There is also a Saperda of the Poplar and a Saperda [[225]]of the Cherry-tree. They have the same organisation and the same tools; but the former follows the methods of the Capricorn of the Oak, while the latter imitates the Capricorn of the Cherry-tree.
The poplar-tree is also inhabited by the Bronze Buprestis, which takes no defensive measures before going to sleep. It makes no barricade, no heap of shavings. And in the apricot-tree the Nine-spotted Buprestis behaves in the same way. In this case the grub is inspired by its intuitions to alter its plan of work to suit the coming Beetle. The perfect insect is a cylinder; the grub is a strap, a ribbon. The former, which wears unyielding armour, needs a cylindrical passage; the latter needs a very low tunnel, with a roof that it can reach with the pads on its back. The grub therefore changes its manner of boring: yesterday the gallery, suited to a wandering life in the thickness of the wood, was a wide burrow with a very low ceiling, almost a slot; to-day the passage is cylindrical. A gimlet could not bore it more accurately. This sudden change in the system of roadmaking on behalf of the coming insect once more shows us the foresight of this “bit of intestine.”
I could tell you of many other wood-eaters. Their tools are the same; yet each species displays special methods, tricks of the trade that have nothing to do with the tools. These grubs, then, like so many insects, show [[226]]us that instinct is not made by the tools, so to speak, but that the same tools may be used in various ways.
To continue the subject would be monotonous. The general rule stands out very clearly from these facts: the wood-eating grubs prepare the path of deliverance for the perfect insect, which will merely have to pass a barricade of shavings or pierce a screen of bark. By a curious reversal of the usual state of things, infancy is here the season of energy, of strong tools, of stubborn work; mature age is the season of leisure, of industrial ignorance, of idle diversions, without trade or profession. The providence of the human infant is the mother; here the baby grub is the mother’s providence. With its patient tooth, which neither the peril of the outside world nor the difficult task of boring through hard wood is able to discourage, it clears away for her to the supreme delights of the sun. [[227]]