THE INTELLIGENCE OF ANTS

By Sir John Lubbock

The subject of ants is a wide one, for there are at least a thousand species of ants, no two of which have the same habits. In this country (England) we have rather more than thirty, most of which I have kept in confinement. Their life is comparatively long: I have had working ants which were seven years old, and a queen ant lived in one of my nests for fifteen years. The community consists, in addition to the young, of males, which do no work, of wingless workers, and one or more queen mothers, who have at first wings, which, however, after one marriage flight, they throw off, as they never leave the nest again, and in it wings would of course be useless. The workers do not, except occasionally, lay eggs, but carry on all the affairs of the community. Some of them, and especially the younger ones, remain in the nest, excavate chambers and tunnels, and tend the young, which are sorted up according to age, so that my nests often had the appearance of a school, with the children arranged in classes. In our English ants the workers in each species are all similar except in size, but among foreign species there are some in which there are two or even more classes of workers, differing greatly not only in size, but also in form. The differences are not the result of age nor of race, but are adaptations to different functions, the nature of which, however, is not yet well understood. Among the Termites, those of one class certainly seem to act as soldiers, and among the true ants also some have comparatively immense heads and powerful jaws. It is doubtful, however, whether they form a real army. Bates observed that on a foraging expedition the large-headed individuals did not walk in the regular ranks, nor on the return did they carry any of the booty, but marched along at the side, and at tolerably regular intervals, "like subaltern officers in a marching regiment."

Solomon was, so far as we yet know, quite correct in describing ants as having "neither guide, overseer, nor ruler." The so-called queens are really mothers. Nevertheless it is true, and it is curious, that the working ants and bees always turn their heads towards the queen. It seems as if the sight of her gives them pleasure. On one occasion, while moving some ants from one nest into another for exhibition at the Royal Institution, I unfortunately crushed the queen and killed her. The others, however, did not desert her, or draw her out as they do dead workers, but on the contrary carried her into the new nest, and subsequently into a larger one with which I supplied them, congregating round her for weeks just as if she had been alive. One could hardly help fancying that they were mourning her loss, or hoping anxiously for her recovery.

The communities of ants are sometimes very large, numbering even up to 500,000 individuals; and it is a lesson to us, that no one has ever yet seen a quarrel between any two ants belonging to the same community. On the other hand, it must be admitted that they are in hostility, not only with most other insects, including ants of different species, but even with those of the same species if belonging to different communities. I have over and over again introduced ants from one of my nests into another nest of the same species, and they were invariably attacked, seized by a leg or an antenna, and dragged out.

It is evident therefore that the ants of each community all recognize one another, which is very remarkable. But more than this, I several times divided a nest into two halves, and found that even after a separation of a year and nine months they recognized one another, and were perfectly friendly; while they at once attacked ants from a different nest, although of the same species.

It has been suggested that the ants of each nest have some sign or password by which they recognize one another. To test this I made some insensible. First I tried chloroform, but this was fatal to them; and as therefore they were practically dead, I did not consider the test satisfactory. I decided therefore to intoxicate them. This was less easy than I had expected. None of my ants would voluntarily degrade themselves by getting drunk. However, I got over the difficulty by putting them into whisky for a few moments. I took fifty specimens, twenty-five from one nest and twenty-five from another, made them dead drunk, marked each with a spot of paint, and put them on a table close to where the other ants from one of the nests were feeding. The table was surrounded as usual with a moat of water to prevent them from straying. The ants which were feeding soon noticed those which I had made drunk. They seemed quite astonished to find their comrades in such disgraceful condition, and as much at a loss to know what to do with their drunkards as we are. After a while, however, to cut my story short, they carried them all away: the strangers they took to edge of the moat and dropped into the water, while they bore their friends home into the nest, where by degrees they slept off the effects of the spirit. Thus it is evident that they know their friends even when incapable of giving any sign or password.

This little experiment also shows that they help comrades in distress. If a wolf or a rook be ill or injured, we are told that it is driven away or even killed by its comrades. Not so with ants. For instance, in one of my nests an unfortunate ant, in emerging from the chrysalis skin, injured her legs so much that she lay on her back quite helpless. For three months, however, she was carefully fed and tended by the other ants. In another case an ant in the same manner had injured her antennae. I watched her also carefully to see what would happen. For some days she did not leave the nest. At last one day she ventured outside, and after a while met a stranger ant of the same species, but belonging to another nest, by whom she was at once attacked. I tried to separate them, but whether by her enemy, or perhaps by my well-meant but clumsy kindness, she was evidently much hurt and lay helplessly on her side. Several others passed her without taking any notice, but soon one came up, examined her carefully with her antennae, and carried her off tenderly to the nest. No one, I think, who saw it could have denied to that ant one attribute of humanity, the quality of kindness.

The existence of such communities as those of ants or bees implies, no doubt, some power of communication, but the amount is still a matter of doubt. It is well known that if one bee or ant discovers a store of food, others soon find their way to it. This, however, does not prove much. It makes all the difference whether they are brought or sent. If they merely accompany on her return a companion who has brought a store of food, it does not imply much. To test this, therefore, I made several experiments. For instance, one cold day my ants were almost all in their nests. One only was out hunting and about six feet from home. I took a dead bluebottle fly, pinned it on to a piece of cork, and put it down just in front of her. She at once tried to carry off the fly, but to her surprise found it immovable. She tugged and tugged, first one way and then another for about twenty minutes, and then went straight off to the nest. During that time not a single ant had come out; in fact she was the only ant of that nest out at the time. She went straight in, but in a few seconds—less than half a minute—came out again with no less than twelve friends, who trooped off with her, and eventually tore up the dead fly, carrying it off in triumph.

Now the first ant took nothing home with her; she must therefore somehow have made her friends understand that she had found some food, and wanted them to come and help her to secure it. In all such cases, however, so far as my experience goes, the ants brought their friends, and some of my experiments indicated that they are unable to send them.

Certain species of ants, again, make slaves of others, as Huber first observed. If a colony of the slave-making ants is changing the nest, a matter which is left to the discretion of the slaves, the latter carry their mistresses to their new home. Again, if I uncovered one of my nests of the Fuscous ant (Formica fusca), they all began running about in search of some place of refuge. If now I covered over one small part of the nest, after a while some ant discovered it. In such a case, however, the brave little insect never remained there, she came out in search of her friends, and the first one she met she took up in her jaws, threw over her shoulder (their way of carrying friends), and took into the covered part; then both came out again, found two more friends and brought them in, the same manoeuvre being repeated until the whole community was in a place of safety. This I think says much for their public spirit, but it seems to prove that, in F. fusca at least, the powers of communication are but limited.

One kind of slave-making ant has become so completely dependent on their slaves that even if provided with food they will die of hunger, unless there is a slave to put it into their mouths, I found, however, that they would thrive very well if supplied with a slave for an hour or so once a week to clean and feed them.

But in many cases the community does not consist of ants only. They have domestic animals, and indeed it is not going too far to say that they have domesticated more animals than we have. Of these the most important are Aphides on trees and bushes; others collect root-feeding Aphides into their nests. They serve as cows to the ants, which feed on the honey-dew secreted by the Aphides. Not only, moreover, do the ants protect the Aphides themselves, but collect their eggs in autumn, and tend them carefully through the winter, ready for the next spring. Many other insects are also domesticated by ants, and some of them, from living constantly underground, have completely lost their eyes and become quite blind.

When we see a community of ants working together in perfect harmony, it is impossible not to ask ourselves how far they are mere exquisite automatons; how far they are conscious beings. When we watch an ant-hill tenanted by thousands of industrious inhabitants, excavating chambers, forming tunnels, making roads, guarding their home, gathering food, feeding the young, tending their domestic animals—each one fulfilling its duties industriously, and without confusion—it is difficult; altogether to deny to them the gift of reason; and all our recent observations tend to confirm the opinion that their mental powers differ from those of men, not so much in kind as in degree.