156 Illinois State Laboratory of Natural History. 



washed upon the shores at times of higher water. The 

 definite grassy margins also favored water-beetle life, as 

 was the case at Station D, which became very similar to 

 the west shore of C as the river fell and the current 

 nearly disappeared. 



Station B and the east shore of Station C, also 

 belonging to this group, located on the east shore of 

 Quiver Lake, introduce a new element— the belt of satu; 

 rated sandy shore, uniform in temperature, coated with 

 algal growth, and teeming with life, including vast num- 

 bers of Asellus and Garamarus and an abundance of 

 dipterous larvse. Leeches and spring-tails (Podura and 

 Isotoma) were unusually common. 



At the upper station, B, the surfaces of bare reeking 

 mud were inhabited b}'^ soldier-fly larvse of the genus 

 Stratiomyia. The little hollows produced here by the 

 tramping of cattle quickly filled with water, and in these 

 hollows, as well as in similar protected depressions along 

 margins everywhere, the mosquito larvse were noticeably 

 abundant in due season, occurring also less commonly 

 in open pockets in thick floating vegetation. Lack of a 

 suitable food plant prevented the occurrence of aquatic 

 caterpillars. 



Station E is like the west shore of C, except that a 

 great reduction in the quantity of vegetable life cor- 

 respondingly reduces the number of the more delicate 

 shallow- water forms. There is a considerable amount 

 of sticks and rubbish, and the harder-shelled water- 

 beetles and water-bugs are therefore more numerous. 

 Gyrinidae in small schools also appeared. 



The most aberrant station of all, Phelps Lake^ 

 the bottom of which was almost as bare as a floor, was 

 apparently equally destitute of life. Close search, however, 

 revealed abundant Corisidse in the deeper water; Berosus 

 and other small water-beetles in the shallows hidingunder 

 fallen leaves; Notonecta about a fallen branch in the 

 water; and Heteroceiidae swarming over the mud at the 

 margin, in their tiny mole-like burrows. 



