Curious investigators

Glenn O. Blough & Julius Schwartz & Albert J. HuggettElementary School Science and how to teach it, New York, Henry Holt & Company, 1958, p. 294.

The larva of these insects live in streams and ponds. The larva of one kind of caddis fly cements a tube from grains of sand and mineral particles that it finds in the water. Another type makes a « log-cabin » case out of twig fragments. This case is the house of the caddis fly until it emerges as an  adult; it is constructed to admit food and protect the young fly from water currents.

If the log-cabin caddis-fly larva is taken out of its case and put in a jar of pond water, it will build a new case out of the available materials. Some have been reported to use fine bits of transparent film or cellophane that were placed in the jar by curious investigators.