256 Annals Entomological Society of America __[Vol. VII, 
swift and in spite of their delicate construction, they stand 
the considerable pressure of the water very well. I have 
never noticed that the dwellings or nets protruded above 
water.”’ 
One of the most interesting of the descriptions of Hydro- 
psyche catching-nets comes from Dr. Wesenberg-Lund. In 
his paper (1911) he has compiled the records of all known 
cases of net-spinning and extended our knowledge greatly by 
personal observations. He studied the nets of H. pellucidula 
and H. angustipennis, and gives a very full description of the 
beautiful structures of the latter which he studied in July, 
1909, in the outlet of Foenstrup pond in Gripwalde. The 
larvae had utilized the leaves of Lemna triscula in the con- 
struction of their dwellings, and chains of these, arranged in 
rows, were placed obliquely across the stream. Every chain 
was composed of the dwellings of a number of larvae. Each 
house had a funnel-like entrance facing up stream which led 
into a vestibule about 1-2 cm. long and of the same height, 
covered with Lemna leaves. In the farther corner was the © 
entrance to the larval dwelling which was 2-3 cm. long. This 
is always laid obliquely to the principal course of the chain, 
and was made of small bits of decayed wood and pebbles 
interwoven in the silken mesh and covered with Lemna leaves. 
In the wall of the vestibule towards the entrance to the dwelling 
was a circular window about 1 cm. in diameter covered by a 
beautiful screen. This served as the larva’s catching-net 
and was woven of strong threads crossing nearly at right 
angles and of wonderful regularity in the centre, but irregular 
and of a coarser mesh toward the framework, which was made 
of small pieces of straw finely fastened together. The cases 
were submerged in the water, but the upper part of the vesti- 
bule and window projected over the surface of the water. I 
have copied a diagramatic figure of a Hydropsyche house 
from his paper. (See Plate XXXVII, Fig. 1). 
In regard to the seasons when the nets are found he gives 
the following data: ‘‘Up to December, beautiful larval dwell- 
ings and nets are found; from December to the last of April 
no nets observed. During this period the larvae were found 
rolled up under stones or in crevices in boards, probably taking 
only a little food. At the beginning of May and during the 
whole of June the nets were put up again.”’ 
