The industry of the larvae reminds us at every point what we have learned from the _Bruchus pisi_. Each grub excavates a lodging in the mass of the bean, respecting the epidermis, and preparing a circular trap-door which the adult can easily open with a push at the moment of emergence. At the termination of the larval phase the lodgements are betrayed on the surface of the bean by so many shadowy circles. Finally the lid falls, the insect leaves its cell, and the haricot remains pierced by as many holes as it has nourished grubs. Extremely frugal, satisfied with a little farinaceous powder, the adults seem by no means anxious to abandon the native heap or bin so long as there are beans untouched. They mate in the interstices of the heap; the mothers sow their eggs at random; the young larvae establish themselves some in beans that are so far intact, some in beans which are perforated but not yet exhausted; and all through the summer the operations of breeding are repeated once in every five weeks. The last generation of the year--that of September or October--sleeps in its cells until the warm weather returns. If the haricot pest were ever to threaten us seriously it would not be very difficult to wage a war of extermination against it. Its habits teach us what tactics we ought to follow. It exploits the dried and gathered crop in the granary or the storehouse. If it is difficult to attack it in the open it would also be useless. The greater part of its affairs are managed elsewhere, in our storehouses. The enemy establishes itself under our roof and is ready to our hand. By means of insecticides defence should be relatively easy. CHAPTER XX THE GREY LOCUST I have just witnessed a moving spectacle: the last moult of a locust; the emergence of the adult from its larval envelope. It was magnificent. I am speaking of the Grey Locust, the colossus among our acridians,[10] which is often seen among the vines in September when the grapes are gathered. By its size--and it grows as long as a man's finger--it lends itself to observation better than any other of its tribe. The larva, disgustingly fat, like a rude sketch of the perfect insect, is commonly of a tender green; but it is sometimes of a bluish green, a dirty yellow, or a ruddy brown, or even an ashen grey, like the grey of the adult cricket. The corselet is strongly keeled and indented, and is sprinkled with fine white spots. As powerful as in the adult insect, the hind-leg has a corpulent haunch, streaked with red, and a long shin like a two-edged saw.