340 SEXUAL SELECTION. [Part I L 



and, in tlie case of Pirates stridulus^ this is said " to be 

 effected by the movement of the neck within the pro- 

 thoracic cavity. According to Westring, Heduvius per- 

 so?iatus 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 Cicadae. The females ai-e 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 Cicadidje usually sing during the day; while the 

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

 cording to Landois,"' 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, 



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



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

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

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



" 'Zeitschrift fur wissenschaft. Zoolog.' B. xvii. 1867, s. 152-158. 



