Read Ebook: Insect life: Souvenirs of a naturalist by Fabre Jean Henri Merrifield F Editor Parker M Prendergast Illustrator Roberts Margaret Translator

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But my ambition was far from satisfied. It was not enough to know ravisher and prey: I wanted the larva for which all this rich store was laid up. After exhausting the first vein of Buprestis I hastened to make new excavations. Digging down more carefully I finally discovered two larvae, which completed the good fortune of this campaign. In less than an hour I turned over three haunts of the Cerceris, and my booty was some fifteen whole Buprestids with fragments of a yet greater number. I calculated, and I believe it fell far short of the truth, that there were twenty-five nests in this garden, a fact representing an immense number of buried Buprestids. What must it be, I said to myself, in localities where in a few hours I have caught as many as sixty Cerceris on blossoming garlic, with nests most probably near, and no doubt provisioned quite as abundantly! Imagination, backed by probability, showed me underground, within a small space, B. bifasciata by thousands, although I who have observed the entomology of our parts for over thirty years have never noticed a single one. Once only, perhaps twenty years ago, did I see, sticking in a hole of an ancient oak, the abdomen and elytra of this insect. This fact was a ray of light, for it told me that the larva of B. bifasciata must live in the wood of the oak, and entirely explained the abundance of this beetle in a district where the forests consist chiefly of that tree. As Cerceris bupresticida is rare on the clayey hills of the latter stretch of country compared to the sandy plains where grows Pinus maritima, it became an interesting question whether this Hymenopteron when it inhabits the pine region provisions its nest as it does in the oak district. I had good reason to believe that it did not, and you will soon see with some surprise how exquisite is the entomological tact of our Cerceris in her choice of the numerous kind of Buprestids.

Let us hasten to the pine region to taste new pleasures. The spot to be explored is a garden belonging to a property in the midst of forests of the maritime pines. The haunts of the Cerceris were soon recognised; they were exclusively found in the main paths, where the beaten and compact soil offered the burrowing Hymenoptera sufficient solidity for the construction of their subterranean dwellings. I visited some twenty, and I did it, I may say, by the sweat of my brow. It is a very laborious kind of exploration, for the nests and provisions are only found at the depth of one foot, so that it is necessary to invest the place by a line of square trenches seven or eight inches from the mouth of the hole, first inserting a stalk of grass in the gallery by way of clue. One must sap with a garden spade, so that the central clod, thoroughly detached all round, may be raised in one piece, then reversed on the ground and broken up carefully. Such is the manoeuvre which I found successful. You would have shared our enthusiasm at the sight of the beautiful species of Buprestis which this new style of research revealed to our eager gaze. You ought to have heard our exclamations as each time the clod was reversed, new treasures were revealed rendered yet more brilliant by the hot sun, or when we discovered the larvae of every age attached to their prey, or the cocoons of these larvae incrusted with copper, bronze, and emerald. I who had been for three or four times ten years, alas! a practical entomologist had never beheld such an enchanting sight or had had such good fortune. We only wanted you to double our enjoyment. With ever increasing admiration we dwelt now on the brilliant Coleoptera and now on the marvellous sagacity of the Cerceris which had buried and laid them up for food. Can you believe it? Out of more than 400 beetles dug up, there was not one which did not belong to the old genus Buprestis! Our Hymenopteron had not committed the smallest error. How much there is to learn from this intelligent industry in so small an insect! What value Latreille would have attached to the vote of this Cerceris in favour of the natural system!

Let us pass on to the various contrivances of the Cerceris in making and provisioning her nest. I have already said that she chooses ground whose surface is beaten, compact, and solid. I should add that this ground must be dry and in full sunshine. This choice shows an intelligence, or, if you like, an instinct, which one is tempted to believe is the result of experience. Crumbly earth or mere sand would of course be easier to work, but then how construct an orifice which will remain wide open for ingress and exit, and a gallery whose walls will not constantly fall in, yield, and become blocked by the least rain? The choice is therefore both reasonable and perfectly well calculated.

Our burrowing Hymenopteron hollows her gallery with her mandibles and front tarsi, which accordingly are furnished with stiff points to act as rakes. The orifice must not only have the diameter of the miner's body, but be able to admit a prey of larger bulk. This shows admirable forethought. As the Cerceris digs deeper she brings out the rubbish, and this makes the heap which I compared to a tiny molehill. The gallery is not vertical, as this would have exposed it to be filled up by wind or other causes. Not far from the starting-point it makes an angle; its length is from seven to eight inches. At the far end the industrious mother establishes the cradle of her progeny. Five cells, separate and independent of one another, are hollowed in the shape and nearly of the size of an olive; within they are solid and polished. Each can contain three Buprestids, the ordinary allowance for a larva. The Cerceris lays an egg amid the three victims, and then stops up the gallery with earth, so that when once the provisions for the brood are laid in, the cells have no communication with the outside.

Cerceris bupresticida must be an indefatigable, daring, and skilful huntress. The cleanness, the freshness of the beetles which she buries in her den testify that they are seized just as they emerge from the wooden galleries where their final metamorphosis takes place. But what inconceivable instinct urges a creature that lives solely on the nectar of flowers to seek amid a thousand difficulties animal food for carnivorous offspring, which it will never see, and to post itself on trees quite unlike one another, which hide deep in their trunks the insects which are to fall her victims? What entomological tact, yet more inconceivable, makes her lay down a strict law to select them in a single generic group, and to catch species differing very considerably in size, shape, and colour? You observe how unlike are Buprestis biguttata, with its slender long body and dark colour; B. octoguttata, oval-oblong, with great stains of a beautiful yellow on a blue or green ground; and B. micans, three or four times the size of B. biguttata, with a splendid metallic greeny gold.

There is another very singular fact in the manoeuvres of our assassin of Buprestids. The buried ones, like those which I have seized in the grasp of their murderers, give no sign of life, and are unquestionably quite dead, yet, as I observed with surprise, no matter when they are dug up, not only do they keep all their freshness of colour, but every bit of them--feet, antennae, palpi, and the membranes which unite the various parts of their bodies--is perfectly supple and flexible. At first one supposes the explanation, as far as concerns the buried ones, to be in the coolness of the ground, and absence of air and light, and for those taken from their murderers, in the very recent date of death. But observe that after my explorations, having isolated in cones of paper the numerous Buprestids dug up, I have often left them over thirty-six hours before pinning them out. And yet, notwithstanding the dryness and great heat of July, I have always found the same flexibility in the joints. More than this, after that lapse of time, I have dissected several, and their viscerae were as perfectly preserved as if I had used my scalpel on the live insect. Now, long experience has taught me that even in a beetle of this size, when twelve hours have passed in summer after its death, the interior organs are either dried up or corrupted so that it is impossible to be sure of form or structure. There is some peculiarity about Buprestids put to death by the Cerceris which prevents corruption or desiccation for a week, or perhaps two. But what is this peculiarity?

To explain this wonderful preservation which makes an insect dead for several weeks into a piece of game not even high, but, on the contrary, as fresh as when first caught, and that during the greatest heat of summer, the skilful historian of Cerceris bupresticida supposes that there must be an antiseptic liquid acting as do the preparations used in preserving anatomical specimens. This liquid can only be the poison injected by the Hymenopteron into the body of the victim. A minute globule of the venomous humour accompanying the dart or lancet, destined for this purpose, acts as a kind of pickle or antiseptic fluid to preserve the flesh on which the larva is to feed. But then how superior to our processes are those of the Cerceris with regard to preserved food! We salt or smoke or enclose in tins hermetically sealed provisions which remain eatable, to be sure, but which are far, very far from having the qualities of fresh meat. Sardines drowned in oil, Dutch smoked herrings, cod hardened into slabs by salt and sun,--can any of these sustain comparison with the same fish brought alive to the kitchen? For meat properly so-called it is still worse. Beyond salting and drying we have nothing which even for a short period can keep meat eatable. At the present time, after innumerable fruitless attempts of the most varied kind, special ships are equipped at great cost, which, furnished with powerful freezing apparatus, convey to us the flesh of sheep and oxen slaughtered in the Pampas of South America, frozen and kept from corruption by intense cold. How far superior is the method of the Cerceris, so rapid, so cheap, so expeditious! What lessons we should have to learn from such transcendental chemistry when an imperceptible drop of liquid poison renders in an instant the prey incorruptible! What am I saying?--incorruptible?--that is far from being all; the game is put into a condition which prevents desiccation, leaves their suppleness to the limbs, and maintains all the organs in pristine freshness, both the internal and external. In short, the Cerceris puts the insect into a state differing only from life by a corpse-like immobility.

Such is the conclusion arrived at by L?on Dufour before this incomprehensible marvel of the dead Buprestis untouched by corruption. An antiseptic fluid, incomparably superior to anything that human science could produce, would explain the mystery. He, the Master, skilful of the skilful, thoroughly used to most delicate anatomy; he who with magnifying glass and scalpel has scrutinised the whole circuit of entomology, leaving no corner unexplored; he, in short, for whom the organisation of insects has no secrets,--can advance no better conjecture than an antiseptic liquid to give at least a kind of explanation of a fact which leaves him confounded. Let me insist on this comparison between the instinct of the animal and the reason of the sage in order the better to demonstrate in due time the overwhelming superiority of the former.

I will add but a few words to the history of the C. bupresticida. This Hymenopteron, common in the Landes, as we have heard, seems to be rare in the department of Vaucluse. It is only at long intervals that I have met with it, in autumn, and always isolated specimens, on the spiny heads of Eryngium campestre, in the environs of Avignon or round Orange and Carpentras. In the latter spot, so favourable to burrowing hymenoptera, from its sandy soil of Mollasse, I had the good fortune, not indeed of being present at the exhumation of such entomological riches as L?on Dufour describes, but of finding some old nests which I feel certain belonged to Cerceris bupresticida, from the shape of the cocoons, the kind of provender stored up, and the existence of the Hymenopteron in the neighbourhood. These nests, hollowed in a very friable sandstone, called safre in those parts, were filled with remains of beetles, easily recognised, and consisting of detached wing-cases, empty corslets, and whole feet. Now these remains of the larva's feast all belonged to one species, and this was a Buprestis, Sphaenoptera geminata. Thus from the west to the east of France, from the department of the Landes to Vaucluse, the Cerceris remains faithful to its favourite prey; longitude does not affect its predilections, a hunter of Buprestids among the maritime pines of the ocean sand-hills, it is equally so amid the evergreen oaks and olives of Provence. The species is changed according to place, climate, and vegetation--causes influencing greatly the insect population, but the Cerceris keeps to its chosen genus, the Buprestis. For what strange reason? That is what I shall try to demonstrate.

CERCERIS TUBERCULATA

With my mind full of the great deeds of the Buprestis hunter, I watched for an opportunity of observing in my turn the labours of the Cerceris, and I watched so closely that finally I got my chance. True, it was not the Hymenopteron celebrated by Dufour, with such sumptuous provisions that when dug up they made one think of the powder from a nugget broken by the miner's pickaxe in some gold field: it was a closely related species, a giant brigand which contents itself with more modest prey--in short, Cerceris tuberculata or C. major, the largest and strongest of the genus.

It is not enough to choose this vertical situation; other precautions are taken to guard against the already advanced season. If some bit of hard sandstone project like a shelf, or if a hole the size of one's fist should have been hollowed naturally in the ground, it will be under this shelter or in this cavity that the gallery is made, a natural vestibule being thus added by the Cerceris to its own edifice. Although there is no kind of community among them, these insects like to associate in small parties, and I have always found their nests in groups of about ten, with orifices, though usually far apart, sometimes touching.

When the sun shines it is wonderful to see the ways of these hard-working miners. Some patiently extract bits of gravel from the bottom of a hole with their mandibles, and push out the heavy mass; others scratch the walls of their tunnel with the sharp rakes of their tarsi, forming a heap of rubbish which they sweep out backward, and send sliding down the steep incline in long dusty streams. It was these periodical sand waves thrown out of galleries in process of construction which betrayed my first Cerceris, and led to the discovery of the nests. Others, either weary, or having completed their hard task, rested and polished their antennae and wings under the natural caves which usually protect their dwelling, or else sat motionless at the mouth of their holes, only displaying their wide, square faces, barred with yellow and black. Others again were flying with a deep hum on the bushes near the cochineal oak, where the males, always on the watch near the burrows in process of construction, speedily join them. Couples form, often troubled by the arrival of a second male, which tries to supplant the happy possessor. The humming grows menacing, quarrels begin, and often both males roll in the dust until one acknowledges the superiority of his rival. Not far off the female waits with indifference the upshot of the struggle, accepting finally the male bestowed on her by the chances of the fight, and the pair fly out of sight to seek peace in some distant thicket. Here the part of the male ends. One half smaller than the females, they prowl about the burrows but never enter, and never take any part in the hard work of excavation, or that perhaps yet harder of provisioning the cells.

In a few days the galleries are ready, especially as after some repairs those of the preceding year are used again. Other Cerceris, as far as I know, have no fixed home, transmitted from one generation to another. True Bohemians, they establish themselves wherever the chances of their vagabond life may lead them, so long as the soil suits them. But C. tuberculata is faithful to her penates. The projecting shelf of sandstone used by its predecessors is used again; it hollows out the same layer of sand hollowed by its forbears, and, adding its own labour to theirs, obtains deep-seated retreats sometimes only visited with difficulty. The diameter of the galleries would admit a thumb, and the insect can move about easily, even when laden with the prey which we shall see it capture. Their direction is horizontal, from four to eight inches, then makes a sudden turn downward more or less obliquely, now in one direction, now in another. Except the horizontal part, and the angle of the tunnel, the direction seems to depend on the difficulties of the ground, as is proved by the windings and changes in the farthest part of this kind of canal, which is half a yard in length. At the far end are the cells, not numerous, and provisioned with five or six dead beetles. But let us leave the details of how a Cerceris builds, and turn to more wonderful facts.

The victim chosen to feed the larvae is a large weevil . One sees the captor arrive, carrying the victim between its feet, body to body, head to head. It alights heavily some way from the hole to complete the journey without the aid of wings, and drags the prey laboriously with its jaws, on ground if not vertical, at least very steeply inclined, which often results in sending captor and captive headlong to the bottom, but the indefatigable mother finally darts into her burrow, covered with dust, but with the prey of which she has never let go. If she does not find walking with such a burden easy, it is otherwise with her flight, which is surprisingly powerful, if one considers that the strong little creature is carrying a prey nearly as large as and heavier than herself. I have had the curiosity to weigh the Cerceris and her prey separately, and the first weighed 150 milligrammes, and the second about 250, almost double.

These weights speak eloquently for the vigorous huntress, and I never wearied of watching how swiftly and easily she resumed her flight, and rose out of sight with the game between her feet when approached too closely. But she did not always fly away, and then, though it was difficult to do so, and yet avoid hurting her, I would make her drop the prey by worrying and upsetting her with a straw. Then I would take possession of the victim, and the Cerceris, thus despoiled, would hunt about, go into her hole for a moment, come out, and resume the chase. In less than ten minutes the sharp-sighted insect would find a new victim, murder it and carry it off, not seldom to my profit. Eight times running have I stolen from the same individual; eight times did the indefatigable Cerceris resume her fruitless journey. Her perseverance tired out mine, and I let her keep the ninth capture.

Moreover, it is by no means the only one to hunt the long-nosed class of weevils. Many other Cerceris, according to their size, strength, and the chances of the chase, capture Curculionidae most various in genus, species, shape, and size. It has long been known that Cerceris arenaria feeds her young with similar food. I myself have found in its burrows Sitona lineata, S. tibialis, Cneorhinus hispidus, Brachyderes gracilis, Geonemus flabellipes, Otiorhynchus maleficus. Cerceris aurita is known to prey on Otiorhynchus raucus and Phytonomus punctatus. In the larder of Cerceris ferreri I saw Phytonomus murinus, P. punctatus, Sitona lineata, Cneorhinus hispidus, Rhynchites betuleti. This weevil, which rolls up vine leaves into the shape of cigars, is sometimes of a superb metallic blue, but more usually of a splendid golden copper. I have found as many as seven of these brilliant insects laid up in one cell, and the gorgeous colours of the little heap might almost bear comparison with the jewels buried by the huntress of the Buprestids. Other species, especially the weaker, hunt smaller game, the lesser size being compensated by numbers. Thus, Cerceris quadricincta heaps in each cell some thirty Apion gravidum, but does not disdain on occasion bigger weevils, such as Sitona lineata, Phytonomus murinus. Cerceris labiata also lays up small species. Finally, the smallest Cerceris in my part of France, C. julii, hunts the least weevils, Apion gravidum and Bruchus granarius, game proportioned to its own size. To end this list of provender, let us add that some Cerceris follow other gastronomic laws, and bring up their families on Hymenoptera. Such is C. ornata. These tastes being alien to our subject, let us pass on.

We see that out of eight species of Cerceris which lay up Coleoptera as food, seven hunt weevils and one Buprestids. What singular reason confines the chase of these Hymenoptera within such narrow limits? What are the motives of such an exclusive selection? What internal likeness is there between the Buprestids and the weevils, outwardly quite dissimilar, that both should become food for carnivorous and nearly related larvae? No doubt between such and such a victim there are differences as to taste and nutritive qualities which the larvae thoroughly appreciate, but there must be a far graver reason than these gastronomic considerations to explain these strange predilections.

After all that has been so admirably said by L?on Dufour on the long and marvellous preservation of the insects destined as food for the carnivorous larvae, it is needless to say that the weevils which I dug up, as well as those taken from between the feet of their murderer, were perfectly fresh, though permanently motionless. Freshness of colour, suppleness of the membranes and smallest articulations, normal condition of the viscera, all combine to make one doubt whether the inert body under one's eyes can really be a corpse, all the more that even under the magnifying glass it is impossible to perceive the smallest wound; and in spite of one's self one expects every moment to see the insect move and walk. Yet more, in weather so hot that insects which had died naturally would in a few hours have become dried up and crumbly, or again in damp weather which would with equal rapidity have made them decay and grow mouldy. I have kept specimens in glass tubes or cones of paper over a month with no precautions, and wonderful to say, after all this length of time, the intestines were as fresh as ever, and I found dissection as easy as if the creatures were alive. No, in presence of such facts one cannot talk of an antiseptic, and believe in real death; life is still there--life latent and passive--vegetative life. It alone, struggling successfully for a time against the destructive invasion of chemical forces, can thus preserve the organism from decomposition. Life is still there, but without motion, and we have under our eyes such a marvel as chloroform or ether might produce--a marvel caused by the mysterious laws of the nervous system.

The functions of this vegetative life are slackened and troubled no doubt, but still they are feebly exercised. I have the proof of this in that action of the viscera which takes place normally and at intervals in the weevils during the first week of that deep slumber, which will never be broken, and yet which is not death. It only ceases when the intestine is empty, as is shown by autopsy. But the faint rays of life which the creature manifests do not stop there; and though sensation appears annihilated for ever, I have succeeded in reawakening some vestige of them. Having placed weevils, recently exhumed and absolutely motionless, in a bottle with sawdust moistened with benzine, I was not a little surprised to see a quarter of an hour later moving antennae and feet. For a moment I thought I could recall them to life. Vain hope! these movements, last trace of a sensitiveness about to cease, soon stopped, and could not be excited a second time. I have repeated this experiment from some hours to several days after the murder, and always with the same success; only movement is tardy in appearing in proportion as the date of the victim's death is distant. The movements are always from the forepart backward. First, the antennae move, then the front tarsi tremble and share in the oscillations; next, the second pair do the same; and finally, the third. Once movement is excited, all these members oscillate without any order until all become again motionless, as they do sooner or later. Unless death has been quite recent, movement does not go beyond the tarsi, and the legs remain motionless.

Ten days after the murder I could not obtain the least sign of irritability by the proceeding described, and I had recourse to the Voltaic battery. This is more effective, and provokes muscular contractions where the vapour of benzine fails. One or two elements of Bunsen suffice, which are armed with the rheophores of slender needles. Plunging the point of the one under the furthest ring of the abdomen, and the point of the other under the neck, you obtain each time that the current is established, not only the quivering of the tarsi, but a strong flexion of the feet, which fold themselves under the body, and relax when the current is interrupted. These movements, very energetic during the first days, gradually lose intensity, and after a certain time appear no more. On the tenth day I have still been able to obtain visible motions, but on the fifteenth the pile was unable to provoke them, notwithstanding the suppleness of the limbs and freshness of the viscera. I have submitted also to the action of the pile Coleoptera really dead, Blaps, Saperda, Lamia, asphyxiated by benzine or sulphureous gas, and two hours later it was impossible to provoke the movements obtained so easily from weevils lying already for several days in the singular state, intermediate between life and death, into which their redoubtable enemy plunges them.

All these facts contradict the supposition of an animal completely dead, and the hypothesis of a real corpse rendered incorruptible by some antiseptic liquid. One can only explain them by admitting that the animal is struck in the principle of its movements, and that sensitiveness, suddenly benumbed, dies slowly out, while the more tenacious, vegetative functions die yet more slowly and preserve the intestines during the time necessary for the larva.

The most important detail to show was how the murder is committed. Evidently, the chief part must be played by the poisoned dart of the Cerceris. But where and how does it penetrate the body of the weevil, covered with a hard cuirass, with pieces so closely joined? Even under the magnifying glass nothing told where the sting entered. Direct examination, therefore, was required to discover the murderous ways of the Cerceris--a problem before whose difficulties L?on Dufour had already recoiled, and the solution of which seemed to me for a time impossible. I tried, however, and had the satisfaction of succeeding, though not without some groping about.

When they fly from their holes to the chase, the Cerceris go here and there, sometimes on one side, sometimes on the other, and return from all directions, loaded with prey, so that they must seek it on all sides; but as they barely take ten minutes between going and returning, the space worked over could not be very great, especially considering the time necessary to discover the prey, to attack and render it an inert mass. I, therefore, set myself to examine all the adjacent ground with close attention, hoping to discover some Cerceris on the hunt. One afternoon devoted to this weary work convinced me of the uselessness of my researches, and of the little chance I had of surprising any of the few Cerceris, scattered here and there, and soon lost to view by their rapid flight; above all, in difficult ground, planted with olives, I gave up the attempt. But by carrying live weevils to the neighbourhood of the nests might I not tempt the Cerceris by a prey found without trouble, and so observe the drama? The notion seemed good, and the very next day I set out to find live Cleonus ophthalmicus. Vineyards, wheat-fields, and crops of lucerne, and heaps of stones did I visit and examine one and all, and after two days of close search I possessed--dare I own it?--three weevils! bare, dusty, maimed of antennae or tarsi, shabby old creatures which, perhaps, the Cerceris would not touch! Since the day of that fevered search, when, for a weevil's sake, I bathed myself in perspiration during my wild expedition, many a year has passed, and yet, in spite of almost daily entomological researches, I am still ignorant of the life and habits of this Cleonus, which I met here and there, straying on the edge of paths. Wonderful powers of instinct! in the same spots, and in a fraction of time, one Hymenopteron would have found hundreds of these insects which man cannot find, and found them fresh and shining, no doubt just emerged from the cocoon!

No matter; let us experiment with my wretched victim. A Cerceris has just gone into her gallery with her prey; before she comes out for a new expedition I place a weevil a few inches from her hole. The weevil moves about; when it strays too far I bring it back to its place. At last the Cerceris shows her wide face at the mouth of her hole; my heart beats fast. She walks for a few minutes near her dwelling, sees the weevil, brushes against it, turns, passes several times over its back, and flies off without even honouring my captive with a bite--my captive which cost me so much labour! I was confounded--knocked over. New attempts at other holes, new disappointments. Decidedly these dainty hunters will have none of the game which I offer them. Perhaps they find it too old, too tasteless; perhaps, in handling it, I communicated some smell to it which displeases them. Foreign contact disgusts these connoisseurs.

Should I be more fortunate if I obliged the Cerceris to defend herself? I enclosed one with a Cleonus in a bottle, irritating them by shaking it. The Hymenopteron, sensitive by nature, was more impressed than the other prisoner, with its dull, heavy organisation; she thought of escape, not attack. Their parts were exchanged; the weevil became the aggressor, sometimes seizing with the end of its trunk a foot of its mortal foe, who made no attempt at defence, so terrified was she. I could devise nothing more; my desire to be present at the d?no?ment had only added to former difficulties. Well, let us try again.

A luminous idea flashed upon me, bringing hope, so naturally did it touch the very heart of the question. Of course, it was the right thing and must succeed. My disdained game must be offered to the Cerceris in the heat of the chase--then, absorbed and preoccupied, she will not discover its imperfections. I have already said that on returning from the chase the Cerceris alights at the foot of the incline at some distance from the hole, whither she laboriously drags the prey. What I then had to do was to deprive her of her victim, drawing it away by one foot with pincers, and instantly throwing her the living weevil in exchange. This manoeuvre succeeded perfectly. As soon as the Cerceris felt the prey slip under her body and escape her, she stamped with impatience, turned round, and perceiving the weevil which had replaced hers, flung herself upon it and clasped it in order to carry it away. But she promptly perceived that this prey was alive, and then the drama began and ended with inconceivable rapidity. The Cerceris faced her victim, seized its proboscis with her powerful jaws and grasped it vigorously, and while the weevil reared itself up, pressed her forefeet hard on its back as if to force open some ventral articulation. Then the tail of the murderess slid under the Cleonus, curved and darted its poisoned lancet swiftly two or three times at the joining of the prothorax, between the first and second pair of feet. In a twinkling all was over. Without one convulsive movement, with no motion of the limbs such as accompany the death of an animal, the victim fell motionless for ever, as if annihilated. It was at once wonderful and terrible in its rapidity. Then the assassin turned the Weevil on its back, placing herself body to body with it, her legs on either side of it, and flew off. Three times I renewed the experiment with my three Weevils, and the same scene was always enacted.

Of course, each time I gave the Cerceris back her first prey and withdrew my Cleonus to examine it at greater leisure. This examination only confirmed my opinion of the terrible skill of the assassin. It is impossible to find the slightest trace of a wound, or the smallest flow of vital liquids from the point which was struck. But the most striking thing is the rapid, complete annihilation of all movement. Vainly did I seek even immediately after the murder for any trace of sensibility in the three Weevils done to death under my eyes--neither pinching nor pricking provoked it; to do so required the artificial means already mentioned. Thus these robust Cleonus, which, pierced alive with a pin and fixed by a collector on his fatal sheet of cork, would have struggled for days, weeks, nay, whole months, instantly lose all power of motion from the effect of a little prick which inoculates them with a minute drop of poison. Chemistry knows none so active in so small a dose; scarcely could prussic acid produce such an effect, if, indeed, it could do so at all. It is not then to toxology, but to physiology and anatomy that we must turn to find the cause of such instantaneous catalepsy; it is not so much the great virulence of the poison injected, as the importance of the organ injured by it which we must consider in order to explain these marvels. What, then, is found at the point where the sting penetrates?

ONE SKILFUL TO SLAY

The Hymenopteron has partly revealed her secret by showing us where the sting strikes. But does that explain the question? Not yet, by any means. Let us retrace our steps, forget for a moment what the insect has taught us, and consider the problem set before the Cerceris. The problem is this: to lay up in an underground cell a certain number of heads of game which may suffice to nourish the larva hatched from the egg laid upon the heap of provender.

At first sight this storing of food appears simple enough, but reflexion soon discovers graver difficulties. Our own game is brought down by a shot and killed with horrible wounds. The Hymenopteron has refinements unknown to us; she chooses to have her prey intact, with all its elegance of form and colour. No broken limbs, no gaping wounds, no hideous disembowelment. Her prey has all the freshness of the living insect; she does not destroy an atom of the fine-coloured powder which the mere contact of our fingers deflowers. If the insect were really dead, really a corpse, how difficult it would be for us to obtain such a result! Any one can slay an insect by stamping brutally on it, but to kill it neatly leaving no sign is no easy operation, within every one's power. How many of us would be at our wits' end if we had to kill on the spot, without crushing it, a little creature so tenacious of life that even beheaded it still goes on struggling! One must have been a practical entomologist before thinking of asphyxiation, and here, again, success would be doubtful with the primitive methods of vapour of benzine or burnt sulphur. In this deleterious atmosphere the insect struggles too long, and tarnishes its brightness. One must have recourse to more heroic methods--for instance, to the terrible exhalations of prussic acid slowly disengaging themselves from strips of paper impregnated with cyanide of potassium, or better still, as being without danger to the collector, to the thunderbolt of vapour of bisulphide of carbon. It requires a real art, an art calling to its aid the redoubtable arsenal of chemistry, to kill an insect neatly; to do that is what the elegant method of the Cerceris brings about so quickly, if we admit the stupid supposition that her prey really becomes a dead body.

A dead body! But that is by no means the diet of the larvae, little ogres greedy for fresh meat, to whom game ever so slightly tainted would inspire insurmountable disgust. They must have fresh meat with no high taste--that first sign of decay. Yet the prey cannot be laid up alive in the cell like animals destined to furnish fresh meat to the crew and passengers of a vessel. What would become of a delicate egg laid among living food? What would become of the feeble larva, a worm bruised by the slightest thing among vigorous Coleoptera moving their long spurred legs for whole weeks? It is absolutely necessary--and here we seem caught in a blind alley--to obtain deathly immobility with the freshness of life for the interior organs. Before such an alimentary problem the best instructed man of the world would stand helpless--even the practised entomologist would own himself at a loss. The larder of the Cerceris would defy their reasoning powers.

Let us then imagine an academy of entomologists and physiologists, a congress where the question should be discussed by Flourens, Majendies, Claude Bernards. To obtain at once complete immobility and long preservation of food, the first and most natural and simple idea would be that of preserved meats. One would invoke some antiseptic liquid, as the illustrious savant of the Landes did with regard to his Buprestids, and attribute such virtue to the poisonous fluid of the Cerceris, but this strange quality has yet to be proved. Gratuitous hypothesis replacing the unknown quantity of the preserving liquid may perhaps be the final verdict of the learned assembly, as it was that of the naturalist of the Landes.

Should one insist and explain that the larvae require not preserved food which could never have the properties of flesh still palpitating, but prey yet alive, so to say, in spite of complete absence of motion, the learned Congress, after ripe consideration, will fall back upon paralysis: "Yes, of course; the creature has to be paralysed without being killed." There is but one means of arriving at this result, namely, to injure, cut, and destroy the nervous system of the insect in one or more skilfully chosen points.

If the question be thus left in hands unfamiliar with the secrets of a delicate anatomy it will not have advanced far. What is the arrangement of this nervous system which must be paralysed without killing the insect? First, where is it? In the head no doubt and along the back, like the brain and spinal marrow in the superior animals. "A grave mistake!" our congress would reply; the insect is so to say an animal reversed, which walks on its back--that is, it has the spinal marrow below instead of above, all along breast and stomach; therefore on the lower surface alone can the operation to paralyse the insect be performed.

This difficulty removed, a far graver one presents itself. Armed with his scalpel, the anatomist can direct its point where he will in spite of obstacles which he may have to set aside. The Hymenopteron has no choice. Its victim is a solidly cuirassed beetle, its lancet a dart, extremely delicate, which the horny mail would certainly turn aside. Only certain points are vulnerable to the frail tool, namely, the joints, protected simply by a membrane with no power of resistance. But the joints of the limbs, although vulnerable, do not in the least fulfil the necessary conditions, for through these the utmost that could be obtained is local paralysis, not one affecting the whole organism of motion. Without any prolonged struggle, without repeated operations, which, if too numerous, might endanger the victim's life, the Hymenopteron has, if possible, to abolish all motive power at one blow. Therefore she must direct her dart at the nervous centres, the source of the power of motion whence radiate the nerves running up to the various organs of movement. Now these sources of locomotion, these nervous centres, consist of a certain number of ganglia, more numerous in the larva, less so in the perfect insect, and arranged on the median line of the under surface in a string of beads more or less distant and connected by a double ribbon of nervous tissue. In all insects which have reached the perfect state the ganglia called thoracic, i.e. those furnishing nerves to wings and feet and governing their movements, are three in number. Here are the points to be struck: if their action can be in any way destroyed, the possibility of movement is destroyed also.

To choose as the spot in which to plant her sting the one vulnerable point, the point which only a physiologist versed in the anatomy of insects could determine beforehand is by no means enough; the Hymenopteron has a far greater difficulty to overcome, and she overcomes it with a mastery which fills one with amazement. We said that the nervous centres controlling the organs of motion in an insect are three. These are more or less distant from each other, but sometimes, though rarely, near together. They possess a certain independence of action, so that an injury to one does not cause, at all events immediately, more than paralysis of members connected with it, while the other ganglia and their corresponding members are not affected by it. To reach these three sources of motion one after the other, the second farther off than the first, and the last farther still, and by a single way, between the first and second pairs of feet, seems impossible for the sting, which is too short, and besides, so difficult to aim well in such conditions. True, certain Coleoptera have the three ganglia of the thorax almost touching, and others have the two last completely united, soldered, smelted together. It is also recognised that in proportion as the different nervous centres combine and centralise, the characteristic functions of animality become more perfect, and also, alas, more vulnerable. Those Coleoptera with centres of motion so near that they touch or even gather into one mass, and so are made part of each other, would be instantly paralysed by one sting; or if several were needed, at all events the ganglia to be paralysed are all collected under the point of the dart.

Now which are the Coleoptera so specially easy to paralyse? That is the question. The lofty science of a Claude Bernard, floating in the fundamental generalities of organisation and life, is no longer enough for us; it is unable to inform and guide us in this entomological selection. I appeal to every physiologist under whose eye these lines may fall. Without having recourse to his book-shelves, could he name the Coleoptera where such a nervous centralisation is found, and even with the help of his library, could he instantly lay his hand on the information wanted? The truth is, we are entering on the minute details of the specialist; the highway is quitted for a path known to few.

I find the necessary documents in the fine work of M. E. Blanchard on the nervous system of Coleoptera. There I find that this centralisation of nerve power belongs especially to the Scarabaeus, but most of these are too large; the Cerceris could neither attack nor carry them away; besides, many live in filth, where the cleanly Hymenopteron could not go to seek them. Motive centres very close together are also found among the Histers, which live on impurity, amid the smell of decay, and again that will not do; also in the Scolytus, which is too small, and finally in Buprestids and Weevils.

What unexpected light amid the pristine obscurities of the problem! Amid the immense number of the Coleoptera which the Cerceris seem able to prey upon, two groups alone, Weevils and Buprestids, fulfil the indispensable conditions. They live far from decay and dung, which perhaps cause invincible repugnance in this dainty Cerceris; they are of most varied size, proportioned to that of their different captors, which may thus choose according to their convenience. They are far more vulnerable than all the others at the one point where the sting of the Hymenopteron can penetrate successfully, for at that point, all easily accessible to the dart, crowd the motor centres of feet and wings. At this point the three thoracic ganglia of Weevils lie very close, the hind two are contiguous. At that same spot in the Buprestids the second and third are welded in one large mass a little distance from the first. And as it is precisely Buprestids and Weevils which are hunted, to the absolute exclusion of all other game, by the eight species of Cerceris, whose food stores of Coleoptera have been ascertained, a certain internal likeness, namely, in centralisation of the nervous system must be the explanation why there are heaped in the dens of various Cerceris victims, outwardly so unlike.

In this choice, upon which even transcendent knowledge could not improve, such an assembly of difficulties is splendidly resolved, that one asks if one be not the dupe of some involuntary illusion, and if preconceived theories have not obscured the reality of facts, in short, whether the pen has not described imaginary marvels. A scientific result is only solidly established when confirmed by experiments repeated in every possible way. Now let us submit to experimental proof the physiological operation taught us by Cerceris tuberculata. If it be possible to obtain artificially what the Hymenopteron obtained by her sting, i.e. abolition of movement, and long preservation of the victim in a state of perfect freshness; if it be possible to bring about this wonder with the Coleoptera hunted by the Cerceris, or with those possessing a like nervous centralisation, while one fails with those whose ganglia are far apart, one must admit, however exacting one may be in the matter of proof, that the Hymenopteron possesses in the unconscious inspirations of instinct the resources of sublime science. Let us see then what experiment shows. The manner of operation is very simple. With a needle, or, better still, with the point of a fine steel pen, we must introduce a tiny drop of some corrosive liquid into the thoracic motive centres, pricking the insect slightly at the jointing of the prothorax behind the first pair of feet. The liquid which I use is ammonia, but it is evident that any other liquid whose action is equally strong would produce the same results. The metal pen being charged with ammonia as it might be with a droplet of ink, I give the prick. The effects thus obtained differ enormously, according to whether the experiment be made upon species with thoracic ganglia near together or upon those where these same ganglia are far apart. With regard to the first category, my experiments were made on Scarabaeus, S. sacer and S. longicollis; on a bronze Buprestis; and on weevils, especially that Cleonus hunted by the heroine of these observations. In the second category I have experimented on Caraboidea, Carabus, Procrustes, Chloenius, Sphodrus, Nebria; Longicornia, Saperda, and Lamia; on Melasomes; Blaps, Scaurus, and Asida.

Among the Scarabaeus class, the Buprestids, and the Weevils, the effect is instantaneous. Every movement stops suddenly, without any convulsion, as soon as the fatal drop has touched the nerve centres. The sting of the Cerceris does not produce prompter extinction. Nothing can be more striking than this sudden immobility in a vigorous Scarabaeus sacer, but the likeness between the effects produced by the dart of the Cerceris and the steel pen charged with ammonia does not stop here. Scarabaeids, Buprestids, and Weevils artificially stung, in spite of their complete immobility, preserve for three weeks, one month, or even two, the perfect flexibility of every joint and the normal freshness of the interior organs. With them defecation takes place on the first days as in the normal condition, and movement can be excited by the Voltaic current. In a word, they behave exactly as do Coleoptera sacrificed by the Cerceris. There is complete identity between the state into which she plunges her victims and that produced at will by injecting ammonia into the nerve centres of the thorax. Now, as it is impossible to attribute the perfect preservation of the insect during so long a time to the drop injected, one must altogether reject the notion of an antiseptic fluid, and grant that in spite of utter immobility the creature is not really dead. A spark of life exists, keeping the organs for some time in normal freshness, but dying out by degrees and leaving them at last subject to corruption. Moreover, the ammonia in some cases produces extinction of movement in the feet only, and then the deleterious action of the fluid having doubtless not extended far enough, the antennae preserve some mobility, and one sees that the creature, even a month after inoculation, draws them back quickly at the least touch--an evident proof that life has not completely abandoned the inert body. This movement is not rare with Weevils wounded by the Cerceris.

Injection of ammonia always stops motion at once in Buprestids, Weevils, and Scarabaeus, but it is not always possible to put the creature into the state just described. If the wound be too deep, or the little drop instilled be too strong, at the end of two or three days the victim really dies, and after two or three days there is but a decaying body. If, on the contrary, the prick be too slight, it recovers the power of motion, at least partially, after being inanimate for more or less time. The Cerceris herself may operate clumsily, just like man, for I have seen this kind of resurrection in a victim struck by the dart of a Hymenopteron. Sphex flavipennis, whose history will presently occupy us, heaps in her dens young crickets struck by her venomed lancet. From one of her holes I have taken three poor crickets whose extreme flabbiness would, in any other circumstances, have denoted death. But here, again, death was only apparent. Placed in a bottle, these crickets kept quite fresh but motionless for nearly three weeks, after which two grew mouldy, while the third came partly to life--that is to say, it regained motion of the antennae, mouth-parts, and, which is more remarkable, of the first two pairs of feet. If even the skill of the Hymenopteron sometimes fails to benumb a victim for good and all, can one expect constant success with the rough experiments of man?

The Melasomes and the Longicorns are more sensitive to the action of ammonia. The injection of a small corrosive drop quickly renders them motionless, and after some twitching they seem dead. But the paralysis which would have persisted in Weevils, Scarabids, and Buprestids is but momentary. Before long motion reappears as energetic as before. It is only when the dose of ammonia is of a certain strength that movement does not reappear. But then the creature is really dead, and putrefaction rapidly comes on. It is then impossible to cause complete and persistent paralysis in Coleoptera with ganglia far apart by the means so efficacious in those with ganglia near together. At the utmost one can only obtain momentary paralysis, which passes quickly away. The demonstration is decisive. Cerceris which prey on Coleoptera conform in their choice to what the most learned physiology and finest anatomy alone can teach. It would be vain to endeavour to see nothing here but chance agreement; it is not chance which explains such harmony.

THE YELLOW-WINGED SPHEX

In their impenetrable coat of mail the Coleoptera offer but one vulnerable point to their dart-bearing foe. This defect in the cuirass is known to the assassin, and the poisoned sting is there inserted, striking at one blow the three centres of motion, the Weevil and Buprestid, which alone have a nervous organisation sufficiently centralised, being selected. But what happens when the insect wears no armour and is soft-skinned, so that the Hymenopteron can pierce it anywhere that the chances of the struggle may direct? Is there then a choice as to where the blow is given? Like the assassin who strikes at the heart to shorten the dangerous struggles of his victim, does the Sphex follow the tactics of the Cerceris, and strike by preference at the motor ganglia? If so, what happens when these are distant from one another, acting so independently that paralysis of one does not affect the others? These questions will be answered by the history of an insect which hunts field crickets, Sphex flavipennis.

It is towards the end of July that this Sphex tears open the cocoon which until then has protected it, and flies away from its subterranean cradle. During the whole of August one constantly sees it seeking drops of honey on the spiny heads of Eryngium campestre, the commonest of such robust plants as brave the dog days. But this careless life is brief, for in the earliest days of September the Sphex has begun the hard existence of miner and hunter. It is usually on some small flat spot on banks along a road that the dwelling is established, only there must be two indispensable conditions--a sandy soil easy to work, and sun. Beyond this no precaution is taken to shelter the domicile against autumn rain and winter frost. A horizontal position, unsheltered, beaten by rain and wind, suit the Sphex perfectly, so long as it is exposed to the sun. But when the work is half-way through, if heavy rain should come, it is sad to see next day galleries in course of construction choked with sand and finally abandoned.

Rarely does the Sphex work in solitude; it is in small bands of ten, twenty, or more excavators that the claim selected is worked. One must have spent some days watching one of these colonies in order to form any idea of the restless activity, the feverish haste, the abrupt movements, of these hard-working miners. They rapidly attack the ground with the rakes of their forefeet, canis instar, as Linnaeus says. A puppy does not show more energy in scratching up the ground in play. At the same time each labourer hums a joyous song--shrill, high-pitched, interrupted at short intervals, and modulated by vibrations of wings and thorax. One would think they were a troop of merry comrades, stimulating one another to work by a cadenced rhythm. Meanwhile, the sand flies, falling in fine dust on their quivering wings, and the heavier gravel, pulled out bit by bit, rolls far away. If a bit resist too much, the insect goes at it with a high note, reminding one of the cry with which a woodcutter accompanies the stroke of his axe. Under the redoubled efforts of tarsi and mandibles the cavity is already sketched out, and the Sphex can already dart into it. Then comes a lively interchange of forward movements to detach material, and of backward to brush out fragments. In this hurried coming and going the Sphex does not so much walk as dart forward, as though impelled by a spring. With panting abdomen, antennae vibrating, the whole body moved by a strong thrill, she springs forward and is out of sight. You still hear the unwearied hum underground, and one sees from time to time hind legs pushing backward a wave of sand to the mouth of the burrow. From time to time labour underground is interrupted either that the Sphex may dust herself in the sunlight, and get rid of grains of dust which insinuate themselves into delicate joints and hamper the liberty of her movements, or that she make a reconnaissance in the neighbourhood. Notwithstanding these short interruptions, in a few hours the gallery is hollowed out and the Sphex appears on her threshold, to voice her triumph, and give the last touch to her labours by effacing some inequality, or carrying away some particles of earth, the objection to which only the eye of a Sphex could perceive.

Of the many tribes of Sphegidae visited by me, there is one of which I retain a specially lively recollection, on account of its singular installation upon the edge of a high road, where were little heaps of mud thrown up from side ditches by the cantonnier's shovel. One, well sun-dried, had a conical shape like a sugar-loaf over fifteen inches high. The situation pleased the Sphegidae, who had established a more populous community than I have ever again met with. From base to summit the cone of dried mud was pierced with burrows, giving it the appearance of a huge sponge. In every story was feverish animation, and a busy coming and going which brought to mind the scene in some great workshop when orders are pressing. Crickets were being dragged by the antennae up the slopes of the conical city; there was storing of provisions in the larders of the cells; dust was pouring from galleries in process of construction; at intervals the grimy faces of the miners appeared at mouths of passages--there was a constant going and coming. Now and then, in a short interval of leisure, a Sphex ascended the top of the cone, perhaps to take a general and well-satisfied view from this belvedere. What a tempting sight!--one to make me long to carry away the entire city with its inhabitants. It was useless to try; the mass was too heavy. One cannot take up a village by the roots to plant it elsewhere.

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