TJie Food of FrefiJi-Wfifpr Fif^JiPS. 459 



upon insects, a few specimens of Allorchestes dentata and 

 Daphnia being the only other items. Eggs and young of 

 Hexagenia and other ephemerids composed the greater part of 

 the food, Chironomus larvse amounting to about one half as 

 much,* 



ICTALURUS NATALIS, LcS. YeLLOW CaT. 



This species occurs everywhere throughout Illinois, but 

 less abundantly than nebidosns^ and usually in larger streams. 

 It has not been taken by us from ponds and lakes except where 

 these were immediately connected with rivers subject to over- 

 flow. 



The alimentary structures of this species closely resemble 

 those of /. nehulosus^ described under the next head. Twelve 

 specimens were collected from the Illinois River at Peoria, the 

 Fox River at McHenry, and from one of the smaller lakes in 

 northern Illinois, in the months of May, August, October, and 

 November of 1878, 1880, and 1887. 



The food was wholly animal with the exception of a trace 

 of duckweeds (Lemna and Wolffia) taken by a single specimen. 

 The scavenger habit of the species was shown by the food of 

 the Fox River specimen, three fourths of which consisted of 

 the remnants of a dead cat. Fishes made a larger ratio of the 

 food than in the preceding species, amounting to about one 

 third, most of them apparently taken alive. One, however, a 

 sucker, was represented only by the stomach and intestines, 

 doubtless picked up near a fish boat. The gizzard shad, cer- 

 tain Cyprinid*, and undetermined suckers (Catostomatida?) were 

 recognized, four of the twelve specimens having fed wholly or 

 almost wholly upon them. The molluscan food of these speci- 

 mens was insignificant, no bivalve mollusks having been taken 

 by them and only a few Vivipara and Melantho, amounting in 

 all to five per cent. While insects had been eaten by four of 

 the specimens and reached a ratio of thirty per cent., they were 

 practically all Hexagenia larvae, taken in October, 1878 and 

 1887. On the other hand, seventeen per cent, of the food was 

 catfishes, taken by four of the specimens in May and August. 



* A hmt of the winter food is given by six specimens received 

 from the Illinois T?iver i\\ Tfavana, February, 1888, all of which had 

 fed unly u[)oii (liiiouomu.s l;u vie (ir l;ii v;c of Agiion. 



