Bioacoustics of Hexacentrus

( Fig. 77 ) Type-species: Hexacentrus unicolor Serville, 1831 (by monotypy). More than 20 taxa are assigned to this genus. The systematic position of several of them is not clear, mainly by absence of reliable specific characters. It transpired however, that morphological particulars of the male stridulatory file offer uncommonly good means for identification. It might be expected that bioacoustics will do the same. We compared the files in H. dorsatus , H. pusillus , H . australis (all Redtenbacher 1891 ), H. fuscipes Matsumura & Shiraki 1908 , H. japonicus Karny 1907 , H. karnyi Griffini 1909 , H. borneensis C. Willemse 1961 and a small yet undescribed species from eastern New Guinea with those in H. unicolor and H . mundus . All of them are quite characteristic and recognizable immediately. Two males before us from the surroundings of Wau, Morobe District , NE New Guinea may easily be arranged under what hitherto has been understood to represent H. mundus (Walker, 1869) .

1 Tegmina narrowed in males; stridulatory file narrow and provided with relatively greater number of teeth................................................................................................. H. unicolor Serville, 1831 - Tegmina inflated in males; stridulatory file wide and provided with relatively fewer teeth............................. 2 2 Stridulatory file with approximately 27 teeth; male subgenital plate with straight styles, diverging apically; female subgenital plate triangular, apex with median rounded excision; Mid tibiae dorsally armed................ H. japonicus Karny, 1907 - Stridulatory file with approximately 32 teeth; subgenital plate with styles curved and converging apically; female subgenital plate triangular; bifurcated apically; mid tibiae dorsally unarmed................................ H. bifurcata sp. nov.

1. Prosternum and Mesosternum unicolor, femora in the general coloration.......................................... 2 - Prosternum and Mesosternum blackish brown, femora brownish at apex.......................................... 3 2. Mirror on the tegmen rhomoboid in shape, body yellowish green, third and fourth joint of tarsi blackish brown ( Wang and Shi 2005 : Fig 1 , 4 )................................................................. H. expansus (Wang and Shi) - Mirror on the tegmen oviform........................................................................... 4 3. Antennae concolorous, Male tegmen with angular apex....................................................... 5 - Antennae discolorous, Male tegmen rounded at apex......................................................... 6 4. Male tegmen inflated.................................................................................. 7 - Male tegmen not inflated............................................................................... 8 5. Fore femora armed with 5–6 ventral spines on the inner margin, stridulatory file with 32 teeth, subgenital plate with styles curved and converging apically ( Farooqi and Usmani 2018b : Fig 7I ; 8A.............. H . bifurcatus (Farooqi and Usmani) - Fore femora armed with 18–30 ventral spines on inner and outer margin, stridulatory file with 20–23 teeth, styles diverging from each other ( Ghosh et al. 2023 : Fig 11 A–D, 12)....................................... H. tiddae (Ghosh et al. ) 6. Hind wings are shorter and hidden under tegmen, stridulatory file with 37–40 teeth with 4 large teeth in the middle ( Ghosh et al. 2023 : Fig 3A–B , 5 )........................................................... H. khasiensis (Ghosh et al. ) - Hind wings same size or larger than tegmen, stridulatory file homogenous with 40 teeth ( Ghosh et al. 2023 : Fig 7 A–B , 9)................................................................................... H. ashoka (Ghosh et al. ) 7. Stridulatory file homogenous, Ovipositor straight, base thickened ( Ingrisch and Shishodia 2000 : Fig 143–144)............................................................................................ H. major (Redtenbacher) - Stridulatory file with 2–3 large teeth, ovipositor curved, rather longer than the body................ H. mundus (Walker) 8. Male tegmen short and broad, stridualtory file moderately sulcate with <30 teeth and with>3 large teeth................ 9 - Male tegmen long and narrow, stridulatory file moderately sulcate with>30 teeth and 3 large teeth at the distal end ( Farooqi and Usmani 2018b : Fig 1 ; Inagaki et al. 1990 : Fig B,D)...................................... H. unicolor (Serville) 9. Stridulatory file with 5 large teeth towards the distal end, Subgenital plate long with elongated, wide, longitudinal median furrow, lateral ridges well developed, apical margin with rounded excision; styles straight, diverging apically, chirping call ( Inagaki et al. 1990 Fig A, B; Farroqi and Usmani 2018b: Fig 4I )............................... H. japonicus (Karny) - Stridulatory file with 4 large teeth in the middle, Subgenital plate long with elongated, wide, longitudinal median furrow, lateral ridges well developed, apical margin with rounded excision; with styles curved, converging apically, buzzing call ( Fig 1G, 1I ).................................................................................... H. sylvanus sp. nov