Samuel Jackson Holmes, The elements of animal biology, Philadelphie, P. Blakiston’s Son & Co, 1919, p. 73.

The caddis flies are much better know in their larval than I their adult state. The larvae are remarkable for surrounding themselves in a tubular case made of various materials which tey carry about with them. Some species construct cases of sand, some employ irregular sticks of wood, while a few make their cases of bits of leaves which are cut out in a regular rectangular shape and fastened together at the edges in a most neat and orderly manner. Usually only the anterior part of the body is protruted from the case. The posterior part is soft and generally furnished with outgrowths which serve as grills, and at the tip of the abdoman there is a pair of hooks by means of which the worm holds on to its case. When the worms are removed from their cases they will readily construct new ones if given the proper materials.