nearly 

 twice as many as the otlier. This fact is possil^ly related to the 

 surface-swimming habit already mentioned, but is more likely due 

 to the smaller bodies of water in which the top minnows occur. 

 Concerning the food of the family as a whole, the salient charac- 

 ters are the presence of a considerable quantity of vegetable food, 

 (abovit twenty per cent.) the occurrence of fifteen per cent, of Mol- 

 lusca, the insignificant quantity of Crustacea eaten (four per cent.), 

 and the importance of terrestrial insects as a source of support. 



FAMILY UMBRID^. 



Umhka limi, Kirt. ^luj) Minnow. 



This species, the only one of its family in Illinois, is very abund- 

 ant in muddy ponds and ditches, and has been collected by us 

 from Lake to Union Counties. 



The intestine is short, less than the body in length; the gill- 

 rakers are thick and rather long, about one-half the l(Migth of the 

 filaments, and the pharyngeal apparatus is wholly insignificant. 



Ten specimens were studied, from six localities, all from South- 

 ern Illinois but one, Avhich was taken in Calumet River. Vegeta- 

 ble food amounted to forty per cent., chiefly Wolfiia, eaten by 



