- any of numerous aquatic insects constituting the order Trichoptera, having two pairs of membranous, often hairy wings and superficially resembling moths.
Most caddisfly larvae live in cases they build out of sand, rock, twigs, leaf pieces, and any other kind of underwater debris. Some even generate their own cases out of silk. There is tremendous variation in case style and also in the way the larvae manage their cases: whether they replace it as they grow or renovate their old one, and whether they carry it around or fix it to an object.
"'Wizards always used to build a tower around themselves, like those...what do you call those things you find at the bottom of rivers?'
"'Caddis flies is what I meant,' said Rincewind."
- Terry Pratchett, Sourcery