Harold Melvin Stanford, The Standard reference work: for the home, school and Library, Vol. 2, Chicago, Standard Education Society, 1921.

Caddice Fly, an insect resembling a moth. The caddice fly lays its eggs in water. The larva has ability of spinning…
It glues together a case of pebbles, bits of wood, straw, grains of sands, fragment of shell, or anything of the sort inside of which it constructs a silk-lined nest in which to live. Some species leave this home in search of food.
Others drag it about as the snail does its shell. One might see hundreds of these cases on the bottom of a brook without suspecting their nature. Some caddice worms, as the larvae are called, decorate their houses by gluing on shells, even of living snails. An astonishing proof of their ingenuity is the construction of tunnel-shaped webs, fastened to stones in running water, apparently for the purpose of catching insects. When full grown the caddice  worm retires into its silky nest, closes the door for a while, and emerges in due time a caddice fly.