The spider seeks the highest spot available, faces the wind, and straightens its legs and body, standing, so to speak, upon its toes, its abdomen with its spinning tubes being elevated as much as possible. Streamers of silk presently appear from the spinnerets and float gently to leeward on the light current of air. The spider has no power to shoot out a thread of silk to a distance, but it accomplishes the same result indirectly by spinning a little sheet or flocculent mass which is borne away by the breeze.
Fig. [189].—Young Spider preparing for an aerial voyage. (After Emerton.)
When the streaming threads pull with sufficient force the animal casts off, seizes them with its legs, and entrusts itself to the air, whose currents determine the height to which it is carried and the direction of its journey. The duration, however, is not quite beyond the spider’s control, at all events in calm weather, for it can furl its sail at will, hauling in the threads “hand-over-hand,” and rolling them up into a ball with jaws and palps.
This curious ballooning habit of young Spiders is independent of the particular family to which they belong, and it is remarkable that newly-hatched Lycosidae and Aviculariidae, whose adult existence is spent entirely on or under the ground, should manifest a disposition to climb any elevated object which is at hand.
The “Gossamer,” which so puzzled our forefathers, is probably no mystery to the reader. It is, of course, entirely the product of Spider industry, though not altogether attributable to the habit of ballooning above described. Only a small proportion of gossamer flakes are found to contain spiders, though minute insects are constantly to be seen entangled in them. They are not formed in the air, as was supposed long after their true origin was known, but the threads emitted by multitudes of spiders in their various spinning operations have been intermingled and carried away by light currents of air, and on a still, warm day in spring or autumn, when the newly-hatched spider-broods swarm, the atmosphere is often full of them.
They rise to great heights, and may be carried to immense distances. Martin Lister relates how he one day ascended to the highest accessible point of York Minster, when the October air teemed with gossamer flakes, and “could thence discern them yet exceeding high” above him. Gilbert White describes a shower, at least eight miles in length, in which “on every side, as the observer turned his eyes, he might behold a continual succession of fresh flakes falling into his sight, and twinkling like stars as they turned their sides toward the sun.” The ascent of a hill 300 feet in height did not in the least enable him to escape the shower, which showed no sign of diminution.
The mortality among very young spiders must be exceedingly great; indeed, this is indicated by the large number of eggs laid by many species, an unfailing sign of a small proportion of ultimate survivors. We shall have, by and by, to speak of some of their natural enemies, but apart from these their numbers are sadly reduced by the rigours of the weather, and appreciably also by their tendency to cannibalism. A thunderstorm will often destroy a whole brood, or they may perish from hunger in the absence of an adequate supply of insects minute enough for their small snares and feeble jaws. In the latter case they sometimes feed for a time on one another, and it is even said that two or three of a brood may be reared on no other food than their unfortunate companions.
The large and handsome Garden-spider, Epeira diademata, has been known, when well fed, to construct six cocoons, each containing some hundreds of eggs, and some species are even more fertile, while their adult representatives remain stationary, or even diminish in number.
Spider-Webs.—Some account has already been given of the external and internal spinning organs of Spiders. Within the body of the animal the silk is in the form of a gummy fluid; and this, being emitted in exceedingly fine streams, solidifies as it meets the air. It cannot be shot out to any distance, but the animal usually draws it out by its hind legs, or attaches it to a spot, and moves away by walking or allowing itself to drop. It has some power of checking the output, and can stop at will at any point of its descent; but the sphincter muscles of the apertures are but weak, and by steady winding the writer has reeled out a hundred yards of the silk, the flow of which was only then interrupted by the spider rubbing its spinnerets together and breaking the thread.