200 ILLINOIS STATE ACADEMY OF SCIENCE 



A PRELIMINARY REPORT ON THE VERTICAL 



DISTRIBUTION OF WATER MITES IN 



GREEN LAKE, WISCONSIN 



Ruth Marshall, Rockford College 



While geographical distribution, altitude distribution 

 and distribution according to the character of the bodies 

 of water in which they have been found, have been stud- 

 ied, the vertical distribution of water mites has received 

 little attention. Distribution in the lakes of different 

 elevations has been studied in the Swiss and Scandinav- 

 ian mountain regions. In this country, little has been 

 done beyond systematic work; data on distribution 

 have been confined almost entirely to horizontal distri- 

 bution. In this connection, it is interesting to note that 

 Professor F. C. Baker, in his studies on the life in Oneida 

 Lake, New York, records the hydrachnids at varying 

 depths and for different bottoms in a shallow bay. 



The author has been fortunate enough to receive from 

 Professor Chauncey Juda}^, of the Wisconsin Natural 

 History Survey, some" collections made at different depths 

 in Green Lake, in eastern Wisconsin. This lake is re- 

 markable among lakes in the glaciated plains regions in 

 its great depth, which reaches 230 feet. 



Collections were made in August, 1921, and were in 

 three lots: at depths from the surface to five meters; 

 from five meters to ten meters ; and from ten meters to 

 twenty-nine meters. Thirteen genera were represented, 

 most of them common ones. About three hundred and 

 thirty-five individuals were present ; the species have not 

 yet been fully determined. As was to be expected, the 

 genera were not found in the same ratios as in ordinary 

 collections made by dragging a cone net through the vege- 

 tation of the surface waters, where Arrhenurus, Fiona, 

 Limuesia, Uniouicola and the "red mites", like Diplo- 

 dontus, usually predominate. However, Limuesia led in 

 number of individuals and was found at all depths, as 

 were also ArrJieuurus, Neumauia and Piona. Lehertia 

 and Torrenticola were very abundant in the shallow 

 places but were not found at the greater depths. Mideop- 



