Onychotrechus dooarsicus, Subramanian, K. A., Basu, Srimoyee & Zettel, Herbert, 2014

Subramanian, K. A., Basu, Srimoyee & Zettel, Herbert, 2014, A new species of Onychotrechus Kirkaldy, 1903 (Hemiptera, Heteroptera, Gerridae) from Dooars, West Bengal, India, and a key to males of all species, Deutsche Entomologische Zeitschrift 62 (2), pp. 133-139 : 133-135

Taxon classification Animalia Hemiptera Gerridae

Onychotrechus dooarsicus sp. n. Figs 1-19

Holotype

(apterous male): INDIA: West Bengal; Jalpaiguri; Buxa Jhora near Buxa fort; Buxa Tiger Reserve, 26.76223° N, 89.59968° E, 630 m a. s. l., 19.IV.2013, Srimoyee Basu (Reg. No.: 3130/H15). Paratypes: one apterous male, one apterous female, same data as holotype (Reg. No.: 3131/H15).

Type locality.

INDIA: West Bengal; Jalpaiguri; Buxa Jhora near Buxa fort; Buxa Tiger Reserve; stream with large rocks, stones in forested areas.

Description of apterous male

(Fig. 1). Size: Body length (from head tip to tip of proctiger) of apterous male holotype 3.30, male paratype 3.27; maximum width of body across mesoacetabula 1.12 (holotype), 1.07 (paratype).

Colour: Body dorsally black with yellow markings. Head with a median yellow longitudinal stripe, which ends in a blunt arrow head (Fig. 3); head anteriorly and along medial and posterior eye margins yellow. Antenna and leg segments yellowish brown. Pronotum with two broad yellow sub-lateral stripes, a thin median yellow stripe, and two yellow curved lateral stripes. Meso- and metanotum (Fig. 4) with two thin lateral stripes, two broad sub-lateral stripes and an indistinct short yellow median line. Abdominal tergites completely black (Figs 4, 12). Forefemur yellow with one broad dark band on dorsal side and one very slender dark brown band on extensor side. Venter yellow. Mesosternum (Fig. 6) with paired black patches behind forecoxae and metasternum posteriorly with an almost W-shaped broad dark region. Abdominal sternites pale yellowish brown (Fig. 13).

Structural characteristics

(measurements refer to holotype). Head length 0.64, width 0.89. Interocular width 2 times as large as eye width (0.45: 0.22). Eye length 0.44. Length of antennal segments 1-4: 0.96, 0.94, 0.89, 1.38; first antennomere with three spines distally, being two long, and a small one arising near base of first spine. Rostrum reaching up to mid-way of mesosternum, length 1.50.

Pronotum 0.84 mm in width; pronotum length 0.53, width 0.79. Combined length of mesonotum and metanotum 1.12, width 0.98. Mesosternum (Fig. 6) modified, with narrow median groove slightly widened posteriorly; depression with black, scattered setae directed to its centre; posterior swelling with densely arranged long stout black setae covering base of mesosternum. Forefemur (Fig. 8) slender, widened basally, but almost evenly tapering apically; length of forefemur 1.17, width 0.25; forefemur apically with a few setae and with short dark stiff setae distributed throughout. Foretibia (Fig. 9) strongly curved, basally with patch of few short setae on flexor side; a soft spinous structure protruded outwards from base of curvature; apical region with two prominent black spines that diverge from almost touching bases (forming a ‘V’), and with four black spines and a row of short setae towards extensor side. Mid and hind femora slender, each about 1.1 times as long as body; both with distinct rows of short spines arranged equidistantly. Foreclaws (Fig. 11) sharply bent and slightly longer than mid and hind claws. Measurements of leg segments provided in Table 1.

Abdomen (Figs 12, 13) short, only about one third of body length. Length of abdominal sternites 1.01, width 0.90. Sterna II-VI visible as very narrow curved strips; sternum VII (Fig. 13) much longer; sterna II-VII without median groove. Segment VIII broad, with median depression, posterior part with several setae, bluntly ending.

Genitalia (Figs 16-19): Pygophore sub-oval, slightly elongated, widened basally. Proctiger (Fig. 17) short, widened distally, gradually tapering towards basal part, with long setae and medially with numerous punctures. Endosomal sclerites as in Fig. 18. Paramere (Fig. 19) short, simple and with a distinct median notch.

Description of apterous female

(Figs 2, 7). Size: Body length 4.4; maximum body width across mesoacetabula 1.38.

Colour: Almost identical to male, with the following exceptions: posterior yellow mid-line lacking from metanotum (Fig. 5). Venter yellow, with two broad markings on mesosternum. Metasternum brownish yellow. Abdominal sterna II-VI yellowish brown, paler at mid-line and sides; sternum VII black anteriorly, yellowish posteriorly.

Structural characteristics : Length of head 0.75, width 0.91. Interocular width 0.52. Eye length 0.42, width 0.23. Length of pronotum 0.51, width 0.85. Length of antennal segments 1-4: 1.10, 1.08, 1.04, 1.48. Combined length of meso- and metanotum 1.38, width 1.36. Forefemur slender (Fig. 10). Foretibia less curved, without spinous protrusion from curvature. Measurements of leg segments provided in Table 1. Abdominal tergites (Fig. 14) elongated, densely covered by setae. Abdominal sterna II-VI with median groove; sternum VII (Fig. 15) broad, trapezoidal, concave towards end, partly concealing genitalia. Proctiger acuminate.

Macropterous male and female.

Unknown.

Comparative notes.

Onychotrechus dooarsicus sp. n. is probably a close relative of Onychotrechus jaechi , recently described from Bhutan. They share some common characters: males have almost identical pro-, meso- and metasternal markings, basally incrassate forefemora, similar mesosternal modifications and short abdominal segments. However, the male of Onychotrechus dooarsicus sp. n. distinctly differs from Onychotrechus jaechi by the following characteristics: 1) The foretibia of Onychotrechus dooarsicus sp. n. bears a patch of few short setae basally on flexor side, and a soft spinous structure protruding outwards from the base of the curvature; its apical region bears two prominent black spines (forming a ‘V’), four black spines and a row of short setae towards extensor side; whereas, in Onychotrechus jaechi its base bears a patch of long hairs on the flexor side and the distal modifications are absent. 2) The mesosternum of Onychotrechus dooarsicus sp. n. has a median narrow groove that is slightly widened posteriorly, whereas Onychotrechus jaechi has a strongly modified mesosternum, with a medial, posteriorly widened depression and a prominent transverse swelling at its hind margin. 3) In Onychotrechus dooarsicus sp. n., the paramere has a notch at mid-length, that is absent from Onychotrechus jaechi . The female of Onychotrechus jaechi is unknown.

Etymology.

The specific epithet ' dooarsicus’ comes from its place of occurrence, ‘Dooars’ of West Bengal. Dooars is a large region, forming the gateway from India to Bhutan and stretching from the plains of Darjeeling District, Jalpaiguri District, and the upper regions of Cooch Behar District of West Bengal to some parts of Assam. This part mainly consists of Himalayan foothills.

Habitat.

Representatives of this species have been found in the shallow zone between the rocks, splashed by a slow-flowing stream (630 m), known as Buxa Jhora, located near Buxa fort of Buxa Tiger Reserve Range.