Paul SterryPond Watching, Nature Watch,  Feltham, Middlesex,  Hamlyn Paperbacks, 1982,      p. 81.

Hatch into endearing larvae, renowned for manufacturing protective case which they carry all their lives. Identification of many species can be determined by the cases, as each is constructed differently. Some larvae use plants material for these whilst others use grains of sand or even snail shells. As caddis larvae are generally slow moving, crawling around on pond bottom and amongst vegetation, the case helps protect them from predators. Not all species have larvae with cases; some are free-living making silk tunnels and nets.