Baker—The Fauna of The Lake Winnebago Region. 119 
a habitat often have the foot unusually developed for this pur¬ 
pose. Three species make up 73 per cent of the total population 
of the boulder habitat: Pleurocera acuta 19 per cent ; Physa sayii 
43 per cent; and Lymnaea winnebagoensis 11 per cent. Physa is 
here the dominant species. 
Associated animals are about six times as numerous in individ¬ 
uals as the Mollusca (Mollusca 17 per cent, associated animals 83 
per cent). Fifteen higher groups of aquatic animals are repre¬ 
sented. The conspicuous forms on the rocks are the caddie-flies 
(Trichoptera) the elongated or flattened tubes of which are fas¬ 
tened to the rocks by filmy anchors. The snail-like case of Heli- 
copsyche and the flattened tubes of Leptocella are the most con¬ 
spicuous. Hydroptilidae and Agraylea are also represented. Poly- 
centropid larvae, with their funnel-shaped tubes attached to the 
rocks by broad bands of a fine cementing substance, are common. 
Chironomid larvae and pupae are abundant, their tubes being at¬ 
tached to the under side of the rocks. The Bphemerids, repre¬ 
sented by the nymphs of Heptagenia, are occasionally seen on the 
under side of rocks, but these are not as numerous as was observed 
in Oneida Lake. Caenis occurred at one station. An Enallagma 
nymph was caught at another station. Coleoptera, represented 
principally by the flat larva of Psephenus lecontei, also included 
Stenelmus bicarinatus, Oyrinus ventralis, and an unknown larva 
of Dascyllidae. 
In some places the smaller cobbles mixed with the larger rocks 
are covered with life, especially associated animals. Thus at sta¬ 
tion 12, 1,225 individuals, representing twelve higher groups, were 
picked from 24 rocks with a maximum surface area of 1,350 square 
centimeters. 
Cladophora harbors certain species which cannot be strictly 
called petrophilus. Small Nematodes, Planaria, Cladocera, Ostra- 
coda, the mites Limnesiopsis, Hygrobates, and Lebertia; two 
Hemiptera, Belostoma and a Corixid, occurred at two stations, in¬ 
cluding both adults and nymphs. The Amphipod, Hyalella knick- 
erbockeri, was abundant where the alga was most plentiful. A few 
Chironomid larvae as well as Trichopterid larvae also live among 
the algae. 
Burrowers, including small leeches and Cambarus propinquus, 
were observed beneath the boulders, but they were not abundant 
in the purely boulder habitats. The disparity in numbers between 
the Mollusca and the associated animals in the boulder habitats is 
