Cecil Warburton

JUMPING SPIDERS

We are not in the land of the jumping spiders or Attidae, and our few and sober-coloured examples of the group give but a feeble idea of the Attid fauna of tropical countries where these creatures abound and often rival the “ruby-tail” flies in the brilliancy of their hues.

Fig. 8. Salticus scenicus, female, × 4.

It is one of the largest groups, numbering several thousand species, but the British list includes barely thirty, and most of these are of rare occurrence, or at all events exceedingly unlikely to be met with by any but the most energetic collector. Indeed it may be said that there is only one British species which we may look forward with tolerable confidence to finding upon some sunny wall or fence in the summer, in whatever part of the country we may be. This is Salticus scenicus, sometimes called the Zebra Spider. Though absolutely dowdy in comparison with most of its tropical cousins, it is a not unattractive little creature, and illustrates sufficiently well the characteristics of its tribe. Armed with a pocket-lens, a glass tube or two, and—more necessary still—the very largest amount of patience we can summon, we go in quest of the zebra spider. A tarred fence is a good hunting ground, because the spider, if present, is readily seen, but if this is drawn blank we must have recourse to a wall, where sharper eyesight will be required.

Our quarry is of small size, not more than a quarter of an inch long in the body, which resembles that of the wolf-spiders in build, the abdomen not rising above the level of the fore-body or cephalothorax. It is thickly clothed with short hairs—black, white, and grey—so arranged as to show oblique zebra-like stripes on either side of the abdomen. The legs are short and robust, very different from the long thin limbs of the garden-spider; especially strong are the fore-legs. The head is broad and square, with a high perpendicular forehead, but the most remarkable features are the eyes.

On the vertical front are four splendid eyes. The wolf-spider’s eyes were large, but these, in comparison, are immense, especially the median pair. Their axes are directed straight in front. Four other eyes are placed on the top of the head, far apart from each other, the more forward pair very small, the hind pair of moderate size. In some Attid spiders these great anterior eyes are wonderful objects under the microscope, deep sea-green in hue and fringed with coloured hairs. They form a veritable battery which the spider brings to bear upon the object of its chase. Human eyes, to match them in comparative size, would literally have to be as large as saucers!

If we are in luck, we soon descry a Salticus showing up boldly against the black surface of the fence, and to set ourselves to watch its antics attentively. One thing strikes us at once; it is quite at home on a perpendicular surface—nay, on the under side of a horizontal beam, for that matter. Now a garden-spider would have great difficulty in maintaining itself in such a position unless well supplied with silken lines to which to cling; evidently there is some difference in the structure of the feet of these spiders which may be worth investigating later on.

Also we notice some odd tricks of movement in the jumping spider; a curious way of exploring the surface on which it is working by a succession of short runs alternately with periods of absolute stillness as though on the qui vive; a noticeable freedom of movement between the fore- and the hind-bodies so that its battery of eyes may be directed to this side or that; sometimes an elevation of fore part as though for the purpose of obtaining a wider view.

We may have to wait long before we see it successful in the chase. It will often patiently explore a large area, testing the surface with its palps as it goes, without any obvious reward. It conscientiously searches all depressions and crannies, and, sometimes remains in them for a considerable time—perhaps to devour some minute creature which did not call into play its special methods of attack. At last it sights a small insect which has alighted on the fence a few inches away; we see it turn its head in that direction and remain motionless. Soon it begins to edge nearer in a stealthy manner, striving to approach its prey from behind, till, with a sudden spring, it pounces on its back. Not always is the spring successful; often the insect sees its peril at the last moment and takes to wing. But in this case, how does the spider avoid a fall? We see, what we had not noticed before, that it is anchored to the fence by a silken line; indeed all the time it has been hunting it has been trailing behind it an exceedingly fine thread of silk which it has attached at frequent intervals to the fence, so that it can check its fall at will in the case of accident. At the right angle, we may see the delicate filaments glistening in the sun over the surface of its explorations. The garden-spider entangles its prey in a web, the wolf-spider runs it down by sheer strength and speed, but the jumping spider stalks it like a Red Indian.

The actions of the spider make it quite evident that its power of sight is well developed. Mr and Mrs Peckham, whose remarkable observations on the mating habits of jumping spiders must presently be considered, established friendly relations with some of their captives which became so tame as to jump on their hands and take food from their fingers. They frequently induced them to jump from a finger of one hand to one of the other, gradually increasing the distance up to eight inches. They also twice observed a male chasing a female upon a table covered with jars, books and boxes. “The female would leap rapidly from one object to another, or would dart over the edge of a book or a box so as to be out of sight. In this position she would remain quiet for a few moments and then, creeping to the edge, would peer over to see if the male were still pursuing her. If he happened not to be hidden, she would seem to see him, even when ten or twelve inches away, and would quickly draw back.”

Moreover that they have the ability to discriminate colours has been shown by their behaviour when imprisoned in cages consisting of a series of communicating chambers each with a glass top of a different hue. They show a marked preference for the red chamber under these circumstances while the least attractive colour seems to be blue.

It has been known for a long time that the males of many kinds of birds—and especially of the more ornamental species—are accustomed to perform the most extraordinary antics in the presence of the female at the time of mating. The Peckhams made the unexpected discovery that precisely similar “love dances” took place in the case of the jumping spiders. Even the comparatively sober-coloured “zebra spider” performs a weird pas seul in courting its mate, but its display is feeble compared with that of some of the more ornate of the Attidae.

Certain isolated observations on captive jumping spiders led these observers to suspect that the mating habits were unusual and worthy of accurate investigation, and they laid their plans accordingly, taking their summer holiday a month earlier than usual, so as to miss nothing of the pairing season, and including in their party an artist whose drawings should furnish an indubitable record of the attitudes assumed by the male spiders in their evolutions.

On arriving at their destination they found a small species, Saitis pulex, with no great claims to remarkable beauty, mature, and ready to pair. A female was placed in one of the experimental boxes which had been provided in advance, and a male was admitted on the following day. He sighted her at a distance of twelve inches, and showing signs of excitement, advanced to within about four inches and then performed a most ludicrous dance—something in the nature of a “highland fling,” in a semicircle before her, she, in the meantime, moving in such a manner as to keep him always in view. His exact behaviour was this: he extended all the legs—and the palp—on the left side, folding the first two legs and the palp of the right side under him, and leaning over sideways so far as nearly to lose his balance, and in this attitude he sidled along towards the lowered (right) side till he had described an arc of about two inches; then the position was instantly reversed, the right legs being extended and the left folded under, and the arc retraced. A male was seen to repeat this performance 111 times! He then approached nearer and when almost within reach “whirled madly around and around her, she joining and whirling with him,” after which she accepted him as a mate.

The next species to engage attention was an Icius. It was noteworthy that although the neighbourhood was well known to the experimenters they had never met with this spider before, but for a few days it swarmed on the fences just as birds are known to assemble from all quarters for the so-called “love dances.” After the mating season the spiders wandered off into the woods again and were seen no more.

The performance was much as before, but the spiders assumed different attitudes. The female lay flat on the ground with her front legs raised; the male danced on the six hind legs, with the front legs lowered and meeting at the tips. The males of this species were exceedingly quarrelsome, sparring frantically whenever they met, but their battles were entirely bloodless. “Indeed,” say the observers, “having watched hundreds of seemingly terrible battles between the males of this and other species, the conclusion has been forced upon us that they are all sham affairs, gotten up for the purpose of displaying before the females, who commonly stand by, interested spectators.” In the case of one species, after two weeks of hard fighting between the males, the Peckhams were unable to discover one wounded warrior. The females, on the other hand, were often really formidable. Phidippus morsitans is an example. The male has handsome front legs, thickly fringed with white hairs, and he displays these to the best advantage in his love antics. Two males supplied in succession to one female “had offered her only the merest civilities when she leaped upon them and killed them.”

In the case of most of the spiders whose love-dances were investigated, the chief ornamentation of the male consisted of fringes of white or coloured hairs on the face, the palps, and the front legs, and they kept these parts always before the females, displaying their glories to the utmost advantage. The male of Habrocestum splendens, however, possesses an extremely brilliant abdomen, and, lest anything of its beauty should be lost upon the object of his admiration, he varies the ordinary performance in a remarkable manner. He often pauses in the dance, and, raising his abdomen, “strikes an attitude” in which he remains motionless for half a minute. Moreover he frequently turns his back on the female—a most unusual occurrence in the course of these antics.

The males of one species, Philaeus militaris, were observed to capture and keep guard over young females, which they imprisoned in webs spun for the purpose until they had undergone their last moult and were mature, chasing away all intruders in the interval.

The jumping spiders furnish a much stronger case for those who believe that ornamentation plays an important part in sexual selection than do either birds or butterflies. With regard to the birds it has been objected, first, that there is little evidence that the females pay much attention to the antics of the males, and secondly, that practically all the male birds pair, whatever their claims to pre-eminent beauty. Now in the case of the jumping spiders the females follow the performances of the males with the utmost attention, and seeing that the males are present in large numbers when the females begin to appear, the latter are certainly in the position to reject such mates as do not please them.

The mere relation of the results of this most interesting investigation conveys no hint of the unwearied patience and close observation necessary to those who would surprise the secrets of nature. One is apt to infer that it is only needful to place some spiders in a box, establish oneself in an arm chair, and ring on the performance, so to speak. The Peckhams modestly remark: “The courtship of spiders is a very tedious affair. We shall condense our descriptions as much as possible, but it must be noted that we often worked four or five hours a day for a week in getting a fair idea of the habits of a single species.”