Proc. Zool. Society for 1900, pp. 837-69. Footnote 95: Fabre, Insect Life, p. 165. Footnote 96: Proc. Zool. Society for 1900, pp. 837-69. Footnote 97: There are two British species of Elephant Hawk-Moth, the large and small. The caterpillar of the former has four false eyes, that of the latter only two. Footnote 98: Poulton, The Colour of Animals, pp. 258-61. Footnote 99: Leland O. Howard, The Insect Book. Footnote 100: Proc. Zool. Society for 1900, pp. 837-69. Footnote 101: Leland O. Howard, The Insect Book. Footnote 102: Nature, June 25th, 1903. Footnote 103: Poulton, The Colour of Animals, pp. 258-61. ------------------------------------------------------------------------ CHAPTER XX Butterfly resemblances—A living leaf—How spiders trap butterflies—Butterfly doubles—Suggested explanation—More evidence wanted—Warning coloration—A theory on trust—A straightforward test—Advice to naturalists—A strange omission. SOME of the most remarkable instances of protective resemblances amongst insects are exhibited by butterflies, one, perhaps, being the most perfect existing under nature; however, I only say perhaps. This is the world-renowned leaf butterfly of Sumatra, and elsewhere in the Malay Archipelago. Of the great purple emperor family, it is purple on the upper surface, and gleams like a meteor as it shoots about in the rich, sun-bathed atmosphere of the tropics, its conspicuousness being enhanced by a sort of miniature, sharp-pointed swallow-tail, in which the hinder pair of wings end, and a broad, orange bar, like a sash or scarf of honour, running right across the anterior wings. It flies boldly and strongly, and when it descends upon a bush or shrub it is as though a little purple torch had shot through the foliage; but all at once, even though you see it come down just in front of you, it has vanished utterly—the torch has gone out. You may look and look, but unless you know the trick, and have seen the settling, and never taken your eyes off the exact spot, you will never find the butterfly, or see anything more of it until, all at once, it gleams in the air again. For the under part of the leaf butterfly’s lovely purple wings is like the leaf indeed—“the sere, the yellow leaf”—with a midrib running down the centre veinings on either side, a curled tip at the top, a stalk at the bottom, and everything proper to leaves, but not as a rule to butterflies. All four wings join in this effect, for being thrown up in the usual way when the insect settles, the leaf-like shape is thus brought about, one-half of the under surface being seen on each side in clear profile, whilst the purple now lies hid within, like the pictures on a folded screen. As for the body of the butterfly, that is hidden inside the wings too; the legs are all but invisible, and the two little pointed swallow-tails, just touching the plant’s stem with their mutual tip,