They look like part of the bottom of the stream

Wilda Ross, Can you find the animal ? Ill. John Hamberger, New york, Coward, McCann & Geoghegan, 1974.

Fish like to eat caddis worms when they can find them crawling on a stream bed. When caddis worms are still, they look like part of the bottom of the stream. The caddis worm also use the garbage kind of camouflage in a skillful way. It spins a silken tube about the body, closing one end. Then it fastened bits of dead leaves and twigs to the outside of the tube with more silken threads. When resting, the caddis worm pulls its head and legs back into the tube.