A little reassured by this conjecture, I take my stand at the foot of the rock, under a broiling sun; and, for half a day, I follow the evolutions of my flies. They flit quietly in front of the slope, at a few inches from the earthy covering. They go from one orifice to the next, but without even penetrating. For that matter, their big wings, extended crosswise even when at rest, would resist their entrance into a gallery, which is too narrow to admit those spreading sails. And so they explore the cliff, going to and fro and up and down, with a flight that is now sudden, now smooth and slow. From time to time, I see the Anthrax quickly approach the wall and lower her abdomen as though to touch the earth with the end of her ovipositor. This proceeding takes no longer than the twinkling of an eye. When it is done, the insect alights elsewhere and rests. Then it resumes its sober flight, its long investigations and its sudden blows with the tip of its belly against the layer of earth. The Bombylii [bee flies] observe similar tactics when soaring at a short height above the ground.
I at once rushed to the spot touched, lens in hand, in the hope of finding the egg which everything told me was laid during that tap of the abdomen. I could distinguish nothing, in spite of the closest attention. It is true that my exhaustion, together with the blinding light and scorching heat, made examination very difficult. Afterwards, when I made the acquaintance of the tiny thing that issues from that egg, my failure no longer surprised me. In the leisure of my study, with my eyes rested and with my most powerful glasses held in a hand no longer shaking with excitement and fatigue, I have the very greatest difficulty in finding the infinitesimal creature, though I know exactly where it lies. Then how could I see the egg, worn out as I was under the sun-baked cliff, how discover the precise spot of a laying performed in a moment by an insect seen only at a distance? In the painful conditions wherein I found myself, failure was inevitable.
Despite my negative attempts, therefore, I remain convinced that the Anthrax flies strew their eggs one by one, on the spots frequented by those bees who suit their grubs. Each of their sudden strokes with the tip of the abdomen represents a laying. They take no precaution to place the germ under cover; for that matter, any such precaution would be rendered impossible by the mother's structure. The egg, that delicate object, is laid roughly in the blazing sun, between grains of sand, in some wrinkle of the calcined chalk. That summary installation is sufficient, provided the coveted larva be near at hand. It is for the young grub now to manage as best it can at its own risk and peril.
Though the sunken roads of the Legue did not tell me all that I wished to know, they at least made it very probable that the coming grub must reach the victualled cell by its own efforts. But the grub which we know, the one that drains the bag of fat which may be a Chalicodoma larva or an Osmia larva, cannot move from its place, still less indulge in journeys of discovery through the thickness of a wall and the web of a cocoon. So an imperative necessity presents itself: there must perforce be an initial larva form, capable of moving and organized for searching, a form under which the grub would attain its end. The Anthrax would thus possess two larval states: one to penetrate to the provisions; the other to consume them. I allow myself to be convinced by the logic of it all; I already see in my mind's eye the wee animal coming out of the egg, endowed with sufficient power of motion not to dread a walk and with sufficient slenderness to glide into the smallest crevices. Once in the presence of the larva on which it is to feed, it doffs its travelling dress and becomes the obese animal whose one duty it is to grow big and fat in immobility. This is all very coherent; it is all deduced like a geometrical proposition. But to the wings of imagination, however smooth their flight, we must prefer the sandals of observed facts, the slow sandals with the leaden soles. Thus shod, I proceed.
Next year, I resume my investigations, this time on the Anthrax of the Chalicodoma, who is my neighbor in the surrounding wastelands and will allow me to repeat my visits daily, morning and evening if need be. Taught by my earlier studies, I now know the exact period of the Bee's hatching and therefore of the Anthrax' laying, which must take place soon after. Anthrax trifasciata settles her family in July, or in August at latest. Every morning, at nine o'clock, when the heat begins to be unendurable and when, to use [the author's gardener and factotum] Favier's expression, an extra log is flung on the bonfire of the sun, I take the field, prepared to come back with my head aching from the glare, provided that I bring home the solution of my puzzle. A man must have the devil in him to leave the shade at this time of the year. And what for, pray? To write the story of a fly! The greater the heat, the better my chance of success. What causes me to suffer torture fills the insect with delight; what prostrates me braces the fly. Come along!
The road shimmers like a sheet of molten steel. From the dusty and melancholy olive trees rises a mighty, throbbing hum, a great andante whose executants have the whole sweep of woods for their orchestra. 'Tis the concert of the Cicada, whose bellies sway and rustle with increasing frenzy as the temperature rises. The strident scrapings of the Cicada of the Ash, the Carcan of the district, lend their rhythm to the one note symphony of the common cicada. This is the moment: come along! And, for five or six weeks, oftenest in the morning, sometimes in the afternoon, I set myself to explore the flinty plateau.
The Chalicodoma's nests abound, but I cannot see a single Anthrax make a black speck upon their surface. Not one, busy with her laying, settles in front of me. At most, from time to time, I can just see one passing far away, with an impetuous rush. I lose her in the distance; and that is all. It is impossible to be present at the laying of the egg. I know the little that I learnt from the cliffs in the Legue and nothing more.
As soon as I recognize the difficulty, I hasten to enlist assistants. Shepherds—mere small boys—keep the sheep in these stony meadows, where the flocks graze, to the greater glory of our local mutton, on the camphor saturated badafo, that is to say, spike lavender. I explain as well as I can the object of my search; I talk to them of a big black Fly and the nests on which she ought to settle, the clay nests so well known to those who have learnt how to extract the honey with a straw in springtime and spread it on a crust of bread. They are to watch that fly and take good note of the nests on which they may see her alight; and, on the same evening, when they bring their flocks back to the village, they are to tell me the result of their day's work. On receiving their favorable report, I will go with them, next day, to continue the observations. They shall be paid for their trouble, of course. These latter day Corydons have not the manners of antiquity: they reck little of the seven holed flute cemented with wax, or of the beechen bowl, preferring the coppers that will take them to the village inn on Sunday. A reward in ready money is promised for each nest that fulfils the desired conditions; and the bargain is enthusiastically accepted.