REPORT OF THE STATE ENTOMOLOGIST I907 181 



Diatoms in a considerable variety, filaments of Cyanophyceae and 

 Desmids (among which the genera Closterium and Desmidium were 

 recognized). All of these occurred sparingly and may very well 

 have been taken along with the disintegrating stems and leaves of 

 the higher plants. * 



This last mentioned material was in four cases a mass of leaf 

 fragments of a slender species of river weed (Potamogeton) and 

 in three other cases it contained (once in excess) remains of the 

 petiole of the yellow water lily ( N y m p h a e a a d v e n a) . These 

 were recognizable by the well preserved internal hairs from the 

 walls of the air chambers. Such food stuff was, of course, very 

 abundant in this place. There may have been a good many other 

 plants present, indeed I have no doubt there were some others ; for 

 a form of tracheids quite unknown to me, derived from the vas- 

 cular bundles of some other seed plant, occurred three times. 



These were the predominating elements of the food, however; 

 they show that at this time and place Chrosomus was a vegetable 

 feeder. Apparently this singularly beautiful and hardy little fish 

 is one that can be introduced safely into private ponds. 



I hasten to place beside the foregoing, the results of a more ex- 

 tensive study of the food of this fish, made in quite a different 

 situation, and so different in kind that they will teach the neces- 

 sity of great care in reaching conclusions as to what fishes eat. 



A former pupil of mine, Mr Warren H. Ferguson, studied the 

 food and feeding habits of Chrosomus in Pettibone creek, near 

 North Chicago, 111., in 1904. The place has since become the site 

 of the United States Naval training station of the Great Lakes. 

 The creek was then a beautiful little stream flowing through fine oak 

 woods with here and there a deep shadowy pool and with inter- 

 vening stretches of flowing water. It was one of my favorite 

 collecting grounds when I lived at Lake Forest, 6 miles distant. 

 A few other fishes live in the stream; the horned dace, a little 

 stickleback, several darters, and very small suckers, but none were 

 so abundant as Chrosomus; and only the darters that live in the 

 riflies were as constantly to be found in a given place. 



The forage ofifered by this creek was very different indeed from 

 that of Old Forge pond. Here there were no standing aquatics 

 and no unattached filamentous algae. Rocks and sticks exposed 

 in the riffles were draped with two beautiful sessile algae (D r a - 

 pernaldia plumosa and a species of Cladophora) . The out- 

 let of ^very pool was choke4, an4 ^very obstruction was pov^r^d 



