SG6 



SEXUAL SELECTION. 



[Part II. 



with any other family of theColeoptera or beetles. With 



some species the males are provided 

 with weapons for lighting ; some live 

 in pairs and show mutual affection • 

 many have the power of stridulating 

 when excited; many are furnished 

 with the most extraordinary horns, 

 apparently for the sake of ornament ; 

 some which are diurnal in their hab- 

 its are gorgeously colored ; and, last- 

 ly, several of the largest beetles in 

 the world belong to this family, which 

 was placed by Linnaeus and Fabri- 

 cius at the head of the Order of the 

 Coleoptera. 67 



Fig. 23. — Chiasoenathus 

 grant ii, reduced 

 figure, male ; lower figure, 

 female. 



Stridulating organs. — Beetles 

 belonging to many and widely-dis- 

 tinct families possess these organs. 

 The sound can sometimes be heard 

 at the distance of several feet or even 

 yards, 68 but is not comparable with 

 that produced by the Orthoptera. 

 The part which may be called the 

 rasp generally consists of a narrow 

 slightly-raised surface, crossed by 

 very fine, parallel ribs, sometimes so 

 fine as to cause iridescent colors, and 

 having a very elegant appearance 

 under the microscope. In some cases, 

 Upper for instance, with Typhceus, it could 

 be plainly seen that extremely mi- 



67 Westwood, ' Modern Class.' vol. i. p. 184. 



es Wollaston, On certain musical Curculionidae, ' Annals and Mag. of 

 Nat. Hist.' vol. vi. 1860, p. 14. 



