CHAPTER III
Ants and white ants—Guest insects—Ants’-nest beetles—Doubtful relations—A strange forbearance—Yellow ants and white wood-lice—Beetles fed by ants.
FROM what has been said about the Termites in the last chapter, it is clear that they very much resemble ants in their habits, so that it is no wonder that they have long passed for ants in popular estimation. Such a similarity is quite enough to justify one part of the name, as names go; and as for the word white, which entomologists are always complaining about, that is quite near enough too, for though their bodies are not white, but yellow, yet the greater part of them—the soft fat abdomen, which particularly catches the eye—is of such a light yellow that it suggests white in contrast to the darker colouring of most ants. Scientific men—unless their particular science is philology—are dreadful pedants in regard to names, and always want to substitute their own manufactured ones, which have no real life in them, for what has sprung up naturally on the lips of the people. Thus, instead of hedge-sparrow—a name that explains itself to anyone who has seen the bird and knows something of its ways—ornithologists would have us say “hedge-accentor”—a preposterous concoction—and stormy petrel should, according to them, be “storm-petrel,”because the bird itself cannot be stormy, whatever the sea may be. No imagination behind the common use of language, then. No poetic transference of attributes. All is to be as prosy as professors can make it, and “we must speak by the card, or equivocation will undo us.” But names, which are a part of language, come into being as language itself does—spontaneously, that is to say, and by a natural growth. They are right because they exist; and the very errors contained in them—telling, as they do, of popular beliefs and superstitions—are of greater and wider interest than the rectitudes of a few pedants. Could they play with substance as they can with breath, these wise simpletons would first draw up a theory of anatomy, and then annul all bodies that did not conform to it. Such and such a word or name is wrong, in their eyes, though it exists quite as naturally as any nerve or muscle, and is quite as tough though only made of air. This last they will find if they live long enough, and “hedge-sparrow” and “stormy petrel” will survive all their lifeless substitutions, though embalmed in many dull paragraphs of many dull books.
But let us come back from words to things. Much as the white ants resemble real ones in many of their habits, the more remarkable ones that distinguish the latter are not practised by them. They make no slaves and keep no domestic animals—at least I have never heard of their doing so, though in natural history one must always be prepared for new discoveries. Many insects do, in fact, live with them in the termitary, just as others live in the formicaries of ants, and it is quitepossible that, when these have been better studied, some of them will be found to have special relations—involving mutual intelligent action—with their landlords.
At present, however, we seem to have little or no information on this head. With ants it is different, and perhaps one of the most interesting chapters in their history is that which has to do with thesemyrmecophilous, or guest insects, as they are called.[10]Take, for instance, the ants’-nest beetles, and especially one family—thePaussidæ—which numbers some 200 species, every one of which passes the whole of its life, when not flying by night, within the nest of some species of ant. These beetles are small, as might be expected, the largest being not more than half an inch in length, but present an extraordinary appearance owing to the antennæ ending in two broad palmated surfaces, like the horns of a moose deer, which project outwards, one on each side, at right angles with two short stalks, forming the only serviceable joints of these strangely modified feelers. All the other ones (in some species, at any rate) have been fused and welded together to form these flattened club-like structures, the use of which is not at first-sight apparent, and may not be fully understood. If, however, apaussusis laid on its back upon a flat surface, a predicament which would be as embarrassing to many beetles as it is to a turtle, one of their special functions is at once seen. Turning back the two clubs till they rest on the ground, and making the joint rigid, the insect uses the one most conveniently placed as alever, and soon gets on to its legs again. Could we imagine that such an expedient would often need to be resorted to, the curious modification of the antennæ is at once explained; but it probably rarely happens that any small beetle finds itself on its back in a place where there are no irregularities to aid it in righting itself. Possibly, however, the smooth galleries or chambers of some of the larger ants might expose theseMyrmicophilæto such a catastrophe, though, for my part, I suppose that the antennæ are used in some other special way which is of far more importance to their owners.
The relations existing between the ants and these curious beetles has not yet been fully made out. It is true that the various species ofPaussidæhave upon some part of their bodies a smooth downy substance—apubescence, to use the word dear to entomologists—which in other ants’-nest beetles is known to exude a sweet honey-like dew which the ants, not unnaturally, are very fond of, and for which they assiduously lick them. As they have also been seen to lick theirPaussi, we seem, here, to have at least the root of the matter, nor does the fact that, at other times, when perhaps these have ceased to supply the attraction, they pay little attention to them, seem of much importance, since we are all neglected when we have given what we have to give. But there are other circumstances not of so straightforward a nature. It has been lately discovered by a French observer—M. Péringuey—that thesePaussidæ, welcome guests as they generally are, will yet, sometimes, eat the larvæ of the ants with whom they live, when any small worker isengaged in carrying them from one place to another. The ants resent this, and occasionally a large one, who feels himself equal to the undertaking, will attack and even kill aPaussusthat he sees behaving in such a manner. Yet, with all this, so valued are these beetles by the ants that they often drag them back into their nests, when they have approached, or emerge from, the entrance. On such occasions, and also when the ants attack and even dismember them, thePaussidæmake no sort of resistance. Yet they are extremely well able to do so, being armed with a weapon of tremendous efficiency, by which in a moment they could kill or stun a whole crowd of ants round about them. For they are bombardier beetles, having the power at any moment of discharging a fluid of a highly acrid nature, and so volatile that, on coming in contact with the air, it explodes with a puff of blue smoke, exhaling at the same time a very pungent and unpleasant odour. When they are tickled with a straw, even, this bombardment at once takes place, and ants all round are seen to stagger or drop to the earth. Small workers are killed, large ones retreat in confusion; yet the owner of this deadly battery, which can only have been developed for the express purpose of overwhelming an enemy, will not, even to save life or limb, discharge it against an ant—not one, at least, to whom it stands in these somewhat doubtful relations.
How have these relations—whatever in their entirety they may be—come about? My own idea is that these beetles, like some other creatures—amongst them the little white wood-louse that lives with our ownFormicaflava—found ants’ nests very comfortable places of retirement, since, by reason of their peculiar weapon of defence, they could defy any attempt to interfere with them, on the part of the ants. The ants, on their side, would soon have given up molesting them, so that, never requiring to defend themselves against the creatures by whom they were surrounded, the intruders got to associate them with quite other ideas, and, having first lost the habit, at length lost the power of turning their artillery in this direction. MeanwhilePaussus, owing to its sweet secretion, which, after relations had once become amicable, the ants would soon have discovered, had got to be a very welcome guest, so much so that, even when it took to eating their larvæ, they retained their love for it, as a species, though resenting such conduct upon the individual. And now the once redoubtable invader could be punished with impunity, for the habit of never discharging against an ant had become a fixed, inherited instinct, not to be got rid of even though life were at stake. Thus, as it appears to me, it may have come about that, though armed with dynamite, and carrying bombs, no livingPaussushas ever defended itself against an ant, and no living ant, perhaps, ever seen aPaussusdischarge its artillery. Of course these are only conjectures, and the last, especially, may be opposed to fact, since it has been suggested that one way in whichPaussusmay make itself useful within the nest of its hosts, may be by bombarding certain obnoxious parasites, or other would-be invaders. This does not, however, appear to me to be likely, for how could these explosion take place, under such circumstances,without doing damage to the ants themselves? In one’s own house one would hardly wish a bomb to be thrown, even against one’s greatest enemy—at any rate not in the drawing-room. That the ants should, by this means, be able, or, if able, willing to rid themselves of the mites which infest them, as has been conjectured, seems especially unlikely—indeed, hardly possible. On the whole, it seems to me that the relations at present existing between the two insects could only have grown up throughPaussushaving ceased to discharge, not only at an ant, but even—owing, probably, to there never being any occasion for it—in an ants’ nest. The experimental tickling with a straw was, of course, an artificial stimulus. In spite of its sweet secretion, I cannot see how a beetle with such a power at its command asPaussushas, can have been originally selected by the ants for domestication, but, on the other hand, an armed invader might easily, by coincidence, possess some property which would make it, in time, of use and value to the population on which it forced itself.
An example of an invader having no such merit, but harmless, and that has become tolerated through necessity, is, in my opinion, the little white wood-louse before mentioned. It apparently has now lost the power of rolling itself into a ball, but when it first began to penetrate into the galleries ofFormica flava—our little yellow ant—it may very well have had it, and this would have rendered it impervious to attack, whilst its weight and round scaly surface would have made the task of removing it almost an impossible one. Thus, perforce, it stayed where itwished to stay, penetrating, perhaps, deeper and deeper into the labyrinth of galleries, as successive generations of cave animals have retreated farther and farther from the light of day, until at length, finding the wherewithal to live, it became wholly subterranean in its habits, lost the power of doing what it never required to do—namely, of rolling itself into a ball—and, through the absence of all sunlight, lost, too, its colouring matter, and became of its present dead, bleached white. Whether its eyesight, if it ever had any, is also gone, I do not know; but it can hardly, under present conditions, have any use for it, whereas its antennæ are constantly moving, and seem to be of extreme delicacy. I could never observe—for I have kept nests ofFormica flava—the smallest sign of any kind of relations between these wood-lice and their hosts; and if any scavenger work is done by the former, from which the latter derive benefit, I believe that this is merely incidental, and that the ants know nothing about it. But they have got accustomed to the wood-lice being there, and put up with them because they cannot help it.
It must be remembered, in regard toPaussidæ, that the family is represented by some two hundred species, all of which pass the greater part of their lives with ants. In regard to this Mr. Kirby remarks: “The observations made upon the family are so contradictory that the discrepancies can only be accounted for by supposing that different species have very different habits. Possibly some species may perform various useful services to the ants, while others are hostile; or they may be so usefulthat the ants are willing to pay toll of a certain number of their offspring, in return.”[11]
This last, however, does not seem very well to accord with recorded observations as to ants attacking any individualPaussuswhom they may chance to see devouring their larvæ, nor with the latter refusing to bombard, under these circumstances, even when in danger of their lives. It is impossible to imagine a hostilePaussusnot bombarding, in such a case, unless, indeed, we suppose it to have first lost its hostility, and then again to have become hostile, without, however, regaining the power of using its natural weapon. But this is a state of affairs hardly to be conceived.
We probably do not know the whole round of occupations which make up the life by day, of thePaussidæ; of their life by night, we know nothing at all. The nefarious raids upon the larvæ or eggs (for both are appreciated) of the ants can hardly be of frequent occurrence, or the partnership, one would think, must come to an end. Other ant-guests, however, including sometimes smaller members of their own family, are likewise preyed upon by these curious beetles, but very frequently, when observed, they seem to be asleep, nor do they appear then to be taken much notice of by the ants. Where or under what conditions their eggs are hatched, or what is the larval and pupal history of each species, we do not know, but only the perfect insect has as yet been found in any ants’ nest.
Other beetles that live with ants are either indifferent or hostile to them, but others, again, are kept and tendedin the same manner as are the aphides, and for a similar purpose. All or most of these secrete some sweet substance, which their hosts lick up, and, in return, offer them an asylum from all enemies, and are ready to give them their personal protection, should this be necessary. They go even further than this, and actually feed them as they do their own larvæ, with honey, or something of a similar nature, which they regurgitate from their crops. One little beetle—Atemelesby name—is extremely fond of such a meal, and solicits it from the ants by stopping in front of them and assuming a certain attitude, accompanied with insinuating motions of the antennæ. WhetherAtemelesis able to feed itself, or must live wholly upon these ministrations, I am not quite sure; but another beetle—poorClavigertestaceus—is, according to Janet, so entirely dependent upon the ants for subsistence that, if separated from them, he has nothing to do but to die.