As a rule the exodus is partial, being distributed over several days. When the whole swarm has disappeared there are still the wingless red Lice, the hump-backed pigmies, the progenitors of the big migrants. Some of them come to enjoy a little sunlight on the brink of the aperture. They soon go in again. Others follow them; perhaps they too are attracted by the brilliant sunshine. Then we see none at all. The festival of the light is not for them. For a week or two longer they lead a hand-to-mouth existence in the ruined gall, but their end is not far off. The withered gall starves them and old age kills them where they stand. So far there is nothing new: my laboratory experiments have already shown me what the terebinth in the garden tells me. The window-panes and test-tubes have even taught me more than the tree: they have enabled me to realize the part played by the winged Lice. In the liberty of the open air one fundamental detail of their story escapes me, for parturition takes place at a distance, I do not know where. The new-born Lice must be scattered everywhere, often at a considerable distance, as the emigrant’s flight informs me. Shall I then not find on the tree itself the little Lice with which my indoor observations have made me familiar? Yes: and in circumstances which are worth recording. Let me recapitulate: to escape from their galls, strongly-built dungeons without any outlet, the Terebinth-Lice have no means of breaking through. Though very clever at tickling vegetable tissues and making them swell into excrescences, they can do nothing with the walls of their prison. When it is time to go, however impatient they may be to get out, they must wait until the gall opens of itself, until the horn, in particular, splits into jagged segments at the top and the globe bursts open at the side. Until the fort is thus spontaneously dismantled, there is no possibility of escape. Now it may happen that the winged population is ripe and ready to increase and multiply before there is a breach in the wall, either because the gall is not yet sufficiently distended, or because it has dried up before its time and is henceforth unable to open. What do the captives do in the event of such a disaster? Precisely what they would do in the open air. Their business cannot be postponed. When the imperious hour has struck they bring forth their young, one on top of another, in such a crush that it is hardly possible to move. For good, or ill, the great task is accomplished. In this tangle of wings a-flutter in the midst of a waxy powder, this skirmish of legs seeking equilibrium on an ever-shifting support, many young Lice are trampled underfoot and injured, many are unable to strip and shrivel into grains of dust. The majority, none the less, so tenacious of life are they, contrive to escape in the swarming confusion.