Here, then, we have an aggressive, as well as a protective, resemblance—for, no doubt, the two are combined—of which principle we have another example in a certain mantis of India, which resembles, in a manner equally deceptive, if not quite so perfect, a more attractive object, namely, a flower. Most of us have seen pictures of the ordinary green praying mantis, a curious kind of insect, allied to the grasshoppers, that has received its name owing to its habit of sitting motionless with the fore part of its body raised, and its fore legs extended, as though it were praying. Really, however, it is waiting for its prey, which, when it approaches, it cuts to pieces by pressing together, as though it were shutting a knife, the flattened and blade-like joints of the legs it has held out so holily; first, of course, having got the victim between them. The mantis in question does not look quite like the praying one. Instead of rearing itself upright, it sits flat on the leaf, and its body is not green, but pink. Being rounded, it passes for the centre of a flower, whilst the legs, which diverge from it at different angles, and are flattened in the most extraordinary manner, bear a still more striking resemblance to the petals. Sitting thus, a flower amongst flowers, it is approached by many insects which, too late, discover the real nature of that somewhat strange-looking blossom.
Here, then, we have a flower-insect. Stick-insects—walking-stick insects as we call them—or grass-insects, are more common. They are especially abundant in Central Africa. Anyone who sees one of these creatures for the first time is infallibly taken in by them, though he may have read about them often, and made up his mind not to be. He is strengthening himself, perhaps, in this resolution, at the moment when, having at last got to the country where they abound, he happens to be brushing away, with his hand, a small wisp of hay or dry grass that he sees clinging to his coat. But that wisp of hay is the very insect he has set himself to recognise, but which now, even when his native servants point it out to him and tell him what it is, he cannot for the life of him make out to be anything but what it looks like. It is just a slight stem of yellow, withered grass, from which six still slighter pieces hang, at intervals, in pairs. Bend the stem as you will, and twist the bits that hang from it how you like, they all stay just as you put them, as long as they have anything to rest against. But if you take the thing, at any point, between your thumb and finger, and hold it in the air, then the other parts of it will either remain stiff or dangle down, just as you would expect them to do, if it were a piece of grass that you held. The insect seems jointed everywhere, so that, what with this, and the thinness and ridiculous length of its body and all its legs, it does not even look like a healthy growing grass, but only a long, thin bit that has first been broken off, then broken again, in all sorts of places, and, finally, crushed up, squeezed and crumpled together in the hand. Yet the insect which it really is, has a head, eyes, antennæ, thorax, abdomen, and all the internal organs like any other one, and it breathes, sleeps, eats, and digests upon just the same principles. There are thousands of these wonderful grass-insects, and almost as many different species of them. All about, wherever the grass springs up in patches, amidst the forests of equatorial Africa, they form, as it were, a sort of second animal crop, living amongst the vegetable one and indistinguishable from it. When they leap from one stem to another, then, all at once, they are seen; but the instant they alight they become invisible again, vanishing under one’s very eyes, whilst one looks at them, as if by magic. What is most wonderful is that as the tintings of the true grasses change with the season, so do those of the false ones that cling to them. From the bright, vivid green of the fresh spring crops, through the later darker greens, and the golds and reds of autumn, all is mimicked, the one change keeps pace with the other, but whether it is a sequence of different imitative creatures—like the rotation of crops—or whether it is not the species, but only their colours, which change, does not appear to be certain, though, probably, it is the latter.
Other insects imitate mosses or lichens, whilst a still greater number, perhaps, are the counterparts of all kinds of leaves—from the fresh young green ones to those which are sere and yellow. To these belong the mantises which we have just been talking about, besides a whole host of locusts and grasshoppers. One of these latter was seen by Mr. Belt, in Nicaragua, standing perfectly still in the midst of an army of foraging ants, numbers of which kept passing over its body, and would at once have torn it to pieces, had they had the smallest idea that it was not what it pretended to be. This locust had wings, like others of its family, and could easily, by their aid, have got away from the ants. This, however, would not have saved its life, for the air and surrounding trees were full of birds that were busily engaged in catching such insects as the ants put up. Knowing, therefore, that it would only be flying from danger to certain death, it preferred, or, rather, its instinct taught it, to stay and brave the former, which it might do with a very fair chance, though not quite a certainty, of success. That there was no choice in the matter we may, I think, assume, because with all these creatures that imitate still life, there is a strong instinct to be still themselves whenever there is cause for alarm—and indeed generally, as long as moving can be dispensed with. This is, indeed, a part of the deception, since it is obvious to the meanest capacity of bird or predaceous insect, that a leaf, for instance, that walks about, cannot really be a leaf.
Neither can it, when it, all at once, comes off its stalk and begins to fly about, in the shape of a butterfly, which is what happens, sometimes, in India and the Malay Archipelago, as we shall immediately see. In these countries there is a butterfly that belongs to the same family as our own purple emperor, and, as far as the upper surface of its wings is concerned, it is a purple emperor, and so looks like one, when it flies. But as soon as it settles, it becomes a leaf, for then it raises its wings above its back, in the way butterflies do, so that only their under surface is seen, which is as like a dry brown leaf as anything that is not one can be. The shape is exact, from the extreme point, or tip, of the upper wing, to the little swallow tail at the end of the lower one, which last just touches the stem that the butterfly clings on, and makes the stalk of the leaf. Between the tip and the stalk there runs a well-marked dark line, which answers very well for the leaf’s mid-rib, whilst on each side of it thinner lines are traced, representing the lateral veins. The slender legs of the butterfly, as it sits on the stalk, are hardly to be seen, and its head lies just hidden between the margins of the wings. The leaves of the bush on which it has gone down are of the same shape and colour as itself, for it takes care not to settle amidst surroundings with which it would not be in harmony. A bird, therefore, that has pursued this brilliant blue butterfly into a bush, where it disappears, is completely baffled; and so, too, is a grave scientific gentleman with a butterfly-net in his hand.
The above, I believe, is the best example known of a butterfly that escapes its enemies by looking like a leaf, or any other inanimate object; but there are others where the take-in is of a still more curious and unexpected kind. Certain butterflies have bitter juices in their bodies, and for this reason are let alone by birds and other enemies. As a consequence, other butterflies belonging to quite different families, have taken to mimicking them—just as if they were leaves or sticks or grasses—so that, being mistaken for them, they are let alone too. If they were not so mistaken, they would be eaten at once—or at least whenever they could be caught—for their juices are very nice indeed. What seems still more extraordinary is that, in some cases, the nasty butterfly is mimicked only by the female of the nice one, and not by the male. Thus there is a butterfly in Africa, the male of which is a beautiful swallow-tail, but the female has no tails to her wings, and both in shape and colouring she is just like another butterfly, not nearly so handsome, and which is not a swallow-tail at all. What can be the reason of this? What can account for this favouritism in Nature?—for that is what it seems like. Why should only the nice-tasting female be protected, and not the equally nice-tasting male? But the male, it appears, can fly faster, and he is not bothered by having to lay eggs, like the female. The female, with eggs in her body, is heavier than he, and whilst she is laying them she has to sit still. This is the explanation generally given for a fact so remarkable. I confess that I don’t feel quite satisfied with it, but it is difficult to think of a better one. At any rate, there are the facts. Butterflies mimic each other, and pretend to belong to families which they really don’t belong to—just as adventurers do.
But it may be said, how can one tell which is which, or, if two butterflies look exactly alike, how can we tell that they do belong to two families, and not to one and the same? But if one dissects a leaf-, or a walking-stick-insect, one does not find that it is like a leaf, or a piece of twig, inside, and just in the same way, though the difference is not so great, the two butterflies that look so much alike, are found to differ, on dissection. The internal organs of the mimicking kind have not been changed in the same way that its colouring and shape have been—for that would have done it no good—and then, again, it is not quite exactly like the other one; there is some difference, a little more, perhaps, than that between Tweedledum and Tweedledee, which would be enough for an entomologist, when he had the two on a table, to be able to tell.
It is not only amongst insects that these curious cases of beneficial resemblance are to be found, that creatures live, as it were, a false life, and are not what they seem to be. The device, indeed, is not so frequently resorted to in the case of any other order of animals, and when it is, it is not, as a rule, so marked—not of such a definite nature as with insects, and some other of the smaller class of creatures, but still the principle is there. We have seen the case of the mantis pretending, as it were, to be a flower. There is a certain lizard that does much the same thing, for the skin at the angle of its mouth, on each side, is puckered up into a little red flower, just like one that grows in the sand, where it lives. Insects, thinking to come to the flower, come to the lizard’s mouth instead, and are soon gobbled up. Insects are things which often fly into manifest danger, but still, if they saw the lizard they would be less likely to come to the flower. But now this lizard’s body is exactly the colour of the sand that it lies in, so that it can hardly be seen, and this sort of general resemblance is much more common amongst birds and mammalia than the more special ones that we have been considering. I do not, indeed, know any case of one quadruped escaping destruction, by being mistaken for another, or for a rock or tree, but amongst birds there are just a few instances of this. In the Malay Archipelago, for instance, there are some loud, noisy birds which are called “Friar-birds,” because some of the feathers on their necks curl up over their heads, like a friar’s cape or cowl. They have powerful beaks and claws, which they know how to use, and, as they fly about in flocks, they are very well able to take care of themselves. There are different species of these friar-birds on each of the larger islands, and in each of these islands—flying in the same flock with them—is a bird of a quite different family, and as timid and retiring as the others are bold and aggressive. Orioles these attendant birds are, and the typical oriole is as different from a friar-bird in appearance as it is in disposition. But these particular ones resemble them so exactly that they have been mistaken for friar-birds by scientific gentlemen, with the two together in their hands, and have even got mixed up with them in scientific works—flying with them still, through those dry, dead leaves, as though they were the living forests of their native land. Thus in a great scientific French book, called Voyage de l’Astrolabe, an oriole of Bouru is both described and figured as a friar-bird, keeping up the joke, or the fiction, to the very last. However, as far as that is concerned, I have no doubt that the oriole thinks he really is a friar-bird, or, at least, feels as if he was one, which would come to much the same thing.
When first these cases of imitation, or mimicry as they are called, began to be noticed,[11] nobody could tell what to make of them. It seemed plain that one animal could not purposely make itself like another one—or like a twig or a flower—in the way that an actor dresses up to represent some character on the stage. But how, then, had such marvellous resemblances been brought about? Chance seemed quite out of the question, but nobody had any better explanation to give. The whole thing was a mystery. Gradually, however, the subject came to be better understood. One thing was clear: that the animal—or one of the animals—presenting this extraordinary likeness was always benefited by it. At last came Darwin, who explained everything by natural selection, the principle of which is this, that as no two individuals of any species are born quite alike, some must be born with some sort of an advantage over others, and as these would live longer, and leave a greater number of descendants to inherit this advantage—whatever it might be—all living creatures must, gradually, be getting better and better adapted for the kind of life they have to lead. Supposing, therefore, that two different creatures, living in the same country, had some slight resemblance to one another—and this would not be wonderful—then if this resemblance was an advantage to one of them, it would gradually get more and more like the other, because those individuals that were less like it would get killed off sooner, whilst the others would live longer and leave a greater number of offspring, to carry on the likeness. Those orioles, for instance—to take our last example—which least resembled the friar-birds, would get soonest killed by hawks and kites, whilst those that most resembled them would be most let alone, and so they would lay more eggs, and rear more young birds, and of these young orioles, some would be even more like the friar-birds than their parents, and so it would go on. The gradually increasing resemblance would be like a portrait that was always being painted and painted, and having finishing touches put to it, without ever being quite finished—an eternal sitter with an eternal artist in front of him; for the sitter, too, would change as time went on, and as he did, so would his portrait have to. This is how Nature, the great artist, paints her portraits, so that when, in speaking of these cases, we say that one creature mimics another we really mean something quite different. Still, mimic, we are told, though it conveys a wrong meaning, is the best word to use, because with it we can express this wrong meaning in so many different ways, having at our disposal “the convenient series of words—mimic, mimicry, mimetic, mimicker, mimicked, mimicking.” So we should not call something that is white, white, if, with more flexibility, we could describe it as black—and this, indeed, with the converse, is a principle very much in vogue. The curious thing is, however, that when the likeness is between some creature and a plant or inanimate object, scientists do not say that the former mimics the latter, but that it resembles it. They can put up with the right word then, but not, it appears, in the other case. Yet there is no essential distinction between the two, and the process by which each has been brought about, is identical. So, as one butterfly, say, does really resemble another, but does not really mimic it, why cannot learned gentlemen use the right word here too, instead of speaking a language which neither accords with the fact, nor expresses their real meaning? Even if it does come more pat to describe a thing badly, is it not, nevertheless, better to describe it well? So I say, with Hotspur—
“Oh, while you live tell truth and shame the devil.”