The house are usually mobile

W.G. Hardy (édit.), Alberta, a Natural History, Alberta, The Patrons, 1975, p. 244.

However, they differ from most caterpillars in that they live in water and in houses which they construct. The houses are usually mobile and are made of grass stems, twigs, sand grains, or little pebbles stuck together with silk. Each house forms a tube inside which the larva remains anchored by means of a pair of hooks at its posterior end.