The Glow-Worm and Other Beetles Part 6

[Footnote 2: .117 to .156 inch.--_Translator's Note_.]

Apart from the general configuration, it will be seen that we have here the strikingly characteristic appearance of the pseudochrysalids of the Sitares, Oil-beetles and Zonites. There are the same rigid integuments, of the red of a cough-lozenge or virgin wax; the same cephalic mask, in which the future mouth-parts are represented by faintly marked tubercles; the same thoracic studs, which are the vestiges of the legs; the same distribution of the stigmata. I was therefore firmly convinced that the parasite of the Mantis-hunters could only be a Meloid.

Let us also record the description of the strange larva found devouring the heap of Mantes in the burrows of the Tachytes. It is naked, blind, white, soft and sharply curved. Its general appearance suggests the larva of some Weevil. I should be even more accurate if I compared it with the secondary larva of _Meloe cicatricosus_, of which I once published a drawing in the _Annales des sciences naturelles_.[3] If we reduce the dimensions considerably, we shall have something very like the parasite of the Tachytes.

[Footnote 3: It was his essays in this periodical, on the metamorphoses of the Sitares and Oil-beetles, that procured Fabre his first reputation as an entomologist.--_Translator's Note_.]

The head is large, faintly tinged with red. The mandibles are strong, bent into a pointed hook, black at the tip and a fiery red at the base. The antennae are very short, inserted close to the root of the mandibles. I count three joints: the first thick and globular, the other two cylindrical, the second of these cut short abruptly. There are twelve segments, apart from the head, divided by fairly definite grooves. The first thoracic segment is a little longer than the rest, with the dorsal plate very slightly tinged with russet, as is the top of the head. Beginning with the tenth segment, the body tapers a little. A slight scalloped rim divides the dorsal from the ventral surface.

The legs are short, white and transparent and end in a feeble claw. A pair of stigmata on the mesothorax, near the line of junction with the prothorax; a stigma on either side of the first eight abdominal segments; in all nine pairs of stigmata, distributed like those of the pseudochrysalis. These stigmata are small, tinged with red and rather difficult to distinguish. Varying in size, like the pseudochrysalid which seems to come from it, this larva averages nearly half an inch in length and an eighth of an inch in width.

The six little legs, feeble though they be, perform services which one would not at first suspect. They embrace the Mantis that is being devoured and hold her under the mandibles, while the grub, lying on its side, takes its meal at its ease. They also serve for locomotion.

On a firm surface, such as the wooden top of my table, the larva can move about quite well; it toddles along, dragging its belly, with its body straight from end to end. On fine, loose sand, change of position becomes difficult. The grub now bends itself into a bow; it wriggles upon its back, upon its side; it crawls a little way; it digs and heaves with its mandibles. But let a less crumbling support come to its a.s.sistance; and pilgrimages of some length are not beyond its powers.

I reared my guests in a box divided into compartments by means of paper part.i.tions. Each s.p.a.ce, representing about the capacity of a Tachytes-cell, received its layer of sand, its pile of Mantes and its larva. And more than one disturbance arose in this refectory, where I had reckoned upon keeping the banqueters isolated one from the other, each at its special table. This larva, which had finished its ration the day before, was discovered next day in another chamber, where it was sharing its neighbour's repast. It had therefore climbed the part.i.tion, which for that matter was of no great height, or else had forced its way through some c.h.i.n.k. This is enough, I think, to prove that the grub is not a strict stay-at-home, as are the larvae of the Sitares and the Oil-beetles when devouring the ration of the Anthophora.

I imagine that, in the burrows of the Tachytes, the grub, when its heap of Mantes is consumed, moves from cell to cell until it has satisfied its appet.i.te. Its subterranean excursions cannot cover a wide range, but they enable it to visit a few adjacent cells. I have mentioned how greatly the Tachytes' provision of Mantes varies.[4] The smaller rations certainly fall to the males, which are puny dwarfs compared with their companions; the more plentiful fall to the females. The parasitic grub to which fate has allotted the scanty masculine ration has not perhaps sufficient with this share; it wants an extra portion, which it can obtain by changing its cell. If it be favoured by chance, it will eat according to the measure of its hunger and will attain the full development of which its race allows; if it wander about without finding anything, it will fast and will remain small. This would explain the differences which I note in both the grubs and the pseudochrysalids, differences amounting in linear dimensions to a hundred per cent and more. The rations, rare or abundant according to the cells lit upon, would determine the size of the parasite.

[Footnote 4: The essay on the Tachytes has not yet appeared in English. It will form part of a volume ent.i.tled _More Hunting Wasps_.--_Translator's Note_.]

During the active period, the larva undergoes a few moults; I have witnessed at least one of these. The creature stripped of its skin appears as it was before, without any change of form. It instantly resumes its meal, which was interrupted while the old skin was shed; it embraces with its legs another Mantis on the heap and proceeds to nibble her. Whether simple or multiple, this moult has nothing in common with the renewals due to the hypermetamorphosis, which so profoundly change the creature's appearance.

Ten days' rearing in the part.i.tioned box is enough to prove how right I was when I looked upon the parasitic larva feeding on Mantes as the origin of the pseudochrysalis, the object of my eager attention. The creature, which I kept supplied with additional food as long as it accepted it, stops eating at last. It becomes motionless, retracts its head slightly and bends itself into a hook. Then the skin splits across the head and down the thorax. The tattered slough is thrust back; and the pseudochrysalis appears in sight, absolutely naked. It is white at first, as the larva was; but by degrees and fairly rapidly it turns to the russet hue of virgin wax, with a brighter red at the tips of the various tubercles which indicate the future legs and mouth-parts. This shedding of the skin, which leaves the body of the pseudochrysalis uncovered, recalls the mode of transformation observed in the Oil-beetles and is different from that of the Sitares and the Zonites, whose pseudochrysalis remains wholly enveloped in the skin of the secondary larva, a sort of bag which is sometimes loose, sometimes tight and always unbroken.

The mist that surrounded us at the outset is dispelled. This is indeed a Meloid, a true Meloid, one of the strangest anomalies among the parasites of its tribe. Instead of living on the honey of a Bee, it feeds on the skewerful of Mantes provided by a Tachytes. The North-American naturalists have taught us lately that honey is not always the diet of the Blister-beetles: some Meloidae in the United States devour the packets of eggs laid by the Gra.s.shoppers. This is a legitimate acquisition on their part, not an illegal seizure of the food-stores of others. No one, as far as I am aware, had as yet suspected the true parasitism of a carnivorous Meloid. It is nevertheless very remarkable to find in the Blister-beetles, on both sides of the Atlantic, this weakness for the flavour of Locust: one devours her eggs; the other a representative of the order, in the shape of the Praying Mantis and her kin.

Who will explain to me this predilection for the Orthopteron in a tribe whose chief, the Oil-beetle, accepts nothing but the mess of honey? Why do insects which appear close together in all our cla.s.sifications possess such opposite tastes? If they spring from a common stock, how did the consumption of flesh supplant the consumption of honey? How did the Lamb become a Wolf? This is the great problem which was once set us, in an inverse form, by the Spotted Sapyga, a honey-eating relative of the flesh-eating Scolia.[5]

I submit the question to whom it may concern.

[Footnote 5: The essays on these will appear in the volume, ent.i.tled _The Hunting Wasps_, aforementioned.--_Translator's Note_.]

The following year, at the beginning of June, some of my pseudochrysalids split open transversely behind the head and lengthwise down the whole of the median line of the back, except the last two or three segments. From it emerges the tertiary larva, which, from a simple examination with the pocket-lens, appears to me, in its general features, identical with the secondary larva, the one which eats the Tachytes' provisions. It is naked and pale-yellow, the colour of b.u.t.ter. It is active and wriggles with awkward movements.

Ordinarily it lies upon its side, but it can also stand in the normal position. The creature is then trying to use its legs, without finding sufficient purchase to enable it to walk. A few days later, it relapses into complete repose.

Thirteen segments, including the head, which is large, with a quadrilateral cranium, rounded at the sides. Short antennae, consisting of three knotted joints. Powerful curved mandibles, with two or three little teeth at the end, of a fairly bright red. l.a.b.i.al palpi rather bulky, short and with three joints, like the antennae. The mouth-parts, labrum, mandibles and palpi are movable and stir slightly, as though seeking food. A small brown speck near the base of each antenna, marking the place of the future eyes. Prothorax wider than the segments that come after it. These are all of one width and are distinctly divided by a furrow and a slight lateral rim. Legs short, transparent, without a terminal claw. They are three-jointed stumps.

Pale stigmata, eight pairs of them, placed as in the pseudochrysalis, that is, the first and largest pair on the line dividing the first two segments of the thorax and the seven others on the first seven abdominal segments. The secondary larva and the pseudochrysalis also have a very small stigma on the penultimate segment of the abdomen.

This stigma has disappeared in the tertiary larva; at least I cannot detect it with the aid of a good magnifying-gla.s.s.

Lastly, we find the same strong mandibles as in the secondary larva, the same feeble legs, the same appearance of a Weevil-grub. The movements return, but are less clearly marked than in the primary form. The pa.s.sage through the pseudochrysalid state has led to no change that is really worth describing. The creature, after this singular phase, is what it was before. The Meloes and Sitares, for that matter, behave similarly.

Then what can be the meaning of this pseudochrysalid stage, which, when pa.s.sed, leads precisely to the point of departure? The Meloid seems to be revolving in a circle: it undoes what it has just done, it draws back after advancing. The idea sometimes occurs to me to look upon the pseudochrysalis as a sort of egg of a superior organization, starting from which the insect follows the ordinary law of entomological phases and pa.s.ses through the successive stages of larva, nymph and perfect insect. The first hatching, that of the normal egg, makes the Meloid go through the larval dimorphism of the Anthrax and the Leucospis. The primary larva finds its way to the victuals; the secondary larva consumes them. The second hatching, that of the pseudochrysalis, reverts to the usual course, so that the insect pa.s.ses through the three customary forms: larva, nymph, adult.

The tertiary larval stage is of brief duration, lasting about a fortnight. The larva then sheds its skin by a longitudinal rent along the back, as did the secondary larva, uncovering the nymph, in which we recognize the Beetle, the genus and species being almost determinable by the antennae.

The second year's development turned out badly. The few nymphs which I obtained about the middle of June shrivelled up without attaining the perfect form. Some pseudochrysalids remained on my hands without showing any sign of approaching transformation. I attributed this delay to lack of warmth. I was in fact keeping them in the shade, on a what-not, in my study, whereas under natural conditions they are exposed to the hottest sun, beneath a layer of sand a few inches deep.

To imitate these conditions without burying my charges, whose progress I wished to follow comfortably, I placed the pseudochrysalids that remained on a layer of fresh sand at the bottom of a gla.s.s receiver.

Direct exposure to the sun was impracticable: it would have been fatal at a period when life is subterranean. To avoid it, I tied over the mouth of the receiver a few thicknesses of black cloth, to represent the natural screen of sand; and the apparatus thus prepared was exposed for some weeks to the most brilliant suns.h.i.+ne in my window.

Under the cloth cover, which, owing to its colour, favours the absorption of heat, the temperature, during the day-time, became that of an oven; and yet the pseudochrysalids persisted in remaining stationary. The end of July was near and nothing indicated a speedy hatching. Convinced that my attempts at heating would be fruitless, I replaced the pseudochrysalids in the shade, on the shelves, in gla.s.s tubes. Here they pa.s.sed a second year, still in the same condition.

June returned once more and with it the appearance of the tertiary larva, followed by the nymph. For the second time this stage of development was not exceeded; the one and only nymph that I succeeded in obtaining shrivelled, like those of the year before. Will these two failures, arising no doubt from the overdry atmosphere of my receivers, conceal from us the genus and the species of the Mantis-eating Meloid? Fortunately, no. The riddle is easily solved by deduction and comparison.

The only Melodiae in my part of the country which, though their habits are still unknown, might correspond in size with either the larva or the pseudochrysalis in question are the Twelve-pointed Mylabris and Schaeffer's Cerocoma. I find the first in July on the flowers of the sea scabious; I find the second at the end of May and in June on the heads of the iles d'Hyeres everlasting. This last date is best-suited to explain the presence of the parasitic larva and its pseudochrysalis in the Tachytes' burrows from July onwards. Moreover, the Cerocoma is very abundant in the neighbourhood of the sand-heaps haunted by the Tachytes, while the Mylabris does not occur there. Nor is this all: the few nymphs obtained have curious antennae, ending in a full, irregular tuft, the like of which is found only in the antennae of the male Cerocoma. The Mylabris, therefore, must be eliminated; the antennae, in the nymph, must be regularly jointed, as they are in the perfect insect. There remains the Cerocoma.

Any lingering doubts may be dispelled: by good fortune, a friend of mine, Dr. Beauregard, who is preparing a masterly work upon the Blister-beetles, had some pseudochrysalids of Schreber's Cerocoma in his possession. Having visited Serignan for the purpose of scientific investigations, he had searched the Tachytes' sand-heaps in my company and taken back to Paris a few pseudochrysalids of grubs fed on Mantes, in order to follow their development. His attempts, like mine, had miscarried; but, on comparing the Serignan pseudochrysalids with those of Schreber's Cerocoma, which came from Aramon, near Avignon, he was able to establish the closest resemblance between the two organisms.

Everything therefore confirms the supposition that my discovery can relate only to Schaeffer's Cerocoma. As for the other, it must be eliminated: its extreme rarity in my neighbourhood is a sufficient reason.

It is tiresome that the diet of the Aramon Meloid is not known. If I allowed myself to be guided by a.n.a.logy, I should be inclined to regard Schreber's Cerocoma as a parasite of _Tachytes tarsina_, who buries her h.o.a.rds of young Locusts in the high sandy banks. In that case, the two Cerocomae would have a similar diet. But I leave it to Dr.

Beauregard to elucidate this important characteristic.

The riddle is deciphered: the Meloid that eats Praying Mantes is Schaeffer's Cerocoma, of whom I find plenty, in the spring, on the blossoms of the everlasting. Whenever I see it, my attention is attracted by an unusual peculiarity: the great difference of size that is able to exist between one specimen and another, albeit of the same s.e.x. I see stunted creatures, females as well as males, which are barely one third the length of their better-developed companions. The Twelve-spotted Mylabris and the Four-spotted Mylabris present differences quite as p.r.o.nounced in this respect.

The cause which makes a dwarf or a giant of the same insect, irrespective of its s.e.x, can be only the smaller or greater quant.i.ty of food. If the larva, as I suspect, is obliged to find the Tachytes'

game-larder for itself and to visit a second and a third, when the first is too frugally furnished, it may be imagined that the hazard of the road does not favour all in the same way, but rather allots abundance to one and penury to another. The grub that does not eat its fill remains small, while the one that gluts itself grows fat. These differences of size, in themselves, betray parasitism. If a mother's pains had ama.s.sed the food, or if the family had had the industry to obtain it direct instead of robbing others, the ration would be practically equal for all; and the inequalities in size would be reduced to those which often occur between the two s.e.xes.

They speak, moreover, of a precarious, risky parasitism, wherein the Meloid is not sure of finding its food, which the Sitaris finds so deftly, getting itself carried by the Anthophora, after being born at the very entrance to the Bee's galleries and leaving its retreat only to slip into its host's fleece. A vagabond obliged to find for itself the food that suits it, the Cerocoma incurs the risk of Lenten fare.

One chapter is lacking to complete the history of Schaeffer's Cerocoma: that which treats of the beginning, the laying of the eggs, the egg itself and the primary larva. While watching the development of the Mantis-eating parasite, I took my precautions, in the first year, to discover its starting-point. By eliminating what was known to me and seeking among the Meloidae of my neighbourhood for the size that corresponded with the pseudochrysalids unearthed from the Tachytes'

burrows, I found, as I have said, only Schaeffer's Cerocoma and the Twelve-spotted Mylabris. I undertook to rear these in order to obtain their eggs.

As a standard of comparison, the Four-spotted Mylabris, of a more imposing size, was added to the first two. A fourth, _Zonitis mutica_, whom I did not need to consult, knowing that she was not connected with the matter in hand and being familiar with her pseudochrysalis, completed my school of egg-layers. I proposed, if possible, to obtain her primary larva. Lastly, I had formerly reared some Cantharides with the object of observing their egg-laying. In all, five species of Blister-beetles, reared in a breeding-cage, have left a few lines of notes in my records.

The method of rearing is of the simplest. Each species is placed under a large wire-gauze dome standing in a basin filled with earth. In the middle of the enclosure is a bottle full of water, in which the food soaks and keeps fresh. For the Cantharides, this is a bundle of ash-twigs; for the Four-spotted Mylabris, a bunch of bindweed (_Convolvus arvensis_) or psoralea (_P. biluminosa_), of which the insect nibbles only the corollae. For the Twelve-spotted Mylabris, I provide blossoms of the scabious (_Scabiosa maritima_); for the Zonitis, the full-blown heads of the eryngo (_Eryngium campestre_); for Schaeffer's Cerocoma, the heads of the iles d'Hyeres everlasting (_Helichrysum stoechas_). These three last nibble more particularly the anthers, more rarely the petals, never the leaves.

A sorry intellect and sorry manners, which hardly repay the minute cares involved in the rearing. To browse, to love her lord, to dig a hole in the earth and carelessly to bury her eggs in it: that is the whole life of the adult Meloid. The dull creature acquires a little interest only at the moment when the male begins to toy with his mate.

Every species has its own ritual in declaring its pa.s.sion; and it is not beneath the dignity of the observer to witness the manifestations, sometimes so very strange, of the universal Eros, who rules the world and brings a tremor to even the lowest of the brute creation. This is the ultimate aim of the insect, which becomes transfigured for this solemn function and then dies, having no more to do.

A curious book might be written on the subject of love among the beasts. Long ago the subject tempted me. For a quarter of a century my notes have been slumbering, dustily, in a corner of my library. I extract from them the following details concerning the Cantharides. I am not the first, I know, to describe the amorous preludes of the Meloid of the Ash-tree; but the change of narrator may give the narrative a certain value: it confirms what has already been said and throws light upon some points which may have escaped notice.

A female Cantharides is peacefully nibbling her leaf. A lover comes upon the scene, approaches her from behind, suddenly mounts upon her back and embraces her with his two pairs of hind-legs. Then with his abdomen, which he lengthens as much as possible, he energetically slaps that of the female, on the right side and the left by turns. It is like the strokes of a washerwoman's bat, delivered with frenzied rapidity. With his antennae and his fore-legs, which remain free, he furiously lashes the neck of the victim. While the blows fall thick as hail, in front and behind, the head and corselet of the amorous swain are shaken by an extravagant swaying and trembling. You would think that the creature was having an epileptic fit.

Meanwhile, the beloved makes herself small, opening her wing-cases slightly, hiding her head and tucking her abdomen under her, as though to escape the erotic thunderstorm that is bursting upon her back. But the paroxysm calms down. The male extends his fore-legs, shaken by a nervous tremor, like the arms of a cross and in this ecstatic posture seems to call upon the heavens to witness the ardour of his desires.

The antennae and the belly are held motionless, in a straight line; the head and the corselet alone continue to heave rapidly up and down.

This period of repose does not last long. Short as it is, the female, her appet.i.te undisturbed by the pa.s.sionate protestations of her wooer, imperturbably resumes the nibbling of her leaf.

Another paroxysm bursts forth. Once more the male's blows rain upon the neck of the tightly-clasped victim, who hastens to bow her head upon her breast. But he has no intention of allowing his lady-love to escape. With his fore-legs, using a special notch placed at the juncture of the leg and the tarsus, he seizes both her antennae. The tarsus folds back; and the antennae are held as in a vice. The suitor pulls; and the callous one is forced to raise her head. In this posture the male reminds one of a horseman proudly sitting his steed and holding the reins in both hands. Thus mastering his mount, he is sometimes motionless and sometimes frenzied in his demonstrations.

Then, with his long abdomen, he lashes the female's hinder-parts, first on one side, then on the other; the front part he flogs, hammers and pounds with blows of his antennae, head and feet. The object of his desires will be unfeeling indeed if she refuse to surrender to so pa.s.sionate a declaration.

Nevertheless she still requires entreating. The impa.s.sioned lover resumes his ecstatic immobility, with his quivering arms outstretched like the limbs of a cross. At brief intervals the amorous outbursts, with blows conscientiously distributed, recur in alternation with periods of repose, during which the male holds his fore-legs crosswise, or else masters the female by the bridle of her antennae. At last the flagellated beauty allows herself to be touched by the charm attendant on his thumps. She yields. Coupling takes place and lasts for twenty hours. The heroic part of the male's performance is over.

Dragged backwards behind the female, the poor fellow strives to uncouple himself. His mate carts him about from leaf to leaf, wherever she pleases, so that she may choose the bit of green stuff to her taste. Sometimes he also takes a gallant resolve and, like the female, begins to browse. You lucky creatures, who, so as not to lose a moment of your four or five weeks' existence, yoke together the cravings of love and hunger! Your motto is, "A short life and a merry one."

The Cerocoma, who is a golden green like the Cantharides, seems to have partly adopted the amorous rites of her rival in dress. The male, always the elegant s.e.x in the insect tribe, wears special ornaments.

The horns or antennae, magnificently complicated, form as it were two tufts of a thick head of hair. It is to this that the name Cerocoma refers: the creature crested with its horns. When a bright sun s.h.i.+nes into the breeding-cage, it is not long before the insects form couples on the bunch of everlastings. Hoisted on the female, whom he embraces and holds with his two pairs of hind-legs, the male sways his head and corselet up and down, all in a piece. This oscillatory movement has not the fiery precipitation of that of the Cantharides; it is calmer and as it were rhythmical. The abdomen moreover remains motionless and seems unskilled in those slaps, as of a washerwoman's bat, which the amorous denizen of the ash-tree so vigorously distributes with his belly.

While the front half of the body swings up and down, the fore-legs execute magnetic pa.s.ses on either side of the tight-clasped female, moving with a sort of twirl, so rapidly that the eye can hardly follow them. The female appears insensible to this flagellatory twirl. She innocently curls her antennae. The rejected suitor leaves her and moves on to another. His dizzy, twirling pa.s.ses, his protestations are everywhere refused. The moment has not yet arrived, or rather the spot is not propitious. Captivity appears to weigh upon the future mothers.

Before listening to their wooers they must have the open air, the sudden joyful flight from cl.u.s.ter to cl.u.s.ter on the sunlit slope, all gold with everlastings. Apart from the idyll of the twirling pa.s.ses, a mitigated form of the Cantharides' blows, the Cerocoma refused to yield before my eyes to the last act of the bridal.

Among males the same oscillations of the body and the same lateral flagellations are frequently practised. While the upper one makes a tremendous to-do and whirls his legs, the one under him keeps quiet.

Sometimes a third scatterbrain comes on the scene, sometimes even a fourth, and mounts upon the heap of his predecessors. The uppermost bobs up and down and makes swift rowing-strokes with his fore-legs; the others remain motionless. Thus are the sorrows of the rejected beguiled for a moment.