Metrocoris obscurus Chen & Nieser, 1993

A. D., Tran & Polhemus, D. A., 2017, The genus Metrocoris Mayr, 1865 (Gerromorpha: Gerridae) in Vietnam, with descriptions of five new species, Raffles Bulletin of Zoology 65, pp. 109-149 : 123

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.

Figures

Figs. 3–17. Dorsal colour patterns of Metrocoris species, all apterous morph. 3, 4: M. stranguloides, specimens from Vietnam, Gia Lai Prov., 60 km N. of An Khe (CL 4309). 5, 6: M. bilobatoides, specimens from Vietnam, Lao Cai Prov., 12 km NW. of Sa Pa (CL 4404). 7, 8: M. johnpolhemi, new species, specimens from Vietnam, Lai Chau Prov.; male from 12 km N. of Lai Chau (CL 4410), female from Nam Ceung stream (CL 4409). 9: M. vietnamensis, paratype, from Vietnam, Da Nang Prov., Ba Na - Nui Chua (TAD0334) (9 reproduced and modified from Tran & Zettel, 2005). 10, 11: M. quynhi, specimens from Vietnam, Lao Cai Prov., 18 km NW. of Sa Pa (CL 4400). 12, 13: M. obscurus, specimens from Vietnam, Lao Cai Prov., 4 km NE. of Sa Pa (CL 4407). 14, 15: M. acutus, specimens from Vietnam, Hai Hung Prov., 22 km N. of Chi Linh (CL 4375). 16, 17: M. nigrofascioides, specimens from Vietnam, Binh Dinh Prov., An Khe Pass (CL 4291).

Figs. 32–43. Parameres of Metrocoris species. 32: M. stranguloides, specimen from Vietnam, Gia Lai Prov., 60 km N. of An Khe (CL 4309). 33: M. bilobatoides, specimen from Vietnam, Lao Cai Prov., 12 km NW. of Sa Pa (CL 4404). 34: M. johnpolhemi, new species, specimen from Vietnam, Lai Chau Prov., Nam Ceung stream (CL 4409). 35: M. quynhi, specimen from Vietnam, Lao Cai Prov., 18 km NW. of Sa Pa (CL 4400). 36: M. obscurus, specimen from Vietnam, Lao Cai Prov., 4 km NE. of Sa Pa (CL 4407). 37: M. acutus, specimen from Vietnam, Hai Hung Prov., 22 km N. of Chi Linh (CL 4375). 38: M. nigrofascioides, specimen from Vietnam, Binh Dinh Prov., An Khe Pass (CL 4291). 39: M. sicilis, new species, specimen from Vietnam, Hanoi, Ba Vi N’Park (CL 4393). 40: M. triangulatus, specimen from Vietnam, Gia Lai Prov., N. of Tram Lap (ROM-961066). 41: M. ciliatus, paratype, from Vietnam, Lai Chau Prov., Muong Te (TAD1329). 42: M. nigriventris, new species, paratype, from Vietnam, Lao Cai Prov., 20 km NE. of Sa Pa (CL 4406). 43: M. monticola, new species, paratype, from Vietnam, Lao Cai Prov., Sa Pa, Sin Chai (TAD1363).

Figs. 66–73. Morphological features of Metrocoris species. 66–70: M. quynhi (65–70 reproduced from Tran & Zettel, 2005). 66: right fore leg of male. 67: pygophore, lateral view. 68: male genital capsule, dorsal view. 69: left paramere. 70: female sternum 7, in situ. 71–73: M. obscurus. 71: right fore leg of male. 72: left paramere. 73: sternum 7 of female, ventral view (66, 71 same scale; 67, 68 same scale; 69, 72 same scale; 70, 73 same scale).

Figs. 74–79. Morphological features of Metrocoris species. 74–76: M. acutus. 74, 75: right fore legs of male, same scale. 76: sternum 7 of female, ventral view. 77–79: M. nigrofascioides. 77: right fore leg of male. 78: hind trochanter of female. 79: sternum 7 of female, ventral view (74, 75, 77 same scale; 76, 78, 79 same scale).

Figs. 80–90. Morphological features of Metrocoris species. 80–83: M. ciliatus, macropterous male. 80: right fore leg. 81, 82: left paramere, two different views. 83: endosomal sclerites, lateral view. 84, 85: M. inthanon. 84: right fore leg of male. 85: apex of abdomen, female, ventral view. 86–90: M. triangulatus. 86–89: male holotype. 86: A, right fore leg. 87: left paramere. 88, 89: endosomal sclerites, lateral and dorsal views. 90: abdomen of female, ventral view (80, 84, 86 same scale; 81–83 same scale; 85, 90 same scale).

Fig. 139. Distribution records in Vietnam of Metrocoris obscurus, M. quynhi, M. acutus, and M. nigrofascioides.