Archive image from page 317 of The descent of man, and. The descent of man, and selection in relation to sex descentofmanse00darw Year: 1870 31 THE DESCENT OF MAN', [part u marked aifference in this respect among well-developed indi- viduals. In Lethrus, moreover, a beetle belonging to the same great division of the Lamellicorns, the males are known to fight, but are not provided with horns, though their mandi- bles are much larger than those of the female. The conclusion that the horns have been acquired as orna- ments is that which best agrees with the fact of their having been so immensely
Archive image from page 317 of The descent of man, and. The descent of man, and selection in relation to sex descentofmanse00darw Year: 1870 31 THE DESCENT OF MAN', [part u marked aifference in this respect among well-developed indi- viduals. In Lethrus, moreover, a beetle belonging to the same great division of the Lamellicorns, the males are known to fight, but are not provided with horns, though their mandi- bles are much larger than those of the female. The conclusion that the horns have been acquired as orna- ments is that which best agrees with the fact of their having been so immensely, yet not fixedly, developed—as shown by ♦heir extreme variability in the same species, and by their extreme diversity in closely allied species. This view will at first appear extremely improbable ; but we shall hereafter find with many animals standing much higher in the scale, namely, fishes, amphibians, reptiles, and birds, that various kinds of crests, knobs, horns, and combs have been developed apparently for this sole purpose. The males of Onitisfurcifer (fig. 21) and of some other species of the genus are furnished with singular projections on their an- terior femora, and with a great fork or pair of horns on the lower surface of the thorax. Judging from other insects, these may aid the male in clinging to the female. Al- though the males have not even a trace of a horn on the upper surface of the body, yet the females plainly exhibit a rudiment of a single horn on the head (fig. 22, «), and of a crest (J?) on the thorax. That the slight thoracic crest in the female is a rudiment of a projection proper to the male, though entirely absent in the male of this particu- lar species, is clear: for the female of Bubas bison (a genus which comes next to Onitis) has a similar slight crest on the Fig. 21.—Onitis furcifer, male, viewed from beneath.
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