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. This is more 

 especially difficult in those Orders, such as the Orthop- 

 tera, 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, we shall see that they pre- 

 sent 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 diversified kinds, and are decorated 

 with beautiful colours, all evidentlv for the sake of dis- 

 play. 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 



