122 L November, 



if in Acridiidce, Lepidoptera, and CicadidcB (?), we should find at tlie 

 base of the abdomen structures suited to hearing, and which in the 

 LocHstina and GryUidcB have a counterpart on the fore tibiae. 



The Glcadidce challenge and reply to each other when they are at 

 a distance apart ; and, considering the low pitch of their notes, this 

 action would accord with an auditory adit of considerable dimension. 

 The females also alight near the musical males. Now the corresponding 

 cavities at the base of the abdomen, placed ventrally, and closed 

 inwardly by a membrane, posteriorly tense and iridescent, and 

 anteriorly soft, answer structurally the requirements of an external 

 ear, by intermittent exposure in the males to atmospheric impressions 

 by the action accompanying their music. These cavities, although 

 having a considerably greater development in the male, are similar in 

 the female sex, and seem to correspond to the other auditory structures 

 I shall notice. 



Regarding the counterpart of this organ in the Acridiidce 

 {Ortlioptera), more is known, thanks to the researches of Goureau, 

 Miiller, and Siebold. In this there is evidently a cavity, with an ovate, 

 lunate, or linear opening ; situated at the hinder lateral portion of 

 the first dorsal arc of the abdomen, partially covered by the wings. 

 This cavity is closed interiorly by an iridescent, thin, and oval mem- 

 brane (membrana tympanica), which parts it from the first abdominal 

 air-bladder. On its disc, certain brown punctate discolorations are 

 Been, which mark the position of two raised chitinous pieces on its 

 internal surface : the larfjer angfular, the other small and triangular. 

 To the more projecting angular piece is attached a snow-white vesicle, 

 distended with a clear fluid (membranous labyrinth), that also sends 

 off a thin arm, inserted in the smaller piece situated towards the 

 centre of the disc. The tender vesicle again is surrounded with the 

 ramifications of a nerve (representing the acoustic), proceeding from 

 the third thoracic ganglion. And lastly, in the horny setting that 

 surrounds the iridescent membrane, where it dilates anteriorly and 

 inferiorly, is a minute round or oval opening, forming a communication 

 between the air-bladder and external air ; adapted to the part of an 

 Eustachian tube, by introducing air immediately behind the membrane 

 (Von Siebold, Erichson's Archiv fiir Natui-gesch., 1S44, pp. 52—81). 

 A readier proof of the function of this organ may be gathered by 

 observation than comparison. If any one will watch the grasshoppers 

 in the meadows it will be noticed how the male, on the conclusion of 

 his music, lowers one or both femora horizontally, retaining the elytra 

 somewhat raised, and thus exposing their membrane until he receives 

 a response : or how, when he seeks to jdlure the female, he places 



