INSECTS. 



341 



Sexual selection, which implies the possession of con- 

 siderable perceptive powers and of strong passions, seems to 

 have been more effective with the 

 Lamellicorns than with any other 

 family of beetles. With some species 

 the males are provided with weapons 

 for fighting; some live in pairs and 

 show mutual affection; many have 

 the power of stridulating when ex- 

 cited; many are furnished with the 

 most extraordinary horns, apparently 

 for the sake of ornament; and some, 

 which are diurnal in their habits, are 

 gorgeously colored. Lastly, several 

 of the largest beetles in the world 

 belong to this family, which was 

 placed by Linnaeus and Fabricius at 

 the head of the order. * 



Stridulating Organs. Beetles be- 

 longing to many and widely distinct 

 families possess these organs. The 

 sound thus produced can sometimes 

 be heard at the distance of several 

 feet or even yards, \ but it is not r 

 comparable with that made by the J* 

 Orthoptera. The rasp generally con- 

 sists of a narrow, slightly raised sur- 

 face, crossed by very fine, parallel 

 ribs, sometimes so fine as to cause 

 iridescent colorc, and having a very 

 elegant appearance under the micro- 

 scope. In some cases, as with Ty- 

 phoeus, minute, bristly or scale-like 

 prominences, with which the whole 

 surrounding surface is covered in 

 approximately parallel lines, could 

 be traced passing into the ribs of the Fig. 24. chiasognathus Gran- 

 rasp. The transition takes place 



* Westwood, " Modern Class.," vol. i, p. 184. 

 fWollaston, "On Certain Musical CurculiouidaB," 

 Mag. of Nat. Hist.," vol. vi, 1860, p, 14. 



Annals and 



