THREE STROKES OF A DAGGER

Insect life: Souvenirs of a naturalist by Jean-Henri Fabre, is part of the HackerNoon Books Series. You can jump to any chapter in this book here. THREE STROKES OF A DAGGER

VII. THREE STROKES OF A DAGGER

There can be no doubt that the Sphex uses her greatest skill when immolating a cricket; it is therefore very important to explain the method by which the victim is sacrificed. Taught by my numerous attempts to observe the war tactics of the Cerceris, I immediately used on the Sphex the plan already successful with the former, i.e. taking away the prey and replacing it by a living specimen. This exchange is all the easier because, as we have seen, the Sphex leaves her victim while she goes down her burrow, and the audacious tameness, which actually allows her to take from your fingertips, or even off your hand, the cricket stolen from her and now offered, conduces most happily to a successful result of the experiment by allowing the details of the drama to be closely observed.

It is easy enough to find living crickets; one has only to lift the first stone, and you find them, crouched and sheltering from the sun. These are the young ones of the current year, with only rudimentary wings, and which, not having the industry of the perfect insect, do not yet know how to dig deep [94]retreats where they would be beyond the investigations of the Sphex. In a few moments I find as many crickets as I could wish, and all my preparations are made. I ascend to the top of my observatory, establish myself on the flat ground in the midst of the Sphex colony and wait.

A huntress comes, conveys her cricket to the mouth of her hole and goes down alone. The cricket is speedily replaced by one of mine, but placed at some distance from the hole. The Sphex returns, looks round, and hurries to seize her too distant prey. I am all attention. Nothing on earth would induce me to give up my part in the drama which I am about to witness. The frightened cricket springs away. The Sphex follows closely, reaches it, darts upon it. Then there is a struggle in the dust when sometimes conqueror, sometimes conquered is uppermost or undermost. Success, equal for a moment, finally crowns the aggressor. In spite of vigorous kicks, in spite of bites from its pincer-like jaws, the cricket is felled and stretched on its back.

The murderess soon makes her arrangements. She places herself body to body with her adversary, but in a reverse position, seizes one of the bands at the end of the cricket’s abdomen and masters with her forefeet the convulsive efforts of its great hind-thighs. At the same moment her intermediate feet squeeze the panting sides of the vanquished cricket, and her hind ones press like two levers on its face, causing the articulation of the neck to gape open. The Sphex then curves her abdomen vertically, so as to offer a convex surface impossible for the [95]mandibles of the cricket to seize, and one beholds, not without emotion, the poisoned lancet plunge once into the victim’s neck, next into the jointing of the two front segments of the thorax, and then again towards the abdomen. In less time than it takes to tell, the murder is committed, and the Sphex, after setting her disordered toilette to rights, prepares to carry off her victim, its limbs still quivering in the death-throes. Let us reflect a moment on the admirable tactics of which I have given a faint sketch. The Cerceris attacks a passive adversary, incapable of flight, whose sole chance of safety is found in a solid cuirass whose weak points the murderers know. But here what a difference! The prey is armed with redoubtable mandibles, capable of disembowelling the aggressor if they can seize her, and a pair of strong feet, actual clubs, furnished with a double row of sharp spines, which can be used alternatively to enable the cricket to bound far away from an enemy or to overturn one by brutal kicks. Accordingly, note what precautions on the part of the Sphex before using her dart. The victim, lying on its back, cannot escape by using its hind levers, for want of anything to spring from, as of course it would were it attacked in its normal position, as are the big Weevils by Cerceris tuberculata. Its spiny legs, mastered by the forefeet of the Sphex, cannot be used as offensive weapons, and its mandibles, held at a distance by the hind-feet of the Hymenopteron, open threateningly but can seize nothing. But it is not enough for the Sphex to render it impossible for her victim to hurt her: she must hold it so firmly garrotted that no [96]movement can turn the sting from the points where the drop of poison must be instilled, and probably it is in order to hinder any motion of the abdomen that one of the end segments is grasped. If a fertile imagination had had free play to invent a plan of attack it could not have devised anything better, and it is questionable whether the athletes of the classic palestra when grappling an adversary would have assumed attitudes more scientifically calculated.

I have just said that the dart is plunged several times into the victim’s body, once under the neck, then behind the prothorax, lastly near the top of the abdomen. It is in this triple blow that the infallibility, the infused science of instinct, appear in all their magnificence. First let us recall the chief conclusions to which the preceding study of the Cerceris have led us. The victims of Hymenoptera whose larva live on prey are not corpses, in spite of entire immobility. There is merely total or partial paralysis, and more or less annihilation of animal life, but vegetative life—that of the nutritive organs—lasts a long while yet, and preserves from decomposition the prey which the larvæ are not to devour for a considerable time. To produce this paralysis the predatory Hymenoptera use just those methods which the advanced science of our day might suggest to the experimental physiologist—namely, wounding, by means of a poisoned dart, those nervous centres which animate the organs of locomotion. We know too that the various centres or ganglia of the nervous chain in articulate animals act to a certain degree independently, so that injury to one only causes, at all events immediately, paralysis of the corresponding [97]segment, and this in proportion as the ganglia are more widely separated and distant from each other. If, on the contrary, they are soldered together, injury to the common centre causes paralysis of all the segments where its ramifications spread. This is the case with Buprestids and Weevils, which the Cerceris paralyses by a single sting, directed at the common mass of the nerve centres in the thorax. But open a cricket, and what do we find to animate the three pairs of feet? We find what the Sphex knew long before the anatomist, three nerve centres far apart. Thence the fine logic of the three stabs. Proud science! humble thyself.

Crickets sacrificed by Sphex flavipennis are no more dead, in spite of all appearances, than are Weevils struck by a Cerceris. The flexibility of the integuments displays the slightest internal movement, and thus makes useless the artificial means used by me to show some remains of life in the Cleonus of Cerceris tuberculata. If one closely observes a cricket stretched on its back a week or even a fortnight or more after the murder, one sees the abdomen heave strongly at long intervals. Very often one can notice a quiver of the palpi and marked movements in the antennæ and the bands of the abdomen, which separate and then come suddenly together. By putting such crickets into glass tubes I have kept them perfectly fresh for six weeks. Consequently, the Sphex larvæ, which live less than a fortnight before enclosing themselves in their cocoons, are sure of fresh food as long as they care to feast.

The chase is over; the three or four crickets needed to store a cell are heaped methodically on their backs, their heads at the far end, their feet [98]toward the entrance. An egg is laid on each. Then the burrow has to be closed. The sand from the excavation lying heaped before the cell door is promptly swept out backward into the passage. From time to time fair-sized bits of gravel are chosen singly, the Sphex scratching in the fragments with her forefeet, and carrying them in her jaws to consolidate the pulverised mass. If none suitable are at hand, she goes to look for them in the neighbourhood, apparently choosing with such scrupulous care as a mason would show in selecting the best stones for a building. Vegetable remains and tiny bits of dead leaf are also employed. In a moment every outward sign of the subterranean dwelling is gone, and if one has not been careful to mark its position, it is impossible for the most attentive eye to find it again. This done, a new burrow is made, provisioned and walled up as soon as the Sphex has eggs to house. Having finished laying, she returns to a careless and vagabond life until the first cold weather ends her well-filled existence.

The Sphex’s task is accomplished. I will finish mine by an examination of her weapon. The organ destined for the elaboration of her poison is composed of two elegantly branched tubes communicating separately with a common reservoir or pear-shaped vial, whence proceeds a slender channel leading to the axis of the sting and conducting to its end the little poisoned drop. The dart is extremely small, and not such as one would expect from the size of the Sphex, especially from the effect which her sting produces on crickets. The point is quite smooth, without the barbs found in the sting of the hive bee. [99]The reason of this is evident. The bee uses her sting to avenge an injury only at the cost of life, the barbs preventing its withdrawal from the wound, and thus causing mortal ruptures in the viscera at the end of the abdomen. What could the Sphex have done with a weapon which would have been fatal the first time it was used? Even supposing that the barbed dart could have been withdrawn, I doubt if any Hymenopteron using its weapon, especially to wound game destined for its progeny, would be provided with one. For here the dart is not a fine gentleman’s weapon, unsheathed for vengeance, which is said to be the pleasure of the gods, but a very costly one, since the vindictive bee sometimes pays for it with life. It is a worker’s tool, on which depends the future of the larvæ, thus it should be one easily used in a struggle with captured prey, plunging into and coming out of the flesh without any delay—a condition much better fulfilled by a smooth blade than by a barbed one.

I wished to ascertain at my own expense if the Sphex’s sting be very painful—that sting which knocks over robust victims with frightful rapidity. Well, I own with great admiration that it is slight and cannot be at all compared as to pain with those of the bee and the irascible wasp. It hurts so little that, instead of using pincers, I never hesitated to catch with my fingers any Sphegidæ which I wanted for my researches. I may say the same of the various Cerceris, Philanthides, Palares, and even of the huge Scoliides, whose very look is terrifying, and in general of all predatory Hymenoptera which I have been able to observe. I except, however, those that hunt spiders, [100]the Pompili, and even their sting is far less severe than that of a bee.

One last remark. We know how furiously Hymenoptera armed with a sting used only for defence rush at the bold man who disturbs their nest, and punish his temerity. Those on the contrary whose sting is used only for hunting are very pacific, as if they guessed how important for their family is the little poison drop in their vase. That droplet is the safeguard of their race—I might really say their means of subsistence; therefore they use it economically, in the serious business of the chase, with no parade of vengeful courage. I was not once punished by a sting when I established myself amid colonies of our various predatory Hymenoptera, whose nests I overturned, carrying off larvæ and provisions. To induce the creature to use its weapon, one must lay hold of it, and even then the skin is not always pierced, unless one puts within reach a part more delicate than the fingers, such as the wrist.

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