Often been mistaken by shell-collectors

Alpheus Spring Packard, Entomology for Beginners, New York, Henry Holt & Co., 188, 1890, p. 188.

All the Caddis-flies are sack-bearers un their larval state, and the larvae are from this habit called case-worms. The worm apprently builds them by adding grain after grain of coarse sand to the mouth of the tube, lining the interior with silk ; if there is moss at hand, bits are fastened to the exterior, or large pieces of leaves. Fig. 233, a, represents the case of European Phryganea grandis ; but we have a similar one, formed by cutting a leaf into a broad ribbon-like strip and then rolling it into a tube some are like horns, while the case of Helicopsyche (Fig. 233, d) has often been mistaken by shell-collectors for a freshwater snail (Valvata).