What is this fleck of foam, like a drop of saliva, which we see in springtime on the weeds of the meadows; among others on the spurge, when its stems begin to shoot, and its sombre flowers open in the sunlight? "It is the work of an insect. It is the shelter in which the Cicadellina deposits her eggs. What a miraculous chemist! Her stiletto excels the finest craft of the botanical anatomist" by its sovereign art of separating the acrid poison which flows with the sap in the veins of the most venomous plants, and extracting therefrom only an inoffensive fluid. (7/2.) At every step the insects set us problems equally varied. The other creatures are nearer to us; they resemble us in many respects. But insects, almost the first-born of creation, form a world apart, and contain, in their tiny bodies, as Réaumur has admirably said, "more parts than the most gigantic animals." They have senses and faculties of their own, which enable them to accomplish actions, which are doubtless very simply related in reality, but which seem, to our minds, as extraordinary as the habits of the inhabitants of Mars might, if by chance they were to descend in our midst. We do not know how they hear, nor how they see through their compound eyes, and our ignorance concerning the majority of their senses still further increases the difficulty, which so often arrests us, of interpreting their actions. The tubercled Cerceris "finds by the hundred" and almost immediately a species of weevil, the Cleona ophthalmica, on which it feeds its larvae, and which the human eye, though it searches for hours, can scarcely find anywhere. The eyes of the Cerceris are like magnifying glasses, veritable microscopes, which immediately distinguish, in the vast field of nature, an object that human vision is powerless to discover. (7/3.) How does the Ammophila, hovering over the turf and investigating it far and wide, in its search for a grey grub, contrive to discern the precise point in the depth of the subsoil where the larva is slumbering in immobility? "Neither touch nor sight can come into play, for the grub is sealed up in its burrow at a depth of several inches; nor the scent, since it is absolutely inodorous; nor the hearing, since its immobility is absolute during the daytime." (7/4.) The Processional caterpillar of the pine-trees, "endowed with an exquisite hygrometric sensibility," is a barometer more infallible than that of the physicists. "It foresees the tempests preparing afar, at enormous distances, almost in the other hemisphere," and announces them several days before the least sign of them appears on the horizon. (7/5.)