Archive image from page 308 of The descent of man . The descent of man : and selection in relation to sex descentofmanseledarw Year: 1874 COLEOPTERA. 295 tie belonging to the same great division of the Lamellicorns, the males are known to fight, but are not provided with horns, though their mandibles are much larger than those of the female. The conclusion that the horns have been acquired as ornaments is that which best agrees with the fact of their having been so immensely, yet not fixedly, developed,—as shown by their extreme variability in the same species, and by their extreme diversity
Archive image from page 308 of The descent of man . The descent of man : and selection in relation to sex descentofmanseledarw Year: 1874 COLEOPTERA. 295 tie belonging to the same great division of the Lamellicorns, the males are known to fight, but are not provided with horns, though their mandibles are much larger than those of the female. The conclusion that the horns have been acquired as ornaments is that which best agrees with the fact of their having been so immensely, yet not fixedly, developed,—as shown by their 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 stand- ing 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 Onitis furcifer (fig. 21), and of some other .species of the genus, are furnished with singular projections on their anterior fe- mora, 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. Although the males have not even a trace of a horn on the upper surface of the body, yet the females plainly exhibit a rudi- 21. Onitis of a single horn on the head (fig. 22, a), male and of a crest (b) on the thorax. That the slight thoracic crest in the female is a rudiment of a projection proper to the male, though en- tirely absent in the males of this particular species, is clear: for the female of Bubas bison (a genus which comes next to Onitis) has a similar slight crest on the thorax. Fig. furcifer, viewed from be neath.
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