Acoustic and vibrational signaling in true katydid Nesoecia nigrispina: three means of sound production in the one species

Abstract

The males of Mexican katydids Nesoecia nigrispina (Stal, 1873) produce calling songs and protest sounds using the same stridulatory apparatus as in most of the other Ensifera at the base of the elytra. It includes pars stridens on the upper elytron and plectrum on the lower. Calling sounds of two types (fast and slow) are 2-pulse series, repeated with a frequency of 1.2-4.5 s-1. Protest signals in the form of short trills from the same pulse duration males produce with tactile stimulation. The pulse repetition rate is more higher than that of the calling sounds - up to 10 (mean c. 8) s-1. The frequency spectra of these signals have maxima in the band of 14-15 kHz. However, in addition to the sounds described, both males and females are capable to produce protest signals of the second type with the help of another sound apparatus, namely with the help of the wings. Insects with removed elytra are unable to produce an audible sound. Thus, the sound is produced by the friction of the wings on the elytra, but there are no specialized stridulatory structures on them. In individuals of both sexes, in response mainly to tactile stimulation, short clicks are recorded, which they make, apparently, by the mandibles. Vibrational signals at tremulation are emitted by individuals of both sexes during courtship and males, completing the calling signal cycle and after copulation. It is possible that vibrational signals are an additional factor in reproductive isolation in sympatric species, since the calling sound signals in representatives of the genus Nesoecia are similar and exhibit significant variability.