The outer wrapper of paper scales, seeds or tufts of cotton-wool adheres fairly well. Beneath it is the real wall, consisting entirely of brown cement. The regularity of the shell gives us at first the idea of an intentional arrangement. The same idea occurs to us if we consider the cocoon of the Golden Cetonia, which is often prettily adorned with a rubble of droppings. It looks as though the grub collected from all around such building-stones as suit its purpose and encrusted them piecemeal in the mortar to give greater strength to the work. But this is not so at all. There is no mosaic-work. With its round rump the larva presses back the shifting material on every side; it adjusts it, levels it by simple pressure and then fixes it, at one point after another, by means of its mortar. Thus it obtains an egg-shaped cavity which it reinforces at leisure with fresh layers of plaster, until its excremental reserves are exhausted. Everything that is reached by the trickling of the cement sets like concrete and henceforth forms part of the wall, without any further intervention by the builder. To follow the grub through the whole course of its labours is impracticable: it works under a roof, protected from our indiscretion. But we can at least surprise the essential secret of its method. I select a cocoon whose softness indicates that the work is not yet completed. I make a moderate hole in it. If it were too wide, the breach would discourage the occupant and would make it impossible for the grub to repair its shattered roof, not for lack of materials, but for want of support. Let us make a cautious incision with the point of a penknife and look. The grub is rolled into a hook which is almost closed. Feeling uneasy, it puts its head to the sky-light which I have opened and investigates what has happened. The accident is soon perceived. Thereupon the hook closes entirely, the opposite poles of the grub come into mutual contact and then and there the builder is in possession of a pellet of cement which the stercoral factory has that moment furnished. To display such prompt obedience the intestine must certainly be peculiarly obliging. That of the Cetonia-larva is very highly so; directly it is called upon to act, it acts. Now the true function of the legs is revealed. Of no use for walking, they become precious auxiliaries when the time comes for building. They are tiny hands that seize the piece gathered by the mandibles, turn it over and over, and hold it while the mason subdivides it and applies it economically. The pincers of the mandibles serve as a trowel. They cut bit after bit from the lump, chewing and kneading the material and then spreading it on the edge of the breach. The forehead presses and smooths it as it is laid. When the supply of the moment is exhausted, the grub, coiling itself again into a closed hook, will obtain a further piece from its warehouse, which remains obedient to its orders.