878 TSE DESCENT OF MAN 



male the wliole body has been converted into a musical 

 instrument, being distended with air, like a great pellucid 

 bladder, so as to increase the resonance. Mr. Trimen in- 

 forms me that at the Cape of Good Hope these insects make 

 a wonderful noise during the night. 



In the three foregoing families the females are almost 

 always destitute of an efficient musical apparatus. But 

 there are a few exceptions to this rule, for Dr. Gruber 

 has shown that both sexes of Ephippiger vitium are thus 

 provided, though the organs differ in the male and fe- 

 male to a certain extent. Hence we cannot suppose that 

 they have been transferred from the male to the female, as 

 appears to have been the case with the secondary sexual 

 characters of many other animals. They must have been 

 independently developed in the two sexes, which no doubt 

 mutually call to each other during the season of love. 

 In most other Locustidse (but not according to Landois 

 in Decticus) the females have rudiments of the stridulatory 

 organs proper to the male, from whom it is probable that 

 these have been transferred. Landois also found such rudi- 

 ments on the under surface of the wing-covers of the female 

 Achetidse, and on the femora of the female Acridiidae. In 

 the Homoptera, also, the females have the proper musical 

 apparatus in a functionless state; aa'd we shall hereafter 

 meet in other divisions of the animal kingdom with many 

 instances of structures proper to the male being present in 

 a rudimenta. y condition in the female. 



Landois has observed another important fact, namely, 

 that in the females of the AcridiidiB, the stridulating teeth 

 on the femora remain, throughout life in the same condition 

 in which they first appear during the larval state in both 

 sexes. In the males, on the other hand, they become fur- 

 ther developed, and acquire their perfect structure at the 

 last moult, when the insect is mature and ready to breed. 



From the facts now given, we see that the means by 

 which the males of the Orthoptera produce their sounds 

 are extrem 5ly diversified, and are altogether different from 



