I have discussed elsewhere the stings administered by the Wasps to their prey. Now chemistry comes and puts a spoke in the wheel of our arguments, telling us that the poison of the Bees is not the same as that of the Wasps. The Bees' is complex and formed of two elements, acid and alkaline. The Wasps' possess only the acid element; and it is to this very acidity and not to the 'so-called' skill of the operators that the preservation of the provisions is due (1).
Admitting that there is a difference in the nature of the venom, I fail to see that this has any bearing on the problem in hand. I can inoculate with various liquids acids, weak nitric acid, alkalis, ammonia, neutral bodies, spirits of wine, essence of turpentine and obtain conditions similar to those of the victims of the predatory insects, that is to say, inertia with the persistence of a dull vitality betrayed by the movements of the mouth-parts and antennae. I am not, of course, invariably successful, for there is neither delicacy nor precision in my poisoned needle and the wound which it makes does not bear comparison with the tiny puncture of the unerring natural sting; but, after all, it is repeated often enough to put the object of my experiment beyond doubt. I should add that, to achieve success, we must have a subject with a concentrated ganglionic column, such as the Weevil, the Buprestis, the Dung-beetle and others. Paralysis is then obtained with but a single prick, made at the point which the Cerceris has revealed to us, the point at which the corselet joins the rest of the thorax. In that case, the least possible quantity of the acrid liquid is instilled, a quantity too small to endanger the patient's life. With scattered nervous centres, each requiring a separate operation, this method is impracticable: the victim would die of the excess of corrosive fluid. I am quite ashamed to have to recall these old experiments. Had they been resumed and carried on by others of greater authority than I, we should have escaped the objections of chemistry.
When light is so easy to obtain, why go in search of scientific obscurity? Why talk of acid or alkaline reactions, which prove nothing, when it is so simple to have recourse to facts, which prove everything? Before declaring that the hunting insects' poison has preservative properties merely because of its acid qualities, it would have been well to enquire if the sting of a Bee, with its acid and its alkali, could not perchance produce the same effects as that of the paralyser, whose skill is categorically denied. The chemists never gave this a thought. Simplicity is not always welcome in our laboratories. It is my duty to repair that little omission. I propose to enquire if the poison of the Bee, the chief of the Apidae, is suitable for a surgery that paralyses without killing.
The enquiry bristles with difficulties, though this is no reason for abandoning it. First and foremost, I cannot possibly operate with the Bee just as I catch her. Time after time I make the attempt, without once succeeding; and patience becomes exhausted. The sting has to penetrate at a definite point, exactly where the Wasp's sting would have entered. My intractable captive tosses about angrily and stings at random, never where I wish. My fingers get hurt even oftener than the patient. I have only one means of gaining a little control over the indomitable dart; and that is to cut off the Bee's abdomen with my scissors, to seize the stump instantly with a fine forceps and to apply the tip at the spot where the sting is to enter.
Everybody knows that the Bee's abdomen needs no orders from the head to go on drawing its weapon for a few instants longer and to avenge the deceased before being itself overcome with death's inertia. This vindictive persistency serves me to perfection. There is another circumstance in my favour: the barbed sting remains where it is, which enables me to ascertain the exact spot pierced. A needle withdrawn as soon as inserted would leave me doubtful. I can also, when the transparency of the tissues permits, perceive the direction of the weapon, whether perpendicular and favourable to my plans, or slanting and therefore valueless. Those are the advantages.
The disadvantages are these: the amputated abdomen, though more tractable than the entire Bee, is still far from satisfying my wishes. It gives capricious starts and unexpected pricks. I want it to sting here. No, it balks my forceps and goes and stings elsewhere: not very far away, I admit; but it takes so little to miss the nerve-centre which we wish to get at. I want it to go in perpendicularly. No, in the great majority of cases it enters obliquely and passes only through the epidermis. This is enough to show how many failures are needed to make one success.
Nor is this all. I shall be telling nobody anything new when I recall the fact that the Bee's sting is very painful. That of the hunting insects, on the contrary, is in most cases insignificant. My skin, which is no less sensitive than another's, pays no attention to it: I handle Sphex, Ammophilae and Scoliae without heeding their lancet-pricks. I have said this before; I remind the reader of it because of the matter in hand. In the absence of well-known chemical or other properties, we have really but one means of comparing the two respective poisons; and that is the amount of pain produced. All the rest is mystery. Besides, no poison, not even that of the Rattlesnake, has hitherto revealed the cause of its dread effects.
Acting, therefore, under the instruction of that one guide, pain, I place the Bee's sting far above that of the predatory insects as an offensive weapon. A single one of its thrusts must equal and often surpass in efficaciousness the repeated wounds of the other. For all these reasons an excessive display of energy; the variable quantity of the virus inoculated by a wriggling abdomen which no longer measures the emission by doses; a sting which I cannot direct as I please; a wound which may be deep or superficial, the weapon entering perpendicularly or obliquely, touching the nerve-centres or affecting only the surrounding tissues my experiments ought to produce the most varied results.
I obtain, in fact, every possible kind of disorder: ataxy, temporary disablement, permanent disablement, complete paralysis, partial paralysis. Some of my stricken victims recover; others die after a brief interval. It would be an unnecessary waste of space to record in this volume my hundred and one attempts. The details would form tedious reading and be of very little advantage, as in this sort of study it is impossible to marshal one's facts with any regularity. I will, therefore, sum them up in a few examples.
A colossal member of the Grasshopper tribe, the most powerful in my district, Decticus verrucivorus (2), is pricked at the base of the neck, on the line of the fore-legs, at the median point. The prick goes straight down. The spot is the same as that pierced by the sting of the slayer of Crickets and Ephippigers (3). The giantess, as soon as stung, kicks furiously, flounders about, falls on her side and is unable to get up again. The fore-legs are paralysed; the others are capable of moving. Lying sideways, if not interfered with, the insect in a few moments gives no signs of life beyond a fluttering of the antennae and palpi, a pulsation of the abdomen and a convulsive uplifting of the ovipositor; but, if irritated with a slight touch, it stirs its four hind-legs, especially the third pair, those with the big thighs, which kick vigorously. Next day, the condition is much the same, with an aggravation of the paralysis, which has now attacked the middle-legs. On the day after that, the legs do not move, but the antennae, the palpi and the ovipositor continue to flutter actively. This is the condition of the Ephippiger stabbed three times in the thorax by the Languedocian Sphex. One point alone is missing, a most important point: the long persistence of a remnant of life. In fact, on the fourth day, the Decticus is dead; her dark colour tells me so.
There are two conclusions to be drawn from this experiment and it is well to emphasise them. First, the Bee's poison is so active that a single dagger-thrust aimed at a nervous centre kills in four days one of the largest of the Orthoptera (4), though an insect of powerful constitution. Secondly, the paralysis at first affects only the legs whose ganglion is attacked; next, it spreads slowly to the second pair; lastly, it reaches the third. The local effect is diffused. This diffusion, which might well take place in the victims of the predatory insects, plays no part in the latters' method of operation. The egg, which will be laid immediately afterwards, demands the complete inertia of the prey from the outset. Hence all the nerve-centres that govern locomotion must be numbed instantaneously by the virus.
I can now understand why the poison of the predatory Wasps is comparatively painless in its effects. If it possessed the strength of that of the Bee, a single stab would impair the vitality of the prey, while leaving it for some days capable of violent movements that would be very dangerous to the huntress and especially to the egg. More moderate in its action, it is instilled at the different nervous centres, as is the case more particularly with the caterpillars (5). In this way, the requisite immobility is obtained at once; and, notwithstanding the number of wounds, the victim is not a speedy corpse. To the marvels of the paralysers' talent we must add one more: their wonderful poison, the strength of which is regulated by delicate doses. The Bee revenging herself intensifies the virulence of her poison; the Sphex putting her grubs' provender to sleep weakens it, reduces it to what is strictly necessary.
One more instance of nearly the same kind. I prefer to take my subjects from among the Orthoptera, which, owing to their imposing size and the thinness of their skin at the points to be attacked, lend themselves better than other insects to my delicate manipulations. The armour of a Buprestis, the fat blubber of a Rosechafer-grub, the contortions of a caterpillar present almost insuperable obstacles to the success of a sting which it is not in my power to direct. The insect which I now offer to the Bee's lancet is the Great Green Grasshopper (Locusta viridissima), the adult female. The prick is given in the median line of the fore-legs.
The effect is overwhelming. For two or three seconds the insect writhes in convulsions and then falls on its side, motionless throughout, save in the ovipositor and the antennae. Nothing stirs so long as the creature is left alone; but, if I tickle it with a hair-pencil, the four hind-legs move sharply and grip the point. As for the fore-legs, smitten in their nerve-centre, they are quite lifeless. The same condition is maintained for three days longer. On the fifth day, the creeping paralysis leaves nothing free but the antennae waving to and fro and the abdomen throbbing and lifting up the ovipositor. On the sixth, the Grasshopper begins to turn brown; she is dead. Except that the vestige of life is more persistent, the case is the same as that of the Decticus. If we can prolong the duration, we shall have the victim of the Sphex.
But first let us look into the effect of a prick administered elsewhere than opposite the thoracic ganglia. I cause a female Ephippiger to be stung in the abdomen, about the middle of the lower surface. The patient does not seem to trouble greatly about her wound: she clambers gallantly up the sides of the bell-jar under which I have placed her; she goes on hopping as before. Better still, she sets about browsing the vine-leaf which I have given her for her consolation. A few hours pass and the whole thing is forgotten. She has made a rapid and complete recovery.
A second is wounded in three places on the abdomen: in the middle and on either side. On the first day, the insect seems to have felt nothing; I see no sign of stiffness in its movements. No doubt it is suffering acutely; but these stoics keep their troubles to themselves. Next day, the Ephippiger drags her legs a little and walks somewhat slowly. Two days more; and, when laid on her back, she is unable to turn over. On the fifth day, she succumbs. This time, I have exceeded the dose; the shock of receiving three stabs was too much for her.
And so with the others, down to the sensitive Cricket, who, pricked once in the abdomen, recovers in one day from the painful experience and goes back to her lettuce-leaf. But, if the wound is repeated a few times, death ensues within a more or less short period. I make an exception, among those who pay tribute to my cruel curiosity, of the Rosechafer-grubs, who defy three and four needle-thrusts. They will collapse suddenly and lie outstretched, flabby and lifeless; and, just when I am thinking them dead or paralysed, the hardy creatures will recover consciousness, move along on their backs (6), bury themselves in the mould. I can obtain no precise information from them. True, their thinly scattered cilia and their breastplate of fat form a palisade and a rampart against the sting, which nearly always enters only a little way and that obliquely.
Let us leave these unmanageable ones and keep to the Orthoperon, which is more amenable to experiment. A dagger-thrust, we were saying, kills it if directed upon the ganglia of the thorax; it throws it into a transient state of discomfort if directed upon another point. It is, therefore, by its direct action upon the nervous centres that the poison reveals its formidable properties.
To generalize and say that death is always near at hand when the sting is administered in the thoracic ganglia would be going too far: it occurs frequently, but there are a good many exceptions, resulting from circumstances impossible to define. I cannot control the direction of the sting, the depth attained, the quantity of poison shed; and the stump of the Bee is very far from making up for my shortcomings. We have here not the cunning sword-play of the predatory insect, but a casual blow, ill-placed and ill-regulated. Any accident is possible, therefore, from the gravest to the mildest. Let us mention some of the more interesting.
An adult Praying Mantis (7) is pricked level with the attachment of the predatory legs. Had the wound been in the centre, I should have witnessed an occurrence which, although I have seen it many times, still arouses my liveliest emotion and surprise. This is the sudden paralysis of the warrior's savage harpoons. No machinery stops more abruptly when the mainspring breaks. As a rule, the inertia of the predatory legs attacks the others in the course of a day or two; and the palsied one dies in less than a week. But the present sting is not in the exact centre. The dart has entered near the base of the right leg, at less than a millimetre (8) from the median point. That leg is paralysed at once; the other is not; and the insect employs it to the detriment of my unsuspecting fingers, which are pricked to bleeding-point by the spike at the tip. Not until tomorrow is the leg which wounded me to-day rendered motionless. This time, the paralysis goes no farther. The Mantis moves along quite well, with her corselet proudly raised, in her usual attitude; but the predatory fore-arms, instead of being folded against the chest, ready for attack, hang lifeless and open. I keep the cripple for twelve days longer, during which she refuses all nourishment, being incapable of using her tongs to seize the prey and lift it to her mouth. The prolonged abstinence kills her.
Some suffer from locomotor ataxy. My notes recall an Ephippiger who, pricked in the prothorax away from the median line, retained the use of her six limbs without being able to walk or climb for lack of co-ordination in her movements. A singular awkwardness left her wavering between going back and going forward, between turning to the right and turning to the left.
Some are smitten with semiparalysis. A Cetonia-grub, pricked away from the centre on a level with the fore-legs, has her right side flaccid, spread out, incapable of contracting, while the left side swells, wrinkles and contracts. Since the left half no longer receives the symmetrical cooperation of the right half, the grub, instead of curling into the normal volute, closes its spiral on one side and leaves it wide open on the other. The concentration of the nervous apparatus, poisoned by the venom down one side of the body only, a longitudinal half, explains this condition, which is the most remarkable of all.
There is nothing to be gained by multiplying these examples. We have seen pretty clearly the great variety of results produced by the haphazard sting of a Bee's abdomen; let us now come to the crux of the matter. Can the Bee's poison reduce the prey to the condition required by the predatory Wasp? Yes, I have proved it by experiment; but the proof calls for so much patience that it seemed to me to suffice when obtained once for each species. In such difficult conditions, with a poison of excessive strength, a single success is conclusive proof; the thing is possible so long as it occurs once.
A female Ephippiger is stung at the median point, just a little in front of the fore-legs. Convulsive movements lasting for a few seconds are followed by a fall to one side, with pulsations of the abdomen, flutterings of the antennae and a few feeble movements of the legs. The tarsi cling firmly to the hair-pencil which I hold out to them. I place the insect on its back. It lies motionless. Its state is absolutely the same as that to which the Languedocian Sphex (9) reduces her Ephippigers. For three weeks on end, I see repeated in all its details the spectacle to which I have been accustomed in the victims extracted from the burrows or taken from the huntress: the wide-open mandibles, the quivering palpi and tarsi, the ovipositor shuddering convulsively, the abdomen throbbing at long intervals, the spark of life rekindled at the touch of a pencil. In the fourth week, these signs of life, which have gradually weakened, disappear, but the insect still remains irreproachably fresh. At last a month passes; and the paralysed creature begins to turn brown. It is over; death has come.
I have the same success with a Cricket and also with a Praying Mantis. In all three cases, from the point of view of long-maintained freshness and of the signs of life proved by slight movements, the resemblance between my victim and those of the predatory insects is so great that no Sphex and no Tachytes would have disowned the product of my devices. My Cricket, my Ephippiger, my Mantis had the same freshness as theirs; they preserved it as theirs did for a period amply sufficient to allow of the grubs' complete evolution. They proved to me, in the most conclusive manner, they prove to all whom it may interest, that the poison of the Bees, leaving its hideous violence on one side, does not differ in its effects from the poison of the predatory Wasps. Are they alkaline or acid? The question is an idle one in this connection. Both of them intoxicate, derange, torpify the nervous centres and thus produce either death or paralysis, according to the method of inoculation. For the moment, that is all. No one is yet able to say the last word on the actions of those poisons, so terrible in infinitesimal doses. But on the point under discussion we need no longer be ignorant: the Wasp owes the preservation of her grub's provisions not to any special qualities of her poison but to the extreme precision of her surgery.
A last and more plausible objection is that raised by Darwin when he said that there were no fossil remains of instincts. And, if there were, O master, what would they teach us? Not very much more than what we learn from the instincts of to-day. Does not the geologist make the erstwhile carcases live anew in our minds in the light of the world as we see it? With nothing but analogy to guide them, he describes how some saurian lived in the jurassic age; there are no fossil remains of habits, but nevertheless he can tell us plenty about them, things worthy of credence, because the present teaches him the past. Let us do a little as he does.
I will suppose a precursor of the Calicurgi (The Calicurgus, or Pompilus, is a Hunting Wasp, feeding her larvae on Spiders. Cf. "The Life and Love of the Insect": chapter 12.(10) dwelling in the prehistoric coal-forests. Her prey was some hideous Scorpion, that first-born of the Arachnida. How did the Hymenopteron master the terrible prey? Analogy tells us, by the methods of the present slayer of Tarantulae. It disarmed the adversary; it paralysed the venomous sting by a stroke administered at a point which we could determine for certain by the animal's anatomy. Unless this was the way it happened, the assailant must have perished, first stabbed and then devoured by the prey. There is no getting away from it: either the precursor of the Calicurgi, that slaughterer of Scorpions, knew her trade thoroughly, or else the continuation of her race became impossible, even as it would be impossible to keep up the race of the Tarantula-killer without the dagger-thrust that paralyses the Spider's poison-fangs. The first who, greatly daring, pinked the Scorpion of the coal-seams was already an expert fencer; the first to come to grips with the Tarantula had an unerring knowledge of her dangerous surgery. The least hesitation, the slightest speculation; and they were lost. The first teacher would also have been the last, with no disciples to take up her work and perfect it.
But fossil instincts, they insist, would show us intermediary stages, first, second and third rungs; they would show us the gradual passing from the casual and very incorrect attempt to the perfect practice, the fruit of the ages; with their accidental differences, they would give us terms of comparison wherewith to trace matters from the simple to the complex. Never mind about that, my masters: if you want varied instincts in which to seek the source of the complex by means of the simple, it is not necessary to search the foliations of the coal-seams and the successive layers of the rocks, those archives of the prehistoric world; the present day affords to contemplation an inexhaustible treasury realizing perhaps everything that can emerge from the limbo of possibility. In what will soon be half a century of study, I have caught but a tiny glimpse of a very tiny corner of the realm of instinct; and the harvest gathered overwhelms me with its variety: I do not yet know two species of predatory Wasps whose methods are exactly the same.
One gives a single stroke of the dagger, a second two, a third three, a fourth nine or ten. One stabs here and the other there; and neither is imitated by the next, who attacks elsewhere. This one injures the cephalic centres and produces death; that one respects them and produces paralysis. Some squeeze the cervical ganglia to obtain a temporary torpor; others know nothing of the effects of compressing the brain. A few make the prey disgorge, lest its honey should poison the offspring; the majority do not resort to preventive manipulations. Here are some that first disarm the foe, who carries poisoned daggers; yonder are others and more numerous, who have no precautions to take before murdering the unarmed prey. In the preliminary struggle, I know some who grab their victims by the neck, by the rostrum, by the antennae, by the caudal threads; I know some who throw them on their backs, some who lift them breast to breast, some who operate on them in the vertical position, some who attack them lengthwise and crosswise, some who climb on their backs or on their abdomens, some who press on their backs to force out a pectoral fissure, some who open their desperately contracted coil, using the tip of the abdomen as a wedge. And so I could go on indefinitely: every method of fencing is employed. What could I not also say about the egg, slung pendulum-fashion by a thread from the ceiling, when the live provisions are wriggling underneath; laid on a scanty mouthful, a solitary opening dish, when the dead prey requires renewing from day to-day; entrusted to the last joint stored away, when the victuals are paralysed; fixed at a precise spot, entailing the least danger to the consumer and the game, when the corpulent prey has to be devoured with a special art that warrants its freshness!
Well, how can this multitude of varied instincts teach us anything about gradual transformation? Will the one and only dagger-thrust of the Cerceris and the Scolia take us to the two thrusts of the Calicurgus, to the three thrusts of the Sphex, to the manifold thrust of the Ammophila? Yes, if we consider only numerical progression. One and one are two; two and one are three: so run the figures. But is this what we want to know? What has arithmetic to do with the case? Is not the whole problem subordinate to a condition that cannot be translated into cyphers? As the prey changes, the anatomy changes; and the surgeon always operates with a complete understanding of his subject. The single dagger-thrust is administered to ganglia collected into a common cluster; the manifold thrusts are distributed over the scattered ganglia; of the two thrusts of the Tarantula-huntress, one disarms and the other paralyses. And so with the others: that is to say, the instinct is directed each time by the secrets of the nervous organism. There is a perfect harmony between the operation and the patient's anatomy.
The single stroke of the Scolia is no less wonderful than the repeated strokes of the Ammophila. Each has her appointed game and each slays it by a method as rational as any that our own science could invent. In the presence of this consummate knowledge, which leaves us utterly confounded, what a poor argument is that of 1 + 1 = 2! And what is that progress by units to us? The universe is mirrored in a drop of water; universal logic flashes into sight in a single sting.
Besides, push on the pitiful argument. One leads to two, two lead to three. Granted without dispute. And then? We will accept the Scolia as the pioneer, the foundress of the first principles of the art. The simplicity of her method justifies our supposition. She learns her trade in some way or other, by accident; she knows supremely well how to paralyse her Cetonia-grub with a single dagger-thrust driven into the thorax. One day, through some fortuitous circumstance, or rather by mistake, she takes it into her head to strike two blows. As one is enough for the Cetonia, the repetition was of no value unless there was a change of prey. What was the new victim submitted to the butcher's knife? Apparently, a large Spider, since the Tarantula and the Garden Spider call for two thrusts. And the prentice Scolia, who used at first to sting under the throat, had the skill, at her first attempt, to begin by disarming her adversary and then to go quite low down, almost to the end of the thorax, to strike the vital point. I am utterly incredulous as to her success. I see her eaten up if her lancet swerves and hits the wrong spot. Let us look impossibility boldly in the face and admit that she succeeds. I then see the offspring, which have no recollection of the fortunate event save through the belly and then we are postulating that the digestion of the carnivorous larva leaves a trace in the memory of the honey-sipping insect I see the offspring, I say, obliged to wait at long intervals for that inspired double thrust and obliged to succeed each time under pain of death for them and their descendants. To accept this host of impossibilities exceeds all my faculties of belief. One leads to two, no doubt; the Ssingle blow of the predatory Wasp will never lead to the blow twice delivered.
In order to live, we all require the conditions that enable us to live: this is a truth worthy of the famous axioms of La Palice. (11).
The predatory insects live by their talent. If they do not possess it to perfection, their race is lost. Hidden in the murk of the past ages, the argument based upon the non-existence of fossil instinct is no better able than the others to withstand the light of living realities; it crumbles under the stroke of fate; it vanishes before a La Palice platitude.