Further Investigations into the Function of the “Mirror” in Tettigonioidea (Orthoptera)

Abstract

FROM the calculations of Pierce¹ nearly two decades ago, students of the production of sound in bush crickets have assumed the area of thin cuticle on the right tegmen known as the “mirror” to be acoustically important² (Fig. 1). Pierce's attribution of a resonant function to this membrane was challenged by Broughton³ and Dumortier⁴. Dumortier suggested that the whole tegmen is responsible as an acoustic coupler, not only the mirror. Broughton, working on the decticine, Metrioptera roeselii (Hagenbach), found that the frequency spectrum of one individual was not obligatorily changed by coating the mirror with a deadening film of latex. His results have stimulated further work of the same nature on two members of the Conocephalidae, Conocephalus discolor (Thunberg) and Homorocoryphus nitidulus nitidulus (Scopoli). Both these animals, like M. roeselii, have a well-defined spectrum, but their peak frequencies are at 28 kc/s and 15.5 kc/s, respectively.