19151 
Andrews: Survey of Lake Butte Des Morts Bog 
197 
to identify specimens: Dr. F. C. Baker, Mollusca; Dr. S. Grae- 
nicher, Diptera; R. A. Muttkowski, Odonata; Dr. Denniston, 
Equisetales and Sagittaria. 
PHYSIOGRAPHIC FEATURES OF LAKE REGION 
Lake Butte des Morts is in Winnebago County in the southeastern 
part of Wisconsin. It is some five miles in length, and about 
three in breadth. There has never been an accurate hydrographic 
survey of the lake, but it is probable that its depth nowhere ex- 
ceeds twelve feet. It is evident to even a superficial observer that 
the entire lake is rapidly being transferred into a huge marsh as 
the bog now covers over three-fourths of the old area of the lake. 
The climate of this region is characterized by cold winters and 
hot summers. The daily range of temperatures is greatest dur- 
ing the summer months when the nights are nearly always cool, 
and when mid-day may bring a torrid heat, a temperature of 
more than 100 degrees Fahrenheit having been recorded. Exact 
figures for the annual precipitation are not available, but it is 
approximately 10.2 inches. The precipitation for any one of the 
summer months — June, July, or August — usually equals or ex- 
ceeds that during the entire winter. Tables I and II show the 
mean annual temperatures in degrees Fahrenheit, and the mean 
precipitation, as computed for Fond du Lac, Wisconsin, which is 
about twenty miles southeast of Butte des Morts. 
TABLE I 
Showing mean annual temperatures 
Mean temperature 68 
Mean maximum 80 
Mean minimum 56 
TABLE II 
Showing mean temperature by seasons, and mean precipitation 
SEASON 
TEMPERATURE 
PRECIPITATION 
March 1 to June 1 
4 
inches 
9 
June 1 to September 1 
70 
12.4 
September 1 to December 1 
50 
8.1 
December 1 to March 1 
20 
5 
