The same materials

P. Martin Duncan (édité par ), Cassell’s Natural History, Londres, Cassell & Company, 1883, p.18.

To protect this soft body the larva makes himself a little habitation, which is composed of the most various materials by different species. Fragments of wood and leaves, short lengths of reeds, and other hollow stems, small stones and grains of sand, little shells, often with their owners still living in them, and sometimes even the cases of other smaller Caddises are made use of; but each species usually employs the same materials or, at any rate, the same class of materials in the construction of its dwellings. These materials, whatever they may be, are held together by means of silky threads produced by glands which have their opening in the labium of the larva. The cases are often at first tapering; but in most instances the larva prefers a cylindrical dwelling, and after a time removes the slender posterior end and uses the materials, along with others, to add to the length of the case at the wider end.