Calling Songs, Duets, and Auditory Tuning in Two Cryptic Katydids (Tettigoniidae: Phaneropterinae: <I>Amblycorypha</I>)

Abstract

In most katydids, females listen to and locate a stationary, singing male for mating. Pair formation differs in phaneropterine katydids where pairs form duets and the male typically Þnds the female after hearing her acoustic reply to his song. We recorded the duetting behavior of two cryptic species of phaneropterines, Amblycorypha rotundifolia (Scudder) and Amblycorypha alexanderi Walker (Tettigoniidae: Phaneropterinae), from populations in their zone of sympatry. The songs of the two species differed in their temporal properties, and the duets differed in the timing of the femaleOs replies with respect to the maleOs song. We also measured the hearing sensitivity and auditory tuning in these species by recording extracellular neural responses to sound stimuli varying in frequency and intensity. Individuals of both species were most sensitive to frequencies near 13 kHz, which corresponds to the frequencies of the malesO calling songs and to the peak frequency in the femalesO tick responses. Both species also responded to pulses with ultrasonic carrier frequencies. For higher amplitude stimuli, neural responses had shorter latencies and more action potentials. Latency functions differed for low-frequency and high-frequency stimuli. These data form the basis for understanding how auditory processing and sexual selection might be involved in the recent diver- gence of these two cryptic species.