Is so distinctive

Stefan Buczacki, Fauna Britannica, Londres, Hamlyn, 2002, p. 89.

The caddis-fly larva is so distinctive because many species build small protective case for themselves from tiny pieces of twig and other wood matter, tiny fragments of gravel, or even the discarded shells of minute molluscs. The materials used, and the overall appearance of the case, is characteristic of individual species. As the larva grows, it adds pieces to the case, which thus «  grows » as well.