Anonyme, A Selection of Lectures delivered before the Sunday Lecture Society, parties 1-7, Londres, 1886, p. 5- 6.

There is a kind of larvae called the caddis-worm, which lives at the bottom of fresh water streams. At the bottom of fresh water streams it constructs for itself a tubular shell, fitting close to its worm-like body. This tubular or cylindrical shell is constructed of a large number of small particles of gravels, sand, bits of leaf, and so forth, all glued together by a secretion from the animal’s body. Now, it has been quite recently discovered by a very competent observer Mr W. MacLachlan F.R.S and principal entomologist in this country, that when the caddis-worm finds its tubular shell coming too heavy, so that it has difficulty in dragging it about the bottom of the stream, it will glue into the structure small splinters of wood, in order to cause the tubular dwelling to have less specific gravity, to make it lighter, and therefore more easy for the worm to drag about the bottom of the stream…