William A. Niering, The Life of the Marsh, The North American Wetlands, New York, MacGraw-Hill Book Company, 1966, p. 118-119.

If you look attentively, you can find an odd little parcel of tiny leaf fragments and sticks moving deliberately along the bottom of the water in the wooded swamp; you can see legs protruding from the tube. This is a caddis-fly larva, hiding Inside the camouflage it makes out of dead leaves ans twigs. It feeds on small water plants and animals during its aquatic stage. Wherever it goes, it drags its case along.