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 The following example is found in the unpublished Lincecum manuscripts.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. The parties were scattered in struggling pairs over a space ten or fifteen feet around the city gate, and the ground was strewed with many dead bodies. The new colonists aimed altogether at cutting off the legs of their larger foes, which they accomplished with much success. The old-city warriors, on the contrary, gnawed and clipped off the heads and abdomens of their enemies. Two days afterward the battlefield was revisited, and many ants were found lying dead tightly locked together by legs and mandibles, while hundreds of decapitated bodies and severed heads were strewed over the ground.
Another example, which is given in the published paper, is quite similar, and had like result. In forty-eight hours the old settlers had exterminated the new. The distance between the nests was about 20 feet. While the young colonists remained in concealment they were not disturbed, but as soon as they began to clear away their open disk war was declared.
MacCook, however, says that 'these ants are not always so jealous of territorial encroachment, or at least must have different standards of rights.' For he observed many cases of nests situated within twenty, and even ten feet of one another, without a battle ever occurring between members of the two communities. Therefore, without questioning the accuracy of Lincecum's observations—which, indeed, present no scope for inaccuracy—he adds, 'That neighbouring ants, like neighbouring nations of civilised men, will fall out and wage war Lincecum's examples show. Perhaps we should be quite as unsuccessful in case of these ants as of our human congeners, should we seek a sufficient reason for these wars, or satisfactory cause for these differences in dealing with neighbours which appear from the comparison of Lincecum's observations with mine.'
In connection with the wars of these ants, the following quotations may also be made from the same author:—
The erratic ants do not appear to be held as common enemies by the agriculturals, and they are even permitted to establish their formicaries within the limits of the open disk. Sometimes, however, the diminutive hillocks which mark the entrance to an erratic ant-nest multiply beyond the limit of the agriculturals' forbearance. But they do not declare war, nor resort to any personal violence. Nevertheless, they get rid of them, oddly enough, by a regular system of vexatious obstructions. They suddenly conclude that there is urgent demand for improving their public domain. Forthwith they sally forth in large numbers, fall eagerly to work gathering the little black balls which are thrown up by the earth-worms in great quantities everywhere in the prairie soil, which they bring and heap upon the paved disk until all the erratic ant-nests are covered! The entire pavement is thus raised an inch or so, and pains are taken to deposit more balls upon and around the domiciles of their tiny neighbours than elsewhere. The erratics struggle vigorously against this Pompeian treatment; they bore through the avalanche of balls, only to find barriers laid in their way. The obstructions at length become so serious that it is impossible to keep the galleries open. The dwarfs cease to contend against destiny, and, gathering together their household stores, quietly evacuate the premises of the inhospitable giants. It is the triumph of the policy of obstruction, a bloodless but effectual opposition.
Lastly, MacCook records the history of an interesting engagement which he witnessed between two nests of Tetramorium cæspitum. It took place between Broad Street and Penn Square in Philadelphia, and lasted for nearly three weeks. Although all the combatants belonged to the same species, however great the confusion of the fight, friends were always distinguished from foes—apparently by contact of antennæ.
Habit of keeping Domestic Pets.—Many species of ants display the curious habit of keeping in their nests sundry kinds of other insects, which, so far as observation extends, are of no benefit to the ants, and which therefore have been regarded by observers as mere domestic pets. These 'pets' are for the most part species which occur nowhere else except in ants' nests, and each species of 'pet' is peculiar to certain species of ants. Thus Moggridge found 'a large number of a minute shining brown beetle moving about among the seeds' in the nests of the harvesting ant of the south of Europe, 'belonging to the scarce and very restricted genus Colnocera, called by Kraatz C. attæ, on account of its inhabiting the nests of ants belonging to the genus Atta.' He also observed inhabiting the same nests a minute cricket 'scarcely larger than a grain of wheat' (Gryllus myrmecophilus), which had been previously observed by Paolo Savi in the nests of several species of ants in Tuscany, where it lived on the best terms with its hosts, playing round the nests in warm weather, and retiring into them in stormy weather, while allowing the ants to carry it from place to place during migrations. Again, Mr. Bates observes that 'some of the most anomalous forms of coleopterous insects are those which live solely in the nests of ants.' Sir John Lubbock also, and other observers whom we need not wait to cite, mention similar facts. The Rev. Mr. White says that altogether 40 distinct species of Coleoptera, most of which he has in his own collection, are known to inhabit the nests of various species of ants, and to occur nowhere else.