I have seen N. Manderstjernæ snatch at insects in this way during the daytime, and I well remember how I started on one occasion when, as I was looking fixedly at a small blue gnat which I had taken for a moth, I saw the earth suddenly open and one of these spiders partly emerge, make a swift stroke at the insect, and withdraw again as swiftly.
I have found the remains of ants, of beetles of many species and different sizes, of wood-lice (Oniscus), and of earwigs (Forficula) in the nests of N. Eleanora and N. Manderstjernæ, and the wings of a large green field-bug in the nest of the former. I have only once detected traces of food in the dwellings of Cteniza Moggridgii, and these consisted of minute fragments of the integuments of insects, none of which were certainly recognisable, though I believe that they partly consisted of the coats of a small species of ant. The rarity or complete absence of the wings of insects which habitually fly rather than crawl on the ground, and my inability to discover either snares or any evidence that these spiders ever leave the nest, lead me to believe that they live (at any rate from October to May) by dragging into their nests any insects which approach within reach.
Ants, earwigs, beetles, and wood-lice are precisely the very creatures which would fall a prey to the spider without obliging her to leave her nest, and it is accordingly their remains that we find.
On one occasion, however, at Montpellier, my sister detected N. cæmentaria in the act of devouring a fair-sized caterpillar, to obtain which there is some reason to think she must have left her nest. We were out together on the 8th of May last (1874), hunting for the new wafer nests of that district, under the kind guidance of M. Lichtenstein, when my sister called our attention to a caterpillar, the body of which partly projected from the tube of a cork nest (N. cæmentaria), and prevented the lid from closing.
On closer examination we found that the spider was in the act of devouring the caterpillar, and had already sucked out the juices from the anterior portion, while the middle and posterior parts of the body still resisted, and the legs clung tenaciously to the lip of the nest.
M. Lichtenstein told us that this larva, which when entire must have been rather more than an inch long, was that of the mullein moth (Cucullia verbasci).
It was not full grown, and as there were no mullein plants within some two feet of the nest and this caterpillar will not leave the plant on which it feeds unless compelled, it would seem as if the spider must have gone afield in order to capture it. It is possible, nevertheless, that the caterpillar may have fallen within reach of the spider when blown off the mullein leaves by the wind.
I have, unfortunately, but few details to give of the nocturnal habits of the trap-door spiders. It would appear, however, that they are more active by night than by day, and that it is more common to find their doors ajar at night, with the spiders posted on the look-out at the narrow opening. This is borne out by my observations on captive spiders, to which I shall allude shortly.
When at Hyères on the 11th of May, 1873, the evening being very warm and a bright moon shining, I went at 8:30 P.M. with my father and sister to see what the spiders would be doing on a hedge bank where we had previously marked five cork and eight wafer nests. The moonlight did not fall upon this spot, but I was provided with a lantern, and by its light the nests at first appeared to be tightly closed, but we soon perceived first one and then another with the door slightly raised, ready to close on the smallest alarm, whether from a footfall or from the flickering of the lamp. When the light of the lantern was steady it did not appear to frighten the spiders in the least, even when brought to within a few inches of the door,[148] and this enabled me to watch them very closely. On either side of the raised door of one of the wafer nests I could see the feet of the spider projecting, and just at that moment I caught sight of a beetle close at hand, feeding on the topmost spray of some small plant below. Using every precaution, I contrived to gather the spray without shaking off the beetle, and gradually pushed it nearer and nearer to the nest. When it almost touched the lip of the nest the door flew open, and the spider snatched at the beetle and dragged it down below.
[148] This had been observed before both by my father and Mr. Dillon when watching the trap-door spiders at night at Mentone.