Robert W. Hegner, College Zoology, New York, The MacMillan Company, 1914, p. 350.
The term caddice-fly is derived from the case (Fig. 282, A) which its aquatic larva builds of leaves, grass, stems, or grains of sand as a mean protection. The larva (B) can extend the force part of the body and drag its case from place to place or can retreat into its house for safety. Thread-like tracheal gills are present on the abdomen. Each species builds a certain kind of cases which can be distinguished from those built by other species.