Phonotactic preferences of female meadow katydids (Orthoptera: Tettigoniidae: Conocephalus nigropleurum)

Abstract

Sexually receptive females of Conocephalus nigropleurum were tested in an arena at 30 °C for responsiveness to tape-recorded models of male calling song. Exit bearing from the arena relative to speakers was the response criterion. Models were the song of a male recorded at 30 °C, the same recording with tegminal opening sounds deleted, and the same male's song at 25 °C. A fourth model was a recording of two males, 10 cm apart, singing at 30 °C, less than 10 cm equidistant from the microphone. Female choice was established for all model pairings. Preferences could not be ranked on a single scale, indicating that discriminatory criteria change with particular combinations. The model with two males proved most effective.In presenting a choice between 'two males' and 'single male with intact song (30 °C),' when the broadcast amplitude levels of these models were identical for both speakers, four times as many phonotactic exits occurred in the quadrant of the speaker broadcasting dual song than occurred in the single male quadrant. This suggests that males, competing acoustically in the field, could increase their chances of attracting females by (paradoxically) signalling in proximity to other competitors.