370 SEXUAL SELECTION. Part II. 



A most remarkable distinction between the sexes of 

 many beetles is presented by the great horns which 

 rise from the head, thorax, or clypeus of the males ; 

 and in some few cases from the under surface of the 

 body. These horns, in the great family of the Lamelli- 

 corns, resemble those of various quadrupeds, such as 

 stags, rhinoceroses, &c, 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. 15 to 1 9.) 

 The females generally exhibit rudiments of the horns 

 in the form of small knobs or ridges; but some are 

 destitute of even a rudiment. On the other hand, the 

 horns are nearly as well developed in the female as in 

 the male of Phanseus Jancifer ; and only a little less 

 well developed in the females of some other species of 

 the same genus and of Copris. In the several sub- 

 divisions of the family, the differences in structure of 

 the horns do not run parallel, as I am informed by 

 Mr. Bates, with their more important and characteristic 

 differences ; thus within the same natural section of the 

 genus Onthophagus, there are species which have either 

 a single cephalic horn, or two distinct horns. 



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 distin- 

 guished from the females. Mr Walsh 59 found that in 

 Phaneeus camifex the horns were thrice as long in some 

 males as in others. Mr. Bates, after examining above 

 a hundred males of Onthophagus rangifer (fig. 19), 

 thought that he had at last discovered a species in 



39 'Proc. Entomolog. Soc. of Philadelphia,' 1864, p. 228. 



