288 Tlie Descent of Man. Pa rt II. 



distended with air, like a great pellucid bladder, so as to 

 increase the resonance. Mr. Trimen informs me that at the 

 Gape 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 shewn that both 

 sexes of Ephippiger vitium are thus provided; though the organs 

 differ in the male and female 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 rudiments on the under surface of the 

 wing-covers of the female Achetidse, and on the femora of the 

 female Acridiidse. In the Homoptera, also, the females have the 

 proper musical apparatus in a functionless state ; and we shall 

 hereafter meet in other divisions of the animal kingdom with 

 many instances of structures proper to the male being present 

 in a rudimentary condition in the female. 



Landois has observed another important 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 during the larval state in both sexes. In the 

 males, on the other hand, they become further 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 extremely 

 diversified, and are altogether different from those employed by 

 the Homoptera. 43 But throughout the animal kingdom we 

 often find the same object gained by the most diversified means ; 

 this seems due to the whole organisation having undergone mul- 

 tifarious changes in the course of ages, and as part after part 

 varied different variations were taken advantage of for the 

 same general purpose. The diversity of means for producing 

 Bound in the three families of the Orthoptera and in the 



** Landois has recently found in moptera ; and this is a surprising 



certain Orthoptera rudimentary fact. See ' Zeitschr. fur wissensch. 



structures closely similar to the Zoolog.' B xyii. Heft 3, 1871, p. 



sound-producing organs in the Ho- 348. 



