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, 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 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
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 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 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. 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 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. [37] The function exercised will have it so.
But why need the larva of the Cetonia 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 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 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 few minutes; the White Worm, [38] 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, 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 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 steel-blue spots. [39] 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.
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 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 Dipteron [40] and the Hymenopteron [41] 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.
These latter include various Orthoptera, [42] 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, 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 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.
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 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.
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 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 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. 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 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 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.