Cyphoderris monstrosa

Acoustic analysis agrees with previously reported results for the calling song of C. monstrosa (Fig. 2) (Morris and Gwynne, 1978; Spooner, 1973; Morris et al., 2002). Mean peak frequency of the call is 13.08±0.1 kHz (N=5). These calls are highly resonant, with the mean Q of the calling song being 57.3±18.39 (Fig. 2). Scanning laser vibrometry experiments to reveal the vibration-compliant areas of the forewings of C. monstrosa were successfully achieved in five specimens, and we hereby present an initial treatment of wing mechanics in this species. Vibrations in response to sound stimulus (at a band around the calling frequency) are limited to the mirror and also the areas herein termed the neck, the pre-mirror and the anterior portion of the harp (Fig. 3). Vibrations of the mirror and adjacent area occur in phase (‘as-one’ vibrations; Fig. 4), in a basic mode corresponding to the dominant resonant frequency. Although the mirror and adjacent areas are weakly delimited, the vibrating surface is confined within the surrounding veins. This vibration pattern was observed in both wings of all specimens scanned (N=5) and further symmetry of wing function is exhibited. Peak vibration amplitudes are observed on the mirror area (Fig. 4) with the average vibration amplitude of the mirror (as calculated by averaging all scan points on the mirror in displacement) being 182.4±77.5 nm Pa−1 for the left wing and 138.4±52.8 nm Pa−1 for the right wing, and this difference was not significant (paired t-test, t=0.874, d.f.=4, P=0.432). Mean resonant frequency of the mirror was 14.2± 1.08 kHz (N=5) for the right wing and 14.6±2.2 kHz (N=5) for the left wing (Fig. 3), and this difference was also not significant (paired t-test, t=0.618, d.f.=4, P=0.569). High coherence of vibration of the mirror shows that the observed response is reliable, with coherence approaching one around the frequencies of resonance (Fig. 3). Thus the mirrors exhibit a natural tuning at frequencies close to the calling song (Fig. 5) and this matching suggests the natural frequency of the wings is functionally tuned to a specific frequency, which is in turn being exploited for efficient, resonant sound production. The areas adjacent to the mirror (pre- mirror, neck and h1) vibrate at a lower amplitude than the mirror, and exhibit no sharp resonance (Fig. 6). The Q of the mirror’s resonance, measured from the peak on the spectra, is much lower than that of the calling song, with Q of the mirror area being 27.8± 24.8 for left wing and 12.7±3.7 for the right wing (this difference being not significant: Wilcoxon, Z=−0.674, P=0.5). [1]

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