[CHAPTER V]
TRAP-SNARES AND BALLOONS
There are some interesting variants of the circular snare spun by some exotic Epeirids. One North American species spins it in a horizontal position and then raises the centre, and, by an elaborate system of stay lines from above, converts it into a very accurately shaped dome. A whole group of orb-weavers habitually decorate a sector of the snare with bands of flocculent silk, the object of which for a long time puzzled arachnologists, till it was observed that the spider drew upon this reserve supply of material to wrap up particularly obstreperous insects. It is not unusual for a spider of one of the common species to remove a whole sector of the snare, and by stretching a line from the centre to a place of retreat along the gap thus formed, to provide an unencumbered avenue between its home and its post when on duty. For it must not be forgotten that a spider has to walk warily on its own web, and must avoid, as far as possible, treading on the adhesive lines, or delay and damage to the structure are sure to ensue.
As a rule the circular snares of the different British species are of a very uniform pattern, differing chiefly in the degree of neatness with which they are constructed, and in certain minor details of the “hub,” but we have one spider, Hyptiotes paradoxus—an exceedingly rare species, scarcely ever seen beyond the limits of the New Forest—which makes such a strange snare that it seems a pity to omit all mention of it. It consists of a sector—about one sixth of the full circle—comprising about four radii with cross lines. From the point where the radii meet, a “trap-line” connects the sector to another point of attachment; on, or rather under, this trap-line, the spider takes up its position, hauling it in so as to tighten the web and to leave a slack portion of the line between the points where it holds on by its front and hind legs. When an insect impinges on the web and causes it to tremble, the spider immediately lets go with its fore legs, and the consequent vibration of the web helps to entangle its prey.
The circular snare is the highest form of spinning work attained by spiders, and there is little temptation to expend much time in studying the cruder structures that meet the eye everywhere, but two other types are worth a brief notice. Examine any garden bush—particularly a holly bush, of which the rather rigid leaves provide excellent points of support—and you will find numberless small webs made without any discoverable method, the lines crossing one another at random in all directions. These are the snares of some species of Theridion, and if the webs lack interest the spiders themselves are worth looking at, for they are nearly always quite prettily ornamented.
The other common type of snare is that of Linyphia. It is larger and of more definite design, consisting of a finely-spun hammock stretched horizontally, and surmounted by a labyrinth of irregular lines. Flies entangled in the labyrinth fall upon the hammock in their struggles to escape, and the spider is at hand—always on the under surface of the hammock—to ensure their capture.
Having noted these three common types of snare, let us leave the garden and choose a new field for our observations.
If it is an absolutely calm sunny October morning it will be a suitable occasion for visiting an iron railing, the “knobbier” the better. Early summer will do, but late autumn is generally more fruitful. Almost any railing will serve, but the most satisfactory kind is one with the uprights surmounted by round knobs, and not by spikes. We see at once that the knobs, and the upper rail are glistening with silken lines; many spiders have obviously been at work there. Lines streak the top-rail in all directions, stretch from knob to rail, or from knob to knob if not too distant, while here and there loose ends or streamers flutter gently in the slight currents of air. And closer inspection reveals various small objects moving among this labyrinth of threads. Most of them are spiders, though insects, and particularly weevils, are not wanting. No doubt the weevils know their own business, though the writer has not been taken into their confidence, but the spiders are the particular object of our investigation. And first of all note that it is a veritable race-congress of spiders; the most varied groups are represented. Wolf-spiders (Lycosidae) which under ordinary circumstances rarely leave the ground are found in company with crab-spiders (Thomisidae), jumping spiders (Attidae), as well as Epeiridae and Theridiidae of which we already know something. They have only one thing in common—they are either small species or small and immature specimens of larger species. They seem to be scrambling about in a meaningless sort of way, paying little or no attention to each other—which is odd, for spiders are terrible cannibals, and as a general thing it would be exceedingly unsafe for a small spider to rub shoulders with a larger one of a different species.