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Both larvae practise a special art of eating, which is determined by the nature of the game. The Sphex, when sitting down to an Ephippiger, the food that has fallen to its lot, knows thoroughly how to consume it and how to preserve, to the very end, the glimmer of life which keeps it fresh; but, if it has to browse upon a Cetonia-grub, whose different structure would confuse its talents as a dissector, it would soon have nothing before it but a heap of putrescence. The Scolia, in its turn, is familiar with the method of eating the Cetonia-grub, its invariable portion; but it does not understand the art of eating the Ephippiger, though the dish is to its taste. Unable to dissect this unknown species of game, its mandibles slash away at random, killing the creature outright as soon as they take their first bites of the deeper tissues of the victim. That is the whole secret.
One more word, on which I shall enlarge in another chapter. I observe that the Scoliae to which I give Ephippigers paralysed by the Sphex keep in excellent condition, despite the change of diet, so long as the provisions retain their freshness. They languish when the game goes high; and they die when putridity supervenes. Their death, therefore, is due not to an unaccustomed diet, but to poisoning by one or other of those terrible toxins which are engendered by animal corruption and which chemistry calls by the name of ptomaines. Therefore, notwithstanding the fatal outcome of my three attempts, I remain persuaded that the unfamiliar method of rearing would have been perfectly successful had the Ephippigers not gone bad, that is, if the Scoliae had known how to eat them according to the rules.
What a delicate and dangerous thing is the art of eating in these carnivorous larvae supplied with a single victim, which they have to spend a fortnight in consuming, on the express condition of not killing it until the very end! Could our physiological science, of which, with good reason, we are so proud, describe, without blundering, the method to be followed in the successive mouthfuls? How has a miserable grub learnt what our knowledge cannot tell us? By habit, the Darwinians will reply, who see in instinct an acquired habit.
Before deciding this serious matter, I will ask you to reflect that the first Wasp, of whatever kind, that thought of feeding her progeny on a Cetonia-grub or on any other large piece of game demanding long preservation could necessarily have left no descendants unless the art of consuming food without causing putrescence had been practised, with all its scrupulous caution, from the first generation onwards. Having as yet learnt nothing by habit or by atavistic transmission, since it was making a first beginning, the nurseling would bite into its provender at random. It would be starving, it would have no respect for its prey. It would carve its joint at random; and we have just seen the fatal consequence of an ill-directed bite. It would perish—I have just proved this in the most positive manner—it would perish, poisoned by its victim, already dead and putrid.
To prosper, it would have, although a novice, to know what was permitted and what forbidden in ransacking the creature's entrails; nor would it be enough for the larva to be approximately in possession of this difficult secret: it would be indispensable that it should possess the secret completely, for a single bite, if delivered before the right moment, would inevitably involve its own demise. The Scoliae of my experiments are not novices, far from it: they are the descendants of carvers that have practised their art since Scoliae first came into the world; nevertheless they all perish from the decomposition of the rations supplied, when I try to feed them on Ephippigers paralysed by the Sphex. Very expert in the method of attacking the Cetonia, they do not know how to set about the business of discreetly consuming a species of game new to them. All that escapes them is a few details, for the trade of an ogre fed on live flesh is familiar to them in its general features; and these unheeded details are enough to turn their food into poison. What, then, happened in the beginning, when the larva bit for the first time into a luscious victim? The inexperienced creature perished; of that there is not a shadow of doubt, unless we admit an absurdity and imagine the larva of antiquity feeding upon those terrible ptomaines which so swiftly kill its descendants to-day.
Nothing will ever make me admit and no unprejudiced mind can admit that what was once food has become a horrible poison. What the larva of antiquity ate was live flesh and not putrescence. Nor can it be admitted that the chances of fortune can have led at the first trial to success in a system of nourishment so full of pit-falls: fortuitous results are preposterous amid so many complications. Either the feeding is strictly methodical at the beginning, in conformity with the organic exigencies of the prey devoured, and the Wasp established her race; or else it was hesitating, without determined rules, and the Wasp left no successor. In the first case we behold innate instinct; in the second acquired habit.
A strange acquisition, truly! An acquisition presumed to be made by an impossible creature; an acquisition supposed to develop in no less impossible successors! Though the snow-ball, slowly rolling, at last becomes an enormous sphere, it is still necessary that the starting-point shall not have been NIL. The big ball implies the little ball, as small as you please. Now, in harking back to the origin of these acquired habits, if I interrogate the possibilities I obtain zero as the only answer. If the animal does not know its trade thoroughly, if it has to acquire something, all the more if it has to acquire everything, it perishes: that is inevitable; without the little snow-ball the big snow-ball cannot be rolled. If it has nothing to acquire, if it knows all that it needs to know, it flourishes and leaves descendants behind it. But then it possesses innate instinct, the instinct which learns nothing and forgets nothing, the instinct which is steadfast throughout time.
The building up of theories has never appealed to me: I suspect them one and all. To argue nebulously upon dubious premises likes me no better. I observe, I experiment and I let the facts speak for themselves. We have just heard these facts. Let each now decide for himself whether instinct is an innate faculty or an acquired habit.
CHAPTER 4. THE CETONIA-LARVA.
The Scolia's feeding-period lasts, on the average, for a dozen days or so. By then the victuals are no more than a crumpled bag, a skin emptied of the last scrap of nutriment. A little earlier, the russet-yellow tint announces the extinction of the last spark of life in the creature that is being devoured. The empty skin is pushed back to make space; the dining-room, a shapeless cavity with crumbling walls, is tidied up a little; and the Scolia-grub sets to work on its cocoon without further delay.
The first courses form a general scaffolding, which finds a support here and there on the earthen walls, and consist of a rough, blood-red fabric. When the larva is merely laid, as required by my investigations, in a hollow made with the finger-tip in the bed of mould, it is not able to spin its cocoon, for want of a ceiling to which to fasten the upper threads of its network. To weave its cocoon, every spinning larva is compelled to isolate itself in a hammock slung in an open-work enclosure, which enables it to distribute its thread uniformly in all directions. If there be no ceiling, the upper part of the cocoon cannot be fashioned, because the worker lacks the necessary points of support. Under these conditions my Scolia-grubs contrive at most to upholster their little pit with a thick down of reddish silk. Discouraged by futile endeavours, some of them die. It is as if they had been killed by the silk which they omit to disgorge because they are unable to make the right use of it. This, if we were not watchful, would be a very frequent cause of failure in our attempts at artificial rearing. But, once the danger has been perceived, the remedy is simple. I make a ceiling over the cavity by laying a short strip of paper above it. If I want to see how matters are progressing, I bend the strip into a semicircle, into a half-cylinder with open ends. Those who wish to play the breeder for themselves will be able to profit by these little practical details.
In twenty-four hours the cocoon is finished; at least, it no longer allows us to see the grub, which is doubtless making the walls of its dwelling still thicker. At first the cocoon is a vivid red; later it changes to a light chestnut-brown. Its form is that of an ellipsoid, with a major axis 26 millimetres in length, while the minor axis measures 11 millimetres. (1.014 x.429 inch.—Translator's Note.) These dimensions, which incidentally are inclined to vary slightly, are those of the female cocoons. In the other sex they are smaller and may measure as little as 17 millimetres in length by 7 millimetres in width. (.663 x.273 inch.—Translator's Note.)
The two ends of the ellipsoid have the same form, so much so that it is only thanks to an individual peculiarity, independent of the shape, that we can tell the cephalic from the anal extremity. The cephalic pole is flexible and yields to the pressure of my tweezers; the anal pole is hard and unyielding. The wrapper is double, as in the cocoons of the Sphex. (Cf. "The Hunting Wasps": chapters 4 to 10 et passim.—Translator's Note.) The outer envelope, consisting of pure silk, is thin, flexible and offers little resistance. It is closely superimposed upon the inner envelope and is easily separated from it everywhere, except at the anal end, where it adheres to the second envelope. The adhesion of the two wrappers at one end and the non-adhesion at the other are the cause of the differences which the tweezers reveal when pinching the two ends of the cocoon.
The inner envelope is firm, elastic, rigid and, to a certain point, brittle. I do not hesitate to look upon it as consisting of a silken tissue which the larva, towards the end of its task, has steeped thoroughly in a sort of varnish prepared not by the silk-glands but by the stomach. The cocoons of the Sphex have already shown us a similar varnish. This product of the chylific ventricle is chestnut-brown. It is this which, saturating the thickness of the tissue, effaces the bright red of the beginning and replaces it by a brown tint. It is this again which, disgorged more profusely at the lower end of the cocoon, glues the two wrappers together at that point.
The perfect insect is hatched at the beginning of July. The emergence takes place without any violent effraction, without any ragged rents. A clean, circular fissure appears at some distance from the top; and the cephalic end is detached all of a piece, as a loose lid might be. It is as though the recluse had only to raise a cover by butting it with her head, so exact is the line of division, at least as regards the inner envelope, the stronger and more important of the two. As for the outer wrapper, its lack of resistance enables it to yield without difficulty when the other gives way.
I cannot quite make out by what knack the Wasp contrives to detach the cap of the inner shell with such accuracy. Is it the art practised by the tailor when cutting his stuff, with mandibles taking the place of scissors? I hardly venture to admit as much: the tissue is so tough and the circle of division so precise. The mandibles are not sharp enough to cut without leaving a ragged edge; and then what geometrical certainty they would need for an operation so perfect that it might well have been performed with the compasses!
I suspect therefore that the Scolia first fashions the outer sac in accordance with the usual method, that is, by distributing the silk uniformly, without any special preparation of one part of the wall more than of another, and that it afterwards changes its method of weaving in order to attend to the main work, the inner shell. In this it apparently imitates the Bembex (Cf. "The Hunting Wasps": chapters 14 to 16.—Translator's Note.), which weaves a sort of eel-trap, whose ample mesh allows it to gather grains of sand outside and encrust them one by one in the silky network, and completes the performance with a cap fitting the entrance to the trap. This provides a circular line of least resistance, along which the casket breaks open afterwards. If the Scolia really works in the same manner, everything is explained: the eel-trap, while still open, enables it to soak with varnish both the inside and the outside of the inner shell, which has to acquire the consistency of parchment; lastly, the cap which completes and closes the structure leaves for the future a circular line capable of splitting easily and neatly.
This is enough on the subject of the Scolia-grub. Let us go back to its provender, of whose remarkable structure we as yet know nothing. In order that it may be consumed with the delicate anatomical discretion imposed by the necessity of having fresh food to the last, the Cetonia-grub must be plunged into a state of absolute immobility: any twitchings on its part—as the experiments which I have undertaken go to prove—would discourage our nibbling larva and impede the work of carving, which has to be effected with so much circumspection. It is not enough for the victim to be unable to move from place to place beneath the soil: in addition to this, the contractible power in its sturdy muscular organism must be suppressed.
In its normal state, this larva, at the very least disturbance, curls itself up, almost as the Hedgehog does; and the two halves of the ventral surface are laid one against the other. You are quite surprised at the strength which the creature displays in keeping itself thus contracted. If you try to unroll it, your fingers encounter a resistance far greater than the size of the animal would have caused you to suspect. To overcome the resistance of this sort of spring coiled upon itself, you have to force it, so much so that you are afraid, if you persist, of seeing the indomitable spiral suddenly burst and shoot forth its entrails.
A similar muscular energy is found in the larvae of the Oryctes (Also known as the Rhinoceros Beetle.—Translator's Note.), the Anoxia (A Beetle akin to the Cockchafer.—Translator's Note.), the Cockchafer. Weighed down by a heavy belly and living underground, where they feed either on leaf-mould or on roots, these larvae all possess the vigorous constitution needed to drag their corpulence through a resisting medium. All of them also roll themselves into a hook which is not straightened without an effort.
Now what would become of the egg and the new-born grub of the Scoliae, fixed under the belly, at the centre of the Cetonia's spiral, or inside the hook of the Oryctes or the Anoxia? They would be crushed between the jaws of the living vice. It is essential that the arc should slacken and the hook unbend, without the least possibility of their returning to a state of tension. Indeed, the well-being of the Scoliae demands something more: those powerful bodies must not retain even the power to quiver, lest they derange a method of feeding which has to be conducted with the greatest caution.
The Cetonia-grub to which the Two-banded Scolia's egg is fastened fulfils the required conditions admirably. It is lying on its back, in the midst of the mould, with its belly fully extended. Long accustomed though I be to this spectacle of victims paralysed by the sting of the Hunting Wasp, I cannot suppress my astonishment at the profound immobility of the prey before my eyes. In the other victims with flexible skins, Caterpillars, Crickets, Mantes, Ephippigers, I perceived at least some pulsations of the abdomen, a few feeble contortions under the stimulus of a needle. There is nothing of the sort here, nothing but absolute inertia, except in the head, where I see, from time to time, the mouth-parts open and close, the palpi give a tremor, the short antennae sway to and fro. A prick with the point of a needle causes no contraction, no matter what the spot pricked. Though I stab it through and through, the creature does not stir, be it ever so little. A corpse is not more inert. Never, since my remotest investigations, have I witnessed so profound a paralysis. I have seen many wonders due to the surgical talent of the Wasp; but to-day's marvel surpasses them all.
I am doubly surprised when I consider the unfavourable conditions under which the Scolia operates. The other paralysers work in the open air, in the full light of day. There is nothing to hinder them. They enjoy full liberty of action in seizing the prey, holding it in position and sacrificing it; they are able to see the victim and to parry its means of defence, to avoid its spears, its pincers. The spot or spots to be attained are within their reach; they drive the dagger in without let or hindrance.
What difficulties, on the other hand, await the Scolia! She hunts underground, in the blackest darkness. Her movements are laboured and uncertain, owing to the mould, which is continually giving way all round her; she cannot keep her eyes on the terrible mandibles, which are capable of cutting her body in two with a single bite. Moreover, the Cetonia-grub, perceiving that the enemy is approaching, assumes its defensive posture, rolls itself up and makes a shield for its only vulnerable part, the ventral surface, with its convex back. No, it cannot be an easy operation to subdue the powerful larva in its underground retreat and to stab with the precision which immediate paralysis requires.
We wish that we might witness the struggle between the two adversaries and see at first hand what happens, but we cannot hope to succeed. It all takes place in the mysterious darkness of the soil; in broad daylight, the attack would not be delivered, for the victim must remain where it is and then and there receive the egg, which is unable to thrive and develop except under the warm cover of vegetable mould. If direct observation is impracticable, we can at least foresee the main outlines of the drama by allowing ourselves to be guided by the warlike manoeuvres of other burrowers.
I picture things thus: digging and rummaging through the heap of mould, guided perhaps by that singular sensibility of the antennae which enables the Hairy Ammophila to discover the Grey Worm (The caterpillar of the Turnip Moth. Cf. "The Hunting Wasps": chapters 18 to 20.—Translator's Note.) underground, the Scolia ends by finding a Cetonia-larva, a good plump one, in the pink of condition, having reached its full growth, just what the grub which is to feed on it requires. Forthwith, the assaulted victim, contracting desperately, rolls itself into a ball. The other seizes it by the skin of the neck. To unroll it is impossible to the insect, for I myself have some trouble in doing so. One single point is accessible to the sting: the under part of the head, or rather of the first segments, which are placed outside the coil, so that the grub's hard cranium makes a rampart for the hinder extremity, which is less well defended. Here the Wasp's sting enters and here only can it enter, within a narrowly circumscribed area. One stab only of the lancet is given at this point, one only because there is no room for more; and this is enough: the larva is absolutely paralysed.
The nervous functions are abolished instantly; the muscular contractions cease; and the animal uncoils like a broken spring. Henceforth motionless, it lies on its back, its ventral surface fully exposed from end to end. On the median line of this surface, towards the rear, near the brown patch due to the alimentary broth contained in the intestine, the Scolia lays her egg and without more ado, leaves everything lying on the actual spot where the murder was committed, in order to go in search of another victim.
This is how the deed must be done: the results prove it emphatically. But then the Cetonia-grub must possess a very exceptional structure in its nervous organization. The larva's violent contraction leaves but a single point of attack open to the sting, the under part of the neck, which is doubtless uncovered when the victim tries to defend itself with its mandibles; and yet a stab in this one point produces the most thorough paralysis that I have ever seen. It is the general rule that larvae possess a centre of innervation for each segment. This is so in particular with the Grey Worm, the sacrificial victim of the Hairy Ammophila. The Wasp is acquainted with this anatomical secret: she stabs the caterpillar again and again, from end to end, segment by segment, ganglion by ganglion. With such an organization the Cetonia-grub, unconquerably coiled upon itself would defy the paralyser's surgical skill.
If the first ganglion were wounded, the others would remain uninjured; and the powerful body, actuated by these last, would lose none of its powers of contraction. Woe then to the egg, to the young grub held fast in its embrace! And how insurmountable would be the difficulties if the Scolia, working in the profound darkness amid the crumbling soil and confronted by a terrible pair of mandibles, had to stab each segment in turn with her sting, with the certainty of method displayed by the Ammophila! The delicate operation is possible in the open air, where nothing stands in the way, in broad daylight, where the sight guides the scalpel, and with a patient which can always be released if it becomes dangerous. But in the dark, underground, amidst the ruins of a ceiling which crumbles in consequence of the conflict and at close quarters with an opponent greatly her superior in strength, how is the Scolia to guide her sting with the accuracy that is essential if the stabs are to be repeated?
So profound a paralysis; the difficulty of vivisection underground; the desperate coiling of the victim: all these things tell me that the Cetonia-grub, as regards its nervous system, must possess a structure peculiar to itself. The whole of the ganglia must be concentrated in a limited area in the first segments, almost under the neck. I see this as clearly as though it had been revealed to me by a post-mortem dissection.
Never was anatomical forecast more fully confirmed by direct examination. After forty-eight hours in benzine, which dissolves the fat and renders the nervous system more plainly visible, the Cetonia-grub is subjected to dissection. Those of my readers who are familiar with these investigations will understand my delight. What a clever school is the Scolia's! It is just as I thought! Admirable! The thoracic and abdominal ganglia are gathered into a single nervous mass, situated within the quadrilateral bounded by the four hinder legs, which legs are very near the head. It is a tiny, dull-white cylinder, about three millimetres long by half a millimetre wide. (.117 x.019 inch.—Translator's Note.) This is the organ which the Scolia's sting must attack in order to secure the paralysis of the whole body, excepting the head, which is provided with special ganglia. From it run numbers of filaments which actuate the feet and the powerful muscular layer which is the creature's essential motor organ. When examined merely through the pocket-lens, this cylinder appears to be slightly furrowed transversely, a proof of its complex structure. Under the microscope, it is seen to be formed by the close juxtaposition, the welding, end to end, of the ganglia, which can be distinguished one from the other by a slight intermediate groove. The bulkiest are the first, the fourth and the tenth, or last; these are all very nearly of equal size. The rest are barely half or even a third as large as those mentioned.
The Interrupted Scolia experiences the same hunting and surgical difficulties when she attacks, in the crumbling, sandy soil, the larvae of the Shaggy Anoxia or of the Morning Anoxia, according to the district; and these difficulties, if they are to be overcome, demand in the victim a concentrated nervous system, like the Cetonia's. Such is my logical conviction before making my examination; such also is the result of direct observation. When subjected to the scalpel, the larva of the Morning Anoxia shows me its centres of innervation for the thorax and the abdomen, gathered into a short cylinder, which, placed very far forward, almost immediately after the head, does not run back beyond the level of the second pair of legs. The vulnerable point is thus easily accessible to the sting, despite the creature's posture of defence, in which it contracts and coils up. In this cylinder I recognize eleven ganglia, one more than in the Cetonia. The first three, or thoracic, ganglia are plainly distinguishable from one another, although they are set very close together; the rest are all in contact. The largest are the three thoracic ganglia and the eleventh.
After ascertaining these facts, I remembered Swammerdam's investigations into the grub of the Monoceros, our Oryctes nasicornis. (Jan Swammerdam (1637-1680), the Dutch naturalist and anatomist.—Translator's Note.) I chanced to possess an abridgement of the "Biblia naturae," the masterly work of the father of insect anatomy. I consulted the venerable volume. It informed me that the learned Dutchman had been struck, long before I was, by an anatomical peculiarity similar to that which the larvae of the Cetoniae and Anoxiae had shown me in their nerve-centres. Having observed in the Silk-worm a nervous system formed of ganglia distinct one from the other, he was quite surprised to find that, in the grub of the Oryctes, the same system was concentrated into a short chain of ganglia in juxtaposition. His was the surprise of the anatomist who, studying the organ qua organ, sees for the first time an unusual conformation. Mine was of a different nature: I was amazed to see the precision with which the paralysis of the victim sacrificed by the Scolia, a paralysis so profound in spite of the difficulties of an underground operation, had guided my forecast as to structure when, anticipating the dissection, I declared in favour of an exceptional concentration of the nervous system. Physiology perceived what anatomy had not yet revealed, at all events to my eyes, for since then, on dipping into my books, I have learnt that these anatomical peculiarities, which were then so new to me, are now within the domain of current science. We know that, in the Scarabaeidae, both the larva and the perfect insect are endowed with a concentrated nervous system.
The Garden Scolia attacks Oryctes nasicornis; the Two-banded Scolia the Cetonia; the Interrupted Scolia the Anoxia. All three operate below ground, under the most unfavourable conditions; and all three have for their victim a larva of one of the Scarabaeidae, which, thanks to the exceptional arrangement of its nerve-centres, lends itself, alone of all larvae, to the Wasp's successful enterprises. In the presence of this underground game, so greatly varied in size and shape and yet so judiciously selected to facilitate paralysis, I do not hesitate to generalize and I accept, as the ration of the other Scoliae, larvae of Lamellicorns whose species will be determined by future observation. Perhaps one of them will be found to give chase to the terrible enemy of my crops, the voracious White Worm, the grub of the Cockchafer; perhaps the Hemorrhoidal Scolia, rivalling in size the Garden Scolia and like her, no doubt, requiring a copious diet, will be entered in the insects' "Who's Who" as the destroyer of the Pine-chafer, that magnificent Beetle, flecked with white upon a black or brown ground, who of an evening, during the summer solstice, browses on the foliage of the fir-trees. Though unable to speak with certainty or precision, I am inclined to look upon these devourers of Scarabaeus-grubs as valiant agricultural auxiliaries.
The Cetonia-larva has figured hitherto only in its quality of a paralysed victim. We will now consider it in its normal state. With its convex back and its almost flat ventral surface, the creature is like a semi-cylinder in shape, fuller in the hinder portion. On the back, each of the segments, except the last, or anal, segment, puckers into three thick pads, bristling with stiff, tawny hairs. The anal segment, much wider than the rest, is rounded at the end and coloured a deep brown by the contents of the intestine, which show through the translucent skin; it bristles with hairs like the other segments, but is level, without pads. On the ventral surface, the segments have no creases; and the hairs, though abundant, are rather less so than on the back. The legs, which are quite well-formed, are short and feeble in comparison with the animal's size. The head has a strong, horny cap for a cranium. The mandibles are powerful, with bevelled tips and three or four teeth on the edge of the bevel.
Its mode of locomotion marks it as an idiosyncratic, exceptional, fantastic creature, having no fellow, that I know of, in the insect world. Though endowed with legs—a trifle short, it is true, but after all as good as those of a host of other larvae—it never uses them for walking. It progresses on its back, always on its back, never otherwise. By means of wriggling movements and the purchase afforded by the dorsal bristles, it makes its way belly upwards, with its legs kicking the empty air. The spectator to whom these topsy-turvy gymnastics are a novelty thinks at first that the creature must have had a fright of some sort and that it is struggling as best it can in the face of danger. He puts it back on its belly; he lays it on its side. Nothing is of any use; it obstinately turns over and resumes its dorsal progress. That is its manner of travelling over a flat surface; it has no other.
This reversal of the usual mode of walking is so peculiar to the Cetonia-larva that it is enough in itself to reveal the grub's identity to the least expert eyes. Dig into the vegetable mould formed by the decayed wood in the hollow trunks of old willow-trees, search at the foot of rotten stumps or in heaps of compost; and, if you come upon a plumpish grub moving along on its back, there is no room for doubt: your discovery is a Cetonia-larva.
This topsy-turvy progress is fairly swift and is not less in speed to that of an equally fat grub travelling on its legs. It would even be greater on a polished surface, where walking on foot is hampered by incessant slips, whereas the numerous hairs of the dorsal pads find the necessary support by multiplying the points of contact. On polished wood, on a sheet of paper and even on a strip of glass, I see my grubs moving from point to point with the same ease as on a surface of garden mould. In the space of one minute, on the wood of my table, they cover a distance of eight inches. The pace is no swifter on a horizontal bed of sifted mould. A strip of glass reduces the distance covered by one half. The slippery surface only half paralyses this strange method of locomotion.
We will now place side by side with the Cetonia-grub the larva of the Morning Anoxia, the prey of the Interrupted Scolia. It is very like the larva of the Common Cockchafer. It is a fat, pot-bellied grub, with a thick, red cap on its head and armed with strong, black mandibles, which are powerful implements for digging and cutting through roots. The legs are sturdy and end in a hooked nail. The creature has a long, heavy, brown paunch. When placed on the table, it lies on its side; it struggles without being able to advance or even to remain on its belly or back. In its usual posture it is curled up into a narrow hook. I have never seen it straighten itself completely; the bulky abdomen prevents it. When placed on a surface of moist sand, the ventripotent creature is no better able to shift its position: curved into a fish-hook, it lies on its side.
To dig into the earth and bury itself, it uses the fore-edge of its head, a sort of weeding-hoe with the two mandibles for points. The legs take part in this work, but far less effectually. In this way it contrives to dig itself a shallow pit. Then, bracing itself against the wall of the pit, with the aid of wriggling movements which are favoured by the short, stiff hairs bristling all over its body, the grub changes its position and plunges into the sand, but still with difficulty.
Apart from a few details, which are of no importance here, we may repeat this sketch of the Anoxia-grub and we shall have, if the size be at least quadrupled, a picture of the larva of Oryctes nasicornis, the monstrous prey of the Garden Scolia. Its general appearance is the same: there is the same exaggeration of the belly; the same hook-like curve; the same incapacity for standing on its legs. And as much may be said of the larva of Scarabaeus pentodon, a fellow-boarder of the Oryctes and the Cetonia.
CHAPTER 5. THE PROBLEM OF THE SCOLIAE.
Now that all the facts have been set forth, it is time to collate them. We already know that the Beetle-hunters, the Cerceres (Cf. "The Hunting Wasps": chapters 1 to 3.—Translator's Note.), prey exclusively on the Weevils and the Buprestes, that is, on the families whose nervous system presents a degree of concentration which may be compared with that of the Scolia's victims. Those predatory insects, working in the open air, are exempt from the difficulties which their emulators, working underground, have to overcome. Their movements are free and are directed by the sense of sight; but their surgery is confronted in another respect with a most arduous problem.
The victim, a Beetle, is covered at all points with a suit of armour which the sting is unable to penetrate. The joints alone will allow the poisoned lancet to pass. Those of the legs do not in any way comply with the conditions imposed: the result of stinging them would be merely a partial disorder which far from subduing the insect, would render it more dangerous by irritating it yet further. A sting in the joint of the neck is not admissible: it would injure the cervical ganglia and lead to death, followed by putrefaction. There remains only the joint between the corselet and the abdomen.
The sting, in entering here, has to abolish all movement with a single stab, for any movement would imperil the rearing of the larva. The success of the paralysis, therefore, demands that the motor ganglia, at least the three thoracic ganglia, shall be packed in close contact opposite this point. This determines the selection of Weevils and Buprestes, both of which are so strongly armoured.
But where the prey has only a soft skin, incapable of stopping the sting, the concentrated nervous system is no longer necessary, for the operator, versed in the anatomical secrets of her victim, knows to perfection where the centres of innervation lie; and she wounds them one after another, if need be from the first to the last. Thus do the Ammophilae go to work when dealing with their caterpillars and the Sphex-wasps when dealing with their Locusts, Ephippigers and Crickets.
With the Scoliae we come once again to a soft prey, with a skin penetrable by the sting no matter where it be attacked. Will the tactics of the caterpillar-hunters, who stab and stab again, be repeated here? No, for the difficulty of movement under ground prohibits so complicated an operation. Only the tactics of the paralysers of armour-clad insects are practicable now, for, since there is but one thrust of the dagger, the feat of surgery is reduced to its simplest terms, a necessary consequence of the difficulties of an underground operation. The Scoliae, then, whose destiny it is to hunt and paralyse under the soil the victuals for their family, require a prey made highly vulnerable by the close assemblage of the nerve-centres, as are the Weevils and Buprestes of the Cerceres; and this is why it has fallen to their lot to share among them the larvae of the Scarabaeidae.
Before they obtained their allotted portion, so closely restricted and so judiciously selected; before they discovered the precise and almost mathematical point at which the sting must enter to produce a sudden and a lasting immobility; before they learnt how to consume, without incurring the risk of putrefaction, so corpulent a prey: in brief, before they combined these three conditions of success, what did the Scoliae do?
The Darwinian school will reply that they were hesitating, essaying, experimenting. A long series of blind gropings eventually hit upon the most favourable combination, a combination henceforth to be perpetuated by hereditary transmission. The skilful co-ordination between the end and the means was originally the result of an accident.
Chance! A convenient refuge! I shrug my shoulders when I hear it invoked to explain the genesis of an instinct so complex as that of the Scoliae. In the beginning, you say, the creature gropes and feels its way; there is nothing settled about its preferences. To feed its carnivorous larvae it levies tribute on every species of game which is not too much for the huntress' power or the nurseling's appetite; its descendants try now this, now that, now something else, at random, until the accumulated centuries lead to the selection which best suits the race. Then habit grows fixed and becomes instinct.
Very well. Let us agree that the Scolia of antiquity sought a different prey from that adopted by the modern huntress. If the family throve upon a diet now discontinued, we fail to see that the descendants had any reason to change it: animals have not the gastronomic fancies of an epicure whom satiety makes difficult to please. Because the race did well upon this fare, it became habitual; and instinct became differently fixed from what it is to-day. If, on the other hand, the original food was unsuitable, the existence of the family was jeopardized; and any attempt at future improvement became impossible, because an unhappily inspired mother would leave no heirs.
To escape falling into this twofold trap, the theorists will reply that the Scoliae are descended from a precursor, an indeterminate creature, of changeable habits and changing form, modifying itself in accordance with its environment and with the regional and climatic conditions and branching out into races each of which has become a species with the attributes which distinguish it to-day. The precursor is the deus ex machina of evolution. When the difficulty becomes altogether too importunate, quick, a precursor, to fill up the gaps, quick, an imaginary creature, the nebulous plaything of the mind! This is seeking to lighten the darkness with a still deeper obscurity; to illumine the day by piling cloud upon cloud. Precursors are easier to find than sound arguments. Nevertheless, let us put the precursor of the Scoliae to the test.
What did she do? Being capable of everything, she did a bit of everything. Among its descendants were innovators who developed a taste for tunnelling in sand and vegetable mould. There they encountered the larvae of the Cetonia, the Oryctes, the Anoxia, succulent morsels on which to rear their families. By degrees the indeterminate Wasp adopted the sturdy proportions demanded by underground labour. By degrees she learnt to stab her plump neighbours in scientific fashion; by degrees she acquired the difficult art of consuming her prey without killing it; at length, by degrees, aided by the richness of her diet, she became the powerful Scolia with whom we are familiar. Having reached this point, the species assumes a permanent form, as does its instinct.
Here we have a multiplicity of stages, all of the slowest, all of the most incredible nature, whereas the Wasp cannot found a race except on the express condition of complete success from the first attempt. We will not insist further upon the insurmountable objection; we will admit that, amid so many unfavourable chances, a few favoured individuals survive, becoming more and more numerous from one generation to the next, in proportion as the dangerous art of rearing the young is perfected. Slight variations in one and the same direction form a definite whole; and at long last the ancient precursor has become the Scolia of our own times.
By the aid of a vague phraseology which juggles with the secret of the centuries and the unknown things of life, it is easy to build up a theory in which our mental sloth delights, after being discouraged by difficult researches whose final result is doubt rather than positive statement. But if, so far from being satisfied with hazy generalities and adopting as current coin the terms consecrated by fashion, we have the perseverance to explore the truth as far as lies in our power, the aspect of things will undergo a great change and we shall discover that they are far less simple than our overprecipitate views declared them to be. Generalization is certainly a most valuable instrument: science indeed exists only by virtue of it. Let us none the less beware of generalizations which are not based upon very firm and manifold foundations.
When these foundations are lacking, the child is the great generalizer. For him, the feathered world consists merely of birds; the race of reptiles merely of snakes, the only difference being that some are big and some are little. Knowing nothing, he generalizes in the highest degree; he simplifies, in his inability to perceive the complex. Later he will learn that the Sparrow is not the Bullfinch, that the Linnet is not the Greenfinch; he will particularize and to a greater degree each day, as his faculty of observation becomes more fully trained. In the beginning he saw nothing but resemblances; he now sees differences, but still not plainly enough to avoid incongruous comparisons.
In his adult years he will almost to a certainty commit zoological blunders similar to those which my gardener retails to me. Favier, an old soldier, has never opened a book, for the best of reasons. He barely knows how to cipher: arithmetic rather than reading is forced upon us by the brutalities of life. Having followed the flag over three-quarters of the globe, he has an open mind and a memory crammed with reminiscences, which does not prevent him, when we chat about animals, from making the most crazy assertions. For him the Bat is a Rat that has grown wings; the Cuckoo is a Sparrow-hawk retired from business; the Slug is a Snail who has lost his shell with the advance of years; the Nightjar (Known also as the Goatsucker, because of the mistaken belief that the bird sucks the milk of Goats, and, in America, as the Whippoorwill.—Translator's Note.), the Chaoucho-grapaou, as he calls her, is an elderly Toad, who, becoming enamoured of milk-food, has grown feathers, so that she may enter the byres and milk the Goats. It is impossible to drive these fantastic ideas out of his head. Favier himself, as will be seen, is an evolutionist after his own fashion, an evolutionist of a very daring type. In accounting for the origin of animals nothing gives him pause. He has a reply to everything: "this" comes from "that." If you ask him why, he answers:
"Look at the resemblance!"
Shall we reproach him with these insanities, when we hear another, misled by the Monkey's build, acclaim the Pithecanthropus as man's precursor? Shall we reject the metamorphosis of the Chaoucho-grapaou, when people tell us in all seriousness that, in the present stage of scientific knowledge, it is absolutely proved that man is descended from some rough-hewn Ape? Of the two transformations, Favier's strikes me as the more credible. A painter of my acquaintance, a brother of the great composer Felicien David (Felicien Cesar David (1810-1876). His chief work was the choral symphony "Le Desert":—Translator's Note.), favoured me one day with his reflections on the human structure:
"Ve, moun bel ami," he said. "Ve, l'home a lou dintre d'un por et lou defero d'uno mounino." "See, my dear friend, see: man has the inside of a pig and the outside of a monkey."
I recommend the painter's aphorism to those who might like to discover man's origin in the Hog when the Ape has gone out of fashion. According to David, descent is proved by internal resemblances:
"L'home a lou dintre d'un por."
The inventory of precursory types sees nothing but organic resemblances and disdains the differences of aptitude. By consulting only the bones, the vertebrae, the hair, the nervures of the wings, the joints of the antennae, the imagination may build up any sort of genealogical tree that will fit with our theories of classification, for, when all is said, the animal, in its widest generalization, is represented by a digestive tube. With this common factor, the way lies open to every kind of error. A machine is judged not by this or that train of wheels, but by the nature of the work accomplished. The monumental roasting-jack of a waggoners' inn and a Breguet chronometer both have trains of cogwheels geared in almost a similar fashion. (Louis Breguet (1803-1883), a famous Parisian watchmaker and physicist.—Translator's Note.) Are we to class the two mechanisms together? Shall we forget that the one turns a shoulder of mutton before the hearth, while the other divides time into seconds?
In the same way, the organic scaffolding is dominated from on high by the aptitudes of the animal, especially that superior characteristic, the psychical aptitudes. That the Chimpanzee and the hideous Gorilla possess close resemblances of structure to our own is obvious. But let us for a moment consider their aptitudes. What differences, what a dividing gulf! Without exalting ourselves as high as the famous reed of which Pascal speaks, that reed which, in its weakness, by the mere fact that it knows itself to be crushed, is superior to the world that crushes it, we may at least ask to be shown, somewhere, an animal making an implement, which will multiply its skill and its strength, or taking possession of fire, the primordial element of progress. (Blaise Pascal(1623-1662). The allusion is to a passage in the philosopher's "Pensees." Pascal describes man as a reed, the weakest thing in nature, but "a thinking reed."—Translator's Note.) Master of implements and of fire! These two aptitudes, simple though they be, characterize man better than the number of his vertebrae and his molars.
You tell us that man, at first a hairy brute, walking on all fours, has risen on his hind-legs and shed his fur; and you complacently demonstrate how the elimination of the hairy pelt was effected. Instead of bolstering up a theory with a handful of fluff gained or lost, it would perhaps be better to settle how the original brute became the possessor of implements and fire. Aptitudes are more important than hair; and you neglect them because it is there that the insurmountable difficulty really resides. See how the great master of evolution hesitates and stammers when he tries, by fair means or foul, to fit instinct into the mould of his formulae. It is not so easy to handle as the colour of the pelt, the length of the tail, the ear that droops or stands erect. Yes, our master well knows that this is where the shoe pinches! Instinct escapes him and brings his theory crumbling to the ground.
Let us return to what the Scoliae teach us on this question, which incidentally touches on our own origin. In conformity with the Darwinian ideas, we have accepted an unknown precursor, who by dint of repeated experiment, adopted as the victuals to be hoarded the larvae of the Scarabaeidae. This precursor, modified by varying circumstances, is supposed to have subdivided herself into ramifications, one of which, digging into vegetable mould and preferring the Cetonia to any other game inhabiting the same heap, became the Two-banded Scolia; another, also addicted to exploring the soil, but selecting the Oryctes, left as its descendant the Garden Scolia; and a third, establishing itself in sandy ground, where it found the Anoxia, was the ancestress of the Interrupted Scolia. To these three ramifications we must beyond a doubt add others which complete the series of the Scolia. As their habits are known to me only by analogy, I confine myself to mentioning them.
The three species at least, therefore, with which I am familiar would appear to be derived from a common precursor. To traverse the distance from the starting-point to the goal, all three have had to contend with difficulties, which are extremely grave if considered one by one and are aggravated even more by this circumstance, that the overcoming of one would lead to nothing unless the others were surmounted as successfully. Success, then, is contingent upon a series of conditions, each one of which offers almost no chance of victory, so that the fulfilment of them all becomes a mathematical absurdity if we are to invoke accident alone.
And, in the first place, how was it that the Scolia of antiquity, having to provide rations for her carnivorous family, adopted for her prey only those larvae which, owing to the concentration of their nervous systems, form so remarkable and so rare an exception in the insect order? What chance would hazard offer her of obtaining this prey, the most suitable of all because the most vulnerable? The chance represented by unity compared with the indefinite number of entomological species. The odds are as one to immensity.
Let us continue. The larva of the Scarabaeid is snapped up underground, for the first time. The victim protests, defends itself after its fashion, coils itself up and presents to the sting on every side a surface on which a wound entails no serious danger. And yet the Wasp, an absolute novice, has to select, for the thrust of its poisoned weapon, one single point, narrowly restricted and hidden in the folds of the larva's body. If she miscalculates, she may be killed: the larva, irritated by the smarting puncture, is strong enough to disembowel her with the tusks of its mandibles. If she escapes the danger, she will nevertheless perish without leaving any offspring, since the necessary provisions will be lacking. Salvation for herself and her race depends on this: whether at the first thrust she is able to reach the little nervous plexus which measures barely one-fiftieth of an inch in width. What chance has she of plunging her lancet into it, if there is nothing to guide her? The chance represented by unity compared with the number of points composing the victim's body. The odds are as one against immensity.
Let us proceed still further. The sting has reached the mark; the fat grub is deprived of movement. At what spots should the egg now be laid? In front, behind, on the sides, the back or the belly? The choice is not a matter of indifference. The young grub will pierce the skin of its provender at the very spot on which the egg was fixed; and, once an opening is made, it will go ahead without hesitation. If this point of attack is ill-chosen, the nurseling runs the risk of presently finding under its mandibles some essential organ, which should have been respected until the end in order to keep the victuals fresh. Remember how difficult it is to complete the rearing when the tiny larva is moved from the place chosen by the mother. The game promptly becomes putrid and the Scolia dies.
It is impossible for me to state the precise motives which lead to the adoption of the spot on which the egg is laid; I can perceive general reasons, but the details escape me, as I am not well enough versed in the more delicate questions of anatomy and entomological physiology. What I do know with absolute certainty is that the same spot is invariably chosen for laying the egg. With not a single exception, on all the victims extracted from the heap of garden mould—and they are numerous—the egg is fixed behind the ventral surface, on the verge of the brown patch formed by the contents of the digestive system.
If there be nothing to guide her, what chance has the mother of gluing her egg to this point, which is always the same because it is that most favourable to successful rearing? A very small point, represented by the ratio of two or three square millimetres (About 1/100 square inch.—Translator's Note.) to the entire surface of the victim's body.
Is this all? Not yet. The grub is hatched; it pierces the belly of the Cetonia-larva at the requisite point; it plunges its long neck into the entrails, ransacking them and filling itself to repletion. If it bite at random, if it have no other guide in the selection of tit-bits than the preference of the moment and the violence of an imperious appetite, it will infallibly incur the danger of being poisoned by putrid food, for the victim, if wounded in those organs which preserve a remnant of life in it, will die for good and all at the first mouthfuls.
The ample joint must be consumed with prudent skill: this part must be eaten before that and, after that, some other portion, always according to method, until the time approaches for the last bites. This marks the end of life for the Cetonia, but it also marks the end of the Scolia's feasting. If the grub be a novice in the art of eating, if no special instinct guide its mandibles in the belly of the prey, what chance has it of completing its perilous meal? As much as a starving Wolf would have of daintily dissecting his Sheep, when he tears at her gluttonously, rends her into shreds and gulps them down.
These four conditions of success, with chance so near to zero in each case, must all be realized together, or the grub will never be reared. The Scolia may have captured a larva with close-packed nerve-centres, a Cetonia-grub, for instance; but this will go for nothing unless she direct her sting towards the only vulnerable point. She may know the whole secret of the art of stabbing her victim, but this means nothing if she does not know where to fasten her egg. The suitable spot may be found, but all the foregoing will be useless if the grub be not versed in the method to be followed in devouring its prey while keeping it alive. It is all or nothing.
Who would venture to calculate the final chance on which the future of the Scolia, or of her precursor, is based, that complex chance whose factors are four infinitely improbable occurrences, one might almost say four impossibilities? And such a conjunction is supposed to be a fortuitous result, to which the present instinct is due! Come, come!
From another point of view again, the Darwinian theory is at variance with the Scoliae and their prey. In the heap of garden mould which I exploited in order to write this record, three kinds of larvae dwell together, belonging to the Scarabaeid group: the Cetonia, the Oryctes and Scarabeus pentodon. Their internal structure is very nearly similar; their food is the same, consisting of decomposing vegetable matter; their habits are identical: they live underground in tunnels which are frequently renewed; they make a rough egg-shaped cocoon of earthy materials. Environment, diet, industry and internal structure are all similar; and yet one of these three larvae, the Cetonia's, reveals a most singular dissimilarity from its fellow-trenchermen: alone among the Scarabaeidae and, more than that, alone in all the immense order of insects, it walks upon its back.
If the differences were a matter of a few petty structural details, falling within the finical department of the classifier, we might pass them over without hesitation; but a creature that turns itself upside down in order to walk with its belly in the air and never adopts any other method of locomotion, though it possesses legs and good legs at that, assuredly deserves examination. How did the animal acquire its fantastic mode of progress and why does it think fit to walk in a fashion the exact contrary of that adopted by other beasts?
To these questions the science now in fashion always has a reply ready: adaptation to environment. The Cetonia-larva lives in crumbling galleries which it bores in the depths of the soil. Like the sweep who obtains a purchase with his back, loins and knees to hoist himself up the narrow passage of a chimney, it gathers itself up, applies the tip of its belly to one wall of its gallery and its sturdy back to another; and the combined effort of these two levers results in moving it forward. The legs, which are used very little, indeed hardly at all, waste away and tend to disappear, as does any organ which is left unemployed; the back, on the other hand, the principal motive agent, grows stronger, is furrowed with powerful folds and bristles with grappling-hooks or hairs; and gradually, by adaptation to its environment, the creature loses the art of walking, which it does not practise, and replaces it by that of crawling on its back, a form of progress better suited to underground corridors.
So far so good. But now tell me, if you please, why the larvae of the Oryctes and the Scarabaeus, living in vegetable mould, the larva of the Anoxia, dwelling in the sand, and the larva of the Cockchafer in our cultivated fields have not also acquired the faculty of walking on their backs? In their galleries they follow the chimney-sweep's methods quite as cleverly as the Cetonia-grub; to move forward they make valiant use of their backs without yet having come to ambling with their bellies in the air. Can they have neglected to accommodate themselves to the demands of their environment? If evolution and environment cause the topsy-turvy progress of the one, I have the right, if words have any meaning whatever, to demand as much of the others, since their organization is so much alike and their mode of life identical.
I have but little respect for theories which, when confronted with two similar cases, are unable to interpret the one without contradicting the other. They make me laugh when they become merely childish. For example: why has the tiger a coat streaked black and yellow? A matter of environment, replies one of our evolutionary masters. Ambushed in bamboo thickets where the golden radiance of the sun is intersected by stripes of shadow cast by the foliage, the animal, the better to conceal itself, assumed the colour of its environment. The rays of the sun produced the tawny yellow of the coat; the stripes of shadow added the black bars.
And there you have it. Any one who refuses to accept the explanation must be very hard to please. I am one of these difficult persons. If it were a dinner-table jest, made over the walnuts and the wine, I would willingly sing ditto; but alas and alack, it is uttered without a smile, in a solemn and magisterial manner, as the last word in science! Toussenel, in his day, asked the naturalists an insidious question. (Alphonse Toussenel (1803-1885), the author of a number of learned and curious works on ornithology.—Translator's Note.) Why, he enquired, have Ducks a little curly feather on the rump? No one, so far as I know, had an answer for the teasing cross-examiner: evolution had not been invented then. In our time the reason why would be forthcoming in a moment, as lucid and as well-founded as the reason why of the tiger's coat.
Enough of childish nonsense. The Cetonia-grub walks on its back because it has always done so. The environment does not make the animal; it is the animal that is made for the environment. To this simple philosophy, which is quite antiquated nowadays, I will add another, which Socrates expressed in these words:
"What I know best is that I know nothing."
CHAPTER 6. THE TACHYTES.
The family of Wasps whose name I inscribe at the head of this chapter has not hitherto, so far as I know, made much noise in the world. Its annals are limited to methodical classifications, which make very poor reading. The happy nations, men say, are those which have no history. I accept this, but I also admit that it is possible to have a history without ceasing to be happy. In the conviction that I shall not disturb its prosperity, I will try to substitute the living, moving insect for the insect impaled in a cork-bottomed box.
It has been adorned with a learned name, derived from the Greek Tachytes, meaning rapidity, suddenness, speed. The creature's godfather, as we see, had a smattering of Greek; its denomination is none the less unfortunate: intended to instruct us by means of a characteristic feature, the name leads us astray. Why is speed mentioned in this connection? Why a label which prepares the mind for an exceptional velocity and announces a race of peerless coursers? Nimble diggers of burrows and eager hunters the Tachytes are, to be sure, but they are no better than a host of rivals. Not the Sphex, nor the Ammophila, nor the Bembex, nor many another would admit herself beaten in either flying or running. At the nesting-season, all this tiny world of huntresses is filled with astounding activity. The quality of a speedy worker being common to all, none can boast of it to the exclusion of the rest.
Had I had a vote when the Tachytes was christened, I should have suggested a short, harmonious, well-sounding name, meaning nothing else than the thing meant. What better, for example, than the term Sphex? The ear is satisfied and the mind is not corrupted by a prejudice, a source of error to the beginner. I have not nearly as much liking for Ammophila, which represents as a lover of the sands an animal whose establishments call for compact soil. In short, if I had been forced, at all costs, to concoct a barbarous appellation out of Latin or Greek in order to recall the creature's leading characteristic, I should have attempted to say, a passionate lover of the Locust.
Love of the Locust, in the broader sense of the Orthopteron, an exclusive, intolerant love, handed down from mother to daughter with a fidelity which the centuries fail to impair, this, yes, this indeed depicts the Tachytes with greater accuracy than a name smacking of the race-course. The Englishman has his roast-beef; the German his sauerkraut; the Russian his caviare; the Neapolitan his macaroni; the Piedmontese his polenta; the man of Carpentras his tian. The Tachytes has her Locust. Her national dish is also that of the Sphex, with whom I boldly associate her. The methodical classifier, who works in cemeteries and seems to fly the living cities, keeps the two families far removed from each other because of considerations and attaching to the nervures of the wings and the joints of the palpi. At the risk of passing for a heretic, I bring them together at the suggestion of the menu-card.
To my own knowledge, my part of the country possesses five species, one and all addicted to a diet of Orthoptera. Panzer's Tachytes (T. Panzeri, VAN DER LIND), girdled with red at the base of the abdomen, must be pretty rare. I surprise her from time to time working on the hard roadside banks and the trodden edges of the footpaths. There, to a depth of an inch at most, she digs her burrows, each isolated from the rest. Her prey is an adult, medium-sized Acridian (Locust or Grasshopper.—Translator's Note.), such as the White-banded Sphex pursues. The captive of the one would not be despised by the other. Gripped by the antennae, according to the ritual of the Sphex, the victim is trailed along on foot and laid beside the nest, with the head pointing towards the opening. The pit, prepared in advance, is closed for the time being with a tiny flagstone and some bits of gravel, in order to avoid either the invasion of a passer-by or obstruction by landslips during the huntress' absence. A like precaution is taken by the White-banded Sphex. Both observe the same diet and the same customs.
The Tachytes clears the entrance to the home and goes in alone. She returns, puts out her head and, seizing her prey by the antennae, warehouses it by dragging backwards. I have repeated, at her expense, the tricks which I used to play on the Sphex. (For the author's experiments with the Languedocian, the Yellow-winged and the White-edged Sphex, cf. "The Hunting Wasps": chapter 11.—Translator's Note.) While the Tachytes is underground, I move the game away. The insect comes up again and sees nothing at its door; it comes out and goes to fetch its Locust, whom it places in position as before. This done, it goes in again by itself. In its absence I once more pull back the prey. Fresh emergence of the Wasp, who puts things to rights and persists in going down again, still by herself, however often I repeat the experiment. Yet it would be very easy for her to put an end to my teasing: she would only have to descend straightway with her game, instead of leaving it for a moment on her doorstep. But, faithful to the usages of her race, she behaves as her ancestors behaved before her, even though the ancient custom happen to be unprofitable. Like the Yellow-winged Sphex, whom I have teased so often during her cellaring-operations, she is a narrow conservative, learning nothing and forgetting nothing.
Let us leave her to do her work in peace. The Locust disappears underground and the egg is laid upon the breast of the paralysed insect. That is all: one carcase for each cell, no more. The entrance is stopped at last, first with stones, which will prevent the trickling of the embankment into the chamber; next with sweepings of dust, under which every vestige of the subterranean house disappears. It is now done: the Tachytes will come here no more. Other burrows will occupy her, distributed at the whim of her vagabond humour.
A cell provisioned before my eyes on the 22nd of August, in one of the walls in the harmas, contained the finished cocoon a week later. (The harmas was the piece of enclosed waste land in which the author used to study his insects in their natural state. Cf. "The Life of the Fly," by J. Henri Fabre, translated by Alexander Teixeira de Mattos: chapter 1.—Translator's Note.) I have not noted many examples of so rapid a development. This cocoon recalls, in its shape and texture, that of the Bembex-wasps. It is hard and mineralized, this is to say, the warp and woof of silk are hidden by a thick encrustation of sand. This composite structure seems to me characteristic of the family; at all events I find it in the three species whose cocoons I know. If the Tachytes are nearly related to the Spheges in diet, they are far removed from them in the industry of their larvae. The first are workers in mosaic, encrusting a network of silk and sand; the second weave pure silk.
Of smaller size and clad in black with trimmings of silvery down on the edge of the abdominal segments, the Tarsal Tachytes frequents the ledges of soft limestone in fairly populous colonies. (T. tarsina, LEP.) (According to M. J. Perez, to whom I submitted the Wasp of which I am about to speak, this Tachytes might well be a new species, if it is not Lepelletier's T. tarsina or its equivalent, Panzer's T. unicolor. Any one wishing to clear up this point will always recognize the quarrelsome insect by its behaviour. A minute description seems useless to me in the type of investigation which I am pursuing.—Author's Note.) August and September are the season of her labours. Her burrows, very close to one another when an easily-worked vein presents itself, afford an ample harvest of cocoons once the site is discovered. In a certain gravel-pit in the neighbourhood, with vertical walls visited by the sun, I have been able within a short space of time to collect enough to fill the hollow of my hand completely. They differ from the cocoons of the preceding species only in their smaller size. The provisions consist of young Acridians, varying from about a quarter to half an inch in length. The adult insect does not appear in the assorted bags of game, being no doubt too tough for the feeble grub. All the carcases consist of Locust-larvae, whose budding wings leave the back uncovered and put one in mind of the short skirts of a skimpy jacket. Small so that it may be tender, the game is numerous so that it may suffice all needs. I count from two to four carcases to a cell. When the time comes we will discover the reason for these differences in the rations served.
The Mantis-killing Tachytes wears a red scarf, like her kinswoman, Panzer's Tachytes. (The Mantis-hunting Tachytes was submitted to examination by M. J. Perez, who failed to recognize her. This species may well be new to our fauna. I confine myself to calling her the Mantis-killing Tachytes and leave to the specialists the task of adorning her with a Latin name, if it be really the fact that the Wasp is not yet catalogued. I will be brief in my delineation. To my thinking the best description is this: mantis-hunter. With this information it is impossible to mistake the insect, in my district of course. I may add that it is black, with the first two abdominal segments, the legs and the tarsi a rusty red. Clad in the same livery and much smaller than the female, the male is remarkable for his eyes, which are of a beautiful lemon-yellow when he is alive. The length is nearly half an inch for the female and a little more than half this for the male.—Author's Note.) I do not think that she is very widely distributed. I made her acquaintance in the Serignan woods, where she inhabits, or rather used to inhabit—for I fear that I have depopulated and even destroyed the community by my repeated excavations—where she used to inhabit one of those little mounds of sand which the wind heaps up against the rosemary clumps. Outside this small community, I never saw her again. Her history, rich in incident, will be given with all the detail which it deserves. I will confine myself for the moment to mentioning her rations, which consist of Mantis-larvae, those of the Praying Mantis predominating. (Cf. "The Life of the Grasshopper": chapters 6 to 9.—Translator's Note.) My lists record from three to sixteen heads for each cell. Once again we note a great inequality of rations, the reason for which we must try to discover.
What shall I say of the Black Tachytes (T. nigra, VAN DER LIND) that I have not already said in telling the story of the Yellow-winged Sphex? ("The Hunting Wasps": chapters 4 to 6.—Translator's Note.) I have there described her contests with the Sphex, whose burrow she seems to me to have usurped; I show her dragging along the ruts in the roads a paralysed Cricket, seized by the hauling-ropes, his antennae; I speak of her hesitations, which lead me to suspect her for a homeless vagabond, and finally on her surrender of her game, with which she seems at once satisfied and embarrassed. Save for the dispute with the Sphex, an unique event in my records as observer, I have seen all the rest many a time, but never anything more. The Black Tachytes, though the most frequent of all in my neighbourhood, remains a riddle to me. I know nothing of her dwelling, her larvae, her cocoons, her family-arrangements. All that I can affirm, judging by the invariable nature of the prey which one sees her dragging along, is that she must feed her larvae on the same non-adult Cricket that the Yellow-winged Sphex chooses for hers.
Is she a poacher, a pillager of other's property, or a genuine huntress? My suspicions are persistent, though I know how chary a man should be of suspicions. At one time I had my doubts about Panzer's Tachytes, whom I grudged a prey to which the White-banded Sphex might have laid claim. To-day I have no such doubts: she is an honest worker and her game is really the result of her hunting. While waiting for the truth to be revealed and my suspicions set aside, I will complete the little that I know of her by noting that the Black Tachytes passes the winter in the adult form and away from her cell. She hibernates, like the Hairy Ammophila. In warm, sheltered places, with low, perpendicular, bare banks, dear to the Wasps, I am certain of finding her at any time during the winter, however briefly I investigate the earthen surface, riddled with galleries. I find the Tachytes cowering singly in the hot oven formed by the end of a tunnel. If the temperature be mild and the sky clear, she emerges from her retreat in January and February and comes to the surface of the bank to see whether spring is making progress. When the shadows fall and the heat decreases, she reenters her winter-quarters.
The Anathema Tachytes (T. anathema, VAN DER LIND), the giant of her race, almost as large as the Languedocian Sphex and, like her, decorated with a red scarf round the base of the abdomen, is rarer than any of her congeners. I have come upon her only some four or five times, as an isolated individual and always in circumstances which will tell us of the nature of her game with a probability that comes very near to certainty. She hunts underground, like the Scoliae. In September I see her go down into the soil, which has been loosened by a recent light shower; the movement of the earth turned over keeps me informed of her subterranean progress. She is like the Mole, ploughing through a meadow in pursuit of his White Worm. She comes out farther on, nearly a yard from the spot at which she went in. This long journey underground has taken her only a few minutes.
Is this due to extraordinary powers of excavation on her part? By no means: the Anathema Tachytes is an energetic tunneller, no doubt, but, after all, is incapable of performing so great a labour in so short a time. If the underground worker is so swift in her progress, it is because the track followed has already been covered by another. The trail is ready prepared. We will describe it, for it is clearly defined before the intervention of the Wasp.
On the surface of the ground, for a length of two paces at most, runs a sinuous line, a beading of crumbled soil, roughly the width of my finger. From this line of ramifications (others) shoot out to left and right, much shorter and irregularly distributed. One need not be a great entomological scholar to recognize, at the first glance, in these pads of raised earth, the trail of a Mole-cricket, the Mole among insects. It is the Mole-cricket who, seeking for a root to suit her, has excavated the winding tunnel, with investigation-galleries grafted to either side of the main road. The passage is free therefore, or at most blocked by a few landslips, of which the Tachytes will easily dispose. This explains her rapid journey underground.
But what does she do there? For she is always there, in the few observations which chance affords me. A subterranean excursion would not attract the Wasp if it had no object. And its object is certainly the search for some sort of game for her larvae. The inference becomes inevitable: the Anathema Tachytes, who explores the Mole-cricket's galleries, gives her larvae this same Mole-cricket as their food. Very probably the specimen selected is a young one, for the adult insect would be too big. Besides, to this consideration of quantity is added that of quality. Young and tender flesh is highly appreciated, as witness the Tarsal Tachytes, the Black Tachytes and the Mantis-killing Tachytes, who all three select game that is not yet made tough by age. It goes without saying that the moment the huntress emerged from the ground I proceeded to dig up the track. The Mole-cricket was no longer there. The Tachytes had come too late; and so had I.
Well, how right was I to define the Tachytes as a Locust lover! What constancy in the gastronomic rules of the race! And what tact in varying the game, while keeping within the order of the Orthoptera! What have the Locust, the Cricket, the Praying Mantis and the Mole-cricket in common, as regards their general appearance? Why, absolutely nothing! None of us, if he were unfamiliar with the delicate associations dictated by anatomy, would think of classing them together. The Tachytes, on the other hand, makes no mistake. Guided by her instinct, which rivals the science of a Latreille, she groups them all together. (Pierre Andre Latreille (1762-1833), one of the founders of entomological science, a professor at the Musee d'histoire naturelle and member of the Academie des sciences.—Translator's Note.)
This instinctive taxonomy becomes more surprising still if we consider the variety of the game stored in a single burrow. The Mantis-killing Tachytes, for instance, preys indiscriminately upon all the Mantides that occur in her neighbourhood. I see her warehousing three of them, the only varieties, in fact, that I know in my district. They are the following: the Praying Mantis (M. religiosa, LIN.), the Grey Mantis (Ameles decolor, CHARP. (Cf. "The Life of the Grasshopper": chapter 10.—Translator's Note.)) and the Empusa (E. pauperata, LATR. (Cf. idem: chapter 9.—Translator's Note.)). The numerical predominance in the Tachytes' cells belongs to the Praying Mantis; and the Grey Mantis occupies second place. The Empusa, who is comparatively rare on the brushwood in the neighbourhood, is also rare in the store-houses of the Wasp; nevertheless her presence is repeated often enough to show that the huntress appreciates the value of this prey when she comes across it. The three sorts of game are in the larval state, with rudimentary wings. Their dimensions, which vary a good deal, fluctuate between two-fifths and four-fifths of an inch in length.
The Praying Mantis is a bright green; she boasts an elongated prothorax and an alert gait. The other Mantis is ash-grey. Her prothorax is short and her movements heavy. The coloration therefore is no guide to the huntress, any more than the gait. The green and the grey, the swift and the slow are unable to baffle her perspicacity. To her, despite the great difference in appearance, the two victims are Mantes. And she is right.
But what are we to say of the Empusa? The insect world, at all events in our parts, contains no more fantastic creature. The children here, who are remarkable for finding names which really depict the animal, call the larva "the Devilkin." It is indeed a spectre, a diabolical phantom worthy of the pencil of a Callot. (Jacques Callot (1592-1635), the French engraver and painter, famous for the grotesque nature of his subjects.—Translator's Note.) There is nothing to beat it in the extravagant medley of figures in his "Temptation of Saint Anthony." Its flat abdomen, scalloped at the edges, rises into a twisted crook; its peaked head carries on the top two large, divergent, tusk-shaped horns; its sharp, pointed face, which can turn and look to either side, would fit the wily purpose of some Mephistopheles; its long legs have cleaver-like appendages at the joints, similar to the arm-pieces which the knights of old used to bear upon their elbows. Perched high upon the shanks of its four hind-legs, with its abdomen curled, its thorax raised erect, its front-legs, the traps and implements of warfare, folded against its chest, it sways limply from side to side, on the tip of the bough.
Any one seeing it for the first time in its grotesque pose will give a start of surprise. The Tachytes knows no such alarm. If she catches sight of it, she seizes it by the neck and stabs it. It will be a treat for her children. How does she manage to recognize in this spectre the near relation of the Praying Mantis? When frequent hunting-expeditions have familiarized her with the last-named and suddenly, in the midst of the chase, she encounters the Devilkin, how does she become aware that this strange find makes yet another excellent addition to her larder? This question, I fear, will never receive an adequate reply. Other huntresses have already set us the problem; others will set it to us again. I shall return to it, not to solve it, but to show even more plainly how obscure and profound it is. But we will first complete the story of the Mantis-killing Tachytes.
The colony which forms the subject of my investigations is established in a mound of fine sand which I myself cut into, a couple of years ago, in order to unearth a few Bembex larvae. The entrances to the Tachytes' dwelling open upon the little upright bank of the section. At the beginning of July the work is in full swing. It must have been going on already for a week or two, for I find very forward larvae, as well as recent cocoons. There are here, digging into the sand or returning from expeditions with their booty, some hundred females, whose burrows, all very close to one another, cover an area of barely a square yard. This hamlet, small in extent, but nevertheless densely populated, shows us the Mantis-slayer under a moral aspect which is not shared by the Locust slayer, Panzer's Tachytes, who resembles her so closely in costume. Though engaged in individual tasks, the first seeks the society of her kind, as do certain of the Sphex-wasps, while the second establishes herself in solitude, after the fashion of the Ammophila. Neither the personal form nor the nature of the occupation determines sociability.
Crouching voluptuously in the sun, on the sand at the foot of the bank, the males lie waiting for the females, to plague them as they pass. They are ardent lovers, but cut a poor figure. Their linear dimensions are barely half those of the other sex, which implies a volume only one-eighth as great. At a short distance they appear to wear on their heads a sort of gaudy turban. At close quarters this headgear is seen to consist of the eyes, which are very large and a bright lemon-yellow and which almost entirely surround the head.
At ten o'clock in the morning, when the heat begins to grow intolerable to the observer, there is a continual coming and going between the burrows and the tufts of grass, everlasting, thyme and wormwood, which constitute the Tachytes' hunting-grounds within a moderate radius. The journey is so short that the Wasp brings her game home on the wing, usually in a single flight. She holds it by the fore-part, a very judicious precaution, which is favourable to rapid stowage in the warehouse, for then the Mantis' legs stretch backwards, along the axis of the body, instead of folding and projecting sideways, when their resistance would be difficult to overcome in a narrow gallery. The lanky prey dangles beneath the huntress, all limp, lifeless and paralysed. The Tachytes, still flying, alights on the threshold of the home and immediately, contrary to the custom of Panzer's Tachytes, enters with her prey trailing behind her. It is not unusual for a male to come upon the scene at the moment of the mother's arrival. He is promptly snubbed. This is the time for work, not for amusement. The rebuffed male resumes his post as a watcher in the sun; and the housewife stows her provisions. |
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