1914] Biology of Net-Spinning Trichoptera 258 
To quote from the first article: ‘“‘The typical form of the 
structure resembles a tunnel attached to the surface of a stone, 
having at its mouth a vertical framework with a net stretched 
across it. An open mouth or entrance to the case is always 
close to this net on the side towards the current, so that without 
wholly leaving its house the larva can remove from the net 
anything eatable, which the current may have lodged there. 
The mode of building varies considerably. The case is usually 
about half an inch long and a little curved, loosely attached 
to the stone by its edges and without any bottom. It may be 
composed entirely of sand or of bits of plants or both combined. 
The supporting framework of the net is always formed of 
vegetable bits, and is sometimes a simple arch, sometimes a 
complete ring, and sometimes a short cylinder. It is occasion- 
ally stayed or held in position by silken cords stretching from 
it to suitable points on the stone. It is stiff enough to stand 
erect even when removed from the water. When it is in the 
shape of a cylinder or broad arch the net is always stretched 
across that end of it which is down stream and the entrance 
usually opens under the shelter of the arch. * = = if 
In a stream in Brookline, Mass., are large communities of these 
larvae. The stones in the stream are covered with mud, 
leaves and rubbish. 
Sometimes a stick which has fallen into the brook has a 
row of cases and nets built upon it. Often a stone will have 
a row of them side by side along one edge, or there may be 
only a few of these structures scattered separately upon its 
surface.’’ She mentions having received a net and larva 
from Mt. Desert, Me. 
In 1886 L. O. Howard found similar nets of a Hydropsyche 
larva on the Simulium-covered rocks in the swift water of 
Rock Creek, near Washington. ‘‘The cases varied greatly 
in size, the mouth of the funnel in some instances not more 
than 3 mm. in diameter and in others reached fully 10 mm. 
The tube of the funnel was in every case bent at nearly right 
angles with the mouth and the larva ensconced within it 
waited for its prey to be caught in the broadened mouth. 
The broad funnel-shaped expansion was woven in fine 
meshes with exceedingly strong silk and was supported at 
the sides and top by bits of twigs and small portions of stems 
of water plants. The central portion was so open as to allow 
the water to pass through readily.”’ 
