demeanour of the protected or venomous species, which birds and other insect-eaters know and respect. It might be supposed that the young Zoniopoda is itself unpalatable; but this is scarcely probable, for when the deceptive black mask is once dropped, the excessive shyness, love of concealment, and protective colouring of the insect show that it is much sought after by birds. While setting this down as an undoubted case of "mimicry," although it differs in some respects from all other cases I have seen reported, I cannot help remarking that this most useful word appears to be in some danger of losing the meaning originally attached to it in zoology. There are now very few cases of an accidental resemblance found between two species in nature which are not set down by someone to "mimicry," some in which even the wildest imagination might well fail to see any possible benefit to the supposed mimic. In cases where the outward resemblance of some feeble animal to a widely different and well-protected species, or to some object like a leaf or stick, and where such resemblance is manifestly advantageous and has reacted on and modified the life habits, it is conceivable that slight spontaneous variations in the structure and colouring of the unprotected species have been taken advantage of by the principle of natural selection, and a case of "mimicry" set up, to become more and more perfect in time, as successive casual variations in the same direction increased the resemblance. The stick-insect is perhaps the most perfect example where resemblance to an inanimate object has been the result aimed at, so to speak, by nature; the resemblance of the volucella fly to the humble-bee, on which it is parasitical, is the most familiar example of one species growing like another to its own advantage, since only by means of its deceptive likeness to the humble-bee is it able to penetrate into the nest with impunity. These two cases, with others of a similar character, were first called cases of "mimicry" by Kirby and Spence, in their ever-delightful _Introduction to Entomology--_an old book, but, curiously enough in these days of popular treatises on all matters of the kind, still the only general work on insects in the English language which one who is not an entomologist can read with pleasure.