29^ 



The Descent of Man. 



Paet II, 



species of ttie genus, are furnished with singular projections on 

 their anterior femora, and with a great fork or pair of horns on 

 the lower suiface of the thorax. Judging 

 from other insects, these may aid the male 

 in clinging to the female. Although the 

 males have not even a trace of a horn on 

 the upper surface of the body, yet the fe- 

 males plainly exhibit a rudiment of a single 

 horn on the head (fig. 22, a), and of a crest 

 (J) on the thorax. That the slight thoracic 

 f « yo crest in the female is a rudiment of a pro- 



T^ f » jection proper to the male, though entirely 



absent in the male of this particular species, 

 is clear: for the female of Bubas hison (a 

 genus which comes next to Onitis) has a 

 similar slight crest on the thorax, and the male bears a great 

 projection in the same situation. So, again, there can hardly be 

 a doubt that the little point (a) on the head of the female Onitis 



Fig 21. Onitis furcifer, 

 male viewed from be- 

 neatll. 



..-^ 



Fig. 22. Left-hand figure, male of Onitis furcifer, viewed laterally. Right-hand 

 hgure, female, a. Rudiment of cephalic horn. b. Tr.ace of thoracic horn or crest. 



furcifer, as well as on the head of the females of two or three 

 allied species, is a rudimentary representative of the cephalic 

 horn, which is common to the males of so many Lamellicorn 

 beetles, as in Pharseus (fig. 18). 



'the old belief that rudiments have been created to complete 

 the scheme of nature is here so far from holding good, that we 

 nave a complete inversion of the ordinary state of things in the 

 family. We may reasonably suspect that the males originally 

 bore horns and transferred them to the females in a rudimentary 

 condition, as in so many other Lamellicorns. Why the males 

 subsequently lost their horns, we know not ; but this may have 

 been caused through the principle of compensation, owing to 

 the development of the large horns and projections on the lower 

 surface ; and as these are confined to the males, the rudiments 

 of the upper horns on the females would not have been thus 

 obliterated. 



