Metrocoris sapa, A.D. & Polhemus, 2017

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 : 137-139

Metrocoris sapa , new species

( Figs. 28, 29 , 117–122 )

Material examined. Holotype (apterous male) & allotype (apterous female): VIETNAM, Lao Cai Prov., Sa Pa, Hoang Lien N’Park, Nui Xe, upstream of Suoi Vang, coll. Tran A.D., 4 July 2004, TAD0416 ( ZMHU).

Paratypes: VIETNAM, Lao Cai Prov.: 1 male, 1 female (apt) , 1 male, 4 females (mpt), same locality data as holotype ( ZRC); 1 male (mpt), Sa Pa, Hoang Lien N’Park, Nui Xe, Suoi Vang, coll. Tran A.D., 4 July 2004, TAD0417 ( ZRC) .

Diagnosis. Both sexes: body sub-ovate, ventral surface light coloured ventral surface, without any dark mark; fore femur clearly longer than mesosternum. Male: fore femur moderately slender (ratio length/width: 6.60), proximal half, broader than distal half, constricted near near the middle, pilosity denser and longer at proximal half ( Fig. 117 ); genitalia small: abdominal segment 8 clearly longer than sternum 7; proctiger simple, elongated and slender; pygophore ovate on ventral view; paramere falciform, simple, curved at middle part, apex rounded and not modified ( Fig. 118 ); endosoma ( Figs. 119, 120 ): dorsal sclerite long and recurved on apical, apical accessory sclerite distinct, ventral sclerite shorter than dorsal sclerite, lateral sclerite straight, rather broad, partially sclerotised. Female: fore femur simple, not modified as in male, and slender (ratio length/width: 7.94); hind coxa and trochanter enlongated, without apical projection, interior side of hind coxa and trochanter with long hairs ( Fig. 121 ); abdominal sternum 7 broader than long, clearly longer than previous sterna together, constricted laterally, posterior part producing a median lobe with nearly straight apical margin, directed dorsad, and completely enclosing genitalia on ventral view ( Fig. 122 ).

Description. Size: apterous males: length 4.80–5.60 (holotype 5.60), width 2.48–2.97 (holotype 2.97), macropterous males: length 8.00–8.10, width 2.87; apterous females: length 4.80–5.10 (allotype 5.10), width 2.90–2.94 (allotype 2.94), macropterous females: length 8.00–8.30, width 3.00–3.04.

Colour ( Figs. 28, 29 ). Dorsal body mainly pale, light brown markings expanded and yellow markings reduced. Antennae dark brown or black, proximal part of antennal segment 1 yellowish brown. Interocular region of head mainly dark, with yellow mark on posterior margin of head. Pronotum with black anterior margin confluent with a slender median black marking, forming a T-shaped marking; antero-lateral corners with a large light brown marking, leaving the yellow markings slender along the median black marking and on posterior margin. Mesonotum with a slender median black marking, two large light brown markings along each side of median black marking, and a light brown marking on each antero-lateral corner. Metanotum with a slender median black marking, two yellow markings on each side of the median marking running along posterior margin. Abdominal terga 1–7: each tergum dark brown or black on anterior part, and yellow on posterior part. Metacetabula, inner half yellow, outer half brown to dark brown. All coxae and trochanters mainly yellow with small brown markings. Fore femur yellow with 1 brown stripe on outer side and 1 on inner side, confluent with brown apical part. Middle and hind femora mainly yellowish brown. Tibia and tarsus dark brown or black. Venter of body mainly light yellow. In macropterous form, pronotum with median T-shaped black marking on anterior margin, pronotal lobe mainly yellowish brown with lateral margin light yellow from humeri to tip of pronotal lobe, wings mainly brown.

Apterous male (holotype): Head width 1.59, interocular width 0.67, eye size 0.75. Lengths of antennal segments 1–4: 2.54: 1.17: 1.03: 0.71, antennal segment 2 with scattered spines. Pronotum length 0.49, mesonotum length 1.58. Lengths of leg segments (femur: tibia: tarsus 1: tarsus 2): fore leg: 2.64: 2.51: 0.08: 0.86; middle leg: 7.30: 5.45: 2.51: 0.35; hind leg: 7.80: 4.61: 0.35: 0.44. Fore femur: width 0.40, other characteristics as in Diagnosis above. Abdomen length on ventral view: 1.71, pregenital length 0.83; sternum 7 slightly longer than sterna 5 and 6 combined, length 0.27. Genital segments small: segment 8 sub-rectangular on dorsal view, length 0.44, width 0.56; characteristics of pygophore, proctiger, paramere, and endosoma as in Diagnosis above.

Apterous female (allotype): Head width 1.64, interocular width 0.65, eye size 0.78. Lengths of antennal segments 1–4: 2.23: 1.06: 1.03: 0.71, antennal segment 1 with scattered spines. Pronotum length 0.44, mesonotum length 1.70. Lengths of leg segments: fore leg: 2.54: 2.38: 0.08: 0.83; middle leg: 7.00: 5.10: 2.35: 0.33; hind leg: 7.30: 4.56: 0.32: 0.42. Fore femur: width 0.32, other characteristics as in Diagnosis above. Hind coxae without apical projection, length of hind trochanter 0.76, interior side of hind coxa and trochanter with long hairs ( Fig. 121 ). Abdominal venter length 1.08. Abdominal sternum 7 broader than long, length ca. 0.98 (caudal view), shape of sternum 7: see Diagnosis above.

Macropterous male: head width 1.56, interocular width 0.63, eye size 0.70. Lengths of antennal segments: 2.48: 1.17: 0.98: 0.71. Pronotum length 3.30, humeral width 2.48. Fore wing length 6.40. Lengths of leg segments: fore leg: 2.48: 2.44: 0.10: 0.79; middle leg: 7.10: 5.15: 2.33: 0.35; hind leg: 7.30: 4.26: 0.32: 0.40. Margin of connexivum with long hairs. Other characteristics similar to apterous male.

Macropterous female: head with 1.52, interocular width 0.63, eye size 0.71. Lengths of antennal segments: 2.08: 0.90: 0.95: 0.68. Pronotum length 3.45, humeral width 2.48. Fore wing length 6.30. Lengths of leg segments: fore leg: 2.48: 2.31: 0.08: 0.76; middle leg: 6.30: 4.70: 2.38: 0.35; hind leg: 6.80: 4.17: 0.35: 0.44. Margin of connexivum with long hairs. Other characteristics similar to apterous female.

Remarks. Based on the definition of M. compar species group (sensu Chen & Nieser, 1993, see Remarks under M. monticola , new species), we can assign also M. sapa , new species to the M. compar species group. However, M. sapa does not totally fit the diagnostic characteristics of this group because it has a light coloured ventral surface, without any dark markings.

Metrocoris sapa , new species is most similar to M. hirtus Chen & Nieser, 1993 (from Sichuan, China) in having a similar general shape of the male parameres, endosomal structures and female hind coxa. The dorsal colour pattern of M. sapa is similar to that of M. pardus Zettel, 2011 (from Peninsular Malaysia). However, the apex of the paramere in M. sapa is rounded, simple and not modified like those of M. hirtus or M. pardus (see Chen & Nieser, 1993: Fig. 195; Zettel, 2011: Fig. 8 ). This species can also be distinguished from all other species of the M. compar group by the combination of following characters: apex of paramere rounded and not modified; endosoma with the apical sclerite more developed, lateral sclerite indistinct, ventral sclerite shorter; median lobe of sternum 7 of female with rounded apex; hind coxa of female with less dense pilosity and with the apex not produced.

The discoveries of M. nigriventris , M. monticola , and M. sapa have raised the total number of species in the M. compar group to nine, and they are also the first records of this group in Vietnam. Other previously known species have been found in India, Nepal, Myanmar, China, and Peninsular Malaysia ( Chen & Nieser, 1993; Chen, 1994; Zettel, 2011).

Etymology. This species is named after its type locality, Sa Pa. The word “ sapa ” is used here specifically as a noun in apposition.

Distribution. Vietnam: Lao Cai ( Fig. 141 ).

Habitats. Metrocoris sapa was collected from a montane stream, at elevations between 1800 and 1900 m. It was found in association with M. quynhi and M. acutus , both of which are much larger species. Due to the small size and pale dorsal colour of living specimens in this new species, it may superficially resemble nymphs of other Metrocoris species.

Figures

Figs. 18–31. Dorsal colour patterns of Metrocoris species. 18, 19: M. inthanon, specimens from Vietnam, Nghe An Prov., Pu Mat Nature Reserve (CL 4385). 20, 21: M. sicilis, new species, paratypes, from Vietnam, Hanoi, Ba Vi N’Park (CL 4393). 22, 23: M. triangulatus, specimens from Vietnam, Kontum Prov., 60 km NW. of Kontum (CL 4280). 24, 25: M. nigriventris, new species, paratypes, from Vietnam, Lai Chau Prov., 12 km N. of Lai Chau (CL 4410). 26, 27: M. monticola, new species, paratypes, from Vietnam, Lao Cai Prov., Sa Pa, Sin Chai (TAD1363). 28, 29: M. sapa, new species, paratypes, from Vietnam, Lao Cai Prov., Sa Pa, Nui Xe (TAD0416). 30, 31: M. tenuicornis, specimens from Vietnam, Gia Lai Prov., 60 km N. of An Khe (CL 4309).

Figs. 117–122. Morphological features of Metrocoris sapa, new species. 117: right fore leg of male. 118: left paramere. 119, 120: endosomal sclerites, lateral and dorsal views. 121: hind coxa and trochanter of female. 122: sternum 7 of female, ventral view (121, 122 same scale).

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).

Fig. 141. Distribution records in Vietnam of Metrocoris nigriventris, new species, M. monticola, new species, M. sapa, new species, and M. tenuicornis.