The Industries of Animals

by Frédéric Houssay

Domestic animals of Ants. — Following through different species the perfection reached in the art of laying up provisions for the future, we have gradually arrived at methods resembling those of Man. But a foresight still greater and nearer to his is manifested by those ants who breed and keep near them animals of different species, not for the sake of their flesh, but for certain secretions, just as man utilises the milk of the cow or the goat. Ants have true domestic animals belonging to a variety of species, but the most widely spread are the Claviger and the Aphides or plant-lice. To keep these insects at their disposal, Hymenoptera act in various ways: some, who are a little experienced, are content to take advantage of a free aphis which chance may put in their way; others shut up their cattle in stables situated in the midst of the ant-hill, or else pen them in the country at a spot where they can best find their food. These facts have long since been carefully studied and leave no room for doubt.

The Claviger testaceus is a small beetle, often met in the dwellings of ants. Nature has not been very generous on its behalf. It is blind, and its eyes are indeed altogether atrophied. The elytra are soldered at the median edge, so that it cannot spread its wings to fly. It is an animal predestined to the yoke; and for the rest its masters treat it with extreme kindness. The yellow ants, according to Müller,[64] have reduced this outcast beetle to domesticity, and it is almost a piece of good fortune for him to have lost his freedom and to have gained in exchange a shelter and a well-furnished trough. These insects are in fact cared for by their masters, who feed them by disgorging into their mouths the sweet liquids they have gathered here and there. If a nest is disturbed the ants hasten to carry their eggs and larvæ out of danger; they display the same solicitude with regard to the Claviger, and carefully bear them to the depth of their galleries. It must not be believed that the practical insect takes so much care in order to repair the injustice of nature towards the beetle; the part of a devoted sick nurse would not suit him; he cares for the Claviger because it is his property, a capital which brings in interest in the shape of excellent sweet little drops which are good to suck.[65]

A yellow ant, who wishes to enjoy the result of the cares given to his pensioner, approaches it and gently caresses it with his antennæ; the other shows signs of pleasure at this visit, and soon a pearly drop appears on the tuft of hairs at the edge of its elytra, and this the ant hastens to lick. The beetle is thus exploited and tickled by all the members of the community to which he belongs who meet him on their road. But when it has been milked two or three times it ceases to secrete. A solicitous ant arriving at this moment finds its efforts in vain, but still behaves like a good shepherd; it shows no impatience or anger towards its exhausted beast, knowing well that it is only necessary to come back a little later or to go to another member of the herd. Nor are his cares lessened by finding the source dried up. He foresees that it will still be good after repose, and if it is hungry he disgorges food for it.

Degrees of civilisation in the same species of Ants. — These facts are sufficiently marvellous in themselves, but are more surprising when we recollect that they cannot be regarded as an innate and unreflecting instinct with which all the individuals of the same species are endowed. The art of domesticating the Claviger is a stage of civilisation reached by some tribes and not by others. Lespès[66] has placed this out of doubt in the following manner. He had specimens of Lasius niger who exploited a flock of Coleoptera. Having met ants of the same species who possessed no flocks, he brought them some. At the sight of the little insects they threw themselves on them, killed them, and devoured them. If we compare these facts with those which pass in human societies, it will seem to us that these latter Hymenoptera behave like a horde of hunters in the presence of a flock of sheep, while the first have already arrived at the sheep-herding stage.

Aphis-pens and paddocks. — Ants can also keep Aphides in their homes. In this case, fearing that the adult beasts may not be able to adopt a change of surroundings and food, they bring the eggs to their nests and care for them at the same time as their own children. In time they come out and constitute a flock easy to tame. Other ants, still more intelligent, have discovered a method of holding the Aphides captive, while allowing them to enjoy their accustomed life, and to feed at will on the foods they prefer on their own favourite spots. It is sufficient for this purpose to establish barriers around a group of cattle who have themselves fixed the place of their sojourn. The Lasius niger, a skilful architect, constructs vaulted passages from his dwelling into the country. These covered roads, built with earth moistened with saliva, have various ends; some have been made in order to reach remote work sheltered from the sun, or to give concealment from enemies. Many lead to the pens of the Aphides; they reach from the anthill as far as the foot of a plant where these insects are abundant. In order to have their milkers at their disposal, without removing them from pasture, the ants make tunnels along the stalk, and enclose within it all the Aphides they meet. They thus prevent any desire for a distant ramble. But in order that the flock may not be too closely confined, the Lasius niger enlarge the galleries in places, and make a sort of chamber or stable in which the beasts may disport themselves at ease. These halls, which are proportionately very vast, are supported against the branches and leaves of the plant which bears up the walls and the vaults. The captives find themselves then with all the advantages of material life, and may be milked with every facility.[67]

An allied species of ant, the Lasius brunneus, lives almost entirely on the sweet secretion of large Aphides in the bark of oaks and walnut trees. The ants construct around these insects cabins made of fragments of wood, and wall them in completely so as to keep them at their own disposal.

The Myrmica also forms similar pasture lands; its system is rather less perfect than that of the Lasius, as it does not form covered galleries to reach its stables. It is content to build large earth huts around a colony. A large hole, which allows the passage of the ants, but not the escape of the flock, is formed so that they may come to milk their cows. They use the same methods we have seen practised on the Claviger, caressing the insect with their antennæ until the sugared drop appears.[68]

An example is quoted which shows still greater intelligence and foresight in Ants. They have been known to repopulate their territories after an epidemic, or at least after the destruction of their Aphides. The proprietor of a tree, finding it covered with these exploited beasts, cleared it of its inconvenient guests by repeated washes; but the dispossessed Hymenoptera, considering that this pasture close to their nest was very convenient for a flock, resolved to repopulate it, and for some time these tenacious insects could be seen bringing back among the foliage Aphides captured elsewhere.[69]

Slavery among Ants. — The custom of making slaves is widely spread in the ant world; I have already described the expeditions organised to obtain them. We will now consider the relations of these insects among themselves.

The Formica sanguinea takes possession of the eggs of the Formica fusca and rears them with its own. When the slaves reach the adult condition they live beside their masters and share their labours, for the latter work, are skilful in all tasks, and can by their own activity construct an ant-hill and keep it going. If they desire servants, it is not in order to throw all the work on them, but to have intelligent assistants. This is the primitive form of slavery as it first existed among men. It was not until later that it became modified, to become at last an institution against which the sentiment of justice arose. Other species of Ants have pushed the exploitation of slaves to a point Man has never reached. But the Formica sanguinea are companions to their helpers rather than masters, and even show them great consideration. When the colony emigrates one may see the owners of the nest, who are of larger size than the Formica fusca, take these up in their jaws and carry them the entire way.