These cases form the most obvious means of identification

D. Fisher, The Teacher’s Book of Nature Study. W. & R. Chambers, Londres, 1958, p. 178-179.

In most species the aquatic larvae protect themselves by building cases of water-logged vegetation, pebbles and sand-grains which are hauled about by the immates, and these cases form the most obvious means of identification…/… The species forming cases from vegetation inhabit still or sluggish water, or sheltered backwaters of brooks, while those living in the rapid parts of streams prepare cases from sand-grains and small stones which are less liable to be washed away by the current.