234 Professor Edward B. Poulton on the 



exercised with direct reference to females, or in rivalry 

 to other males in the presence of a female. In the case 

 of Psophiis stridulus, true stridulation was only observed 

 when the close proximity of a female had evidently 

 thrown the male into a state of excitement. 



The I'ollowing considerations also support the same 

 conclusions. In Pezotettix pedestris, both sexes have 

 rudimentary wings and the male never makes any audible 

 sound. Nevertheless, when he is seated on the back of 

 the female attempting to pair, and during coitus itself, 

 he continually moves his third legs alternately as if 

 in stridulation. I believe that this movement is a vestige 

 of an ancient and long-lost power of producing sound. 

 Although stridulation is usually produced by a symmetincal 

 movement of the third legs, it will be shown that this is 

 not the case with Stenohothrus elegans. There is there- 

 fore no objection to be raised against this character of 

 the movement in Pezotettix. Another view, and that 

 held by my friend, the learned Orthopterist, Henri de 

 Saussure, is that sound is really produced, only we cannot 

 hear it. He holds that the sound is merely the outward 

 expression of the elated feelings of the male Pezotettix. 



Dv. Sharp, too, considers from the presence in 

 apparently dumb species of well-developed tympana — 

 and this is their condition in Pezotettix — "that the 

 Orthoptera provided with acoustic organs, and which we 

 consider dumb, are not really so,, but produce sounds we 

 cannot hear, and do so in some manner unknown to us ^' 

 (Cambridge Natural History, Vol. v., 287). On the 

 other hand, it may be urged that the perception of vibra- 

 tion by means of tympana may be of great value in the 

 life of an organism, even if the organism were incapable 

 of producing sounds, and that it may be retained for 

 some more general use v^'hen its original special function 

 has ceased to exist. 



But in any case this movement of Pezotettix is con- 

 ducted with an apparatus homologous with that by which 

 sound is produced in other AcridiidcT, and yet one in 

 which the special sound-producing structures are absent. 

 The tegmina are too short to be brought into their usual 

 relation with the femora, and the ridge on the inner face 

 of the latter is without the "musical beads,^^ although 

 strongly chitinized and prominent as though it had pi'e- 

 viously possessed significance in this respect. 



