Johann Loeser, Animal Behaviour, Ill. Erna Pinner, Londres, MacMillan & Co., 1950, p. 25.

Such armour may even be self-created, whether from the materials of an animal’s own body, as is the case with some tube-making worms (chiefly Polychaetes), which surround themselves with tubes consisting of organic substances, or from alien materials when the exceedingly sensitive bodies like the larvae of the caddis-fly are protected by the soldering together of all kinds of alien materials by means of a mucous secretion.