The process of the narrative having led, in the last chapter or two, to a discussion of some of the ways in which insects become shaped and coloured through natural selection, sexual selection seemed marked out as the subject for this one. The reason why I have filled it with extracts from a certain very interesting paper has been a better one than that of saving myself trouble. That paper—the most important one perhaps that has ever been written on the subject—is a wonderful confirmation of Darwin’s views, but Darwin, as it appears to me, has not benefited by it in the way that he ought to do in the popular mind. There is no work that I know of, written upon merely popular lines, that brings these facts forward, and yet I feel sure that to large numbers of people, who yet do not care to read books avowedly scientific, they must be extremely interesting, not only in themselves, but as allowing them both to form a judgment on the subject, and on the correctness or otherwise of Darwin’s views—for Darwin is an interesting and picturesque figure far beyond the close borough of science.
Now the general more intelligent public who read, perhaps, widely, but not very deeply or very specially, know that Darwin believed in two forces—natural and sexual selection—by the joint action of which, species, as he held, had been gradually modified and evolved, and they know that the former of these two has been accepted by science, but that to the latter there has been much more opposition, and that it is not—or is not supposed to be—established like the other. Many, perhaps, may have read Dr. Wallace’s Darwinism, a work in which Darwin’s most distinctive and original view—that one whose conception, apparently, he shared with nobody and on which he based much of the argument contained in his Descent of Man—is considered and rejected in a way which makes the title of the book misleading, surely, if not a somewhat comically ludicrous misnomer. All those who have read it, as well as many who have not, will be interested—they cannot fail to be—in the wonderful record of spider courtships contained in these extracts, and having reflected on them, they will, if I mistake not, be much more impressed with the arguments for this part of Darwinism than they were with those brought against it in the book of that name.
All these latter arguments, by the way—the languor of swallows as against the vitality of parrots, trogons, etc.—were well known to Darwin himself; and as no one was, at the same time, more impartial in considering, and more capable of correctly estimating, facts hostile to his own theories, or which, at first sight, might seem to be so, it may not be out of place to end this chapter with a reference to what he thought of them. This we may gather from a statement contained in a paper—the last, presumably, ever written by him—which was read before the Zoological Society but a few hours before his death, and which is as follows: “I may, perhaps, be here permitted to say that, after having carefully weighed, to the best of my ability, the various arguments which have been advanced against the principle of sexual selection, I remain firmly convinced of its truth.”
CHAPTER XXIII
Web making spiders—Dangerous wooings—An unkind lady-love—Lizard-eating spiders—Enlightened curiosity—Rival entomologists—Instinct of resignation—A worm-eating spider—Alternative explanation—The dangers of patriotism—Trap-door spiders—Web-flying spiders—Spiders that nearly fly—Spider navigators—The raft and the diving-bell.
NONE of the spiders mentioned in the last chapter are web-makers. These latter are not dancers; that is to say, the males do not dance before the females when they wish to recommend themselves as husbands. Instead, they pull at the strands of the web, whilst stationed at its circumference, in a manner which has a distinct meaning for the female, who sits in the centre, and who replies by other twitches. These may be either of an encouraging or repellent nature, and it is only in the former case that the lover ventures to approach. This, however, he must do with extreme caution, and prepared at any moment to drop and hang suspended by a thread should the object of his attentions, who greatly exceeds him in size, change her mind or conceive some cause of displeasure against him. Should he not be sufficiently quick on such occasions, he is liable to be spun up between the long legs of his lady-love as though he were a fly, and disposed of accordingly. This was observed in 1798 by Raymond Maria de Termayer, who remarks upon it: “Perhaps overpowering hunger compelled her to do it, but the act was very ferocious.”
The most curious thing in these webepathic courtships, as one may call them, is that the female spider seems to know the particular jerk or twitch of any strand of the web which is made by a male, and to distinguish it, perfectly, from the vibrations set in motion by a fly or other insect that enters it, for upon these occasions, though her back may be turned towards her admirer, she does not trouble to look round, whereas in the latter case she would not only do so, but come rushing down to secure her victim—if she were hungry, perhaps it should be added. On the other hand, as has been already mentioned, the male can interpret the wishes of the female from the movement she imparts to the thread, and regulates his conduct accordingly. Webepathy, therefore, does not seem a name ill-chosen to describe this system of intercommunication of ideas.
The spider mentioned above as devouring her lover was the common garden or geometric one, as it is sometimes called, which in England is the largest example of a web-spinner. In other parts of the world, however, web-spinning spiders attain to a much larger size, and their webs, of course, are in proportion. The largest, perhaps, are found in Madagascar, and the gigantic fabrics which many of these weave are curiously utilised by smaller spiders of a parasitic disposition, who spin their own little webs between the thick strands of those of their hosts. Here they live in perfect amity with the latter, in whose presence they find a protection against the attacks of small birds—for these, it would seem, stand in awe of these huge spiders, in whose toils they are sometimes accidentally caught, and by whom they are then devoured. So, at least, Vinson, the historian of the spiders of Madagascar, would seem to imply, if he does not actually make the statement, of which I will not be quite sure.[[136]] That the great Mygale of South America eats birds is now an established fact, Bates having given an account of it in his well-known work, The Naturalist on the River Amazon.[[137]] In this case also the birds—for there were two of them—were caught in a web, but it was not a geometric one, in which the spider sat, but a much denser and more closely woven fabric stretched across a crevice, or irregularity, in the trunk of a tree, the spider—which was of much larger size than the largest Epeira—keeping watch behind it in the recess.