It attains its object, for the most part, within the twenty-four hours. I see the worm making a hole in the tough skin of the seed; I watch its efforts; I catch sight of it half-sunk in the beginning of a gallery whose entrance is dusty with white flour, the refuse from the boring. It works its way in and penetrates into the heart of the seed. Its evolution is so rapid that it will emerge in the adult form in five weeks’ time.
This hasty development permits several generations to take place in the course of the year. I have seen four. On the other hand, an isolated couple supplied me with a family of eighty. Let us consider only half this number, to allow for the [[233]]two sexes, which I take to be equally represented. At the end of the year, the couples resulting from this source will therefore be represented by the fourth power of forty, reaching in terms of larvæ the frightful total of over two and a half millions. What a heap of haricots such a legion would destroy!
The larva’s methods remind us at all points of what the Pea-weevil showed us. Each grub digs itself a cell in the floury mass, while respecting the skin in the form of a protective disk, which the adult will easily be able to push out at the moment of leaving. Towards the end of the larval phase, the cells show through on the surface of the bean as so many dark circles. At last the lid falls off, the insect leaves its cell and the haricot remains pierced with as many holes as it had grubs feeding on it.
Very frugal, satisfied with a few floury scraps, the adults seem not at all anxious to abandon the heap so long as beans worth exploiting remain. They mate in the interstices of the stack; the mothers scatter their eggs at random; the young grubs make themselves at home, some in the untouched haricots, some in the beans that are holed but not yet exhausted; and the swarming is repeated every five weeks throughout the summer, after which the last generation, the one born in September or October, slumbers in its cells till the return of the warm weather. [[234]]
If ever the spoiler of the haricots became too ominously threatening, it would not be very difficult to wage a war of extermination upon her. We know from her habits the best tactics to follow. She ravages the dry and gathered crop, stored in the granaries. It is an irksome matter to attend to her in the open fields; and it is also almost useless. The bulk of her business is conducted elsewhere, in our warehouses. The enemy settles down under our roof, within our reach. This being so, with the aid of insecticides defence becomes relatively easy. [[235]]
[1] Or, if the reader prefers, the Swell-belly. Gus, in the Provençal dialect, means both ‘guts’ and ‘bigger.’—Translator’s Note. [↑]
‘And Thestylis wild thyme and garlic beats
For harvest hinds, o’erspent with toil and heats.’—