3G0 SEXUAL SELECTION. [Part IL 



obvious conjecture is that they are used by the males for 



fighting togetlicr ; 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 

 mutihited or broken condition, of their having been thus 

 used. If the males had been habitual fighters, their size 

 v/ould probably have been increased through sexual selec- 

 tion, so as to have exceeded that of the female ; but Mr. 

 Bates, after comparing the two sexes in above a hundred 

 species of the Copridoe, does not find in well-developed in- 

 dividuals any marked diflerence in this respect. There is, 

 moreover, one beetle, belonging to the same great divis- 

 ion 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 devel- 

 oped — as shown by their extreme variability in the same 

 species and by their extreme diversity in closely-allied 

 species — is that tliey have been acquired as ornaments. 

 This view will at first appear extremely 

 improbable; but we shall hereafter find 

 with many animals, standing much higher 

 in the scale, namely, fishes, amphibians, 

 reptiles, and birds, that various kinds of 

 crests, knobs, horns, and combs, have 

 been developed apparently for this sole 

 purpose. 

 Fig. 20. — Onitis fur- The malcs of Onitis furcifer (fig. 20) 



cifer, male, viewed r -i ^ '.i • 'i ' • „t.i „ 



from beneath. 'ii'c lumished With SHigular projections 



on their anterior femora, and with a great 



fork or pair of horns on the lower surface of the thorax. 



This situation seems extremely ill-adapted for the display 



of these projections, and they may be of some real service ; 



