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Show 372 SEXUAL SELECTION. PART II. the same species and by their extreme diversit~ in closely-allied species-is that they have been acqmred as ornaments. This view will at first appear extremely improbable; but we shall hereafter find with many animals, standing much higher in the sc~le, na~ely fishes, amphibians, reptiles and birds, t at varwu. kinds of crests, knobs, horns and combs have been developed apparently for this sole purpose. . The males of Onitis jurc1jer (fig. 20) are furmshecl with sincrular projections on their anterior femora, and 0 with a great fork or pair of horns on the lower surface of the thorax. This situation seems extremely ill adapted for the display of these projections, and they rna y be of Eo me real service ; but no use can at present be- J assigned to them. It is a highly J' remarkable fact, that although the· Fig. 20. Onitis furcifel', male, males do not exhibit even a trace of viewed from beneath. f f h horns on the upper sur ace o t e-body, yet in the females a rudiment of a single horn on the head (fig. 21, a), and of a. crest (b) ~n the t~orax, are plainly visible. That the slight thoraciC crest m the Fig. 21. Left-hand figure, male of Onitis furcifer, vi,ewed laterally. Right-han~ figure, female. a. Rudiment of cephallc born. b. Trace of thoracic hom or etest. female is a rudiment of a projection proper to the male; though entirely absent in the male of this particular species, is clear : for the female of Bubas bison (a form C: JAP. X. COLEOPTERA. 373 ~.v hich comes next to Onitis) has a similar slight crest on the thorax, and the male has in the same situation a great projection. So again there can be no doubt that the little point (a) on the head of the female Onitis J~wcifer, as well of the females of two or three allied species, is a rudimentary representative of the cephalic horn, which is common to the males of so many lamellicorn beetles, as in Phanreus, fig. 17. The males indeed ()f some unnamed beetles in the British Museum, which are believed actually to belong to the genus Onitis, are furnished with a similar born. The remarkable nature of this case will be best perceived by an illustration : the Ruminant quadrupeds run parallel with the lamel. licorn beetles, in some females possessing horns as large as those of the male, in others having them much -smaller, or existing as mere rudiments (though this is as rare with ruminants as it is common with Lamelli ·corns), or in having none at all. Now if a new species of deer or sheep were discovered with the female bearing distinct rudiments of horns, whilst the head .of the male was absolutely smooth, we should have a case like that of Onitis furcifer. In this case the old belief of rudiments having been created to complete the scheme of nature is so far from holding good, that all ordinary rules are complet.ely broke~ through. The view which seems the most probable 1s that some early progenitor of Onitis acquired, like other Lamellicorns, horns on the head and thorax, .and then transferred them, in a rudimentary condition, as with so many existing species, to the female, by whom 'they have ever since been retained. The subsequent loss of. th.e horns by the ma.le may have resulted through the pnnmple of compensatiOn from the development of 'the projections on the lower surface, whilst the female l1as not been thus affected, as she is not furnished with |