Bioacoustics of Hexacentrus tiddae

Diagnosis and Description. The species is similar to H. ashoka , H. bifurcata & H . japonicus but differs by the following characters. Body medium size and slender ( Fig. 11A–B ). Head. Face longer than wide. Antennae without any short dark rings. Fastigium verticis laterally much more compressed, apically tapering and triangular in dorsal view pointing appearance apically. Scapus cylindrical with slight bulge at apex in dorsal view, scapus almost 3 times as wide as fastigium ( Fig. 11C & 11F ). Pronotum. Pronotum longer than wide, flat with a slightly upward curved near end, longer than broad and extended posteriorly. Anterior and posterior margins slightly concave; an hourglass-like band covers the whole pronotum ( Fig. 11C–D ). Legs. FI dorsally unarmed and ventrally armed with 18–30 spines on inner and outer margins, 1 apical spine on lateral margin; TI inner tympanum slightly longer than outer tympanum; TI dorsally unarmed and ventrally armed with 6 subapical spurs on each side, both inner and outer margin without spines; FII dorsally unarmed and ventrally armed with 18–22 spines on inner and outer margins, 2 apical spines on the lateral margin; TII dorsally unarmed and ventrally armed with 6 subapical spurs on each side, both inner and outer margin without spines; FIII dorsally unarmed and ventrally armed with 39–52 spines both or inner and outer margin; TIII dorsally armed with 34–36 spines on both inner and outer margins and ventrally armed with 11–14 subapical spurs on both inner and outer margins, one subapical spur in center. Male. Wings. Hindwings almost as long as tegmina, hidden under tegmen; tegmen is long surpassing hind tibiae. Male tegmen are long, broad in middle, and nearly triangular at end. M straight, thick distally, CuP bent distally, space between CuP and CuA shorter than between M and CuA, 1 st anal vein bearing stridulatory file straight, bent in middle, ventral side with 20–23 teeth ( Fig.14C , 12 ). Male Genitalia . Supra-anal plate triangular with a dorsal groove. Little broadened short apex slightly pointed. Cerci cylindrical at base; broad with a tubercle on internal side, then abruptly narrowed to small digitiform apical appendages with strongly incurved apex ( Fig.11E ). Sub-genital plate elongates with a median longitudinal furrow, lateral ridges well developed, apical margin with prominent ‘V’-shaped bifurcation ( Fig.11G ). Styli slightly thicker at base than at tip, both are diverging from each other, and have the apex is rounded and inward curved ( Fig. 11G–H ). Males BL FW_L BL_FWL PH PL FI_L TI_L FIII_L TIII_L Holotype 27 36 45 3.4 6.5 6.4 7.6 16.7 16.5 M_1 paratype dry 22.7 34 42 3.3 6.5 6.5 6.7 15.1 16.2 Acoustic measurements. Hexacentrus tiddae produces a regular amplitude modulated pattern of continuous syllables, alternating between longer, higher amplitude syllables and faster, low amplitude syllables. All syllables have the same broadband spectral structure. The peak frequency is 9.4 ± 3.6 kHz ( Fig. 13D–E ) and the bandwidth is 40 ± 3.2 kHz ( Fig. 13D–E ). The low amplitude syllables last for 0.9 ± 0.4 ms, with a total syllable period of 1.61 ± 0.6 ms ( Fig. 13B–13C ), and SRR of 715 ± 156 (n=3 animals, 10 syllables of each kind per animal). The high amplitude syllables occur regularly, separated by an average interval of 846.25 ± 46 ms. The high amplitude syllable duration is 2.33 ± 0.7 ms with a syllable period of 1.71 ± 0.4 ms and SRR of 463 ± 120.2 ( Fig. 13C ) (n=3 animals, 10 syllables per animal). The juxtaposition of the high amplitude buzzing bursts and the low amplitude background trill sounds almost like two simultaneous callers.