Arthur Henry Beavan, Tube, Train, Tram and Car, Or Up-to-date locomotion, Londres, Routledge & Son. 1903, p. 75.

…making roads and galleries, the friction of his fur, set perpendicularly on his skin lining his tube so that the soil did not fall in. The larvae of the humble caddis-fly covered the inside of their cases with fine silk ; and the trap-door spider line dits 1 2- inch long shaft with similar…