RELIABLE ACOUSTIC CUES FOR FEMALE MATE PREFERENCE IN A KATYDID (SCUDDERIA-CURVICAUDA, ORTHOPTERA, TETTIGONIIDAE)

The call of male Scudderia curvicauda (Orthoptera: Tettigoniidae) cons ists of a series of phrases, and each phrase contains syllables. Femal es respond to the male signal with ticks that follow male phrases afte r a specific period of time. Pair formation takes place after males lo cate the female using her response sounds. Repeated recordings of male s revealed that the average number of syllables produced per phrase wa s a stable, within-male parameter and that this parameter was a reliab le predictor of male size (pronotum length). Thus, phrase length could be a reliable cue by which females evaluate males. We presented virgi n females with a sequential choice of two tape-recorded male calls tha t differed only in the mean number of syllables produced per phrase. T wo different playback tapes were used, and each female was tested on e ach of 5 consecutive days with the same playback tape. Females respond ed more often and with a greater number of ticks to calls containing m ore syllables per phrase, and this preference was maintained throughou t the testing period. Male size was a poor predictor of the size of th e spermatophore food-gift produced by the male; therefore, females are probably not selecting males for this attribute. For one of the playb ack tapes, there was a significant increase in female responsiveness o ver several playback trials, suggesting that females may employ a fall ing-threshold tactic with respect to mate preference.