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SEXUAL DIMORPHISM 



way as to be opposed to each other, they are not articulated 

 but rigidly connected with those parts of the body. But the 

 head and prothorax themselves are movable, and thus the 

 horns can be moved about like the limbs of a pair of tongs. 

 Entomologists are still unable to assign a definite use to 

 these excrescences. It is stated that they are but little used 

 for fighting. According to Mr. David Sharp, in the Cambridge 



Fig. 24. Xylotrupes Gideon : a common beetle in India and the Malay Archipelago. 

 A, male ; B, female. 



Natural History, Baron von Hiigel saw the males of Xylotrupes 

 Gideon in Java sometimes carrying the females by means of 

 their horns; but Mr. Sharp considers this must be an 

 exceptional case, because in the majority of species the shape 

 of the horns makes such an employment of them impossible. 

 Whether the excrescences are useful or not, it seems to me 

 that their resemblance to similar unisexual developments in 

 other families indicates that they have been produced by 

 mechanical irritation, by blows of some kind ; and as so 



