Animal Intelligence. George John Romanes
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to meet the enemy. The Lasius species defend their large, strong, and very extensive nests against hostile attack or sieges with equal courage and skill, while other timid species seek to fly as speedily as possible with their larvæ, pupæ, and fruitful queens. There is, as Forel tells us, a regular barricade fight. Passage after passage is stopped and defended to the uttermost, so that the assailants can only advance step and step. Unless the latter are in an enormous majority, the struggle may last a very long time with these tactics. During this time, other workers are busy preparing subterranean passages backwards for eventual flight. Generally such passages are already made, and during a fight a new dome of the Lasius may be seen rising at a distance, it not being difficult for them to make this with the help of their extended subterranean passages and communications.
The F. exsecta or pressilabris fights in a peculiar way, which is due to care of their small and very tender bodies. It avoids all single combats, and always fights in closed ranks. Only when it thinks victory secure does it spring on its enemy's back. But its chief strength lies in the fact that many together always attack a foe. They nail down their opponent by seizing its legs and holding them firmly to the ground, while a comrade springs on the back of the defenceless creature and tries to bite through its neck. But if threatened the holders sometimes take flight, and so it happens that in battles between the exsectæ and the much stronger pratenses not a few of the latter are seen running about with a small enemy clutching their shoulders, and making violent efforts to tear the neck of its foe. If the bearer is then seized with cramp, the nervous cord has been injured. On the other hand, if an exsecta is seized by the back by a pratensis it is at once lost.
The tactics of the turf ants resemble those of the exsectæ, three or four of them seizing an opponent and pulling off his legs. In similar fashion the attack of the Lasius species is chiefly directed against the legs of its enemies, three, four, or five uniting in the effort. They understand barricade fighting particularly well in their large well-built dwellings, and if it comes to the worst fly by subterranean passages. They are feared by most ants on account of their numerical superiority. Forel one day poured the contents of ten nests of pratenses in front of a tree trunk inhabited by Lasius fuliginosus (jet ant). The siege at once began; but the jet ants called in help from the nests connected with their colony, and thick black columns were at once seen coming out from the surrounding trees. The pratenses were obliged to fly, and left behind them a mass of dead as well as their pupæ, which last were carried off by the victors to their nests to be eaten.
Battles, however, are not confined to species of ants having warlike and slave-making habits. The agricultural ants likewise at times wage fierce wars with one another. The importance of seeds to these ants, and the consequent value which they set upon them, induce the animals, when supplies are scarce, to plunder each other's nests. Thus Moggridge says,—
By far the most savage and prolonged contests which I have witnessed were those in which the combatants belong to two different colonies of the same species. . . . . The most singular contests are those which are waged for seeds by A. barbara, when one colony plunders the stores of an adjacent nest belonging to the same species, the weaker nest making prolonged though, for the most part, inefficient attempts to recover their property.
In the case of the other species of ant which I have watched fighting, the strife would last but a short time—a few hours or a day—but A. barbara will carry on the battle day after day and week after week. I was able to devote a good deal of time to watching the progress of a predatory war of this kind, waged by one nest of barbara against another, and which lasted for forty-six days, from January 18 to March 4!
I cannot of course declare positively that no cessation of hostilities may have taken place during the time, but I can affirm that whenever I visited the spot—and I did so on twelve days, or as nearly as possible twice a week—the scene was one of war and spoliation such as that which I shall now describe.
An active train of ants, nearly resembling an ordinary harvesting train, led from the entrance of one nest to that of another lower down the slope, and fifteen feet distant; but on closer examination it appeared that though the great mass of seed-bearers were travelling towards the upper nest, some few were going in the opposite direction and making for the lower. Besides this, at intervals, combats might be seen taking place, one ant seizing the free end of a seed carried by another, and endeavouring to wrench it away, and then frequently, as neither would let go, the stronger ant would drag seed and opponent towards its nest. At times other ants would interfere and seize one of the combatants and endeavour to drag it away, this often resulting in terrible mutilations, and especially in the loss of the abdomen, which would be torn off while the jaws of the victim retained their indomitable bull-dog grip upon the seed. Then the victor might be seen dragging away his prize, while its adversary, though now little more than a head and legs, offered a vigorous though of course ineffectual resistance. I frequently observed that the ants during these conflicts would endeavour to seize one another's antennæ, and that if this were effected, the ant thus assaulted would instantly release his hold, whether of seed or adversary, and appear utterly discomfited. No doubt the antennæ are their most sensitive parts, and injuries inflicted on these organs cause the greatest pain.
It was not until I had watched this scene for some days that I apprehended its true meaning, and discovered that the ants of the upper nest were robbing the granaries of the lower, while the latter tried to recover the stolen seeds both by fighting for them and by stealing seeds in their turn from the nest of their oppressors. The thieves, however, were evidently the stronger, and streams of ants laden with seeds arrived safely at the upper nest, while close observation showed that very few seeds were successfully carried on the reverse journey into the lower and plundered nest.
Thus when I fixed my attention on one of these robbed ants surreptitiously making its exit with the seed from the thieves' nest, and having overcome the opposition and dangers met with on its way, reaching, after a journey which took six minutes to accomplish, the entrance to its own home, I saw that it was violently deprived of its burden by a guard of ants stationed there apparently for the purpose, one of whom instantly started off and carried the seed all the way back again to the upper nest.
This I saw repeated several times.
After March 4 I never saw any acts of hostility between these nests, though the robbed nest was not abandoned. In another case of the same kind, however, where the struggle lasted thirty-one days, the robbed nest was at length completely abandoned, and on opening it I found all the granaries empty with one single exception, and this one was pierced by the matted roots of grasses and other plants, and must therefore have been long neglected by the ants. Strangely enough, not one of the seeds in this deserted granary showed traces of germination.
No doubt some very pressing need is the cause of these systematic raids in search of accumulations of seeds, and there can be little doubt that the requirements of distinct colonies of ants of the same species are often different even at the same season and date. Thus these warring colonies of ants were active on many days when the majority of the nests were completely closed; and I have even seen these robbers staggering along, enfeebled by the cold, and in wind and rain, when all other ants were safe below ground.
The agricultural ants of Texas do not appear to be less pugnacious than their European congeners. Thus MacCook says:—
A young community has sometimes to struggle into permanent prosperity through many perils. The following example is found in the unpublished Lincecum manuscripts. One day a new ant-city was observed to be located within ten or twelve yards of a long-established nest, a distance that the doctor thought would prove too near for peaceable possession—for the agriculturals seem to pre-empt a certain range of territory around their formicary as their own, within which no intrusion is allowed. He therefore concluded to keep these nests under close observation, and visited them frequently. Only a day or two had elapsed before he found that the inhabitants of the old city had made war upon the new. They had surrounded it in great numbers, and were entering, dragging out and killing the citizens. The young colonists, who seemed to be of less size than their adversaries, fought bravely, and, notwithstanding they were overwhelmed by superior numbers, killed and maimed many of their assailants.