Besides these particular aphides, which leave the nest directly after leaving the egg, there are four or five other species which live in it altogether, and feed on the roots of various growing plants. Some nests which I had contained a few, but under natural conditions they are to be found, I believe, in abundance. Special chambers, it would seem, are given up to them, and in Kirby’s Marvels of Ant Life there is a picture of such a “subterranean cow-house.” The question arises, where do these aphides lay their eggs, and, if in the nest, does not it largely discount the intelligence, or prudence, attributed to Lasius flavus in bringing the other ones into it? In that case, since the eggs of the various species probably resemble one another, any found outside would be brought in by the ants, just as their own larvæ or pupæ would be—or anything else which they value—nor need we ascribe greater foresight to the one act than to the other.
Ants, however, do more wonderful things in relation to aphides than this that Sir John Lubbock has recorded, and if that act is unexampled, as an exhibition of prudence, elsewhere in the animal kingdom, it is not, I think, in this particular branch of it. First it must be remarked that amongst the aphides we have what is called the “alternation of generations,” that is to say a light-loving generation that feeds on the stems and leaves of upper earth, produces one that loves darkness, whose food is only the underground roots of the plants their parents lived on. This brood in its turn gives birth to another, which forthwith seeks the sun, and so the round goes on. There is this difference in the two broods, that the light-lovers, nevertheless, seek out darkness when the time comes to lay their eggs, whilst the children of darkness lay theirs in the caves where they have, all their lives, lived. That ants should be aware of all this, and habitually adapt their cow-keeping economy to circumstances so recondite, seems very extraordinary, but it would certainly appear to be the case. Thus when Lasius fuliginosus (another Franco-Britannico, etc., species) sees Schizoneura venusta—its particular Aphis—seated on a grass stem, and evidently wishing to lay her eggs, it knows at once what to do. Soft and large, with voluminous wings, such an insect is not well fitted for burrowing. She could hardly do it, in fact, so the ants, recognising this, begin to do it for her, and soon drive a tunnel leading down to the roots of the grass, through which they lead her, first, however, having clipped off her wings, which are now but a useless encumbrance.
Arrived at the terminus, the ants make a proper apartment for their cow Aphis, and here, in the midst of warm sympathisers, and with every comfort and luxury about her, she no longer hesitates to lay her eggs. In due time they hatch, producing wingless aphides, and from the brood thus raised the ants obtain their honey. When, however, this crawling generation have in turn produced another winged one, the ants, far from seeking to detain these in a place where they would only die, again set to work to make tunnels, through which they conduct them successively to the upper air. One tunnel, one would think, would be sufficient for the purpose; but Lichtenstein, who observed these facts in the south of France,[[50]] states that each Aphis, as it issues from the egg, has a separate one made for it by the ants. Having reached the surface, these cave-born Ariels spread their wings and fly away. Where they will settle no ant knows, but to the community that has freed them they are lost, probably—they and their eggs—for ever. Do the ants know this? If they do, they do not repine at it, for they know also that the perpetuation of the species, through which alone they can hope for fresh honey, has been provided for. This seems to me altogether to outdo the prudential feat of Lasius flavus, and since Lasius fuliginosus is distributed probably throughout the greater part of Europe, all the nations that do honour to that portion of the earth’s surface are at equal liberty to think of it with patriotic complacency as “our ant.” For my part, I will only say this, that, whether it is or not, I think it deserves to be a Japanese ant—or that the Japanese, nowadays, much more deserve to have it than we do: that perhaps is the better way of putting it.
CHAPTER XIII
Cow caterpillars—The adventures of Theophrastus—Cave-born Ariels—Led to the sky—A strange attraction—Ant slaves and slave-holders—Slave-making raids—Feeble masters—An ant mystery—Effects of slavery—The decadent’s reply.
AS we have seen, both in this chapter and a former one, aphides are not the only insects which yield the ants honey—or something honey-sweet—and are cherished by them in consequence. There are, for instance, the coccidæ, or scale insects, as mentioned by Belt; but whilst some of this family are milked in the same way as the aphides, to which, indeed, they bear a strong resemblance, others are simply eaten, as though they were sweets. To them might be said in warning, “Make yourself all honey, and the ants will swallow you,” but who can modify the nature of his own juices? Then there are the ants’-nest beetles, many of which have a sweet downiness which the ants enjoy licking, and are for this reason carried about with them when they move from one place to another. Not that they are always carried, for one little beetle, at any rate, whose name—it must be a diminutive—is Formicoxenus nitidulus, is accustomed to ride on the backs of its protectors, like the little cockroaches discovered by Professor Wheeler.
But perhaps the most interesting parallel to the aphides, as cows, is to be found in certain caterpillars, which are as soft and defenceless as they are, and represent a class of creatures which ants habitually prey upon. A certain family of butterflies, however, commonly known as the Blues, but entitled to the scholarly name of Lycænidæ, produce caterpillars which bear, upon the twelfth segment of the body, a certain honey-holding reservoir which, when full or nearly so, may be made to yield its contents through the same treatment which is so effectual in the case of the aphides. The ants tap or titillate the body of the caterpillar, near where the gland is situated, with their antennæ, and the caterpillars, charmed with such affability, overflow in return. This interesting fact has been observed in various parts of the Old World, and also in North America; but the most detailed account which we have of it comes from India. In this case, as in all the others, the caterpillar is a quite small one, and feeds on the leaves of a certain tree, bearing both “an astringent yellow fruit” and the name of Zizyphus jujuba, though, by the way, jujubes are not, as a rule, astringent. The name of this little caterpillar—it would scorn to be behind the tree it feeds on in such a matter—is Tarucus theophrastus, so now we have something to fix it in the memory. The ant that patronises it is a large black one—its name I cannot give—and here, too, as in the case of the aphidean relations, we have, in the most noteworthy of the actions recorded, a very remarkable instance of what looks like foresight, and foresight, too, of a very large and general kind. In the first place, the ants make a nest at the foot of the trees in which the caterpillars reside, and here, during the period of their growth and nourishment, they avail themselves of their services. But when this period is over, and the caterpillars are about to change into chrysalids, then a strange scene takes place. All over the tree, ants are now to be seen running about in a state of the greatest excitement, and whenever they meet a caterpillar descending, or preparing to descend, the trunk, in order to burrow into the earth at its base, and there pass its pupal stage of existence, they conduct it down themselves and relieve it from the labour of digging, just in the same way as our English ants do with the aphides.
Still stranger is the scene which reveals itself if the earth at the base of the tree be removed, for then it is seen that chrysalids, and caterpillars that are about to turn into chrysalids, are clinging all round the trunk, whilst all amongst them are the ants, helping to place this one or that one in position. The band thus formed round the tree may be several inches broad, and it is always remarkably even, as though arranged on æsthetic principles. As the light shines in, the ants become agitated, and seizing hold of their property—for in this light they consider the caterpillars—begin to rebury them, so that in time, if the annoyance continues, they will form a fresh circle of bodies lower down the tree. Here, then, is an ants’ nest, described as temporary by Mrs. Wyllie, from whose interesting account[[51]] the above facts are taken, full of butterfly chrysalids, and in about a week it becomes full of butterflies themselves, and amidst the rough, black bodies of hosts of earth-working Calibans, colours born of the rainbow gleam and flash from the fairy wings of delicate insect Ariels. Each one of these was helped from its cradle, thus strangely situated, by a little group of these gnomes, who then assisted it to unfold its wings, and guided its uncertain steps. Later, when strength has come to it, and something—it knows not what—like an upward desire, these same gnomes will lead it to the portals of their gloomy Hades, where it will spread its wings and fly to meet the light. In so strange a way, led by such uncouth guides, does Ariel find the sky. Yet, as though the place of their new birth—gloomy though it be and opposed to their light-loving natures—had yet some nameless attraction for them, crowds of these butterflies may be seen, for some time after their exodus, hovering over the nest, before they leave it for ever to dwell in the courts of the sun.