352 
SEXUAL SELECTION. 
Paut II. 
soon as the first had finished his song, 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 Achetidae or 
crickets, the Locustidae for which there is no exact 
equivalent name in English, and the Acridiidae or grass- 
hoppers. The stridulation produced by some of the 
Locustidae is so loud that it can be heard during 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 cages. 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 
Bussia (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. Guilding, ‘ Transact. Linn. Soc.’ vol. xv. p. 154. 
26 Koppen, as quoted in the 6 Zoological Kecord,’ for 1867, p. 460. 
27 Gilbert White, ‘ Nat. Hist, of Selborne,’ vol. ii. 1825, p. 262. 
