The existence, then, of bright colours in this and other species in like case, seems to show that it has nothing to do with Sexual Selection, directly at any rate. The males having assembled, their presence is probably communicated to the female by the characteristic male odour, which is never of the same penetrating quality as that of the female. There is no need that it should possess this, for the females never seek their mates. The successful male, where several rivals are competing, is probably not simply the strongest, but he who also disperses the right odour necessary to provoke the pairing response. These illustrations furnished by the scent-hunting, scent-dispersing males and females are of the highest importance to students of the Sexual Selection theory, for they seem to show conclusively that coloration plays at any rate but a minor part therein. The importance of the scent-detecting organs is shown in the very different types of antennæ which obtain between male and female Moths, those of the male taking the form of huge feather-like structures, as in some Saturniidæ, and far exceeding those of the female in size. The methods of pairing which obtain among Butterflies and Moths, it is not surprising to find, are very different; for whereas in the former it takes place on the wing, in the latter the female is always in a resting position. Where the females are winged, long flights are often taken for the purpose of depositing and distributing the eggs: the flightless forms make no such excursions. A few, as in the case of some of the _Psychidæ_ are not only wingless, but limbless and maggot-like. They never leave the chrysalis case, but deposit their eggs inside it. Though there is undoubtedly much that is wonderful about the mating of these scent-distributing species, the history of the Moths of the genus Acentrophus is more wonderful and more mysterious still. For the females are aquatic. The males may sometimes be found in crowds fluttering over the surface of large but shallow sheets of water. The females, which are wingless, come to the surface and, like sirens, draw the males under water, where coupling takes place; after which they probably immediately die. But how do they discover their submerged mates? The escape from the water of any odour which the females may possess seems well nigh impossible.