Soon the cross-bars of the window are peopled with vermin, jogging along with great activity, promiscuously with the winged Lice. What a to-do on the borderland of the invisible! What are they seeking, these busy atoms? What do they want? My ignorance will be their undoing. In two or three days the winged Lice die. Their part is played. That of the children is beginning. For some time yet the latter wander about, but at last nothing stirs at the window; the legion of Lice is dead. Before sweeping them away with a camel’s-hair brush, let us give a brief description of them. The new-born insects are pale green and slender in shape. Their length is not far short of a millimetre.[1] Nimble and standing fairly high on their legs, they trot about busily.
The globular galls burst and the hems, auricles and spindles begin to gape a little earlier than the horn-shaped galls, about the middle of September. The five gall-makers of the terebinth all have the same customs. After emerging from their open dwellings, all the adults, or winged black Lice, give [[280]]birth, within twenty-four hours, to a small number of young, some five or six, as do those of the horn-shaped galls.
The auricles yield a dumpy Louse, wider behind than before and of a dark olive colour. Her most remarkable feature is her sucker, which, folded underneath the insect, sticks out behind, recalling after a fashion a Grasshopper’s oviscapt. What can the puny creatures want with this mechanism? It is a sword, a sabre. Held erect, the implement would prevent any attempt at walking. To drive it into the food-plant, the insect apparently hoists itself on its legs, which correspond in length with the enormous probe. I should like to see this inordinate beak at work. My captives refuse what I give them: leaves and fresh galls. They lie huddled on the plug of cotton-wool which closes the tube. They have business to attend to. They want to get away; but to what?
Likewise squat of build, packed, not without a certain prettiness, into the shape of miniature Toads, the Lice from the globular galls are a pale yellowish brown, while those of the folded leaves are greenish black. [[281]]Neither the first nor the second have beaks of exaggerated length. That extraordinary rostrum, which sticks out behind, and, when at rest, resembles a caudal appendage, recurs in the young Lice from the spindle-shaped galls; but this time the little creature is oblong and its colour is pale green.
Let us cut short these dry details. It is enough if we recognize that these five fellow-guests of the terebinth are not of one race following different trades, but separate species. If the earlier generations, which all resemble one another, seemed to bear witness to a specific unity, the family of the winged Lice testifies to the contrary. These thickset insects and these slender ones; these bearers of the rostrum, sometimes of normal length and sometimes fantastically prolonged into the semblance of a caudal beak; these pale-green, olive-green, light-yellow insects are obviously independent forms.
A meticulous examination might find here preeminently all the characteristic features of the five categories; but the reader, repelled by prose descriptions, would soon turn the page. Let us pass on. Let us leave the insect laboratory, with its jars and test-tubes; [[282]]let us go out of doors to see how matters come to pass under natural conditions on the terebinth in the grounds.
The galls, frequently inspected during the hottest hours of the day, open before my eyes; the horns are splitting at the top, the globes are opening their sides, the others are parting their lips. The moment the fissure is wide enough the black emigrants appear, without haste, one by one, in absolute composure, despite the fierceness of the sun. The exodus was not accomplished with greater sobriety in the comparative darkness of my study. For a few seconds they linger in the breach; then, shedding a dusty trail from their floury backs, they spread their wings and are off. Their flight, favoured by the least breath of air, promptly carries them to a distance at which I soon lose sight of them.
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 [[283]]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 [[284]]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.