Samuel G. Camp, Fishing with Floating Flies, New York, Outing Publishing Company, 1913, p. 109.

The cases are familiar objects in most clear streams and ponds. There is great variety in the materials used and in the size and shape of the cases, each kind of caddis worm having a particular and constant style of house-building. Grains of sand may be fastened together to form tiny smooth-walled, symmetrical cornucopias, or small stones to form larger, rough-walled, irregular cylinders. Small bits of twigs or pine needles may be used ; and these chips may be laid longitudinally or transversely and with projecting ends. Small snail-shells or bits of leaves and grass may serve for building materials.