Bioacoustics of Hexacentrus ashoka

Description. Mostly similar to H. khaisiensis sp. nov. Except for the following characters. Male. Body slender, medium-sized ( Fig. 7A–B ). Head. Fastigium verticis triangular, narrow, laterally compressed with a median longitudinal sulcus, and apex round in lateral view. At base of fastigium verticis is almost the same width as the scapus. Fastigium verticis is separated from fastigium frontis by a furrow. Eyes globular ( Fig. 7C–E ). Pronotum. Saddle shaped, expanded in posterior region; with three transverse sulci, slightly depressed behind first transverse sulcus, third transverse sulcus is restricted to disc, “U” shaped sulcus presents between second and third transverse sulci, anterior margin slightly concave with no excision present. An hourglass-like brown band is present in the pronotum. Median carina is faintly visible ( Fig. 7C ). Pronotal disc is flat, posteriorly expanded, broadly rounded, posterior margin concave with slight median excision. Lateral margin of pronotum descending, longer than high, with the humeral sinus absent, anterior angle is round and anterior margin shorter than posterior margin from lateral view, posterior angle is obtuse. Thoracic auditory spiracle large, oval, slightly hidden under lateral lobe of pronotum ( Fig. 7D ). Wings. Tegmina slightly shorter or the same as the length of hind wings. Tegmina long and crosses the mid tibiae of the hind leg. Male tegmina long, broad in middle, apex narrow round in lateral view ( Fig. 7B ). Stridulatory file broader at the tip and narrows towards the centre. Tooth length is different in different parts of the file, widest in the beginning. The stridulatory file has 40 teeth ( Fig. 9 ). Legs. Fore coxae are provided with a forward outward projecting spine. FI with 4 subapical spurs and 1 apical spur, 16 spines in between sub-apical spurs on the inner margin, and approximately 27 spines with no subapical and apical spur on the outer margin. TI dorsally unarmed and ventrally armed with 6 long subapical spurs inwardly bent, 1 st subapical spur slightly shorter than 2 nd subapical spur and then decreasing in length apically on both margins. TII is dorsally armed with two subapical spurs, sometimes absent, ventrally armed with 6 subapical spurs on inner and outer margins. TIII dorsally armed with 24–36 spines on the inner margin and 27–35 spines on the outer margin, TIII ventrally armed with 10–15 subapical spurs increasing in length and density each on the outer margin and 8–15 subapical spurs increasing in length and density towards tarsus. Male Genitalia. Supra-anal plate triangular in shape with dorsal groove. Cerci are cylindrical in shape at the base; it is broad with a tubercle internal side then narrowing to small digitiform apical appendages with strongly incurved apex ( Fig.7F ). Subgenital plate is long with elongated, wide longitudinal median furrow, and lateral ridges are well developed, apical margin with wide V-shaped excision, styles curved, slightly thick at the base than apex, diverging basally and slightly converging apically ( Fig. 7G ). Female. Pronotum. In dorsal view the posterior lobe of the female pronotum is less widened and rounded than in males ( Fig. 8C ). Wings. Hind wings and tegmina of same length and shape as in male ( Fig. 8B ). Female Genitalia. Supra-anal plate triangular dorsal groove, short and broad at base and apex rounded. Subgenital plate triangular, small, with a dorsal groove, as long as wide, at end roundly excised ( Fig. 8I ). Cerci robust, upcurved, straight, thick at base narrow at apex, with smooth conical slightly inward appendages ( Fig. 8G ). Ovipositor dagger shaped, widest before mid-length, gradually narrowing towards end, apex pointed, serrated apically ( Fig. 8J ) Coloration. Overall green when alive ( Fig.2A ). Antennae with regularly spaced blackish brown annules. Occiput and vertex with a thick rusty brown stripe covering most of the head in dorsal view. Pronotum disc bearing rusty brown stripe less in width as of head up to half the length much widened posteriorly. Males BL FW_L BL_FWL PH PL FI_L TI_L FIII_L TIII_L Holotype 23.3 33 42 3.6 6.9 6.6 8.7 16.7 20 M_1 Paratype dry 23.3 32 42 3.7 7.5 6 8.2 16.5 19.5 M_2 Paratype dry 22.3 33 41 4.3 7.5 7.3 8.1 17 19.4 Continued. Females BL FW_L Ovi_L PH PL FI_L TI_L FIII_L TIII_L Allotype 25 30 14 4.5 5.6 5.8 7.6 19.4 16 F_1 paratype dry 22.63 30 14.4 4 6 6.8 10.1 20.2 20.5 F_2 paratype wet 21.2 30 14.7 4.7 5.4 7.2 8.5 20.5 20.6 F_3 paratype dry 23 30 14.1 3.8 5.3 6.9 7.7 19 19.1 Acoustic measurements. The call of Hexacentrus ashoka call consists of two sections ( Fig. 10A ). The first part of the call consists of a group of low-amplitude chirps with variable chirp duration: the earlier chirps are longer (337 ± 1.7 ms for the first five chirps from this portion averaged across 3 individuals) and the later chirps are quicker (261 ± 18 ms for the last five chirps from this portion averaged across 3 individuals). There is also considerable variability in the inter-chirp interval, which also reduces over time (317 ± 10 ms for the first five chirps, 187.2 ± 13 ms for the last five chirps, n=3 individuals). The second part has a group of higher amplitude and well-defined sharp chirps that sound like short buzzing sounds ( Fig. 10B–D ). Each chirp ends with a quick single syllable tick of 2 ± 0 ms length. The high amplitude chirps have groups of 80.8 ± 2.13 syllables for a total duration of 194 ± 50 ms (n=7). Each syllable is 1.7 ± 1 ms in length with inter syllable duration of 1.2 ms. The SRR is 340 ± 18. The spectrogram is broadband with a bandwidth of 5 ± 0.8kHz and a peak frequency of 8.9 ± 0.13 kHz ( Fig. 10E–F ).