Metrocoris obscurus Chen & Nieser, 1993 (Figs. 12, 13, 36, 71–73) Metrocoris obscurus Chen & Nieser, 1993: 27–29, Figs. 70, 71, 76, 84 (type locality: Bumgahtauang-Hpungan, Myanmar). Material examined. VIETNAM, Lao Cai Prov.: 2 males, 5 females (apt), stream in open valley, 4 km NE. of Sa Pa on Lao Cai road, 1250 m asl, 22°21′10″N, 103°52′12″E, water temp. 24°C, 9 April 2000, 1630–1700 hrs., CL 4407, coll. D.A. Polhemus, J.T. Polhemus & P. Nguyen (USNM); Cao Bang Prov.: 1 male, 3 females (apt), Bao Lac, Dinh Phung commune, near Tung Muu, stream by the Nat’ road 34, coll. Tran A.D. et al., 20 December 2013, TAD1378 (ZMHU). Diagnosis. Male: fore femur incrassate (ratio length/width 3.22–3.67), ventral margin sinuate on distal half (widest at ca. distal half), with a single apical tooth; inner surface of tibia without sub-basal elevation (Fig. 71). Male genitalia: abdominal segment 8 large, ventral side about as long as wide; pygophore long, with apical margin broadly rounded, dorsolateral process of pygophore short and directed dorsad; proctiger long, with narrow distal half; paramere sharply bent on distal one-third, with broadly rounded tumescence subapically on outer margin (Fig. 72); endosoma as in Chen & Nieser (1993: Fig. 84). Female: body dorsoventrally compressed; sternum 7 large, length along midline about same as length of preceding abdominal sterna combined; posterior sternum 7 with two small and finger-like lobes, separated by wide, shallow, transverse notch (Fig. 73). Size: apterous males: length 6.2–6.9, width 3.05–3.45; apterous females: length 5.9–6.1, width 3.35–3.48. Remarks. Metrocoris obscurus belongs to the M. obscurus species group (sensu Chen & Nieser, 1993) and is the only taxon in this species group. The specimens from Vietnam are slightly larger than the type specimens from Myanmar and China (see Chen & Nieser, 1993). Distribution. Vietnam (first record): Lao Cai, Cao Bang (Fig. 139). Extralimital records: Myanmar: Bumgahtauang-Hpungan; China: Yunnan.

Published as part of A. D., Tran & Polhemus, D. A., 2017, The genus Metrocoris Mayr, 1865 (Gerromorpha: Gerridae) in Vietnam, with descriptions of five new species, pp. 109-149 in Raffles Bulletin of Zoology 65 on page 123, DOI: 10.5281/zenodo.4502634