“They are light green in color, big-bellied, and wingless. With a little attention we distinguish the two minute posterior horns whence oozes the liquid on which the ants regale themselves. They have, underneath, a sucker, straight and very slender, a sort of bore which they push into the tender bark to extract from it the juices on which they live. The sucker once implanted at any convenient point, the animalcule seldom stirs from that spot. If it does decide to move a little, it is because its well has run dry and it must bore another close beside it. A promenade of merely the length of the branch is a liberty that only the most adventurous dare allow themselves. As a rule, the plant-louse sticks to the spot where it was born, to the very end.” “But how can the stem of a rose get so completely covered with those little green lice?” asked Emile. “That is easily explained,” answered his uncle. “Plant-lice multiply very rapidly, since each one, without exception, from the first to the last, whatever their number, becomes capable in a few days of procreating a family. The newly born settle down beside their mothers, and are themselves soon surrounded by their own progeny. These in turn, in a little while, have offspring of their own; and so on, indefinitely, as long as the season lasts. Thus the stem, the branch, the entire plant, become covered with lice so closely packed one against another that in places the real bark is hidden by this bark of vermin. “Have you ever seen a garden-patch of broad beans overrun by black lice? There, better than anywhere else, may be seen the rapidity of propagation. On that green expanse appears at first a small black stain, announcing the beginning of the invasion. It is a family of lice installed at the top of a beanstalk, the tenderest part of the plant, where the insects’ suckers can work to best advantage. The gardener, as soon as he is aware of what is going on, hastens to cut off this part of the stalk and crush it under his heel. He hopes to exorcise the evil by destroying this nest of vermin. “His hope is short-lived. A few days later, instead of one plant invaded there are dozens. He lops off again; he turns up the remaining leaves and examines them one by one; he crushes what vermin he finds, taking all pains to make the extermination complete. Will he make an end of it this time? Not at all: the black hordes reappear in greater numbers than ever; the invaded stalks can no longer be counted. A few lice that escaped the slaughter were enough to infest the whole patch of beans. The foliage hangs down, foul and withered; the young pods, riddled with punctures and corrugated with scars, shrivel up and can grow no larger. For this ill there is no remedy; the harvest is ruined.