Margaret Shaw & James Fisher, Animals as friends and how to keep them, Londres, Dent, 1939,
Caddis worms are usually found in slow-moving water. They are the larvae od caddis flies, and each species spins a different kind of case made of grass, sand twigs, fine gravel, small empty snail-shells, or water weeds. The insect crawls about withits head and front legs protruding from the case until it is time to pupate. It feeds mainly on plants. The snare-building caddis worm does not make a portable case, but spins a loose web of silk..