Chapter VIII · RESEARCHES INTO THE ORIGIN OF MIXED OR COMPOUND ANT-HILLS.

The discovery of societies composed of different species, apparently living tranquilly together, was of but trifling consideration; an object of by far higher interest was, to ascertain the real nature and intent of this association, and to decide to which of the two casts the ant-hill appertained. The most effectual method of acquiring this information, was undoubtedly that of inspecting the interior of their common abode, and of thus coming to the fact, whether there were males and females of the two species, or of one only; as a previous step, it was however necessary to institute a comparison between the allied and rival ants, the Amazons, and the peaceable Ash-coloured Ants, and the latter intermixed with those of the same species, in simple ant-hills. The comparison, I would even say the confronting, of the Ash-coloured Ants in compound, with those inhabiting simple ant-hills, daily repeated, and often with the microscope, left me no doubt of their identity.

The Rufescent Ant, denominated by M. Latreille, Fourmi roussâtre, in every point answers the description of those that fell under my own observation. This author, having made, not only a genus apart, but a distinct class of these insects, from the simple inspection of their form, had, without knowing their manners, given the best proof of the distance which separates them from the dark Ash-coloured Ants. In the notes at the end of this work, a description is given of both species; I shall here, however, briefly describe them to prevent the trouble of recurrence. The former (Fourmi roussâtre) is one-third larger than the latter (Fourmi noir-cendrée); its head is of a square form, its abdomen short and globose, terminating in an obtuse point. It carries its head close to the ground, stands high upon its legs, and moves by a succession of jerks. The latter has a triangular-shaped head, which it carries in an horizontal position; its abdomen is an elongated oval, its feet are short, and its progressive movement more equal and uniform. The Rufescent Ant is of one uniform colour, from the antennæ to the extremity of the abdomen, of a red more or less falling into yellow, and more or less passing into a brownish tint according to its age; the whole of its body is, as it were, invested with a rich glossy varnish. The dark Ash-coloured Ant is sufficiently well described in its denomination; the rings of its body vary in colour from black to grey, the rest of the body is of an unpolished black, but that part lying between the thorax and abdomen (l’etranglement) is more frequently of the same colour; now and then it presents a yellow tinge, the feet are in colour a little paler. The mandibles or pincers of the Rufescent Ant, are very slender, arched, destitute of teeth, and present no concavity; those of the Ash-coloured Ant are large, broad, hollowed like a spoon, shaped as a gouge, and furnished with teeth on the margin. The eyes of the former species are very small, black, and round; those of the latter, rather large and oval. The scale is large and rounded in the one, large and triangular in the other; the Rufescent Ant is moreover provided with a sting, of which the dark Ash-coloured Ant is destitute. We see from this description how much these species differ.

Let us now pass on to the important research of the males and females, to determine who are the original tenants of the ant-hill, the Amazons, or the Negroes, for we must look upon those born there as the first occupants. From an inspection of the interior of one of these mixed ant-hills, I came to the knowledge of the singular composition of these republics. The Negro labourers, by far the most numerous, occupied the upper story of the building; they were guarding a multitude of pupæ, which appeared to be of two different species: some resembled those of the Negro Ants (probably what the Amazons had brought thither), others exhibited the perfect mould of the Martial Ants; these were larger than the preceding, their mandibles were slender and arched, their eyes small and black; added to this, they had every character of that species. There was also under the guard of the Negro Ants, a considerable number of larvæ, belonging to different species, admitting of easy distinction, from the curvature and thickness of the body. Descending another story, I perceived the Amazons collected in numerous groups, mingled with the Negroes; but what most interested me, and fully satisfied my curiosity, was, the finding among them little males, entirely black, with glittering wings, bearing no resemblance to those I had hitherto met with. At length I observed females of a large size, of an orange colour, whose similitude to the Rufescent Ants, clearly denoted their origin. The greater part possessed wings; in their body, eyes, and teeth, they closely resembled the Warrior labourers, but were of greater size. The males were not so large as those commonly found in simple Negro dwellings, and were unlike them, in not having either the feet or antennæ yellow.

In further examining the interior of this nest, which was of great depth and extent, I remarked that the Negroes were alone occupied in watching over these males and females, who allowed themselves to be conducted from place to place, as if they looked upon them as their natural parents. The Amazons, on the other hand, took not the slightest notice of them, but retired and hid themselves as quickly as possible. On looking around, I could see no traces of destruction, nor indeed any thing to justify a suspicion that the Legionary ants were endowed with a ferocious instinct, although one would be inclined to this belief from their martial disposition.

It seems sufficiently demonstrated by what we have seen of the contents of a mixed ant-hill, that it belongs to the Amazons, and that it is composed of three sorts of individuals of that species, and of Negro labourers. With all my care, I could perceive neither males nor females of this latter cast, but only young Negro working ants, and these I recognised by their colour. But whence does this proceed? Are the larvæ and pupæ taken away from the Negro Ants by the Amazons developed in the enemy’s encampment, and do they afterwards become house-stewards, and auxiliaries to the warlike tribe with whom they are associated? Every circumstance seems to prove that here rests the great mystery of their association with the Amazons: brought up in a strange nation, not only do they live sociably with their captors, but bestow the greatest care upon their larvæ and pupæ, their males and females, and even evince the same regard for them, transporting them from one part of the ant-hill to another, going in search of provisions for them, building their habitation; forming, as occasion requires, new galleries, and fulfilling the duties of sentinels, by guarding the exterior of their common abode, not once suspecting that they live with those very insects who have expatriated them.

Whilst the Negro Ants are thus engaged, the Amazons tranquilly wait at the bottom of their subterranean abode, the hour of departure, reserving their strength, their courage, and the tactic they so well know how to put in use, for the purpose of bringing in, from some neighbouring ant-hill, hundreds of larvæ, which they confide to those in charge of the household establishment; these, in their turn, are destined to become useful to the community.

The ants, whose habitation I had deranged, had already furnished me with some traits leading to a conjecture of these truths. When the Amazons, deceived by the strange appearance of their nest, were wandering over the surface, unable to find a retreat, the Negro Ants, who were incessantly occupied in forming new galleries, and who knew better than they the new localities of the ant-hill, drew them from their embarrassment by taking them up gently in their mandibles, and conducting them to the galleries already pierced. An Amazon was frequently seen to approach a Negro, and play upon its head with its antennæ, when the latter immediately seized it in its pincers, and deposited it at one of the entrances. The Amazon Ant then unrolled itself, caressed once more its kind friend, and passed into the interior of the nest. It now and then happened that a Negro Ant, engaged in carrying an Amazon, lost all knowledge of its route, wandering here and there without finding any entrance.

I observed one, after several ineffectual windings, take the precaution of laying on the earth the Amazon, who remained in the same spot until the Negro returned to its assistance, who, having well ascertained and examined one of the entrances, resumed its burthen, and bore it into the interior. If the entrance to any gallery was unluckily obstructed by a mass of earth, and the Negro Ant wished to introduce by that way one of the Amazons, it quickly deposited its load, and began clearing away the impediment; this was no sooner effected, than the Amazon was again taken up, and carried triumphantly into the nest.

If individual facts prove the harmony which reigns between these two species, living under the same roof, general facts fully illustrate what has been already stated.

We may readily see, from the appearance of mixed ant-hills, they are the sole work of the Ash-coloured Ants, although they are of greater extent than simple ant-hills, inhabited by that species, arising from their double population, and the prodigious number of auxiliary ants they contain. Their form, the architecture displayed in their construction, the substance of which they are composed, the interior arrangement, is altogether alike. I have frequently seen the Negro Ants of compound ant-hills take advantage of the rain to construct new stories upon their original domicile; they also often increase the extent of it by forming halls and chambers on the exterior margin; so that in three or four days they form, as it were, a new dwelling around the first enclosure.

The Legionaries never venture abroad, like the Ash-coloured Ants, during the rain, nor do they even, during that period, advance so far as the outer gallery; nor are any seen, as one would suppose, presiding over the masons, in their work; indeed, the Negroes require neither an inspector, nor the excitement of the sting, to induce them to labour; for they are eager to build whilst the rain continues, and their work advances rapidly, on account of their number being infinitely more considerable than that of the labourers in a simple ant-hill. Their operations being finished, they are extremely solicitous the Legionaries should enjoy the advantage; to this end, they lose no time in transferring the colony from the old to the new habitation. But if we are desirous of witnessing a still more curious spectacle, we must observe them when they are about to change their domicile for one more convenient, it being upon them alone the office falls of deciding the urgency of an emigration, and of choosing the situation best adapted (usually one where the soil is loose, admitting of greater facility of mining) for a new establishment. We see them at first engaged in carrying each other to the place destined to this object, where each Negro Ant either begins immediately clearing away the earth, or returns to bring away more of its comrades. When the new habitation is sufficiently advanced, they transport thither all the Amazons. We now see, in the road of communication between the old and new city, a file of Negro Ants, carrying the Legionaries, whose colour strikingly contrasts with that of their conductors. By these faithful guardians, the males and females are afterwards brought away in the same manner, and on their arriving at the entrance of the lodge prepared for them, are placed successively before the door, when other Negro labourers come forward and take them into the nest. The larvæ and pupæ are now taken away in their turn, and safely deposited in the new habitation.

In the morning these trusty servants go in search of provisions for the whole colony; at one time they bring back little dead animals, at another time return with their stomachs full of the liquor furnished them by the pucerons. They may be constantly seen going and coming on the road to the ant-hill. This is not the case with the Legionaries, for they never go in quest of the pucerons, and it is a rare circumstance should they venture forth during the early part of the day.

We have now taken a view of the Negro Ants or auxiliaries in the several offices of, procuring provisions for the republic, constructing a common abode, and conducting thither its varied inhabitants; the Amazons, a colony of soldiers, have, on the contrary, no other occupation, and no other talent than that for war; their manners are altogether distinct. They seldom leave their retreat, unless the temperature be above the 16th degree of Reaumur (67° of Fahrenheit) when placed in the shade. The general rendezvous commonly takes place a little before five in the evening: I have, however, sometimes seen them take their departure earlier, but never before two, nor later than five. They always return at six or half past six. They never quit their abode, unless the weather be fine.

These insects have but one object in their excursions, that of stealing the young from an industrious race, and making slaves of them; and these are the very individuals, who, after a time, labour for this Amazon colony, rear their young, and furnish them with provisions. This being the sole aim of the Amazons, they never seize any but larvæ and working pupæ, for the males and females would be useless. Nature would not assuredly allow the destruction of the habitations of Negro Ants, since this would be to involve in equal ruin those of the Amazons.

These warlike ants are sufficiently well acquainted with all the nests inhabited by Ash-coloured Ants in their neighbourhood, to each of which, in turn, they pay a visit. The route is every day varied, and, as already stated, the same nest is often pillaged several times successively; but they never destroy those ant-hills from which they have carried off the young. In the combats, that almost invariably take place, but very few Negro Ants perish, since their adversaries have no desire of making them prisoners, or of disputing the possession of their invaded city. I have sometimes seen the Amazons, when disposed in column, take one direction, then suddenly return to the garrison, and again proceed in a contrary direction. I have also witnessed their army, but very rarely, separate into two divisions, each taking a different route. The smallest division, however, on perceiving it is not in sufficient force, falls back, and rejoins the other; but when their force is nearly equal, each party goes to pillage separately, and returns to the garrison laden with booty. It is not so much by their real force, as by their impetuosity, that they succeed in spreading dismay among the Ash-coloured Ants; for I have seen an army, composed, at the most, of only one hundred and fifty Amazons, penetrate one of their habitations, and afterwards safely convey the purloined pupæ to their own citadel. What motive can possibly influence the Amazons in taking a certain route, or falling upon one ant-hill, in preference to another? To this I can give no direct reply. I once witnessed a Legionary Ant leave the nest before the hour of departure, apparently on a journey of discovery; I watched its movements for some time in the grass, and found it to visit every dry situation, and every place which seemed to announce the existence of an ant-hill, but I lost sight of it before its return. I have also seen a few return alone from a distant spot, and enter precipitately the garrison, when the army put itself in motion, and commenced a line of march precisely in that direction by which the couriers had arrived; however, I can, by no means, affirm this was the reason of their departure.

The signal they adopt is extremely varied; sometimes they strike against each other with their forehead or mandibles previous to the commencement of their march; at other times they appear to excite, by the play of their antennæ, a warlike ardour among their companions; it would appear that in this way a knowledge of their route is communicated, for it seems to be fixed at the moment of departure, since the army proceeds straight to its purpose. What is remarkable in the arrangement is, that none of the ants composing the troop move constantly in the same direction; on their arrival at the head of the column, they make a little circuit en forme de boucle, and re-enter the main body, then, as before noticed, return to the rear-guard, for the purpose of giving instruction to those behind. Eight or ten of the Amazons seek every opportunity of outstripping their comrades; these form the front of the battalion, but this they scarcely attain before they fall back into the general mass, and thus the advanced guard sustains a continual renovation.

I have never seen Amazon females in these armies: the neuters alone, as in all the other species, subject themselves to the chances of war. They do not march by groping or feeling their way, but run after their companions in arms, without any fear of straggling, and even should they do so, which is rarely the case, they are then brought back to the ant-hill by some of the Negro Ants, who, upon discovering them, seem sufficiently to understand the nature of their situation.

I was once present when the whole army appeared to be deceived in its route. It commenced its march after the ordinary manner; in place, however, of following a straight line, it described a curve, and reached a distance of about fifty paces, halting several times. After diverging on all sides, without discovering any of the usual objects of attack, they fell again into column, and returned by the same road to their garrison, reaping no advantage from their expedition. The decision they took of returning would furnish ample matter for reflection. I shall not now, however, enlarge upon this subject, but limit myself to the question, how can this fact be explained on the supposition of a blind instinct?⁠[1] But here is a fact still more extraordinary. Upon their return our Amazons met with no flattering reception from the Negroes in the mixed ant-hill, who individually assailed, buffeted and dragged them to the outside of the nest, where they even obliged them to act on the defensive: this hostile disposition, however, continued only a few moments, when the Amazons were allowed to re-enter their citadel. Are we to conclude that the Negro Ants were surprised at seeing them arrive without their accustomed booty, or did the larvæ, &c. serve in their eyes as passports for those with whose fate their own was so intimately linked?

The Legionaries never take animal food. I have often cast among them living insects, such as caterpillars, worms, &c., but never observed they touched them. I have also placed before them small pieces of meat, raw and roasted, from which they turned away with equal indifference, the Negro Ants seizing upon it at the moment.

Another experiment, which I frequently repeated, was that of placing my hand before the army when in march; the Amazons passed between my fingers, unalarmed at my presence; none attempted to pinch or sting me. We could not put to the same proof, with impunity, all other species of ants.⁠[2]⁠

I have never seen the Amazons take nourishment but from the mouth of the Negroes. I have presented to them honey and fruit, which they left untasted. When hungry, they approach their auxiliaries, and these disgorge in their mouths the juices they have obtained in their daily intercourse with the pucerons.

An experiment that I tried upon the Legionaries convinced me of their dependance upon their humble companions, both for nourishment and habitation. I enclosed thirty of these ants, with several pupæ and larvæ of their own species, and twenty pupæ belonging to the Negroes, in a glass box, the bottom of which was covered with a thick layer of earth: I placed a little honey in the corner of their prison, and cut off all association with their auxiliaries. At first they appeared to pay some little attention to the larvæ; they carried them here and there, but presently replaced them. More than one-half of the Amazons died of hunger in less than two days. They had not even traced out a dwelling, and the few ants still in existence were languid, and without strength. I commiserated their condition, and gave them one of their black companions. This individual, unassisted, established order, formed a chamber in the earth, gathered together the larvæ, extricated several young ants that were ready to quit the condition of pupæ, and preserved the life of the remaining Amazons. This result needs no commentary: I leave to each the liberty of drawing his own conclusions.