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.
Itused 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 ofThe 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 secondand 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 maystop, 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 oneinsect 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 characteristiccrepitus,” 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 introducedinto 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. Withthis 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]
A soldier, too, has been observed to kill and partially eat one of its worker companions, nor is it altogether uncommon for an individual of any class, after licking, for some little while, the leg of another, suddenly to snap it off. The bond of union, therefore, though sufficiently developed to allow of an elaborate social organisation, is not so strong between members of the same termitary as it is in the case of ants, amongst which latter such unseemly conduct is never known to occur. So, too, unless a particular chemical substance, which seems to have a maddening effect, be flung amongst them, ants of onecommunity never attack each other. Amongst white ants, however, warfare will occasionally break out within the nest, more especially if this be disturbed, in which case the soldiers are apt to turn savagely on those nearest to them, perhaps considering them as the cause of the calamity. Still, upon the whole, order, and, if not friendship, at least co-operation, is conspicuously displayed, and the majority often interfere to put a stop to such individual or partial combats as may from time to time break out.
There is more excuse for the soldier termites in their cannibalistic propensities, since owing to the special development of their jaws, which are long and slender, they are unable to triturate wood, which is the basis of diet of these insects. They might die, therefore, but for such occasional lapses, were it not the common practice for all members of the community to feed one another, though the soldiers, for the above reason, are much more dependent on such aid. The food thus administered has just been swallowed by the individual who parts with it. Such transfer is performed in two ways, the first of which is familiar enough—that process, namely, known as regurgitation—but the second and more staple one is too peculiar to be dealt with in a non-scientific work. When a termite regurgitates, an exceedingly small round pellet of reddish-brown colour may be seen, by attentive observation, to form about the mouth, and gradually to increase in size till it becomes plainly apparent, and is seen to consist of food—that is to say, wood—which has previously been swallowed, in a moistened and softenedcondition. Sometimes this pellet is used for building purposes, but often another termite comes forward, receives, and swallows it.
Another article of diet which has a peculiar efficacy, and is used for a certain purpose, has been already alluded to—viz. saliva. This, we are told, “issues,” when required to do so, “as a colourless and distinctly alkaline liquid. It collects on the labium (the insect equivalent of lips) as a small drop, which may be employed either as a cement in building or as food for others. These may either possess themselves of the drop and then retreat a little way in order to swallow it gradually, or they may receive it from the one which secretes it and clearly provides it for them as an article of diet. The assimilation of a drop requires a certain number of acts of deglutition, which may be counted, and are usually four or five.”[9]Very young larvæ (the whole community, it must be remembered, are either in this or the pupal state) are fed after this fashion, until sufficiently advanced to be able to swallow wood-meal. Under this course of diet the abdomen becomes remarkably transparent, and this, in older individuals, is an indication that they are being bred up by the workers to become royal substitutes. The development, therefore, of termites from the larval to the perfect, or, at least, the sexually perfect form, seems to be wholly dependent on their being fed with this substance.
As is well known, the body of the queen termite, in the African and other tropical species, swells, when about to lay, to an enormous size, but this is not nearly so noticeably the case with her European representatives. Neitheris a cell, in this case, constructed for her accommodation, but the royal pair, whether they are true king and queen, or only substitutes, “remain, in close proximity, in the heart of the nest, where the inmates are always most crowded.” They are not imprisoned, therefore; but can go from one place to another, should they, as sometimes happens, wish to change their situation. In this they would seem to be happier than their more specially accommodated royal cousins, but no doubt, with the latter, or at any rate with the queen, the instinct of locomotion ceases with the capacity to indulge in it. The purpose of the specially made cell is probably rather to guard than to restrain the queen.
In regard to the swarming of white ants—another habit in which we are reminded both of ants and bees—with the subsequent founding of a new colony, Professor Grassi has the following remarks to make. They apply more especially to the larger of the two European species, viz. Calotermes. “Before swarming,” he tells us, “they collect near one of the exit-holes of the termitary, and when the proper time comes, issue from it in ones or twos, so that the twenty or thirty members who are ready to take flight emerge in perhaps a quarter of an hour. Once outside, they run upwards, if the locality admits of it, for a few metres, and then only do they take wing. In a room they fly towards the light, and if a wind is blowing they follow its direction. Some, becoming tired, settle soon upon trunks of trees, and all may do this eventually. Here they group themselves into pairs, the males and females of which must frequently be derivedfrom separate nests, since the sexes swarm separately; this acts as a safeguard by which Calotermes habitually avoids in and in breeding. Matrimonial alliances having been thus formed, the work of excavation commences, each pair seeking for some decayed spot in which to bury themselves and become, in time, the parents of a fresh community. The wings, by this time, have been got rid of. They may be shed by coming into contact with an obstacle, or by getting damp and adhering to some spot, while the insect continues to move. But, if not favoured by chance, the Calotermite purposely rids itself of these now useless encumbrances. Thus four perfect insects were captured after flying about the room, and put under a piece of rotten wood. Hardly had they settled when they stripped off their wings by resting the tips against some projecting corner of the wood, and then moving backwards a little, so that the wings bent near the base, broke, and dropped off. When rid of them they began to gnaw the wood, at first along and then across the grain. When they encountered each other by chance they first threatened to bite one another, and then ran off in opposite directions. This was because they were of the same sex. Had they been of opposite ones, an attachment, under such circumstances, would no doubt have been formed between them.”[9]
This is all the space which I can afford to these interesting insects. There are many other points in connection with them which I might have touched upon, but I thought it better to say less about what may be read by anyone in a score or so of works, and select asmy text-book a series of the closest and most interesting observations, which lie buried in the pages of a scientific journal not at all likely to meet the public eye. Where possible, I shall be guided by the same or a similar principle throughout this small work.