In every brook

Ann Haven Morgan, Field Book of Pond and Streams, New York , G.P. Putmam’s Sons, 1930, pp. 247-248.

Caddis flies are most know by their larvae, the familiar caddis worms or stick-worm which live in every brook (Pl. I), often creeping over the bottom where they can be cleartly seen from the banks. the best know are those which live in cases made of little pebbles, or sticks or leaves which they have cemented together with their own saliva (Fig. 198). When a caddis worm outgrows its case it occasionally squirms out and makes a new one, selecting the same materials and building by the same pattern, but it generally enlarges its case by simply building onto the front edge. It holds itself in the case by draghooks at the hind end of the body but its head and thorax are protruded during its continual clambering. Their gills are filamentous, in many being attached along the sides of the abdomen, completely protected by the case.