those pupae armed with a multiple plowshare at the fore, a trident at the rear and rows of harpoons on the back wherewith to rip open the Osmia bee's cocoon and break through the hard crust of the hillside, betokened a field that was worth cultivating. The little that I said about her at the time brought me urgent entreaties: I was asked for a circumstantial chapter on the strange fly. The stern necessities of life postponed to an ever retreating future my beloved investigations, so miserably stifled. Thirty years have passed; at last, a little leisure is at hand; and here, in the harmas of my village, with an ardor that has in no wise grown old, I have resumed my plans of yore, still alive like the coal smoldering under the ashes. The Anthrax has told me her secrets, which I in my turn am going to divulge. Would that I could address all those who cheered me on this path, including first and foremost the revered Master of the Landes [Leon Dufour]. But the ranks have thinned, many have been promoted to another world and their disciple lagging behind them can but record, in memory of those who are no more, the story of the insect clad in deepest mourning.
In the course of July, let us give a few sideward knocks to the bracing pebbles and detach the nests of the Chalicodoma of the Walls [a mason bee] from their supports. Loosened by the shock, the dome comes off cleanly, all in one piece. Moreover—and this is a great advantage—the cells come into view wide open on the base of the exposed nest, for at this point they have no other wall than the surface of the pebble. In this way, without any scraping, which would be wearisome work for the operator and dangerous to the inhabitants of the dome, we have all the cells before our eyes, together with their contents, consisting of a silky, amber-yellow cocoon, as delicate and translucent as an onion peeling. Let us split the dainty wrapper with the scissors, chamber by chamber, nest by nest. If fortune be at all propitious, as it always is to the persevering, we shall end by finding that the cocoons harbor two larvae together, one more or less faded in appearance, the other fresh and plump. We shall also find some, no less plentiful, in which the withered larva is accompanied by a family of little grubs wriggling uneasily around it.
Examination at once reveals the tragedy that is happening under the cover of the cocoon. The flacid and faded larva is the mason bee's. A month ago, in June, having finished its mess of honey, it wove its silken sheath for a bedchamber wherein to take the long sleep which is the prelude to the metamorphosis. Bulging with fat, it is a rich and defenseless morsel for whoever is able to reach it. Then, in spite of apparently insurmountable obstacles, the mortar wall and the tent without an opening, the flesh-eating larvae appeared in the secret retreat and are now glutting themselves on the sleeper. Three different species take part in the carnage, often in the same nest, in adjoining cells. The diversity of shapes informs us of the presence of more than one enemy; the final stage of the creatures will tell us the names and qualities of the three invaders.
Forestalling the secrets of the future for the sake of greater clearness, I will anticipate the actual facts and come at once to the results produced. When it is by itself on the body of the mason bee's larva, the murderous grub belongs either to Anthrax trifasciata, MEIGEN, or to Leucospis gigas, FAB. But, if numerous little worms, often a score and more, swarm around the victim, then it is a Chalcidid's family which we have before us. Each of these ravagers shall have its biography. Let us begin with the Anthrax.
And first the grub, as it is after consuming its victim, when it remains the sole occupant of the mason bee's cocoon. It is a naked worm, smooth, legless and blind, of a creamy dead white, each segment a perfect ring, very much curved when at rest, but with the tendency to become almost straight when disturbed. Through the diaphanous skin, the lens distinguishes patches of fat, which are the cause of its characteristic coloring. When younger, as a tiny grub a few millimeters long, it is streaked with two different kinds of stains, some white, opaque and of a creamy tint, others translucent and of the palest amber. The former come from adipose masses in course of formation; the second from the nourishing fluid or from the blood which laves those masses.
Including the head, I count thirteen segments. In the middle of the body these segments are well marked, being separated by a slight groove; but in the forepart they are difficult to count. The head is small and is soft, like the rest of the body, with no sign of any mouth parts even under the close scrutiny of the lens. It is a white globule, the size of a tiny pin's head and continued at the back by a pad a little larger, from which it is separated by a scarcely appreciable crease. The whole is a sort of nipple swelling slightly on the upper surface; and its double structure is so difficult to perceive that at first we take it for the animal's head alone, though it includes both the head and the prothorax, or first segment of the thorax.
The mesothorax, or middle segment of the thorax, which is two or three times larger in diameter, is flattened in front and separated from the nipple formed by the prothorax and the head by a deep, narrow, curved fissure. On its front surface are two pale red stigmata, or respiratory orifices, placed pretty close together. The metathorax, or last segment of the thorax, is a little larger still in diameter and protrudes. These abrupt increases in circumference result in a marked hump, sloping sharply towards the front. The nipple of which the head forms part is set at the bottom of this hump.
After the metathorax, the shape becomes regular and cylindrical, while decreasing slightly in girth in the last two or three segments. Close to the line of separation of the last two rings, I am able to distinguish, not without difficulty, two very small stigmata, just a little darker in color. They belong to the last segment. In all, four respiratory orifices, two in front and two behind, as is the rule among Flies. The length of the full sized larva is 15 to 20 millimeters and its breadth 5 to 6.
Remarkable in the first place by the protuberance of its thorax and the smallness of its head, the grub of the Anthrax acquires exceptional interest by its manner of feeding. Let us begin by observing that, deprived of all, even the most rudimentary walking apparatus, the animal is absolutely incapable of shifting its position. If I disturb its rest, it curves and straightens itself in turns by a series of contractions, it tosses about violently where it lies, but does not manage to progress. It fidgets and gets no farther. We shall see later the magnificent problem raised by this inertness.
For the moment, a most unexpected fact claims all our attention. I refer to the extreme readiness with which the Anthrax' larva quits and returns to the Chalicodoma grub on which it is feeding. After witnessing flesh eating larvae at hundreds and hundreds of meals, I suddenly find myself confronted with a manner of eating that bears no relation to anything which I have seen before. I feel myself in a world that baffles my old experience. Let us recall the table manners of a larva living on prey, the Ammophila's for instance, when devouring its caterpillar. A hole is made in the victim's side; and the head and neck of the nursling dive deep into the wound, to root luxuriously among the entrails. There is never a withdrawal from the gnawed belly, never a recoil to interrupt the feast and to take breath awhile. The vivacious animal always goes forward, chewing, swallowing, digesting, until the caterpillar's skin is emptied of its contents. Once seated at table, it does not budge as long as the victuals last. To tease it with a straw is not always enough to induce it to withdraw its head outside the wound; I have to use violence. When removed by force and then left to its own devices, the creature hesitates for a long time, stretches itself and mouths around, without trying to open a passage through a new wound. It needs the attacking point that has just been abandoned. If it finds the spot, it makes its way in and resumes the work of eating; but its future is jeopardized from this time forward, for the game, now perhaps tackled at inopportune points, is liable to go bad.
With the Anthrax' grub, there is none of this mangling, none of this persistent clinging to the entrance wound. I have but to tease it with the tip of a hair pencil and forthwith it retires; and the lens reveals no wound at the abandoned spot, no such effusion of blood as there would be if the skin were perforated. When its sense of security is restored, the grub once more applies its pimple head to the fostering larva, at any point, no matter where; and, so long as my curiosity does not prevent it, keeps itself fixed there, without the least effort, or the least perceptible movement that could account for the adhesion. If I repeat the touch with the pencil, I see the same sudden retreat and, soon after, the same contact just as readily renewed.
This facility for gripping, quitting and regripping, now here, now there and always without a wound, the part of the victim whence the nourishment is drawn tells us of itself that