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Didelphys azarae and young.
tively much greater than in that of the female bat: but then the opossum never quitted its hold on the tree, and it also supplemented its hand-like feet, furnished with crooked claws, with its teeth and long prehensile tail. The poor bat had to seek its living in the empty air, pursuing its prey with the swiftness of a swallow, and it seemed
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wonderful to me that she should have been able to carry about that great burden with her one pair of wings, and withal to be active enough to supply herself and her young with food.
In the end I released her, and saw her fly away and disappear among the trees, after which I put back the two young bats in the place I had taken them from, among the thick-clustering foliage of a small acacia tree. When set free they began to work their way upwards through the leaves and slender twigs in the most adroit manner, catching a twig with their teeth, then embracing a whole cluster of leaves with their wings, just as a person would take up a quantity of loose clothes and hold them tight by pressing them against the chest. The body would then emerge above the clasped leaves, and a higher twig would be caught by the teeth; and so on successively, until they had got as high as they wished, when they proceeded to hook themselves to a twig and assume the inverted position side by side; after which, one drew in its head and went to sleep, while the other began licking the end of its wing, where my finger and thumb had pressed the delicate membrane. Later in the day I attempted to feed them with small insects, but they rejected my friendly attentions in the most unmistakable manner, snapping viciously at me every time I approached them. In the evening, I stationed myself close to the tree, and presently had the satisfaction of seeing the mother return, flying straight to the spot where I had taken her, and in a few moments she was away again and over the trees with her twins.
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Assuming that these two young bats had, before I found them, existed like parasites clinging to the parent, their adroit actions when liberated, and their angry demonstrations at my approach, were very astonishing; for in all other mammals born in a perfectly helpless state, like rodents, weasels, edentates, and even marsupials, the instincts of self-preservation are gradually developed after the period of activity begins, when the mother leads them out, and they play with her and Avith each other. In the bat the instincts must ripen to perfection without exercise or training, and while the animal exists as passively as a fruit on its stem.
I have observed that the helpless young of some of the mammals I have just mentioned seem at first to have no instinctive understanding of the language of alarm and fear in the parent, as all young-birds have, even before their eyes are open. Nor is it necessary that they should have such an instinct, since, in most cases, they are well concealed in kennels or other safe places; but when, through some accident, they are exposed, the want of such an instinct makes the task of protecting them doubly hard for the parent. I once surprised a weasel (Galictis barbara) in the act of removing her young, or conducting them, rather; and when she was forced to quit them, although still keeping close by, and uttering the most piercing cries of anger and solicitude, the young continued piteously crying out in their shrill voices and moving about in circles, without making the slightest attempt to escape, or to conceal themselves, as young birds do.
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Some field mice breed on the surface of the ground in ill-constructed nests, and their young are certainly the most helpless things in nature. It is possible that where this dangerous habit exists, the parent has some admirable complex instincts to safeguard her young, in addition to the ordinary instincts of most animals of this kind. This idea was suggested to me by the action of a female mouse which I witnessed by chance. While walking in a field of stubble one day in autumn, near Buenos Ayres, I suddenly heard, issuing from near my feet, a chorus of shrill squealing voices--the familiar excessively sharp little needles of sound emitted by young, blind and naked mice, when they are disturbed or in pain. Looking down, I saw close to my foot a nest of them--there were nine in all, wriggling about and squealing; for the parent, frightened at my step, had just sprung from them, overturning in her hurry to escape the slight loosely-felted dome of fine grass and thistledown which had covered them. I saw her running away, but after going six or seven yards she stopped, and, turning partly round so as to watch me, waited in fear and trembling. I remained perfectly motionless--a sure way to allay fear and suspicion in any wild creature,--and in a few moments she returned, but with the utmost caution, frequently pausing to start and tremble, and masking her approach with corn stumps and little inequalities in the surface of the ground, until, reaching the nest, she took one of the young in her mouth, and ran rapidly away to a distance of eight or nine yards and concealed it in a tuft of dry grass.
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Leaving it, she returned a second time, in the same cautious manner, and taking another, ran with it to the same spot, and concealed it along with the first. It was curious that the first young mouse had continued squealing after being hidden by the mother, for I could hear it distinctly, the air being very still, but when the second mouse had been placed with it, the squealing ceased. A third time the old mouse came, and then instead of going to the same spot, as I had expected, she ran off in an opposite direction and disappeared among the dry weeds; a fourth was carried to the same place as the third; and in this way they were all removed to a distance of some yards from the nest, and placed in couples, until the last and odd one remained. In due time she came for it, and ran away with it in a new direction, and was soon out of sight; and although I waited fully ten minutes, she did not return; nor could I afterwards find any of the young mice when I looked for them, or even hear them squeal.
I have frequently observed newly-born lambs on the pampas, and have never failed to be surprised at the extreme imbecility they display in their actions; although this may be due partly to inherited degeneracy caused by domestication. This imbecile condition continues for two, sometimes for three days, during which time the lamb apparently acts purely from instincts, which are far from perfect; but after that, experience and its dam teach it a better way. When born its first impulse is to struggle up on to its feet; its second
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to suck, but here it does not discriminate like the newly-hatched bird that picks up its proper food, or it does not know what to suck. It will take into its mouth whatever comes near, in most cases a tuft of wool on its dam's neck; and at this it will continue sucking for an indefinite time. It is highly probable that the strong-smelling secretion of the sheep's udder attracts the lamb at length to that part; and that without something of the kind to guide it, in many cases it would actually starve without finding the teats. I have often seen lambs many hours after birth still confining their attention to the most accessible locks of wool on the neck or fore legs of the dams, and believe that in such cases the long time it took them to find the source of nourishment arose from a defective sense of smell. Its next important instinct, which comes into play from the moment it can stand on its feet, impels it to follow after any object receding from it, and, on the other hand, to run from anything approaching it. If the dam turns round and approaches it from even a very short distance, it will start back and run from her in fear, and will not understand her voice when she bleats to it: at the same time it will confidently follow after a man, dog, horse, or any other animal moving from it. A very common experience on the pampas, in the sheep-country, is to see a lamb start up from sleep and follow the rider, running along close to the heels of the horse. This is distressing to a merciful man, tor he cannot shake the little simpleton off, and if he rides on, no matter how fast, it will keep up him, or keep him in sight, for half a mile or a
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mile, and never recover its dam. The gaucho, who is not merciful, frequently saves himself all trouble and delay by knocking it senseless with a blow of his whip-handle, and without checking his horse. I have seen a lamb, about two days old, start up from sleep, and immediately start off in pursuit of a puff ball about as big as a man's head, carried past it over the smooth turf by the wind, and chase it for a distance of five hundred yards, until the dry ball was brought to a stop by a tuft of coarse grass. This blundering instiuct is quickly laid aside when the lamb has learned to distinguish its dam from other objects, and its dam's voice from other sounds. When four or five days old it will start from sleep, but instead of rushing blindly away after any receding object, it first looks about it, and will then recognize and run to its dam.
I have often been struck with the superiority of the pampa or creolla--the old native breed of sheep--in the greater vigour of the young when born over the improved European varieties. The pampa descends to us from the first sheep introduced into La Plata about three centuries ago, and is a tall, gaunt bony animal, with lean dry flesh, like venison, and long straight wool, like goats' hair. In their struggle for existence in a country subject to sudden great changes of temperature, to drought, and failure of grass, they have in a great measure lost the qualities which make the sheep valuable to man as a food and wool-producing animal; but on the other hand they have to some extent recovered the vigour of a wild animal, being hardy enough to exist without any shelter, and requiring from their
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master man only protection from the larger carnivores. They are keen-scented, swift of foot and Wonderfully active, and thrive where other breeds would quickly starve. I have often seen a lamb dropped on the frosty ground in bitterly cold windy weather in midwinter, and in less than five seconds struggle to its feet, and seem as vigorous as any day-old lamb of other breeds. The dam, impatient
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Pampa sheep.
at the short delay, and not waiting to give it suck, has then started off at a brisk trot after the flock, scattered and galloping before the wind like huanacos rather than sheep, with the lamb, scarcely a minute in the world, running freely at her side. Notwithstanding its great vigour it has been proved that the pampa sheep has not so far outgrown the domestic taint as to be able to maintain its own existence when left entirely to itself. During the
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first half of this century, when cattle-breeding began to be profitable, and wool was not worth the trouble of shearing, and the gaucho workman would not eat mutton when beef was to be had, some of the estancieros on the southern pampas determined to get rid of their sheep, which were of no value to them; and many flocks were driven a distance out and lost in the wilds. Out of many thousands thus turned loose to shift for themselves, not one pair survived to propagate a new race of feral sheep; in a short time pumas, wild dogs, and other beasts of prey, had destroyed them all. The sterling qualities of the pampa sheep had their value in other times; at present the improved kinds are alone considered worth having, and the original sheep of the country is now rapidly disappearing, though still found in remote and poor districts, especially in the province of Cordova; and probably before long it will become extinct, together with the curious pug-nosed cow of the pampas.
I have had frequent opportunities of observing the young, from one to three days old, of the Cervus campestris--the common deer of the pampas, and the perfection of its instincts at that tender age seem very wonderful in a ruminant. When the doe with, fawn is approached by a horseman, even when accompanied with dogs, she stands perfectly motionless, gazing fixedly at the enemy, the fawn motionless at her side; and suddenly, as if at a preconcerted signal, the fawn rushes directly away from her at its utmost speed; and going to a distance of six hundred to a thousand yards conceals
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itself in a hollow in the ground or among the long grass, lying down very close with neck stretched out horizontally, and will thus remain until sought by the dam. When very young if found in its hiding-place it will allow itself to be taken, making no further effort to escape. After the fawn has run away the doe still maintains her statuesque attitude, as if resolved to await the onset, and only when the dogs are close to her she also rushes away, but invariably in a direction as nearly opposite to that taken by the fawn as possible. At first she runs slowly, with a limping gait, and frequently pausing, as if to entice her enemies on, like a partridge, duck or plover when driven from its young; but as they begin to press her more closely her speed increases, becoming greater the further she succeeds in leading them from the starting-point.
The alarm-cry of this deer is a peculiar whistling bark, a low but far-reaching sound; but when approaching a doe with young I have never been able to hear it, nor have I seen any movement on the part of the doe. Yet it is clear that in some mysterious way she inspires the fawn with sudden violent fear; while the fawn, on its side, instead of being affected like the young in other mammals, and sticking closer to its mother, acts in a contrary way, and runs from her.
Of the birds I am acquainted with, the beautiful jacana (Parra jacana) appears to come into the world with its faculties and powers in the most advanced state. It is, in fact, ready to begin active
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life from the very moment of leaving the shell, as I once accidentally observed. I found a nest on a small mound of earth in a shallow lagoon, containing four eggs, with the shells already chipped by the birds in them. Two yards from the small nest mound there was a second mound covered with coarse grass. I got off my horse to examine the nest, and the old birds, excited beyond measure, fluttered round me close by pouring out their shrill rapidly-reiterated cries in an unbroken stream, sounding very much like a policeman's rattle. While I was looking closely at one of the eggs lying on the palm of my hand, all at once the cracked shell parted, and at the same moment the young bird leaped from my hand and fell into the water. I am quite sure that the young bird's sudden escape from the shell and my hand was the result of a violent effort on its part to free itself; and it was doubtless inspired to make the effort by the loud persistent screaming of the parent birds, which it heard while in the shell. Stooping to pick it up to save it from perishing, I soon saw that my assistance was not required, for immediately on dropping into the water, it put out its neck, and with the body nearly submerged, like a wounded duck trying to escape observation, it swam rapidly to the second small mound I have mentioned, and, escaping from the water, concealed itself in the grass, lying close and perfectly motionless like a young plover.
In the case of the pampa or creolla sheep, I have shown that during its long, rough life in La Plata, this variety has in some measure recovered the natural vigour and ability to maintain existence in
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adverse circumstances of its wild ancestors. As much can be said of the creolla fowl of the pampas; and some observations of mine on the habits of this variety will perhaps serve to throw light on a vexed question of Natural History--namely, the cackling of the hen after laying, an instinct which has been described as "useless" and "disadvantageous." In fowls that live unconfined, and which are allowed to lay where they like, the instinct, as we know it, is certainly detrimental, since egg-eating dogs and pigs soon learn the cause of the outcry, and acquire a habit of rushing off to find the egg when they hear it. The question then arises: Does the wild jungle fowl possess the same pernicious instinct?
The creolla is no doubt the descendant of the fowl originally introduced about three centuries ago by the first colonists in La Plata, and has probably not only been uncrossed with any other improved variety, such as are now fast taking its place, and has lived a much freer life than is usual with the fowl in Europe. It is a rather small, lean, extremely active bird, lays about a dozen eggs, and hatches them all, and is of a yellowish red colour--a hue which is common, I believe, in the old barn-door fowl of England. The creolla fowl is strong on the
wing, and much more carnivorous and rapacious in habits than other breeds; mice, frogs, and small snakes are eagerly hunted and devoured by it. At my home on the pampas a number of these fowls were kept, and were allowed to range freely about the plantation, which was large, and the adjacent grounds, where there were thickets of giant cardoon thistle, red-weed, thorn apple, &c. They always
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nested at a distance from the house, and it was almost impossible ever to find their eggs, on account of the extreme circumspection they observed in going to and from their nests; and when they succeeded in escaping foxes, skunks, weasels, and opossums, which, strange to say, they often did, they would rear their chickens away out of sight and hearing of the house, and only bring them home when winter deprived them of their leafy covering and made food scarce. During the summer, in. my rambles about the plantation, T would occasionally surprise one of these half-wild hens with her brood; her distracted screams and motions would then cause her chicks to scatter and vanish in all directions, and, until the supposed danger was past, they would lie as close and well-concealed as young partridges. These fowls in summer always lived in small parties, each party composed of one cock and as many hens as he could collect--usually three or four. Each family occupied its own feeding ground, where it would pass a greater portion of each day. The hen would nest at a considerable distance from the feeding ground, sometimes as far as four or five hundred yards away. After laying an egg she would quit the nest, not walking from it as other fowls do, but flying, the flight extending to a distance of from fifteen to about fifty yards; after which, still keeping silence, she would walk or run, until, arrived at the feeding ground, she would begin to cackle. At once the cock, if within hearing, would utter a responsive cackle, whereupon she would run to him and cackle no more. Frequently the cackling call-note would not be uttered more than two or three times, some-
Parental and Early Instincts.i 15
times only once, and in a much lower tone than in fowls of other breeds.
If we may assume that these fowls, in their long, semi-independent existence in La Plata, have reverted to the original instincts of the wild Gallus bankiva, we can see here how advantageous the cackling instinct must be in enabling the hen in dense tropical jungles to rejoin the flock after laying an egg. If there are egg-eating animals in the jungle intelligent enough to discover the meaning of such a short, subdued cackling call, they would still be unable to find the nest by going back on the bird's scent, since she flies from the nest in the first place; and the wild bird probably flies further than the creolla hen of La Plata. The clamorous cackling of our fowls would appear then to be nothing more than a perversion of a very useful instinct.
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CHAPTER VII
THE MEPHITIC SKUNK.
IT might possibly give the reader some faint conception of the odious character of this creature (for adjectives are weak to describo it) when I say that, in talking to strangers from abroad, I have never thought it necessary to speak of sunstroke, jaguars, or the assassin's knife, but have never omitted to warn them of the skunk, minutely describing its habits and personal appearance.
I knew an Englishman who, on taking a first gallop across the pampas, saw one, and, quickly dismounting, hurled himself bodily on to it to effect its capture. Poor man! he did not know that the little animal is never unwilling to be caught. Men have been blinded for ever by a discharge of the fiery liquid full in their faces. On a mucous membrane it burns like sulphuric acid, say the unfortunates who have had the experience. How does nature protect the skunk itself from the injurious effects of its potent fluid? I have not unfrequently found individuals stone-blind, sometimes moving so briskly about that the blindness must have been of long standing--very possibly in some cases an accidental drop discharged by the animal itself has caused the loss of sight. When coming to close
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quarters with a skunk, by covering up the face, one's clothes only are ruined. But this is not all one has to fear from an encounter; the worst is that effluvium, after which crushed garlic is lavender, which tortures the olfactory nerves, and appears to pervade the whole system like a pestilent ether, nauseating one until sea-sickness seems almost a pleasant sensation in comparison.
To those who know the skunk only from reputation, my words might seem too strong; many, however, who have come to close quarters with the little animal will think them ridiculously weak. And consider what must the feelings be of one who has had the following experience--not an uncommon experience on the pampas. There is to be a dance at a neighbouring house a few miles away; he has been looking forward to it, and, dressing himself with due care, mounts his horse and sets out full of joyous anticipations. It is a dark windy evening, but there is a convenient bridle-path through the dense thicket of giant thistles, and striking it he puts his horse into a swinging gallop. Unhappily the path is already occupied by a skunk, invisible in the darkness, that, in obedience to the promptings of its insane instinct, refuses to get out of it, until the flying hoofs hit it and sand it like a well-kicked football into the thistles. But the forefoot of the horse, up as high as his knees perhaps, have been sprinkled, and the rider, after coming out into the open, dismounts and walks away twenty yards from his animal, and literallysmellshimself all over, and with a feeling of profound relief pronounces himself Not the minutest drop of the diabolical spray
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has touched his dancing shoes! Springing into the saddle he proceeds to his journey's end, is warmly welcomed by his host, and speedily forgetting his slight misadventure, mingles with a happy crowd of friends. In a little while people begin exchanging whispers and significant glances; men are seen smiling at nothing in particular; the hostess wears a clouded face; the ladies cough and put their scented handkerchiefs to their noses, and presently they begin to feel faint and retire from the room. Our hero begins to notice that there is something wrong, and presently discovers its cause; he, unhappily, has been the last person in the room to remark that familiar but most abominable odour, rising like a deadly exhalation from the floor, conquering all other odours, and every moment becoming more powerful. A drophastouched his shoe after all; and fearing to be found out, and edging towards the door, he makes his escape, and is speedily riding home again; knowing full well that his sudden and early departure from the scene will be quickly discovered and set down to the right cause.
In that not always trustworthy bookThe Natural History of Chili,Molina tells us how they deal with the animal in the trans-Andine regions. "When one appears," he says, "some of the company begiu by caressing it, until an opportunity offers for one of them to seize it by the tail. In this position the muscles become contracted, the animal is unable to eject its fluid, and is quickly despatched." One might just as well talk of caressing a cobra de capello; yet this laughable fiction finds believers
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all over South and North America. Professor Baird gravely introduces it into his great work on the mammalia. I was once talking about animals in a rancho, when a person present (an Argentine officer) told that, while visiting an Indian encampment, he had asked the savages how they contrived to kill skunks without making even a life in the desert intolerable. A grave old Cacique informed him that the secret was to go boldly up to the animal, take it by the tail, and despatch it; for, he said, when you fear it not at all, then it respects your courage and dies like a lamb--sweetly. The officer, continuing his story, said that on quitting the Indian camp he started a skunk, and, glad of an opportunity to test the truth of what he had heard, dismounted and proceeded to put the Indian plan in practice. Here the story abruptly ended, and when I eagerly demanded to hear the sequel, the amateur hunter of furs lit a cigarette and vacantly watched the ascending smoke. The Indians aro grave jokers, they seldom smile; and this old traditional skunk-joke, which has run the length of a continent, finding its way into many wise books, is their revenge on a superior race.
I have shot a great many eagles, and occasionally a carancho (Polyborus tharus), with the plumage smelling strongly of skunk, which shows that these birds, pressed by hunger, often commit the fearful mistake of attacking the animal. My friend Mr. Ernest Gibson, of Buenos Ayres, in a communication to theIbis,describes an encounter he actually witnessed between a carancho and a skunk. Riding home one afternoon, he spied a skunk "shuffling
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along in the erratic manner usual to that odoriferous quadruped;" following it at a very short distance was an eagle-vulture, evidently bent on mischief. Every time the bird came near the bushy tail rose menacingly; then the carancho would fall behind, and, after a few moments' hesitation, follow on again. At length, growing bolder, it sprung forward, seizing the threatening tail with its claw, but immediately after "began staggering about with dishevelled plumage, tearful eyes, and a profoundly woe-begone expression on its vulture face. The skunk, after turning and regarding its victim with an I-told-you-so look for a few moments, trotted unconcernedly off."
I was told in Patagonia by a man named Molinos, who was frequently employed by the Government as guide to expeditions in the desert, that everywhere throughout that country the skunk is abundant. Some years ago he was sent with two other men to find and treat with an Indian chief whose whereabouts were not known. Far in the interior Molinos was overtaken by a severe winter, his horses died of thirst and fatigue, and during the three bitterest months of the year he kept himself and his followers alive by eating the flesh of skunks, the only wild animal that never failed them. No doubt, on those vast sterile plains where the skunk abounds, and goes about by day and by night careless of enemies, the terrible nature of its defensive weapon is the first lesson experience teaches to every young eagle, fox, wild cat, and puma.
Dogs kill skunks when made to do so, but it is not a sport they delight in. One moonlight night,
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at home, I went out to where the dogs, twelve in number, were sleeping: while I stood there a skunk appeared and deliberately came towards me, passing through the dogs where they lay, and one by one as he passed them they rose up, and, with their tails between their legs, skulked off. When made to kill skunks often they become seasoned; but always perform the loathsome task expeditiously, then rush away with frothing mouths to rub their faces in the wet clay and rid themselves of the fiery sensation. At one time I possessed only one dog that could be made to face a skunk, and as the little robbers were very plentiful, and continually coining about the house in their usual open, bold way, it was rather hard for the poor brute. This dog detested them quite as strongly as the others, only he was more obedient, faithful, and brave. Whenever I bade him attack one of them he would come close up to me and look up into my face with piteous pleading eyes, then, finding that he was not to be let off from the repulsive task, he would charge upon the doomed animal with a blind fury wonderful to see. Seizing it between his teeth, he would shake it madly, crushing its bones, then hurl it several feet from him, only to rush again and again upon it to repeat the operation, doubtless with a Caligula-like wish in his frantic breast that all the skunks on the globe had but one backbone.
I was once on a visit to a sheep-farming brother, far away on the southern frontier of Buenos Ayres, and amongst the dogs I found there was one most interesting creature, He was a great, lumbering,
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stupid, good-tempered brute, so greedy that when you offered him a piece of meat he would swallow half your arm, and so obedient that at a word he would dash himself against the horns of a bull, and face death and danger in any shape. But, my brother told me, he would not face a skunk--he would die first. One day I took him out and found a skunk, and for upwards of half an hour I sat on my horse vainly cheering on my cowardly follower, and urging him to battle. The very sight of the enemy gave him a fit of the shivers; and when the irascible little enemy began to advance against us, going through the performance by means of which he generally puts his foes to flight without resorting to malodorous measures--stamping his little feet in rage, jumping up, spluttering and hissing and flourishing his brush like a warlike banner above his head--then hardly could I restrain my dog from turning tail and flying home in abject terror. My cruel persistence was rewarded at last. Continued shouts, cheers, and hand-clappings began to stir the brute to a kind of frenzy. Torn by conflicting emotions, he began to revolve about the skunk at a lumbering gallop, barking, howling, and bristling up his hair; and at last, shutting his eyes, and with a yell of desperation, he charged. I fully expected to see the enemy torn to pieces in a few seconds, but when the dog was still four or five feet from him the fatal discharge came, and he dropped down as if shot dead. For some time he lay on the earth perfectly motionless, watched and gently bedewed by the victorious skunk; then he got up and crept whining away. Gradually he quickened his pace,
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finally breaking into a frantic run. In vain I followed him, shouting at the top of my lungs; he stayed not to listen, and very speedily vanished from sight--a white speck on the vast level plain. At noon on the following day he made his appearance, gaunt and befouled with mud, staggering forward like a galvanized skeleton. Too worn out
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Skunk and dog.
even to eat, he flung himself down, and for hours lay like a dead thing, sleeping off the effects of those few drops of perfume.
Dogs, I concluded, like men, have their idiosyncrasies; but I had gained my point, and proved once more--if any proof were needed--the truth of that noble panegyric of Bacon's on our faithful servant and companion.
CHAPTER VIII.
MIMICRY AND WARNING COLOURS IN GRASSHOPPERS.
THERE is in La Plata a large handsome grasshopper (Zoniopoda tarsata), the habits of which in its larva and imago stages are in strange contrast, like those in certain lepidoptera, in which the caterpillars form societies and act in concert. The adult has a greenish protective colouring, brown and green banded thighs, bright red hind wings, seen only during flight. It is solitary and excessively shy in its habits, living always in concealment among the dense foliage near the surface of the ground. The yonng are intensely black, like grasshoppers cut out of jet or ebony, and gregarious in habit, living in bands of forty or fifty to three or four hundred; and so little shy, that they may sometimes be taken up by handfuls before they begin to scatter in alarm. Their gregarious habits and blackness--of all hues in nature the most obvious to the sight--would alone be enough to make them the most conspicuous of insects; but they have still other habits which appear as if specially designed to bring them more prominently into notice. Thus, they all keep so close together at all times as to have their bodies actually touching, and when
Mimicry and Warning Colours in Grasshoppers.25
travelling, move so slowly that the laziest snail might easily overtake and pass one of their bands, and even disappear beyond their limited horizon in a very short time.
They often select an exposed weed to feed on, clustering together on its summit above the surrounding verdure, an exceedingly conspicuous object to every eye in the neighbourhood. They also frequently change their feeding-ground; at such times they deliberately cross wide roads and other open spaces, barren of grass, where, moving so slowly that they scarcely seem to move at all, they look at a distance like a piece of black velvet lying on the ground. Thus in every imaginable way they expose themselves and invite attack; yet, in spite of it all, I have never detected birds preying on them, and I have sometimes kept one of these black societies under observation near my house for several days, watching them at intervals, in places where the trees overhead were the resort of Icterine and tyrant birds, Guira cuckoos, and other species, all great hunters after grasshoppers. A young grasshopper is, moreover, a morsel that seldom comes amiss to any bird, whether insect or seed eater; and, as a rule, it is extremely shy, nimble, and inconspicuous. It seems clear that, although the young Zoniopoda does not mimic in its form any black protected insect, it nevertheless owes its safety to its blackness, together with the habit it possesses of exposing itself in so open and bold a manner. Blackness is so common in large protected insects, as, for instance, in the un-palatable leaf-cutting ants, scorpions, mygale
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spiders, wasps, and other dangerous kinds, that it is manifestly a "warning colour," the most universal and best known in nature; and the grasshopper, I believe, furthermore mimics the fearless demeanour of the protected or venomous species, which birds and other insect-eaters know and respect. It might be supposed that the young Zoniopoda is itself unpalatable; but this is scarcely probable, for when the deceptive black mask is once dropped, the excessive shyness, love of concealment, and protective colouring of the insect show that it is much sought after by birds.
While setting this down as an undoubted case of "mimicry," although it differs in some respects from all other cases I have seen reported, I cannot help remarking that this most useful word appears to be in some danger of losing the meaning originally attached to it in zoology. There are now very few cases of an accidental resemblance found between two species in nature which are not set down by someone to "mimicry," some in which even the wildest imagination might well fail to see any possible benefit to the supposed mimic. In cases where the outward resemblance of some feeble animal to a widely different and well-protected species, or to some object like a leaf or stick, and where such resemblance is manifestly advantageous and has reacted on and modified the life habits, it is conceivable that slight spontaneous variations in the structure and colouring of the unprotected species have been taken advantage of by the principle of natural selection, and a case of "mimicry" set up, to become more and more
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perfect in time, as successive casual variations in the same direction increased the resemblance.
The stick-insect is perhaps the most perfect example where resemblance to an inanimate object has been the result aimed at, so to speak, by nature; the resemblance of the volucella fly to the humble-bee, on which it is parasitical, is the most familiar example of one species growing like another to its own advantage, since only by means of its deceptive likeness to the humble-bee is it able to penetrate into the nest with impunity. These two cases, with others of a similar character, were first called cases of "mimicry" by Kirby and Spence, in their ever-delightfulIntroduction to Entomology--an old book, but, curiously enough in these days of popular treatises on all matters of the kind, still the only general work on insects in the English language which one who is not an entomologist can read with pleasure.
A second case of mimicry not yet noticed by any naturalist is seen in another grasshopper, also common in La Plata (Rhomalea speciosa of Thun-berg). This is an extremely elegant insect; the head and thorax chocolate, with cream-coloured markings; the abdomen steel-blue or purple, a colour I have not seen in any other insects of this family. The fore wings have a protective colouring; the hind wings are bright red. When at rest, with the red and purple tints concealed, it is only a very pretty grasshopper, but the instant it takes wing it becomes the fac-simile of a very common wasp of the genus Pepris. These wasps vary greatly in size, some being as large as the hornet;
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they are solitary, and feed on the honey of flowers and on fruit, and, besides being furnished with stings like other wasps--though their sting is nok so venomous as in other genera--they also, when angry, emit a most abominable odour, and are thus doubly protected against their enemies. Their excessive tameness, slow flight, and indolent motions serve to show that they are not accustomed to be interfered with. All these strong-smelling wasps have steel-blue or purple bodies, and bright red wings. So exactly does the Rhomalea grasshopper mimic the Pepris when flying, that I have been deceived scores of times. I have even seen it on the leaves, and, after it has flown and settled once more, I have gone to look at it again, to make sure that my eyes had not deceived me. It is curious to see how this resemblance has reacted on and modified the habits of the grasshopper. It is a great flyer, and far more aerial in its habits than any other insect I am acquainted with in this family, living always in trees, instead of on or near the surface of the ground. It is abundant in orchards and plantations round Buenos Ayres, where its long and peculiarly soft, breezy note may be heard all summer. If the ancient Athenians possessed so charming an insect as this, their great regard for the grasshopper was not strange: I only wish that the "Athenians of South America," as my fellow-townsmen sometimes call themselves in moments of exaltation, had a feeling of the samo kind--the regard which doesnotimpale its object on a pin--for the pretty light-hearted songster of their groves and gardens.
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When taken in the hand, it has the habit, common to most grasshoppers, of pouring out an inky fluid from its mouth; only the discharge is unusually copious in this species. It has another habit in defending itself which is very curious. When captured it instantly curls its body round, as a wasp does to sting. The suddenness of this action has more than once caused me to drop an insect I had taken, actually thinking for the moment that I had taken hold of a wasp. Whether birds would be deceived and made to drop it or not is a question it would not be easy to settle; but the instinct certainly looks like 'one of a series of small adaptations, all tending to make the resemblance to a wasp more complete and effective.
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CHAPTER IX.
DRAGON-FLY STORMS.
ONE of the most curious things I have encountered in my observations on animal life relates to a habit of the larger species of dragon-flies inhabiting the Pampas and Patagonia. Dragon-flies are abundant throughout the country wherever there is water. There are several species, all more or less brilliantly coloured. The kinds that excited my wonder, from their habits, are twice as large as the common widely distributed insects, being three inches to four inches in length, and as a rule they are sober-coloured, although there is one species--the largest among them--entirely of a brilliant scarlet. This kind is, however, exceedingly rare. All the different kinds (of the large dragon-flies) when travelling associate together, and occasionally, in a flight composed of countless thousands, one of these brilliant-hued individuals will catch the eye, appearing as conspicuous among the others as a poppy or scarlet geranium growing alone in an otherwise flowerless field. The most common species--and in some cases the entire flight seems to be composed of this kind only--is the Aeschna bonariensis Raml, the prevailing colour of which is pale blue. But the really wonderful thing about them all alike is,
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that they appear only when flying before the southwest wind, calledpampero--the wind that blows from the interior of the pampas. The pampero is a dry, cold wind, exceedingly violent. It bursts on the plains very suddenly, and usually lasts only a short time, sometimes not more than ten minutes; it comes irregularly, and at all seasons of the year, but is most frequent in the hot season, and after exceptionally sultry weather. It is in summer and autumn that the large dragon-flies appear; notwiththe wind, but--and this is the most curious part of the matter--in advance of it; and inasmuch as these insects are not seen in the country at other times, and frequently appear in seasons of prolonged drought, when all the marshes and water-courses for many hundreds of miles are dry, they must of course traverse immense distances, flying before the wind at a speed of seventy or eighty miles an hour. On some occasions they appear almost simultaneously with the wind, going by like a flash, and instantly disappearing from sight. You have scarcely time to see them before the wind strikes you. As a rule, however, they make their appearance from five to fifteen minutes before the wind strikes; and when they are in great numbers the air, to a height of ten or twelve feet above the surface of the ground, is all at once seen to be full of them, rushing past with extraordinary velocity in a north-easterly direction. In very oppressive weather, and when the swiftly advancing pampero brings no moving mountains of mingled cloud and dust, and is consequently not expected, the sudden apparition of the dragon-fly is a most welcome one,
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for then an immediate burst of cold wind is confidently looked for. In the expressive vernacular of the gauchos the large dragon-fly is calledhijo del pampero--son of the south-west wind.
It is clear that these great and frequent dragonfly movements are not explicable on any current hypothesis regarding the annual migrations of birds, the occasional migrations of butterflies, or the migrations of some mammals, like the reindeer and buffalo of Arctic America, which, according to Rae and other observers, perform long journeys north and south at regular seasons, "from a sense of polarity." Neither this hypothetical sense in animals, nor "historical memory" will account for the dragon-fly storms, as the phenomenon of the pampas might be called, since the insects do not pass and repass between "breeding and subsistence areas," but all journey in a north-easterly direction; and of the countless millions flying like thistledown before the great pampero wind, not one solitary traveller ever returns.
The cause of the flight is probably dynamical, affecting the insects with a sudden panic, and compelling them to rush away before the approaching tempest. The mystery is that they should fly from the wind before it reaches them, and yet travel in the same direction with it. When they pass over the level, treeless country, not one insect lags behind, or permits the wind to overtake it; but, on arriving at a wood or large plantation they swarm into it, as if seeking shelter from some swift-pursuing enemy, and on such occasions they sometimes remain clinging to the trees while the