"The Hunting Wasps": chapters 13 and 18 to 20.—Translator's Note.)
My readers may differ in appraising the comparative value of the trifling discoveries which entomology owes to my labours. The geologist, the recorder of forms, will prefer the hypermetamorphosis of the Oil-beetles (The chapter treating of this subject has not yet been translated into English and will appear in a later volume.—Translator's Note.), the development of the Anthrax (Cf. "The Life of the Fly": chapter 2.—Translator's Note.) or larval dimorphism; the embryogenist, searching into the mysteries of the egg, will have some esteem for my enquiries into the egg-laying habits of the Osmia (Cf. "Bramble-bees and Others": chapter 4.—Translator's Note.); the philosopher, racking his brain over the nature of instinct, will award the palm to the operations of the Hunting Wasps. I agree with the philosopher. Without hesitation, I would abandon all the rest of my entomological baggage for this discovery, which happens to be the earliest in date and that of which I have the fondest memories. Nowhere do I find a more brilliant, more lucid, more eloquent proof of the intuitive wisdom of instinct; nowhere does the theory of evolution suffer a more obstinate check.
Darwin, a true judge, made no mistake about it. (Charles Robert Darwin, born the 12th of February, 1809, at Shrewsbury, died at Down, in Kent, on the 19th of April, 1882. For an account of certain experiments which the author conducted on his behalf, cf. "The Mason-bees": chapter 4.—Translator's Note.) He greatly dreaded the problem of the instincts. My first results in particular left him very anxious. If he had known the tactics of the Hairy Ammophila, the Mantis-hunting Tachytes, the Bee-eating Philanthus, the Calicurgi and other marauders, his anxiety, I believe, would have ended in a frank admission that he was unable to squeeze instinct into the mould of his formula. Alas, the philosopher of Down quitted this world when the discussion, with experiments to support it, had barely begun: a method superior to any argument! The little that I had published at that time left him with still some hope of an explanation. In his eyes, instinct was always an acquired habit. The predatory Wasps killed their prey at first by stabbing it at random, here and there, in the softest parts. By degrees they found the spot where the sting was most effectual; and the habit once formed became a true instinct. Transitions from one method of operation to the other, intermediary changes, sufficed to bolster up these sweeping assertions. In a letter of the 16th of April, 1881, he asks G.J. Romanes to consider the problem:
"I do not know," he says "whether you will discuss in your book on the mind of animals any of the more complex and wonderful instincts. It is unsatisfactory work, as there can be no fossilised instincts, and the sole guide is their state in other members of the same order, and mere PROBABILITY.
"But if you do discuss any (and it will perhaps be expected of you), I should think that you could not select a better case than that of the sand-wasps which paralyse their prey as described by Fabre in his wonderful paper in the 'Anales des sciences naturelles,' and since amplified in his admirable 'Souvenirs...'"
I thank you, O illustrious master, for your eulogistic expressions, proving the keen interest which you took in my studies of instinct, no ungrateful task—far from it—when we tackle it as it should be tackled: from the front, with the aid of facts, and not from the flank, with the aid of arguments. Arguments are here out of place, if we wish to maintain our position in the light. Besides, where would they lead us? To evoking the instincts of bygone ages, which have not been preserved by fossilization? Any such appeal to the dim and distant past is quite unnecessary, if we wish for variations of instinct, leading by degrees, according to you, from one instinct to another; the present world offers us plenty.
Each operator has her particular method, her particular kind of game, her particular points of attack and tricks of fence; but in the midst of this variety of talents we observe, immutable and predominant, the perfect accordance of the surgery with the victim's organization and the larva's needs. The art of one will not explain the art of another, no less exact in the delicacy of its rules. Each operator has her own tactics, which tolerate no apprenticeship. The Ammophila, the Scolia, the Philanthus and the others all tell us the same thing: none can leave descendants if she be not from the outset the skilful paralyser or slayer that she is to-day. The "almost" is impracticable when the future of the race is at stake. What would have become of the first-born mammal but for its perfect instinct of suckling?
And then, to suppose the impossible: a Wasp discovers by chance the operative method which will be the saving attribute of her race. How are we to admit that this fortuitous act, to which the mother has vouchsafed no more attention than to her other less fortunate attempts, could leave a profound trace behind it and be faithfully transmitted by heredity? Is it not going beyond reason, going beyond the little that is known to us as certain, if we grant to atavism this strange power, of which our present world knows no instance? There is a good deal to be said for this point of view, my revered master! But, once more, arguments are here out of place; there is room only for facts, of which I will resume the recital.
Hitherto I had but one means of studying the operative methods of the spoilers: to surprise the Wasp in possession of her capture, to rob her of her prey and immediately to give her in exchange a similar prey, but a living one. This method of substitution is an excellent expedient. Its only defect—a very grave one—is that it subjects observation to very uncertain chances. There is little prospect of meeting the insect dragging its victim along; and, in the second place, should good fortune suddenly smile upon you, preoccupied as you are with other matters you have not the substitute at hand. If we provide ourselves with the necessary head of game in advance, the huntress is not there. We avoid one reef to founder on another. Moreover, these unlooked for observations, made sometimes on the public highway, the worst of laboratories, are only half-satisfactory. In the case of swiftly-enacted scenes, which it is not in our power to renew again and again until perfect conviction is reached, we always fear lest we may not have seen accurately, may not have seen everything.
A method which could be controlled at will would offer the best guarantees, above all if employed at home, under comfortable conditions, favourable to precision. I wished, therefore, to see my insects at work on the actual table at which I am writing their history. Here very few of their secrets would escape me. This wish of mine was an old one. As a beginner, I made some experiments under glass with the Great Cerceris (C. tuberculata) and the Yellow-winged Sphex. Neither of them responded to my desires. The refusal of each to attack respectively her Cleonus or her Cricket discouraged further progress in this direction. I was wrong to abandon my attempts so soon. Now, very long afterwards, the idea occurs to me to place under glass the Bee-eating Philanthus, whom I sometimes surprise in the open engaged in forcing a bee to disgorge her honey. The captive massacres her bees in such a spirited fashion that the old hope revives stronger than ever. I contemplate reviewing all the wielders of the stiletto and forcing each to reveal her tactics.
I was obliged to abate these ambitions considerably. I had some successes and many more failures. I will tell you of the former. My insect-cage is a spacious dome of wire-gauze resting on a bed of sand. Here I keep in reserve the captives of my hunting-expeditions. I feed them on honey, placed in little drops on spikes of lavender, on heads of thistle, or field eryngo, or globe-thistle, according to the season. Most of my prisoners do well on this diet and seem scarcely affected by their internment; others pine away and die in two or three days. These victims of despair nearly always throw me back, because of the difficulty of obtaining the necessary prey at short notice.
Indeed it entails no small trouble to secure in the nick of time the game demanded by the huntress who has recently fallen a captive to my net. As assistant-purveyors I have a few small schoolboys, who, released from the tedium of their declensions and conjugations, set out, on leaving the classroom, to inspect the greenswards and beat the bushes in the neighbourhood on my behalf. The gros sou, the penny-piece, if you please, stimulates their zeal; but with misadventurous results! What I need to-day is Crickets. The band sallies forth and returns with not a single Cricket, but numbers of Ephippigers, for which I asked the day before yesterday and which I no longer need, my Languedocian Sphex being dead. General surprise at this sudden change of market. My young scatterbrains find it hard to understand that the beast which was so precious two days ago is now of no value whatever. When, owing to the chances of my net, a renewed demand for the Ephippiger sets in, then they will bring me the Cricket, the despised Cricket.
Such a trade could never hold out if now and again my speculators were not encouraged by some success. At the moment when urgent necessity is sending up prices, one of them brings me a magnificent Gad-fly intended for the Bembex. For two hours, when the sun was at its height, he kept watch on the threshing-floor hard by, waiting for the blood-sucker, in order to catch him on the buttocks of the Mules which trot round and round trampling the corn. This gallant fellow shall have his gros sou and a slice of bread and jam as well. A second, no less fortunate, has found a fat Spider, the Epeira, for whom my Pompili are waiting. To the two sous of this fortunate youth I add a little picture for his missal. Thus are my purveyors kept going; and, after all, their help would be very inadequate if I did not take upon myself the main burden of these wearisome quests.
Once in possession of the requisite prey, I transfer the huntress from my warehouse, the wire-gauze cage, to a bell-glass varying in capacity from one to three or four litres (1 3/4 to 5 or 7 pints.—Translator's Note.), according to the size and habits of the combatants; I place the victim in the arena; I expose the bell-glass to the direct rays of the sun, without which condition the executioner as a rule declines to operate; I arm myself with patience and await events.
We will begin with the Hairy Ammophila, my neighbour. Year after year, when April comes, I see her in considerable numbers, very busy on the paths in my enclosure. Until June I see her digging her burrows and searching for the Grey Worm, to be placed in the meat-cellar. Her tactics are the most complex that I know and more than any other deserves to be thoroughly studied. To capture the cunning vivisector, to release her and catch her again I find an easy matter for the best part of a month; she works outside my door.
I have still to obtain the Grey Worm. This means a repetition of the disappointments which I had before, when, to find a caterpillar, I was obliged to watch the Ammophila while hunting and to be guided by her hints, as the truffle-hunter is guided by the scent of his Dog. A patient exploration of the harmas, one tuft of thyme after another, does not give me a single worm. My rivals in this search are finding their game at every moment; I cannot find it even once. Yet one more reason for bowing to the superiority of the insect in the management of her affairs. My band of schoolboys get to work in the surrounding fields. Nothing, always nothing! I in my turn explore the outer world; and for ten days the pursuit of a caterpillar torments me till I lose my power of sleep. Then, at last, victory! At the foot of a sunny wall, under the budding rosettes of the panicled centaury, I find a fair supply of the precious Grey Worm or its equivalent.
Behold the worm and the Ammophila face to face beneath the bell-glass. Usually the attack is prompt enough. The caterpillar is grabbed by the neck with the mandibles, wide, curved pincers capable of embracing the greater part of the living cylinder. The creature thus seized twists and turns and sometimes, with a blow of its tail, sends the assailant rolling to a distance. The latter is unconcerned and thrusts her sting thrice in rapid succession into the thorax, beginning with the third segment and ending with the first, where the weapon is driven home with greater determination than elsewhere.
The caterpillar is then released. The Ammophila stamps on the ground; with her quivering tarsi she taps the cardboard on which the bell-glass stands; she lies down flat, drags herself along, gets up again, flattens herself once more. The wings jerk convulsively. From time to time the insect places its mandibles and forehead on the ground, then rears high upon its hind-legs as though to turn head over heels. In all this I see a manifestation of delight. We rub our hands when rejoicing at a success; the Ammophila is celebrating her triumph over the monster in her own fashion. During this fit of delirious joy, what is the wounded caterpillar doing? It can no longer walk; but all the part behind the thorax struggles violently, curling and uncurling when the Ammophila sets a foot upon it. The mandibles open and shut menacingly.
SECOND ACT.—When the operation is resumed, the caterpillar is seized by the back. From front to rear, in order, all the segments are stung on the ventral surface, except the three operated on. All serious danger is averted by the stabs of the first act; therefore, the Wasp is now able to work upon her patient without the haste displayed at the outset. Deliberately and methodically she drives in her lancet, withdraws it, selects the spot, stabs it and begins again, passing from segment to segment, taking care, each time, to lay hold of the back a little more to the rear, in order to bring the segment to be paralysed within reach of the needle. For the second time, the caterpillar is released. It is absolutely inert, except the mandibles, which are still capable of biting.
THIRD ACT.—The Ammophila clasps the paralysed victim between her legs; with the hooks of her mandibles she seizes the back of its neck, at the base of the first thoracic segment. For nearly ten minutes she munches this weak spot, which lies close to the cerebral nerve-centres. The pincers squeeze suddenly but at intervals and methodically, as though the manipulator wished each time to judge of the effect produced; the squeezes are repeated until I am tired of trying to count them. When they cease, the caterpillar's mandibles are motionless. Then comes the transportation of the carcase, a detail which is not relevant in this place.
I have set forth the complete tragedy, as it is fairly often enacted, but not always. The insect is not a machine, unvarying in the effect of its mechanism; it is allowed a certain latitude, enabling it to cope with the eventualities of the moment. Any one expecting to see the incidents of the struggle unfolding themselves exactly as I have described will risk disappointment. Special instances occur—they are even numerous—which are more or less at variance with the general rule. It will be well to mention the more important, in order to put future observers on their guard.
Not infrequently the first act, that of paralysing the thorax, is restricted to two thrusts of the sting instead of three, or even to one, which is then delivered in the foremost segment. This, it would seem, from the persistency with which the Ammophila inflicts it, is the most important prick of all. Is it unreasonable to suppose that the operator, when she begins by pricking the thorax, intends to subdue her capture and to make it incapable of injuring her, or even of disturbing her when the moment comes for the delicate and protracted surgery of the second act? This idea seems to me highly admissible; and then, instead of three dagger-thrusts, why not two only, why not merely one, if this would suffice for the time being? The amount of vigour displayed by the caterpillar must be taken into consideration. Be this as it may, the segments spared in the first act are stabbed in the second. I have sometimes even seen the three thoracic segments stung twice over: at the beginning of the attack and again when the Wasp returned to her vanquished prey.
The Ammophila's triumphant transports beside her wounded and writhing victim are also subject to exceptions. Sometimes, without releasing its prey for a moment, the insect proceeds from the thorax to the next segments and completes its operation in a single spell. The joyous entr'acte does not take place; the convulsive movements of the wings and the acrobatic postures are suppressed.
The rule is paralysis of all the segments, however many, in regular order from front to back, including even the anal segment if this boast of legs. By a fairly frequent exception the last two or three segments are spared. Another exception, but a very rare one, of which I have observed only a single instance, consists in the inversion of the dagger-thrusts of the second act, the thrusts being delivered from back to front. The caterpillar is then seized by its hinder extremity; and the Ammophila, progressing towards the head, stings in reverse order, passing from the succeeding to the preceding segment, including the thorax already stabbed. This reversal of the usual tactics I am inclined to attribute to negligence on the insect's part. Negligence or not, the inverted method has the same final result as the direct method: the paralysis of all the segments.
Lastly, the compression of the neck by the mandibulary pincers, the munching of the weak spot between the base of the skull and the first segment of the thorax, is sometimes practised and sometimes neglected. If the caterpillar's jaws open and threaten, the Ammophila stills them by biting the neck; if they are already growing quiescent, she refrains. Without being indispensable, this operation is useful at the moment of carting the prey. The caterpillar, too heavy to be carried on the wing, is dragged, head first, between the Ammophila's legs. If the mandibles are working, the least clumsiness may render them dangerous to the carrier, who is exposed to their bite without any means of defence.
Moreover, once on the way, thickets of grass are traversed in which the Grey Worm can seize a blade and offer a desperate resistance to the traction. Nor is this all. The Ammophila does not as a rule trouble about her burrow, or at least does not complete it, until she has caught her caterpillar. During the mining-operations, the game is laid somewhere high up, out of reach of the Ants, on some tuft of grass, or the twigs of a shrub, whither the huntress, from time to time, stopping her well-sinking, hastens to see if her quarry is still there. For her this is a means of refreshing her memory of the spot where she has laid it, often at some distance from the burrow, and of preventing attempts at robbery. When the moment comes for removing the game from its hiding-place, the difficulty would be insurmountable were the worm, gripping the shrub with all the might of its jaws, to anchor itself there. Hence inertia of the powerful hooks, which are the paralysed creature's sole means of resistance, becomes essential during the carting. The Ammophila obtains it by compressing the cerebral ganglia, by munching the neck. The inertia is temporary; it wears off sooner or later; but by this time the carcase is in the cell and the egg, prudently laid at a distance on the ventral surface of the worm, has nothing to fear from the caterpillar's grapnels. No comparison is permissible between the methodical squeezes of the Ammophila benumbing the cephalic nerve-centres and the brutal manipulations of the Philanthus emptying the crop of her Bee. The huntress of Grey Worms induces a temporary torpor of the mandibles; the ravisher of Bees makes them eject their honey. No one gifted with the least perspicacity will confound the two operations.
For the moment we will not dwell any longer on the method of the Hairy Ammophila; we will see instead how her kinswomen behave. After protracted refusals the Sandy Ammophila (A. sabulosa, FAB.),on whom I experimented in September, ended by accepting the proffered prey, a powerful caterpillar as thick as a lead-pencil. The surgical method did not differ from that employed by the Hairy Ammophila when operating on her Grey Worm in one spell. All the segments, excepting the last three, were stung from front to back, beginning with the prothorax. This single success with a simplified method left me in ignorance of the accessory manoeuvres, which I do not doubt must more or less closely recall those of the preceding species.
I am all the more inclined to accept these secondary manoeuvres, not as yet recorded—the transports of triumph and the compressions of the neck—inasmuch as I see them practised upon the Looper caterpillars, which differ so greatly from the others in external structure, exactly as I have described them in the case of the Grey Worm, which is of the ordinary form. Two species, the Silky Ammophila (A. holoserica, FAB.) and Jules' Ammophila (See in the first volume of the "Souvenirs entomologiques" what I mean by this denomination.—Author's Note.), affect this curious prey, which moves with the stride of a pair of compasses. The first, often renewed under glass during the greater part of August, has always refused my offers; the second, her contemporary, has, on the contrary, promptly accepted them.
I present Jules' Ammophila with a slender, brownish Looper which I caught on the jasmine. The attack is not slow in coming. The caterpillar is grabbed by the neck: lively contortions of the victim, which rolls the aggressor over and drags her along, now uppermost, now undermost in the struggle. First the thorax is stung, in its three rings, from back to front. The sting lingers longest near the throat, in the first segment. This done, the Ammophila releases her victim and proceeds to stamp her tarsi, to polish her wings, to stretch herself. Again I observe the acrobatic postures, the forehead touching the ground, the hinder part of the body raised. This mimic triumph is the same as that of the huntress of the Grey Worm. Then the Looper is once more seized. Despite its contortions, which are not in the least abated by the three wounds in the thorax, it is stung from front to back in each segment still unwounded, no matter how many, whether supplied with legs or not. I expected to see the sting refrain more or less in the long interval which separates the true legs in front from the pro-legs at the back (Fleshy legs found on the abdominal segments of caterpillars and certain other larvae.—Translator's Note.): segments devoid of organs of defence or locomotion did not seem to me to deserve conscientious surgery. I was mistaken: not a segment of the Looper is spared, not even the last ones. It is true that these, being eminently capable of catching hold with their false legs, would be dangerous later were the Wasp to neglect them.
I observe, however, that the lancet works more rapidly in the second part of the operation than in the first, either because the caterpillar, half subjugated by the triple wound at the outset, is easier to reach with the sting, or because the segments more remote from the head are rendered harmless with a smaller injection of poison. Nowhere do we see repeated the care expended upon paralysing the thorax, still less the insistent attention to the first segment. On returning to her Looper after the entr'acte devoted to the joys of success, the Ammophila stabs so swiftly that, on one occasion, I saw her obliged to begin all over again. Lightly stung along its whole length, the victim still struggles. Without hesitation, the operator unsheathes her scalpel for the second time and operates on the Looper afresh, with the exception of the thorax, which was already sufficiently anaesthetized. This done, all is in order; there is no more movement.
After the stiletto the hooks of the mandibles rarely fail to intervene. Long and curved, they nibble at the paralysed victim's neck, sometimes from above, sometimes from below. It is a repetition of what the Hairy Ammophila showed us: the same sudden squeezes of the pincers, with rather long intervals between. These intervals, these measured bites and the insect's watchful attitude have every appearance of telling us that the operator is noting the effect produced before giving a fresh pinch of the nippers.
It will be seen how valuable is the evidence of Jules' Ammophila: it tells us that the immolaters of Looper caterpillars and those of ordinary caterpillars follow precisely the same method; that victims displaying very dissimilar external structure do not entail any modification of the operative tactics so long as the internal organization remains the same. The number, arrangement and degree of mutual independence of the nerve-centres guide the sting; the anatomy of the game, rather than its form, controls the huntress' tactics.
Let me mention, before I dismiss the subject, a superb example of this marvellous anatomical discrimination. I once took from between the legs of a Hairy Ammophila, which had just paralysed it, a caterpillar of Dicranura vinula. What a strange capture compared with the ordinary caterpillar! Bridling in thick folds beneath its pink neckerchief, its fore-part raised in a sphinx-like attitude, its hinder-part slowly waving two long caudal threads, the curious animal is no caterpillar to the schoolboy who brings it to me, nor to the man who comes upon it while cutting his bundle of osiers; but it is a caterpillar to the Ammophila, who treats it accordingly. I explore the queer creature's segments with the point of a needle. All are insensitive; all therefore have been stung.
After the Ammophilae, the paralysers who multiply their lancet-thrusts to destroy the influence of the various nerve-centres, excepting those of the head, it seemed advisable to interrogate other insects which also are accustomed to a naked prey, vulnerable at all points save the head, but which deliver only a single thrust of the sting. Of these two conditions the Scoliae fulfilled one, with their regular quarry, the tender Cetonia-, Oryctes-or Anoxia-larva, according to the Scolia's species. Did they fulfil the second? I was convinced beforehand that they did. From the anatomy of the victims, with their concentrated nervous system, I foresaw, when compiling my history of the Scoliae, that the sting would be unsheathed once only; I even mentioned the exact spot into which the weapon would be plunged.
These were assertions dictated by the anatomist's scalpel, without the slightest direct proof derived from observed facts. Manoeuvres executed underground escaped the eye, as it seemed to me that they must always do. How indeed could I hope that a creature whose art is practised in the darkness of a heap of mould would decide to work in broad daylight? I did not reckon upon it all. Nevertheless, to salve my conscience, I tried bringing the Scolia into contact with her prey under the bell-glass. I was well-advised to do so, for my success was in inverse ratio to my hopes. Next to the Philanthus, none of the Hunting Wasps displayed such ardour in attacking under artificial conditions. All the insects experimented upon, some sooner, some later, rewarded me for my patience. Let us watch the Two-banded Scolia (S. bifasciata, VAN DER LIND) operating on her Cetonia grub.
The incarcerated larva strives to escape its terrible neighbour. Lying on its back, it fiercely wends its way round and round the glass circus. Presently the Scolia's attention awakens and is betrayed by a continued tapping with the tips of the antennae upon the table, which now represents the accustomed soil. The Wasp attacks the game, delivering her assault upon the monster's hinder end. She climbs upon the Cetonia-grub, obtaining a purchase with the tip of her abdomen. The quarry merely travels the more quickly on its back, without coiling itself into a defensive posture. The Scolia reaches the fore-part, with tumbles and other accidents which vary greatly with the amount of tolerance displayed by the larva, her improvised steed. With her mandibles she nips a point of the thorax, on the upper surface; she places herself athwart the beast, arches herself and makes every effort to reach with the end of her abdomen the region into which the sting is to be driven. The arch is a little too narrow to embrace almost the whole circumference of her corpulent prey; and she renews her attempts and efforts for a long time. The tip of the belly tries every conceivable expedient, touching here, there and everywhere, but as yet stopping nowhere. This persistent search in itself demonstrates the importance which the paralyser attaches to the point at which her lancet is to penetrate the flesh.
Meanwhile, the larva continues to move along on its back. Suddenly it curls up; with a stroke of its head it hurls the enemy to a distance. Undiscouraged by all her set-backs, the Wasp picks herself up, brushes her wings and resumes her attack upon the colossus, almost always by mounting the larva's hinder end. At last after all these fruitless attempts, the Scolia succeeds in achieving the correct position. She is seated athwart the Cetonia-grub; the mandibles grip a point on the dorsal surface of the thorax; the body, bent into a bow, passes under the larva and with the tip of the belly reaches the region of the neck. The Cetonia-grub, placed in serious peril, writhes, coils and uncoils itself, spinning round upon its axis. The Scolia does not interfere. Holding the victim tightly gripped, she turns with it, allows herself to be dragged upwards, downwards, sidewards, following its contortions. Her obstinacy is such that I can now remove the bell-glass and follow the details of the drama in the open.
Briefly, in spite of the turmoil, the tip of the abdomen feels that the right spot has been found. Then and only then the sting is unsheathed. It plunges in. The thing is done. The larva, at first plump and active, suddenly becomes flaccid and inert. It is paralysed. Henceforth there are no movements save of the antennae and the mouthparts, which will for a long time yet bear witness to a remnant of life. The point wounded has never varied in the series of combats under glass: it occupies the middle of the line of demarcation between the prothorax and the mesothorax, on the ventral surface. Note that the Cerceres, operating on Weevils, whose nervous system is as compact as the Cetonia-grub's, drive in the needle at the same spot. Similarity of nervous organization occasions similarity of method. Note also that the Scolia's sting remains in the wound for some time and roots about with marked persistence. Judging by the movements of the tip of the abdomen, one would certainly say that the weapon is exploring and selecting. Free to shift in one direction or the other, within narrow limits, its point is most probably seeking for the little mass of nerve-tissue which must be pricked, or at least sprinkled with poison, to obtain overwhelming paralysis.
I will not close this report of the duel without relating a few further facts, of minor importance. The Two-banded Scolia is a fierce persecutor of the Cetonia. In one sitting the same mother stabs three larvae, one after the other, in front of my eyes. She refuses the fourth, perhaps owing to fatigue or to exhaustion of the poison-bag. Her refusal is only temporary. Next day, she begins again and paralyses two grubs; the day after that, she does the same, but with a zeal that decreases from day to day.
The other Hunting Wasps that pursue the chase far afield grip, drag, carry their prey, after depriving it of movement, each in her own fashion and, laden with their burden, make prolonged attempts to escape from the bell-glass and to gain the burrow. Discouraged by these futile endeavours, they abandon them at last. The Scolia does not remove her quarry, which lies on its back for an indefinite time on the actual spot of the sacrifice. When she has withdrawn her dagger from the wound, she leaves her victim where it lies and, without taking further notice of it, begins to flutter against the side of the glass. The paralysed carcase is not transported elsewhere, into a special cellar; there where the struggle has occurred it receives, upon its extended abdomen, the egg whence the consumer of the succulent tit-bit will emerge, thus saving the expense of setting up house. It goes without saying that under the bell-glass the laying does not take place: the mother is too cautious to abandon her egg to the perils of the open air.
Why then, recognizing the absence of her underground burrow, does the Scolia uselessly pursue the Cetonia with the frantic ardour of the Philanthus flinging herself upon the Bee? The action of the Philanthus is explained by her passion for honey; hence the murders committed in excess of the needs of her family. The Scolia leaves us perplexed: she takes nothing from the Cetonia-grub, which is left without an egg; she stabs, though well aware of the uselessness of her action: the heap of mould is lacking and it is not her custom to transport her prey. The other prisoners, once the blow is struck, at least seek to escape with their capture between their legs; the Scolia attempts nothing.
After due reflection, I lump together in my suspicions all these surgeons and ask myself whether they possess the slightest foresight, where the egg is concerned. When, exhausted by their burden, they recognize the impossibility of escape, the more expert among them ought not to begin all over again; yet they do so begin a few minutes later. These wonderful anatomists know absolutely nothing about anything, they do not even know what their victims are good for. Admirable artists in killing and paralysis, they kill or paralyse at every favourable opportunity, no matter what the final result as regards the egg. Their talent, which leaves our science speechless, has not a shadow of consciousness of the task accomplished.
A second detail strikes me: the desperate persistence of the Scolia. I have seen the struggle continue for more than a quarter of an hour, with frequent alternations of good luck and bad, before the Wasp achieved the required position and reached with the end of her abdomen the spot where the sting should penetrate. During these assaults, which were resumed as soon as they were repulsed, the aggressor repeatedly applied the tip of her belly to the larva, but without unsheathing, as I could see by the absence of the start which the larva gives when it feels the pain of the sting. The Scolia therefore does not prick the Cetonia anywhere until the weapon covers the requisite spot. If no wounds are inflicted elsewhere, this is not in any way due to the structure of the larva, which is soft and vulnerable all over, except in the head. The point sought by the sting is no more unprotected than any other part of the skin.
In the scuffle, the Scolia, curved into a bow, is sometimes seized by the vice-like grip of the Cetonia-grub, which is violently coiling and uncoiling. Heedless of the powerful grip, the Wasp does not let go for a moment, either with her mandibles or with the tip of her abdomen. At such times the two creatures, locked in a mutual embrace, turn over and over in a mad whirl, each of them now on top, now underneath. When it contrives to rid itself of its enemy, the larva uncoils again, stretches itself out and proceeds to make off upon its back with all possible speed. Its defensive ruses are exhausted. Formerly, before I had seen things for myself, taking probability as my guide I willingly granted to the larva the trick of the Hedgehog, who rolls himself into a ball and sets the Dog at defiance. Coiled upon itself, with an energy which my fingers have some difficulty in overcoming, the larva, I thought, would defy the Scolia, powerless to unroll it and disdaining any point but the one selected. I hoped and believed that it possessed this means of defence, a means both efficacious and extremely simple. I had presumed too much upon its ingenuity. Instead of imitating the Hedgehog and remaining contracted, it flees, belly in air; it foolishly adopts the very posture which allows the Scolia to mount to the assault and to reach the spot for the fatal stroke. The silly beast reminds me of the giddy Bee who comes and flings herself into the clutches of the Philanthus. Yet another who has learnt no lesson from the struggle for life.
Let us proceed to further examples. I have just captured an Interrupted Scolia (Colpa interrupta, LATR.), exploring the sand, doubtless in search of game. It is a matter of making the earliest possible use of her, before her spirit is chilled by the tedium of captivity. I know her prey, the larva of Anoxia australis (The Anoxia are a genus of Beetles akin to the Cockchafers.—Translator's Note.); I know, from my past excavations, the points favoured by the grub: the mounds of sand heaped up by the wind at the foot of the rosemaries on the neighbouring hill-sides. It will be a hard job to find it, for nothing is rarer than the common if one wants it then and there. I appeal for assistance to my father, an old man of ninety, still straight as a capital I. Under a sun hot enough to broil an egg, we set off, shouldering a navvy's shovel and a three-pronged luchet. (The local pitchfork of southern France.—Translator's Note.) Employing our feeble energies in turns, we dig a trench in the sand where I hope to find the Anoxia. My hopes are not disappointed. After having by the sweat of our brow—never was the expression more justified—removed and sifted two cubic yards at least of sandy soil with our fingers, we find ourselves in possession of two larvae. If I had not wanted any, I should have turned them up by the handful. But my poor and costly harvest is sufficient for the moment. To-morrow I will send more vigorous arms to continue the work of excavation.
And now let us reward ourselves for our trouble by studying the tragedy in the bell-glass. Clumsy, awkward in her movements, the Scolia slowly goes the round of the circus. At the sight of the game, her attention is aroused. The struggle is announced by the same preparations as those displayed by the Two-banded Scolia: the Wasp polishes her wings and taps the table with the tips of her antennae. And view, halloo! The attack begins. Unable to move on a flat surface, because of its short and feeble legs, deprived moreover of the Cetonia-larva's eccentric means of travelling on its back, the portly grub has no thought of fleeing; it coils itself up. The Scolia, with her powerful pincers, grips its skin now here, now elsewhere. Curved into a circle with the two ends almost touching, she strives to thrust the tip of her abdomen into the narrow opening in the coil formed by the larva. The contest is conducted calmly, without violent bouts at each varying accident. It is the determined attempt of a living split ring trying to slip one of its ends into another living split ring, which with equal determination refuses to open. The Scolia holds the victim subdued with her legs and mandibles; she tries one side, then the other, without managing to unroll the circle, which contracts still more as it feels its danger increasing. The actual circumstances make the operation more difficult: the prey slips and rolls about the table when the insect handles it too violently; there are no points of purchase and the sting cannot reach the desired spot; the fruitless efforts are continued for more than an hour, interrupted by periods of rest, during which the two adversaries represent two narrow, interlocked rings.
What ought the powerful Cetonia-grub to do to defy the Two-banded Scolia, who is far less vigorous than her victim? It should imitate the Anoxia-larva and remain rolled up like a Hedgehog until the enemy retires. It tries to escape, unrolls itself and is lost. The other does not stir from its posture of defence and resists successfully. Is this due to acquired caution? No, but to the impossibility of doing otherwise on the slippery surface of a table. Clumsy, obese, weak in the legs, curved into a hook like the common White Worm (The larva of the Cockchafer.—Translator's Note.), the Anoxia-larva is unable to move along a smooth surface; it writhes laboriously, lying on its side. It needs the shifting soil in which, using its mandibles as a plough-share, it digs into the ground and buries itself.
Let us try if sand will shorten the struggle, for I see no end to it yet, after more than an hour of waiting. I lightly powder the arena. The attack is resumed with a vengeance. The larva, feeling the sand, its native element, tries to escape. Imprudent creature! Did I not say that its obstinacy in remaining rolled up was due to no acquired prudence but to the necessity of the moment? The sad experience of past adversities has not yet taught it the precious advantage which it might derive from keeping its coils closed so long as danger remains. For that matter, on the unyielding support of my table, they are not one and all so cautious. The larger seem even to have forgotten what they knew so well in their youth: the defensive art of coiling themselves up.
I continue my story with a fine-sized specimen, less likely to slip under the Scolia's onslaught. When attacked, the larva does not curl up, does not shrink into a ring as did the last, which was younger and only half as large. It struggles awkwardly, lying on its side, half-open. For all defence it twists about; it opens, closes and reopens the great hooks of its mandibles. The Scolia grabs it at random, clasps it in her shaggy legs and for nearly a quarter of an hour battles with the luscious tit-bit. At last, after a not very tumultuous struggle, when the favourable position is attained and the propitious moment has come, the sting is implanted in the creature's thorax, in a central point, below the throat, level with the fore-legs. The effect is instantaneous: total inertia, except of the appendages of the head, the antennae and mouth-parts. I achieved the same results, the same prick at a definite, invariable point, with my several operators, renewed from time to time by some lucky cast of the net.
Let us mention, in conclusion, that the attack of the Interrupted Scolia is far less fierce than that of the Two-banded Scolia. The Wasp, a rough sand-digger, has a clumsy gait; her movements are stiff and almost automatic. She does not find it easy to repeat her dagger-thrust. Most of the specimens with which I experimented refused a second victim on the first two days after their exploits. As though somnolent, they did not stir unless excited by my teasing them with a bit of straw. Although more active and more ardent in the chase, the Two-banded Scolia likewise does not draw her weapon every time that I invite her. For all these huntresses there are moments of inaction which the presence of a fresh prey is powerless to disturb.
The Scoliae have taught me nothing further, in the absence of subjects belonging to other species. No matter: the results obtained represent no small triumph for my ideas. Before seeing the Scoliae operate, I said, guided solely by the anatomy of the victims, that the Cetonia-, Anoxia- and Oryctes-larvae must be paralysed by a single thrust of the lancet; I even named the point where the sting must strike, a central point, in the immediate vicinity of the fore-legs. Of the three genera of paralysers, two have allowed me to witness their surgical methods, which the third, I feel certain, will confirm. In both cases, a single thrust of the lancet; in both cases, injection of the venom at a predetermined point. A calculator in an observatory could not compute the position of his planet with greater accuracy. An idea may be taken as proved when it attains to this mathematical forecast of the future, this certain knowledge of the unknown. When will the acclaimers of chance achieve a like success? Order appeals to order; and chance knows no laws.