by Grant Allen
No. 9 is a back view of the same head, with the various jaws and mouthpieces expanded. It shows very well the complicated nature of the tongue, the palps, the shield, and so forth, and also the powerful nipping jaws, with their closely serrated and tooth-like edge — these last being the weapons used in battle and in repelling the attacks of large enemies. It also excellently exhibits the complex arrangement of the beautiful jointed antennæ. The black spot in the centre of the head above is the cut neck, or esophagus. I advise you to look closely at the mouth-organs in this microscopic drawing, and to compare them with the corresponding parts in the wasp, illustrated by Mr. Enock in the last chapter.
Considering how important the antennæ are, it will not surprise you to learn that the clean little ants have a special instrument, like the bees and wasps, for keeping these useful outgrowths in proper order. The singular brush-and-comb with which they clean them is shown in No. 10, together with a smaller representation of the entire leg on which it exists, so as to enable you to see where the ant carries it. Ants, indeed, are as fond of washing themselves as cats; and when any accident happens to one, such as getting smeared with honey, you will see the little creature carefully getting rid of the foreign body with her hairy legs, and paying particular attention to her precious antennæ. The mere existence of such developed brushes is sufficient to prove the immense importance of the organs they clean to the bee-and-ant order.
The life-history of an ant falls into four periods or ages: the egg, the grub, the pupa, and the perfect insect. The eggs, which are very tiny, are white or yellowish, and somewhat elongated; those observed by Sir John Lubbock, the great authority on ants, have taken a month or six weeks to hatch. The larvæ, like the young of bees and wasps, are white, legless grubs, narrow towards the head. The picture in No. 2, indeed, only imperfectly suggests the constant care with which they are tended by the nurses in early life; for they are carried about from room to room at different times, apparently to secure the exactly proper degree of warmth or moisture; and they are also often assorted in a sliding-scale of ages. “It is sometimes very curious to see them in my nests,” says Sir John Lubbock, “arranged in groups according to size, so that they remind one of a school divided into five or six classes.” After a longer or shorter period of grubhood, which differs in length in different species, they turn into pupæ, either in a cocoon or naked. It takes the insects three or four weeks, in the pupa form, to develop into full-grown ants; and even when they have finished, they are as helpless as babies, and could not escape from the cocoon but for the kind offices of the worker attendants. “It is pretty to see the older ants helping them to extricate themselves, carefully unfolding the legs and smoothing out the wings” of the males and females, “with truly feminine tenderness and delicacy.” This utter helplessness of the young ant is very interesting for comparison with the case of man; for it is now known that nothing conduces to the final intellectual and moral supremacy of a race so much as the need for tending and carefully guarding the young; the more complete the dependence of the offspring upon their elders, the finer and higher the ultimate development.
Ants are likewise great domesticators of various other animals; indeed, as I have said before, they keep many more kinds of flocks and herds in confinement than we ourselves do. There is a funny little pallid creature, called Beckia, an active, bustling small thing, remotely resembling a minute earwig-larva, which runs in and out among the ants in great numbers, keeping its antennæ always in a state of perpetual vibration. The nests also harbour a queer, armour-plated white wood-louse, whose long Latin-German name I mercifully spare you; and this strange beast toddles about quite familiarly among the ants in the galleries. Both kinds must have been developed in ants’ nests from darker animals; and both are blind, from long residence in the dark underground tunnels which they never quit; their lightness of colour and the disappearance of their eyes tend alike to show that they and their ancestors have resided for countless ages in the homes of the ants. Yet no ant ever seems to take the slightest notice of them. Still, there they are, and the ants tolerate their presence; while an unauthorised interloper, as Sir John Lubbock remarks, would at once be set upon and killed. The accomplished entomologist in question suggests that they may perhaps act as scavengers, like the wild dogs of Constantinople or the turkey-buzzard vultures of the West Indies and South America. I have sometimes almost been inclined to suspect, myself, that they may be kept as totems, much as human savages domesticate one of their revered ancestral animals as an object of worship.
In other cases the relation between the ants and their domesticated animals is more distinctly economical. For instance, there is a blind beetle — most ant-cattle are blind from long residence in the tunnels — which has actually lost the power of feeding itself; but the ants feed it with their own food, and then caress it with their antennæ, apparently in order to make it give forth some pleasant secretion. This secretion seems to be poured out by a tuft of hairs at the base of the beetle’s hard wing-cases; these tufts of hair the ants take into their mouths and lick all over with the greatest relish. Some ant tribes even strike up an alliance with other ants of a different species, whose nest they frequent and whom they follow in all their wanderings. Thus, there is a very tiny yellow ant, known as Stenamma, which takes up its abode in the galleries of the much larger Horse Ants and Field Ants. When these big friends change their quarters to a new nest, as frequently happens, the tiny Stenammas accompany them, “running about among them,” says Sir John Lubbock, “and between their legs, tapping them inquisitively with their antennæ, and even sometimes climbing on to their backs, as if for a ride, while the large ants seem to take little notice of them. They almost seem to be the dogs, or perhaps the cats, of the ants.” In yet another case, a wee parasitic kind makes its own small tunnels in and out among those of a much larger species, members of which cannot get at the petty robbers, because they are themselves too big to enter the minute galleries. The depredators are, therefore, quite safe, and make incursions into the nests of their bigger victims, whose larvæ they carry off and devour— “as if we had small dwarfs, about eighteen inches long, harbouring in the walls of our houses, and every now and then carrying off some of our children into their horrid dens.”
When once one begins upon these fascinating insects, the difficulty is to know when to stop. But I have said enough, I hope, to suggest to you the extraordinary interest of the study of ant life. Even if observed in the most amateurish way, it affords one opportunities for endless amusing glimpses into the politics of a community full of comic episodes and tragic dénouements.
IX. A FROZEN WORLD
THE pond in the valley is a world by itself. So far as its inhabitants are concerned, indeed, it is the whole of the world. For a pond without an outlet is like an oceanic island; it is a system, a microcosm, a tiny society apart, shut off by impassable barriers from all else around it. As the sea severs Fiji or St. Helena from the great land-surface of the continents, so, and just as truly, the fields about this pond sever it from all other inhabited waters. The snails and roach and beetles that dwell in it know of no other world; to them, the pond is all; the shore that bounds it is the world’s end; their own little patch of stagnant water is the universe.
A pond which empties itself into a river by means of a stream or brook is not quite so isolated. It has points of contact with the outer earth: it resembles rather a peninsula than an island: it is the analogue of Spain or Greece, not of Hawaii or Madeira. And you will see how important this distinction is if you remember that trout and stickleback and stone-loach and fresh-water mussels can ascend the river into the brook, and pass by the brook into the pond, which has thus a direct line of communication with all waters elsewhere, including even the great oceans. But the pond without an outlet cannot thus be peopled. Whatever inhabitants it possesses have come to it much more by pure chance. They are not able to walk overland from one pond to another; they must be brought there somehow, by insign
ificant accidents. Regarded in this light, the original peopling of every pond in England is a problem in itself — a problem analogous in its own petty way to the problem of the peopling of oceanic islands.
That great and accomplished and ingenious naturalist, Mr. Alfred Russel Wallace, working in part upon lines long since laid down by Darwin, has shown us in detail how oceanic islands have in each case come to be peopled. He has shown us how they never contain any large indigenous land animals belonging to the great group of mammals — any deer or elephants or pigs or horses; because mammals, being born alive, cannot, of course, be transported in the egg, and because the adult beasts could seldom be carried across great stretches of ocean by accident without perishing on the way of cold, hunger, or drowning. One can hardly imagine an antelope or a buffalo conveyed safely over sea by natural causes from Africa to the Cape Verdes, or from America to the Bermudas. As a matter of fact, therefore, the natural population of oceanic islands (for I need hardly say I set aside mere human agencies) consists almost entirely of birds blown across from the nearest continent, and their descendants; of reptiles, whose small eggs can be transported in logs of wood or broken trees by ocean currents; of snails and insects, whose still tinier spawn can be conveyed for long distances by a thousand chances; and of such trees, herbs, or ferns as have very light seeds or spores, easily whirled by storms (like thistledown), or else nuts or hard fruits which may be wafted by sea-streams without damage to the embryo. For the most part, also, the plants and animals of oceanic islands resemble more or less closely (with locally induced differences) those of the nearest continent, or those of the land from which the prevailing winds blow towards them, or those of the country whence currents run most direct to the particular island. They are waifs and strays, stranded there by accident, and often giving rise in process of time to special local varieties or species.
Now, it is much the same with isolated ponds. They acquire their first inhabitants by a series of small accidents. Perhaps some water-bird from a neighbouring lake or river alights on the sticky mud of the bank, and brings casually on his webbed feet a few clinging eggs of dace or chub, a few fragments of the spawn of pond-snails or water-beetles. Paddling about on the brink, he rubs these off by mere chance on the mud, where they hatch in time into the first colonists of the new water-world. Perhaps, again, a heron drops a half-eaten fish into the water — a fish which is dead itself, but has adhering to its scales or gills a few small fresh-water crustaceans and mollusks. Perhaps a flood brings a minnow or two and a weed or two from a neighbouring stream; perhaps a wandering frog trails a seed on his feet from one pool to another. By a series of such accidents, each trivial in itself, an isolated pond acquires its inhabitants; and you will therefore often find two ponds close beside one another (but not connected by a stream), the plants and animals of which are nevertheless quite different.
Now, the pond in summer is one thing; the pond in winter is quite another. For just reflect what winter means to this little, isolated, self-contained community! The surface freezes over, and life in the mimic lake is all but suspended. Not an animal in it can rise to the top to breathe; not a particle of fresh oxygen can penetrate to the bottom. Under such circumstances, when you come to think of it, you might almost suppose life in the pond must cease altogether. But nature knows better. With her infinite cleverness, her infinite variety of resource, of adaptation to circumstances, she has invented a series of extraordinary devices for allowing all the plants and animals of a pond to retire in late autumn to its unfrozen depths, and there live a dormant existence till summer comes again. Taking them in the mass, we may say that the population sink down to the bottom in November or December, and surge up again in spring, though in most varied fashions.
Consider, once more, the curious set of circumstances which renders this singular plan feasible. Water freezes at 32 degrees Fahrenheit. For the most part, under normal conditions, the water at the top of the pond is the warmest, and that at the bottom coldest; for the hot water, being expanded and lighter, rises to the surface, while the cold water, being contracted and heavier, sinks to the depths. If this relation remained unchanged throughout, when winter came, the coldest water would gradually congeal at the bottom of the pool: and so in time the whole pond would freeze solid. In that case, life in it would obviously be as impossible as in the ice of the frozen pole or in the glaciers of the Alps. But by a singular variation, just before water freezes, it begins to expand again, so that ice is lighter than water. Thus the ice as it forms rises to the surface, and leaves at the bottom a layer of slightly warmer water, some four or five degrees above freezing point. It is usual to point this fact out as a beautiful instance of special provision on the part of nature for the plants and animals which live in the ponds; but to do so, I think, is to go just a step beyond our evidence. Nature does not fit all places alike for the development of life; she does not fit the desert, for example, nor the interior of glaciers or frozen oceans, nor, for the matter of that, the rocks of the earth’s mass; nor does she try to fit living beings for such impossible situations. All we are really entitled to say is this — that the conditions for life do occur in ponds, owing to this habit of water, and that therefore special plants and animals have been adapted by nature to fulfil them.
The devices by which such plants and animals get over the difficulties of the situation, however, are sufficiently remarkable to satisfy the most exacting. Recollect that for some weeks together the entire pond may be frozen over, and that during that dreary time all animal or vegetable life at its surface must be inevitably destroyed. For hardly a plant or an animal can survive the actual freezing of its tissues. Nevertheless, as soon as winter sets in, the creatures which inhabit the pond feel the cold coming, and begin to govern themselves accordingly. A few, which are amphibious, migrate, it is true, to more comfortable quarters. Among these are the smaller newts or efts, which crawl ashore, and take refuge from the frost in crannies of rocks or walls, or in cool damp cellars. Most of the inhabitants of the pool, however, remain, and retire for warmth and safety to the depths. Even the amphibious frogs themselves, which have hopped ashore on their stout legs in spring, when they first emerged from their tadpole condition, now return for security to their native pond, bury themselves comfortably in the mud in the depths, and sleep in social clusters through the frozen season. They are not long enough and lithe enough to creep into crannies above ground like the newts; and with their soft smooth skins and unprotected bodies they would almost inevitably be frozen to death if they remained in the open. On the bottom of the pond, however, they huddle close and keep one another warm, so that portions of the mud in the centre of the pool consist almost of a living mass of frogs and other drowsy animals.
Some of the larger pond-dwellers thus hibernate in their own persons; others, which are annuals, so to speak, die off themselves at the approach of winter, and leave only their eggs to vouch for them and to continue the race on the return of summer. A few beetles and other insects split the difference by hibernating in the pupa or chrysalis condition, when they would have to sleep in any case, and emerging as full-fledged winged forms at the end of the winter. But on the whole the commonest way is for the plant or animal itself in its adult shape to lurk in the warm mud of the bottom during the cold season.
In No. 1 we have an excellent illustration of this most frequent type, in the person of the beautiful pointed pond-snail, a common fresh-water mollusk, with a shell so daintily pretty that if it did not abound we would prize it for its delicate transparent amber hue and its graceful tapering form, resembling that of the loveliest exotics. This pond-snail, though it lives in the water, is an air-breather, and therefore it hangs habitually on the surface of the pool, opening its lung-sac every now and then to take in a fresh gulp of air, and looking oddly upside down as it floats, shell downward, in its normal position. It browses at times on the submerged weeds in the pond; but it has to come to the surface at frequent intervals to breathe; though, in co
mmon with most aquatic air-breathers, it can go a long time without a new store of oxygen, like a man when he dives, or a duck or swan when it feeds on the bottom — of course to a much greater degree, because the snail is cold-blooded; that is to say, in other words, needs much less aëration. On a still evening in summer you will often find the surface of the pond covered by dozens of these pretty shells, each with its slimy animal protruded, and each drinking in air at the top by its open-mouthed lung-sac.
In winter, however, as you see in No. 2, our pond-snail retires to the mud at the bottom, and there quietly sleeps away the cold season. Being a cold-blooded gentleman, he hibernates easily, and his snug nest in the ooze, where he buries himself two or three inches deep, leaves him relatively little exposed to the attacks of enemies. Indeed, since the whole pond is then sleeping and hibernating together, there is small risk of assault till spring comes round again.
