The sense of touch is extremely well developed in these spiders, but in sight, hearing and smell they are strangely deficient. No response whatever, was obtained to either high or low notes. A cricket sang for hours quite close to a spider which had been kept hungry for several days, without attracting any attention. It is very remarkable, by the way, that insects show no instinctive dread of these formidable creatures, not attempting to keep at a distance, and indeed frequently running over them in trying to find a way out of the cage. Nor do the spiders seem to be at all guided by smell; they evince no knowledge of the presence of insects which emit a strong odour, nor do they react to such tests as those to which the garden-spider was subjected unless strong irritants such as chlorine are employed, in the perception of which it is perhaps unnecessary that smell in the strict sense should take any part.
They have eight eyes—two of them round and rather business-like in appearance, and the others oval or pear-shaped—and they are very sensitive to light, retreating at once from the direct rays of the sun or from a light flashed on them, but they do not appear to see anything at all, recognising neither friends nor enemies by sight, however close at hand. It was far otherwise with a wolf-spider in the same cage. Running towards the Dugesiella it was clearly aware of it at a distance of several inches, and could not be persuaded to approach nearer. But the supremacy of the sense of touch is most striking when the spiders are courting. When the male is seeking the female he seems quite unaware of her proximity unless he accidentally brushes up against her. If he loses contact for a moment he is quite at sea and wanders blindly about, turning, perhaps, to the left when the least motion to the right would bring them together again. This frequently happens when he has accidentally touched the female with one of the hind legs. He immediately turns about, and if she is still there, all is well, but if she has chanced to move out of reach, he is quite at a loss. Neither sight nor sound nor smell guide him, but touch only. The delicacy of this sense, however, is quite remarkable. He seems to be aware at once of the nature of the object which touches him, assuming a threatening attitude if the touch is hostile, or pouncing instantly if hungry and the touch is that of a passing insect. If, however, the insect is lucky enough to escape, it is in no danger of pursuit.
As in the case of many spiders—though by no means of all—his courting is not unattended with peril. The tragic fate which sometimes overtakes the male spider has so hit the popular imagination that there is a general impression that the female spider is a confirmed misanthrope and desires the life of any suitor bold enough to approach her. Not at all! We have simply to remember that spiders are carnivorous and prone to cannibalism. If the female happens to be hungry she makes no nice discrimination between an amorous male and a succulent grass-hopper; if replete, she may find time for the play of softer emotions. The male of D. hentzi appears to be more or less prepared for a hostile reception on the part of the female, for the thighs of his front legs are furnished with spurs at their extremity and with these he holds back and renders powerless her threatening fangs.
There is no doubt that the spider’s delicate sense of touch resides in the hairs with which both body and limbs are thickly clothed. They are of various kinds—fine hairs, bristles, and stout spines—and many of them are supplied with nerve-fibres at the base. The finer hairs are probably not sensory, and they are, in the case of some Avicularid spiders very easily shed, and have a strongly irritant action on the hand that touches them, not unlike the sting of a nettle.
It is not at all unusual for one large Avicularid spider, Psalmopoeus cambridgii, to be brought over to England in cases of bananas from the W. Indies. Mr James Adams of Dunfermline has kept two specimens alive for a considerable time. The first specimen lived in captivity for two years and nine months, during which it moulted five times but grew very little in size. Arriving in September, it was at first fed on flies, and in a few weeks, when these began to fail, it accepted beetles, consuming about three a day. In November, even these insects were difficult to obtain, and recourse was had to cockroaches. At first about three cockroaches a week were eaten but the number decreased until, in the middle of March it ceased feeding altogether, and on April 13 it cast its skin. It moulted again in October, and twice a year for the rest of its life—in spring and autumn. During six months it took no food at all, and very little for four months previously. At the last moult but one it lost a limb, which however, reappeared when the spider again changed its skin, though it never attained the proper size.
With spiders, as with insects, moulting is a very serious matter, involving much more than the mere casting off of an external coat. If all does not go well limbs may easily be lost in the operation, nor is it rare to meet with instances in which the animal has perished in its unsuccessful attempt to discard the old integument.
Mr Adams’ second specimen was kept alive for three years and ten months. It moulted only once each year—in June or July—and it died in the act of casting its skin. In the case of these spiders, also, it was noted that insects supplied to them as food displayed no fear whatever. There were always a few cockroaches in the same box, and they were often observed actually with the spider in its nest, but no notice was taken of them unless their host chanced to be hungry. A photograph of this spider is given in the Frontispiece.
It is an interesting fact that many of the Aviculariidae of Southern Asia and Australia possess a sound-producing apparatus which is entirely lacking in African and American forms, but this is a subject which deserves a chapter to itself.