Onychotrechus jaechi, Zettel, Herbert & Duc, Tran Anh, 2007

Zettel, Herbert & Duc, Tran Anh, 2007, On Gerridae (Insecta: Heteroptera) from Bhutan, with description of a new species of Onychotrechus Kirkaldy, 1903, Zootaxa 1467, pp. 43-49 : 44-46

Description of Onychotrechus jaechi sp.n.

( Figs. 1–5, 7, 8, 10 )

Material examined. Holotype (apterous male), " BHUTAN: Sarpang Prov.\ Geylephug – Shempang rd.\ 10km NNE Geylephug, 400m \ 26°56’43”N 90°31’29”E \ 26.11.2005, leg. M. Jäch (29)", in the Natural History Museum Vienna.

Type locality. Bhutan, Sarpang Province, along road between Geylephug and Shempang, ca. 10 km NNE Geylephug, 26°56’43”N 90°31’29”E, alt. ca. 400 m a.s.l., creek with large rock boulders in forested area ( Fig. 3 ).

Description of holotype. Size: apterous male, length 3.72, width 1.17.

Colour. Body dorsally ( Fig. 1 ) mainly blackish brown with yellow markings. Head with median longitudinal stripe and anterior part yellow except along midline. Pronotum with two broad yellow sublateral stripes and thin median stripe. Mesonotum with two sublateral stripes, median stripe not distinct. Dorsum of abdomen totally brown. Antennal and leg segments mainly dark yellow. Fore femur ( Fig. 4 ) with one broad dark brown stripe on exterior side and one slender, shorter brown stripe on extensor side. Venter yellow, mesosternum with paired black patches behind fore coxae and with the most posterior region black.

Structural characteristics. Head width 0.98, interocular width 0.51, eye size (length, dorsal view) 0.52. Lengths of antennal segments ( Fig. 1 ): 1.21: 1.13: 1.11: 1.56, first segment with three long spines on distal part. Head length 0.90, pronotum length 0.59, mesonotum length 1.24. Lengths of meso- and metasterna (in ventral view of specimen!), 1.75: 0.12. Mesosternum ( Fig. 2 ) strongly modified, with medial, posteriorly widened depression in posterior half and with strong transverse swelling at hind margin; depression with black setae directed to its centre; swelling with densely set, long, stout, black, posterodorsad directed setae covering base of metasternum. Metasternum ca. 0.21 long (median length in perpendicular view!), oriented almost vertically, forming a step between mesosternum and base of abdomen ( Fig. 2 ). Lengths of leg segments (femur: tibia: tarsal segment 1: tarsal segment 2): fore leg: 1.43: 1.19: 0.13: 0.27; middle leg: 4.61: 3.27: 0.19: 0.43; hind leg: 4.39: 3.14: 0.19: 0.38. Fore femur ( Fig. 4 ) incrassate basally and tapering towards apex, width of fore femur 0.31; fore tibia ( Fig. 4 ) strongly curved, basal part with patch of long hairs on flexor side. Middle and hind femora slender and longer than body length ( Fig. 1 ); spines on middle femur scattered and not distinct. Middle and hind claws similar to each other, subequal to first tarsal segment, length of each: 0.17. Abdomen ( Fig. 2 ) very short, length of sterna 2–7 combined: 0.57; ventrally caudal opening of segment 7 fully exposed (after dissection of segment 8 and genitalia) and occupying three-fourths of that length. Abdominal sterna 2–6 visible as very narrow transverse strips, each of about 0.03 in length, all without median groove. Ventral length of abdominal segment 8: 0.30. Pygophore small, sub-oval; proctiger ( Fig. 5 ) short, apex with obtuse angle; paramere ( Figs. 7, 8 ) short, simple; endosoma structures as in Figure 10 .

Etymology. This species is named in honour of Dr. Manfred A. Jäch (Natural History Museum Vienna) who discovered this interesting species.

Remarks. Onychotrechus jaechi sp.n. is closely related to O. robustus described from northwestern India ( Andersen 1980) and recently also collected in Nepal (Assess-HKH, unpublished data). Males of both species have a basally incrassate fore femur (with distinct dark stripes; Figs. 1, 2 , 4 ), a patch of long hairs on the basal part of the flexor side of the fore tibia ( Fig. 4 ), a mesosternal impression ( Fig. 5 ), a short abdomen ( Figs. 1, 2 ), and a long hind coxa ( Fig. 1 ). However, the male of the new species can be easily separated from O. robustus by the following characteristics: The fore tibia is strongly curved ( Fig. 4 ; only basally curved in O. robustus ). The middle femur has small, less erect spines (middle femur of O. robustus with long, erect spines set in a distinct row). The posterior swelling of the mesosternum bears long black setae ( Fig. 2 ; absent in O. robustus ). The median groove of the mesosternum has long, black setae ( Fig. 2 ; short black pegs in O. robustus ). The metasternum is oriented almost vertically ( Fig. 2 ; horizontally in O. robustus ). The proctiger is short and has an obtuse apex (long and slender, with more acute apex in O. robustus ; comp. Figs. 5 and 6 ). The apex of the paramere is strongly curved mediad (flat and club-shaped in O. robustus ; comp. Figs. 7–9 ). The dorsal sclerite of the endosoma is basally strongly curved (slanted in O. robustus ; comp. Figs. 10 and 11 ). The female of O. jaechi sp.n. is so far unknown. The pattern of black stripes is much more extended in O. jaechi sp.n. ( Fig. 1 ) than described for O. robustus by Andersen (1980), but we have seen new specimens of O. robustus from India which are relatively dark in colour and not much different from O. jaechi sp.n.

Figures

FIGURES 1 – 3. Onychotrechus jaechi sp. n. (1) habitus of holotype (apterous male), dorsal view (see text for size); (2) same specimen, ventral view of body after dissection of abdominal segment 8 and genitalia; (3) small stream NNE of Geylephug, habitat of Onychotrechus jaechi sp. n. (photo: M. A. Jäch).

FIGURES 4 – 11. Morphological structures of males of Onychotrechus spp. (4) fore leg of O. jaechi sp. n.; (5) proctiger of O. jaechi sp. n., dorsal view; (6) same, of O. robustus; (7) left paramere of O. jaechi sp. n., lateral view; (8) same, ventral view; (9) same, of O. robustus, lateral view; (10) endosoma of O. jaechi sp. n., lateral view; (11) same, of O. robustus.