Hexacentrus sylvanus Tiwari and Diwakar, 2024

Tiwari, Chandranshu & Diwakar, Swati, 2024, The Orchestra Nocturne: Description For Six New Katydid Species From India (Orthoptera: Tettigoniidae), Zootaxa 5405 (2), pp. 227-245 : 229-231

Hexacentrus sylvanus Tiwari and Diwakar sp. n

( Fig. 1 )

Material examined: Holotype: Male. INDIA: Assam, Hollangapar Gibbon Wildlife Sanctuary, Jorhat ~ 120 m a.s.l. 2015, Coll. Chandranshu Tiwari, Department of Environmental Studies, University of Delhi, 110007 (Delhi), India. Paratype: Assam, Hollangapar Gibbon Wildlife Sanctuary, Jorhat ~ 120 m a.s.l., 2021 Coll. Chandranshu Tiwari (2 ♂).

Type locality. Hollangapar Gibbon Wildlife Sanctuary , Jorhat, Assam, India.

Measurements (length in mm): Body 26.67 (4.65); tegmen 31.95 (1.24); pronotum 8.13 (1.48); fore-femora 8.35 (1.11); mid-femora 8.57 (1.42); hind-femora 21.25 (3.53); fore-tibia 9.61 (2.79); mid-tibia 9.33 (2.39); hind-tibia 22.34 (1.77); file 2.1 (0.0).

Distribution: Nocturnal. Found only in the dense understorey. In addition to the type locality, the new species was also recorded by the collector in ONGC colony, Cinnamara in Jorhat. The species is likely to be distributed in North-East Himalayas.

Seasonal occurrence: The species was recorded from the type locality during monsoon and wet post-monsoon period.

Etymology: The specific epithet reflects habitat of the species. Latin adjective (=of the forest), following Hexacentrus in gender.

Differential diagnosis: The new species is similar to Hexacentrus japonicus ( Karny 1907) but differs in the following characters: 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. The two species can also be differentiated by their calls, H. japonicus produces distinct amplitude modulated chirps whereas H. sylvanus produces a continuous buzz (Ingaki et al. 1986; as Hexacentus sp. 1 in Tiwari and Diwakar 2023a)

Description:

Male: Body medium sized and slender. Head: antennae with alternate short dark bands apically. Fastigium of vertex triangular, narrow; compressed laterally with a longitudinal median sulcus; apex obtusely rounded. Fastigium of vertex separated from the fastigium of frons by a furrow. Median ocellus well developed. Eyes are globular. Pronotum saddle-shaped, dorsal region longer than wide and expanded on posterior region. Slightly depressed behind first transverse sulcus; with three transverse sulci, second and third ones restricted to disc, a U-shaped sulcus is present between second and third transverse sulci anterior dorsal margin slightly concave, with slight median excision. An hour glass shaped band covers the whole pronotum; median carina faintly visible. Pronotal disc flat, expanded, broadly rounded and highly rugose on posterior region; lateral lobes of pronotum inclined; longer than high. Prosternum armed with two long, cylindrical spines; mesosternum and metasternum armed with a pair of short and thick sternite. Thoracic auditory spiracle large, oval, slightly hidden under the lateral lobe of pronotum with a tubercle at midanterior edge. Legs: genicular lobes of fore femora armed with a single spine on inner side and unarmed on outer side, mid and hind genicular lobes armed with bispinose on both inner and outer side. Fore coxae with a forward outward projecting spine. Fore-femora and mid femora armed with 2 spines, Hind femora ventrally armed with 9–10 spines each on inner and outer margin. Fore tibiae dorsally unarmed. Fore tibiae ventrally armed with 5 long, movable, outwardly bowed opposing spines decreasing in length from basally to apically each on inner margin and outer margin. Mid tibia dorsally with 2 spines on inner margin only, ventrally armed with 6 long, movable, outwardly bowed opposing spines decreasing in length from basally to apically each on inner and outer margin. Hind tibiae dorsally armed with 15 spines on inner and outer margin. Hind tibiae ventrally armed with 30–31 spines increasing in length and density from basally to apically on inner margin. Single dorsal pair of spurs and two ventral pairs (inner small and outer large) of spurs present on the apical region of hind tibiae. Wings. Tegmina longer than hind wings. Tegmina reaching the middle of hind tibiae. Male tegmina broad at the middle. Stridulatory file with 27 teeth (n=3), including four large teeth in the middle, file moderately sulcate, gradually narrowing at distal end, abruptly narrowing with few teeth towards proximal end.

Male genetalia. Subgenital plate long with median longitudinal furrow apically, lateral ridges well developed, apical margin with rounded excision; styles diverging basally, apex slightly incurved. Cerci robust, apical third narrowed and curved inwards; apex pointed.

Female: unknown. Supposed to be similar to that of H. japonicus .

Coloration: Green to greenish yellow when alive. Antennae with yellow brown with regularly spaced dark annules. Occiput and vertex bearing thick rusty brown stripe covering most of the head in dorsal view. Pronotum dorsal disc bearing rusty brown stripe similar in width as of head up to half the length, much widened posteriorly. Tegmen appears green/yellow when alive, but is hyaline with veins and veinlets brown. Male tegmen with stridulatory apparatus and apical field rusty brown, lateral part venation brown.

Depositories: The specimen are deposited in the Department of Environmental Studies, Faculty of Science, University of Delhi.

Figures

FIGURE 1. Hexacentrus sylvanus (a) habitus, (b) dorsal view of head, (c) laterial view of head, (d) face, (e) lateral view of head and pronotum (f) ventral view of right tegmen (P: Plectrum, M: Mirror), (g) ventral view of subgenital plate (h) lateral view of cercus, (i) scanning electron microscope image of stridulatory file.