Fred Kitchen & Clifford W. Greatorex, What the countryman wants to know, Londres, Victor Gollancz, 1948, p. 194-195.

HOW LONG DOES A CADDIS-WORM TAKE IN BUILDING ITS CASE ?

One authority gives between four and eight hours one of the present writers has found that caddis-fly larvae (« worms » or « grubs »), when gently ejected from their cases and placed in a vessel of water containing tiny pebbles, sand, soaked leaves, and the shells of that familiar little freshwater snail, Planorbis, constructed their cases in periods ranging from three hours fifteen minutes and ten hours twelves minutes.
The pieces of material utilised are fastened together by means of silk, and the larvae dwells in the tube thus formed. Sticks and straws, also grass-blades, are cut to the requisite length before being incorporated in the structure.