THE LANGUEDOCIAN SCORPION: THE IMMUNITY OF LARVÆ

The Life of the Scorpion by Jean-Henri Fabre, is part of the HackerNoon Books Series. You can jump to any chapter in this book here. THE LANGUEDOCIAN SCORPION: THE IMMUNITY OF LARVÆ

CHAPTER IV. THE LANGUEDOCIAN SCORPION: THE IMMUNITY OF LARVÆ

So little do we possess the Scorpion’s secret that unexpected facts crop up that strangely complicate the problem. The study of life brings us these surprises. Repeated experiments, with mutually consistent results, seem to justify our formulation of a rule when, suddenly, important exceptions arise, compelling us to follow a fresh path, directly opposed to the first, and leading us to doubt which is the last stage on the road to knowledge. After labouring long and patiently, like an ox yoked to the plow, we have to plant a note of interrogation at the end of the field which we thought that we had made ready for sowing, without any hope of a final answer. One question leads to another.

To-day the Cetonia-larvæ have forced upon me a similar change of opinion. It was at the end of November, late in the year, [84]when the adult insect was becoming scarce. At this season of dearth, for lack of anything better wherewith to continue my experiments, I thought of resorting to the grubs of the Cetonia, grubs which abound all the year through in a heap of dead leaves in a corner of the enclosure. The naturalist who questions animals is necessarily a torturer: there is no other means of making them speak. A host of questions therefore sends my curiosity rummaging, as a regular thing, in that heap of leaf-mould. Every physiological laboratory has its appointed victims: the Frog, the Guinea-pig, even the Dog. The Cetonia-larva suffices for my rustic work-shop. I add the humble grub to the noble series of victims of whose suffering our knowledge is born.

The advanced and already cold season has not slackened the Scorpion’s activity; the fat grub, on its part, in the warm moisture of the decayed leaves, has retained all the suppleness of its back. Both are in perfect condition. I bring them face to face.

The attack is not spontaneous. The larva flees obstinately, turned over on its back, skirting the wall of the cage. The [85]Scorpion remains motionless and looks on; he draws to one side and makes way when the circular track brings the creature in his direction. It is not a prey to his liking, still less a dangerous adversary; and killing merely for killing’s sake is not one of his vices. If I did not interfere, the peaceful encounter might continue indefinitely.

I worry the two of them, bring them into contact, irritate them with a bit of a straw, to such good purposes that my devices look like an attack on the part of the grub. The poor topsy-turvy creature is certainly not dreaming of fighting; it is a natural coward which, when in danger, curls up and refuses to move. Unaware of my tricks with the straw, the Scorpion ascribes to his innocent neighbour the annoyance of which I alone am the cause. He waves his sting on high and stabs. The blow has struck home, for the wound bleeds.

Relying on what the adult Cetonia showed me, I expect to see convulsions, the preludes of death. But what is this? When left to itself, the grub uncoils itself and makes off; it travels on its back neither faster nor slower than usual, as though it had not been [86]wounded. Laid on the heap of leaf-mould, it swiftly dives down, without appearing in the least injured. I go to look at it a couple of hours later. It is as vigorous as before the experiment. Its state of health is the same the next day. What are we to make of this rebel? In its adult form, it would have dropped dead; in its larval form, it is indomitable. The wound was deep, since it bleeds, but perhaps the sting omitted to inject any poison, in which case it is a harmless prick, a negligible accident for the sturdy grub. We must try again.

The same subject is stung a second time, by another Scorpion. The result agrees with the first. The wounded grub ambles along on its back entirely at its ease; it dips down into the layer of rotten leaves and quietly resumes eating. The poisoned stab has not affected it.

This immunity cannot be an exceptional instance; there are no privileged individuals among the Cetoniæ; any other subject of the same species ought to prove equally refractory. I unearth twelve larvæ and have them stung, some of them twice or thrice [87]in quick succession. All wriggle a little at the moment when the dirk enters; all lick the bleeding spot if they can reach it with their mouth and then quietly recover from their excitement. They amble along, with their legs in the air; they burrow down into the heart of the leaf-mould. I inspect them next day, the day after and the following days. The poison does not seem to have endangered them in any way.

They look so fit that I conceive a hope of rearing them. In this I succeed to perfection, without further trouble than that of renewing from time to time the provision of rotten leaves. The following year, in June, the twelve that have been subjected to the atrocious sting weave their cocoons and undergo metamorphosis. The Scorpion’s stab has caused them no worse damage than a slight itching at the moment when the sting entered the belly.

This curious result reminds me of what Lenz tells us on the subject of the Hedgehog:

“I had a mother Hedgehog,” he writes, “who was suckling her young. I threw a [88]large Viper into her box. The Hedgehog soon felt that he was there, for she is guided by the sense of smell and not of sight. She got up, went fearlessly to the Snake and sniffed at him from head to foot, especially about the mouth. The Viper hissed and bit her several times on the snout and lips. As though to make fun of her feeble assailant, she contented herself with licking her wounds, continued her inspection and was once more bitten, but this time in the tongue. At last, she seized the Viper by the head, which she crunched between her jaws, together with the poison-fangs and glands. Then she devoured half the reptile, after which she returned to lie down beside her young and give them to suck. That evening she ate another Viper and what remained of the first. Her health was not affected thereby, nor was that of the little Hedgehogs; her wounds did not even swell.

“Two days later, there was a new Viper and a new fight. The Hedgehog went up to the reptile and smelt it. Opening her jaws and erecting her poison-fangs, the Viper rushed upon her, bit her in the upper lip and remained hanging there for a time. [89]The Hedgehog shook him off and, though bitten ten times in the muzzle and twenty times elsewhere, amidst the prickles, she seized him by the head and devoured him slowly, notwithstanding his contortions. This time again neither the mother nor the sucklings seemed unwell.”

It is said that Mithridates, King of Pontus, to fortify his constitution against the dangerous potions with which his enemies attempted to destroy him, accustomed himself to different poisons. By degrees he inured his stomach against venom. Can the Hedgehog, that new Mithridates, in her quality as a Snake-eater, have acquired her immunity by gradual use and wont? Or is it not rather in her case, an original aptitude? When for the first time she bit into the reptile’s head, did she not already possess the predisposition necessary to her safety?

She did, the Cetonia-larva tells us for our answer. If any members of the insect clan has to provide itself with defensive means against the Scorpion’s attacks, it is certainly not the grub that dwells amid vegetable [90]decay. The two do not frequent the same places, which makes meetings almost impossible. On the larva’s part, therefore, there is no increasing tolerance of the poison. The first to find themselves in the Scorpion’s presence are perhaps those which I myself place there. Nevertheless, without preparations of any kind, behold the grub refractory to the sting. It possesses, from the first, powers of resistance to the poison which is quite as surprising as that of the reptile-eater.

That the Hedgehog, the appointed exterminator of Vipers, should be endowed with the prerogatives essential to her calling is strictly logical. In the same way, the Bee-eater, the handsomest bird of Mediterranean provinces, crams his crop with impunity with live Wasps; in the same way, the Cuckoo suffers from no irritation when he fills his stomach with a barbed wire entanglement of stinging hairs from the Processionary Caterpillar.1 The function exercised will have it so.

But why need the larva of the Cetonia [91]safeguard itself against the Scorpion, whom she probably never meets? We dare not believe in privileges; rather do we suspect a general aptitude. The Cetonia-larva resists the Scorpion’s sting, not as a Cetonia, but as a grub, a preparatory phase on the way to a higher organization. If so, all the larvæ, in a greater or lesser degree, according to their robustness, must possess similar powers of resistance.

What does experiment say on the subject? It behooves us to exempt from the test the weaker grubs, of a delicate constitution. To them a mere prick, without the aid of the poison, would mean a serious and often fatal wound. The point of a needle would gravely injure them. What would it be with the brutal stiletto, even though not poisoned? What we need is a few corpulent grubs which would think little of a perforated belly.

And here I have the very thing I want. An old olive-stump softened underground by decay, provides me with the larva of the Rhinoceros Beetle. It is a plump sausage, as thick as a man’s thumb. When stung by the Scorpion, the paunchy grub glides among [92]the scraps of decayed olive-wood with which I have furnished a glass jar; heedless of its mishap, it works its jaws so lustily that, eight months later, having thrived and waxed fat, it is preparing its cell for the metamorphosis. It has passed through the dreadful ordeal unscathed.

As for the adult insect, we have already seen what it does. Stung on the upper surface of the abdomen, under the lifted wing-cases, the colossus soon topples over and feebly kicks its legs about in the air. All movement ceases in three or four days at most. The powerful creature dies; its grub loses nothing in either strength or appetite.

This instance of correct prevision on my part is confirmed by a number of others. In front of my door are two old cherry-laurels, magnificently green at all times of the year. A Capricorn is ruining them for me. This is the little Cerambyx cerdo, the usual inhabitant of the hawthorn. The aroma of prussic acid, instead of repelling him, attracts him; the horned dandy is well acquainted with it, thanks to his long experience of the clusters of the hawthorn-blossoms with their searching smell. This alien [93]tree suits him so well for establishing his family that the axe will have to intervene if I want to save what remains.

I cut down the boughs that have suffered most damage. From one limb split into fragments I obtain a dozen of the Capricorn’s larvæ. My inspection of the neighbouring hedge-rows provides me with the perfect insect. And now we’ll have it out together, O destroyer of my leafy arbour! You shall make amends to me for your misdeeds; you shall die by the Scorpion.

The adults indeed succumb; but the larvæ resist. Lodged in a glass jar, with tiny morsels of the demolished tree, they quietly resume their gnawing. If the provisions do not dry up, the grubs wounded by the Scorpion complete their larval life without accident.

The Capricorn of the Oak, Cerambyx heros, behaves in a like fashion. The great horn-wearer perishes; his grub does not mind the sting a jot, for, when restored to its place in the gallery, it tunnels the wood as it did before and completes its development.

The result is the same with the Common Cockchafer. The stabbed insect dies in a [94]few minutes; the White Worm,2 on the contrary, holds out, goes underground and climbs back to the surface to gnaw the lettuce-stalk which I have given it. If my patience as an insect-rearer did not tire, the victim of the accident, from which it quickly recovers, would become a Cockchafer, as may be seen from the paunch sleek and glossy with health.

A near kinsman of the Stag-beetle, Dorcus parallelopipedus, whose larva I find in an old tamarisk-stump, adds his evidence to that of the above: the adult insect dies, the larva resists. These instances are sufficient; there is no need to continue on these lines.

Cetonia-, Oryctes-, Capricorn-, Cockchafer- and Dorcus-grubs are fat creatures, addicted to a vegetarian diet. Do these plump larvæ owe their immunity to the nature of their victuals? Or, on the other hand, can the fatty stratum, in which the reserves of these insatiable eaters accumulate, neutralize the virulence of the sting? Let us enquire of some lean flesh-eaters.

I choose the largest of our Ground-Beetles, [95]Procrusies coriaceus, a saturnine hunter whom I meet at the foot of the walls, disembowelling a Snail. A bold highwayman and built for fighting, he welds his wing-cases into an inviolable cuirass. I pare away a little of his armour behind, in order to render accessible to the Scorpion’s sting the only penetrable part, the upper surface of the abdomen.

We see a repetition of the Gold Beetle’s wretched end. The fight against the agonies of the sting would strike us with horror, if things were happening in a higher world. Thus struggles a Dog tortured by the municipal sausage seasoned with strychnine. At first the wounded Beetle scurries off desperately. Suddenly, he stops and raises himself high on his stiffened legs; he lifts his hinder part, lowers his head and supports himself on his mandibles as though about to turn a somersault. A jolt topples him over. He falls; quickly he stands up again and resumes his unnatural attitude. To look at him you would say that his joints were controlled by wires. He is like an automaton worked by a jerky spring. Another shake, another fall, another recovery: and this goes [96]on for twenty minutes or so. At last the demented Beetle collapses on his back and does not get up again, though his limbs continue to move. Next morning he is absolutely motionless.

And what of the larva? Well, though destitute of the layer of fat which would seem to protect the grubs of the Cetonia, the Oryctes and the others, the meagre grub of the Procrustes is so little harmed by the Scorpion’s sting that, a fortnight after the ordeal, it buries itself in the ground and digs itself a cell in which the transformation is effected. Lastly, not long after, the adult emerges from the soil in perfect health. Therefore neither the diet nor the degree of stoutness is responsible for this immunity.

Nor is the place occupied in the entomological series, as the Moths will tell us, now that the Beetles have spoken. The first to be questioned is the Zeuzera, whose caterpillar has a calamitous effect upon various trees and shrubs. I take a mother at the moment when she is slipping her long ovipositor into the crevices in the bark of a lilac-tree, to lay her eggs. She is magnificent in her white costume adorned with [97]steel-blue spots.3 I place her at the Scorpion’s mercy. The business is not protracted. No sooner is the Zeuzera stung than she dies, with no disordered motions. Death is gentle to her.

And the caterpillar? After the prick, the caterpillar is as well as before. Restored to the gallery whence I extracted it by splitting its lilac-branch, it works away busily as usual: I can see this by the sawdust ejected through the orifice of the cell. The chrysalis and the Moth come in the summer, according to rule.

The Silkworm, which I am able to procure in such numbers as I require from the nurseries at the farms hard by, lends itself much better to experiment. At the end of May, when the rearing is nearly finished, I cause a couple of dozen to be stung. The worms have a fine, chubby skin, into which the sting each time enters easily, producing a copious hemorrhage. The little table on which my curiosity drives me to perpetrate these barbarities is soon covered with splashes of blood like drops of liquid amber.[98]

When restored to their litter of mulberry-leaves, the wounded almost at once set to browsing with their usual appetite. Ten days later, all, from the first to the last, weave their cocoons, which are perfectly normal in shape and thickness. Lastly, from these cocoons, without any losses, emerge Moths whom we shall presently question in another connection. For the moment it is proved that the Silkworm resists the Scorpion’s sting. As for the Moth herself, we know what becomes of her. She succumbs slowly, it it true, after the manner of the Great Peacock; but at all events she succumbs: the sting is always fatal.

The Spurge Hawk-moth gives the same answer: the Moth dies quickly: the caterpillar defies the sting, eats its fill and then goes underground itself into a chrysalis under a coarse veil of sand and silk. Nevertheless, among the number operated upon, there are some which are stabbed to death, perhaps because of the multiplicity of their wounds. The skin offers a certain resistance to perforation and the discharge of blood remains uncertain, leaving me undecided as to the efficiency of the stab. I was [99]obliged to prolong the struggle until the evidence was complete and it is probable that I sometimes went too far. The caterpillar which, if pricked but once, would have withstood the ordeal as sturdily as the Silkworm perishes from an overdose.

The mighty, turquoise-bedecked caterpillar of the Great Peacock supplies me with very definite results. When pricked till the blood comes and then replaced on its grazing-ground, the branch of almond, it completes its development and accurately spins its ingenious cocoon.

The Dipteron4 and the Hymenopteron5 should be worth examination. Like the Moth and the Beetle, they undergo a general remoulding through the action of the metamorphosis; but they are small-sized and for the most part could not be easily manipulated were my tweezers to present them to the sting. Their delicate larvæ would die merely of the perforation of the skin. Let us question only the giants.[100]

These latter include various Orthoptera,6 the Tryxalis, the Grey Locust, the White-faced Decticus, the Mole-cricket, the Mantis. As we have already seen, all these succumb when struck by the Scorpion’s sting. Now, in their group, the complete development essential to the festival of the pairing is preceded by a transition-form which, without being actually larval, and presenting no likeness whatever to the adult, constitutes an inferior stage, a step towards the marriageable.

The Grey Locust, as we see him on the vine at vintage-time, does not yet possess his magnificent network wings, nor his leathery wing-cases; he possesses only their rudiments, reduced to skimpy coat-tails. The Mole-cricket, who ends by displaying an ample set of wings, which fold back into a sharp tail and enclose the tip of the abdomen, has at first only ungainly stumps, fastened to the upper part of the back.

We behold the same sign of juvenile inferiority in the young Tryxalis, the young Decticus and the others. These mighty, [101]aerial sailing-craft of the future have their canvas enclosed in the germ, in mean-looking sheaths. As for the rest, the insect is, from the beginning, very nearly what it will be in all the fullness of its finery. Age develops and does not transform the Orthopteron.

Now are these incomplete insects, with wing-stumps in the place of wings, are these young insects capable of withstanding the Scorpion’s sting as do the true larvæ, the babes of the Oryctes and the Capricorn, the caterpillar of the Hawk-moth and the Bombyx? If the generous sap of youth is an adequate preservative, we ought to find immunity here. We find nothing of the sort. With wings or without, old or young, the Mole-cricket perishes. The Mantis, the Locust, the Tryxalis, whether adult or incomplete, perish likewise.

In the matter of resistance to the Scorpion’s poison we are therefore led to class insects in two categories: on the one hand, those which undergo a real transformation, accompanied by an alteration of the whole organism; on the other hand, those which undergo only secondary modifications. In [102]the first division, the larva resists and the adult dies; in the second, death invariably ensues.

What reason can we discover for this difference? Experiment shows us first that resistance to the sting increases as the nature of the victim becomes less highly organized. The Lycosa, the Epeira, the Mantis, all exceedingly sensitive to impressions, succumb on the instant, as though struck by lightning; the Gold Beetle and the Procrustes, those strenuous livers, are seized forthwith with convulsions similar to those produced by strychnine; the Sacred Beetle, a spirited pill-roller, prances in a sort of St. Vitus’ dance. On the other hand, the sluggish Oryctes, the lazy Cetonia, both lovers of protracted slumbers in the heart of the roses, bear their misfortunes patiently and fidget feebly for whole days on end before giving up the ghost. Beneath them is the Acridian, the Locust, the essential rustic. Lower still comes the Centipede, an inferior being, roughly organized. It is evident therefore that the venom acts more quickly or more slowly according to the patient’s nervous constitution.[103]

Let us consider separately the insects of a superior order, subject to complete transformations. The word metamorphosis applied to them means a change of form. Now is it only the shape that changes when the caterpillar turns into a Moth, or when the grub in the leaf-mould becomes a Cetonia? More than this occurs and much more, as the Scorpion’s sting informs us.

A profound and comprehensive renewal is effected in the vital statics of the metamorphosed insect; the substance, which is actually still the same, enters into fusion, subtilizes its atomic structure and becomes liable to sensory vibrations which are the first appanage of the nubile specimen. The armour of the wing-cases, the blades, tufts and quivering stems of the antennæ, the legs fit for running and wings fit for flying: all these are magnificent and yet all these are nothing.

Something else towers high above them. The transformed insect has acquired a new life, more active and richer in sensations. A second birth has taken place in which all is renewed, in the invisible and intangible even more than in the material domain. It is more than a molecular rearrangement; it [104]is the development of aptitudes unknown in the past. The larva, generally a mere scrap of intestine, lived a placid and very monotonous existence and lo, in view of the future instincts, metamorphosis revolutionizes its substance, distils its humours and refines the centres of energy atom by atom. An enormous leap is made towards progress, but the new state has not the sturdy equilibrium of the first, perfection has been gained at the cost of stability; and so the insect dies of an ordeal which the grub would support with impunity.

With the Acridians and the Orthoptera in general, conditions are quite different. Here there is no real metamorphosis, utterly changing the structure, the mode of life and the habits. The insect remains, all its life long, very much what it was on leaving the egg. It is born in a shape which the future will hardly modify, with habits which will not be altered by time. It undergoes no renovation, no sudden growth. In its infancy already it possesses the temperament of the adult; and as such it is deprived of the immunity enjoyed by rudimentary organisms.[105]

Exempted from a probationary period in the grub state, the short-coated Locust suffers from the drawbacks of a too rapid development. He perishes as quickly as the adult, whom he resembles in all but a few details.

I will not deny that the explanation which I have given may not be the right one; and I will not insist upon it. A cast of the net into the depths of the unknown does not always bring up to the surface the correct idea, a very rare catch. A far-reaching fact is acquired nevertheless, even though it remain unexplained. Metamorphosis modifies the organic substance to the degree of changing its innermost properties. The Scorpion’s poison, a reagent of transcendental chemistry, distinguishes the flesh of the larva from that of the adult; it is kindly to the first and deadly to the second.

This curious result raises a question which is not alien to the vainglorious theories affecting attenuated viruses, serums and vaccines. A larva subject to complete metamorphosis is stung by the Scorpion; we might readily say that it has been vaccinated, in the sense that it has been inoculated with [106]a virus fatal under the future conditions, but tolerable in its effects in the present stage. The patient does not seem affected by the sting; it begins to eat again and continues its larval work as usual.

The virus, however, cannot fail to act, in one way or another, on the animal’s blood or nerves. Might it not lessen the vulnerability which results from the transformation? Can the adult be rendered immune by a habit acquired during the larval stage? Might it be able to resist the virus as Mithridates was able to resist poison? In short, is the insect with a complete metamorphosis whose larva has been stung capable of itself withstanding the sting? That is the question.

The confirmatory arguments are so urgent that we are at first tempted to answer:

“Yes, the adult will resist.”

But we will leave experiment to speak for itself. With this object preparations are made with four sets of subjects. The first consists of twelve Cetonia-larvæ, which, after being stung in October, have been revaccinated, that is to say, stung a second time, in May. The second set is also composed [107]of twelve Cetonia-larvæ, but these have been stung once only, in May. Four chrysalids of the Spurge Hawk-moth form the third. They belong to caterpillars stung once, in June. Lastly, I have some cocoons spun by the Silkworm whose vaccination, attended by a flow of blood, I have described above. The Scorpion will once more play his part with each lot after the hatching has taken place.

The Silkworm Moth is the first to respond to my impatience. The Moth is there in two or three weeks’ time, bustling about in readiness for the pairing. The stab received as a caterpillar has not cooled his ardour in the very least. I subject him to the test. The attack is laboured and the blow is not clearly struck. No matter: all those attacked perish after a death-struggle lasting a day or two. The previous vaccination has made no difference to the result: they succumbed before and they succumb after.

But these are feeble witnesses, on whom it is not wise to rely. I shall achieve more, I feel convinced, with the Hawk-moths and especially with those sturdy subjects the Cetoniæ. [108]Well, the Hawk-moths whose caterpillars have received the virus which theoretically should render them immune retain their normal vulnerability: when attacked by the sting, they succumb instantly, exactly like the others, who did not at the larval age undergo a preventative inoculation.

Perhaps the number of days elapsing between the stinging of the caterpillar and of the moth was not sufficient to enable the virus to act upon the organism to the requisite degree. It might need a longer space of time to bring about the inward modifications caused by the action of the poison on the insect’s organism. The Cetonia-larvæ will perhaps be able to dispense with this period.

I have a set of twelve of them, stung twice over, first in October and then in May. The perfect insect bursts its cocoon at the end of July. Ten months therefore have elapsed since the first sting and three months since the second. Is the adult now immune?

Not at all. When subjected to the Scorpion, my twelve vaccinated specimens all perish, no more and no less quickly than their fellows who were born quietly in their heap of rotten leaves. Twelve others, pricked [109]only once, in May, succumb with the same promptness. In the case of both sets, my devices, which inspired me with confidence at first, miscarry pitifully, to my extreme confusion.

I try another method, that of transfusion of blood, which is related to serotherapy. Since it resists the Scorpion’s sting, the larva of the Cetonia must have blood endowed with special qualities, apt to neutralize the virulence of the poison. If transferred from the larva to the adult, might not this blood communicate its qualities and render the perfect insect invulnerable?

I give a Cetonia-grub a superficial wound with the point of a needle. The blood spouts forth abundantly. I collect it in a watch-glass. A glass tube of small diameter, drawn out to a sharp point, serves as an injector. I charge it by suction with the fluid collected, varying the dose from a cubic millimetre to ten and twenty times as much. By blowing into the tube I transfer the liquid into some point of the adult Cetonia, particularly on the ventral surface, where a needle has prepared the way for the fragile injector. The insect stands the operation [110]very well. The richer by a little larval blood and not seriously wounded, it presents every appearance of blooming health.

Now what comes of this treatment? Nothing at all. I wait a day or two to give the injected fluids time to diffuse and act. The Cetonia is then presented to the Scorpion. Veil your face, O foolish physiologist: the creature perishes as it would have done before your presumptuous attempts at surgery. We cannot manipulate animals as we can the reagents of chemistry.

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