52 The Food of Fishes. 



September and October, at Pekin, Peoria and Mackinaw 

 Creek, Woodford county. Neither locality nor date seems 

 to have made any marked difference in their food, the 

 principal elements of which were Entomostraca and Ohi- 

 ronomus larvae — fifty-seven per cent, and thirty-seven 

 per cent, respectively. 



A few water-spiders (Hydrachnidae) and undetermined 

 Amphipoda were the other items. The Entomostraca were 

 all Cyclops (twenty per cent.) and Cladocera {Simoceph- 

 alus vetulus and aniericanus^ Bosmina longirostris and 

 Pleuroxus dent at us ) . 



Nine specimens, between two and three inches long, 

 were caught at the same times and places as the preceding, 

 except that one specimen from Mackinaw Creek was taken 

 in June, and one taken in September was from Clear Lake, 

 Kentucky. The greater size of these specimens was indi- 

 cated by the appearance of a few Neuroptera larvae in the 

 food — eight per cent. In other essential respects, the food 

 was like that of the foregoing group. One specimen had 

 eaten largely of water-mites and another of Cyprids (fifty 

 per cent. ) , and these elements have therefore greater prom- 

 inence in the averages. Chironomus larvae and Entomos- 

 traca now sum up eighty-one per cent. 



In the third group of the young, consisting of seven fishes, 

 between two and three inches long, the Chironomus larvae 

 remain about as before (thirty per cent.), Corixas appear 

 (twenty-five per cent.) and Neuroptera larvae rise to four- 

 teen per cent. Entomostraca now fall away to a trifle, and 

 larger percentages of Amphipoda appear. Single fishes 

 had eaten the larvge of a Gyrinid beetle, portions of the 

 Polyzoan Pectinatella magniUca.* Leidy, and an earth- 

 worm, — the latter probably nibbled from some fisherman's 

 hook. 



*This animal forms the large, translucent masses found in midsummer 

 in the slow water along the margins of the Illinois River and elsewhere 

 throughout the state, usually collected about a stick or a stem of a water- 

 weed. They vary from the size of a walnut to that of half a bushel. 

 The fragments were easily recognized by the peculiar form and armature 

 of the winter eggs (statoblasts), which are discoidal and bordered with a 

 row of sbnder double hooks, shaped something like an anchor. 



