Chap. X.] COLEOPTERA. 359 



erally exhibit rudiments of the horns in the form of small 

 knobs or ridges ; but some are destitute of even a rudi- 

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

 developed in the female as in thfc male of JPhanceus Ian- 

 cifer; and only a little less well developed in the females 

 of some other species of the same genus and of Copris. 

 In the several subdivisions of the family, the differences 

 in structure of the horns do not run parallel, as I am in- 

 formed 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 distinguished 

 from the females. Mr. Walsh 69 found that in Phanmus 

 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. 19), 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 important 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 fric- 

 tion, as if used for any ordinary work. Some authors 

 suppose 60 that as the males wander much more than the 

 females, they require horns as a defence against their 

 enemies ; but in many cases the horns do not seem well 

 adapted for defence, as they are not sharp. The most 



59 'Proa Entomolog. Soc. of Philadelphia,' 1864, p. 228. 



60 Kirby and Spence, ' Introduct. Entomolog.' vol. iii. p. 300. 



