How ants carry on war

No living creatures known to the writer so closely resemble man in the tendency to wage pitched battles as do ants. Vast numbers of separate species, or of hostile factions of the same species, may he seen massed in combat, which is continued for hours, days, or, in at least one case noted, for over a week. Some of the most extensive battles observed have been fought between neighboring communes of Tetramorium coespitum, a small dark-brown species common to America and Europe. It abounds in and around Philadelphia, where it is popularly known as the "pavement ant," on account of its habit of making its nest under the bricks and flags of sidewalks.

I have often seen them engaged upon the large pavingflags that cover the walk from the manse through the grassy terrace fronting the church at Chestnut and Thirty-seventh Street. They fairly blackened considerable spaces of the gray stones with the vast numbers of the combatants. Some details of one of these fights will give a fair type of all. In the centre the warriors were heaped several ranks high. The mass seemed to boil with the intensity of the action. There was no appearance of orderly array or "line of battle" formation. It was literally a melee, recalling descriptions of battles in the days of chivalry, when armored warriors fought hand to hand.

From the central mass the numbers gradually diminished until, as spaces opened in the surrounding fringe of the fight, one could see small groups of combatants scattered over several square feet of surface. Most of them were duels; but trios, quartets, quintets abounded. In one case six ants were engaged with one; in the centre, two were tugging with interlocked mandibles, and five others were grouped around, like spokes in a wheel, each sawing or pulling at a limb of the unfortunate central integer, who was being torn to pieces. Here and there a larger group would be piled upon one another, heaving, pushing, tugging, like the athletes of a football rush, but with mortal intent.

The duellists seized each other by the head, frequently interclasping mandibles, and pulling backward or swaying back and forth. It was literally a "tug of war." Again, one would have her antagonist grasped by the face above the mandibles, which placed the latter at a great disadvantage. In such and other cases both ants would often be reared upon the hind and middle legs, with abdomens turned under and stinging organs out-thrust, making vicious stabs at one another.

All over the field disengaged ants were running about, excitedly seeking a focman, incessantly stopping to challenge with antennae, then hastening on until a hostile party was met, when at once the two locked mandibles and fell to. Many ran to and fro, stopping now at one group, now at another, to nip an abdomen, gnaw a leg, or snap at face or antennae, and then would rush away to some more promising service.

Meantime, from the gates of the warring communes - small openings on the edge of the paved walk - two streams of recruits were pouring toward the scene of strife. Their bodies fairly quivered under the intensity of their emotion as they ran along, reminding one of human crowds hurrying to a fire or a fight. As the two opposing streams met and intermingled, ant tackled ant in deathly grapple, and thus the fury of the battle was fed.

Of one party, distinguished as "Alpha," a long file of warriors was running from the field along the trail to the home nest. They challenged briefly every passing fellow, and pushed on. I conceived, as a solution of this conduct, that this was a file of messengers bearing from the field an appeal for recruits. They certainly were not running away. All appearances and all experience were against that inference. At all events, the ideas of a recruiting detail, a call for relief, fell in with the analogy of a human battlefield so strongly suggested by the scene before me.

From the central point of the fight, as first seen at the edge of the walk nearest the "Alphas," the vortex of the combat gradually shifted toward the gate of their, antagonists, the "Gammas." At first it seemed as though that army were being slowly pushed from the field. But if so, the tide of battle afterward turned; for victory finally remained with them, as far as it could be adjudged to either party. At this period the field of battle was spread over a space two feet long by six inches wide, the fighters grouped most thickly about two centres, beyond and around which the walk was dotted with many duellists and small contending groups.

At 12.30 p.m. the battle, which had begun at 8.30 A.M., was practically over. The "rear guard" of the Alphas were continually dropping into their home trail, and numbers of Gammas were filing to their gate in a sluggish way. Not a recruit from either side was coming to the field. The dead lay in little windrows where the tide of battle had left them, or whither they had crawled to die, or the rising breeze had borne them. Here and there among them were ants still living but fatally hurt, struggling to drag their mutilated bodies from the mass. Even so, two enemies, when forced together in this grim fellowship, would grip one another and roll and strain, giving their waning strength to a last hostile tug.

It was a not inapt reminder of after - battle scenes among men. Only, there was no hospital corps separating the dead and bearing off the wounded; no surgeons plying their ministry of bodily help and repair, nor chaplains their ministry of spiritual consolation. Dead, dying, and wounded were all alike abandoned by their late comrades, a number of whom, on both sides, were now gathered around the pats of butter and sugar which I had vainly placed in hope to lure them from fighting. The refection which they refused during the heat of combat was eagerly accepted to refresh themselves after the toils of strife. That, too, was a quite human-like scene, for soldiers must eat and drink when the dreadful stress of battle is eased. However, there was no attempt by the living ants to feed upon the dead, as one sees under other conditions.

The state of the wounded was pitiful, an exhibit in miniature of the dreadful aftermath of human battles. For example, here was a warrior whose middle leg on one side was sound, the hind leg cut off at the thigh, the front leg at the trochanter - a mere stump. On the opposite side the hind and middle legs retained all the parts, but were broken, curved, useless, like paralyzed limbs, the joint effect of its enemies' mandibles and acid batteries. Its antennae were both paralyzed, bent up, and motionless. It was thus bereft of all sense of direction, and all power of communication and progressive motion. It lifted up its head again and again in vain efforts to rise. It shook its stumps of legs, rolled upon its side, rested a moment, and then with ruling passion of emmet tidiness, strong even in death, struggled to support itself upon its abdomen, and tried to cleanse (perhaps to heal) with its tongue a fore leg.

Its adversary had not a whole leg left, its most perfect one being a middle leg that had lost the foot. All the others were torn off to the thigh, or the tibia, or close to the body, and one antenna was gone. There the two foes floundered close together, dismembered and dying, left to their fate by the comrades who had mutually helped in the achievement of this great victory. Like examples were scattered over the field, from which the rage of conflict had died away, except as it lingered here and there in duels or small groups of combatants doggedly fighting out their controversy to the death.

From time to time various groups had been removed from the mass, and placed in artificial nests prepared with a view to special experiments. Among these was a pair whose fate I wished to follow separately. One ant, that seemed to be quite sound, was interlocked with an antagonist much damaged, having lost several legs and an antenna. But it had tightly gripped in its jaws a leg of its adversary, who snapped at its antagonist's neck and face, and squirmed and doubled, and strove, with many contortions but in vain, to disable its opponent and get free.

As it promised to be a long engagement, I left them alone in their box and turned to view the battle. When I next saw the pair the duel was finished. The maimed warrior lay dead and near by the victor was seated upon a pebble nonchalantly preening her ruffled coat, and with comb and tongue and spined limbs was repairing the damage of battle.

I placed her near the Gamma gate, wishing to see if she could find her way home, and what would be her conduct and reception. She ran about in an involved path for nearly fifteen minutes, covering a great space, and at last fell upon the regular trail to the nest used by the ants of that commune. But as she showed no familiarity with the field, I concluded that she belonged elsewhere, and transferred her to the vicinage of gate Beta, one of the outlets in the territory of the Alpha colony.

She circled around in an irregular course, always drawing a little nearer to Beta. In her march she met a pair of combatants, exchanged antennal salutations, and passed on. Presently she came upon another duel, again challenged, and again passed on. She acted as if lost, but kept bearing gradually toward Alpha gate. Now she met several scouts who challenged her with some evident doubt as to her status, but let her go. Next she was stopped by a group with whom, plainly enough, was exchanged a satisfactory password and "How d'e do!" and then she was off with a joyous trot. She had struck the home trail! In a moment she dived into the gate.

Home at last - home from the wars! Doubtless there may have been, on her part, a passing satisfaction like that which Burns sang in The Soldier's Return:

"When wild war's deadly blast was blawn, An' gentle peace returning,
Wi' mony a sweet babe fatherless, An' mony a widow mourning."

But we may be sure it was but a fleeting emotion, and that on the part of the commune there was neither for her nor for any other returning braves a civic demonstration of "Welcome home from war." They glided simply and naturally, as though from a night's rest, into the regular routine of communal duty, and there was no more to-do about it. Every active member of society stood ready to take the same risk, do the same service, make the same sacrifice. What occasion was there for special hero-mongering?

Verily; and when human commonwealths have reached the same level of patriotism and civil devotion, citizens may fairly take a like attitude. But until then gratitude for and due recognition of true heroism in army and navy must be held as a civic virtue, and the poet's, admonition be in place:

"The brave, poor soldier ne'er despise,
Nor count him for a stranger; Remember, he's his country's stay In day and hour of danger."

What was the cause of these conflicts between insects that apparently ought to have been close friends? In at least one case noted the quarrel clearly arose over a find of rations. The centre of the warring mass was some fatty matter which had been thrown on and around the seams of a brick pavement through which a large formicary had cut its gates. From the battlefield a column of Tetramoriums three or four lines deep stretched along a depression made by a shallow surface drain to a second nest under a gate that led through a party-wall into a house yard.

Apparently, the ants from the curb colony had fallen upon the unctuous treasure which had dropped by their door, but had been disturbed in their "feast of fat things" by stragglers frorn the gate nest. These were attacked; others came, and were also attacked. Messengers ran to the gate nest for reinforcements; fresh squadrons issued from the curb colony, and so the battle grew. It is probable that many like conflicts arise from rivalries for the possession of food; and, as in the above case, it is almost sure that a communal war springs out of a quarrel between a few, who, appealing to civic partisanship, finally enlist in their contention the two communities represented. Of course, conflicts between separate genera and species are readily explained by race antipathy.

Perhaps the most usual cause for the wars waged between our city Tetramoriums is the irritation produced by the encroachment of the mining workers upon their neighbors in the enlargement of their living-quarters. This is the more likely, as the most common period for the battles is the early spring, when the demand for larger room is greatest for the accommodation of the rapidly increasing young of the commune. The galleries, nurseries, and living-rooms for the numerous males and females are pushed out with such fervor that the excavated pellets rise into heaps and moundlets around the nest gates. In such conditions the overlapping of the new boundaries is inevitable, and in the tense nervous strain and high communal pressure under which the work is being pushed, the contact between the rival parties is almost sure to be hostile.

As the season advances, and the excitement of homebuilding and the keen fervor of communal parentalism abate, the war fever cools down, and peace prevails. Whatever be thought of the above as an explanation of the wars of our city Tetramoriums, it at least opens to us a secret chapter in the life of ant communities that awakens unusual interest. It is the story of underground wars. The surface combats are sufficiently intense and tragical. But there is a mystery about the battles waged within the dark caverns of the communes beneath the surface that clothes them with an air of romance.

Here are mining and countermining, just as one sees it in engineering campaigns of men, without the horrible accessories of explosives. Here a gallery is broken through; a sharp engagement follows; the assaulted party rallies to the defence of the works; the victors have pushed their way in; the vanquished fall back. But behind them a working detail has thrown up a strong barricade, behind which the besieged rally, and the battle goes on anew. In the case of such a "thief ant" as Solenopsis fugax, whose diminutive commune is constructed within that of some far larger host, the mining tactics and the spirited resistance may be observed in artificial glass nests, and they are extremely interesting to watch. A rather remarkable feature of the communal habits of this ant is that its swarming does not occur, as Forel observes, until September, long after that of its host ants (July, August). Thus they can get to the surface safely and swarm undisturbed, that belligerent period of their huge neighbors being overpast.

But in most cases no sufficient reason appeared for the frequent wars between the pavement ants. They are of one species, and in some cases, as it seemed to me, of one commune. Why should they fight? To be sure, civil wars are, unhappily, not unnatural to human societies, and indeed to social aggregations of humbler creatures. But somehow one expects better things of ants, even though their "ways" may not be held as "wise" in all things as those of Solomon's harvesters. Yet almost the first act of our city Tetramoriums, upon issuing from their winter quarters, is to engage in fierce war with their neighbors or fellow-formicarians. At times throughout the season these hostilities were renewed.

If, as we conjecture, the individuals be of one nest, is this nature's mode of distributing the species from the home centre, by causing the worsted party to emigrate? Or, supposing the combatants to be of separate adjoining communities, is this wasting pugnacity a sort of emmetonian malthusianism which the surplus population is reduced and kept within due bounds, much to the comfort of survivors, and more to the satisfaction of man? Whatever theory or conjecture one adopts, he is apt to conclude that it is well-nigh as hard to find a really good reason for wars of ants as for many wars of man.

Another perplexing problem here arises: How do these ant warriors recognize friend from foe? The device of variant uniforms does not serve in this case, for they are all alike. Take a group of combatants in the hand and put them under a magnifier, as one can readily do, so intent are they upon mutual destruction. The most careful observer can note no difference be
tween individuals of the two factions, yet they do infallibly and instantly distinguish their nest-fellows from the enemy. This is done by the antennae, which are kept in constant motion, the tips describing sundry curves. At a meeting between ants these organs touch and embrace the face; if the parties be friends, they pass on; if foes, they straightway begin to fight. The newcomers, thronging to the battle-centre, where hundreds are struggling in a heap that is chaos to human eyes, but presents no difficulty to emmet senses, plunge into the seething mass and instantly recognize and join combat with their enemies. How is it done?

During the summer, while pondering this problem, it occurred to the writer that this recognition was based upon a certain odor, emitted in different degrees of intensity by the respective factions, or upon two distinct characteristic party odors. The degree of odor or difference in odors, he thought, might be dependent upon some peculiarity in the physical condition or environment of the antagonists. Supposing that there were any truth in this theory, it further occurred to him that the presence of an artificial and alien perfume strong enough to neutralize the distinctive animal odors, ordegrees of odor, and environ the combatants with a foreign and common odor, would have a tendency to confuse the ants, and disturb or destroy their recognition of the distasteful and exciting element. In which case he conjectured that the result might be their pacification and reconciliation.

Experiments were made to test this hypothesis. A number of warring Tetramoriums, taken upon a flower border, were placed together in a large glass vessel upon some soil. The jar was vigorously shaken so that, if possible, the mechanical agitation might separate the combatants. The ants emerged quite unaffected by the miniature earthquake, to continue or recommence the fight. When the surface was well covered with them, and the battle was again at its height, a ball of paper saturated with cologne water was introduced into the jar. The ants showed no signs of pain, displeasure, or intoxication under the strong fumes. Some ran freely over the paper. But in a few seconds the warriors had unclasped mandibles, released their hold of enemies' legs, antennae, and bodies, and, after a brief interval of seeming confusion, began to burrow galleries in the earth with the utmost harmony.

There was no renewal of the battle. The quondam foes dwelt together for several days in absolute unity and fraternity, amicably feeding, burrowing, and building. This experiment was followed by others, varying the conditions and the individuals, but holding to the species. The result was always the same with Tetramorium coespitum. The perfume of the cologne proved a complete pacificator of the contending parties, and so far verified the theory. The alien odor neutralized the distinctive nest odors which had served to identify friends and foes, permitting them thus to return to their normal neighborliness; or in some way had mollified the hostile parties, and transformed them from enemies into amicable associates.

Similar experiments were tried with colonies of carpenter ants taken from the Alleghany Mountains and from Logan Square, Philadelphia. These pointed to a conclusion just the reverse of the above. Whatever the cause - a failure of the experimenter in arranging his conditions, or the presence of some disturbing element that was overlooked, or because one or both parties were too far saturated and seasoned in their own native nestodor to respond to the cologne treatment - the fact was that the experiments led to opposite conclusions.

However, I had little doubt then, and have none now, that the original inference was substantially true in the case of wars between separate communes. The ants were recognized by a special odor which they absorbed during residence, and which was stronger or weaker according to age and environment and conditions unknown. How acute and delicate and accurate must be the sense organs seated in the antennae, which are instruments of recognition, the facts related will show.

"He does not carry the odor of my species, my commune, or my caste. Therefore, we will fight!" To a human philosopher meditating upon these things, it seems a small difference on which to divide two such closely related creatures into hostile camps. But mayhap he who counts this for abatement of the common fame of ants for wisdom might find, in the history of human wars, originating causes as insignificant and unreasonable.