Now that attention has been drawn to the existence of this new type of nest, I fully expect that Nemesia meridionalis will be found at many points along the Riviera and in the whole Mediterranean region, but I have hitherto only discovered it at Mentone and Cannes. Mrs. Boyle saw one of these nests in the Pallavicini gardens near Genoa, and there seems every reason to believe that certain nests which have been detected near Naples and in Ischia, will, when better known, be found to be of the branched double-door type.
It seems probable that our spider belongs to the species which was first described by M. Costa,[69] under the name of Mygale meridionalis, though, if we are to rely implicitly on the figures and detailed account given by this naturalist, we must suppose that it constructs a different nest in Southern Italy from that which it makes on the Riviera, and one which, although it agrees in most other respects, is destitute of the characteristic subterranean door.
[69] Fauna del Regno di Napoli, (vol. containing Animali Articolati, classe ii. Aracnidi: incomplete, Naples, 1861), p. 14, tab. i. figs. 1-4. See [Appendix A].
It is more likely, however, that M. Costa has overlooked the existence of the lower door, though it is strange that he should have done so, as he says that the nests "sometimes have a double aperture, and the upper portions of the burrows meet and anastomose at about two inches distance," thus showing that he was aware that the tube is branched.
One more nest only now remains to be described, and this is again an example of a new type—namely, of that which I have distinguished as the unbranched double door ([Plate XII.]), the work of Nemesia Eleanora. This nest is never branched, and its second and subterranean door is situated from one to four inches below the surface door, and only serves to close the one tube which is narrowed above the insertion of this lower door. Here, as in the branched nest, the thin and wafer-like surface door appears to serve principally for concealment and the lower one for resistance. This latter, made out of earth encased in strong white silk, is from one to two lines thick, and has, at the end away from the hinge, a similar appendage to that found in the lower door of the branched nest. This appendage serves, I imagine, as a kind of ear by which the door, when firmly jammed into the tube on the approach of an enemy, may be pulled down again as soon as the alarm is over. As in the branched nest it has the upper surface concave and the lower slightly rounded, so that when drawn back and not in use it may not obstruct the passage. The sides of this lower door slope a little, so that the crown is smaller than the base; and this is important, because it causes the door to fit more tightly when driven upwards into the tube, acting on the principle of an inverted cork door.
Plate XII.
In form this door is somewhat elliptic, but much broader and shorter than the second door of the branched nest, and it is frequently of a nearly horse-shoe shaped outline. The second door of the branched nest is necessarily longer, having to perform the double function of closing the opening to the branch and the passage of the main tube.
In either case, however, these doors will be found to be more or less elliptic, and this is necessarily so, for, lying as they do when in use in a plane which cuts the subcylindrical tube obliquely, they have to fill a somewhat elliptical area.[70]