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Trichoptera (caddis flies, sedge flies, silver-horns, Welsh buttons; class Insecta, subclass Pterygota) An order of aquatic, rather moth-like insects that spend most of their lives as larvae inhabiting cases they construct from small mineral grains or plant material, the type of case often being characteristic of a species. Larvae lack abdominal legs, are free-living or spin webs to trap food particles, and pupate below the water surface in shelters attached to stones or other objects. The pupae swim to the surface, where the adult emerges. Most adults do not feed, those that do feeding on nectar. The name, Trichoptera, is derived from the Greek trikhos, ‘hair’, and pteron, ‘wing’, referring to small hairs that cover the wings. Fossil Trichoptera are known from the Triassic. There are about 7000 species, in about 25 families. They occur in unpolluted water on all continents.