AQUATIC INSECTS IN NEW YORK STATE valid 
larger prey, however. Very frequently in my aquariums, after 
the supply of other food has run out, I have found a larva, with 
another larva of its own species and nearly of its own size, two 
thirds swallowed and one third digested. 
We have but few species of Corethra, and they are much alike, 
and should be readily recognized generically in larval and pupal 
Stages by comparison with the figures given on plate 39. 
3 Unknown trichopter larva from bottom of Bone pond 
This is another species that lives outside the line of the shore 
vegetation. Just outside that line, on bottoms shallow enough 
to be reached with a long handled sieve net, Mr Betten found’ 
the cases of the species in great abundance, but they were all 
empty. He has described the case in bulletin 47, page 572, as: 
no. 2. 
Because all students of our lake bottoms have reported caddis: 
fly larvae along with Chironomus larvae as a constant part of 
the fauna, I have thought it desirable to have the structural 
characters of this species illustrated as fully as possible in the 
hope of its recognition by comparison in the future. The only 
specimens seen were obtained from the trout stomachs, and 
were pretty well digested. Some of the cases were fairly well 
preserved, but the pupae were so badly disintegrated as to be 
hardly distinguishable as pupae; the parts of the larvae most 
strongly chitinized, and the parts most important for the dis- 
tinguishing of the species were fairly well preserved, and have 
been used, together with a perfect case collected from the water 
and apparently belonging to the same species, as a basis for the 
figures presented on plate 6. 
The trout swallow the animals case and all, doubtless being 
unable to get them apart. The case persists after the animal 
within has been disintegrated, but the sand grains gradually 
fall off, and the brown, lining tube of silk gradually breaks up 
into fragments. Most of the stomachs contained a little sand, 
doubtless derived from this source, and trout nos. 2, 3, 6,7 and 17 
contained large quantities loose, in addition to that still on the 
walls of the cases remaining. 
