CERCERIS BUPRESTICIDA

Every one has met with books which, according to his turn of mind, have been epoch-making, opening to him horizons whose very existence he had never guessed. They throw wide open the gates of a new world where henceforward he will use his mental powers; they are the spark which, falling on a hearth, kindles into flame materials otherwise never utilised. And very often it is mere chance which puts into our hands some book which makes a new starting-point in the evolution of our ideas. The most casual circumstance, a few lines which happen to come under our eye, decide our future and impel us into the path which thenceforward we shall follow. One winter evening, beside a stove where the ashes were yet warm, while my family slept, I was forgetting, while I read, all the cares of the morrow—the black cares of the professor of physics, who, after having piled one university diploma on another and rendered for a quarter of a century services whose merit was not denied, earns for himself and family 1600 francs—less than a groom in a well-to-do household. Such was the shameful parsimony of that day in educational matters; thus did Red tape will it. I was a free-lance, son of my solitary studies. Thus, amid my books I was putting aside acute professorial worries when I chanced to light on an entomological pamphlet which had come into my hands I forget how. It was by the patriarch of entomology of that day, the venerable savant Léon Dufour, on the habits of a Hymenopteron whose prey was the Buprestis. Certainly long ere this I had felt a great interest in insects; from childhood I had delighted in beetles, bees, and butterflies; as far back as I can recollect I see myself enraptured by the splendours of a beetle’s elytra, or the wings of the great Swallowtail butterfly. The materials lay ready on the hearth, but the spark to kindle them had been lacking. The accidental perusal of Léon Dufour’s pamphlet was that spark. I had a mental revelation. So then to arrange lovely beetles in a cork box, to name and classify was not the whole of science; there was something far superior, namely, the close study of the structure, and still more of the faculties of insects. Thrilled by emotion I read of a grand instance of this. A little later, aided by those fortunate circumstances which always befriend the ardent seeker, I published my first entomological work, the complement of Léon Dufour’s. It gained the honours of the Institute of France, a prize for experimental physiology being adjudged to it, and—far sweeter reward!—shortly after I received a most flattering and encouraging letter from the very man who had inspired me. From far away in the Landes the venerated master sent me the cordial expression of his enthusiasm, and urged me to continue my studies. At that recollection my old eyes still grow wet with a holy emotion. Oh, bright days of illusion, of faith in the future, what has become of you!

I hope that the reader will not be sorry to meet with an extract from the pamphlet which was the starting-point of my own researches, the more so that it is necessary for the understanding of what follows. So I will let my Master speak, only abridging slightly:—

In all insect history I know of no fact more curious and extraordinary than that which I am about to relate. It concerns a species of Cerceris which feeds its progeny on the most splendid kinds of Buprestis. Let me share with you, my friend, the vivid impressions gained by studying the habits of this Hymenopteron. In July 1839 a friend, who lives in the country, sent me two Buprestis bifasciata, an insect new to my collection, telling me that a kind of wasp which was carrying one of these pretty beetles had dropped it on his coat, and that a few minutes later a similar wasp had let fall another on the ground. In July 1840, having been called in as physician by my friend, I reminded him of his capture of the preceding year, and asked about the circumstances. Season and place corresponding with it, I hoped to do as much myself, but that particular day was dark and chilly, unfavourable therefore to the flight of Hymenoptera. Nevertheless, we made a tour of inspection in the garden walks, and seeing no insects I bethought myself of seeking in the ground for the homes of burrowing Hymenoptera. A tiny heap of sand recently thrown up, like a miniature mole-hill, attracted my attention. Scratching it away, I saw that it masked the orifice of a gallery descending far down. We carefully dug up the ground with a spade, and soon caught sight of the shining elytra of the coveted Buprestis. Soon I not only found wing-cases but a whole Buprestis, nay, [43]three and four displayed their gold and emerald. I could not believe my eyes. But that was only the prelude to my feast. In the chaos caused by my own exhumations a Hymenopteron appeared and was taken by me; it was the captor of the Buprestis, trying to escape from amid her victims. I recognised an old acquaintance, a Cerceris which I have found some two hundred times in Spain and around Saint Sever.

But my ambition was far from satisfied. It was not enough to know ravisher and prey: I wanted the larva for which all this rich store was laid up. After exhausting the first vein of Buprestis I hastened to make new excavations. Digging down more carefully I finally discovered two larvæ, which completed the good fortune of this campaign. In less than an hour I turned over three haunts of the Cerceris, and my booty was some fifteen whole Buprestids with fragments of a yet greater number. I calculated, and I believe it fell far short of the truth, that there were twenty-five nests in this garden, a fact representing an immense number of buried Buprestids. What must it be, I said to myself, in localities where in a few hours I have caught as many as sixty Cerceris on blossoming garlic, with nests most probably near, and no doubt provisioned quite as abundantly! Imagination, backed by probability, showed me underground, within a small space, B. bifasciata by thousands, although I who have observed the entomology of our parts for over thirty years have never noticed a single one. Once only, perhaps twenty years ago, did I see, sticking in a hole of an ancient oak, the abdomen and elytra of this insect. This fact was a ray of light, for it told me that the larva of B. bifasciata must live in the wood of the oak, and entirely explained the abundance of this beetle in a district where the forests consist chiefly of that tree. As Cerceris bupresticida is rare on the clayey hills of the latter stretch of country compared to the sandy plains where grows Pinus maritima, it became an interesting question whether this Hymenopteron when it inhabits the pine region provisions its nest as it does in [44]the oak district. I had good reason to believe that it did not, and you will soon see with some surprise how exquisite is the entomological tact of our Cerceris in her choice of the numerous kind of Buprestids.

Let us hasten to the pine region to taste new pleasures. The spot to be explored is a garden belonging to a property in the midst of forests of the maritime pines. The haunts of the Cerceris were soon recognised; they were exclusively found in the main paths, where the beaten and compact soil offered the burrowing Hymenoptera sufficient solidity for the construction of their subterranean dwellings. I visited some twenty, and I did it, I may say, by the sweat of my brow. It is a very laborious kind of exploration, for the nests and provisions are only found at the depth of one foot, so that it is necessary to invest the place by a line of square trenches seven or eight inches from the mouth of the hole, first inserting a stalk of grass in the gallery by way of clue. One must sap with a garden spade, so that the central clod, thoroughly detached all round, may be raised in one piece, then reversed on the ground and broken up carefully. Such is the manœuvre which I found successful. You would have shared our enthusiasm at the sight of the beautiful species of Buprestis which this new style of research revealed to our eager gaze. You ought to have heard our exclamations as each time the clod was reversed, new treasures were revealed rendered yet more brilliant by the hot sun, or when we discovered the larvæ of every age attached to their prey, or the cocoons of these larvæ incrusted with copper, bronze, and emerald. I who had been for three or four times ten years, alas! a practical entomologist had never beheld such an enchanting sight or had had such good fortune. We only wanted you to double our enjoyment. With ever increasing admiration we dwelt now on the brilliant Coleoptera and now on the marvellous sagacity of the Cerceris which had buried and laid them up for food. Can you believe it? Out of more than 400 beetles dug up, there was not one which did not belong to the old [45]genus Buprestis! Our Hymenopteron had not committed the smallest error. How much there is to learn from this intelligent industry in so small an insect! What value Latreille would have attached to the vote of this Cerceris in favour of the natural system!1

Let us pass on to the various contrivances of the Cerceris in making and provisioning her nest. I have already said that she chooses ground whose surface is beaten, compact, and solid. I should add that this ground must be dry and in full sunshine. This choice shows an intelligence, or, if you like, an instinct, which one is tempted to believe is the result of experience. Crumbly earth or mere sand would of course be easier to work, but then how construct an orifice which will remain wide open for ingress and exit, and a gallery whose walls will not constantly fall in, yield, and become blocked by the least rain? The choice is therefore both reasonable and perfectly well calculated.

Our burrowing Hymenopteron hollows her gallery with her mandibles and front tarsi, which accordingly are furnished with stiff points to act as rakes. The orifice must not only have the diameter of the miner’s body, but be able to admit a prey of larger bulk. This shows admirable forethought. As the Cerceris digs deeper she brings out the rubbish, and this makes the heap which I compared to a tiny molehill. The gallery is not vertical, as this would have exposed it to be filled up by wind or other causes. Not far from the starting-point it makes an angle; its length is from seven to eight inches. At the far end the industrious mother establishes the cradle of her progeny. Five cells, separate and independent of one another, are hollowed in the shape and nearly of the size of an olive; within they are solid and polished. Each can contain three Buprestids, the ordinary allowance for a larva. The Cerceris lays an egg amid the three victims, and then stops up the gallery with [46]earth, so that when once the provisions for the brood are laid in, the cells have no communication with the outside.

Cerceris bupresticida must be an indefatigable, daring, and skilful huntress. The cleanness, the freshness of the beetles which she buries in her den testify that they are seized just as they emerge from the wooden galleries where their final metamorphosis takes place. But what inconceivable instinct urges a creature that lives solely on the nectar of flowers to seek amid a thousand difficulties animal food for carnivorous offspring, which it will never see, and to post itself on trees quite unlike one another, which hide deep in their trunks the insects which are to fall her victims? What entomological tact, yet more inconceivable, makes her lay down a strict law to select them in a single generic group, and to catch species differing very considerably in size, shape, and colour? You observe how unlike are Buprestis biguttata, with its slender long body and dark colour; B. octoguttata, oval-oblong, with great stains of a beautiful yellow on a blue or green ground; and B. micans, three or four times the size of B. biguttata, with a splendid metallic greeny gold.

CERCERIS BUPRESTICIDA AND ITS PREY, BUPRESTICIS MICANS AND BUPRESTIS FLAVOMACULATA

There is another very singular fact in the manœuvres of our assassin of Buprestids. The buried ones, like those which I have seized in the grasp of their murderers, give no sign of life, and are unquestionably quite dead, yet, as I observed with surprise, no matter when they are dug up, not only do they keep all their freshness of colour, but every bit of them—feet, antennæ, palpi, and the membranes which unite the various parts of their bodies—is perfectly supple and flexible. At first one supposes the explanation, as far as concerns the buried ones, to be in the coolness of the ground, and absence of air and light, and for those taken from their murderers, in the very recent date of death. But observe that after my explorations, having isolated in cones of paper the numerous Buprestids dug up, I have often left them over thirty-six hours before pinning them out. And yet, notwithstanding the dryness and great heat of July, I have always found the same [47]flexibility in the joints. More than this, after that lapse of time, I have dissected several, and their visceræ were as perfectly preserved as if I had used my scalpel on the live insect. Now, long experience has taught me that even in a beetle of this size, when twelve hours have passed in summer after its death, the interior organs are either dried up or corrupted so that it is impossible to be sure of form or structure. There is some peculiarity about Buprestids put to death by the Cerceris which prevents corruption or desiccation for a week, or perhaps two. But what is this peculiarity?

To explain this wonderful preservation which makes an insect dead for several weeks into a piece of game not even high, but, on the contrary, as fresh as when first caught, and that during the greatest heat of summer, the skilful historian of Cerceris bupresticida supposes that there must be an antiseptic liquid acting as do the preparations used in preserving anatomical specimens. This liquid can only be the poison injected by the Hymenopteron into the body of the victim. A minute globule of the venomous humour accompanying the dart or lancet, destined for this purpose, acts as a kind of pickle or antiseptic fluid to preserve the flesh on which the larva is to feed. But then how superior to our processes are those of the Cerceris with regard to preserved food! We salt or smoke or enclose in tins hermetically sealed provisions which remain eatable, to be sure, but which are far, very far from having the qualities of fresh meat. Sardines drowned in oil, Dutch smoked herrings, cod hardened into slabs by salt and sun,—can any of these sustain comparison with the same fish brought alive to the kitchen? For meat properly so-called it is still [48]worse. Beyond salting and drying we have nothing which even for a short period can keep meat eatable. At the present time, after innumerable fruitless attempts of the most varied kind, special ships are equipped at great cost, which, furnished with powerful freezing apparatus, convey to us the flesh of sheep and oxen slaughtered in the Pampas of South America, frozen and kept from corruption by intense cold. How far superior is the method of the Cerceris, so rapid, so cheap, so expeditious! What lessons we should have to learn from such transcendental chemistry when an imperceptible drop of liquid poison renders in an instant the prey incorruptible! What am I saying?—incorruptible?—that is far from being all; the game is put into a condition which prevents desiccation, leaves their suppleness to the limbs, and maintains all the organs in pristine freshness, both the internal and external. In short, the Cerceris puts the insect into a state differing only from life by a corpse-like immobility.

Such is the conclusion arrived at by Léon Dufour before this incomprehensible marvel of the dead Buprestis untouched by corruption. An antiseptic fluid, incomparably superior to anything that human science could produce, would explain the mystery. He, the Master, skilful of the skilful, thoroughly used to most delicate anatomy; he who with magnifying glass and scalpel has scrutinised the whole circuit of entomology, leaving no corner unexplored; he, in short, for whom the organisation of insects has no secrets,—can advance no better conjecture than an antiseptic liquid to give at least a kind of explanation of a fact which leaves him confounded. Let me [49]insist on this comparison between the instinct of the animal and the reason of the sage in order the better to demonstrate in due time the overwhelming superiority of the former.

I will add but a few words to the history of the C. bupresticida. This Hymenopteron, common in the Landes, as we have heard, seems to be rare in the department of Vaucluse. It is only at long intervals that I have met with it, in autumn, and always isolated specimens, on the spiny heads of Eryngium campestre, in the environs of Avignon or round Orange and Carpentras. In the latter spot, so favourable to burrowing hymenoptera, from its sandy soil of Mollasse, I had the good fortune, not indeed of being present at the exhumation of such entomological riches as Léon Dufour describes, but of finding some old nests which I feel certain belonged to Cerceris bupresticida, from the shape of the cocoons, the kind of provender stored up, and the existence of the Hymenopteron in the neighbourhood. These nests, hollowed in a very friable sandstone, called safre in those parts, were filled with remains of beetles, easily recognised, and consisting of detached wing-cases, empty corslets, and whole feet. Now these remains of the larva’s feast all belonged to one species, and this was a Buprestis, Sphænoptera geminata. Thus from the west to the east of France, from the department of the Landes to Vaucluse, the Cerceris remains faithful to its favourite prey; longitude does not affect its predilections, a hunter of Buprestids among the maritime pines of the ocean sand-hills, it is equally so amid the evergreen oaks and olives of Provence. [50]The species is changed according to place, climate, and vegetation—causes influencing greatly the insect population, but the Cerceris keeps to its chosen genus, the Buprestis. For what strange reason? That is what I shall try to demonstrate.