SINGING AND HEARING IN AEROTEGMINA KILIMANDJARICA (TETTIGONIIDAE: HEXACENTRINAE), A SPECIES WITH UNUSUAL LOW CARRIER FREQUENCY OF THE CALLING SONG

摘要

The carrier frequency of the calling songs of bush-crickets (Tettigonioidea) is generally negatively correlated with body size; the smaller the species, the higher the frequency. However, in the correlation between body size and frequency there is a large variation. Some species do not seem to follow the main trend, but the reason(s) for the deviations from the negative correlation are largely unknown. Especially interesting are species which produce sounds "too" low for their size because this requires special and – judging from the other species – probably expensive modifications of the tegmina. Here we present data on the signal and the acoustic behaviour of Aerotegmina kilimandjarica, a small species with extraordinarily enlarged and inflated tegmina. The calling song has its peak frequency at 5 kHz (bandwidth 10 dB below peak 4-10 kHz). The species has a typical tettigoniid hearing curve, being most sensitive at 10 kHz (threshold 45 dB SPL). Taking into account the atmospheric attenuation, the song (loudness 100 dB SPL at 1 m) has a greater range at 5 kHz than at 10 kHz, so that maximising the range may have been one reason for the use of this unusually low frequency.