Just as in the case of the aphides released by Lasius fuliginosus, these ants will never see their butterflies again, nor will they gain any after advantage that can with certainty be traced to the particular individuals thus set free. But they gain in such a manner as, if the reflection really occurred to them, would make ants not much below men. The process of reasoning would be this: “Though we may very likely not get any caterpillars from the eggs which these butterflies will lay, yet we ought not to kill them, because then there would be so many butterflies less in the world, to lay eggs, and if we did this every year, and other ants too, caterpillars, as well as butterflies, would become scarce, and at last we should not get enough.” For myself I doubt if ants really do reason like this, but by what steps this habit of releasing butterflies so as to ensure the perpetuation of the species has come about, I don’t quite see. In the case of the aphides, perhaps it has been through actual observation of their habits, and here, too, this hypothesis may not be excluded, since the butterflies might well be seen laying their eggs, nor is it unlikely that these are watched, and the issuing caterpillars tended from the beginning. For the purposes of the ants, indeed, all aphides, and every theophrastus, would be the same, and they might very well think that those which they found laying, or about to lay their eggs, were the very ones previously liberated by them from the nest. Thus the difficulty involved in supposing that they must reason in a general and not merely in a particular way does not really exist.
Some of these black caterpillar-tending ants of India are not always so lucky as to secure stock. They may live far from a jujube tree, and so never meet the right species; but if ever they do, even though it be in the most unexpected manner, they are not taken by surprise, notwithstanding that other caterpillars are habitually devoured by them. Mrs. Wyllie proved this by an experiment. “I took Theophrastus,” she tells us, “from a tree, and introduced him on the pathway of another company of the same species of ant, which lived in our verandah, but kept no farm, and it was odd to see the ants come tumbling out headlong to fight the intruder, and the sudden way in which they cooled down on investigation of the foe. None attempted to harm him, and he was politely escorted across the boundary, the ants running alongside and feeling him all over with their antennæ. This must have been instinctive, as they could have had no former knowledge of him as a ‘milk-giver.’” Mrs. Wyllie adds that “the dead chrysalids in an ants’ nest are carefully removed and thrown away outside; the ants also distinguish between the dead and the living.”
Anyone observing or reading about ants might exclaim, on finding that they utilised the natural product of other insects and kept them in captivity in order to do so, “Where will this end? May they not, then, also keep slaves?” And in very fact, as all the world now knows, we do find what is called slavery amongst ants, though to me it hardly seems the right word, since there is perfect willingness on the part of the slave, and no power of punishment lies with the master. There is equality, moreover, since this is not a matter of the kind of things which one class of a community does and another does not do, but of the spirit in which each does them. With the ants we have the Japanese spirit—or rather the Japanese seem getting nearer to the ants—and so there is real equality. However, the first act which makes these creatures slaves—for I will use terms as I find them—is one of violent and deadly hostility, and through it they are, of set purpose, taken possession of and carried off to the nest. At that period, however, they are yet in the cradle, have yet to be born into their last and most perfect state of life. From the moment they are so born they grow up as a part, and indeed the most important part, of the body politic, and of such pleasure and consideration as obtains in ant-life they have their full share.
From the above it may be gathered that these ant-slaves are ants themselves, and this, indeed, is the case. One species of ant raids the nest of another, overpowers the able-bodied inhabitants, slays or incapacitates a certain number, and carries away with it to its own nest as many of the helpless pupæ as it is able to. For a great many years—thousands probably—these combats and carrying off of spoil had been observed, but it had always been imagined that the pupæ—or ants’ eggs, as they are commonly called—were taken as provisions, merely to be stored in the nest of the victor, and there eaten at leisure. The discovery of the real truth was an era in the study of ant-history, and it was made by a Frenchman—Pierre Huber—a man of whom Darwin says that he was a “better observer even than his celebrated father,” for Pierre was the son of François Huber, the blind man, who yet found out all about bees. I hardly see how he can have been better myself; but the son was not blind, and, of course, eyesight is an advantage in observation.
The particular species of ant concerning which this discovery was made is Formica rufescens, or Polyergus rufescens—the reader may take his choice—and Darwin, who impresses the facts of ant-slavery upon the mind better than a dozen books specially devoted to ants or insects, says of it: “This ant is absolutely dependent on its slaves, and without their aid the species would certainly become extinct in a single year. The males and fertile females do no work of any kind, and the workers, or sterile females, though most energetic and courageous in capturing slaves, do no other work. They are incapable of making their own nests or of feeding their own larvæ. When the old nest is found inconvenient, and they have to migrate, it is the slaves which determine the migration, and actually carry their masters (one might just as well call them their slaves) in their jaws. So utterly helpless are the masters, that when Huber shut up thirty of them without a slave, but with plenty of the food which they like best, and with their own larvæ and pupæ to stimulate them to work, they did nothing; they could not even feed themselves, and many perished of hunger. Huber then introduced a single slave, and she instantly set to work, fed and saved the survivors, made some cells, and tended the larvæ, and put all to rights. What can be more extraordinary than these well-ascertained facts?”[[52]] The slave-ant in this case is Formica fusca, and it is also held in bondage by another species of slave-maker, viz. Formica sanguinea—or the Blood-red Ant—as was likewise a discovery of Pierre Huber. This last species is found in the south of England, and its slave-making habits have been observed by Darwin, who opened fourteen nests and found a few slaves in all of them. “The slaves,” he tells us, “are black, and not above half the size of their red masters, so that the contrast in their appearance is great.”[[52]] The black ants were not often seen by Darwin to leave the nest, and others who have observed their habits in England have considered them as “strictly household slaves.”[[52]] Huber, however, whose observations were carried on in Switzerland, says that “their chief office is to search for aphides,”[[52]] and this would take them far afield. In Switzerland, however, slaves seem to be more numerous in the nests of the Blood-red Ant, and Darwin attributes the difference in their habits to this account. Huber also tells us that the Swiss slaves “habitually work with their masters in making the nest, and they alone open and close the doors in the morning and evening.”[[52]] This is done, I suppose, by placing pellets of earth in the mouth of the entrance-tunnel and removing them again; but there is one species of ant which would have only to place or remove itself, for this purpose, since its large head, by being wedged into the passage, stops it up, and thus fulfils the office of a front door. The ant that does this must be one belonging to a certain caste of workers having very large heads, for the heads of the other ones would not be large enough. The nest of this species is made in decaying wood, and there is always some worker who thus uses his large head as a stopper, removing it when a fellow-townsman wishes to enter the nest, but presenting its smooth, impenetrable surface, guarded with jaws, to all unauthorised intruders. It is Forel, one of the best ant-observers of to-day, who tells us this, and the ant apparently is Lasius fuliginosus, which is a British species, and, according to an account which I have already referred to, does not seem to be always a wood-borer. Formica sanguinea, however, does things—or has things done for it—after a more ordinary fashion.
Darwin was the witness of a slave-raid on the part of F. sanguinea which was not, in this instance, very successful. He says: “They approached, and were vigorously repulsed by an independent community of the slave-species (F. fusca), sometimes as many as three of these ants clinging to the legs of the slave-making sanguinea. The latter ruthlessly killed their small opponents, and carried their dead bodies as food to their nest, twenty-nine yards distant; but they were prevented from getting any pupæ to rear as slaves. I then dug up a small parcel of the pupæ of Formica fusca from another nest, and put them down on a bare spot near the place of combat; they were eagerly seized and carried off by the tyrants, who perhaps fancied that, after all, they had been victorious in their late combat.”[[52]] In his work, Ants and their Ways,[[53]] the Rev. Farren White describes a similar raid which was—or rather which had been, for it was nearly over when he arrived on the scene—wholly successful. Here, however, the oppressed species seems to have made a very poor resistance, though very likely it had been more vigorous in the earlier stages of the raid. “I watched a fusca,” says Mr. White, “carrying off a pupa from behind the entrance whence the sanguineæ were issuing forth. Immediately it saw one of the enemy approaching, it dropped its charge and left it to its fate. The sanguinea then gave it a push, and drove it off in double-quick time”; and, again, “I noticed a sanguinea coming up out of the nest with a pupa, and a fusca, observing it, went up a fern-frond with the utmost expedition.”[[53]] Other observations of a similar nature were made, and the conclusion arrived at by Mr. White is “that between the fuscæ and the sanguineæ there is a well-defined and clearly pronounced antagonism. In presence of the sanguineæ the fuscæ were terror-stricken. In fact the depredators had it all their own way, and were able in this instance, at least, to carry out their marvellous instincts without destroying a single life.”[[53]] It will be seen how ill this accords with the account given by Darwin. My own way of accounting for the discrepancy is that, in the first instance, the little fuscæ were flushed with success, and, in the second, demoralised through defeat. The same effects would follow the same causes in all but the most splendid human armies.
The raids made by the first-mentioned species, Polyergus rufescens, or, as Huber calls them, the Amazon ants, are of an even more determined description, for none are braver, or perhaps so brave. If one of these should find herself alone and in the midst of enemies, she makes no effort to escape, as many, though not all, other species would, but fights on to the end, making constant agile leaps to this side or that, at every one of which she transfixes an enemy, and dies at last biting hard. To fight, indeed, is the whole end, aim, and business of life for an Amazon, and we have already seen how they do no work, and are washed, fed, and carried by their servants. It is not quite true, however, that they cannot feed themselves, as Pierre Huber thought, and had good reason to think, for a well-known living observer—Herr Wasmann—has discovered that their mandibles are so constructed as to enable them “to absorb nourishment from eggs or pupæ.” Possibly the mandibles are hollow, and communicate thus with the mouth, as is the case with some other insects, but I have not Wasmann’s account at hand, and his exponent says only this. Wasmann tells us also that these Amazons will “absorb nourishment,” however they do it, even from the eggs of their own species. They cannot, however, feed on liquid food, and as they had no other when shut up without servants, that is why they died, or would have died, had these not been brought them in time. So too, though their slaves wash and brush them, yet they are always brushing themselves and attending generally to their own toilette, and this they do even amidst
“All the currents of a heady fight,”
so that Wasmann has compared them to the Spartans combing their long hair before the battle of Thermopylæ, though we are not told that they combed it after the fight had begun.
Still, it seems plain that the habit of keeping slaves has exercised a degrading influence on these ants, and this tendency is much more markedly apparent in several other species. One of these with a really dreadful name, Strongylognathus—we might call them Strong Ants, but they seem to be weak ones—is described by Forel as “une triste caricature” of the Amazons, and the extraordinary thing is that, though themselves feeble and enervated, they manage to make, or by some means obtain as slaves, the workers of a much more robust species—Tetramorium, to wit; workers, by the way, are the only class of ants ever enslaved. These weak ants fight in the same way as the Amazons themselves; but, though spirited enough, they are so much inferior in bodily vigour to the Tetramoriums, “a courageous species living in large communities, that in a battle between the two, artificially instigated by Forel, almost all the slave-holders were killed, without being able to avenge their deaths even on a single one of those whom they aspired to rule.” Yet they won the day, or rather the already enslaved Tetramoriums, who marched to do battle for them, won it for the few survivors in their ranks. From this we can see how, when these decadents once have slaves, they may get more. The difficulty is how they are obtained in the first instance—when a nest is first founded by a queen of the slave-making species, for example. It might be supposed, finding two kinds of ants living together, one weaker and much more helpless than the other, that the former lived a parasitic existence in the nest of the latter, and was not a slave-owner at all; but this theory is disproved by the fact that no males or females of the Tetramoriums are ever to be found, showing that it is not they but the others who are the true founders of the nest.