The Food of Fresh-Water Fishes. 461 



Mollusks made one fifth of the entire amount of the food, 

 — more than one half of them Sphaeriiim. This genus made 

 nearly all the food of a large group taken from the Illinois River 

 at Pekin in September, 1882, and also of two other specimens 

 taken in the Illinois River at Peoria in October, 1887. Uni- 

 valves were rarely preseut, amounting to only two per cent, 

 of the food, taken however by eight of the specimens. These 

 included the usual forms — Valvata, Melantho, and Amnicola, 

 together with two or three specimens of Physa. Examples of 

 Pisidiura were rarely noted, and two had eaten Unios. 



Nearly a fourth of the food was insects, mostly aquatic, 

 and the larger part of them larvae of Diptera — especially Chi- 

 ronomus and Corethra. Seven per cent, of Neuroptera larvai 

 (Hexagenia, Libellulid^, and Phryganeidae), together with a 

 miscellaneous assortment of terrestrial species, complete the ac- 

 count of the insect food. 



The Crustaceans (thirteen per cent.) were nearly all cray- 

 fish, traces of Diaptomus, Leptodora, Chydorus, etc., appearing, 

 however, in here and there a specimen, and the little am- 

 phipod AUorchesfes dentata, appearing in three. A leech and 

 a nematoid worm occurred, each in one. 



It will be seen that the food of this species was very widely 

 distributed, being composed about equally of fishes, mollusks, 

 aquatic insects, and vegetable structures, with a very considera- 

 ble ratio (thirteen per cent.) of crustaceans added. 



Two smaller specimens, two and three and a half inches 

 respectively, had fed chiefly on ephemerid and Chironomus 

 larvai, small crayfish, and Asellus. To these were added Corixa 

 tumida, Cyclops, Daphnia, filaments of Spongilla, Chydorus, 

 Scapholeberis mucronatus. a few Diatoms, and traces of fila- 

 mentous Algse. 



ICTALURUS MARMORATUS, Holbrook. MaRBLED CaT. 



This species is scarcely more than a deep-water variety of 

 the common bull-head (/. nebidosKs), distinguished only by the 

 color. It occurs in the larger rivers of the State and their im- 

 mediate tributaries, but nowhere, so far as I know, in stagnant 

 waters. Our thirteen specimens were all from Peoria and 

 Havana, taken in August, October, and November of 1878 and 

 1887. 



