'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 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 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. Entomology vol. iii. p. 300. 
2 B 2 
