Mecopoda niponensis vietnamica Heller & Korsunovskaya, 2021

Heller, Klaus-Gerhard, Baker, Ed, Ingrisch, Sigfrid, Korsunovskaya, Olga, Liu, Chun-Xiang, Riede, Klaus & Warchałowska-Šliwa, Elżbieta, 2021, Bioacoustics and systematics of Mecopoda (and related forms) from South East Asia and adjacent areas (Orthoptera, Tettigonioidea, Mecopodinae) including some chromosome data, Zootaxa 5005 (2), pp. 101-144 : 116-118

Mecopoda niponensis vietnamica Heller & Korsunovskaya subsp. nov.

Holotype: VIETNAM: Tân Phú District, Dong Nai, Cát Tiên National Park , 128 m a.s.l., 11°26’ N, 107°26’ E. 13 vi 2019, leg. N. Sevastianov. ZIN. Song and stridulatory organs studied.

Diagnosis. Differs from the nominate subspecies by longer tegmina, from other Mecopoda species by the characteristic amplitude modulation in the trill (see Fig. 6–7 ) and from the Vietnamese species M. ampla and M. prominens in file structure (see Fig. 11–12 ).

Morphology. As nominate subspecies, but with longer tegmina (see above).

Song. The recorded specimen had an unusually variable song containing two elements. It produced trill-like series, quite similar to the song of the continental subspecies ( Fig. 6 ) and to that known from other parts of its range (for details see Liu Cx et al. 2020). These series last for many minutes and have a relatively complicated structure. Within a song unit, the low-amplitude beginning and ending phases consist of repeated simple syllables, while the high-amplitude climax is composed of many repeated subunits. In the recorded specimen the subunits consisted of five to six syllables with a characteristic amplitude pattern ( Fig. 7 ). In other parts of its range like Japan and Korea (n. niponensis ) one subunit seems to have typically only three syllables ( Ichikawa et al. 2006; Kim 2009). Besides the trills, the specimen produced also occasionally long series of echemes before the trill. In the frequency spectrum, the ultrasound components were even stronger than the peak in the audible range ( Fig. 14 ).

Stridulatory file. Like specimens of the nominate subspecies, also the Vietnamese specimen has a long file carrying about 115 teeth ( Fig. 11 B ) like M. n. niponenis . The inter-teeth distances start anally with 50 µm and reach their maximum of about 80 µm between the 30th and 40th tooth ( Fig. 12 ). In the file of the lectotype of M. n. niponenis the inter-tooth distances are slightly smaller but there is some variability in this character. The file of the M. n. continentalis specimen (105 teeth) photographed by Liu Cx et al. (2020) is similar to M. n. vietnamica n. ssp, but has the maximum around the 50th tooth. Another Chinese specimen of M. n. continentalis ( Fig. 11 A ; CH 7674, 107 teeth) is between the lastly mentioned and M. n. vietnamica subsp. nov., and the specimen from Fujian (M. n. continentalis; 115 teeth) is similar to the lectotype of M. n. niponenis ( Fig. 12 ).

Distribution. Vietnam.

Measurements (length in mm). Pronotum 9.0, tegmina 55, hind femur 51.7.

Figures

FIGURE 6. Oscillograms of the calling songs of species of the Mecopoda niponensis subgroup and of M. cf. yunnana. Overview (12 s sections).

FIGURE 7. Oscillograms of the calling songs of species of the Mecopoda niponensis subgroup. Details (1 s sections). In M. himalaya synchronous registration of movement of left tegmen and sound (upper line: upward deflection indicating opening, downward closing; lower line: sound).

FIGURE 11. Stridulatory files in Mecopoda and Eumecopoda. A M. niponensis niponensis, lectotype, B M. niponensis vietnamica subsp. nov., holotype, C M. himalaya, CH3737 (Malaysia), D M. himalaya (=M. ampla malayensis, holotype), E M. himalaya (=M. ampla javaensis, holotype), F M. himalaya (=M. fallax aequatorialis, holotype), G M. macassariensis, holotype, H M. fallax, Thailand, I M. stridulata stridulata, CRTmeceloM02 (Borneo), J M. stridulata stridulata, holotype, K M. paucidens sp. nov., (Java), L M. sismondoi sp. nov., holotype, M M. javana, neotype, N M. javana, Sri Lanka, O M. mahindai sp. nov., holotype, P M. angusta, CH3697, Q M. dilatata, ORT 2005/413 (Borneo), R E. cyrtoscelis zhantievi subsp. nov., holotype, S M. prominens, holotype, T M. ampla ampla, holotype. Scale 1 mm.

FIGURE 12. Inter-tooth spacing in stridulatory files of Mecopoda species. Thick lines and filled symbols indicate specimens with known song. A–D: M. elongata group: A M. niponensis subgroup and M. marmorata, B M. himalaya and macassariensis, C M. fallax and species with similar files, D M. confracta subgroup, E other Mecopoda and Eumecopoda species.

FIGURE 14. Power spectra of the calling songs of Mecopoda species. In A, red line trill, green line chirp; in B–D, grey area opening and closing hemisyllable together, blue line opening hemisyllable only, yellow line closing hemisyllable only (for Eumecopoda opening/closing assumed).