make the stalk of the leaf. Even on the wall of a room or a curtain it would seem as though a dead leaf were sticking there; how much more when, as is always the case, the butterfly flies into some bush or thicket crowded with dry, brown leaves, and settles all amongst them. It is not that you don’t see it there that makes you miss it, but that you see it and scores of brown leaves all about it, every one of which looks just the same as itself. ------------------------------------------------------------------------ [Illustration: PROTECTIVE MIMICRY] The picture at the top shows birds pursuing butterflies, while in the one below the same birds have lost their prey, as the butterflies have alighted and show only the underside of their wings, which are practically indistinguishable from the neighbouring leaves. To make the matter plainer, in case this is not a very accurate description, here is the account of an eye-witness: “This species,” says Dr. Wallace, “was not uncommon in dry woods and thickets, and I often endeavoured to capture it without success, for after flying a short distance it would enter a bush among dry or dead leaves, and however carefully I crept up to the spot, I could never discover it till it would suddenly dart out again, and then disappear in a similar place. At length I was fortunate enough to see the exact spot where the butterfly settled, and though I lost sight of it for some time, I at length discovered that it was close before my eyes, but that in its position of repose it so closely resembled a dead leaf attached to a twig as almost certainly to deceive the eye, even when gazing full upon it.” Then follows a minute explanation of the imposture. “The end of the upper wings terminates in a fine point, just as the leaves of many tropical shrubs and trees are pointed, while the lower wings are somewhat more obtuse, and are lengthened out into a short, thick tail. Between these two points there runs a dark, curved line exactly representing the midrib of a leaf, and from this radiate on each side a few oblique marks, which well imitate the lateral veins. The tint of the under surface varies much, but it is always some ashy brown or reddish colour, which matches with those of dead leaves. The habit of the species is always to rest on a twig and among dead or dry leaves, and in this position, with the wings closely pressed together, their outline is exactly that of a moderately-sized leaf, slightly curved or shrivelled. The tail of the hind wings forms a perfect stalk, and touches the stick, while the insect is supported by the middle pair of legs, which are not noticed among the twigs and fibres that surround it. The head and antennæ are drawn back between the wings, so as to be quite concealed, and there is a little notch hollowed out at the very base of the wings, which allows the head to be retracted sufficiently. All these varied