Spectral analysis of the male calling song (Figs. 2E, S1) shows that most of the song’s energy is contained within a relative narrow frequency band between ca. 8-11 kHz (pooled mean CF=9.2 ± 0.2 kHz, n=5; see also Table S1). Recordings under lab conditions exhibit an additional low amplitude frequency peak at 26-29 kHz that is not present in field recordings. As similar ultrasonic frequency components were reported by Morris & Mason (Morris and Mason, 1995), we assume that the higher frequencies are present in all songs but attenuate quickly under field conditions.
Our results show that the production of loud calling songs in A. acuta relies not only on the use of two, but three mechanical oscillators – the wings, the pronotal chamber possessing structural resonance, and the Helmholtz resonator formed by the chamber and the animal’s body – that are set into motion and driven at or close to resonance by the animal’s stridulatory movements.[1]
References
- . Chamber music: an unusual Helmholtz resonator for song amplification in a Neotropical bush-cricket (Orthoptera, Tettigoniidae). The Journal of Experimental Biology. 2017;220(16):2900 - 2907. Available at: http://jeb.biologists.org/lookup/doi/10.1242/jeb.160234.