Millicent Selsam, See through the lake, Ill. Winifred Lubel, New York,  Harper & Row, 1958,  p.34.

But here’s something we haven’t seen before. Its head is sticking out of a tube of sticks ans stones. It’s a caddis worm- the young stage of the caddis fly, which is an insect somewhat like a moth. The caddis worm lives in this tube, which it makes out of bits of pebbles, grains of sand, shells, and scraps of plants, all  glued together with a stricky saliva. The lake water is clear, so we can peer down and watch these caddis worms hauling their tubes like trailers across the muddy bottom.