Bioacoustics of Macroxiphus sumatranus

Remarks. The male collected from PFR ( Figs 1–3 ) appears to be morphologically more similar to Macroxiphus sumatranus sumatranus ( Haan, 1843 ) than Macroxiphus sumatranus siamensis Helfert & Sänger, 1995 by the shape of the titillators with its sclerites more elongated and curved (instead of right-angled) ( Figs 3D, 3E ); but the shape of the cercus is intermediate between the nominal subspecies from Indonesia and latter subspecies from Thailand ( Figs 3A–C ). Our male specimen has 108 teeth on the left tegmen, which is also intermediate between the two subspecies. Furthermore, the calling song of the male is more similar to that of the nominal subspecies. These variations suggest that characters used to define the subspecies may need to be reconsidered with the aid of examining more specimens from different parts of their distributions.

Distribution. INDONESIA ( Sumatra ); PENINSULAR MALAYSIA ( Johor State : PFR) [new] Calling song (1♁, 28.3°C) ( Fig. 5 ). The calling song is made up of a fairly isolated echeme, each consisting of two closely-spaced syllables. Each echeme has an average duration of 0.35±0.02 s (0.33–0.37 s). The first syllable has an average duration of 18.7±0.9 ms (17.6–19.9 ms) and an average period of 0.15±0.01 s (0.14–0.16 s). The second syllable has an average duration of 18.9±1.2 ms (17.8–20.7 ms). The interval between the two syllables has an average duration of 0.13±0.01 s (0.11–0.14 s). The call spectrum is broad-based and has a peak frequency of 11.7±1.0 kHz (10.8–13.4 kHz). The calling song of the male from PFR consists of two syllables, similar to that of Macroxiphus sumatranus sumatranus (recorded from Maninjau from West Sumatra), whereas that of Macroxiphus sumatranus siamensis (recorded from Ulu Gombak in Selangor and Surat Thani in Thailand ) typically consists of four syllables.