Muttkowshi—The Fauna of Lake Mendota. 
407 
to the larva the pupa has an elaborate tracheation which com¬ 
municates with a pair of external air-chambers from the thorax. 
Pupal life is very short, and lasts one to three days, at most. 
The daily migration of the larvae needs mention. In day¬ 
light the larvae are found below the thermocline and in the bot¬ 
tom mud, while at night they come to the surface. Aside from 
the considerable adjustment entailed by the change in pressure 
(at least two atmospheres), there is the change from aerobic to 
anaerobic conditions which perplexes us and leaves us in doubt 
as to the precise status of the air chambers. 
The larval history lasts about six to seven weeks. Hence 
there may be three generations during the summer, the wintered 
larvae pupating in May and June, the second generation ap¬ 
pearing in late July and early August, the third generation in 
September. Wintering larvae are uniformly larger before 
pupation than are summer larvae. 
Family Chironomidae. (Table 5, p. 475). 
The species of Chironomidae about Madison are legion. The 
various waters,—lakes, ponds, springs, creeks, swamps, 
whichever they be—all contribute their share to the Chirono- 
mid complex. Only a small portion of this complex has been 
studied, and a still smaller portion only can be referred to 
in this paper. In practically all of the species listed it was pos¬ 
sible to breed the species and verify previous work. Addi¬ 
tional species from other waters were also bred, some in all of 
their stages, some in part only,—wherever opportunity offered 
and time would permit. An idea of the richness of the Chiron- 
omid fauna may be gained from the fact that I have taken at 
least 35 species from the lake, and that each of the surround¬ 
ing waters contains several other species. The contents of fish 
stomachs from various localities have apprised me of further 
unknown stages. 
Cerotopogoninae. 
Palpomyia longipennis Loew; Probezzia pallida Malloch; Pro- 
bezzia glaber Coquillet. 
Specimens of these three species were bred in large quanti¬ 
ties. All three are common in the lake and appear to show a 
special preference for Cladophora and other filamentous algae 
as a habitat. 
