Metrocoris johnpolhemi, 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 : 119-122

Metrocoris johnpolhemi , new species

( Figs. 7, 8 , 34 , 56–65 )

Material examined. Holotype (apterous male) & allotype (apterous female): VIETNAM: Hanoi, Ba Vi N’Park, stream near Coste 400, ca. 550 m asl, coll. Ngo Q.H. & Tran A.D., 27 April 2012, TAD1210 ( ZMHU).

Paratypes: VIETNAM: Hanoi: 11 males, 7 females (apt) , 2 males, 2 females (mpt), same locality data as holotype ( ZMHU, ZRC, NHMW) ; 3 males, 6 females (apt), Ba Vi N’Park, stream near Coste 400, ca. 550 m asl, coll. Ngo Q.H. et al., 16 December 2011, TAD1120 ( ZMHU) ; 1 female (apt), Ba Vi N’Park, Minh Quang, stream near by Tan Vien Pagoda, 340 m asl, coll. Ngo Q.H. et al., 17 December 2011, TAD1125 ( ZMHU) ; 1 female (apt), Ba Vi N’Park, nr. Son Tay, W. of Hanoi , first small stream on lower road, 575 m asl, 21°03′32″N, 105°21′12″E, water temp. 18°C, 4 April 2000, CL 4391, coll. J.T. Polhemus & P. Nguyen ( USNM) . Phu Tho Prov.: 1 male (mpt), Xuan Son N’Park, Lap stream, site 1, at Ngoc waterfall, coll. Tran A.D. et al., 5 June 2013, TAD1331 ( ZMHU) ; 1 male (apt), 1 male (mpt), Xuan Son N’Park, Kim Thuong, Tan Ong stream, site 1, at Chin Tang waterfall, coll. Tran A.D. et al., 6 June 2013, TAD1334 ( ZMHU) ; 1 male, 1 female (apt), Xuan Son N’Park, Kim Thuong, Tan Ong stream, site 1, at Chin Tang waterfall, coll. Nguyen T.S. et al., 26 August 2014, TS1401 ( ZMHU) ; 1 male, 2 females (mpt), Xuan Son N’Park, Kim Thuong, Tan Ong stream, site 1, at Chin Tang waterfall, coll. Nguyen T.S. et al., 22 May 2015, TS1503 ( ZMHU) ; 2 males, 2 females (mpt), Xuan Son N’Park, Lap stream, site 1, at Ngoc waterfall, coll. Tran A.D. et al., 23 May 2015, TS1511 ( ZMHU) . Lai Chau Prov.: 2 females (apt) , 2 males, 4 females (mpt), Nam Ceung stream, trib. to Nam Na River, 15.5 km N. of Lai Chau , 200 m asl, 22°08′52″N, 103°11′33″E, water temp. 21.5°C, 11 April 2000, 10:00–13:00 hrs., CL 4409, coll. D.A. Polhemus, J.T. Polhemus & P. Nguyen ( USNM, BPBM) ; 1 male, 2 females (apt), 3 females (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, 13:45–16:00 hrs., CL 4410, coll. D.A. Polhemus, J.T. Polhemus & P. Nguyen ( USNM, BPBM) ; 1 male, 1 female (mpt), Tam Duong, Ho Thau, stream at Su Thang brigde, km 9 Nat. Road #4D, coll. Tran A.D. et al., 31 May 2013, TAD1324 ( ZMHU) .

Diagnosis. Male: fore femur variably incrassate (ratio length/ width: 3.32–4.25, holotype: 3.32), ventral surface of fore femur in distal one-fourth with indentation and with single large sub-apical tooth; inner surface of fore tibia subbasally with tooth-like elevation ( Figs. 56, 57 ). Male genitalia large: pygophore not raised posteriorly, caudal margin broadly rounded, dorso-lateral process curved and apically blunt ( Fig. 59 ); proctiger elongate ( Fig. 60 ); paramere prominent, falciform, strongly curved, slightly expanded on distal part, apex rounded ( Figs. 34 , 61 ); endosoma ( Figs. 62, 63 ): dorsal sclerite long and recurved proximally, apical accessory sclerite small and weakly sclerotised, lateral sclerite broad and long, accessory lateral sclerite present. Female: tergum 7 subtriangular, not produced posteriorly ( Fig. 64 ); sternum 7 ( Fig. 65 ) large, distinctly longer than preceding abdominal sterna together, posterior one-third constricted and forming two widely separated lobes, apices of lobes angular, surpassing apex of proctiger in ventral view, the notch between lobes as wide as each lobe and with angular margin.

Description. Size: apterous males: length 6.32–6.72 (holotype: 6.65), width 2.85–3.05 (holotype: 3.02); macropterous males: wings 8.10–8.20, width 2.97–3.07; apterous females: length 5.19–5.70 (allotype: 5.70), width 2.93–3.17 (allotype: 3.09); macropterous females: 7.20, width 2.94–2.97.

Colour ( Figs. 7, 8 ): Apterous morph: Dorsal dark markings prominent. Interocular area with light brown mark or without dark mark. Antenna: segment 1 almost entirely yellowish or with distal part brown, segments 2–4 light brown to dark brown. Pronotum with median black T-shaped mark at anterior margin and with two dark brown or black marks near anterolateral margin. Mesonotum with black marks: lateral stripes and median longitudinal stripe slender, running toward posterior margin and connected with anterior mark; sublateral stripes slender; each side of mesopleura with a longitudinal slender brown mark, usually variable. Metanotum with black marks running along anterior and lateral margins and with a medial longitudinal mark, bordering two broad, hookshaped yellowish marks; metacetabula with black stripe, running throughout its length. Fore femur: (a) of the male with apical dark ring and four longitudinal marks of which ventral mark dark brown and connected with ring, and lateral marks dark brown, not confluent with ring, dorsal mark light brown and not confluent with ring; (b) of the female with three slender, usually light brown, longitudinal mark, one on dorsal, one on ventral and the other one on external side of femur, all not confluent with dark ring. Fore tibia yellowish at basal one-fifth or basal one-fourth, distal part dark brown; fore tarsus dark brown. Middle and hind legs: femora yellow or sometimes brownish, tibiae and tarsi dark brownish. Abdomen mainly blackish dorsally, tergum 1 with one yellowish mark posteriorly, terga 2–7: anterior halves blackish, posterior halves yellowish. Venter bright yellowish. Macropterous morph: Pronotum with black mark on anterior margin, confluent with anterolateral marks and the median longitudinal stripe; two light brown sublateral marks confluent with the median stripe; lateral margin between anterior corner and humeri dark brown; posterior margin between humeri and apex yellowish. Fore wings mainly dark brown, anterior margin yellowish.

Apterous male (holotype): Head width 1.72; interocular width 0.63; eye size 0.82. Lengths of antennal segments 1–4: 2.50: 1.05: 0.99: 0.84. Pronotum length 0.69. Mesonotum length 1.57. Lengths of leg segments: fore leg: 3.15: 2.70: 0.16: 0.93; middle leg: 7.70: 5.70: 2.60: 0.34; hind leg: 7.60: 4.53: 0.35: 0.41. Fore femur incrassate, width of femur: 0.95, ratio length/width: 3.32, black granules scattered along ventral surface; other characteristics of fore femur as in Diagnosis above ( Figs. 56, 57 ). Abdomen length on ventral view: 2.69, pregenital length 0.65; sternum 7 slightly longer than sterna 5 and 6 combined, length 0.25. Genitalia of male: Abdominal segment 8 ( Fig. 58 ): large, with posterodorsal margin strongly upcurved; posterior dorsum and lateral sides of segment bearing long hairs; postero-ventral margin bearing short, but wide lobe, ventral length 0.85, width 1.37. Characteristics of pygophore, proctiger, paramere, and endosoma as in Diagnosis above.

Apterous female (allotype): Head width 1.64; interocular width 0.61; eye size 0.77. Lengths of antennal segments 1–4: 1.83: 0.85: 0.93: 0.79. Pronotum length 0.52. Mesonotum length 1.50. Lengths of leg segments: fore leg: 2.33: 2.13: 0.15: 0.77; middle leg: 6.10: 4.50: 2.15: 0.29; hind leg: 5.90: 3.75: 0.27: 0.37. Fore femur slender, without teeth, width 0.36, ratio length/width: 6.47. Abdominal venter length 1.63, length of tergum 7: 0.43, length of sternum 7: 0.88. Shape of sternum 7: see Diagnosis above.

Macropterous male: Head width 1.71, interocular width 0.68, eye size 0.79. Lengths of antennal segments 1–4: 2.63: 1.08: 0.97: 0.90. Pronotum: apex of pronotal lobe pointed, median length 3.60, humeral width 2.75. Fore wing length 6.0. Lengths of leg segments: fore leg: 3.17: 2.69: 0.13: 0.94; middle leg: 7.60: 5.50: 2.63: 0.32; hind leg: 7.60: 4.55: 0.35: 0.39. Fore femur incrassate, ratio length/width: 3.69. Abdomen length on ventral view: 2.47, pregenital length 0.61; sternum 7 slightly longer than sterna 5 and 6 combined, length 0.25. Other characteristics as in apterous males.

Macropterous female: Head width 1.59, interocular width 0.59, eye size 0.75. Lengths of antennal segments 1–4: 1.83: 0.81: 0.90: 0.77. Pronotum: apex of pronotal lobe pointed, median length 3.30, humeral width 2.45. Fore wing length 5.72. Lengths of leg segments: fore leg: 2.35: 2.05: 0.14: 0.76; middle leg: 6.00: 4.50: 2.25: 0.30; hind leg: 6.00: 3.88: 0.31: 0.38. Fore femur as slender as in apterous female, ratio length/width: 6.71. Abdominal venter length 1.53, length of sternum 7: 0.90. Other characteristics as in apterous females.

Remarks. Metrocoris johnpolhemi , new species, belongs to the M. bilobatus species group (sensu Chen & Nieser, 1993). This new species is similar to M. bilobatus den Boer, 1965 and M. strictus Chen & Nieser, 1993 , in having the sub-apical indentation on the fore femur of the male without a proximal tooth. The shape of sternum 7 of the female in M. johnpolhemi is relatively similar to that of M. bilobatus , but they can be easily separated because in M. johnpolhemi the posterior lobes are clearly slanted outwards with pointed apices, and the notch between these lobes is wider and has a clearly angular median margin (while in the latter, the lobes are pointed posteriorly with rounded apices, and the notch between the lobes is narrower and has a rounded median margin).

In Vietnam, there are currently three known species of the M. bilobatus group, namely M. johpolhemi, new species, M. bilobatoides Chen & Nieser, 1993 , a taxon probably restricted to northern Vietnam, and M. vietnamensis Tran & Zettel, 2005 , a taxon probably restricted to central Vietnam. This new species differs from M. vietnamensis and M. bilobatoides in regard to the following structures: (1) fore femur of the male: in M. johnpolhemi there is no tooth at the proximal edge, and the sub-apical tooth is large, while the latter two species possess a small tooth at the proximal edge present together with a large sub-apical tooth; (2) the shape of paramere: in M. johnpolhemi the shaft of the paramere is expanded on the distal half with a rounded apex, while in the latter two species the shaft of the paramere tapers along its length, and has a pointed apex); (3) abdominal sternum 7 of the female: in M. johnpolhemi the distal lobes are long, surpassing the apex of the proctiger in ventral view, and the notch between the two distal lobes is wide and has an angular margin, while in M. bilobatoides the distal lobes are shorter and the notch between the lobes is narrow and angular, and in M. vietnamensis the distal lobes are also short, and the notch wide, but with a rounded margin.

Etymology. This species is dedicated to the late Dr. John T. Polhemus, in honour of his contribution to our knowledge of water bugs in Southeast Asia.

Distribution. Vietnam: Hanoi (Ba Vi), Lai Chau, Phu Tho ( Fig. 138 ).

Habitats. Specimens of M. johnpolhemi were collected from forested hill streams in several localities in northern Vietnam, at elevations ranging ca. 300–600 m above sea level.

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. 56–65. Morphological features of Metrocoris johnpolhemi, new species. 56, 57: right fore legs of male. 58: abdominal segment 8 of male, in situ, lateral view. 59: pygophore, lateral view. 60: proctiger of male. 61: left paramere. 62, 63: endosomal sclerites, lateral and dorsal views. 64: tergum 7 of female, dorsal view. 65: sternum 7 of female, ventral view (56, 57 same scale; 58, 59 same scale; 64, 65 same scale).

Fig. 138. Distribution records in Vietnam of Metrocoris stranguloides, M. bilobatoides, M. johnpolhemi, new species, and M. vietnamensis.