There is quite a large class of Spiders of nocturnal habits, whose only precaution by day is to sit perfectly still and be mistaken for something else. We have referred to the adaptation in colour of our English species, Misumena vatia, to the flowers in which it lies in wait for prey. Bates[[297]] mentions exotic examples of the same family which mimic flower-buds in the axils of leaves. Herbert Smith says of a spider which sits upon a leaf waiting for prey: “The pink three-lobed body appears just like a withered flower that might have fallen from the tree above; to the flies, no doubt, the deception is increased by the strong sweet odour, like jasmine.”
Trimen[[298]] describes a Cape Town species which is of the exact rose-red of the flower of the oleander. “To more effectually conceal it, the palpi, top of the cephalothorax, and four lateral stripes on the abdomen are white, according remarkably with the irregular white markings so frequent on the petals of Nerium.”
The same observer, approaching a bush of the yellow-flowered Senecio pubigera, noticed that two of the numerous butterflies settled upon it did not fly away with their companions. Each of these he found to be in the clutches of a spider, whose remarkable resemblance to the flower lay not only in its colour, but in the attitude it assumed. “Holding on to the flower-stalk by the two hinder pairs of legs, it extended the two long front pairs upward and laterally. In this position it was scarcely possible to believe that it was not a flower seen in profile, the rounded abdomen representing the central mass of florets, and the extended legs the ray florets; while, to complete the illusion, the femora of the front pair of legs, adpressed to the thorax, have each a longitudinal red stripe which represents the ferruginous stripe on the sepals of the flower.”
Cambridge found in Palestine some species of Thomisidae which, when at rest, were indistinguishable from bits of coarse fleecy wool, or the rough seeds of some plant.
There is perhaps no more curious case of mimicry than that of a spider, Phrynarachne (= Ornithoscatoides) decipiens, which Forbes discovered in Java while butterfly-hunting. It appears that butterflies of the Family Hesperidae have a custom of settling, for reasons best known to themselves, upon the excreta of birds, dropped upon a leaf. Forbes noticed one in this position. Creeping up, he seized the butterfly, but found it mysteriously glued by the feet. On further investigation the “excreta” proved to be a spider. So accurate was the mimicry that he was again completely deceived by the same species in Sumatra. Its habit is to weave upon a leaf a small white patch of web, of a shape which greatly assists the deception, and in the midst of this it lies on its back, holding on by the spines with which its legs are furnished. It then folds its legs over its thorax, and waits for some insect to settle upon it.
In rare cases spiders have come to resemble their enemies the Ichneumon flies. A frequent habit of these insects is to deposit their eggs in the newly-formed cocoon of the spider. The Ichneumon eggs are the first to hatch, and the larvae have a convenient food-supply at hand. Sometimes, however, they adopt another method, and insert their eggs into the body of the spider itself. It is probably in order to avoid this unpleasant contingency that the spider has evinced towards the Ichneumon the sincerest form of flattery.
The Senses of Spiders.
Sight.—Though, as has been shown, spiders are well provided with eyes, their power of vision, in most cases, is by no means remarkable. As might be expected, it is less developed in those of sedentary than in those of nomadic habit.
It is noticeable that, in most spiders, some of the eyes are of a pearly grey colour, and others of a much darker hue. Simon designates the former nocturnal and the latter diurnal eyes, according to the special use which he believes them to subserve.
This view of the matter cannot be regarded as at all established, and has not found general acceptation. Moreover, Pillai[[299]] has shown that certain Attid spiders can change the colour of their eyes by a movement of the internal mechanism. The Epeiridae, spinners of the round web, are certainly, as a rule, very dim-sighted creatures. A fly may be held within an inch of them, but, unless it buzz, it will excite no notice whatever. A careful observation of the performances of the large Garden-spider in securing her prey will soon convince the onlooker that she is guided almost entirely by appeals to her sense of touch communicated along the tremulous lines of her snare. Interpreting these too hastily, she will sometimes rush straight past the entangled fly, and wait for it to renew its struggles before making sure of its whereabouts. Keen sight would be of little utility to such spiders, as they are concerned with nothing beyond the limits of their snare, and within its range they are furnished with the equivalent of complete telegraphic communication.