To allow tranquility to be restored and habit to resume its rounds, to give the population time to increase and replace the fugitives and the injured, it would be best, I think, to leave the heap alone this year and not to resume my investigations until the next. After the thorough confusion due to the removal, I should jeopardize success by being too precipitate. Let us wait one year more. I decide accordingly, curb my impatience and resign myself. We will simply confine ourselves to enlarging the heap, when the leaves begin to fall, by accumulating the refuse that strews the paddock, so that we may have a richer field of operations.
In the following August, my visits to the mound of leaf-mould become a daily habit. By two o'clock in the afternoon, when the sun has cleared the adjacent pine-trees and is shining on the heap, numbers of male Scoliae arrive from the neighbouring fields, where they have been slaking their thirst on the eryngo-heads. Incessantly coming and going with an indolent flight, they circle round the heap. If some female rise from the soil, those who have seen her dart forward. A not very turbulent affray decides which of the suitors shall be the possessor; and the couple fly away over the wall. This is a repetition of what I used to see in the Bois des Issards. By the time that August is over. The males have ceased to show themselves. The mothers do not appear either: they are busy underground, establishing their families.
On the 2nd of September, I decide upon a search with my son Emile, who handles the fork and the shovel, while I examine the clods dug up. Victory!
A magnificent result, finer than any that my fondest ambition would have dared to contemplate! Here is a vast array of Cetonia-larvae, all flaccid, motionless, lying on their backs, with a Scolia's egg sticking to the centre of their abdomen; here are young Scolia-larvae dipping their heads into the entrails of their victims; here are others farther advanced, munching their last mouthfuls of a prey which is drained dry and reduced to a skin; here are some laying the foundation of their cocoons with a reddish silk, which looks as if it had been dyed in Bullock's blood; here are some whose cocoons are finished. There is plenty of everything, from the egg to the larva whose period of activity is over. I mark the 2nd of September as a red-letter day; it has given me the final key to a riddle which has kept me in suspense for nearly half a century.
I place my spoils religiously in shallow, wide-mouthed glass jars containing a layer of finely sifted mould. In this soft bed, which is identical in character with the natal surroundings, I make some faint impressions with my fingers, so many cavities, each of which receives one of my subjects, one only. A pane of glass covers the mouth of the receptacle. In this way I prevent a too rapid evaporation and keep my nurselings under my eyes without fear of disturbing them. Now that all this is in order, let us proceed to record events.
The Cetonia-larvae which I find with a Scolia's egg upon their ventral surface are distributed in the mould at random, without special cavities, without any sign of some sort of structure. They are smothered in the mould, just as are the larvae which have not been injured by the Wasp. As my excavations in the Bois des Issards told me, the Scolia does not prepare a lodging for her family; she knows nothing of the art of cell-building.
Her offspring occupies a fortuitous abode, on which the mother expends no architectural pains. Whereas the other Hunting Wasps prepare a dwelling to which the provisions are carried, sometimes from a distance, the Scolia confines herself to digging her bed of leaf-mould until she comes upon a Cetonia-larva. When she finds a quarry, she stabs it on the spot, in order to immobilize it; and, again on the spot, she lays an egg on the ventral surface of the paralysed creature. That is all. The mother goes in quest of another prey without troubling further about the egg which has just been laid. There is no effort of carting or building. At the very spot where the Cetonia-grub is caught and paralysed, the Scolia-larva hatches, grows and weaves its cocoon. The establishment of the family is thus reduced to the simplest possible expression.
