Jim Arnosky, Flies in the water, fish in the air : a Personal Introduction to Fly Fishing, New York, Lothrop, Lee & Shepard, 1986, p. 18-19.

I discovered small cylindrical tubes littering the stream’s pebbly bottom. Upon examining one, I found it to be a hollow case made of tiny pebbles with something alive inside. That something was a caddisfly larva, and the tub, called a «  caddis case », was its home…./… Because the case-building types are more obvious in the water, I am more familiar with them. The kid of case a caddis worm make depends upon the species of caddis it happens to be. Some build cylindrical cases out of tiny pebbles. Other construct simpler odd-shaped pebble case. There are caddis worms that build rustic-looking cases out of sticks and leaf matter. All materials used in caddis cases are held together with silk produced by the worms themselves.

My favorite type of caddis case is one made out of tiny cut strands of leaf. The worms that make them carefully wrap the strands in a way that creates a tapered rectangular tube. The workmanship in these particular caddis cases is remarkable.