THE IGNORANCE OF INSTINCT

The Sphex has shown us how infallibly and with what transcendental art she acts when guided by the unconscious inspiration of her instinct; she is now going to show us how poor she is in resource, how limited in intelligence, how illogical even, in circumstances outside of her regular routine. By a strange inconsistency, characteristic of the instinctive faculties, profound wisdom is accompanied by an ignorance no less profound. To instinct nothing is impossible, however great the difficulty may be. In building her hexagonal cells, with their floors consisting of three lozenges, the Bee solves with absolute precision the arduous problem of how to achieve the maximum result at a minimum cost, a problem whose solution by man would demand a powerful mathematical mind. The Wasps whose larvæ live on prey display in their murderous art methods hardly rivalled by those of a man versed in the intricacies of anatomy and physiology. Nothing is difficult to instinct, so long as the act is not outside the unvarying cycle of animal existence; on the other hand, nothing is easy to instinct, if the act is at all removed from the course usually pursued. The insect which astounds us, which terrifies us with its extraordinary intelligence, surprises us, the next moment, with its stupidity, when confronted with some simple fact that happens to lie outside its ordinary practice. The Sphex will supply us with a few instances.

Let us follow her dragging her Ephippiger home. If fortune smile upon us, we may witness some such little scene as that which I will now describe. When entering her shelter under the rock, where she has made her burrow, the Sphex finds, perched on a blade of grass, a Praying Mantis, a carnivorous insect which hides cannibal habits under a pious appearance. The danger threatened by this robber ambushed on her path must be known to the Sphex, for she lets go her game and pluckily rushes upon the Mantis, to inflict some heavy blows and dislodge her, or at all events to frighten her and inspire her with respect. The robber does not move, but closes her lethal machinery, the two terrible saws of the arm and fore-arm. The Sphex goes back to her capture, harnesses herself to the antennæ and boldly passes under the blade of grass whereon the other sits perched. By the direction of her head we can see that she is on her guard and that she holds the enemy rooted, motionless, under the menace of her eyes. Her courage meets with the reward which it deserves: the prey is stored away without further mishap.

A word more on the Praying Mantis, or, as they say in Provence, lou Prégo Diéou, the Pray-to-God. Her long, pale-green wings, like spreading veils, her head raised heavenwards, her folded arms, crossed upon her breast, are in fact a sort of travesty of a nun in ecstasy. And yet she is a ferocious creature, loving carnage. Though not her favourite spots, the work-yards of the various Digger-wasps receive her visits pretty frequently. Posted near the burrows, on some bramble or other, she waits for chance to bring within her reach some of the arrivals, forming a double capture for her, as she seizes both the huntress and her prey. Her patience is long put to the test: the Wasp suspects something and is on her guard; still, from time to time, a rash one gets caught. With a sudden rustle of wings half-unfurled as by the violent release of a clutch, the Mantis terrifies the newcomer, who hesitates for a moment, in her fright. Then, with the sharpness of a spring, the toothed fore-arm folds back on the toothed upper arm; and the insect is caught between the blades of the double saw. It is as though the jaws of a Wolf-trap were closing on the animal that had nibbled at its bait. Thereupon, without unloosing the cruel machine, the Mantis gnaws her victim by small mouthfuls. Such are the ecstasies, the prayers, the mystic meditations of the Prégo Diéou.

Of the scenes of carnage which the Praying Mantis has left in my memory, let me relate one. The thing happens in front of a work-yard of Bee-eating Philanthi. These diggers feed their larvæ on Hive-bees, whom they catch on the flowers while gathering pollen and honey. If the Philanthus who has made a capture feels that her Bee is swollen with honey, she never fails, before storing her, to squeeze her crop, either on the way or at the entrance of the dwelling, so as to make her disgorge the delicious syrup, which she drinks by licking the tongue which her unfortunate victim, in her death-agony, sticks out of her mouth at full length. This profanation of a dying creature, whose enemy squeezes its belly to empty it and feast on the contents, has something so hideous about it that I should denounce the Philanthus as a brutal murderess, if animals were capable of wrongdoing. At the moment of some such horrible banquet, I have seen the Wasp, with her prey, seized by the Mantis: the bandit was rifled by another bandit. And here is an awful detail: while the Mantis held her transfixed under the points of the double saw and was already munching her belly, the Wasp continued to lick the honey of her Bee, unable to relinquish the delicious food even amid the terrors of death. Let us hasten to cast a veil over these horrors.

We will return to the Sphex, with whose burrow we must make ourselves acquainted before we go further. This burrow is a hole made in fine sand, or rather in a sort of dust at the bottom of a natural shelter. Its entrance-passage is very short, merely an inch or two, without a bend, and leads to a single, roomy, oval chamber. The whole thing is a rough den, hastily dug out, rather than a leisurely and artistically excavated dwelling. I have explained that the reason for this simplicity is that the game is captured first and set down for a moment on the hunting-field while the Wasp hurriedly makes a burrow in the vicinity, a method of procedure which allows of but one chamber or cell to each retreat. For who can tell whither the chances of the day will lead the huntress for her second capture? The prisoner is heavy and the burrow must therefore be near; so to-day’s home, which is too far away for the next Ephippiger to be conveyed to it, cannot be utilized to-morrow. Thus, as each prey is caught, there is a fresh excavation, a fresh burrow, with its single chamber, now here, now there. Having said this, we will try a few experiments to see how the insect behaves when we create circumstances new to it.

A Sphex, dragging her prey along, is a few inches from the burrow. Without disturbing her, I cut with a pair of scissors the Ephippiger’s antennæ, which the Wasp, as we know, uses for harness-ropes. On recovering from the surprise caused by the sudden lightening of her load, the Sphex goes back to her victim and, without hesitation, now seizes the root of the antenna, the short stump left by the scissors. It is very short indeed, hardly a millimetre;1 no matter: it is enough for the Sphex, who grips this fag-end of a rope and resumes her hauling. With the greatest precaution, so as not to injure the Wasp, I now cut the two antennary stumps level with the skull. Finding nothing left to catch hold of at the familiar points, the insect seizes, close by, one of the victim’s long palpi and continues its hauling-work, without appearing at all perturbed by this change in the harness. I leave it alone. The prey is brought home and placed so that its head faces the entrance to the burrow; and the Wasp goes in by herself, to make a brief inspection of the inside of the cell before proceeding to warehouse the provisions. Her behaviour reminds us of that of the Yellow-winged Sphex in similar circumstances. I take advantage of this short moment to seize the abandoned prey, remove all its palpi and place it a little farther off, about half a yard from the burrow. The Sphex reappears and goes straight to her captive, whom she has seen from her threshold. She looks at the top of the head, she looks underneath, on either side, and finds nothing to take hold of. A desperate attempt is made: the Wasp, opening wide her mandibles, tries to grab the Ephippiger by the head; but the pincers have not a sufficient compass to take in so large a bulk and they slip off the round, polished skull. She makes several fresh endeavours, each time without result. She is at length convinced of the uselessness of her efforts. She draws back a little to one side and appears to be renouncing further attempts. One would say that she was discouraged; at least, she smooths her wings with her hind-legs, while with her front tarsi, which she first puts into her mouth, she washes her eyes. This, so it has always seemed to me, is a sign in Hymenoptera of giving up a job.

Nevertheless there is no lack of parts by which the Ephippiger might be seized and dragged along as easily as by the antennæ and the palpi. There are the six legs, there is the ovipositor: all organs slender enough to be gripped boldly and to serve as hauling-ropes. I agree that the easiest way to effect the storing is to introduce the prey head first, drawn down by the antennæ; but it would enter almost as readily if drawn by a leg, especially one of the front legs, for the orifice is wide and the passage short or sometimes even non-existent. Then how is it that the Sphex did not once try to seize one of the six tarsi or the tip of the ovipositor, whereas she attempted the impossible, the absurd, in striving to grip, with her much too short mandibles, the huge skull of her prey? Can it be that the idea did not occur to her? Then we will try to suggest it.

I offer her, right under her mandibles, first a leg, next the end of the abdominal rapier. The insect obstinately refuses to bite; my repeated blandishments lead to nothing. A singular huntress, to be embarrassed by her game, not knowing how to seize it by a leg when she is not able to take it by the horns! Perhaps my prolonged presence and the unusual events that have just occurred have disturbed her faculties. Then let us leave the Sphex to herself, between her Ephippiger and her burrow; let us give her time to collect herself and, in the calm of solitude, to think out some way of managing her business. I leave her therefore and continue my walk; and, two hours later, I return to the same place. The Sphex is gone, the burrow is still open, and the Ephippiger is lying just where I placed her. Conclusion: the Wasp has tried nothing; she went away, abandoning everything, her home and her game, when, to utilize them both, all that she had to do was to take her prey by one leg. And so this rival of Flourens, who but now was startling us with her cleverness as she dexterously squeezed her victim’s brain to produce lethargy, becomes incredibly helpless in the simplest case outside her usual habits. She, who so well knows how to attack a victim’s thoracic ganglia with her sting and its cervical ganglia with her mandibles; she, who makes such a judicious difference between a poisoned prick annihilating the vital influence of the nerves for ever and a pressure causing only momentary torpor, cannot grip her prey by this part when it is made impossible for her to grip it by any other. To understand that she can take a leg instead of an antenna is utterly beyond her powers. She must have the antenna, or some other string attached to the head, such as one of the palpi. If these cords did not exist, her race would perish, for lack of the capacity to solve this trivial problem.

The Wasp is engaged in closing her burrow, where the prey has been stored and the egg laid upon it. With her front tarsi she brushes her doorstep, working backwards and sweeping into the entrance a stream of dust which passes under her belly and spurts behind in a parabolic spray as continuous as a liquid spray, so nimble is the sweeper in her actions. From time to time the Sphex picks out with her mandibles a few grains of sand, so many solid blocks which she inserts one by one into the mass of dust, causing it all to cake together by beating and compressing it with her forehead and mandibles. Walled up by this masonry, the entrance-door soon disappears from sight.

I intervene in the middle of the work. Pushing the Sphex aside, I carefully clear the short gallery with the blade of a knife, take away the materials that close it and restore full communication between the cell and the outside. Then, with my forceps, without damaging the edifice, I take the Ephippiger from the cell, where she lies with her head at the back and her ovipositor towards the entrance. The Wasp’s egg is on the victim’s breast, at the usual place, the root of one of the hinder thighs: a proof that the Sphex was giving the finishing touch to the burrow, with the intention of never returning.

Having done this and put the stolen prey safely away in a box, I yield my place to the Sphex, who has been on the watch beside me while I was rifling her home. Finding the door open, she goes in and stays for a few moments. Then she comes out and resumes her work where I interrupted it, that is to say, she starts conscientiously stopping the entrance to the cell by sweeping dust backwards and carrying grains of sand, which she continues to heap up with scrupulous care, as though she were doing useful work. When the door is once again thoroughly walled up, the insect brushes itself, seems to give a glance of satisfaction at the task accomplished, and finally flies away.

The Sphex must have known that the burrow contained nothing, because she went inside and even stayed there for some time; and yet, after this inspection of the pillaged abode, she once more proceeds to close up the cell with the same care as though nothing out of the way had happened. Can she be proposing to use this burrow later, to return to it with a fresh victim and lay a new egg there? If so, her work of closing would be intended to prevent the access of intruders to the dwelling during her absence; it would be a measure of prudence against the attempts of other diggers who might covet the ready-made chamber; it might also be a wise precaution against internal dilapidations. And, as a matter of fact, some Hunting Wasps do take care to protect the entrance to the burrow by closing it temporarily, when the work has to be suspended for a time. Thus I have seen certain Ammophilæ, whose burrow is a perpendicular shaft, block the entrance to the home with a small flat stone when the insect goes off hunting or ceases its mining operations at sunset, the hour for striking work. But this is a slight affair, a mere slab laid over the mouth of the shaft. When the insect comes, it only takes a moment to remove the little flat stone; and the entrance is free.

On the other hand, the obstruction which we have just seen built by the Sphex is a solid barrier, a stout piece of masonry, where dust and gravel form alternate layers all the way down the passage. It is a definite performance and not a provisional defence, as is proved by the care with which it is constructed. Besides, as I think I have shown pretty clearly, it is very doubtful, considering the way in which she acts, whether the Sphex will ever return to make use of the home which she has prepared. The next Ephippiger will be caught elsewhere; and the warehouse destined to receive her will be dug elsewhere too. But these, after all, are only arguments: let us rather have recourse to experiment, which is more conclusive here than logic.

I allowed nearly a week to elapse, in order to give the Sphex time to return to the burrow which she had so methodically closed and to make use of it for her next laying if such were her intention. Events corresponded with the logical inferences: the burrow was in the condition wherein I left it, still firmly closed, but without provisions, egg or larva. The proof was decisive: the Wasp had not been back.

So the plundered Sphex enters her house, makes a leisurely inspection of the empty chamber, and, a moment afterwards, behaves as though she had not perceived the disappearance of the bulky prey which but now filled the cell. Did she, in fact, fail to notice the absence of the provisions and the egg? Is she, who is so clear-sighted in her murderous proceedings, dense enough not to realize that the cell is empty? I dare not accuse her of such stupidity. She is aware of it. But then why that other piece of stupidity which makes her close—and very conscientiously close—an empty burrow, one which she does not purpose to victual later? Here the work of closing is useless, is supremely absurd; no matter: the insect performs it with the same ardour as though the larva’s future depended on it. The insect’s various instinctive actions are then fatally linked together. Because one thing has been done, a second thing must inevitably be done to complete the first or to prepare the way for its completion; and the two acts depend so closely upon each other that the performing of the first entails that of the second, even when, owing to casual circumstances, the second has become not only inopportune but sometimes actually opposed to the insect’s interests. What object can the Sphex have in blocking up a burrow which has become useless, now that it no longer contains the victim and the egg, and which will always remain useless, since the insect will not return to it? The only way to explain this inconsequent action is to look upon it as the inevitable complement of the actions that went before. In the normal order of things, the Sphex hunts down her prey, lays an egg and closes her burrow. The hunting has been done; the game, it is true, has been withdrawn by me from the cell; never mind: the hunting has been done, the egg has been laid; and now comes the business of closing up the home. This is what the insect does, without another thought, without in the least suspecting the futility of her present labours.

To know everything and to know nothing, according as it acts under normal or exceptional conditions: that is the strange antithesis presented by the insect race. Other examples, also drawn from the Sphex tribe, will confirm this conclusion. The White-edged Sphex (S. albisecta) attacks medium-sized Locusts, whereof the different species to be found in the neighbourhood of the burrow all furnish her with their tribute of victims. Because of the abundance of these Acridians, there is no need to go hunting far afield. When the burrow, which takes the form of a perpendicular shaft, is ready, the Sphex merely explores the purlieus of her lair, within a small radius, and is not long in finding some Locust browsing in the sunshine. To pounce upon her and sting her, despite her kicking, is to the Sphex the matter of a moment. After some fluttering of its wings, which unfurl their carmine or azure fan, after some drowsy stretching of its legs, the victim ceases to move. It has now to be brought home, on foot. For this laborious operation the Sphex employs the same method as her kinswomen, that is to say, she drags her prize along between her legs, holding one of its antennæ in her mandibles. If she encounters some grassy jungle, she goes hopping and flitting from blade to blade, without ever letting slip her prey. When at last she comes within a few feet of her dwelling, she performs a manœuvre which is also practised by the Languedocian Sphex; but she does not attach as much importance to it, for she frequently neglects it. Leaving her captive on the road, the Wasp hurries home, though no apparent danger threatens her abode, and puts her head through the entrance several times, even going part of the way down the burrow. She next returns to the Locust and, after bringing her nearer the goal, leaves her a second time to revisit the burrow. This performance is repeated over and over again, always with the same anxious haste.

These visits are sometimes followed by grievous accidents. The victim, rashly abandoned on hilly ground, rolls to the bottom of the slope; and the Sphex on her return, no longer finding it where she left it, is obliged to seek for it, sometimes fruitlessly. If she find it, she must renew a toilsome climb, which does not prevent her from once more abandoning her booty on the same unlucky declivity. Of these repeated visits to the mouth of the shaft, the first can be very logically explained. The Wasp, before arriving with her heavy burden, inquires whether the entrance to the home be really clear, whether nothing will hinder her from bringing in her game. But, once this first reconnaissance is made, what can be the use of the rest, following one after the other, at close intervals? Is the Sphex so volatile in her ideas that she forgets the visit which she has just paid and runs afresh to the burrow a moment later, only to forget this new inspection also and to start doing the same thing over and over again? That would be a memory with very fleeting recollections, whence the impression vanished almost as soon as it was produced. Let us not linger too long on this obscure point.

At last the game is brought to the brink of the shaft, with its antennæ hanging down the hole. We now again see, faithfully imitated, the method employed in the like case by the Yellow-winged Sphex and also, but under less striking conditions, by the Languedocian Sphex. The Wasp enters alone, inspects the interior, reappears at the entrance, lays hold of the antennæ and drags the Locust down. While the Locust-huntress was making her examination of the home, I have pushed her prize a little farther back; and I obtained results similar in all respects to those which the Cricket-huntress gave me. Each Sphex displays the same obstinacy in diving down her burrow before dragging in the prey. Let us recall here that the Yellow-winged Sphex does not always allow herself to be caught by this trick of pulling away her Cricket. There are picked tribes, strong-minded families which, after a few disappointments, see through the experimenter’s wiles and know how to baffle them. But these revolutionaries, fit subjects for progress, are the minority; the remainder, mulish conservatives clinging to the old manners and customs, are the majority, the crowd. I am unable to say whether the Locust-huntress also varies in ingenuity according to the district which she hails from.

But here is something more remarkable; and it is this with which I wanted to conclude the present experiment. After repeatedly withdrawing the White-edged Sphex’ prize from the mouth of the pit and compelling her to come and fetch it again, I take advantage of her descent to the bottom of the shaft to seize the prey and put it in a place of safety where she cannot find it. The Sphex comes up, looks about for a long time and, when she is convinced that the prey is really lost, goes down into her home again. A few moments after, she reappears. Is it with the intention of resuming the chase? Not the least in the world: the Sphex begins to stop up the burrow. And what we see is not a temporary closing, effected with a small flat stone, a slab covering the mouth of the well; it is a final closing, carefully done with dust and gravel swept into the passage until it is filled up. The White-edged Sphex makes only one cell at the bottom of her shaft and puts one head of game into this cell. That single Locust has been caught and dragged to the edge of the hole. If she was not stored away, it was not the huntress’s fault, but mine. The Wasp performed her task according to the inflexible rule; and, also according to the inflexible rule, she completes her work by stopping up the dwelling, empty though it be. We have here an exact repetition of the useless exertions made by the Languedocian Sphex whose home has just been plundered.

It is almost impossible to make certain whether the Yellow-winged Sphex, who constructs several cells at the end of the same passage and stacks several Crickets in each, is equally illogical when accidentally disturbed in her proceedings. A cell can be closed though empty or imperfectly victualled, and the Wasp will none the less continue to come to the same burrow in order to work at the others. Nevertheless, I have reason to believe that this Sphex is subject to the same aberrations as her two kinswomen. My conviction is based on the following facts: the number of Crickets found in the cells, when all the work is done, is usually four to each cell, although it is not uncommon to find only three, or even two. Four appears to me to be the normal number, first, because it is the most frequent and, secondly, because, when rearing young larvæ dug up while they were still engaged on their first joint, I found that all of them, those actually provided with only two or three pieces of game as well as those which had four, easily managed the various Crickets wherewith I served them one by one, up to and including the fourth, but that after this they refused all nourishment, or barely touched the fifth ration. If four Crickets are necessary to the larva to acquire the full development called for by its organization, why are sometimes only three, sometimes only two provided for it? Why this enormous difference in the quantity of the victuals, some larvæ having twice as much as the others? It cannot be because of any difference in the size of the dishes provided to satisfy the grub’s appetite, for all have very much the same dimensions; and it can therefore be due only to the wastage of game on the way. We find, in fact, at the foot of the banks whose upper stages are occupied by the Sphex-wasps, Crickets that have been paralysed but lost, owing to the slope of the ground, down which they have slipped when the huntresses have momentarily left them, for some reason or other. These Crickets fall a prey to the Ants and Flies; and the Sphex-wasps who come across them take good care not to pick them up, for, if they did, they would themselves be admitting enemies into the house.

These facts seem to me to prove that, while the Yellow-winged Sphex’ arithmetical powers enable her to calculate exactly how many victims to capture, she cannot achieve a census of those which have safely reached their destination. It is as though the insect had no mathematical guide beyond an irresistible impulse that prompts her to hunt for game a definite number of times. When the Sphex has made the requisite number of journeys, when she has done her utmost to store the captures that result from these, her work is ended; and she closes the cell whether completely or incompletely provisioned. Nature has endowed her with only those faculties called for in ordinary circumstances by the interests of her larvæ; and, as these blind faculties, which cannot be modified by experience, are sufficient for the preservation of the race, the insect is unable to go beyond them.

I conclude therefore as I began: instinct knows everything, in the undeviating paths marked out for it; it knows nothing, outside those paths. The sublime inspirations of science and the astounding inconsistencies of stupidity are both its portion, according as the insect acts under normal or accidental conditions.