In both cases the rage for rapid multiplication is the same. The recluses soon produce offspring, who desert the natal shelter and proceed to settle elsewhere as colonists. At last, its flanks drained dry, the viviparous little insect dies in its withered arbour. How many were they, coming from under the lichens and climbing to the assault of the terebinth? There were thousands of them; and this multitude is not enough. Hastily each Louse attacks her leaflet with her beak; she makes herself a lair out of its swollen tip and immediately gives birth to other Lice, multiplying ten- or perhaps a hundredfold in this invasion of the innumerable. The tree has now its full number of colonists, all capable of founding populous tribes. Are we to regard them as different branches of the same trade union, of the same family, exploiting the terebinth in various fashions, according to the point attacked? We hesitate to regard them as strangers to one another, when they are employed on the same work; yet there are significant reasons for concluding that we have here a duality or multiplicity of species. Besides the disparity of the work accomplished, there is, at the outset, one distinctive feature: the colour of the eggs, of which some are black and others red. These vividly contrasted hues must correspond with independent ancestries. It is even possible that a patient examination, capable of analysing this minute object, would find differences in husks of the same colour. All my own searches beneath patches of lichen and in the crevices of dead wood end in nothing more than the discovery of two sorts of ovular carapaces but of two only, at least to judge by appearances; and yet on the tree we shall find five categories of workers who, though resembling one another, build very dissimilar structures. If there are no other germs, germs which have escaped my careful observation, it would seem, therefore that the eggs have different contents under an identical shell, whether black or red. Lastly, the configuration, that essential characteristic of the species, displays, in late autumn, very emphatic differentiating features. Up to this late season, the inmates of the galls of every form are so much alike that it is impossible to distinguish them one from another once they are taken from their dwellings. When the final exodus comes, at the close of the year, a generation makes its appearance which differs greatly from its predecessors, giving final proof of multiple species, to the number of five. Their generic name is Pemphigus, which is to say, bubble, capsule, bladder. This scientific name is well deserved. The Terebinth-lice and some others that pursue similar callings, living on the elm and the poplar, are, in a word, artificers of swellings: by the incessant tickling of their suckers they cause the formation of hollow excrescences, which are at once board and lodging to the community.