Around their bodies

John Denison Champlin & Frederic Augustus Lucas, The Young Folk’s Cyclopaedia of Natural History, New York, Henry Holt, 1905, p. 92

They are commonly called Caddis Worms, and are well know to anglers, who use them for bait. They construct around their bodies cases of bits of sticks and leaves, grains of sand, fragments of shells, etc., which they fasten together in a rough sort of fashion.