Animal Intelligence. George John Romanes
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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.
As in all these cases the ants live on amicable terms with their guests, and in some cases even bestow labour upon them (as in carrying them from one nest to another during migration), it is evident that these insects are not only tolerated, but fostered by the ants. Moreover, as it seems absurd to credit ants with any mere fancy or caprice such as that of keeping pets, we can only conclude that these insects, like the aphides, are of some use to their hosts, although we are not yet in a position to surmise what this use can be.
Habits of Sleep and Cleanliness.—It is probable that all species of ants enjoy periods of true sleep alternating with those of activity; but actual observations on this subject have only been made on two or three species. The following is MacCook's account of these habits in the harvesting ant of Texas:—
The observation upon the ants now before me began at 8 o'clock; at 11 P.M. the cluster had nearly dissolved, only a few being asleep. To illustrate the soundness of this sleep I take the quill pen with which I write, and apply the feather end of it to an ant who is sleeping upon the soil. She has chosen a little oval depression in the surface, and lies with abdomen upon the raised edge, and face toward the lamp. Her legs are drawn up close to the body. She is perfectly still. I gently draw the feather tip along the body, stroking 'with the fur,' if I may so say. There is no motion. Again and again this action is repeated, the stroke gradually being made heavier, although always quite gentle. Still there is no change. The strokes are now directed upon the head, with the same result. Now the tip is applied to the neck, the point at which the head is united to the pro-thorax, with a waving motion intended to produce a sensation of tickling. The ant remains motionless. After continuing these experiments for several minutes, I arouse the sleeper by a sharp touch of the quill. She stretches out her head, then her legs, which she also shakes, steps nearer to the light, and begins to cleanse herself in the manner already described. This act invariably follows the waking of ants from sleep. The above description applies to the general habit of somnolence as observed upon the two named species of harvesting ants for nearly four months. I have often applied the quill, and even the point of a lead pencil, to the sleeping Floridians without breaking their slumber. There are some other details which have not appeared in the behaviour of the individual just put under observation.
Thus, I have several times seen the ants (Crudelis) yawning after awaking. I use this word for lack of one which more accurately expresses the behaviour. The action is very like that of the human animal; the mandibles are thrown open with the peculiar muscular strain which is familiar to all readers; the tongue also is sometimes thrust out, and the limbs stretched with the appearance, at least, of that tension which accompanies the yawn in the genus homo. During sleep the antennæ have a gentle, quivering, apparently involuntary motion, which seemed to me, at times, to have the regularity of breathing. I also often noted an occasional regular lifting up and setting down of the fore-feet, one leg after another, with almost a rhythmic motion.
The length of time during which sleep is prolonged appears to vary according to circumstances and, perhaps, organism. The large head-soldiers of the Floridian harvesters appear to have a more sluggish nature than the smaller workers. Their sleep is longer and heavier. The former fact the watch readily determined. The latter appeared from the greater stolidity of the creatures under disturbance. While the ants of one group are taking sleep others may be busy at work, and these stalk among and over the sleepers, jostling them quite vigorously at times. Again, new members occasionally join the group, and, in their desire to