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 r 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 19.) 
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 Phanmus lancifer ; 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 
Phanxus earnifex 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 
59 < Proc. Entomolog. Soc. of Philadelphia,’ 1864, p. 228. 
