Eotrechus fuscus, Basu & Chandra & Venkatesan & Icar-Nbair, 2017

Basu, Srimoyee, Chandra, Kailash, Venkatesan, Thiruvengadam & Icar-Nbair, 2017, Eotrechus fuscus sp. nov. from Northeastern India with a key to Indian species (Hemiptera: Heteroptera: Gerridae), Acta Entomologica Musei Nationalis Pragae (Acta. Ent. Mus. Natl. Pragae) 57 (2), pp. 391-398 : 392-397

Eotrechus fuscus sp. nov.

( Figs1–12 )

Type locality. India, Sikkim, West Sikkim District, Rimbi waterfalls.

Type material. HOLOTYPE: J (apterous), INDIA: SIKKIM: West Sikkim, Rimbi waterfalls, 27.314035°N, 88.186561°E, alt. 4153 ft [= 1266 m a.s.l.], 11.v.2015, coll: S. Basu.The specimen is deposited in the National Zoological Collection of Zoological Survey of India, Kolkata (NZC-ZSI).

Description. Male (apterous). Body. Body length 11.15 mm, maximum width across mesoacetabula 2.67 mm.

Colour. Dorsally body colour mainly black, covered with golden pubescence. Head black, with ‘v’-shaped brown mark pointing towards posterior margin. Eyes, abdominal tergites black. Antennae and legs brown. Pronotum with a long median brown marking extending from anterior to posterior end. Meso- and metanotum black with typical dark brown markings as in Fig.1 . Ventral coloration mainly black except for dark brown head, prosternum, and 8 th abdominal sternite.

Structure. Head length 1.76 mm and width across eyes 1.49 mm, longer than broad, wide posteriorly. Interocular width 1.14 mm. Eyes distinct, black and ‘bean’ shaped, length 0.78 mm and width 0.51 mm. Antennae long, slender, without tubercles; length of antennal segments 1 st to 4 th (mm): 3.97: 3.39: 2.03: 2.33; first antennal segment longer than rest. Rostrum long, 3.52 mm in length, reaching beyond the forecoxa. Pronotum broader than long, length 1.44 mm and width 1.69 mm, shorter than head length and with a distinct median ridge, stretching from anterior to posterior end. Total length of meso- and metanotum 3.39 mm and width 2.29 mm, with distinct carination ( Fig. 3 ). Fore femur ( Fig. 6 ) slender, without any modification, slightly incrassate basally, near margin of trochanter, fringed with short hairs along exterior margin, width of fore femur 0.45 mm. Fore tarsus dark brown, covered with numerous short setae, fore claws stout and distinct. Middle and hind legs long, slender and thickened proximally. Hind femur with numerous prominent denticles on inner margin. Claws well-developed, stout and sharply bent, length of fore, middle and hind claws 0.22: 0.26: 0.27 mm. Lengths of leg segments as provided in Table 1. Abdomen long, tergites I–VIII black to dark brown, elongated. Tergites I–VII covered with short golden setae, length of abdomen 4.90 mm and width 1.77 mm. Abdominal ventrites slightly depressed from 6 th to 8 th segment, posterior margin of 7 th –8 th segment moderately emarginated in middle, covered with long, brown hairs. Segment 8 relatively long with minute notch, projecting outward near posteromedial margin.

Male genitalia. Genital segments relatively large and modified, length 1.64 mm, width 0.90 mm. Proctiger ( Fig. 11 ) distinctly bilobed, elongate, fringed with brush-like hairs, broad at both ends and with straight outer margin in middle. Dissected 8 th segment ( Fig. 10 ) of male with round posterior margin. Pygophore ( Fig. 9 ) broad with pair of long curved outer projections, dorsally with long, dense patch of bristle-like hairs. Lateral view of pygophore as in Fig. 8 , density of hairs increasing posteriorly. Paramere ( Fig. 9 ) short, distinct, clove-shaped with blunt apex and without hairs. Dorsal view of the well developed endosomal sclerite as in Fig. 12 .

Male (macropterous) and female. Unknown.

Differential diagnosis. The new species is closely related to Eotrechus kalidasa Kirkaldy, 1902 , known from Burma and Assam, and possesses a very similar structure in regard to the fore femur, abdominal apex and pygophore. It can, however, be distinguished from other Indian congeners by the elongate, dark body; long antennae; slender and simple fore femur without any modifications; much longer sternum 7; broad pygophore, with a blunter apex when viewed laterally, and fringed with long hairs throughout, with the density of these hairs increasing apically; by the structure of proctiger, which is more elongate and distinctly bilobed; and the shape of the paramere, which is ‘clove’ shaped, without any hairs, and terminates in a blunt apex.

Eotrechus fuscus is similar to E. kalidasa in possessing a rather large and well-developed male paramere, although this structure is of a different shape in the two species, being stouter basally and less expanded distally in E. fuscus . In addition, the shape of the lateral process on the pygophore, when viewed laterally ( Fig. 8 ), is thicker and somewhat more curved in E. fuscus than in E. kalidasa . Finally, the proctiger of E. fuscus , when viewed dorsally ( Fig. 11 ), has small, angulate lateral lobes that are missing in E. kalidasa . These genital characters, in combination with the darker ground coloration of E. fuscus , are sufficient to separate the two species.

Etymology. The Latin adjective fuscus (- a, - um), meaning dark, refers to the dark black coloration of the species.

Habitat. The type locality is a high altitude mountainous waterfall in Sikkim, in a pristine area. This species occurred on the vertical rock surfaces of the waterfall splashed with water and covered with moss and ferns. The habitat was disturbed to collect the specimen.

Distribution. India, Sikkim, so far known only from the type locality.

Figures

Figs 1–6. Eotrachus fuscus sp. nov., apterousJ (holotype).1 – dorsal view; 2 – ventral view; 3 – head and pronotum, dorsal view; 4 – abdominal tergites; 5 – abdominal sternites; 6 – right foreleg, ventral view.

Figs 7–12. Genitalia of Eotrachus fuscus sp. nov., J (holotype). 7 – dissected genital segment, ventral view; 8 – pygophore with paramere, lateral view; 9 – pygophore, ventral view; 10 – 8th abdominal segment, ventral view; 11 –proctiger of male, dorsal view; 12 – dorsal endosomal sclerite.