FUNCTIONAL-MORPHOLOGY OF BUSH-CRICKET EARS - COMPARISON BETWEEN 2 SPECIES BELONGING TO THE PHANEROPTERINAE AND DECTICINAE (INSECTA, ENSIFERA)

The morphology of the complex tibial organs in the forelegs of two bus hcricket species belonging to the Phaneropterinae and Decticinae (Tett igoniidae) is described comparatively. In both species the tibial orga ns are made up of the subgenual organ, the intermediate organ and the crista acustica; the latter are parts of the tympanal organs and serve as auditory receptors. The very thin tympana in the forelegs of Pholi doptera griseoaptera (Decticinae) are protected by tympanal covers whe reas in Leptophyes punctatissima (Phaneropterinae) the tympana are thi cker and fully exposed. The overall auditory sensitivity of L. punctat issima is lower and the sensitivity maximum of the hearing threshold l ies at higher frequencies compared to P. griseoaptera. The number of s colopidia in the three scolopale organs and the dimensions of parts of the sound conducting system differs in the two species. In the crista acustica of L. punctatissima a higher number of scolopidia is distrib uted in a smaller range than in P. griseoaptera; the scolopidia are es pecially concentrated in the distal part. Morphometrical analyses indi cate that the dimensions of the spiracles, the acoustic trachea and th e tympana determine the overall auditory sensitivity and that the arra ngement of the scolopidia and the dimensions of structures in the cris ta acustica affect the frequency tuning of the hearing threshold.