268 Annals Entomological Society of America [Vol. VII, 
Except for one Chironomid head there were no recognizable 
contents in the alimentary tract of the Cyrnus sp.—only a 
dark brown fluid exuded. After watching it feed, however, on 
the soft bodied forms of microscopic organisms, one can 
account for this fact. 
V. EXPERIMENTAL WORK ON HYDROPSYCHE NETS. 
To one who tries to study the method of construction of the 
nets, feeding habits, etc., in the field, the following difficulties 
present themselves. The threads of the net quickly become cov- 
ered with diatoms, silt and algae which obscure the mesh to some 
extent; the ripples on the surface of the water make it necessary 
to work with a water-glass which cuts out some of the light; 
also the nets are so low down that one can only view them 
satisfactorily from above. 
Although the Hydropsyche larva will construct its dwelling 
tube in a dish of water in the laboratory, it builds no 
catching-net. The larvae, however, made perfect nets in a 
trough supplied with a steady stream of partially filtered water 
from Cascadilla Creek. The trough stood on a framework 
three feet high and was tilted slightly, the end nearest the water- 
pipe being the higher. The side boards of the trough were 
grooved (14 in. by 4 in.) their entire length, and the stream of 
water striking the end board was carried down into the 
grooves as well as into the trough. On each side, at the 
point where the water from the groove met the overflow 
from the trough (See Plate XXXVI, Photo 3.) the current was 
the swiftest. As might be expected these spots were chosen in 
preference to others as building sites. The only caution 
taken was to induce the larva to begin its spinning very near 
the end of the groove so that the net would come within the 
focus of a lens held in front of the groove. The making of 
the larval dwelling could best be observed from above, but 
observations on the construction of the net and the feeding 
habits could be seen to best advantage when one knelt in front 
of the groove so that the eye came on a level with it. In all 
cases a glass slide was placed over the groove to smooth the 
surface of the water. 
By the above methods, the following results have been 
obtained. 
