Debris or leaves in the water

R. D. Hughes, Living Insects, The Australian Naturalist Library, Sydney & Londres, Collins, 1975, p. 249.

When the larvae hatch they conceal themselves under debris or leaves in the water. Most species then construct around themselves a silken tube, decorated or camouflaged with fragments of a variety of materials. Each of these species has its own preference for grains of sand, pieces of wood, plant-stems or snail-shells, etc.