Towner H. E. Coston, Beneath the Surface, The Cycle of River Life, Londres, Country Life, 1938.

On emerging from the eggs stage, they are entirely naked, some know as free living caddis, as the Rhyacophila, do not make cases for themselves, but others are either more industrious, more careful, or more intelligent. With the aid of a cement-like saliva, some form perfect tubular mosaic homes out of tiny grains of sand, others use small snail shells, and are not, and I am sure they do not seek leave of the occupants, who must be sometimes very incovenienced; whilst others spin bits of bark and leaves of weed into a home. As they grow, so must they make their homes more commodious. Many are voracious and predatory, preying on the eggs of fish, and the eggs of other sub-aquatic flies; others confine their more moderate attentions to the incrusting algae which adheres to pebbles and boulders. This incrusting algae is that sort of chalky deposit which one so often finds on under-water objects.
The collection of caddis cases alone is rather a fascinating minor occupation, a sort of a by-the-way business, for one so seldom finds two which are exactly alike. The variety of shapes and forms is truly amazing, and one cannot help but marvel at the efficency and artistry of a tiny masons who work under the directorship of Nature.