INSECTS. 



323 



the wing-covers, and which has probably the effect of 

 increasing the sound."* 



We thus see that the musical apparatus is more dif- 

 ferentiated or specialized in the Locustidae (which 

 include, I believe, the most powerful performers in 



Fig. 18. Chlorocoelus Tanana (from Bates), a, 5. Lobes of opposite wing-covers. 



the order), and in the Achetidae, in which both wing- 

 covers have the same structure and the same function.! 

 Landois, however, detected in one of the Locustidae, 

 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 Phasffonura viridissima. Hence we may infer 

 with confidence that the Locustidae are descended from a 

 form in which, as in the existing Achetidae, both wing- 



*Westwood, "Modern Class, of Insects," vol. i, p. 453 



f Landois, " Zeitsch. f. wiss Zoolog." B. xvii, 1867, ss. 121, 123. 



