The exodus lasts a couple of days. When the last loiterers have gone, let us open the gall entirely. The population has been rigorously sorted. At first it was a mixture of wingless red and winged black Lice. The latter have all left their dwelling; the others are still there. Those faithful to their home are small as before, squat, wrinkled and vermilion. Some of them bear the dorsal wallet, the maternal pouch. In them I recognize the legion of the mothers, now left alone in the house. For some time yet they linger on languidly, the gall being open to wind and weather; those less exhausted continue to produce offspring; mere abortions without a future; the time is too short and the house is falling into decay. At length they perish, with their belated young. The gall is a deserted ruin. Let us return to the emigrants, checked in their flight by the window-panes. In shape, colour and size they are all alike; the swarm is a monotonous repetition of the same individual; there is not one detail, however minute, to denote any difference. Yet we should expect to find males and females here. The Plant-louse, until this moment in the humble larval stage, has just acquired the attributes of the perfect insect. The heavy, pot-bellied Louse has become a slender midge, glorified by four iridescent wings. In any other insect this would be an infallible token of the nuptial frolics. Well, in the children of the galls, these wings, these adornments of maturity, belie their promises. There is no wedding and there can be none. Not a Louse in all the swarm is endowed with sex, and yet each has her brood, which she brings into the world by direct reproduction as her predecessors did. With a slip of straw moistened with saliva I pick up a winged Louse at random. I press its abdomen with a pin. My brutal obstetrics produces an immediate effect: the insect’s outraged flanks eject a string of five or six fœtuses; and the process is repeated without variation no matter what specimen we deliver. Let us, for that matter, consult the natural procedure. A couple of hours elapse and my prisoners behind the window are in the throes of childbirth on the glass of the panes, the plaster of the embrasure, the wood of the cross-bars. Matters become so urgent that any place suits them. The Louse in the act of parturition raises her two large wings, the upper pair, and gently moves the two small ones, the lower pair. The tip of the abdomen bends downwards, touches the supporting surface and the thing is done: a fœtus is implanted perpendicularly to the support, with its head uppermost. A little farther away, a second is deposited as promptly, followed by another and yet others. In one brief sitting the distribution is over. The average number of the litter is six.