F. L. Kirk, « Entomology as a Hobby, Presidential Address »,Lincoln, Lincolnshire Naturalists Union Transactions, vol. XI, n°4, december 1947,  p. 151.

The aquatic larvae or Caddis Worm have the well-know habit of forming cases to protect their soft bodies. These cases have a silk foundation covered with  sand, bits of wood, lengths of plant stalks or shells of snails. The shells may still contain the snails. Caddis worms in running water weight the cases with stone but in ponds lighter materials are employed.