Charles Frederick Holder, Half hours with the lower animals: protozoans, sponges, corals, shell, insects, and custaceans, New York, American Book Company, 1905.
The so-called caddis worms (Fig. 191) are merely the larvae of the caddis fly which incloses itself in a case that is often decorated in a singular way. The cases of a number of the worms placed together display a striking variety of designs. Some roll up leaves; others spin a silken thread from the mouth and bind pieces of leaves together, attaching other pieces to it.