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Show 422 SEXUAL SELECTION. PART II. by the males. But from the circumstance of colour being so variable, and from its having been so often modified for the sake of protection, it is extremely difficult to decide in how large a proportion of cases sexual selection has come into play. ThiR is more especially difficult in those Orders, such as the Orthoptera, Hymenoptera, and Coleoptera, in which the two sexes rarely differ much in colour ; for we are thus cut off from our best evidence of some relation between the reproduction of the species and colour. With the Coleoptera, however, as before remarked, it is in the great lamellicorn group, placed by some authors at the head of the Order, and in which we sometimes see a mutual attachment between the sexes, that we find the males of some species possessing weapons for sexual strife, others furnished with wonderful horns, many with stridulating organs, and others ornamented with splendid metallic tints. Hence it seems probable that all these characters have been gained through the same means, namely sexual selection. When we treat of Birds, \Ye shall see that they present in their secondary sexual characters the closest analogy with insects. Thus, many male birds are highly pugnacious, and some are furnished with special weapons for fighting with their rivals. They possess organs which are used during the breeding-season for producing vocal and instrumental music. They are frequently ornamented with combs, horns, wattles and plumes of the most dh·ersified kinds, and are decorated with beautiful colours, all evident} v for the sake of display. We shall find that, as with insects, both sexes, in certain groups, are equally beautiful, and are equally provided with ornaments which are usually confined to the male sex. In other groups both sexes are equally plain-coloured and unornamented. Lastly, in some few CHAP. XI. SUMMARY ON INSECTS. 423 anomalous cases, the females are more beautiful than the males. We shall often find, in the same group of birds, every gradation from no difference between the sexes to an extreme difference. In the latter case we shall' see that the females, like female insects, often possess more or less plain traces of the charact~rs whi~h properly belong to the males. The ~nalogy? mde~ed, m all these respects between birds and msects, 1s curwusly close. Whatever explanation applies to the one class probably applies to the other; an<l t?is explanatio~, as we shall hereafter attempt to shew, 1s almost certamly l1 U sexual selection. END OF VOL. I. |