The exodus is worth close observation. I choose a few of the horn-shaped galls whose cracked tips announces the coming rupture. I expose them to the sun, in my study, facing a window, at a distance of a few paces from the closed casements. In the intervening space I set up a thick branch of leafy terebinth. I reckon upon this bait to attract the flying Lice, at least as a resting-spot. Next morning one of the horns opens, and by midday, in radiant sunlight, in calm, hot weather, the winged Lice are emerging. They come forth in small companies, without hurrying. It is a quiet, gently-flowing stream. They are dusted over with a waxy flour, all that remains of the sometime powder-puffs. When barely on the threshold of the cranny, they spread their wings and are off, shedding a faint trail of dust from their shoulders, shaken by the vibrations of their wings. With an undulating flight they all make straight for the window, where the light is brighter than elsewhere. They dash against the panes and slip down upon the cross-bars. There, bathed in the sunlight, without attempting to go further afield, they remain, collecting in a drift. Although the rest of the room is thoroughly well lit in all directions, the flight of the departing Lice is always directed towards the window facing the sun. There are thousands upon thousands of them; and not one takes another path, veering ever so little to the right or left. You feel a certain surprise at the invariable route pursued by these atoms which, when released, in a space well lit on every side, all, from the first to the last, rush towards the delights of a ray of sunshine. A handful of shot dropped from a height does not return to earth with greater certainty. The leaden pellets are attracted by gravity, to which all dead matter is subject, while the specks of living matter obey the light. My window-panes check them. In the absence of this obstacle, where would they go? Certainly not to the terebinth-trees near by. I have definite proof of this here, before my eyes. As a resting-place I have set up a bough of the cherished bush. None of the newly emerged insects takes notice of it; none of them pauses there. If on the way to the window one of them collides with the green thicket and falls upon a leaf, it quickly picks itself up again and makes off in a hurry to join the others in the sunlit window. Freed henceforth from the demands of the stomach, they are no longer interested in the terebinth; they all avoid it.