The tube fastened

Jeremy Lingard, The zoo in my backyard : a sort of autobiography, New York, A.S. Barnes and Company, 1966, p. 165.

Few suspect, for example, that beneath the surface of almost any stream lives a curious insect which makes a house out of pieces of grit or vegetation.
It is the larva of the caddis-fly, and its house takes the form of a portable tube or horn. When so inclined the caddis-fly larva can partially emerge from one end of its home and walk along the revier bed, the tube fastened over its hindquaters. The freshwater spider…