Muttkowski—The Fauna of Lake Mendota. 
403 
is of sand and shell fragments. The species seems confined to 
the sublittoral area. 
Leptocerus dilutus Hagen. 
The minute, curved, and hooded cases are characteristic for 
the rock and gravel shores, though less common on the latter. 
This is not an abundant species. 
Leptocella uwarowii Kolenati. 
This is the characteristic caddis-fly of the lake, especially in 
the plant zone, and occurs everywhere in amazing numbers. It 
. is adapted to a variety of aquatic conditions, for it seems also 
to be able to maintain itself to a fair extent on the rocky shores 
and in the rapids of the Yahara Spillway. 
Only the larger fish eat the caddis-worms, for the long cylin¬ 
drical tubes are somewhat difficult to manage. In fall, at the 
time of the heavy equinoctial storms, myriads are swept onto 
the shores and killed in the surf. After such a storm a thick 
lake drift lines the shore, while a secondary drift may be found 
in places in the water; a large portion of the accumulation will 
be composed of the dead Leptocellae. 
Setodes grandis Banks. 
Though occurring sporadically in the lake, the true habitat of 
this species is the Yahara Kiver north of the lake. There the 
larvae in their translucent green cases may be found abundantly 
on Myriophyllum, etc. 
Triaenodes flavescens Banks. 
The spiral case is characteristic for this species. It is fairly 
abundant in somewhat sheltered spots, such as the small bayou 
north of the Yahara Spillway. 
Family Sericostomatidae. 
Helicopsyche borealis Hagen. 
This is a small species, which is quite common on sandy bot¬ 
toms. The characteristic case is built like that of a snail, as 
which it has been repeatedly described. First instar larvae 
build a slightly twisted case, while that of the second instar 
larva is like the case of the older stages. The species is eaten 
frequently by fish. 
