1914} Biology of Net-Spinning Trichoptera 2a 
His observations agree completely with those sent him by 
Ussing, who made regular observations on the nets of H. 
instabilis during the winter of 1909-10 at ‘“‘Hornbek brook.” 
“On the 24th of October, 1909, the nets were very numerous; on 
November 7, beautiful catching nets; on January 2, and Jan- 
uary 19, 1910, none. The animals build no catching-nets in 
winter. The larvae lie rolled up in a spiral and are not active, 
moving reluctantly. They do not live in the usual case, but 
in an irregular net with small pebbles interwoven. He believes 
that the Hydropsyche larvae lie in a dormant condition and 
take no food in winter. 
My observations were started the latter part of October, 
1912, and at this time, although the nets were numerous every- 
where in the creek, they were inconspicuous, owing to a thick 
coating of diatom ooze and silt, and they were badly torn 
by the large numbers of fallen leaves swept along by the cur- 
rent. Only rarely during November did I find a perfect net, 
and during the winter months no nets at all. Heavy rains 
the last week in March made any observations impossible, as 
the turbid water rushed along in torrents. On my next visit, 
however, on April 12, it was as if the stones had been touched 
by some magic wand, for nets had sprung up everywhere. 
They were found on the upper surface of stones or shelving 
rocks wherever there were irregularities or crevices against 
which the cases might be built; on submerged twigs, on the 
underside of stones, and between stones on the bottom. The 
nets were also thick along the edges of the stream, many dis- 
tended pockets being found in the tangle of roots which floated 
out int@sthe current. In July similar nets were observed in the 
mats of Cladophora, but these were generally the tiny pockets 
of very young larvae. I could find no definite dwelling tube 
in either of these instances, but the larvae were found crawling 
among the roots or algal filaments. 
On the brinks of the waterfalls were rows of vertically 
placed nets, so that a continuous stream of water was pouring 
down their open mouths. On the creek bottom the nets were 
generally fastened between two stones, some being of the 
‘“‘dip-net’’ type, while others formed a horizontal net. In 
both instances, however, the net was composed of coarse, ir- 
regular mesh at its entrance and a fine regular mesh behind. 
