The larva of a caddisfly, especially one used as bait for fishing; also the protective case it constructs from sand, plant material, and debris.
Etymology uncertain; possibly derived from archaic or dialectal terms for cloth or fabric, since caddis cloth is a type of woven material and the larval cases resemble woven tubes. Alternative theories suggest connection to Scots or Mediterranean trade languages. The term has been used since at least the 16th century in English.
Caddisfly larvae are like tiny architects—they build custom houses by secreting silk and gluing on whatever materials they find: sand, leaves, stones. Some species are so picky they only use specific colors! Humans discovered these weren't just random cases but deliberate constructions, making caddis one of nature's first documented builders.
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