INTRODUCTION. 
caddis-worms inhabit fresh water, except a single species from 
New Zealand that lives in the ocean, and a well-known terrestrial 
species of Europe that lives in the moss on tree trunks. 
In economic importance the Trichoptera rank very high as food 
for fresh-water fishes. During the summer months the surface- 
feeding species of fish, such as the trout, obtain a never-failing 
supply of food from the caddis-flies, as they hover over the sur- 
face of the stream and lakes. The larvee, however, form a much 
more important article of food for fishes than do the adults. Trout 
taken from the streams of Ithaca in the early spring are found to 
have their stomachs gorged with caddis-worms of the genus Neo- 
phylax, and to contain no other food. In New Zealand, Hudson 
examined the stomachs of sixty trout caught at all seasons of the 
year, and found a total of 5,466 insects. Of these 4,241 were 
caddis-worms. 
Probably no other order of insects is of as great importance in 
the food of wild trout as Trichoptera, and the day will probably 
come when caddis-worms are raised by fish culturists as food for 
their fishes. 
In eating caddis-worms, fishes swallow cases and all, their 
stomach becoming filled with sticks and pebbles, as well as with 
the bodies of insects. 
Aguatic ENvIRONMENT.—To avoid constant repetition on 
following pages, a brief description is here given of situations in 
which the greater part of the present work on caddis-worms was 
done. 
Cayuga Lake, a body of water about forty miles long, with an 
average breadth scarcely exceeding two miles, lies in the valley 
below the Cornell Campus. It is a deep lake with precipitous sides 
that rapidly descend to a depth too great for submerged vegetation, 
except at the two ends, where there are shoals with luxuriant 
growths of aquatic plants that merge into large cat-tail marshes. 
The insect fauna of the lake has never been studied. 
All of the streams of the region flow into Cayuga Lake. On 
approaching it they descend rapidly in a series of falls and tor- 
rents. In this region of rapid descent their bottoms are of rock 
and they pass through deep gorges. 
Higher up they have more the character of the usual streams 
throughout the country. They flow in a series of pools with bot- 
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