252 Annals Entomological Society of America _[Vol. VII, 
This paper is a preliminary study of the net-spinning 
Trichoptera of Cascadilla Creek with special reference to the 
nets—the method of construction, their efficiency as a plancton- 
catching apparatus, and the closely related problems of food 
and feeding habits. 
Since the net-spinning caddis-worms are found in still as 
well as swift flowing water, and their nets are such interesting 
and beautiful structures, it seems strange that they should have 
been overlooked for so long a time. I have found nets repre- 
senting some of the genera of the families Hydropsychide, 
Philopotamide, and Polycentropide, and will treat them by 
families in that order. In each family I have first given 
extracts or a brief summary of the work published on the 
nets up to this time and have then added my own observations. 
This work was carried on under the supervision of Prof. 
James G. Needham, to whom I am especially grateful for 
his valuable suggestions and encouragement at all times. 
II. CATCHING-NETS OF THE FAMILIES HYDROPSYCHIDAE, 
PHILOPOTAMIDAE, POLYCENTROPIDAE. 
FAMILY HYDROPSYCHID. 
The first description of a catching-net is found in Dr. 
F. Muller’s work (1881). He describes and figures the net of 
one of the Hydropsychidz, a southern Brazilian sp. of the 
Genus Rhyacophylax. He always found the houses on the 
upper side of stones, made of irregularly interwoven plant fibres 
or of small stones. Each house has a funnel-shaped vestibule 
or verandah, whose sidewalls are generally constructed out of 
interwoven fibres. These serve as a covering for a very delicate 
silken net with square meshes, generally from 0.2 to 0.38 mm. in 
diameter. The entrance to the vestibule is always directed 
up stream, so that the water coursing through it catches and 
holds back organisms which serve as food for the caddis-worm. 
The larvae rarely live alone, but generally construct their 
houses very close to one another so that sometimes continuous 
rows of them are formed. 
In the year following, the first work on the nets: of the 
Genus Hydropsyche appeared in this country in an article by 
Miss Cora Clarke. In a later paper, 1891, she mentions these 
larvae and their nets again, but gives no additional data. 
