R.B. Lodge, The Story of Hedgerow and Pond, Illustrations de l’auteur, Londres, Charles H. Kelly, 1906.
Crawling on the bottom, and on the stalks and leaves of the water-plants, are moving tubes covered with small stones, bits of stick, and small shells. Inside each of these curious tubes is a whitish grub, a caddis-worm, which when at rest withdraws itself altogether inside the tube, but can stick out its head and legs and walk about when it requires exercise or food. It turns into a chrysalis inside this cleverly constructed shelter, and finally becomes a two-winged fly. The small shells with which its dwelling is adorned are very often alive, or rather contain the living snails which live in them, and these are thus carried about by the caddis-worm, and used by it as building materials, without their consent ever having been asked.