SEX-SPECIFIC SPECTRAL TUNING FOR THE PARTNERS SONG IN THE DUETTING BUSH-CRICKET ANCISTRURA-NIGROVITTATA (ORTHOPTERA, PHANEROPTERIDAE)

The song of the male bushcricket Ancistrura nigrovittata consists of a sequence of verses. Each verse comprises a syllable group, plus, afte r about 400 ms a single syllable serving as a trigger for the female r e sponse song. The carrier frequency of the male song spectrum peaks a t around 15 kHz, while the female song peaks at around 27 kHz. The thr esholds of female responses to models of male songs are lowest for son g frequencies between 12 and 16 kHz and therefore correspend to the ma le song spectrum. The threshold curve of the female response to the tr igger syllable at different frequencies has the same shape as the tuni ng for the syl lable group. Phonotactic thresholds of male Ancistrura nigrovittata to synthetic female responses at different frequencies ar e lowest between 24 and 28 KHz and thereby correspond to the female so ng spectrum and clearly differ from female response thresholds. Activi ty of the tympanic fibre bundle of both sexes is most sensitive betwee n 15 and 35 kHz and therefore not specifically tuned to the partner's song. Individual behavioural thresholds have their minimum within 10 d B of the values of tympanic thresholds.