David Webster, The Angler and the Loop-Rod, Edinburgh & London, William Blackwood,  1885, p. 159.

It was stated that some of these caddis-cases are carried about by the larvae, and others are fixed to the under sides of stones in the water. It is the larvae whose cases are constructed of sand and small stones, that constitute the fisher’s bait. He will find them generally in the deep sides of streams and heads of pools. They are common enough in most rivers and burns.