An expert can determine the species of the occupant.

Francis Blackwell, Tiddlers & Tadpoles, Ill. A. Fraser-Brunner, Medallion Collectors n°2, Londres, Medallion, 1951, p. 31.


The larvae are truly aquatic and are found in stagnant and running water everywhere ; nearly all of them make for themselves a protective cylindrical case to house the long soft body, and as the larva’s head and legs are free it drags this case around with it wherever it goes. Sometimes the larva appropriates a hollow reed or stem but more often it prefers to construct a case from all sorts of tiny odds and ends, bits of stick, leaves, grains of sand- anything in fact may appeal to the diminutive builder, and the choice tit-bits are cemented together with strong silken strands which the larva « spins » from its head-glands after the fashion of the silk-worm ; the interior of the case, too, is cosily lined with silk. As the larva grows, it either cleverly enlarges its case or, les frequently, abandons it altogether and builds or seeks out another. Each species of caddis-fly has its own favourite building material, so that from the shape and character of the case an expert can determine the species of the occupant.