Supplement to Harvesting Ants and Trap-Door Spiders

by John Traherne Moggridge; Octavius Pickard-Cambridge

The hedge-banks near Hyères, and also about the railway station of the same name, which is some 4 miles from the town itself, are frequently tenanted by this spider. During a short stay there in May, 1873, I secured a large number of specimens, and verified the structure of the nest by a careful examination of thirty-eight examples. The nest is invariably branched and furnished with a lower door, but the branch is of variable length, usually short, and never, as far as I could detect, quite reaches the surface. In some cases this branch was so short that it could scarcely contain the spider, and, under these circumstances, it is not easy to conceive any other use for it than that of retaining the lower door when not in use. It may, however, enable the spider to take up a rather better position when engaged, as she frequently is if disturbed, in keeping the main tube closed by pressing the lower door upwards with her feet, for then her head points downwards, and her abdomen rests in the branch.

Plate XVIII.

I have seen her in this attitude on several occasions when I had cut out a block of earth similar to that figured in the plate. The lower door is quite unlike that of either of the other two double-door wafer nests, being wedge-shaped, tapering from below upwards 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 the knife (a common table-knife), which furnished me at once with a good specimen of the nest and of its occupant.

When the spider has once fairly determined upon resistance, it is scarcely possible to make her retreat without destroying the nest, and, in one case, when I tried to push the lower door down from above, while she was pressing it upwards from below, I found that, without crushing my opponent, I could not succeed.

There were probably young in the nest on this occasion, for I have frequently found them in the nests with the mother at this season. In no case did I even catch a glimpse of the male, and this sex is at present unknown.

The young spiders make their nests at an early age, and there can be no doubt that N. congener enlarges its dwelling from time to time as growth demands, just as the trap-door spiders at Mentone do. Indeed in one of these new Hyères nests I found, outside the main tube and some way above the existing lower door, a former and disused lower door much smaller than the one then in use, and which had evidently belonged to the nest at a previous stage of its development. I have observed this before in the nests both of N. Manderstjernæ and N. Eleanora.