352 SEXUAL SELECTION. Part II. 



soon as the first had finished his sonp\ a second im- 

 mediately began ; and after he had concluded, another 

 began, and so on. As there is so much rivalry between 

 the males, it is probable that the females not only dis- 

 cover them by the sounds emitted, but that, like female 

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

 most attractive voice. 



I have not found any well-marked cases of orna- 

 mental 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, Orthoptera. — The males in the three salta- 

 torial families belonging to this Order are remark- 

 able for their musical powers, namely the Achetidse or 

 crickets, the Locustidae for which there is no exact 

 equivalent name in English, and the Acridiidge or grass- 

 hoppers. The stridulation produced by some of the 

 Locustidae is so loud that it can be heard durino- the 

 night at the distance of a mile ; 25 and that made by 

 certain species is not unmusical even to the human 

 ear, so that the Indians on the Amazons keep them 

 in wicker ca^es. All observers agree that the sounds 

 serve either to call or excite the mute females. But it 

 has been noticed 26 that the male migratory locust of 

 Russia (one of the Acridiidae) whilst coupled with the 

 female, stridulates from anger or jealousy when ap- 

 proached by another male. The house-cricket when 

 surprised at night uses its voice to warn its fellows. 27 In 

 North America the Katy-did (Platyphyllum concavum, 



25 L. Guikling, ' Transact. Linn. Soc' vol. xv. p. 154. 



26 Koppen, as quoted in the ' Zoological Record ' for 1867, p. 46'K 



2 7 Gilbert White, ' Nat. Hist, of Seiborne,' vol. ii. 1825, p. 262. 



