CHAPTER XV
Ant wonders—Leaves cut for mushroom-growing—How ants plant mushrooms—A nest in a mushroom-bed—“Psychic plasticity”—Two opinions—Ant stupidity—Unfair comparisons—The ant and the servant-maid—Mushroom-growing beetles—Choked by ambrosia—Intelligent uselessness—Automatic phraseology—A curious insect.
ANTS, as everybody knows, have a special faculty for doing extraordinary things. Only a few of these have been mentioned in the last and preceding chapters, and only a few more can be touched upon in this. To do the subject anything like justice, a whole large book would be required, not a few chapters merely of a quite small one. What ants do, indeed, reminds me of the refrain, constantly repeated, of a certain old ballad lately brought to my notice, viz.—
“Wonders, notable wonders! never the like was heard.”
“Wonders, notable wonders! never the like was heard.”
“Wonders, notable wonders! never the like was heard.”
“Wonders, notable wonders! never the like was heard.”
For instance, they grow mushrooms (rice, or some cereals, they used to grow and reap, but lately they have not been allowed to); they use their own larvæ as an implement to sew or stick things together with, thus making little shuttles of them; they make bridges of their own bodies, by which they pass over rivers—even wide ones, it would seem, at least for them—which otherwise would be impassable; they allow themselves to bemade into honey-pots and kept full for the good of the general community, who take a little of them when they want it; they have cemeteries, and would appear even to feel something like awe or respect in the presence of their own dead; they cause certain plants to grow and come to maturity, which would otherwise die, in order to make a house in them, and so on and so on, many other wonders equally notable, to say nothing of those which have already been recounted.
To take the first on the list—I hardly believe in a classification of wonders—Belt, who was an engineer, but ought to have given up his whole life to observations of this sort, was the first, I believe, to find out that ants were mushroom-growers. Like others, when he came to Nicaragua he saw the leaf-cutting ants passing in long, double columns backwards and forwards between their nests and the trees, the homeward-bound column laden with their little crescent-shaped bits of green leaf, the outgoing one empty-handed. “The first acquaintance a stranger generally makes with them,” says Belt, “is on encountering their paths on the outskirts of the forest crowded with the ants; one lot carrying off the pieces of leaves, each piece about the size of a sixpence, and held up vertically between the jaws of the ant; another lot hurrying along in an opposite direction empty-handed, but eager to get loaded with their leafy burdens. If he follows this last division, it will lead him to some young trees or shrubs, up which the ants mount; and where each one, stationing itself on the edge of a leaf, commences to make a circular cut, with its scissor-likejaws, from the edge, its hinder feet being the centre on which it turns. When the piece is nearly cut off it is still stationed upon it, and it looks as though it would fall to the ground with it, but on being finally detached the ant is generally found to have hold of the leaf with one foot, and soon righting itself, and arranging its burden to its satisfaction, it sets off at once on its return. Following it again, it is seen to join a throng of others, each laden like itself, and, without a moment’s delay, it hurries along the well-worn path. As it proceeds, other paths, each thronged with busy workers, come in from the sides, until the main road often gets to be seven or eight inches broad, and more thronged than the streets of the city of London. Standing near the mounds, one sees from every point of the compass ant-paths leading to them, all thronged with the busy workers carrying their leafy burdens. As far as the eye can distinguish their tiny forms, troops upon troops of leaves are moving up towards the central point and disappearing down the numerous tunnelled passages. The outgoing empty-handed hosts are partly concealed amongst the bulky burdens of the incomers, and can only be distinguished by looking closely amongst them.”[60]
It used to be supposed that these leaves themselves, in a decaying state, were the food of the ants, whilst another theory was that they were used to make a sort of underground roof to the nest with. Belt’s discovery took everybody—including himself—completely by surprise. “I believe,” he says, “the real use they make of them is as a manure, on which grows a minute species of fungus, onwhich they feed: that they are in reality mushroom growers and eaters”;[60]and he thus narrates the circumstances which led him to this conclusion:—
“When I first began my warfare against the ants that attacked my garden, I dug down deeply into some of their nests. In our mining operations we also, on two occasions, carried our excavations from below up through very large formicariums, so that all their underground workings were exposed to observation. I found their nests below to consist of numerous rounded chambers, about as large as a man’s head, connected together by tunnelled passages leading from one chamber to another. Notwithstanding that many columns of the ants were continually carrying in the cut leaves, I could never find any quantity of these in the burrows, and it was evident that they were used up in some way immediately they were brought in. The chambers were always about three-parts filled with a speckled brown flocculent, spongy-looking mass of a light and loosely connected substance. This mass, which I have called the ant-food, proved on examination to be composed of minutely subdivided pieces of leaves, withered to a brown colour and overgrown and lightly connected together by a minute white fungus that ramified in every direction throughout it.”[60]Belt assured himself in many ways, but not through actually seeing them do so, that this fungus was what the ants fed on, and he adds, “that they do not eat the leaves themselves I convinced myself; for I found near the tenanted chambers deserted ones filled with the refuse particles of leaves that had been exhausted as manure for the fungus, and were now left,and served as food for larvæ ofStaphylinidæand other beetles.”[60]
Belt’s conclusions have been since amply verified, and the actual process of preparing the leaves and laying down the mushroom-beds, as well as the clipping and—if I mistake not—eating of the mushrooms, has been observed. Herr Möller—a German observer who resided for some years in tropical America—is usually referred to in this connection; but such extracts from his writings as I have come across are to me lessconvincingthan the following account of Mr. Edward Tanner, which is contained in theJournal of the Trinidad Field Club.[61]The observations were made with ants in confinement, as were Herr Möller’s also, I believe. “Each forager,” says Mr. Tanner, “drops her portion of leaf in the nest, which is taken up as required by the small workers, and carried to a clear space in the nest to be cleaned. This is done with their mandibles, and if considered too large, it is cut into smaller pieces. It is then taken in hand by the larger workers, who lick it with their tongues. Then comes the most important part, which is almost always done by the larger workers, who manipulate it between their mandibles, the ant using her palpi, tongue, three of her legs, and her antennæ while doing so. It now becomes a small, almost black ball, varying in size from a mustard-seed to the finest dust-shot, according to the size of the piece of leaf that has been manipulated, which varies from ⅛ by ⅛ to ¼ by ¼ of an inch. These balls, really pulp, are then built on to an edge of the fungus-bed by the larger workers, and are slightly smoothed down as the work proceeds.The new surface is then planted by the smaller workers with slips of the fungus brought from the older part of the nest. Each plant is planted separately, and they know exactly how far apart the plants should be. It sometimes looks as if the plants had been put in too scantily in places, yet in about forty hours, if the humidity is regulated, it is all evenly covered with a mantle as if of very fine snow. It is this fungus they eat, and with small portions of it the workers feed the larvæ.”
The statement herein contained that the ants plant the new portion of their mushroom-bed with slips or plants taken from the already growing fungus is, as far as I know, new. I do not remember it in Herr Möller’s paper,[62]who speaks of thehyphæof the fungus growing through and round the little leaf-balls within a few hours, but without reference to their being planted, nor is it alluded to by Professor Wheeler, who has studied the mushroom-growing ant—whether the same or a similar species I know not—in Texas. Forel, again, speaking of an allied form in Colombia, says, “The largest workers triturate the leaves”; and again, “the medium-sized workers of the minim caste are for ever clipping the threads of the fungus, which then develops the ‘Kohlrabi’ (the little round swellings, that is to say), on which the ants feed.”[62]Possibly this last may allude to the planting, but if so, it is the reverse of clearly put. Professor Wheeler also alludes to this constant clipping of the fungus, and sees in it the probable cause of the mutilationof the antennæ of the little blind cockroaches that live with these ants and take toll of their mushrooms.[63]But as these constitute the sole food of their insect cultivators, it is natural that the latter should frequently clip in order to eat them, and the clipping would, no doubt, stimulate their growth. All this, however, is different from the actual deliberate planting of the fungus on newly laid-down portions of the bed—an act which would imply a very clear intention, and make the ants farmers in the same way that we are. This, however, need not be the case if they only lay down the beds, for these at one time probably constituted their actual food, the crop of fungus being merely incidental. But if the ants deliberately plant the fungus, then, indeed, they must know precisely, in a human way, what they are about.
As we have seen, the leaves, from which, in their state of pulp, the mushrooms spring, are stored up by the ants in large underground chambers; but these mushroom-beds, or gardens, as they are often called, are themselves a sort of nest, containing tunnels and chambers, and not merely unformed heaps. It is in one or other of these chambers that the queen ant of the nest resides, a majestic creature, almost an inch long, but inflated both with pride and eggs to a disproportionate extent. Her sons and virgin daughters, who will some day be queens themselves, keep her company, whilst all about in the galleries and all over the broad, flat surface of the garden, which resembles a large flattened sponge, walk the different castes of workers, some large, some small, some medium-sized, with a few big-headed soldiers here and thereamongst them, as though to keep the crowd in order. Whether they have really any such duty assigned them we do not know, but they do not appear to do any work, whilst the others are all busy at something, and the smaller workers particularly keep threading the stalks and filaments of the fungus in order to weed out any extraneous useless growth from amongst it.[63]
It is a sad reflection—thus sighs Professor Wheeler—that so much ordered energy, such apparent intelligence, should all be really due to—whathe does not seem to be quite certain about, not automatism entirely perhaps, but if not, then semi- or demi-semi-automatism, tempered with “psychic plasticity.” Against this view of the matter we have that of Belt, who, after giving two instances, which came under his own observation, of intelligent adaptation, on the part of ants, to meet particular circumstances, exclaims, “Can it be contended that such insects are not able to determine by reasoning powers which is the best way of doing a thing, or that their actions are not guided by thought and reflection?”[64]But then Belt was not provided with the term “psychic plasticity,” and without it he could only infer intelligence from any intelligent act.
Still it cannot be denied that a great many instances have been given—noticeably in the case of “ourants” by Sir John Lubbock[65]—in which these paragons of insects have behaved very stupidly, or shall we say—for why should a creature that cannot be intelligent be stupid either?—with great “psychicrigidity”? Certainly such contradictions are very puzzling, but I would suggest oneway of trying to estimate better the rigid type of ant intellect, which I believe to be absolutely new, and that is to compare it not with one’s own brain—or Darwin’s—but with that of a rigid type of person. It is wonderful what a difference this might make in our conclusions. An ant, for instance, that is unable, under some special circumstances, to get a thing down into its nest, because it persists in holding or pulling it, in the way it has always been accustomed to, or another that would rather be blown into the water along a known road than leave it for a new one, makes a poor figure in presence of the seven sages, or amidst a circle of senior wranglers mentally called up for its confusion; but we should think, rather, of some pin-headed servant-maid, setting an article of furniture each morning in the place that, with evident intention, you have removed it from overnight, or making up a larger and larger fire as the weather gets warmer and warmer. One should think of the obstinacy with which many people cling to old habits which changed times have made useless, or even harmful, and of how numbers not only prefer inferior things they are used to, to the most decisive improvements, but hate and revile such improvements as though they were undeniable evils. Instances will occur to everyone. I would rather not mention any for fear of alienating nine out of every ten of my readers. We should think, also, of savages or primitive, slow-moving peoples. What a great unadaptability, for instance, did the Matabele show in their methods of encountering our countrymen during the war, and throughout the rising; as also in that rising itself, since it was against allthose well-known blessings which our empire confers upon savages.[66]It is to these less exalted levels of human faculty that we should look when we seek to compare an ant’s mind—when out of its usual set track—with our own, if we wish to do the ant any justice. That we pursue an opposite plan is my own explanation of many a partial verdict. To every experimenter in these directions (who should happen to ask my advice) I would say, first, “Do you know, or have you ever known, a really silly person?” and on his beginning, at once, with “Yes, Mrs.” or “Miss” (as the case may be), I would strike in peremptorily thus: “Then keepher—not Newton—in your mind as a standard of comparison.”
That ants should intentionally cultivate mushrooms will appear wonderful to everybody, and some will see in it the high-water mark of their mental development, by whatever path it has been arrived at. It seems natural to connect such doings with the fact that “in ants the cerebral ganglia are of extraordinary dimensions, and in all the Hymenoptera these ganglia are many times larger than in the less intelligent orders, such as beetles.”[67]Yet the brain of an ant—“one of the most marvellous atoms of matter in the world, perhaps more so than the brain of a man”—is “not so large as the quarter of a small pin’s head.”[67]Of what size, then, can a beetle’s be?—especially that family of beetles which grow and cultivate mushrooms, just in the same way that ants do. It would be suggestive—though I hardly know of what—should itbe found that, comparatively speaking,theyhave no brain at all.
The beetles alluded to have been named, with reference to the particular kind of mushrooms they grow, ambrosia beetles, though in what the great superiority of these over those raised by the ants lies I do not know, for no one appears to have tasted them. It has been agreed, however, to call them ambrosia. “One of the most remarkable facts,” says Mr. Froggatt, “is that each group of these beetles is associated with a certain kind of ambrosia or fungus, notwithstanding that they are found in different timbers. This substance is actually cultivated by the mother beetle upon a carefully prepared layer or bed of wood-débris, generally at the end of the gallery; but in others the ambrosia is grown only in certain brood chambers of peculiar construction, whilst in others again it is propagated in beds near the cradles of the larvæ!”[68]When the latter hatch, they find a supply of celestial food awaiting them, and can walk about the various galleries, feeding upon it to their hearts’ content.
In other cases, however—that is to say, with other species—social development has gone further, and, besides boring galleries, the mother-beetle excavates a number of cells in their walls, like rows of bedrooms opening out of either side of a passage. She does not, however, quite finish her bedrooms, but, whilst they are still incomplete, lays an egg in each, and when this hatches, the young beetle, then in its larval state, takes up the task where she left off, and in time completes it. All the while they aregrowing up the mother feeds the young ones, and, between the intervals of doing so, stops up the entrance to the cell with a “plug”—such is the word employed; “to what base uses we may return, Horatio!”—of ambrosia. In time, when they have acquired the full imago form, each female beetle flies away to make a burrow and rear a family of her own, and in some species she is accompanied in this marriage flight, as it may be called, by the male. In others, however, the males are wingless, and remain in the burrow, till, when their appointed time comes, they die. Whether the male, when winged, assists the female in her mining operations I am not quite sure, inasmuch as that point seems to be avoided in the accounts which I have been able to consult, but the wingless male would not be able to do so, as he would be left behind in the burrow when the female flew away to found another colony.
The fungus, when it has once commenced to grow, increases very rapidly, so that if the number of beetles in the nest is much diminished, as, say, by some accident, the rest cannot eat enough to keep it down, and so, it would appear, are suffocated. It is asserted, however, that when the wingless males are deserted by the females, and would otherwise perish in this way, they all collect together in a few of the galleries and feast on the ambrosia there growing. By this means, we are told, they “prolong for a time their useless existence”—an ungrateful way of putting it, so it seems to me, as the poor things have already been useful in a very indispensable manner, so that their existence as a whole is anything butuseless, and to separate a part of it from the rest and carp at that is silly as well as ill-natured. But it is the fashion to speak in this harsh way of the male insect, beginning with the drone bee; whereas when the female has done all thatshecan do—which is often just to lay her eggs—nobody talks ofheruseless existence. Fashion is a curious thing, and ants, even if they be automatons, are not the only creatures that do things automatically.
It is certainly very curious, if it be true, that the wingless male beetles should, by thus congregating together in this way, and so saving their lives, show more intelligence than the winged females, who, under similar circumstances, are choked with their ambrosia, as the Duke of Clarence was with his nectar in a malmsey-butt. It is true that with the males the thing happens every year, whereas with the females it is only accidental; but, in the particular circumstances, it is difficult to see how inheritance can have had anything to do with it. Here, then, are a particular family of beetles who live the same sort of social life that ants and bees do, which discovery appears to have been made by a Mr. Hubbard not so many years ago, and from whose paper on the subject all the above particulars have been taken, though only through the medium of various magazines, since even at the British Museum I was unable to get the paper itself. So long ago, however, as 1844 a certain Herr Theo Hartig “published an article on the ambrosia ofXyleborno (Bostrichus) dispar, in which he showed that it was a fungus growth (pilzrasen), and he named the fungusMonilia candida.” This statement is made by Mr.Hubbard in his much more recent account. Not feeling perfectly certain from it whether the origin, as well as the nature, of the strange-named substance was not also divined by the German investigator, I quote the reference in order not to do him a possible injustice, for to me it seems that there have been few more interesting discoveries than this of these ant-like, ambrosia-growing beetles. But why the ants only grow mushrooms, thus allowing themselves to be enormously outdone by an inferior insect, is more than I can understand.
And now a word of justice to these beetles. It might be supposed that, by burrowing into trees, they caused the death of the latter, but this is not really the case. Writing inThe Agricultural Gazetteof New South Wales for August, 1900, Mr. Froggatt, the Government Entomologist, makes the following statement absolvingXleborus: “This curious little beetle (X. solidus) is rather plentiful about Sydney, and is frequently sent to us taken out of the trunks of fruit trees, which it is supposed to have killed; but in all cases that have come under my notice it has had nothing to do with the tree dying, but is attracted to the tree as soon as it becomes sick, the bark begins to wither, and the first symptoms of decay set in.” Mr. Froggatt adds: “The instinct that leads these and other wood-boring beetles to a tree as soon as it is sick is something marvellous; in the tropics I have collected many fine, rare species upon the freshly cut tent-poles in our camp, attracted to the wood, but otherwise seldom found in the bush.” This instinct would seem to be a remarkably developed scent, though why a severed branch shouldsmell differently from the tree of which it but a moment before made a part it is not easy to imagine. However, we cannot, without evidence, attribute clairvoyance to beetles, and perhaps it is the cut from which the scent emanates.
Another example of an insect which is neither an ant, bee, wasp, nor white ant, but which yet may be said to live a true social life, is the little creature which, under the name ofPsocus venosusand as belonging to the orderCarrodentia, will be familiar to everyone. It is nearly related to the so-called book-lice, but lives in the open air, “being seen,” says Mr. Leland Howard, “upon the trunks of trees, in flocks numbering from twelve to forty or fifty individuals.”[69]These browse together like a herd of miniature cattle on the various lichens that embrace the bark, and these they nibble so closely that wherever they move they leave a bare track behind them. Sometimes one family and sometimes several are included in the herd, all ages and stages being represented, from the wingless but free-moving larvæ to the winged imago form. The latter, however, though they be thus provided, will not readily forsake their young, but the whole of them, when alarmed, first run all together, and then, if the cause of disquietude continue, suddenly scatter as though in panic, and run hither and thither, in all and every direction. When the danger seems over, they close up their ranks again, and go on browsing as before.
The femalePsocuslays her eggs in little clusters of from fifteen to twenty, and protects each cluster under a sort of dome or shield of gnawed wood which she pressesupon them so that they stick to it. She is said to brood over the eggs, but this does not appear to mean that she actually incubates them. Rather, she remains about, keeping watchful guard till they are hatched, and then takes the young to find pasture, walking at their head like a hen in front of her chickens. From such beginnings as these it seems possible that the social life of ants has been, in the course of ages, evolved and developed.