1914] Biology of Net-Spinning Trichoptera 269 
1. Time of building—Many Trichoptera larve build their 
dwellings chiefly during the night, but these build their tubes 
and nets at all times, during the day as well as at night. 
2. Time required for building—On watching the con- 
struction of several larval dwellings, I found the average time 
for the completion of the tube and net to be from two and a 
half to three hours. The larva spent about an hour in spinning 
‘its tube and the remainder of the time on its net. 
3. Different species of Hydropsyche larve placed in the 
trough built similar dwellings. 
4. There were no temporary construction threads in the 
net as described for the web of orb-weaving spiders, (Comstock, 
J. H., 1895, p. 37), all of the threads being permanent. 

1 2 a 
Text Figs. land2. 1. Diagram showing usual method of crossing of threads 
to form the regular mesh of the net. 2. Attachment of threads. (a) at beginning 
of thread; (b) continuation of same thread at point of departure from supporting 
surface. 
5. There seemed to be no definite order in which the 
threads of the net were laid down. Sometimes the coarse, irregu- 
lar mesh was spun immediately after the building of the larval 
tube, while at other times the fine, regular mesh was spun first. 
The larva at times left its work on the net and went back to 
add a few threads to the case. In general the catching surface 
was formed of threads crossing each other in the fashion 
shown in figurel. Threads were fastened in the manner shown 
in figure 2, the double thread being split for a short distance and 
each half attached separately. 
6. I have never observed the larve cleaning their nets 
with the dorsal tuft of hairs on the anal prolegs, a function 
which Lund (1911) stated as a probable one. They have 
always removed particles from the net with their mouth-parts. 
