282 The Descent of Man. Part II. 



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

 are set into motion by a current of air emitted from the trachese ; 

 but this view has lately been disputed. Dr. Powell appears to 

 have proved 23 that it is produced by the vibration of a mem- 

 brane, set into action by a special muscle. In the living insect, 

 whilst stridulating, this membrane can be seen to vibrate ; and 

 in the dead insect the proper sound is heard, if the muscle, 

 when a little dried and hardened, is pulled with the point of a 

 pin. In the female the whole complex musical apparatus is 

 present, but is much less developed than in the male, and is 

 never used for producing sound. 



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

 speaking of the Cicada septemdecim, of the United States, says, 2S 

 " the drums are now (June 6th and 7th, 1851) heard in all 

 ". directions. This I believe to be the marital summons from 

 " the males. Standing in thick chestnut sprouts about as high 

 ",, as my head, where hundreds were around me, I observed the 

 " females coming around the drumming males." He adds, " this 

 " season (Aug. 1868) a dwarf pear-tree in my garden produced 

 " about fifty larvse of Cic. pruinosa ; and 1 several times noticed 

 " the females to alight near a male while he was uttering his 

 " clanging notes." Fritz Miiller writes to me from S. Brazil 

 that he has often listened to a musical contest between two or 

 three males of a species with a particularly loud voice, seated 

 at a considerable distance from each other : as soon as one had 

 finished his song, another immediately began, and then another. 

 As there is so much rivalry between the males, it is probable 

 that the females not only find them by their sounds, but that, 

 like female birds, they are excited or allured by the male with 

 the most attractive voice. 



I have not heard of any well-marked cases of ornamental 

 differences between the sexes of the Homoptera. Mr. Douglas 

 informs me that there are three British species, in which the 

 male is black or marked with black bands, whilst the females are 

 pale-coloured or obscure. 



Order, Ortlwptera (Crickets and Grasshoppers). — The males in 

 the three saltatorial families in this Order are remarkable for 

 their musical powers, namely the Achetidse or crickets, the 

 Locustidse for which there is no equivalent English name, and the 

 Acridiidse or grasshoppers. The stridulation produced by some 



25 'Transact. New Zealand In- from a 'Journal of the Doings of 

 stitute,' vol. v. 1873, p. 283. Cicada septemdecim ' by Dr. Hart 



26 I am indebted to Mr. WaLh man. 

 for hanng smt me this extract 



