Michael Theakston revised annotated by Francis M. Walbran, British Angling Flies, Londres, Sampson Low, Marston, Searle, and Rivington, 1888, p. 107.
These artificial cases are a hollow cylinder of tough texture ans smooth insides. The creeper in its progress covers the outsides with rougher materials, such as small pieces and knobs of sticks, stems, straws, particles of sand, soil, etc., etc., which are fixed to the outside by an adhesive matter, peculiar to the creeper. When a full grown creeper is taken out of its case, its appearance is that of a dull sluggish grub, with but little animation or resemblance to the bodies of their flies. Their legs are short, their motions slow, and they would soon be devoured by the fish had not nature endowed them with the instinctive power to compose an artificial covering around them for shelter and protection.