442 WiscOTisin Academy of Sciences^ Arts^ and Letters. 
tera are dominant in the littoral area^ hence in the region of 
plant food. A third point is indicated^—and that is the ready 
passage from a microphagons diet to any other. Among the 
scavengers can be listed Annelida, Gastropoda, Corethridae, 
and Chironomidae; while among the phytophaga the caddis- 
worms have attained a single dominance. It is indeed surpris¬ 
ing that of phytophagous aquatic groups only the caddisworms 
attain a prominent place in the lake complex; and since even 
caddisworms will readily resort to a sarcophagous method of 
life, the place of plant food in the lake complex becomes minim¬ 
ized as a primary source of food, while emphasized rather un¬ 
expectedly from the viewpoint of waste food. 
B. Fish Food .—The greatest element of surprise of the food 
relations lies in the study of fish food items. These items are 
not linear in their proportions to the available food supply; I 
mean to say that the different groups do not form the same per¬ 
centage of fish food that they form of the lake complex. In the 
way of food fish will naturally choose first the free-living forms, 
secondly plant dingers and crawlers, thirdly burrowers and 
tube-builders. But the depressed and appressed dingers and 
protected types of the shore areas seem to be quite absent. 
The commoner supply of food is formed by the Diptera 
primarily among insects, next to which come Sialis and Hemip- 
tera (the latter in the lake shallows). Along the shore line 
Chironomus lobiferus and C. digitatus are the main source, 
while in the aphytal area Protenthes choreus, Chironomus 
tentans, Corethra, and Sialis infumata are the chief representa¬ 
tives. 
Again, certain faunal types are comparatively rare in fish diet. 
Thus, while Leptocella uwarowii forms practically 90% of 
the caddisworm fauna of the lake, it forms probably less than 
25% of the caddisworm diet of fish, while the whole caddis¬ 
worm diet amounts to hardly more than 2% of the total fish food. 
This proportion is not at all commensurate with their avail¬ 
ability and we have to look elsewhere to account for this dis¬ 
parity. Perhaps it is the secretions which make them less 
agreeable as a diet, although along this line other species and 
the notably repellant Hemiptera form a favorite diet wherever 
available. To me it seems that the length, rigidity, and general 
unwieldiness of the cases play a big part in the selection of this 
particular item; small fish cannot manage the cases at all, while 
