CHAPTER II
Ant language—Stridulatory organs—How white ants communicate—Conversation through convulsions—Nests in tubes—Detection of a “crepitus”—Mutual recognition—Cannibalistic propensities—Royal jealousy—Loyal assassins—A kingly feast—Methods of feeding—Foundation of colonies—Swarming habits.
It used to be supposed that such communication as ants are capable of holding with one another took place entirely, or almost entirely, through the mutual stroking of the antennæ, and Sir John Lubbock (now Lord Avebury) was unable to satisfy himself, after numerous experiments, that they could either hear or utter any sound. It is now known, however, that not only can some ants emit various sounds at their pleasure—as, indeed, is sufficiently obvious in the case of one or two species—but also that they possess special structures enabling them to do so, and the existence of which is inconceivable, except on the supposition that they both hear and attach a meaning to the notes thus evolved. Thus at a meeting of the Entomological Society held in the year 1893, Dr. David Sharp (author of the “Insects” portion of The Cambridge Natural History) declared that “examination revealed the existence in ants of the most perfect stridulating or sound-producing organs yet discovered in insects, these being situated on the second and third segments of the abdomen in certain species. The sounds produced were of the greatest delicacy, and it appeared doubtful whether the microphone would be able to assist the human ear in their detection”—which, indeed, it has not yet done.[[7]] Later, in the work above mentioned, Dr. Sharp remarks, “In many ants these parts”—that is to say the abdominal segments—“bear highly developed stridulating organs, and the delicacy and perfection of the articulations allow the parts to be moved, either with or without producing stridulation.”[[8]]
As these ant utterances are not sufficiently loud to be audible to our human ears, they must, I suppose, be inferred from the existence of the organs above-mentioned, and the way in which they work; but this is surely sufficient data to go upon, since it is hardly possible for one hard substance to grate upon another silently. Forel, accordingly, as well as Janet and other observers, now believe sound to be one of the principal means by which ants hold converse with each other, and it is interesting to find that Grassi and Sandias have arrived at the same conclusion in regard to white ants, or termites. Their opinion, together with the facts upon which it has been founded, is thus expressed:—
“Several writers have mentioned the convulsive movements characteristic of Termites. These movements, or quiverings, are easily observed in Calotermes, and may be repeated periodically at very short intervals, almost at the frequency of the pulse-rate. In the act of quivering, the legs are held motionless, whilst the body is shaken forwards and backwards. Sometimes a white ant may stop, whilst running, in order to quiver one or more times. Occasionally these convulsive movements are repeated a few times only, and then stop altogether; but at other times they recur after a few seconds’ or, at most, a few minutes’ rest, and may thus be continued, sometimes, for hours, at regular or irregular intervals. In the intervals between successive convulsions the insect remains still, or progresses for a short distance only. These movements are executed by all members of the colony except the newly hatched ones. I have satisfied myself,” continues Professor Grassi, “by careful observation of the phenomena exhibited in tube-nests, that these convulsions serve as a cry to summon help or give alarm, or as a lament: in short as a mode of intercommunication.”[[9]]
The same observers then go on to tell us that if white ants are disturbed in any sudden way, as by the too rough shaking of their nest, or by a light being suddenly flung upon it, or if otherwise annoyed, “all the members of the colony begin to quiver, except those that are running briskly about in search of a better situation.”[[9]] When dying, too, they will sometimes quiver in this way, at intervals of a few minutes, for as much as an hour or two, or even longer. Should an enemy—such as those we have been speaking of—be introduced of a sudden into the nest, the less valiant members of it prefer to run away, but in the midst of their retreat they may often be seen to stop and quiver with unusual energy. Their object in these cases seems to be to raise a general alarm, nor is it long before they are successful. Again, if whilst one insect is burrowing into wood another outside should quiver in this way, the burrower quickly comes out, as though in response to some signal of alarm. From all this it seems evident that these curious movements must be accompanied by some sound, or sounds, inaudible to our human ears, and perhaps having a varied range, and with considerable power of modulation. To produce them, however, some stridulating or other organs would seem to be necessary, and of these, though they must, if there, be visible under the microscope, Professor Grassi says nothing. Possibly, however, sounds may be produced by the rubbing together of various parts of the body without any special apparatus having been developed, in which case the language, if we may call it so, cannot be so rich or copious.
The above remarks apply more especially to the larger of the two white ants of Southern Europe. In regard to the smaller one, Professor Grassi makes the following interesting remarks: “Termes makes the same convulsive movements as does Calotermes, but the soldier of this species is able to produce a special creaking sound, which arises, whenever the head is held horizontally, during the act of quivering, by friction between the back of the head and the front part of the thorax. But whenever the head, during this act, is held in the usual position, which is not quite horizontal, no perceptible sound is produced, owing to the absence of such friction. The soldiers of Termes, therefore, possess two distinct modes of communication, whilst those of Calotermes have only one, in which no perceptible sound is produced. This characteristic crepitus,” continues the Professor, “may be heard, at frequent intervals, by applying the ear to a tube containing a nest of Termites. This proves that the quivering motions are a constant feature in undisturbed nests, so that they cannot be employed only as signals of alarm or distress. I conclude, therefore, that besides such special significations these convulsive movements must also have the value of ordinary speech; that they constitute, in short, a means of intercommunication. The same conclusion holds good for Calotermes (the one we have hitherto been talking about), and I imagine that the quivering of both species produces a sound which is perceptible to the insects themselves, but inaudible to the human ear.”[[9]]
Members of the same ant community are known to recognise each other, and this is no less the case with the white ants, or termites. Thus when a few of the latter were removed from the termitary and returned to it after five or six hours, the population showed no signs of alarm—not scurrying wildly about as they would have done had strangers been introduced—but remained quiet and orderly. It was objected, however, though I cannot see the force of such an objection, that the exiles, on their return, would have instantly recognised their old nest, and thus, knowing exactly where to go and what to do, they would have created no disorder, and consequently roused no suspicion, amongst the other members of the colony. To meet this theory Professor Grassi provided one of his colonies with a new nest from which he excluded a certain number of individuals, so that when these were introduced into it, an hour or two after their companions had settled down in their fresh abode, it was, of course, quite unfamiliar to them. In spite of this, however, they caused no disturbance, but were clearly recognised as friends. When, however, a few strangers of the same species were introduced, they created great alarm amongst the rightful proprietors, who scattered in all directions. In a little while, however, all was again quiet, and as no fighting was observed, it would appear that, amongst the termites, strangers from different nests soon become friendly with one another. This, however, applies to the commoners only, it is not the same where royalty is concerned. Thus when a second king and queen were introduced into a termitary already provided with a pair, they were at once attacked by the subjects of the latter, who loyally bit off their legs. Two days afterwards the reigning queen was herself seen to attack the male pretender, or rather unfortunate victim of scientific curiosity. He, however, though without legs to assist him, managed to drag himself away, but was afterwards found dead, with the outraged queen nibbling vindictively at his mutilated stumps. Next day the stranger queen was also found dead, and the same thing always happened whenever the experiment was repeated. Sometimes, indeed, the supernumerary royal pair, or pairs, had disappeared altogether, from which it seems clear that they must have been not only killed, but eaten.
Cannibalism, indeed, is rather an institution than a vice in the termitary. To begin with, the cast skin of every member is eaten by the others as a matter of course. With this view, any individual who is ready to moult receives the skilled aid of two or more assistants, who either eat the outer portion of their friend, bit by bit, as they shred it off, or else carry it away whole and devour it at their leisure. Sometimes, moreover, one, after licking another affectionately, in the way that ants do, may be seen to give it a covert bite, as though desirous of something more filling, whilst any sick member is eaten by its companions before it is dead. Royalty is not exempt from this treatment, and, on one occasion, nine individuals, including one soldier, were observed by Professor Grassi in the act of enjoying a meal on the body of a substitute king who was in process of moulting. The wretched animal was still alive, and writhed all over its body, to free itself from the torture. The nine assassins were probably annoyed at the light, for they at once stopped eating, and jointly carried off the victim to a darker part of the nest. Meanwhile many others crowded up to partake in this feast of royal flesh.[[9]]