Chap. X. 



Orthoptera. 



2S5 



" of dome over the wing-covers, and which has probably the 

 " effect of increasing the sound." 37 



Kg. 13. Chloroccelus Xanana (from Bates), a, b. Lobes of opposite wing-covers. 



We thus see that the musical apparatus is more differentiated 

 or specialised in the Locustidaa (which include, I believe, the 

 most powerful performers in the Order), than in the Achetidse, 

 in which both wing-covers have the same structure and the 

 same function. 38 Landois, however, detected in one of the 

 Locustidre, namely in Decticus, a short and narrow row of small 

 teeth, mere rudiments, on the inferior surface of the right wing- 

 cover, which underlies the other and is never used as the bow. 

 I observed the same rudimentary structure on the under side of 

 the right wing-cover in Phasgonura viridissima. Hence we may 

 infer with confidence that the Locustida; are descended from a 

 form, in which, as in the existing AchetidaB, both wing-covers 

 had serrated nervures on the under surface, and could be 

 indifferently used as the bow ; but that in the Locustidse the 

 two wing-covers gradually became differentiated and perfected, 



27 Westvvood, 'Modern Class, of Insects,' vol. i. p. 453. 



38 Landois, ' Zeitsch. f. wiss. Zoolog.' B. xvii. 1867, s. 121, 122. 



