She is a gorgeous and powerful Fly; and her costume, with its brown and yellow bands, shows a vague resemblance to that of the Wasps. Our fashionable theorists have availed themselves of this brown and yellow to cite the Volucella as a striking instance of protective mimicry. Obliged, if not on her own behalf, at least on that of her family, to introduce herself as a parasite into the Wasp’s home, she resorts, they tell us, to trickery and craftily dons her victim’s livery. Once inside the Wasps’-nest, she is taken for one of the inhabitants and attends quietly to her business. The simplicity of the Wasp, duped by a very clumsy imitation of her garb, and the depravity of the Fly, concealing her identity under a counterfeit presentment, exceed the limits of my credulity. The Wasp is not so silly nor the Volucella so clever as we are assured. If the latter really meant to deceive the Wasp by her appearance, we must admit that her disguise is none too successful. Yellow sashes round the abdomen do not make a Wasp. It would need more than that and, above all, a slender figure and a nimble carriage; and the Volucella is thickset and corpulent and sedate in her movements. Never will the Wasp take that unwieldly insect for one of her own kind. The difference is too great. Poor Volucella, mimesis has not taught you enough! You ought—this is the essential point—to have adopted a Wasp’s shape and you forgot to do so; you remained a fat Fly, far too easily recognized. Nevertheless, you penetrate into the terrible cavern; you are able to stay there for a long time, without danger, as the eggs profusely strewn on the wrapper of the Wasps’-nest show. How do you set about it? Let us, first of all, remember that the Volucella does not enter the enclosure in which the combs are stacked: she keeps to the outer surface of the paper rampart and there lays her eggs. Let us, on the other hand, recall the Polistes placed in the company of the Wasps in my breeding-cage. Here of a surety is one who need not have recourse to mimicry to find acceptance. She belongs to the guild, she is a Wasp herself. Any of us that had not the trained eye of the entomologist would confuse the two species. Well, this stranger, so long as she does not become too importunate, is quite readily tolerated by the caged Wasps. None seeks to pick a quarrel with her. She is even admitted to the table, the strip of paper smeared with honey. But she is doomed if she inadvertently sets foot upon the combs. Her costume, her shape, her size, which tally almost exactly with the costume, shape and size of the Wasp, do not save her from her fate. She is at once recognized as a stranger and attacked and slaughtered with the same vigour as the larvæ of the Hylotoma and the Saperda, neither of which bears any outward resemblance to the Wasps.