These larvæ, I am firmly convinced, have been wounded by the Odynerus’ sting, for she would not carry a rapier merely for show. Possessing a weapon, she employs it. However, the wound is so slight that Réaumur and Léon Dufour did not suspect its existence. To their mind the prey was alive; to mine it is very nearly alive. In these conditions we can see to what perils the Odynerus’ egg would be exposed but for exquisitely prudent precautions. There they are, those restless grubs, to the number of two dozen in one cell, side by side with [[46]]the egg, which a mere nothing is enough to endanger. By what means will this very delicate germ escape the perils of the crowd?
As I foresaw by my process of reasoning, the egg is slung from the ceiling of the cell. A very short thread fastens it to the top wall and lets it hang free in space. The first time that I saw this egg, quivering at the end of its thread at the least jerk and confirming by its oscillations the correctness of my theoretical views, I experienced one of those moments of inward joy which atone for much vexation and weariness. I was to have many more such moments, as will be seen. If we pursue our investigations in the insect world with loving patience and a practised eye, we always find some marvel in store for us. The egg, I was saying, swings from the ceiling, held by a very short and extremely fine thread. The cell is sometimes horizontal, sometimes slanting. In the first case, the egg hangs perpendicularly to the axis of the cell and its lower end approaches to within a twelfth of an inch of the opposite wall; in the second case, the vertical direction of the egg forms a more or less acute angle with that axis.
I wished to follow the progress of this [[47]]hanging egg at my leisure, with the greater convenience of observation which is possible at home. With the egg of Eumenes Amadei this was all but impracticable, because of the cell, which could not be moved together with the block that most often serves as its foundation. A house of this kind demands observation on the spot. The Odynerus’ dwelling does not present the same drawback. When a cell is laid bare and found to be in the condition which I desire, I dig round it with the point of a knife until I detach a cylinder of earth containing the cell, which is reduced to an open trough, so as to conceal nothing of what is to happen inside. The victuals are extracted piecemeal, with every care, and decanted separately into a glass tube. I shall thus avoid the accidents that might be occasioned by the swarming heap of grubs during the inevitable shaking of the journey. The egg alone remains, swinging in the empty enclosure. A large tube receives the cylinder of earth, which is wedged in position with pads of cotton-wool. I place my booty in a tin box and carry it in my hand in such a position that the egg hangs vertically without striking against the walls of the cell. [[48]]
Never have I effected a removal which called for such nice precautions. An accidental movement might easily break the suspension-thread, which is so delicate that it needs the magnifying-glass to distinguish it; excessive oscillation might bruise the egg against the walls of the cell: I had to beware of turning it into a sort of bell-clapper dashing against its bronze prison. I walked, therefore, with the stiffness of an automaton, all of one piece, with steps methodically calculated. What a misfortune should some acquaintance appear and make me stop a moment, for a chat or a shake of the hand: the least distraction on my part would perhaps ruin my schemes! Still more embarrassing would it be should Bull, who cannot endure a black look, find himself muzzle to muzzle with a rival and try to get quits with him by flying at his throat. I should have to put an end to the fray, to avoid the scandal of a well-brought-up Dog showing intolerance of the village cur. The squabble would end in the breakdown of all my experimental scaffolding. And to think that the eager preoccupations of a person not entirely devoid of sense may sometimes be dependent on a Dog-fight! [[49]]
Lord be praised, the road is deserted! The journey is accomplished without hindrance; the thread, my great anxiety, does not break; the egg is not bruised; everything is in order. The little clod of earth is put in a place of safety, with the cell in a horizontal position. I distribute near the egg two or three of the grubs which I have collected; the complete allowance of provisions would cause trouble, now that the cell possesses only half its enclosing wall and is reduced to a semicylinder. Two days later, I find the egg hatched. The young larva, yellow in colour, is hanging by its hinder end, head downwards. It is busy with its first grub, whose skin is already growing limp. The suspension-cord consists of the short thread that supported the egg, with the addition of the slough, now reduced to a sort of crumpled ribbon. In order to remain sheathed in the end of this hollow ribbon, the hinder end of the new-born larva is at first slightly constricted and then swells into a button. If I disturb it while at rest, or if the victuals move, the larva withdraws, shrinking back upon itself, but without retreating into the ascending-sheath, as does the Eumenes’ larva. The tethering-cord does not serve as a scabbard, [[50]]as a refuge into which the larva can retire; it is rather an anchor-chain, which gives it a purchase on the ceiling and enables it to protect itself by shrinking to a safe distance from the heap of victuals. When things are quiet, the larva lengthens out and returns to its grub. Thus do matters happen at the start, according to my observations, of which some were made at home, in my rearing-jars, and others on the spot, when I unearthed cells containing a larva young enough for my purpose.
The first grub is devoured in twenty-four hours. The larva thereupon, so it seemed, goes through a moult. For at least some time it remains inactive and contracted; then it releases itself from the cord. It is now free, in contact with the heap of grubs and henceforth unable to step out of the way. The life-line has not lasted long; it protected the egg and safeguarded its hatching; but the larva is still very weak and the peril has not diminished. This means that we shall discover other means of protection.
By a very strange exception, whereof so far I know no other instance, the egg is laid before the provisions are stored. I have seen cells which as yet contained absolutely nothing in the way of victuals and which [[51]]nevertheless had the egg swinging from the ceiling. I have seen others, also furnished with the egg and so far containing only two or three head of game, a first instalment of the abundant dish of twenty-four. This early egg-laying, so utterly unlike what happens in the case of the other predatory Wasps, has its underlying motive, as we shall see; it has its logic at which we cannot fail to marvel.
The egg, laid in the empty cell, is not fixed at random on the first spot that offers upon the enclosing wall, which is vacant at all sides; it is hung near the far end, opposite the entrance. Réaumur had already noted this position of the budding larva, but without insisting on a detail whose importance he did not suspect:
“The grub,” he says, “is born at the bottom of the hole, that is, at the back of the cell.”
He does not speak of the egg, which he does not appear to have seen. This position of the grub was so well known to him that, wishing to attempt the rearing of a grub in a glass cell made with his own hands, he placed the larva at the bottom and the victuals on top of it. [[52]]