Bioacoustics of Hexacentrus khasiensis

Description. Male . Body medium sized and slender ( Fig. 3A–B ). Head. Fastigium verticis triangular, narrow, laterally compressed with median longitudinal sulcus. Apex narrow, tapering forward, rounded in lateral view ( Fig. 3C ). Base of fastigium 1.25 times as wide as scapus. Fastigium verticis separated from fastigium frontis by a furrow. Eyes globular. Pronotum. Saddle-shaped, longer than broad, and expanded posteriorly. Anterior margin straight. Posterior margin slightly concave and the pronotal disc flat expanded and rounded in posterior region ( Fig. 3C ). An hourglass-like band covers whole pronotum. Median carina faintly visible. Slightly depressed behind first transverse sulcus; with three transverse sulci. A ‘V-shaped sulcus is present between first and second sulci ( Fig. 3C ). Second and third transverse sulci restricted to disk. Ventral margin of the lateral lobe inclined downwards longer than high, humeral sinus absent. Anterior angle obtuse, and posterior angle rounded. Posterior part forming a straight slope, and anterior part straight ( Fig. 3E ). Thoracic auditory spiracle large and oval, party hidden under lateral lobe of pronotum. Legs. Fore coxae with a forward outward projecting spine. FI dorsally unarmed and ventrally armed with 3–4 subapical spurs present on inner margin with 4–5 spines present in between subapical spurs and outer margin bearing 4–9 spines, no subapical spurs. TI armed with 6 long subapical spurs, first subapical spur slightly shorter than 2 nd subapical spur and then decreasing in length apically on both sides. TII armed with 6 subapical spurs on inner and outer margins. TIII dorsally armed with 22–34 spines on the inner margin and 20–33 spines on outer margin, ventrally armed with 11–15 and 10–13 subapical spurs variable in length on outer and inner margin. Male. Tegmen of medium size, broad in the middle, apical margin not oval in lateral view ( Fig. 3B ), reaching middle of hind tibia. Left tegmen long, stridulatory file with 37–40 teeth; 1 st anal vein teeth broader and elevated, followed by narrow teeth. Mirror longer than wide. Media slightly curved, Cubitus posterior vein slightly bent in middle, space between CuP and CuA slightly wider than M and CuA, 1 st anal vein bearing stridulatory file inclined, 1.3 mm long with 37–40 teeth ( Fig. 14A ). Male. Genitalia. Supra-anal plate triangular with a dorsal groove, apex round. Cerci long cylindrical, then slowly narrowing to a long digitiform apical appendage with incurved apex ( Fig. 3D ). Subgenital plate elongate with a median longitudinal furrow, lateral ridges well developed, apical margin with deeply curved ( Fig. 3F ). Female. Small body. Pronotum . Lateral lobe straight in posterior margin ( Fig. 4F ). Wings . FW narrow and short, reaching mid ovipositor ( Fig. 4B ). Female Genitalia . Supra-anal plate triangular with dorsal groove, short in length and broad basally, apex rounded ( Fig. 4H ). Cerci conical, slightly upcurved, and apex diverging. The subgenital plate is triangular and wide ( Fig. 4J ). Apex with a median excision. Ovipositor broad at the base, straight, and with pointed end ( Fig. 4I ). Coloration . Green when alive ( Fig. 2B&D ). Antennae with regularly spaced blackish brown annules. Male FW with stridulatory apparatus and apical field rusty brown. The dorsal part of the female FW is rusty brown. Males FW_L BL_FWL PH PL FI_L TI_L FIII_L TIII_L Holotype 21.4 30 2.9 6.5 6.5 7.3 17.4 17.3 M_1 paratype dry 21.3 30 4 6.4 6.7 5.7 15.8 15.2 M_2 paratype dry 21.5 32 3.9 6.5 6.5 7.5 16 17 M_3 paratype wet 21.3 31 3.1 6.3 6.3 8 15.7 17.3 M_4 paratype wet 23.4 35 3.7 7 6.3 7.8 17.8 17.8 Continued. Females BL FW_L Ovi_L PH PL FI_L TI_L FIII_L TIII_L Allotype 25.3 19.4 14 3.5 5.4 6.9 7.6 17.3 18.5 F_1 paratype dry 23.5 20 11.32 4.4 5.2 6.8 8.7 18 18.3 F_2 paratype wet 26.5 20.2 14.3 3.2 5.3 6.4 7.1 17 17.4 F_3 paratype wet 22.8 19.5 13.6 3.9 5.5 4.2 4.8 9.9 11 Acoustic measurements. The continuous call of Hexacentrus khasiensis consists of a broadband trill alternating with an amplitude modulated trill ( Fig. 6A ). All measurements were made for at least 10 syllables per call portion per animal, for multiple animals. In the field, it sounds as if two different individuals are calling because of the continuous droning sound produced by opening and closing of the wing, but recordings in the lab verified that the call was produced by a singular individual.