The caddisflies are a cosmopolitan group of insects whose aquatic larvae are perhaps better known than their moth-like adults. There are currently 199 species known from the British Isles, out of a total of around 1400 species in Europe and over 12,000 worldwide. Although close study of the genitalia is often necessary for species identification, much progress can be made with easily observed characters such as wing patterns. This handbook contains some formal keys as well as numerous illustrations of both living and preserved specimens to aid the newcomer to this group.