. The descent of man, and selection in relation to sex. Evolution (Biology); Sexual selection in animals; Sexual dimorphism (Animals); Sex differences; Human beings -- Origin. 360 SEXUAL SELECTION. [Part II. obvious conjecture is that they are used by the males for fighting together; but they have never been observed to fight; nor could Mr. Bates, after a careful examination of numerous species, find any sufficient evidence, in their mutilated or broken condition, of their having been thus used. If the males had been habitual fighters, their size would probably have been increased through sexu
. The descent of man, and selection in relation to sex. Evolution (Biology); Sexual selection in animals; Sexual dimorphism (Animals); Sex differences; Human beings -- Origin. 360 SEXUAL SELECTION. [Part II. obvious conjecture is that they are used by the males for fighting together; but they have never been observed to fight; nor could Mr. Bates, after a careful examination of numerous species, find any sufficient evidence, in their mutilated or broken condition, of their having been thus used. If the males had been habitual fighters, their size would probably have been increased through sexual selec- tion, so as to have exceeded that of the female; but Mr. Bates, after comparing the two sexes in above a hundred species of the Copridae, does not find in well-developed in- dividuals any marked difference in this respect. There is, moreover, one beetle, belonging to the same great divis- ion of the Lamellicorns, namely, Lethrus, the males of which are known to fight, but they are not provided with horns, though their mandibles are much larger than those of the female. The conclusion, which best agrees with the fact of the horns having been so immensely yet not fixedly devel- oped—as shown by their extreme variability in the same species and by their extreme diversity in closely-allied species—is that they have been acquired as ornaments. 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. Fig. 20. — Onitis fur- The males of Onitis furcifer (fig. 20) cifer, male, viewed r • i j ' • i ~i~„4-:~^~ from beneath. are furnished with singular projections on their anterior femora, and 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 p
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectevoluti, bookyear1872
