Mayer next tested the selective action of the females. He began by removing their wings and affixing to the stumps the wings of males. The males mated with the females quite as readily as under normal conditions, though the most conspicuous female characters had been exchanged for those of the male. After this he affixed female wings upon the males, but mating took place as usual. The females did not seem to detect anything unusual in their suitors, nor did normal males attempt to pair with males bearing female wings. Later he tried the experiment of dyeing the wings of three hundred males scarlet or green, and matched these against three hundred which were left untouched. The disguised, dyed males succeeded in pairing as easily as their normally-coloured brethren. The females exhibited no choice whatever. Hence, then, we have further reason to believe that with the Lepidoptera scent, not sight, is the channel by which mates are found. So far as the evidence goes, it seems to show conclusively that in all that concerns sexual relationships, scent is the guiding and determining factor. By scent the females attract the males, and by scent of another kind the males sharpen the procreative appetites of the females. If the interpretation adopted in these pages is correct, these manifestations and emanations of colour and scent are readily accounted for; for they are manifestations of inherent growth changes which, having started, are free to go on increasing in amplitude unless, and until, checked by natural selection. There is nothing unreasonable or improbable in this interpretation; on the contrary, it embraces also many other features hitherto ignored, but no less demanding an explanation. Such, for example, as the infinite variety of form and sculpture which the scales of the wings and the eggs display. These are details visible only by the aid of the microscope, but they demand explanation as much as the more obvious characters. Moreover they have the advantage of belonging to a set of characters which cannot in any way influence the choice, if choice there be, in the selection of mates, nor are they of a nature likely to affect the results of the struggle for existence. Of these characters, then—the sculpturing of the egg-shell and of the scales, the “nervation” of the wings, and coloration—we can say no more than that they are idiosyncrasies of growth, free to develop in any direction unless, and until, checked by natural selection, which will speedily eliminate disharmonies with the environment. CHAPTER XI BEETLES THAT “BLUFF”