Gilbert Haven Trafton, Nature Study and Science, New York, The MacMillan, (1927), 1929.
The interesting feature of the caddis or case worm is the beautiful little case which it builds and lives in while in the water. (Fig. 62) These case are about an inch long and as big around as a lead pencil. Some of them are made of little bits of sand cemented together and lined with a soft silk thread which the worm spins.