or 
1914} Biology of Net-Spinning Trichoptera 25 
Comstock, Anna B., (1903), in describing the snare of 
Hydropsyche writes, “‘It is formed like a dip-net and fastened 
with silk to a frame of leaves or pebbles, so that its distended 
mouth is directed up stream. Near the frame it consists of 
fragments of vegetation woven into a silken tapestry and 
is finished at the end with a bag of coarse, even mesh. The 
regularity of this bit of netting is beautiful to behold, and 
its use shows the cleverness of the builder. This large mesh 
allows the water to flow through freely, and thereby leave 
entangled in the seine any little creature not small enough to 
pass through. * * On the side of this tiny seine 
toward the current of the stream is a little passage which leads 
to the seine-builder’s house.”’ 
The work on the net-spinning Trichoptera was next taken 
up in Europe and it is to the Danish investigators that we 
owe our most extended knowledge of the various kinds of nets, 
and whose work stimulates a desire to carry their efforts 
farther. E. Petersen, in 1908, found the catching nets of 
Hydropsyche instabilis in a brook north of Silkeborg (Den- 
mark). The larger stones were completely covered with 
Potamogeton pectinatus, Fontinalis antipyretica and Junger- 
mannia sp., and on them the trumpet-shaped catching nets 
were placed in rows and connected with one another. The 
nets were small, being only 8-10 mm. in diameter at the mouth, 
and their depth about 7 mm. The nets were always supported 
by the plants and parts of these were often wovenin. In many 
cases one net was placed a little behind the others and con- 
nected with them by a strong web. At the base of the net 
lurked the larva. 
In 1909 Ussing described a catching-net of H. instabilis 
that he had found in Hornbek brook in the vicinity of Randers. 
Being unable to obtain this paper, I have translated an extract 
from it, which was quoted in Wesenburg-Lund’s (1911) article. 
“The nets are placed obliquely in front of the opening of the 
larva’s tunnel, built of very fine, square meshes (0.2 mm. 
in diameter), propped up by bits of plants. The dwelling of 
the larva is built out of mud and half decayed fragments of 
plants; the tube is spun fast to a stone on the bottom of the 
brook. I have often found whole rows of these dwellings 
with nets placed between the separate occupants. The nets 
turn their expanse against the stream, which is always very 
