Chap. X. COLEOPTERA. 371 



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 friction, as if used for any ordinary work. Some 

 authors suppose r, ° 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 obvious conjecture is that they are 

 used by the males for fighting together ; but they 

 have never been observed to fight ; nor could Mr. Bates, 

 after a careful examination 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, their size would probably 

 have been increased through sexual selection, so as to 

 have exceeded that of the female ; but Mr. Bates, after 

 comparing the two sexes in above a hundred species of 

 the Copridse, does not find in well-developed individuals 

 any marked difference in this respect. There is, more- 

 over, one beetle, belonging to the same great division 

 of the Lamellicorns, namely Lethrus, the males of which 

 are known to fight, but they are not provided with 

 horns, though their mandibles are much larger than 

 those of the female. 



The conclusion, which best agrees with the fact of 

 the horns having been so immensely yet not fixedly 

 developed, — as shewn by their extreme variability in 



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



2 b 2 



