Page:Supplement to harvesting ants and trap-door spiders (IA supplementtoharv00mogg).pdf/95

 *wards to the hinge, which is always placed at the point of bifurcation of the tubes, and having two crowns separated from each other by the gusset-like web of silk which connects the door on either side with the lining of the main tube, one of these crowns fitting into and closing the main tube, while the other fits into the aperture of the branch.

The wedge-shaped structure of the door is seen in its most exaggerated form in the nests of the younger spiders (figs. B, B 1, Plate XVIII.), and becomes less so in the older and larger ones (figs. A 1, A 2). I have even seen some of these lower doors, evidently made by old spiders, which were so much flattened as to bear a considerable resemblance to that of N. Eleanora.

The main tube of the nest is from 10 to 12 inches long, and usually enters the earth almost horizontally, bending downwards from the point at which the branch joins it, and where the lower door is hung. This causes the lower door to lie nearly horizontally when not in use, and its lower crown probably serves, by fitting into the aperture of the branch, to sustain it in this position and prevent it from falling forward. The point of bifurcation is placed, as a rule, much nearer to the entrance of the nest, than it is in the two other branched nests, and occurs usually within two inches of the surface of the earth; so close is it indeed that, on lifting the upper door and looking in, one may frequently see the lower door move across and close the passage down the main tube, pushed by the spider from below. This frequently enabled me to secure the spider without having to follow her to the bottom of the nest; and, when fortune favoured me, I secured a block of earth by one rapid sweep of