In that not always trustworthy book The 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 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 the Ibis, describes an encounter he actually witnessed between a carancho and a skunk. Riding home one afternoon, he spied a skunk "shuffling 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, 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, 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, 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 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 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 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 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-delightful Introduction 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; 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 does not impale its object on a pin—for the pretty light-hearted songster of their groves and gardens.

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.



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, that they appear only when flying before the southwest wind, called pampero—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; not with the 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 watercourses 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, for then an immediate burst of cold wind is confidently looked for. In the expressive vernacular of the gauchos the large dragon-fly is called hijo 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 wind spends its force. This is particularly the case when the wind blows up at a late hour of the day; then, on the following morning, the dragon-flies are seen clustering to the foliage in such numbers that many trees are covered with them, a large tree often appearing as if hung with curtains of some brown glistening material, too thick to show the green leaves beneath.

In Patagonia, where the phenomenon of dragon-fly storms is also known, an Englishman residing at the Rio Negro related to me the following occurrence which he witnessed there. A race meeting was being held near the town of El Carmen, on a high exposed piece of ground, when, shortly before sunset, a violent pampero wind came up, laden with dense dust-clouds. A few moments before the storm broke, the air all at once became obscured with a prodigious cloud of dragon-flies. About a hundred men, most of them on horseback, were congregated on the course at the time, and the insects, instead of rushing by in their usual way, settled on the people in such quantities that men and horses were quickly covered with clinging masses of them. My informant said—and this agrees with my own observation—that he was greatly impressed by the appearance of terror shown by the insects; they clung to him as if for dear life, so that he had the greatest difficulty in ridding himself of them.

Weissenborn, in London's Magazine of Natural History (N. S. vol. iii.) describes a great migration of dragon-flies which he witnessed in Germany in 1839, and also mentions a similar phenomenon occurring in 1816, and extending over a large portion of Europe. But in these cases the movement took place at the end of May, and the insects travelled due south; their migrations were therefore similar to those of birds and butterflies, and were probably due to the same cause. I have been unable to find any mention of a phenomenon resembling the one with which we are so familiar on the pampas, and which, strangely enough, has not been recorded by any European naturalists who have travelled there.



CHAPTER X.

MOSQUITOES AND PARASITE PROBLEMS.

There cannot be a doubt that some animals possess an instinctive knowledge of their enemies—or, at all events, of some of their enemies—though I do not believe that this faculty is so common as many naturalists imagine. The most striking example I am acquainted with is seen in gnats or mosquitoes, and in the minute South American sandflies (Simulia), when a dragon-fly appears in a place where they are holding their aerial pastimes. The sudden appearance of a ghost among human revellers could not produce a greater panic. I have spoken in the last chapter of periodical storms or waves of dragon-flies in the Plata region, and mentioned incidentally that the appearance of these insects is most welcome in oppressively hot weather, since they are known to come just in advance of a rush of cool wind. In La Plata we also look for the dragon-fly, and rejoice at its coming, for another reason. We know that the presence of this noble insect will cause the clouds of stinging gnats and flies, which make life a burden, to vanish like smoke.

When a flight of dragon-flies passes over the country many remain along the route, as I have said, sheltering themselves wherever trees occur; and, after the storm blows over, these strangers and stragglers remain for some days hawking for prey in the neighbourhood. It is curious to note that they do not show any disposition to seek for watercourses. It may be that they feel lost in a strange region, or that the panic they have suffered, in their long flight before the wind, has unsettled their instincts; for it is certain that they do not, like the dragon-fly in Mrs. Browning's poem, "return to dream upon the river." They lead instead a kind of vagabond existence, hanging about the plantations, and roaming over the surrounding plains. It is then remarked that gnats and sand-flies apparently cease to exist, even in places where they have been most abundant. They have not been devoured by the dragon-flies, which are perhaps very few in number; they have simply got out of the way, and will remain in close concealment until their enemies take their departure, or have all been devoured by martins, tyrant birds, and the big robber-flies or devil's dykes—no name is bad enough for them—of the family Asilidaa. During these peaceful gnatless days, if a person thrusts himself into the bushes or herbage in some dark sheltered place, he will soon begin to hear the thin familiar sounds, as of "horns of elf-land faintly blowing"; and presently, from the ground and the under surface of every leaf, the ghost-like withered little starvelings will appear in scores and in hundreds to settle on him, fear not having blunted their keen appetites.

When riding over the pampas on a hot still day, with a pertinacious cloud of gnats or sandflies hovering just above my head and keeping me company for miles, I have always devoutly wished for a stray dragon-fly to show himself. Frequently the wish has been fulfilled, the dragon-fly, apparently "sagacious of his quarry from afar," sweeping straight at his prey, and instantly, as if by miracle, the stinging rain has ceased and the noxious cloud vanished from overhead, to be re-formed no more. This has always seemed very extraordinary to me; for in other matters gnats do not appear to possess even that proverbial small dose of intellect for which we give most insects credit. Before the advent of the dragon-fly it has perhaps happened that I have been vigorously striking at them, making it very unpleasant for them, and also killing and disabling many hundreds—a larger number than the most voracious dragon-fly could devour in the course of a whole day; and yet, after brushing and beating them off until my arms have ached with the exertion, they have continued to rush blindly on their fate, exhibiting not the faintest symptom of fear. I suppose that for centuries mosquitoes have, in this way, been brushed and beaten away with hands and with tails, without learning caution. It is not in their knowledge that there are hands and tails. A large animal is simply a field on which they confidently settle to feed, sounding shrill flourishes on their little trumpets to show how fearless they are. But the dragon-fly is very ancient on the earth, and if, during the Devonian epoch, when it existed, it preyed on some blood-sucking insect from which or Culicidae have come, then these stupid little insects have certainly had ample time in which to learn well at least one lesson.

There is not in all organic nature, to my mind, any instance of wasted energy comparable in magnitude with the mosquito's thirst for blood, and the instincts and elaborate blood-pumping apparatus with which it is related. The amount of pollen given off by some wind-fertilized trees—so great in some places that it covers hundreds of square miles of earth and water with a film of yellow dust—-strikes us as an amazing waste of material on the part of nature; but in these cases we readily see that this excessive prodigality is necessary to continue the species, and that a sufficient number of flowers would not be impregnated unless the entire trees were bathed for days in the fertilizing cloud, in which only one out of many millions of floating particles can ever hit the mark. The mosquito is able to procreate without ever satisfying its ravenous appetite for blood. To swell its grey thread-like abdomen to a coral bead is a delight to the insect, but not necessary to its existence, like food and water to ours; it is the great prize in the lottery of life, which few can ever succeed in drawing. In a hot summer, when one has ridden perhaps for half a day over a low-lying or wet district, through an atmosphere literally obscured with a fog of mosquitoes, this fact strikes the mind very forcibly, for in such places it frequently is the case that mammals do not exist, or are exceedingly rare. In Europe it is different. There, as Reaumur said, possibly one gnat in every hundred may be able to gratify its appetite for blood; but of the gnats in many districts in South America it would be nearer the mark to say that only one in a hundred millions can ever do so.

Curtis discovered that only the female mosquito bites or sucks blood, the male being without tongue or mandibles; and he asks, What, then, does the male feed on? He conjectures that it feeds on flowers; but, had he visited some swampy places in hot countries, where flowers are few and the insects more numerous than the sands on the seashore, he would most probably have said that the males subsist on decaying vegetable matter and moisture of slime. It is, however, more important to know what the female subsists on. We know that she thirsts for warm mammalian blood, that she seeks it with avidity, and is provided with an admirable organ for its extraction—only, unfortunately for her, she does not get it, or, at all events, the few happy individuals that do get it are swamped in the infinite multitude of those that are doomed by nature to total abstinence.

I should like to know whether this belief of Curtis, shared by Westwood and other distinguished entomologists, but originally put forward merely as a conjecture, has ever been tested by careful observation and experiment. If not, then it is strange that it should have crept into many important works, where it is stated not as a mere guess, but as an established fact. Thus, Van Beneden, in his work on parasites, while classing female mosquitoes with his "miserable wretches," yet says, "If blood fails them, they live, like the males, on the juices of flowers." If this be so, it is quite certain that the juices fail to satisfy them; and that, like Dr. Tanner, who was ravenously hungry during his forty days' fast, in spite of his frequent sips of water, the mosquito still craves for something better than a cool vegetarian diet. I cannot help thinking, though the idea may seem fanciful, that mosquitoes feed on nothing. We know that the ephemerae take no refreshment in the imago state, the mouth being aborted or atrophied in these short-lived creatures; but we also know that they belong to an exceedingly ancient tribe, and possibly, after the earth had ceased to produce their proper nourishment there came in their history a long hungry period, which did not kill them, but lasted until their feeding instincts became obsolete, the mouth lost its use, and their life in its perfect state dwindled to its present length.

In any case, how unsatisfactory is the mosquitoes' existence, and what a curious position they occupy in nature! Let us suppose that, owing to some great change in the conditions of the earth, rapacious birds were no longer able to capture prey, and that, by a corresponding change in their organizations, they were able to subsist on the air they breathed, with perhaps an occasional green leaf and a sip of water, and yet retained the old craving for solid food, and the old predatory instincts and powers undiminished; they would be in the position of mosquitoes in the imago state. And if then fifty or a hundred individuals were to succeed every year in capturing something and making one hearty meal, these few fortunate diners would bear about the same proportion to all the raptors on the globe as the mosquitoes that succeed in sucking blood to their unsuccessful fellows. In the case of the hawks, the effect of the few meals on the entire rapacious family or order would certainly be nil; and it is impossible to believe for a moment that the comparatively infinitesimal amount of blood sucked by mosquitoes can. serve to invigorate the species. The wonder is that the machinery, which accomplishes nothing, should continue in such perfect working order.

When we consider the insect's delicate organ, so admirably fitted for the purpose to which it is applied, it becomes difficult to believe that it could have been so perfected except in a condition of things utterly unlike the present. There must have been a time when mosquitoes found their proper nourishment, and when warm mammalian blood was as necessary to their existence as honey is to that of the bee, or insect food to the dragon-fly.

This applies to many blood-sucking insects besides mosquitoes, and with special force to the tick tribes (Ixodes), which swarm throughout Central and South America; for in these degraded spiders the whole body has been manifestly modified to fit it for a parasitical life; while the habits of the insect during its blind, helpless, waiting existence on trees, and its sudden great development when it succeeds in attaching itself to an animal body, also point irresistibly to the same conclusion. In the sunny uplands they act (writes Captain Burton) like the mosquitoes of the hot, humid Beiramar. "The nuisance is general; it seems to be in the air; every blade of grass has its colony; clusters of hundreds adhere to the twigs; myriads are found in the bush clumps. Lean and flat when growing to the leaves, the tick catches man or beast brushing by, fattens rapidly, and, at the end-of a week's good living, drops off, plena cruoris." When on trees, Belt says, they instinctively place themselves on the extreme tips of leaves and shoots, with their hind legs stretching out, each foot armed with two hooks or claws, with which to lay hold of any animal brushing by. During this wretched, incom-plete existence (from which, in most cases, it is never destined to emerge), its greatest length is about one-fourth of an inch; but where it fastens itself to an animal the abdomen increases to a globe as big as a medium-sized Barcelona nut. Being silvery-grey or white in colour, it becomes, when thus distended, very conspicuous on any dark surface. I have frequently seen black, smooth-haired dogs with their coats, turned into a perfect garden of these white spider-flowers or mushrooms. The white globe is leathery, and nothing can injure it; and the poor beast cannot rub, bite, or scratch it off, as it is anchored to his flesh by eight sets of hooks and a triangle of teeth.

The ticks inhabiting regions rich in bird and insect life, but with few mammals, are in the same condition as mosquitoes, as far as the supply of blood goes; and, like the mosquitoes, they are compelled and able to exist without the nourishment best suited to them. They are nature's miserable castaways, parasitical tribes lost in a great dry wilderness where no blood is; and every marsh-born mosquito, piping of the hunger gnawing its vitals, and every forest tick, blindly feeling with its grappling-irons for the beast that never brushes by, seems to tell us of a world peopled with gigantic forms, mammalian and reptilian, which once afforded abundant pasture to the parasite, and which the parasite perhaps assisted to overthrow.

It is almost necessary to transport oneself to the vast tick-infested wilderness of the New World to appreciate the full significance of a passage in Belt's Naturalist in Nicaragua, in which it is suggested that man's hairless condition was perhaps brought about by natural selection in tropical regions, where he was greatly troubled with parasites of this kind. It is certain that if in such a country as Brazil he possessed a hairy coat, affording cover to the tick and enabling it to get a footing on the body, his condition would be a very sad one. Savages abhor hairs on the body, and even pluck them off their faces. This seems like a survival of an ancient habit acquired when the whole body was clothed with hair; and if primitive man ever possessed such a habit, nature only followed his lead in giving him a hairless offspring.

Is it not also probable that the small amount of mammalian life in South America, and the aquatic habits of nearly all the large animals in the warmer districts, is due to the persecutions of the tick?

The only way in which a large animal can rid itself of the pest is by going into the water or wallowing in the mud; and this perhaps accounts for the more or less aquatic habits of the jaguar, aguara-guazu, the large Cervus paluclosus, tapir, capybara, and peccary. Monkeys, which are most abundant, are a notable exception; but these animals have the habit of attending to each other's skins, and spend a great deal of their time in picking off the parasites. But how do birds escape the ticks, since these parasites do not confine their attacks to any one class of aninials, but attach themselves impartially to any living thing coming within reach of their hooks, from snake to man? My own observations bearing on this point refer less to the Ixodes than to the minute bete-rouge, which is excessively abundant in the Plata district, where it is known as bicho colorado, and in size and habits resembles the English Leptus autumnalis. It is so small that, notwithstanding its bright scarlet colour, it can only be discerned by bringing the eye close to it; and being, moreover, exceedingly active and abundant in all shady places in summer—making life a misery to careless human beings—it must be very much more dangerous to birds than the larger sedentary Ixodes. The bete-rouge invariably lodges beneath the wings of birds, where the loose scanty plumage affords easy access to the skin. Domestic birds suffer a great deal from its persecutions, and their. young, if allowed to run about in shady places, die of the irritation. Wild birds, however, seem to be very little troubled, and most of those I have examined have been almost entirely free from parasites. Probably they are much more sensitive than the domestic birds, and able to feel and pick off the insects with their beaks before they have penetrated into the skin. I believe they are also able to protect themselves in another way, namely, by preventing the parasites from reaching their bodies at all. I was out under the trees one day with a pet oven-bird (Furnarius rufus), which had full liberty to range about at will, and noticed that at short intervals it went through the motions of picking something from its toes or legs, though I could see nothing on them. At length I approached my eyes to within a few inches of the bird's feet, and discovered that the large dry branch on which it stood was covered with a multitude of parasites, all running rapidly about like foraging ants, and whenever one came to the bird's feet it at once ran up the leg. Every time this happened, so far as I could see, the bird felt it. and quickly and deftly picked it off with the point of its bill. It seemed very astonishing that the horny covering of the toes and legs should be so exquisitely sensitive, for the insects are so small and light that they cannot be felt on the hand, even when a score of them are running over it; but the fact is as I have stated, and it is highly probable, I think, that most wild birds keep themselves free from these little torments in the same way.

Some observations of mine on a species of Orni-thomyia—a fly parasitical on birds—might possibly be of use in considering the question of the anomalous position in nature of insects possessing the instincts and aptitudes of parasites, and organs manifestly modified to suit a parasitical mode of life, yet compelled and able to exist free, feeding, perhaps, on vegetable juices, or, like the ephemerae, on nothing at all. For it must be borne in mind that I do not assert that these "occasional" or "accidental" parasites, as some one calls them, explaining nothing, do not feed on such juices. I do not know what they feed on. I only know that the joyful alacrity with which gnats and stinging flies of all kinds abandon the leaves, supposed to afford them pasture, to attack a warm-blooded animal, serves to show how strong the impulse is, and how ineradicable the instinct, which must have had an origin. Perhaps the habits of the bird-fly I have mentioned will serve to show how, in some cases, the free life of some blood-sucking flies and other insects might have originated.

Kirby and Spence, in their Introduction, mention that one or two species of Ornithomyia have been observed flying about and alighting on men; and in one case the fly extracted blood and was caught, the species being thus placed beyond doubt. This circumstance led the authors to believe that the insect, when the bird it is parasitical on dies, takes to flight and migrates from body to body, occasionally tasting blood until, coming to the right body—to wit, that of a bird, or of a particular species of bird—it once more establishes itself permanently in the plumage. I fancy that the insect sometimes leads a freer life and ranges much more than the authors imagined; and I refer to Kirby and Spence, with apologies to those who regard the Introduction as out of date, only because I am not aware that we have any later observations on the subject.

There is in La Plata a small very common Dendrocolaptine bird—Anumbius acuticaudatus—much infested by an Ornithomyia, a pretty, pale insect, half the size of a house-fly, and elegantly striped with green. It is a very large parasite for so small a bird, yet so cunning and alert is it, and so swiftly is it able to swim through the plumage, that the bird is unable to rid itself of so undesirable a companion. The bird lives with its mate all the year round, much of the time with its grown-up young, in its nest—a large structure, in which so much building-material is used that the bird is called in the vernacular Lenatero, or Firewood-gatherer. On warm bright days without wind, during the absence of the birds, I have frequently seen a company of from half a dozen to a dozen or fifteen of the parasitical fly wheeling about in the air above the nest, hovering and gambolling together, just like house-flies in a room in summer; but always on the appearance of the birds, returning from their feeding-ground, they would instantly drop down and disappear into the nest. How curious this instinct seems! The fly regards the bird, which affords it the warmth and food essential to life, as its only deadly enemy; and with an inherited wisdom, like that of the mosquito with regard to the dragon-fly, or of the horse-fly with regard to the Monedula wasp, vanishes like smoke from its presence, and only approaches the bird secretly from a place of concealment.

The parasitical habit tends inevitably to degrade the species acquiring it, dulling its senses and faculties, especially those of sight and locomotion; but the Ornithomyia seems an exception, its dependent life having had a contrary effect; the extreme sensitiveness, keenness of sight, and quickness of the bird having reacted on the insect, giving it a subtlety in its habits and motions almost without a parallel even among free insects. A man with a blood-sucking flat-bodied flying squirrel, concealing itself among his clothing and gliding and dodging all over his body with so much artifice and rapidity as to defeat all efforts made to capturo it or knock it off, would be a case parallel to that of the bird-fly on the small bird. It might be supposed that the Firewood-gatherer, like some ants that keep domestic pets, makes a pet of the fly; for it is a very pretty insect, barred with green, and with rainbow reflections on its wings—and birds are believed by some theorists to possess aesthetic tastes; but the discomfort of having such a vampire on the body would, I imagine, be too great to allow a kindly instinct of that nature to grow up. Moreover, I have on several occasions seen the bird making frantic efforts to capture one of the flies, which had incautiously flown up from the nest at the wrong moment. Bird and fly seem to know each other wonderfully well.

Here, then, we have a parasitical insect specialized in the highest degree, yet retaining all its pristine faculties unimpaired, its love of liberty, and of associating in numbers together for sportive exercises, and well able to take care of itself during its free intervals. And probably when thrown on the world, as when nests are blown down, or the birds get killed, or change their quarters, as they often do, it is able to exist for some time without avian blood. Let us then imagine some of these orphaned colonies, unable to find birds, but through a slight change in habits or organization able to exist in the imago state without sucking blood until they laid their eggs; and succeeding generations, still better able to stand the altered conditions of life until they become practically independent (like gnats), multiplying greatly, and disporting themselves in clouds over forests, yet still retaining the old hunger for blood and the power to draw it, and ready at any moment to return to the ancestral habit. It might be said that if such a result were possible it would have occurred, but that we find no insect like the Ornithomyia existing independently. With the bird-fly it has not occurred, as far as we know; but in the past history of some independent parasites it is possible that something similar to the imaginary case I have sketched may have taken place. The bush-tick is a more highly specialized, certainly a more degraded, creature than the bird-fly, and the very fact of its existence seems to show that it is possible for even the lowest of the fallen race of parasites to start afresh in life under new conditions, and to reascend in the scale of being, although still bearing about it the marks of former degeneracy.

The connection between the flea and the mammal it feeds on is even less close than that which exists between the Ornithomyia and bird. The fact that fleas are so common and universal—for in all lands we have them, like the poor, always with us; and that they are found on all mammals, from the king of beasts to the small modest mouse—seems to show a great amount of variability and adaptiveness, as well as a very high antiquity. It has often been reported that fleas have been found hopping on the ground in desert places, where they could not have been dropped by man or beast; and it has been assumed that these "independent" fleas must, like gnats and ticks, subsist on vegetable juices. There is no doubt that they are able to exist and propagate for one or two years after being deprived of their proper aliment; houses shut up for a year or longer are sometimes found infested with them; possibly in the absence of "vegetable juices" they flourish on dust. I have never detected them hopping on the ground in uninhabited places, although I once found them in Patagonia, in a hamlet which had been attacked and depopulated by the Indians about twenty months before my visit. On entering one of the deserted huts I found the floor literally swarming with fleas, and in less than ten seconds my legs, to the height of my knees, were almost black with their numbers. This proves that they are able toincrease greatly for a period without blood; but I doubt that they can go on existing and increasing for an indefinite time; perhaps their true position, with regard to the parasitical habit, is midway between that of the strict parasite which never leaves the body, and that of independent parasites like the Culex and the Ixodes, and all those which are able to exist free for ever, and are parasitical only when the opportunity offers.

Entomologists regard the flea as a degraded fly. Certainly it is very much more degraded than the bird-borne Ornithomyia, with its subtle motions and instinct, its power of flight and social pastimes. The poor pulex has lost every trace of wings; nevertheless, in its fallen condition it has developed some remarkable qualities and saltatory powers, which give it a lower kind of glory; and, compared with another parasite with which it shares the human species, it is almost a noble insect. Darwin has some remarks about the smallness of the brain of an ant, assuming that this insect possesses a very high intelligence, but I doubt very much that the ant, which moves in a groove, is mentally the superior of the unsocial flea. The last is certainly the most teachable; and if fleas were generally domesticated and made pets of, probably there would be as many stories about their marvellous intelligence and fidelity to man as we now hear about our over-praised "friend" the dog.

With regard to size, the flea probably started on its downward course as a comparatively large insect, probably larger than the Ornithomyia. That insect has been able to maintain its existence, without dwindling like the Leptus into a mere speck, through the great modification in organs and instinct, which adapt it so beautifully to the feathery element in which it moves. The bush-tick, wingless from the beginning, and diverging in another direction, has probably been greatly increased in size by its parasitical habit; this seems proven by the fact, that as long as it is parasitical on nothing it remains small, but when able to fasten itself to an animal it rapidly developes to a great size. Again, the big globe of its abdomen is coriaceous and elastic, and is probably as devoid of sensation as a ball of india-rubber. The insect, being made fast by hooks and teeth to its victim, all efforts to remove it only increase the pain it causes; and animals that know it well do not attempt to rub, scratch, or bite it off, therefore the great size and the conspicuous colour of the tick are positive advantages to it. The flea, without the subtlety and highly-specialized organs of the Ornithomyia, or the stick-fast powers and leathery body of the Ixodes, can only escape its vigilant enemies by making itself invisible; hence every variation, i.e. increase in jumping-power and diminished bulk, tending towards this result, has been taken advantage of by natural selection.



CHAPTER XI

HUMBLE-BEES AND OTHER MATTERS.

Two humble-bees, Bombus thoracicus and B. violaceus, are found on the pampas; the first, with a primrose yellow thorax, and the extremity of the abdomen bright rufous, slightly resembles the English B. terrestris; the rarer species, which is a trifle smaller than the first, is of a uniform intense black, the body having the appearance of velvet, the wings being of a deep violaceous blue.

A census of the humble-bees in any garden or field always shows that the yellow bees outnumber the black in the proportion of about seven to one; and I have also found their nests for many years in the same proportion; about seven nests of the yellow to one nest of the black species. In habits they are almost identical, and when two species so closely allied are found inhabiting the same locality, it is only reasonable to infer that one possesses some advantage over the other, and that the least favoured species will eventually disappear. In this case, where one so greatly outnumbers the other, it might be thought that the rarer species is dying out, or that, on the contrary, it is a new-comer destined to supplant the older more numerous species. Yet, during the twenty years I have observed them, there has occurred no change in their relative positions; though both have greatly increased in numbers during that time, owing to the spread of cultivation. And yet it would scarcely be too much to expect some marked change in a period so long as that, even through the slow-working agency of natural selection; for it is not as if there had been an exact balance of power between them. In the same period of time I have seen several species, once common, almost or quite disappear, while others, very low down as to numbers, have been exalted to the first rank. In insect life especially, these changes have been numerous, rapid, and widespread.

In the district where, as a boy, I chased and caught tinamous, and also chased ostriches, but failed to catch them, the continued presence of our two humble-bees, sucking the same flowers and making their nests in the same situations, has remained a puzzle to my mind.

The site of the nest is usually a slight depression in the soil in the shelter of a cardoon bush. The bees deepen the hollow by burrowing in the earth; and when the spring foliage sheltering it withers up, they construct a dome-shaped covering of small sticks, thorns, and leaves bitten into extremely minute pieces. They sometimes take possession of a small hole or cavity in the ground, and save themselves the labour of excavation.

Their architecture closely resembles that of B. terrestris. They make rudely-shaped oval honey-cells, varying from half an inch to an inch and a half in length, the smaller ones being the first made; later in the season the old cocoons are utilized for storing honey. The wax is chocolate-coloured, and almost the only difference I can find in the economy of the two species is that the black bee uses a large quantity of wax in plastering the interior of its nest. The egg-cell of the yellow bee always contains from twelve to sixteen eggs; that of the black bee from ten to fourteen; and the eggs of this species are the largest though the bee is smallest. At the entrance on the edge of the mound one bee is usually stationed, and, when approached, it hums a shrill challenge, and throws itself into a menacing attitude. The sting is exceedingly painful.

One summer I was so fortunate as to discover two nests of the two kinds within twelve yards of each other, and I resolved to watch them very carefully, in order to see whether the two species ever came into collision, as sometimes happens with ants of different species living close together. Several times I saw a yellow bee leave its own nest and hover round or settle on the neighbouring one, upon which the sentinel black bee would attack and drive it off. One day, while watching, I was delighted to see a yellow bee actually enter its neighbour's nest, the sentinel being off duty. In about five minutes' time it came out again and flew away unmolested. I concluded from this that humble-bees, like their relations of the hive, occasionally plunder each other's sweets. On another occasion I found a black bee dead at the entrance of the yellow bees' nest; doubtless this individual had been caught in the act of stealing honey, and, after it had been stung to death, it had been dragged out and left there as a warning to others with like felonious intentions.

There is one striking difference between the two species. The yellow bee is inodorous; the black bee, when angry and attacking, emits an exceedingly powerful odour: curiously enough, this smell is identical in character with that made when angry by all the wasps of the South American genus Pepris—dark blue wasps with red wings. This odour at first produces a stinging sensation on the nerve of smell, but when inhaled in large measure becomes very nauseating. On one occasion, while I was opening a nest, several of the bees buzzing round my head and thrusting their stings through the veil I wore for protection, gave out so pungent a smell that I found it unendurable, and was compelled to retreat.

It seems strange that a species armed with a venomous sting and possessing the fierce courage of the humble-bee should also have this repulsive odour for a protection. It is, in fact, as incongruous as it would be were our soldiers provided with guns and swords first, and after with phials of assafoatida to be uncorked in the face of an enemy.

Why, or how, animals came to be possessed of the power of emitting pestiferous odours is a mystery; we only see that natural selection has, in some mstances, chiefly among insects, taken advantage of it to furnish some of the weaker, more unprotected species with a means of escape from their enemies. The most stinking example I know is that of a large hairy caterpillar I have found on dry wood in Patagonia, and which, when touched, emits an intensely nauseous effluvium. Happily it is very volatile, but while it lasts it is even more detestable than that of the skunk.

The skunk itself offers perhaps the one instance amongst the higher vertebrates of an animal in which all the original instincts of self-preservation have died out, giving place to this lower kind of protection. All the other members of the family it belongs to are cunning, swift of foot, and, when overtaken, fierce-tempered and well able to defend themselves with their powerful well-armed jaws.

For some occult reason they are provided with a gland charged with a malodorous secretion; and out of this mysterious liquor Nature has elaborated the skunk's inglorious weapon. The skunk alone when attacked makes no attempt to escape or to defend itself by biting; but, thrown by its agitation into a violent convulsion, involuntarily discharges its foetid liquor into the face of an opponent. When this animal had once ceased to use so good a weapon as its teeth in defending itself, degenerating at the same time into a slow-moving creature, without fear and without cunning, the strength and vileness of its odour would be continually increased by the cumulative process of natural selection: and how effective the protection has become is shown by the abundance of the species throughout the whole American continent. It is lucky for mankind—especially for naturalists and sportsmen—that other species have not been improved in the same direction.

But what can we say of the common deer of the pampas (Cervus campestris), the male of which gives out an effluvium quite as far-reaching although not so abominable in character as that of the Mephitis? It comes in disagreeable whiffs to the human nostril when the perfumer of the wilderness is not even in sight. Yet it is not a protection; on the contrary, it is the reverse, and, like the dazzling white plumage so attractive to birds of prey, a direct disadvantage, informing all enemies for leagues around of its whereabouts. It is not, therefore, strange that wherever pumas are found, deer are never very abundant; the only wonder is that, like the ancient horse of America, they have not become extinct.

The gauchos of the pampas, however, give a reason for the powerful smell of the male deer; and, after some hesitation, I have determined to set it down here, for the reader to accept or reject, as he thinks proper. I neither believe nor disbelieve it; for although I do not put great faith in gaucho natural history, my own observations have not infrequently confirmed statements of theirs, which a sceptical person would have regarded as wild indeed. To give one instance: I heard a gaucho relate that while out riding he had been pursued for a considerable distance by a large spider; his hearers laughed at him for a romancer; but as I myself had been attacked and pursued, both when on foot and on horseback, by a large wolf-spider, common on the pampas, I did not join in the laugh. They say that the effluvium of C. campestris is abhorrent to snakes of all kinds, just as pyrethrum powder is to most insects, and even go so far as to describe its effect as fatal to them; according to this, the smell is therefore a protection to the deer. In places where venomous snakes are extremely abundant, as in the Sierra district on the southern pampas of Buenos Ayres, the gaucho frequently ties a strip of the male deer's skin, which retains its powerful odour for an indefinite time, round the neck of a valuable horse as a protection. It is certain that domestic animals are frequently lost here through snake-bites. The most common poisonous species—the Craspedo-cephalus alternatus, called Vivora de la Cruz in the vernacular—has neither bright colour nor warning rattle to keep off heavy hoofs, and is moreover of so sluggish a temperament that it will allow itself to be trodden on before stirring, with the result that its fangs are not infrequently struck into the nose or foot of browsing beast. Considering, then, the conditions in which C. campestris is placed—and it might also be supposed that venomous snakes have in past times been much more numerous than they are now—it is not impossible to believe that the powerful smell it emits has been made protective, especially when we see in other species how repulsive odours have been turned to account by the principle of natural selection.

After all, perhaps the wild naturalist of the pampas knows what he is about when he ties a strip of deer-skin to the neck of his steed and turns him loose to graze among the snakes.

The gaucho also affirms that the deer cherishes a wonderful animosity against snakes; that it becomes greatly excited when it sees one, and proceeds at once to destroy it; they say, by running round and round it in a circle, emitting its violent smell in larger measure, until the snake dies of suffocation. It is hard to believe that the effect can be so great; but that the deer is a snake hater and killer is certainly true: in North America, Ceylon, and other districts deer have been observed excitedly leaping on serpents, and killing them with their sharp cutting hoofs.



CHAPTER XII.

A NOBLE WASP.

(Monedula punctata.)

Naturalists, like kings and emperors, have their favourites, and as my zoological sympathies, which are wider than my knowledge, embrace all classes of beings, there are of course several insects for which I have a special regard; a few in each of the principal orders. My chief favourite among the hymenopteras is the one representative of the curious genus Monedula known in La Plata. It is handsome and has original habits, but it is specially interesting to me for another reason: I can remember the time when it was extremely rare on the pampas, so rare that in boyhood the sight of one used to be a great event to me; and I have watched its rapid increase year by year till it has come to be one of our commonest species. Its singular habits and intelligence give it a still better claim to notice. It is a big, showy, loud-buzzing insect, with pink head and legs, wings with brown reflections, and body encircled with alternate bands of black and pale gold, and has a preference for large composite flowers, on the honey of which it feeds. Its young is, however, an insect-eater; but the Monedula does not, like other burrowing or sand wasps, put away a store of insects or spiders, partially paralyzed, as a provision for the grub till it reaches the pupa state; it actually supplies the grub with fresh-caught insects as long as food is required, killing the prey it captures outright, and bringing it in to its young; so that its habits, in this particular, are more bird- than wasp-like.

The wasp lays its solitary egg at the extremity of a hole it excavates for itself on a bare hard piece of ground, and many holes are usually found close together. When the grub—for I have never been able to find more than one in a hole—has come out from the egg, the parent begins to bring in insects, carefully filling up the mouth of the hole with loose earth after every visit. Without this precaution, which entails a vast amount of labour, I do not believe one grub out of every fifty would survive, so overrun are these barren spots of ground used as breeding-places with hunting spiders, ants, and tiger-beetles. The grub is a voracious eater, but the diligent mother brings in as much as it can devour. I have often found as many as six or seven insects, apparently fresh killed, and not yet touched by the pampered little glutton, coiled up in the midst of them waiting for an appetite.

The Monedula is an adroit fly-catcher, for though it kills numbers of fire-flies and other insects, flies are always preferred, possibly because they are so little encumbered with wings, and are also more easily devoured. It occasionally captures insects on the wing, but the more usual method is to pounce down on its prey when it is at rest. At one time, before I had learnt their habits, I used frequently to be startled by two or three or more of these wasps rushing towards my face, and continuing hovering before it, loudly buzzing, attending me in my walks about the fields. The reason of this curious proceeding is that the Monedula preys largely on stinging flies, having learnt from experience that the stinging fly will generally neglect its own safety when it has once fastened on a good spot to draw blood from. When a man or horse stands perfectly motionless the wasps take no notice, but the moment any movement is made of hand, tail, or stamping hoof, they rush to the rescue, expecting to find a stinging fly. On the other hand, the horse has learnt to know and value this fly-scourge, and will stand very quietly with half a dozen loud Avasps hovering in an alarming manner close to his head, well knowing that every fly that settles on him will be instantly snatched away, and that the boisterous Monedula is a better protection even than the tail—which, by the way, the horse wears very long in Buenos Ayres.

I have, in conclusion, to relate an incident I onco witnessed, and which does not show the Monedula in a very amiable light. I was leaning over a gate watching one of these wasps feeding on a sunflower. A small leaf-cutting bee was hurrying about with its shrill busy hum in the vicinity, and in due time came to the sunflower and settled on it. The Monedula became irritated, possibly at the shrill voice and bustling manner of its neighbour, and, after watching it for a few moments on the flower, deliberately rushed at and drove it off. The leaf-cutter quickly returned, however—for bees are always extremely averse to leaving a flower unexplored—but was again driven away with threats and demonstrations on the part of the Monedula. The little thing went off and sunned itself on a leaf for a time, then returned to the flower, only to be instantly ejected again. Other attempts were made, but the big wasp now kept a jealous watch on its neighbour's movements, and would not allow it to come within several inches of the flower without throwing itself into a threatening attitude. The defeated bee retired to sun itself once more, apparently determined to wait for the big tyrant to go away; but the other seemed to know what was wanted, and spitefully made up its mind to stay where it was. The leaf-cutter then gave up the contest. Suddenly rising up into the air, it hovered, hawk-like, above the Monedula for a moment, then pounced down on its back, and clung there, furiously biting, until its animosity was thoroughly appeased; then it flew off, leaving the other master of the field certainly, but greatly discomposed, and perhaps seriously injured about the base of the wings. I was rather surprised that they were not cut quite off, for a leaf-cutting bee can use its teeth as deftly as a tailor can his shears.

Doubtless to bees, as to men, revenge is sweeter than honey. But, in the face of mental science, can a creature as low down in the scale of organization as a leaf-cutting bee be credited with anything so intelligent and emotional as deliberate anger and revenge, "which implies the need of retaliation to satisfy the feelings of the person (or bee) offended?" According to Bain (Mental and Moral Science) only the highest animals—stags and bulls he mentions-can be credited with the developed form of anger, which, he describes as an excitement caused by pain, reaching the centres of activity, and containing an impulse knowingly to inflict suffering on another sentient being. Here, if man only is meant, the spark is perhaps accounted for, but not the barrel of gunpowder. The explosive material is, however, found in the breast of nearly every living creature. The bull—ranking high according to Bain, though I myself should place him nearly on a level mentally with the majority of the lower animals, both vertebrate and insect—is capable of a wrath exceeding that of Achilles; and yet the fact that a red rag can manifestly have no associations, personal or political, for the bull, shows how uniutcllectual his anger must be. Another instance of misdirected anger in nature, not quite so familiar .as that of the bull and red rag, is used as an illustration by one of the prophets: "My heritage is unto me as a speckled bird; the birds round, about are against it." I have frequently seen the birds of a thicket gather round some singularly marked accidental visitor, and finally drive him with great anger from the neighbourhood. Possibly association comes in a little here, since any bird, even a small one, strikingly coloured or marked, might be looked on as a bird of prey.

The flesh-fly laying its eggs on the carrion-flower is only a striking instance of the mistakes all instincts are liable to, never more markedly than in the inherited tendency to fits of frenzied excitement: the feeling is frequently excited by the wrong object, and explodes at inopportune moments.



CHAPTER XIII.

NATURE'S NIGHT LIGHTS.

(Remarks about Fireflies and other matters.)

It was formerly supposed that the light of the firefly (in any family possessing the luminous power) was a safeguard against the attacks of other insects, rapacious and nocturnal in their habits. This was Kirby and Spence's notion, but it might just as well be Pliny's for all the attention it would receive from modern entomologists: just at present any observer who lived in the pre-Darwin days is regarded as one of the ancients. The reasons given for the notion or theory in the celebrated Introduction to Entomology were not conclusive; nevertheless it was not an improbable supposition of the authors'; while the theory which has taken its place in recent zoological writings seems in every way even less satisfactory.

Let us first examine the antiquated theory, as it must now be called. By bringing a raptorial insect and a firefly together, we find that the flashing light of the latter does actually scare away the former, and is therefore, for the moment, a protection as effectual as the camp-fire the traveller lights in a district abounding with beasts of prey. Notwithstanding this fact, and assuming that we have here the whole reason of the existence of the light-emitting power, a study of the firefly's habits compels us to believe that the insect would be just as well off without the power as with it. Probably it experiences some pleasure in emitting flashes of light during its evening pastimes, but this could scarcely be considered an advantage in its struggle for existence, and it certainly does not account for the possession of the faculty.

About the habits of Pyrophorus, the large tropical firefly which has the seat of its luminosity on the upper surface of the thorax, nothing definite appears to be known; but it has been said that this instinct is altogether nocturnal. The Pyrophorus is only found in the sub-tropical portion of the Argentine country, and I have never met with it. With the widely-separated Cratomorphus, and the tortoise-shaped Aspisoma, which emit the light from the abdomen, I am familiar; one species of Cratomorphus—a long slender insect with yellow wing-cases marked with two parallel black lines—is "the firefly" known to every one and excessively abundant in the southern countries of La Plata. This insect is strictly diurnal in its habits—as much so, in fact, as diurnal butterflies. They are seen flying about, wooing their mates, and feeding on composite and umbelliferous flowers at all hours of the day, and are as active as wasps during the full glare of noon. Birds do not feed on them, owing to the disagreeable odour, resembling that of phosphorus, they emit, and probably because they are to be uneatable; but their insect enemies are not so squeamish, and devour them readily, just as they also do the blister-fly, which one would imagine a morsel fitted to disagree with any stomach. One of their enemies is the Monedula wasp; another, a fly, of the rapacious Asilidas family; and this fly is also a wasp in appearance, having a purple body and bright red wings, like a Pepris, and this mimetic resemblance doubtless serves it as a protection against birds. A majority of raptorial insects are, however, nocturnal, and from all these enemies that go about under cover of night, the firefly, as Kirby and Spence rightly conjectured, protects itself, or rather is involuntarily protected, by means of its frequent flashing light. We are thus forced to the conclusion that, while the common house fly and many other diurnal insects spend a considerable portion of the daylight in purely sportive exercises, the firefly, possessing in its light a protection from nocturnal enemies, puts off its pastimes until the evening; then, when its carnival of two or three hours' duration is over, retires also to rest, putting out its candle, and so exposing itself to the dangers which surround other diurnal species during the hours of darkness. I have spoken of the firefly's pastimes advisedly, for I have really never been able to detect it doing anything in the evening beyond flitting aimlessly about, like house flies in a room, hovering and revolving in company by the hour, apparently for amusement. Thus, the more closely we look at the facts, the more unsatisfactory does the explanation seem. That the firefly should have become possessed of so elaborate a machinery, producing incidentally such splendid results, merely as a protection against one set of enemies for a portion only of the period during which they are active, is altogether incredible.

The current theory, which we owe to Belt, is a prettier one. Certain insects (also certain Batrachians, reptiles, &c.) are unpalatable to the rapacious kinds; it is therefore a direct advantage to these unpalatable species to be distinguishable from all the persecuted, and the more conspicuous and well-known they are, the less likely are they to be mistaken by birds, insectivorous mammals, &c., for eatable kinds and caught or injured. Hence we find that many such species have acquired for their protection very brilliant or strongly-contrasted colours—warning colours—which insect-eaters come to know.

The firefly, a soft-bodied, slow-flying insect, is easily caught and injured, but it is not fit for food, and, therefore, says the theory, lest it should be injured or killed by mistake, it has a fiery spark to warn enemies—-birds, bats, and rapacious insects—that it is uneatable.

The theory of warning colours is an excellent one, but it has been pushed too far. We have seen that one of the most common fireflies is diurnal in habits, or, at any rate, that it performs all the important business of its life by day, when it has neither bright colour nor light to warn its bird enemies; and out of every hundred species of insect-eating birds at least ninety-nine are diurnal. Raptorial insects, as I have said, feed freely on fireflies, so that the supposed warning is not for them, and it would be hard to believe that the magnificent display made by luminous insects is useful only in preventing accidental injuries to them from a few crepuscular bats and goatsuckers. And to believe even this we should first have to assume that bats and goatsuckers are differently constituted from all other creatures; for in other animals—insects, birds, and mammalians—the appearance of fire by night seems to confuse and frighten, but it certainly cannot be said to warn, in the sense in which that word is used when we speak of the brilliant colours of some butterflies, or even of the gestures of some venomous snakes, and of the sounds they emit.

Thus we can see that, while the old theory of Kirby and Spence had some facts to support it, the one now in vogue is purely fanciful. Until some better suggestion is made, it would perhaps be as well to consider the luminous organ as having "no very close and direct relation to present habits of life." About their present habits, however, especially their crepuscular habits, there is yet much to learn. One thing I have observed in them has always seemed very strange to me. Occasionally an individual insect is seen shining with a very large and steady light, or with a light which very gradually decreases and increases in power, and at such times it is less active than at others, remaining for long intervals motionless on the leaves, or moving with a very slow flight. In South America a firefly displaying this abnormal splendour is said to be dying, and it is easy to imagine how such a notion originated. The belief is, however, erroneous, for sometimes, on very rare occasions, all the insects in one place are simultaneously affected in the same way, and at such times they mass themselves together in myriads, as if for migration, or for some other great purpose. Mr. Bigg-Wither, in South Brazil, and D'Albertis, in New Guinea, noticed these firefly gatherings; I also once had the rare good fortune to witness a phenomenon of the kind on a very grand scale. Riding on the pampas one dark evening an hour after sunset, and passing from high ground overgrown with giant thistles to a low plain covered with long grass, bordering a stream of water, I found it all ablaze with myriads of fireflies. I noticed that all the insects gave out an exceptionally large, brilliant light, which shone almost steadily. The long grass was thickly studded with them, while they literally swarmed in the air, all moving up the valley with a singularly slow and languid flight. When I galloped down into this river of phosphorescent fire, my horse plunged and snorted with alarm. I succeeded at length in quieting him, and then rode slowly through, compelled to keep my mouth and eyes closed, so thickly did the insects rain on to my face. The air was laden with the sickening phosphorous smell they emit, but when I had once got free of the broad fiery zone, stretching away on either hand for miles along the moist valley, I stood still and gazed back for some time on a scene the most wonderful and enchanting I have ever witnessed.

The fascinating and confusing effect which the appearance of fire at night has on animals is a most interesting subject; and although it is not probable that anything very fresh remains to be said about it, I am tempted to add here the results of my own experience.

When travelling by night, I have frequently been struck with the behaviour of my horse at the sight of natural fire, or appearance of fire, always so different from that caused by the sight of fire artificially created. The steady gleam from the open window or door of a distant house, or even the unsteady wind-tossed flame of some lonely camp-fire, has only served to rouse a fresh spirit in him and the desire to reach it; whereas those infrequent displays of fire which nature exhibits, such as lightning, or the ignis fatuus, or even a cloud of fireflies, has always produced a disquieting effect. Experience has evidently taught the domestic horse to distinguish a light kindled by man from all others; and, knowing its character, he is just as well able as his rider to go towards it without experiencing that confusion of mind caused by a glare in the darkness, the origin and nature of which is a mystery. The artificially-lighted fire is to the horse only the possible goal of the journey, and is associated with the thought of rest and food. Wild animals, as a rule, at any rate in thinly-settled districts, do not know the meaning of any fire; it only excites curiosity and fear in them; and they are most disturbed at the sight of fires made by man, which are brighter and steadier than most natural fires. We can understand this sensation in animals, since we ourselves experience a similar one (although in a less degree and not associated with fear) in the effect which mere brightness has on us, both by day and night.

On riding across the monotonous grey Patagonian uplands, where often for hours one sees not the faintest tinge of bright colour, the intense glowing crimson of a cactus-fruit, or the broad shining white bosom of the Patagonian eagle-buzzard (Buteo erythronotus), perched on the summit of a distant bush, has had a strangely fascinating effect on me, so that I have been unable to take my eyes off it as long as it continued before me. Or in passing through extensive desolate marshes, the dazzling white plumage of a stationary egret has exercised the same attraction. At night we experience the sensation in a greater degree, when the silver sheen of the moon makes a broad path on the water; or when a meteor leaves a glowing track across the sky; while a still more familiar instance is seen in the powerful attraction on the sight of glowing embers in a darkened room. The mere brightness, or vividness of the contrast, fascinates the mind; but the effect on man is comparatively weak, owing to his fiery education and to his familiarity with brilliant dyes artificially obtained from nature. How strong this attraction of mere brightness, even where there is no mystery about it, is to wild animals is shown by birds of prey almost invariably singling out white or bright-plumaged birds for attack where bright and sober-coloured kinds are mingled together. By night the attraction is immeasurably greater than by day, and the light of a fire steadily gazed at quickly confuses the mind. The fires which, travellers make for their protection actually serve to attract the beasts of prey, but the confusion and fear caused by the bright glare makes it safe for the traveller to lie down and sleep in the light. Mammals do not lose their heads altogether, because they are walking on firm ground where muscular exertion and an exercise of judgment are necessary at every step; whereas birds floating buoyantly and with little effort through the air are quickly bewildered. Incredible numbers of migratory birds kill them-selves by dashing against the windows of lighthouses; on bright moonlight nights the voyagers are comparatively safe; but during dark cloudy weather the slaughter is very great; over six hundred birds were killed by striking a lighthouse in Central America in a single night. On insects the effect is the same as on the higher animals: on the ground they are attracted by the light, but keep, like wolves and tigers, at a safe distance from it; when rushing through the air and unable to keep their eyes from it they fly into it, or else revolve about it, until, coming too close, their wings are singed.

I find that when I am on horseback, going at a swinging gallop, a bright light affects me far more powerfully than when I am trudging along on foot. A person mounted on a bicycle and speeding over a level plain on a dark night, with nothing to guide him except the idea of the direction in his mind, would be to some extent in the position of the migratory bird. An exceptionally brilliant ignis fatuus flying before him would affect him as the gleam of a lamp placed high above the surface affects the migrants: he would not be able to keep his eyes from it, but would quickly lose the sense of direction, and probably end his career much as the bird does, by breaking his machine and perhaps his bones against some unseen obstruction in the way.



CHAPTER XIV.

FACTS AND THOUGHTS ABOUT SPIDERS.

Some time ago, while turning over a quantity of rubbish in a little-used room, I disturbed a large black spider. Rushing forth, just in time to save itself from destruction through the capsizing of a pile of books, it paused for one moment, took a swift comprehensive glance at the position, then scuttled away across the floor, and was lost in an obscure corner of the room. This incident served to remind me of a fact I was nearly forgetting, that England is not a spiderless country. A foreigner, however intelligent, coming from warmer regions, might very easily make that mistake. In Buenos Ayres, the land of my nativity, earth teems with these interesting little creatures. They abound in and on the water, they swarm in the grass and herbage, which everywhere glistens with the silvery veil they spin over it. Indeed it is scarcely an exaggeration to say that there is an atmosphere of spiders, for they are always floating about invisible in the air; their filmy threads are unfelt when they fly against you; and often enough you are not even aware of the little arrested aeronaut hurrying over your face with feet lighter than the lightest thistledown.

It is somewhat strange that although, where other tribes of living creatures are concerned, I am something of a naturalist, spiders I have always observed and admired in a non-scientific spirit, and this must be my excuse for mentioning the habits of some spiders without giving their specific names—an omission always vexing to the severely-technical naturalist. They have ministered to the love of the beautiful, the grotesque, and the marvellous in me; but I have never collected a spider, and if I wished to preserve one should not know how to do it. I have been "familiar with the face" of these monsters so long that I have even learnt to love them; and I believe that if Emerson rightly predicts that spiders are amongst the things to be expelled from earth by the perfected man of the future, then a great charm and element of interest will be lost to nature. Though loving them, I cannot, of course, feel the same degree of affection towards all the members of so various a family. The fairy gossamer, scarce seen, a creature of wind and sunshine; the gem-like Epeira in the centre of its Starry web; even the terrestrial Salticus, with its puma-like strategy, certainly appeal more to our aesthetic feelings than does the slow heavy Mygale, looking at a distance of twenty yards away, as he approaches you, like a gigantic cockroach mounted on stilts. The rash fury with which the female wolf-spider defends her young is very admirable; but the admiration she excites is mingled with other feelings when we remember that the brave mother proves to her consort a cruel and cannibal spouse.

Possibly my affection for spiders is due in a great measure to the compassion I have always felt for them. Pity, 'tis said, is akin to love; and who can help experiencing that tender emotion that considers the heavy affliction nature has laid on the spiders in compensation for the paltry drop of venom with which she, unasked, endowed them! And here, of course, I am alluding to the wasps. These insects, with a refinement of cruelty, prefer not to kill their victims outright, but merely maim them, then house them in cells where the grubs can vivisect them at leisure. This is one of those revolting facts the fastidious soul cannot escape from in warm climates; for in and out of open windows and doors, all day long, all the summer through, comes the busy beautiful mason-wasp. A long body, wonderfully slim at the waist, bright yellow legs and thorax, and a dark crimson abdomen,—what object can be prettier to look at? But in her life this wasp is not beautiful. At home in summer they were the pests of my life, for nothing would serve to keep them out. One day, while we were seated at dinner, a clay nest, which a wasp had succeeded in completing unobserved, detached itself from the ceiling and fell with a crash on to the table, where it was shattered to pieces, scattering a shower of green half-living spiders round it. I shall never forget the feeling of intense repugnance I experienced at the sight, coupled with detestation of the pretty but cruel little architect. There is, amongst our wasps, even a more accomplished spider-scourge than the mason-wasp, and I will here give a brief account of its habits. On the grassy pampas, dry bare spots of soil are resorted to by a class of spiders that either make or take little holes in the ground to reside in, and from which they rush forth to seize their prey. They also frequently sit inside their dens and patiently wait there for the intrusion of some bungling insect. Now, in summer, to a dry spot of ground like this, comes a small wasp, scarcely longer than a blue-bottle fly, body and wings of a deep shining purplish blue colour, with only a white mark like a collar on the thorax. It flirts its blue wings, hurrying about here and there, and is extremely active, and of a slender graceful figure—the type of an assassin. It visits and explores every crack and hole in the ground, and, if you watch it attentively, you will at length see it, on arriving at a hole, give a little start backwards. It knows that a spider lies concealed within. Presently, having apparently matured a plan of attack, it disappears into the hole and remains there for some time. Then, just when you are beginning to think that the little blue explorer has been trapped, out it rushes, flying in terror, apparently, from the spider who issues close behind in hot pursuit; but, before they are three inches away from the hole, quick as lightning the wasp turns on its follower, and the two become locked together in a deadly embrace. Looking like one insect, they spin rapidly round for a few moments, then up springs the wasp—victorious. The wretched victim is not dead; its legs move a little, but its soft body is paralyzed, and lies collapsed, flabby, and powerless as a stranded jellyfish. And this is the invariable result of every such conflict. In other classes of beings, even the weakest hunted thing occasionally succeeds in inflicting pain on its persecutor, and the small trembling mouse, unable to save itself, can sometimes make the cat shriek with paiu; but there is no weak spot in the wasp's armour, no fatal error of judgment, not even an accident, ever to save the wretched victim from its fate. And now comes the most iniquitous part of the proceeding. When the wasp has sufficiently rested after the struggle, it deliberately drags the disabled spider back into its own hole, and, having packed it away at the extremity, lays an egg alongside of it, then, coming out again, gathers dust and rubbish with which it fills up and obliterates the hole; and, having thus concluded its Machiavellian task, it flies cheerfully off in quest of another victim.

The extensive Epeira family supply the mason-wasps and other spider-killers with the majority of their victims. These spiders have soft, plump, succulent bodies like pats of butter; they inhabit trees and bushes chiefly, where their geometric webs-betray their whereabouts; they are timid, comparatively innocuous, and reluctant to quit the shelter of their green bower, made of a rolled-up leaf; so that there are many reasons why they should be persecuted. They exhibit a great variety of curious forms; many are also very richly coloured; but even their brightest hues—orange, silver, scarlet—have not been given without regard to the colouring of their surroundings. Green-leafed bushes arc frequented by vividly green Epeiras, but the imitative resemblance does not quite end here. The green spider's method of escape, when the bush is roughly shaken, is to drop itself down on the earth, where it lies simulating death. In falling, it drops just as a green leaf would drop, that is, not quite so rapidly as a round, solid body like a beetle or spider. Now in the bushes there is another Epeira, in size and form like the last, but differing in colour; for instead of a vivid green, it is of a faded yellowish white—the exact hue of a dead, dried-up leaf. This spider, when it lets itself drop—for it has the same protective habit as the other—falls not so rapidly as a green freshly broken off leaf or as the green spider would fall, but with a slower motion, precisely like a leaf withered up till it has become almost light as a feather. It is not difficult to imagine how this comes about: either a thicker line, or a greater stiffness or tenacity of the viscid fluid composing the web and attached to the point the spider drops from, causes one to fall slower than the other. But how many tentative variations in the stiffness of the web material must there have been before the precise degree was attained enabling the two distinct species, differing in colour, to complete their resemblance to falling leaves—a fresh green leaf in one case and a dead, withered leaf in the other!