Samuel Eddy & James Campbell Underhill, Northern fishes with special reference to the Upper Mississipi Valley, University of Minnesota Press, 1974.

The larvae of various Trichoptera species build many different kinds of case. Some possess glands that produce a silk material with which each larva constructs a case around itself, leaving only the head end protuding. Sticks, tiny shells, sand grains, small pebbles, and bits of vegetation are used by other species to make cases (Figure 9). Some species prefer to live in swift water where they attach their case of sand and pebbles to rocks.One species builds a case equipped with webs or nets fashioned to resemble wings which the larva uses to catch prey. Other species make cases that look like bundles of tiny sticks ; it is quite startling to see a bunch of sticks slowy moving over a smooth mud bottom. Another species uses tiny sand grains to build a coiled case that look like a snail’s shell. Still another species makes an elongated case of tiny sticks crossed in a symmetrical log-cabin pattern.