SOUND PRODUCTION AND HEARING IN THE PYRALID MOTH SYMMORACMA-MINORALIS

Males of the moth Symmoracma minoralis (Snellen) (Lepidoptera: Pyralid ae, Nymphulinae) were observed producing a high-intensity calling song (95dB SPL at a distance of 10cm) with a complex amplitude and frequen cy modulation (peaks of carrier frequency at 60 and 12OkHz). This soun d is produced by a hitherto unknown type of sound organ located in the last abdominal (genital) segment, which may act as a tymbal. The obse rved directionality of sound output is probably achieved by means of a hollow cone surrounding the sound organ. Electrophysiological recordi ngs revealed that the tympanal organs of S. minoralis are most sensiti ve in the frequency range from 50 to at least 100kHz, which is distinc tly higher than the minimum threshold levels in most other moths yet e xamined. The origin of genital sound production is discussed with resp ect to abdominal pheromone glands and pheromone-releasing movements.