SEXUAL SELECTION 387 



duller tlian tlie females, the latter being colored of a more 

 or less splendid golden green. On the other hand, in one 

 species the male is golden green, the female being richly 

 tinted with red and purple. In the genus Esmeralda the 

 sexes differ so greatly in color that they have been ranked 

 as distinct species; in one species both are of a beautiful 

 shining green, but the male has a red thorax. On the 

 whole, as far as I could judge, the females of those Prio- 

 nidse in which the sexes differ are colored more richly than 

 the males, and this does not accord with the common rule 

 in regard to color, when acquired through sexual selection. 



A most remarkable distinction between the sexes of 

 many beetles is presented by the great horns which rise 

 from the head, thorax, and clypeus of the males; and in 

 some few cases from the under surface of the body. These 

 horns, in the great family of the Lamellicorns, resemble 

 those of various quadrupeds, such as stags, rhinoceroses, 

 etc. , and are wonderful both from their size and diversified 

 shapes. Instead of describing them, I have given figures 

 of the males and females of some of the more remarkable 

 forms (Figs. 16 to 20). The females generally exhibit 

 rudiments of the horns in the form of small knobs or 

 ridges; but some are destitute of even the slightest rudi- 

 ment. On the other hand, the horns are nearly as well 

 developed in the female as in the male of Phanceus lancifer, 

 and only a little less well developed in the females of some 

 other species of this genus and of Copris. I am informed 

 by Mr. Bates that the horns do not differ in any manner 

 corresponding with the more important characteristic differ- 

 ences between the several subdivisions of the family; thus 

 within the same section of the genus Onthophagus there 

 are species which have a single horn, and others which 

 have two. 



In almost all cases the horns are remarkable from their 

 excessive variability; so that a graduated series can be 

 formed from the most highly developed males to others 

 so degenerate that they can barely be distinguished from 



