External configuration

Robert Patterson, Letters on the Natural History of the Insects mentioned in Shakspeare’s Plays, Londres, Orr, 1838, p. 238-239

The insects of this family are well know to you in their larva state, under the name of case-worms, or caddis-worms, and are to be found in every running stream, and almost in every ditch. Their habitations are extremely singular, and differ considerably, both in the material employed, and in their external configuration. Some are formed of numerous little pieces of grass, and stems of aquatic plants, cut into suitable lengths, and placed cross-ways, forming a rude polygonal figure ; others are constructed of bits of stick, or grains of sand or gravel, cemented strongly together ; and others, again, are composed of fresh-water shells, each containing its own proper inhabitant,-«  a covering, » as Kirby and Spence remark, «  as singular, as if a savage, instead of clothing himself with squirrel skins, should sew together into a coat the animals themselves. »