Hexacentrus mundus (Walker, 1869)

Morris, Glenn K, Ingrisch, Sigfrid, Willemse, Fer, Willemse, Luc, De Luca, Paul A. & Klimas, Dita, 2025, Stridulation songs of some Tettigoniidae (Ensifera, Orthoptera) from Papua New Guinea, Zootaxa 5600 (1), pp. 1-81 : 72

Hexacentrus mundus auct. (= Walker 1869?)

Specimens studied. PNG, nr Wau, W.E.I., 30 vii & 4 viii 1981, G.K. Morris (2 males) (depository NBC Leiden, Specimens discovered missing 2024) .

Systematics. This species, described from Ceram, the Moluccas, has been reported in many references from a range reaching from Japan, China and the Philippines to Borneo, Java, Sulawesi, the Moluccas, Timor and throughout New Guinea.

The Wau males have been compared with material at hand preliminarily arranged under H. mundus : from Java, from the islands of Obi, Halmahera and Key and the remainder from New Guinea. The stridulatory file of all these males comes near that of the type-species H. unicolor (figures and description of the latter in Heller 1986) but may be recognized immediately by the presence of one to three remarkably large teeth in the mid part of the file, which are lacking or scarcely indicated in H. unicolor . Among the mundus-like specimens it was found that the Java males have three, those from the Moluccas, especially from Obi one to two and the New Guinea males two of such large teeth. Besides there are additional differences in width, spacing and shape of the remaining teeth, especially apparent in the Javanese males. In the Wau males the two large central teeth are followed distally (i.e., towards the posterior margin of the elytron) by 4–5 stout ones and these again by 5–7 increasingly smaller and narrower spaced ones. The number of teeth between the central large ones and the base of the file is about 23, those near the large ones being widest of all teeth (0.25–0.3 mm) and most widely set (4 teeth per 0.25 mm). By lack of sufficient data, we abstain in any further analysis. It is clear, however, that revisionary work on the systematics of this group of species, based on their bioacoustics and stridulatory apparatus could be very useful.

Stridulation. The relatively massive species diagnostic files of Hexacentrus are sparsely toothed and twisted ( Heller 1986, See his Fig. 1 ). The song of H. mundus also has a strangely loud percussive quality. Waveforms of sound bursts ( Fig. 77D ) show no time-distinct tooth-derived amplitude modulations. Perhaps its scraaper makes a single hammer-like impact, slipping off a single very enlarged file tooth to bang basad into a 90° file twist? In Hexacentrus unicolor with each cycle of movement to and fro, “only one pulse is created” ( Heller 1986).

Figures

FIGURE 1. Acauloplacella (Papuaprium) immunis, habitus of adult male, dorsal aspect, on vertical glass in daytime cryptic posture.

FIGURE 77. Hexacentrus mundus acoustic analysis: A) part of a calling bout, initiated by a single transient pulse, followed by high-rate repetition of multiple short sound bursts at a stable period; B) complex wavetrain of starting pulse; C) spectrum of this onset pulse; D) 5 sound bursts excerpted from sustained song in A, little or no indication in waveform of tooth events; E) spectrum of time sample in D, insect’s most intense output in middle audio range.