Stridulation of the clear-wing meadow katydid <i>Xiphelimum amplipennis</i>, adaptive bandwidth

Abstract

Rubbed wings, analysed calls and peculiar sound generator structure in males of a conocephaline katydid, Xiphelimum amplipennis, give insight into the making of broadband spectra. High shear forces are indicated by a robust forewing morphology. Intensity is high for frequencies in a 20-60 kHz ultrasonic band. Besides a typical katydid sound-radiating mirror and harp, this insect has a long costal series of semitransparent specular sound radiators. These wing cells are loaded behind by an enlarged and partitioned subwing air space. Calls repeat steadily with five different time-domain sound elements. Distinctive spectra are associated with two of these, giving stepwise frequency modulation that combines to create the exceptionally wide spectral breadth. Broadcast sound levels at 10 cm dorsal, right and left, are near 100 dB. Costal wing-cell sound radiation was explored by loading the costal ‘speculae’ with wax. This produced almost no decrease in lateral sound levels, but did alter spectral content. Apparently this insect’s costal region both baffles and radiates. The species lives at high densities in cluttered vegetation and sound signal attenuation should code via spectral shape for distance ranging.