Muttkowski—The Fauna of Lake Mendota. 
377 
choptera, Odonata, Ephemeridae, Coleoptera, Corethra, etc.) 
were examined; the food habits of the living insects were fur¬ 
ther observed in aquaria and in the field. This examination 
was extended also to leeches, Crustacea, Oligochaeta and other 
aquatic animals. 
It is impossible to treat all of these phases together in a 
homogeneous manner. Even in restricted form, it is difficult 
to deal otherwise than in the most general terms with the sev¬ 
eral phases. For inclusion in the present paper the following 
topics have been selected: 
I. Criteria of Lake Life,—that is, the lake as a physiological 
body, its ecological divisions, factors controlling the lake and 
its biota. 
II. Qualitative and Quantitative Survey of the Macrofauna, 
its distribution, factors which decide the complex, biological 
notes and food relations. 
III. Ecology of the Lake,—that is, the ecological habitats 
and their biota, food relations, and seasonal succession. 
IV. General Comparisons,—with other hydrobiota and with 
other lakes. 
PART I. CRITERIA OF LAKE LIFE 
1. Lake Physiography 
A. PHYSIOGRAPHY 
Lake Mendota is the largest of a chain of four lakes in the 
Yahara Basin in the middle portion of southern Wisconsin. It 
is of glacial origin, lying near the southern edge of the drift. 
The lake is an irregular body of water (fig. 1), its greatest 
length being 9.5 km. (about 5.9 mi.), and its greatest width 
7.4 km. (4.6 mi.). The circumference of the lake is 32.4 km. 
(21.9 mi.), its total surface area 39.4 sq. km. (15.2 sq. mi). Its 
greatest depth is 25.6 m. (84 ft.). The areas of the various 
depths are shown in table 1, page 471. 
Shores .—A considerable portion of the shore line of Lake, 
Mendota consists of cliffs of limestone with bold and rocky 
subaqueous terraces in front of them. Another large portion 
of the beach line consists of sand with an admixture of 
