Bioacoustics of Cardiodactylus minuta

Remarks. Based on new material, we can redescribe the species and describe the calling song. New diagnosis. Cardiodactylus minuta is very similar to Cardiodactylus niugini Dong & Robillard, 2016 in the general habitus and colouration pattern, and the pseudepiphallus having a posterior apex spatulate, but C. minuta differs by: (1) the lateral side of FW almost entirely yellow ventrally (instead of having a brown ventral margin in C. niugini ); (2) the male FW having its mirror (d1) more slender at the posterior end separated by three accessory veins (instead of two in C. niugini ), (3) the apex of pseudepiphallus with its apical end more tongue-shaped, its apex more rounded (instead of more fan-shaped and apex broad in C. niugini ), (4) the pseudepiphallic parameres with their posterior lobe slightly longer and more slender and anterior lobe having its apex bent. The calling song of C. minuta also differs from that of C. niugini by the call structure being an echeme composed of more closely-spaced syllables, frequency spectrum more tonal and a higher dominant frequency. The species is also similar to Cardiodactylus nigris Bhowmik, 1981 and Cardiodactylus pictus Saussure, 1878 in the general habitus and colouration patterns, but differs clearly from C. nigris by the lateral side of FW entirely yellow, and by the shape of the posterior apex of pseudepiphallus and of the pseudephallic parameres.

Distribution. Papua New Guinea . Calling song ( Fig. 10 ). The calling song of C. minuta is composed of echemes, often isolated in time, but that can aggregate to form an echeme-sequence of three to 15 echemes of increasing amplitudes. In such case, the last echeme can be twice longer than the other echemes. On average, the echeme duration is 1.4±0.5 s made up of 48±18 syllables. The average syllable duration is 12.7±3.3 ms. On rare occasion, one to four much shorter syllables (3–5 ms instead of 10–15 ms) occur in the second half of the echeme. The average syllable period is 28.99±2.33 ms. The frequency spectrum is made up of harmonics; the dominant frequency is 18.64±0.87 kHz, and does not correspond to the fundamental frequency, but to the third harmonic. The fundamental frequency is around 6–7 kHz and has a higher energy than the second harmonic.