The Minds and Manners of Wild Animals: A Book of Personal Observations

"The trap-door spiders, inhabiting the warmer portions of both the Old and New Worlds, dig a deep tunnel in the soil, line this with a silken wallpaper, then construct a hinged door at the top so perfectly fitted and camouflaged with soil, that when it is closed there is no indication of the burrow. Moreover, the inside portion of the door of some species is so constructed that it may be "latched," there being two holes near the edge, precisely placed where the curved fangs may be inserted and the door held firmly closed. Also, the trap-door of a number of species is so designed as to be absolutely rain-proof, being bevelled and as accurately fitting a corresponding bevel of the tube as the setting of a compression valve of a gasolene engine. "The study of a number of specimens of our southern California species, which builds the cork-type door, including observations of them at night, when they are particularly active, indicates that the construction of the tube involves other material than the silken lining employed by many burrowing spiders. In the excavation of the tube and retention of the walls, the spider appears to employ a glairy substance, which thoroughly saturates the soil and renders the interior of the tube of almost cement- like hardness. It is then plastered with a thick jet of silk from the spinning glands. This interior finishing process appears to be quite rapid, a burrow being readily lined within a couple of hours. "The construction of the trap-door is a far more complicated process, this convex, beautifully bevelled entrance with its hinge requiring real scientific skill. Judging from observations on a number of specimens, the work is done from the outside, the spider first spinning a net-like covering over the mouth of the tube. This is thickened by weaving the body over the net, each motion leaving a smoky trail of silk. Earth is then shoveled into the covering, the spider carefully pushing the particles toward the centre, which soon sags, and assumes the proper curvature, and automatically moulds against the bevelled walls of the tube.