294 tkjS descent of man. 



as stags, rhinoceroses, &c., and are «(ronderful both from their 

 size and diverrified shapes. Instead of describing them, I have 

 given figures of the males and females of some of the more re- 

 markable forms. (Pigs. 16 to 20.) The females generally ex- 

 hibit rudiments of the horns in the form of small knobs or ridges; 

 but some are destitute of even the slightest rudiment. On the 

 other hand, the horns are nearly as well developed in the female 

 as in the male of Phanseus 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 char- 

 acteristic differences 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 ex- 

 cessive 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 the females. Mr. 

 Walsh" found that in Phanasus carnifex the horns were thrice as 

 long In some males as in others. Mr. Bates, after examining 

 above a hundred males of Onthophagus rangifer (fig. 20), thought 

 that he had at last discovered a species in which the horns did 

 not vary; but further research proved the contrary. 



The extraordinary size of the horns, and their widely different 

 structure in closely-allied forms, indicate that they have been 

 formed for some purpose; but their excessive variability in the 

 males of the same species leads to the inference that this purpose 

 cannot be of a definite nature. The horns do not show marks of 

 friction, as if used for any ordinary work. Some authors sup- 

 pose"' that as the males wander about much more than the fe- 

 males, they require horns as a defense against their enemies; but 

 a,s the horns are often blunt, they do not seem well adapted for 

 defense. The most obvious conjecture is that they are used by 

 the males for fighting together; but the males have never been 

 observed to fight; nor could Mr. Bates, after a careful exam- 

 ination of numerous species, find any sufficient evidence, in their 

 mutilated or broken condition, of their having been thus used. 

 If the males had been habitual fighters, the size of their bodies 

 would probably have been increased through sexual selection, 

 so as to have exceeded that of the females; but Mr. Bates, after 

 comparing the two sexes in above a hundred species of the 

 Copridae, did not find any marked difference in this respect 

 amongst well-developed individuals. In Lethrus, moreover, a bee- 



«* 'Proc. Entomolog. Soc. of Philadelphia,' 1864, p. 228. 



"" Kirby and iSpence, 'Introduot. Entomolog.' vol. iii. p. 300. 



