698 Wisconsin Academy of Sciences, Arts and Letters. 
each side is a narrow area of short blunt spines. The lateral 
line, consisting of white hairs not very long or abundant, is very 
inconspicuous; it begins on the 3rd segment, forming a loop 
under the 8th. No gill-filaments. Mandibles long, slender, a 
little curved, serrate, crossed in front of the labrum, which is 
very short, almost semi-circular, with three long black hairs on 
each side near the base, and five short ones near the anterior 
margin. The j)osterior end of the body is terminated by two 
slender chitinous processes about 2 mm. in length, ending in 
sharp points, and with a few short spines within, before the 
distal end. 
Case. —Length, 16-21 mm. Width, anterior, 2.5 mm.; pos¬ 
terior, 1.5 mm. Composed of very fine sand grains and much 
silk, forming a smooth and very tough case, slightly curved, 
open at both ends. At the anterior end there is a distinct hood. 
In preparation for pupation the case is shortened to about 15 
mm., the anterior end is made of even length, i. e., the hood is 
cut off, and a flaring, bell-like rim is added. Each closing 
membrane has but a single opening, an oblong one placed hori¬ 
zontally at the center. It is fastened firmly at each end by a 
cord of silk, expanding into a circular anchor where it is at¬ 
tached. 
Habits and Occurrence .—These larvae are plentiful on stones, 
sticks, and the shells of live mussels, usually slightly attached, 
in water up to 8 or 10 feet in depth. Their distribution is 
quite general, as they occur in the muddy bays, as well as in 
the sandy or stony portions of the lakes,—Mendota, Monona, 
and Devils Lake. After capturing imagos of both exquisita 
and uwaroivii, and before I suspected that they might be only 
varieties, I anticipated that their larvae might be very similar, 
and accordingly examined many specimens of what I knew to 
be the larvae of one or the other of them, to determine whether 
I could detect two species in this stage. I was unable to do so, 
and have not yet reared a specimen of exquisita in the labora- 
tory. 
The pupal stage is of short duration,—two weeks or less. 
Pupse are plentiful in June, but by the first of July have nearly 
disappeared. The adults are very common late in June, when 
