Frequency tuning and directional sensitivity of tympanal vibrations in the field cricket Gryllus bimaculatus

Female field crickets use phonotaxis to locate males by their calling song. Male song production and female behavioural sensitivity form a pair of matched frequency filters, which in Gryllus bimaculatus are tuned to a frequency of about 4.7 kHz. Directional sensitivity is supported by an elaborate system of acoustic tracheae, which make the ears function as pressure difference receivers. As a result, phase differences between left and right sound inputs are transformed into vibration amplitude differences. Here we critically tested the hypothesis that acoustic properties of internal transmissions play a major role in tuning directional sensitivity to the calling song frequency, by measuring tympanal vibrations as a function of sound direction and frequency. Rather than sharp frequency tuning of directional sensitivity corresponding to the calling song, we found broad frequency tuning, with optima shifted to higher frequencies. These findings agree with predictions from a vector summatio...