The non-pungent Butterflies teach us something more. In order to protect themselves from the birds, they have imitated the pungent ones’ costume. Pray, then, let some one tell us why, among so many naked larvæ on which the little birds feast, not one has thought of assuming the Chrysomela’s black-buttoned overall. Unable to provide themselves with stinking retorts, they should at least possess a colourable imitation, in order to put their persecutors off. The simple creatures! It never entered their heads to protect themselves by mimesis! We will not blame them; it is not their fault. They are what they are; and no bird’s beak will make them change their costume. The Chrysomela’s defensive fluid has a look of essential oil: it discolours paper with a semitransparent stain which disappears by evaporation. Its colour is opalescent; its flavour is horrible; its odour is excessively strong and may be compared with that of the nitrobenzene of our laboratories. Were it not that I lack the leisure and the apparatus, I would gladly undertake a little research-work into this singular product of animal chemistry, which, I think, is quite as worthy of exploration by our tests as the milky exudations of the Salamander or the Toad. Meanwhile I commend the problem to the chemists. In addition to the eighteen flasks of essential oil, the grub possesses yet another protective device, which is at once defensive and locomotory. The end of the intestine expands, at the insect’s pleasure, into a large amber-coloured pimple, whence oozes a colourless or very pale-yellow liquid. I find it difficult to distinguish the odour of this liquid, because the strip of paper on which I collect it is always infected by the creature’s mere touch. Nevertheless I seem to recognize, in a fainter degree, the smell of nitrobenzene. Can there be any connection between the product of the dorsal flask and that of the intestinal pimple? There very well may be. I suspect, also, that it possesses special virtues, for the Odynerus, who is a fine judge in such matters, will tell us presently how greatly she appreciates this liquid.