Hexacentrus khasiensis Ghosh, Jaiswara & Rajaraman, 2023

Ghosh, Aarini, Jaiswara, Ranjana, Sabharwal, Shagun, Dasoju, Vivek, Bhattacharjee, Anubhab & Rajaraman, Bittu Kaveri, 2023, Description of three new species of predatory Genus Hexacentrus (Orthoptera Tettigoniidae) from India, with bioacoustic and morphological characterizations, Zootaxa 5249 (3), pp. 335-356 : 339-342

Hexacentrus khasiensis Ghosh, Jaiswara & Rajaraman sp. nov.

Type material. Holotype, ♂, INDIA: Meghalaya, East Khasi Hills, Shillong , ~ 1400 m a.s.l., 01.IX.2021, 25° 36’ 59.76” N; 91° 54’ 2.52” E, AG_SH1_M6 ( ZSI) . Allotype, ♀, AG_SH1_F1, same locality as holotype ( ZSI) . Paratypes (4 ♂, 3 ♀), same information as holotype, VIII–IX.2021: 2 ♂ ( AG _ SH1 _M1, AG_SH1_M2) 2 ♂ ex-AG_ SH1_M3 ( BNHS) , ex-AG_SH1_M4 ( BNHS); 2 ♀ ( AG _ SH1 _F2, AG_SH1_F3), 1 ♀ ex-AG_SH1_F4 ( BNHS) .

Type locality. East Khasi Hill , Shillong, Meghalaya, India ( Fig. 1 ) .

Distribution. In addition to type locality, this new species has been heard in different parts of the Khasi hills including the Ri-Bhoi and West Khasi Hill districts of Meghalaya. The same call type has been recorded in Balpakram National Park in the South Garo hill district of Meghalaya ( Fig.1 ).

Etymology. The species is named after the type locality Khasi hill of Meghalaya.

Diagnosis. The species is somewhat similar to H. formosanus Chen & He, 2021 with respect to the marks on the disc of pronotum however it differs as follows: In H. formosanus the lateral margin of the pronotum is straight but in H. khasiensis sp. nov. it is slightly concave. Teeth in the middle region of the stridulatory file in H. khasiensis sp. nov. are much wider than the lateral teeth. Stridulatory teeth are more in number in H. khasiensis sp. nov. Apical third of cerci in H. khasiensis sp. nov. longer and styli narrower. Female ovipositor is much narrower.

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.

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.

Figures

FIGURE 1. India map showing distributions for all three species including their type localities. The light green colour shows Haryana state, and the dark green colour shows Meghalaya state with other colours highlighting the distribution of H. ashoka and H. tiddae in Sonipat district (dark blue); H. khasiensis distribution in the East-Khasi hills (yellow), West-Khasi hills (red), Ri-Bhoi (sky blue), South Garo hills (purple).

FIGURE 2. Picture of all 3 species in their natural habitat—H. khasiensis male (A) and female (B), H. ashoka male (C), H. tiddae male (D).

FIGURE 3. Hexacentrus khasiensis male: (A–B) Dorsal and Lateral view. Scale 5mm, (C) Dorsal view of head and pronotum. Scale 5mm, (D) Supra-anal plate, (E) Lateral view of head and pronotum. Scale 5mm, (F–G) Dorsal and Lateral view of subgenital plate, Scale 1mm.

FIGURE 4. Hexacentrus khasiensis female: (A–B) Dorsal and Lateral view. Scale 5mm, (C) Dorsal view of head and pronotum, (D) Ventral view of Specimen, (E) Face, (F) Maxillary palpi. Scale 1mm, (G) Lateral view of head and pronotum, (H) Dorsal view of the subgenital plate. Scale 1mm, (I) Ovipositor in lateral view, (J) Supra-anal plate. Scale 1mm.

FIGURE 6. Hexacentrus khasiensis sp. nov. (A) Waveform of calling song, (B–D) Oscillogram of the first part of call at various time scales, (F) Spectrogram and (E) Power spectra of the first part of the call (G–I) Oscillogram of the second part of call at various time scales, (J) Spectrogram of the second part of call and Power spectra of the high amplitude syllables (K) and low amplitude syllables (L).

FIGURE 14. Stridulatory apparatus structure—ventral side of left wing with file and scraper on the dorsal side of right wing (A–B) of H. khasiensis; (C–D) of H. ashoka; (E–F) of H. tiddae.