Edward George Boulenger, Wild life the world over, New York, Wise & Co, 1947, p. 512-515.

Tiny Creatures of Pond ans Stream

Some of the most interesting aquatic insects are the caddis flies, because of the habit of their larvae, which construct cases for the protection of their soft bodies from materials which they collect out of the water The adult caddies flies are rather mothlike in form, and there are several points of connection between the two groups of insect, so that the moths and the majority of caddis larvae are vegetarians and make portable cases which they take about wherever they go. These cases vary with species and may be composed of grains of sand, small stones and shells, pieces of stick or reed stems, or leaves of water plants. These larvae have a pair of hooks at the tail end with which they cling on to their cases. It is interesting to note that caddis larvae spin silk like caterpillars and use this for holding together and linning their cases.
Some species are carnivorous, and these make fixed cases, which are usually formed of silk only and such debris as may collect on them accidentally. In these lairs the larvae lie in wait and pounce on any passing insect. Caddis FLY When a caddis larva is mature it fixes its case to some support and closes up the ends, and then pupates Inside. The pupa of a caddis fly has its limbs free, not encased in a hard shell like a moth pupa. The hind pair legs are long and fringed with hairs, in a similar manner to the « oars » of the water boatman..