NORTH AMERICAN CADDIS-FLY LARV. 
FAMILY HYDROPSYCHID. 
The family is divided into two subfamilies. The Macronema- 
tine are abundant in the Great Lake region, but have not been 
found in the vicinity of Ithaca. Their larve probably live in 
large lakes and slow-moving rivers. As yet there is no published 
account of their immature stages. 
The subfamily Hydropsychine is represented in our fauna by 
a few species belonging to three genera. These have been care- 
fully studied by Miss Alice Noyes and have been recorded by her 
in 1917, and in the manuscript of a forthcoming paper. The 
present account of the larvae is condensed from the work of Miss 
Noyes. 
Hasits.—The habits of our three genera of Hydropsychine 
differ one from another only in minor details. The best-known 
species are recorded in the genus Hydropsyche, but probably most 
authors have not made generic determinations within the family. 
Hydropsychid larve dwell only in swift-flowing waters and on the 
wave-beaten shores of lakes. In these situations they occur in 
vast numbers. Miss Noyes seems to have found it not uncommon 
to find as many as 165 larve on a square of the stream’s bottom 
measuring only 8% x 8% inches. The larve are most abundant 
on the exposed surfaces of stones, ledges, and even on the brinks 
of falls. In these situations they build the characteristic nets that 
are so well known in the literature on entomology. The nets, 
typically, have a semicircular opening facing upstream. From 
this opening the net extends back in bag-like form. The front 
end is made of fine silk, strengthened by irregular coarse strands. 
Behind the fine-meshed front margin there is an area of coarser 
mesh that acts as a seine. It is made of tough strands running 
in two directions, forming a mesh of minute squares, through 
which the water passes while straining out its burden of plancton 
and small insects. The larva lives in a silken tube at one end of 
the seine. From this retreat it can freely enter the trap to feed 
upon its catch of aquatic organisms. 
Foop or THE Larv.—Young larve feed upon green and blue- 
green alge. In later life they change their diet to include also 
diatoms and various vegetable plancton, as well as Ostracods and 
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