348 SEXUAL SELECTION. [Pakt II. 



into a musical instrument, being distended with air, like a 

 great pellucid bladder, so as to increase the resonance. 

 Mr. Trimen informs me that at the Cape of Good Hope 

 these insects make a wonderful noise during the night. 



There is one exception to the rule that the females in 

 these three Families are destitute of an efficient musical 

 apparatus ; for both sexes of Ephippiger (Locustida?) are 

 said 40 to be thus provided. This case may be compared 

 with that of the reindeer, in which species alone both 

 sexes possess horns. Although the female orthoptera are 

 thus almost invariably mute, yet Landois 41 found rudi- 

 ments of the stridulating organs on the femora of the fe- 

 male AcridiidaB, and similar rudiments on the under sur- 

 face of the wing-covers of the female Achetidae ; but he 

 failed to find any rudiments in the females of Decticus, 

 one of the Locustidae. In the Homoptera, the mute fe- 

 males of Cicada have the proper musical apparatus in an 

 undeveloped state ; and we shall hereafter meet, in other 

 divisions of the animal kingdom, with innumerable in- 

 stances of structures proper to the male being present in 

 a rudimentary condition in the female. Such cases appear 

 at first sight to indicate that both sexes were primordially 

 constructed in the same manner, but that certain organs 

 were subsequently lost by the females. It is, however, a 

 more probable view, as previously explained, that the or- 

 gans in question were acquired by the males and partially 

 transferred to the females. 



Landois has observed another interesting fact, namely, 

 that, in the females of the Acridiidse, the stridulating teeth 

 on the femora remain throughout life in the same condition 

 in which they first appear in both sexes during the larval 

 state. In the males, on the other hand, they become 

 fully developed and acquire their perfect structure at 



^•Westwood, ibid. vol. i. p. 453. 



« Landois, ibid. s. 115, 116, 120, 122. 



