Milo Burdette Hillegas & ‎Thomas Henry Briggs, The Classroom Teacher, vol. 8, Chicago, The Classroom Teacher, 1927, p. 222

The early history of caddis worm is not well know. From June to the following May, however, we may find these creatures with their curious cases in the brooks and ponds. These portable cases may be made of tiny stones or of sticks fastened together with a silk to make a cylindrical home. The slender body of the caddis worm fits the house it has built, and its head and legs protrude in search of prey. Whenever the worm ventures forth a silk thread is attached to the case to guide it back. Pupation takes place inside the case which  has served as a protection for nearly a year