I put two or three handfuls of my Maillanne haricots in a plate and place the swarming mass full in the sunlight on the edge of my bed of beans. I can imagine what will happen. The insects which are free and those which the stimulus of the sun will soon set free will take to their wings. Finding the fostering plant close by, they will stop and take possession of it. I shall see them exploring the pods and flowers and I shall not have long to wait before I witness the laying. That is how the Pea-weevil would act under similar conditions.
Well, no: to my confusion, matters do not fall out as I foresaw. For a few minutes the [[226]]insects bustle about in the sunlight, opening and closing their wing-cases to ease the mechanism of flight; then one by one they fly off. They mount high in the luminous air; they grow smaller and smaller and are soon lost to view. My persevering attention meets with not the slightest success: not one of the fly-aways settles on the haricots.
After tasting the joys of liberty to the full, will they return this evening, to-morrow, the day after? No, they do not return. All the week, at favourable hours, I inspect the rows of beans, flower by flower, pod by pod; never a Weevil do I see, never an egg. And yet it is a propitious time of year, for at this moment the mothers imprisoned in my jars are laying their eggs profusely on the dry haricots.
Let us try at another season. I have two other beds which I have had sown with the late haricot, the red cocot, partly for the use of the household, but principally for the sake of the Weevils. Arranged in convenient rows, the two beds will yield their crops one in August, the other in September and later.
I repeat with the red haricot the experiment which I made with the black. On several occasions, at opportune times, I release into the tangle of verdure large numbers of Bruchi from my glass jars, the general depot. Each time the result is plainly negative. In vain, all through the season, [[227]]I repeat my almost daily search, until both the crops are exhausted: I can never discover a single colonized pod, nor even a single Weevil perched upon the plant.
And yet this is not for lack of watching. My family are enjoined not to touch any part of certain rows which I reserve for my purposes; they are told to mind the eggs which might occur on the pods gathered. I myself examine the beans brought from my own or the neighbouring gardens, before handing them to the housekeeper to be shelled. All my trouble is wasted: there is nowhere a trace of any laying.
To these experiments in the open air I add others under glass. I place in long, narrow flasks fresh pods hanging from their stalks, some green, others mottled with crimson and containing seeds which are nearly ripe. Each flask receives its complement of Weevils. This time I obtain eggs, but they do not inspire me with much hope: the mother has laid them on the sides of the flasks and not on the pods. No matter: they hatch. For a few days I see the grubs roaming about, exploring the pods and the glass with equal zeal. In the end they all die, from the first to the last, without touching the food provided.
The conclusion to be drawn is obvious: the young and tender haricot is not the thing for them. Unlike the Pea-weevil, the Haricot-weevil refuses to entrust her family to beans that are not hardened [[228]]by age and desiccation; she declines to stop on my seed-patch, because she does not find the provisions which she requires.
Then what does she want? She wants old, hard beans, which clatter on the ground like little pebbles. I will satisfy her. I place in my flasks some very hard, tough pods, which have been long dried in the sun. This time the family prospers; the grubs bore through the parched shell, reach the seeds, enter them; and henceforth all goes well as well can be.
To all appearances, this is how the Weevil invades the farmer’s granary. Some haricots are left standing in the fields until both plants and pods, baked by the sun, are perfectly dry. This will make them easier to beat in order to separate the beans. It is now that the Weevil, finding things as she wants them, begins her laying. By getting in his crop a little late, the peasant gets the marauder into the bargain.