Susan MacKeever & Frances Dipper, Freshwater Life of Great Britain and Europe, Junior Nature Guides, Lincoln, Wildlife Watch, 1995, p. 65. 

Caddisfly cases

If you find caddisfly cases with the larvae still in them, you can watch how they build their home. Each caddis case is open at both ends to allow a flow of water through it.

1. If you push a toothpick very gently into the narrow end of the case, the caddisfly larva will come out as it does not like being tickle ! Now you can see it clearly. It will go back inside given the chance.
2. Take aways its old case and keep the larva in a plastic box or jar in a cool, shady place, filled with the pond water that you found it in.
3. Puts in some tiny coloured beads, and it will rebuild its home out of these.
4. Or you can give it pieces of the material it normally uses, such as twigs, or shells, and watch it rebuild its home.
5. It’s best to try this eperiment with several caddisfly larvae, in case one of them is lazy.