340 SEXUAL SELECTION. [Part IL 



and, in the case of Pirates stridulus, this is said 21 to he 

 effected by the movement of the neck within the pro- 

 thoracic cavity. According to Westring, Reduvius per- 

 sonatus also stridulates. But I have not been able to 

 learn any particulars about these insects ; nor have I any 

 reason to suppose that they differ sexually in this respect. 



Order, Homoptera. — Every one who has wandered in 

 a tropical forest must have been astonished at the din 

 made by the male Cicadas. The females are mute ; as the 

 Grecian poet Xenarchus says, " Happy the Cicadas live, 

 since they all have voiceless wives." The noise thus made 

 could be plainly heard on board the "Beagle," when 

 anchored at a quarter of a mile from the shore of Brazil ; 

 and Captain Hancock says it can be heard at the distance 

 of a mile. The Greeks formerly kept, and the Chinese 

 now keep, these insects in cages for the sake of their song, 

 so that it must be pleasing to the ears. of some- men." 

 The Cicadidas usually sing during the day ; while the 

 Fulgoridse appear to be night-songsters. The sound, ac- 

 cording to Landois, 23 who has recently studied the subject, 

 is produced by the vibration of the lips of the spiracles, 

 which are set into motion by a current of air emitted from 

 ,the tracheae. It is increased by a wonderfully complex 

 resounding apparatus, consisting of two cavities covered 

 by scales. Hence the sound may truly be called a voice. 

 In the female the musical apparatus is present^ but very 

 much less developed than in the male, and is never used 

 for producing sound. 



With respect to the object of the music, Dr. Hartman, 



31 Westwood, ' Modern Class, of Insects,' vol. ii. p. 473. 



22 These particulars are taken from Westwood's ' Modern Class, of 

 Insects,' vol. ii. 1840, p. 422. See, also, on the Fulgoridse, Kirby and 

 Spence, ' Introduct.' vol. ii. p. 401. 



23 « Zeitschrift fur wissenschaft. Zoolog.' B. xvii. 1867, 8. 152-158. 



