The upper part of this nest is shown of the natural size in [Plate XVII] with the spider (Nemesia suffusa, Camb.[140]) which constructs it. This is again a wafer nest without any lower door, and this absence of a lower door alone distinguishes it as a type from the branched nest represented at F in the diagram, just as the same deficiency separated the Bordeaux type from that at fig. E.
[140] We have again in this instance an exemplification of the rule that a new type of nest indicates the presence of a new spider, and hitherto, this rule has proved without exception. Mr. Pickard-Cambridge's description of N. suffusa will be found at p. 295, below. Its slender proportions, cylindrico-ovate abdomen, marked with narrow linear chevrons, and caput without, or almost without, any median line or marking, form some of its more striking characteristics.
In this new single-door branched type, the branch makes a more or less acute angle with the main tube, and reaches the surface of the ground, but is there closed by a layer of particles of earth slightly bound together with silk, forming an immovable cover or thatch. This cover constitutes, however, but a slight obstruction and could easily be torn away by the spider if she needed to use this passage as a way of escape.
These nests were tolerably plentiful at a place called Les Mourines, a short distance from Montpellier, where they were mixed with cork nests in the steep hedge banks. The nests were from 8 to 10 inches deep, and, as in all the trap-door nests which I have examined, were tenanted by the female alone. It seems strange that this spider, building as she does a nest apparently but poorly furnished either for concealment or defence, should be able to enter into competition with N. cæmentaria, whose solid, closely-fitting door appears so perfectly contrived for both. It will probably be found, however, when we are better acquainted with their respective ways of life, that they are really more nearly on a footing than they seem to be at first sight. I detected the remains of ants and the elytra of a beetle in one of these branched single-door nests. Now these may also be found in cork nests, so that Nemesia suffusa evidently competes with cæmentaria for its food, and this is of course the main cause of contention between all living creatures.
It is possible, that, if we knew all the uses to which the branch is put by the spider which constructs it, we should find that the advantages derived in the way of security from the existence of this second passage, counterbalance those possessed by the cork nest, which, though so perfectly closed, has only the one tube, and no other possible way of escape.
It may perhaps be no more than a coincidence, but we can scarcely avoid commenting upon the fact, that, just as this Montpellier wafer nest is simpler in construction than any found along the Riviera, so in like manner is the Bordeaux nest simpler than that of Montpellier. It thus becomes tempting to ask whether, in the case of these wafer nests, we shall not discover that the colder and damper climates are the homes of the builders of the simpler types, while the warmer and drier ones, where more food, more enemies and more competitors are found, are reserved for the architects of the more complicated nests.
Doubtless naturalists will soon discover wafer nests on the slopes of the Pyrenees, as for example at Pau and other winter stations in South-western France; and perhaps the coast of the Bay of Biscay may also yield specimens, even to the north of Bordeaux. If so, this curious speculation as to whether there is any relation between simplicity of structure and warmth of climate, will be put on its trial.
About the very time when I was engaged in digging out these new wafer nests at Montpellier, the celebrated arachnologist, Dr. L. Koch of Nuremberg, had just published[141] an account and figure of a very remarkable nest which he had received from Australia, and which, though differing both in form and proportions from the Montpellier nest, may nevertheless perhaps be referred to the present single-door branched wafer type.
[141] Dr. L. Koch, Arachniden Australiens, 10te. Lieferuug, Nurnberg, 1874, tab. xxxvii. fig. 3, p. 484.
This Australian nest, the exact habitat of which is not mentioned, is constructed by a spider now described for the first time under the name of Idioctis helva. The nest has a wafer-door about the size of a sixpence, closing a vertical tube less than half an inch long, which meets and opens into a horizontal tube about three inches in length, and forms with it what may be roughly likened to the figure of a capital T inverted, thus, ┹.