258 Annals Entomological Society of America [Vol. VII, 
Although there are six species of Hydropsyche larve com- 
mon in Cascadilla Creek, I have not been able to find any 
specific differences in their nets, so will describe them col- 
lectively. The case in which the larva lives, I found as de- 
scribed by others, except Miss Clarke, to be made of vegetable 
bits, pebbles, or a combination of both woven into an irregular 
cylindrical tube. In front of this, opening toward the current is a 
net. Mrs. Comstock’s word ‘‘dip-net’’ best describes its shape. 
Beginning at the entrance and generally extending for a little 
more than one half the depth of the net is a very irregular, 
coarse silken mesh, the bottom of the net being composed of a 
wonderfully beautiful, regular mesh. This latter is the catch- 
ing surface proper from which the larva feeds. The tube in 
which it lives extends a very short distance into the net, so that 
its entrance opens under the fine mesh. The tube opens into 
the net either from the right or left side, and is found either 
extending back in a straight line with the net or almost at right 
angles to it. When the stones are taken from the water, some 
of the nets stand upright owing to the supports of plant tissue 
woven into the coarse mesh. Sometimes there is a complete 
supporting arch, but often there is only an oblique prop on 
either side, anchored to the stone by silken guy lines. The 
threads of the catching surface are somewhat distensible, and 
when seen in the water it is concave, but when removed, it 
appears as a flat, almost circular disc in its supporting frame- 
work. In many cases, however, the nets collapse completely 
when there is no current to distend them, there being no sup- 
porting bits of any description. See Plate XXXVII, fig. 2. 
In summer many of the nets have long green streamers of 
Cladophora filaments, which have become entangled in the 
nets and float back several inches behind them. 
The average expanse of the nets at the entrance is about 
8 mm. although some of the largest ones have an expanse of 
20 mm., with a depth of 15 mm., while those of the very young 
larve have an expanse of 144 to 2 mm. and a depth of 1 mm. 
These nets and dwellings I have always found completely 
submerged, and the true catching surface placed at the end of 
the vestibule, instead of in its sidewall as in that of H. angusti- 
pennis described by Wesenberg-Lund (1911). The threads 
are very firm so that they may withstand the force of the 
current and there is no difficulty in seeing the meshwork with 
the naked eye. 
