Metrocoris nigriventris, 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 : 133-135

Metrocoris nigriventris , new species

( Figs. 24, 25 , 42 , 100–107 )

Material examined. Holotype (apterous male) and allotype (apterous female): VIETNAM, Lao Cai Prov., Sa Pa, Thanh Phu, near junction of Nam Cang and Muong Hoa streams, coll. Dinh N.H. et al., 23 October 2012, DNH12.06 ( ZMHU).

Paratypes: VIETNAM: Lao Cai Prov.: 1 male, 3 females (apt), same locality data as holotype ( ZMHU) ; 1 male (apt), Sa Pa, Ban Ho, Nam Pu stream 2, coll. Dinh N.H. et al., 22 October 2012, DNH12.02 ( ZRC) ; 1 female (apt), Sa Pa, Seo Trung Ho stream, coll. Dinh N.H. et al., 22 October 2012, DNH12.05 ( ZRC) ; 1 male (apt), Sa Pa, Nam Cang, Nam Cang stream, coll. Dinh N.H. et al., 23 October 2012, DNH12.08 ( ZMHU) ; 1 female (apt), Sa Pa, Nam Sai, Seo Nam Sai stream 1, coll. Dinh N.H. et al., 24 October 2012, DNH12.09 ( ZMHU) ; 3 males, 2 females (apt), rocky river and tributary 7 km NE. of Sa Pa on Lao Cai road, 1220 m asl, 22°22′19″N, 103°52′16″E, water temp. 17°C, 7 April 2000, 0830–1000 hrs., CL 4395, coll. D.A. Polhemus, J.T. Polhemus & P. Nguyen ( USNM, BPBM) ; 5 males, 1 females (apt), 1 male (mpt), rocky river and small trib., 16 km NE. of Sa Pa on Lao Cai road, 850 m asl, 22°24′52″N, 103°53′51″E, water temp. 19°C (main river), 7 April 2000, 1115–1400 hrs.; 9 April 2000, 1500–1600 hrs., CL 4397, coll. D.A. Polhemus, J.T. Polhemus & P. Nguyen ( USNM, BPBM) ; 4 males, 2 females (apt), 1 female (mpt), small rocky stream 19 km NE. of Sa Pa on Lao Cai road, 595 m asl, 22°25′39″N, 103°55′00″E, water temp. 20°C, 7 April 2000, 1515–1600 hrs., CL 4399, coll. D.A. Polhemus, J.T. Polhemus & P. Nguyen ( USNM, BPBM) ; 5 males, 3 females (apt), cascading stream 20 km NE. of Sa Pa on Lao Cai road, 565 m asl, 22°26′20″N, 103°55′36″E, water temp. 19°C, 9 April 2000, 1215–1430 hrs., CL 4406, coll. D.A. Polhemus, J.T. Polhemus & P. Nguyen ( USNM, BPBM) . Lai Chau Prov.: 2 males, 3 females (apt) , 3 males (mpt), cascading stream 12 km N. of Lai Chau , 290 m asl, 22°07′19″N, 103°11′30″E, water temp. 22°C, 11 April 2000, 1345–1600 hrs., CL 4410, coll. D.A. Polhemus, J.T. Polhemus & P. Nguyen ( USNM, BPBM) . Phu Tho Prov.: 1 male (apt), Xuan Son N’Park, Lap stream, site 1, at Ngoc waterfall, coll. Nguyen T.S. et al., 27 August 2014, TS1409 ( ZMHU) ; 1 male (mpt), Xuan Son N’Park, Lap stream, site 1, at Ngoc waterfall, coll. Nguyen T.S. et al., 23 May 2015, TS1511 ( ZMHU) .

Diagnosis. Both sexes: body sub-ovate, ventral surface with distinct dark marks; fore femur relatively short, about subequal to length of mesosternum) slender (ratio length/ width: males, 5.12–6.40; females, 6.34–6.98); in males, proximal half of fore femur about as wide as distal half, ventral surface slightly notched near the middle ( Fig. 100 ), pilosity denser and longer at proximal half (in females, fore femur simple). Male: genitalia of medium size, abdominal segment 8 longer than wide and clearly longer than sternum 7; pygophore simple, on ventral view apex of pygophore straight, postero-lateral surface covered with long yellowish hairs; proctiger simple, lateral margins almost parallel, with long hairs on lateral margins; paramere not extending beyond genital segment, hook-shaped, curved dorsad at distal one-third, with apex projected outwards and anteriorly ( Figs. 101–103 ); endosoma ( Figs. 104, 105 ): dorsal sclerite long and recurved proximally, apical accessory sclerite large but weakly sclerotised, lateral sclerite broad and short, thin accessory lateral sclerite present. Female: hind trochanter produced posteriorly, forming a small process with some long hairs ( Fig. 106 ); abdomen shortened, tip of abdomen barely surpassing apex of hind coxa; sternum 7 large, clearly longer than previous sterna together, constricted laterally, posterior part producing a median lobe with rounded apical margin, directed dorsad, and completely enclosing genitalia on ventral view ( Fig. 107 ).

Description. Size: apterous males: length 4.75–5.31 (holotype 5.13), width 2.25–2.63 (holotype 2.41), macropterous males: length 6.00–6.45, width 2.22–2.45; apterous females: length 4.34–5.19 (allotype 4.70), width 2.36–2.66 (allotype 2.45), macropterous females: length 6.80, width 2.50.

Colour ( Figs. 24, 25 ): Apterous morph: Interocular area with dark brown mark medially. Antenna: segment 1 yellowish at proximal half and brown at distal half; segments 2–4 brown. Dorsum of thorax yellowish with black markings. Pronotum with median black T-shaped mark at anterior margin and confluent with two lateral black marks which run to propleura. Mesonotum: black mark on anterior margin slender and connected with lateral stripes and median longitudinal stripe; lateral stripes slender, reaching posterior margin of mesonotum; sublateral marks slender anteriorly and broadened posteriorly, confluent with black mark on anterior margin (sublateral marks sometimes variable, indistinct); mesopleura with a longitudinal brown stripe. Metanotum with broad black mark running along anterior and lateral margins, confluent with medial longitudinal mark and metacetabular stripes, bordering yellowish background; metacetabular stripes black, slender and short, about half of metacetabular length; yellow areas on meso- and metacetabula covered with silvery pubescence. Fore femur with apical dark ring and a distinct longitudinal mark on external side usually connected with ring, inner and ventral side chiefly brown; fore tibia and tarsus dark brown. Middle and hind legs: coxae and trochanters chiefly yellowish; middle femur mostly yellow, dorsal and ventral surface each with a longitudinal slender brown mark; hind femur only yellowish proximally; tibiae and tarsi dark brown. Abdomen mostly black dorsally. Venter of body with distinct dark marks: pro-, meso-, and metasternum with broad longitudinal black mark medially; mesosternum with additional broad black or dark brown marks on antero-lateral and postero-lateral areas; abdominal sterna chiefly brown, genital segment usually yellowish. Macropterous morph: Pronotum with dark mark on anterior margin, confluent with the median longitudinal stripe, and connected with dark mark on lateral area between anterior corner and humeri; two brown sublateral marks running toward apex of protonal lobe usually confluent with the median stripe posteriorly; posterior margin between humeri and apex light yellowish. Fore wings chiefly dark brown, posterior part of wings light brown.

Apterous male (holotype): Head width 1.32, interocular width 0.67, eye size 0.56. Lengths of antennal segments 1–4: 2.06: 0.90: 0.85: 0.70. Pronotum length 0.55, mesonotum length 1.32. Lengths of leg segments (femur: tibia: tarsus 1: tarsus 2): fore leg: 2.05: 1.80: 0.09: 0.67; middle leg: 5.19: 3.50: 1.90: 0.34; hind leg: 5.00: 2.78: 0.30: 0.38. Fore femur: width 0.32, other characteristics as in Diagnosis above. Abdomen length on ventral view: 1.71, pregenital length 0.68; sternum 7 about as long as sterna 3–6 combined, length 0.28. Genital segments medium size: segment 8 broadened posteriorly, length 0.49, width 0.61; characteristics of pygophore, proctiger, paramere, and endosoma as in Diagnosis above.

Apterous female (allotype): Head width 1.33; interocular width 0.59; eye size 0.58. Lengths of antennal segments 1–4: 1.90: 0.81: 0.86: 0.71. Pronotum length 0.45, mesonotum length 1.57. Lengths of leg segments: fore leg: 2.03: 1.75: 0.11: 0.67; middle leg: 5.06: 3.43: 2.00: 0.34; hind leg: 4.90: 2.66: 0.29: 0.40. Fore femur slender, width 0.32. Hind coxae simple, without apical projection, hind trochanter produced posteriorly, forming a small process with some long hairs, length of hind trochanter 0.70. Abdominal venter length 1.32, length of tergum 7: 0.20, length of sternum 7 (caudal view): 0.72. Shape of sternum 7: see Diagnosis above. Connexival margin with scattered long hairs.

Macropterous male: Head width 1.35, interocular width 0.63, eye size 0.60. Lengths of antennal segments 1–4: 2.05: 0.92: 0.87: 0.72. Pronotum: apex of pronotal lobe rounded, median length 3.03, humeral width 2.25. Fore wing length 4.9. Lengths of leg segments: fore leg: 2.18: 1.75: 0.11: 0.72; middle leg: 5.19: 3.75: 2.13: 0.38; hind leg: 5.19: 2.97: 0.30: 0.42. Fore femur: width 0.38. Abdomen length on ventral view: 1.95, pregenital length 0.72; sternum 7 about as long as sterna 3–6 combined, length 0.27. Abdominal segment 8: length 0.63, width 0.65. Other characteristics as in apterous males.

Macropterous female: Head width 1.35, interocular width 0.63, eye size 0.58. Lengths of antennal segments 1–4: 1.83: 0.83: 0.90: 0.72. Pronotum: apex of pronotal lobe rounded, median length 3.20, humeral width 2.35. Fore wing length 5.25. Lengths of leg segments: fore leg: 2.15: 1.95: 0.11: 0.72; middle leg: 5.38: 3.60: 2.18: 0.37; hind leg: 5.25: 2.78: 0.32: 0.42. Fore femur as slender as in apterous female, width: 0.32. Abdominal venter length 1.08, length of sternum 7: 0.76. Other characteristics as in apterous females.

Remarks. See Remarks under Metrocoris monticola , new species.

Etymology. This species epithet refers to the extensive black marks on ventral surface of the body, a character state usually present in members of the M. compar species group.

Distribution. Vietnam: Lao Cai, Lai Chau, Phu Tho ( Fig. 141 ).

Habitats. Metrocoris nigriventris , new species has been collected from montane streams, at elevations ranging from 290 to 1220 m.

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. 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. 100–107. Morphological features of Metrocoris nigriventris, new species. 100: right fore leg of male. 101–103: left paramere, three different views. 104, 105: endosomal sclerites, lateral and dorsal views. 106: hind coxa and trochanter of female. 107: sternum 7 of female, ventral view (101–105 same scale; 106, 107 same scale).

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