Metrocoris monticola, 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 : 135-137

Metrocoris monticola , new species

( Figs. 26, 27 , 43 , 108–116 )

Material examined. Holotype (apterous male) & allotype (apterous female): VIETNAM, Lao Cai Prov., Sa Pa, Sin Chai, Sin Chai stream, site 1, coll. Tran A.D. et al., 27 October 2013, TAD1363 ( ZMHU).

Paratypes: VIETNAM: 6 males, 5 females (apt), same locality data as holotype ( ZMHU, BPBM, NHMW, ZRC) .

Diagnosis. Both sexes: body sub-ovate, ventral surface with distinct dark marks; fore femur clearly longer than mesosternum. Male: fore femur moderately slender (ratio length/width: 5.66–6.49), proximal half about as wide as distal half, ventral surface with a distinct notch near the middle, pilosity denser and longer at proximal half ( Fig. 108 ); genitalia of medium size, abdominal segment 8 clearly longer than sternum 7; pygophore simple, on ventral view apex of pygophore broadly rounded, postero-lateral surface with sparse long yellowish hairs; proctiger simple, slightly broadened at basal two-fifths, with long hairs on lateral margins ( Fig. 109 ); paramere not extending beyond genital segment but prominent, curved dorsad at distal half, apex broadened and rounded, curved outwards and posteriorly ( Figs. 110–112 ); endosoma: dorsal sclerite long and recurved proximally, apical accessory sclerite large but weakly sclerotised, lateral sclerite slender and short, thin accessory lateral sclerite present ( Figs. 113, 114 ). Female: fore femur simple and slender (ratio length/width 6.94–7.53); hind trochanter elongated, without long hairs ( Fig. 115 ); abdomen shortened, tip of abdomen not surpassing apex of hind trochanter; sternum 7 large, clearly longer than previous sterna together, constricted laterally, posterior part producing a median lobe with broadly rounded apical margin, directed dorsad, and completely enclosing genitalia on ventral view ( Fig. 116 ).

Description. Size: apterous males: length 5.80–6.00 (holotype 5.88), width 2.53–2.75 (holotype 2.66); apterous females, length 5.13–5.44 (allotype 5.13), width 2.75–2.84 (allotype 2.75).

Colour ( Figs. 26, 27 ): Apterous morph: Interocular area with dark brown mark medially. Antenna: segment 1 yellowish at proximal part and brown at distal part; segments 2–4 brown or lightly brown. Dorsum of thorax yellowish with black markings. Pronotum with median black T-shaped mark at anterior margin and confluent with two black marks on anterolateral areas, which run to propleura. Mesonotum: black mark on anterior margin connected with lateral stripes and median longitudinal stripe; lateral stripes slender, reaching posterior margin of mesonotum; sublateral marks slender broadened posteriorly, confluent with black mark on anterior margin; mesopleura with a longitudinal brown stripe. Metanotum with broad black mark running along anterior and lateral margins, confluent with medial longitudinal mark and metacetabular black marks, bordering yellowish background; metacetabula with broad black marks usually reaching posterior margin of metacetabula; 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 surface either dark brown or light brown; fore tibia and tarsus brown or dark brown. Middle and hind legs: coxae and trochanters chiefly yellowish; middle femur mostly yellow, dorsal surface with a longitudinal slender brown mark, ventral surface sometimes with indistinct longitudinal 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 addtional broad black or dark brown marks on antero-lateral and postero-lateral areas; abdominal sterna chiefly brown, terminal segments usually yellowish.

Apterous male (holotype): Head width 1.49, interocular width 0.67, eye size 0.64. Lengths of antennal segments 1–4: 2.81: 1.15: 0.95: 0.80. Pronotum length 0.55, mesonotum length 1.55. Lengths of leg segments (femur: tibia: tarsus 1: tarsus 2): fore leg: 2.72: 2.43: 0.14: 0.90; middle leg: 6.90: 4.85: 2.50: 0.41; hind leg: 7.00: 4.15: 0.35: 0.40. Fore femur: width 0.44, other characteristics as in Diagnosis above. Abdomen length on ventral view: 2.00, pregenital length 0.74; sternum 7 about as long as sterna 4–6 combined, length 0.27. Genital segments medium size: segment 8 not distinctly broadened posteriorly, length 0.58, width 0.81; characteristics of pygophore, proctiger, paramere, and endosoma as in Diagnosis above.

Apterous female (allotype): Head width 1.42; interocular width 0.64; eye size 0.63. Lengths of antennal segments 1–4: 2.30: 1.05: 0.95: 0.79. Pronotum length 0.49, mesonotum length 1.59. Lengths of leg segments: fore leg: 2.56: 2.28: 0.09: 0.86; middle leg: 6.40: 4.45: 2.45: 0.40; hind leg: 6.40: 3.75: 0.39: 0.44. Fore femur simple and slender, width 0.34. Hind coxae simple, without apical projection, hind coxa and trochanter without long hairs, length of hind trochanter 0.68. Abdominal venter length 1.53, length of tergum 7: 0.09, length of sternum 7 (caudal view): 0.92; shape of sternum 7: see Diagnosis above.

Macropterous morph unknown.

Remarks. Chen & Nieser (1993) defined the M. compar species group on the basis of the following character states: usually darkened ventral surface of the body; male fore femur slender and simple; male paramere hook-shaped or falciform; male endosoma with a long ventral sclerite; hind coxa and trochanter of female usually modified (e.g., elongated and covered with very long hairs); sternum 7 of female constricted, with a median lobe on posterior margin. Both M. monticola , new species and M. nigriventris , new species clearly belong to the M. compar species group. This new species is similar in many respects to M. nigriventris , new species, but differs from the latter by the combination of the following characteristics: longer fore femur (in M. monticola clearly longer than the mesosternum in both sexes, while in M. nigriventris only subequal to the length of the mesoternum); shape of the fore femur of the male (in M. monticola with the notch in the middle of the ventral surface more distinct); relatively larger genitalia; the shape of the male paramere; the shape of pygophore on ventral view; the pilosity of pygophore (in M. monticola with sparse hairs, in M. nigriventris with longer and denser hairs); slightly longer abdomen in the female (in M. monticola clearly surpassing the apex of hind coxae); and the median lobe of sternum 7 of female (broader in M. monticola ).

The shape of paramere of M. monticola is relatively similar to that of Metrocoris compar ( White, 1883) from India and Myanmar, and M. pardus Zettel, 2011 from Peninsular Malaysia, but other characters show significant differences between the these species: M. monticola and M. pardus are distinctly different in the colour pattern of dorsum; and the female of M. pardus has a distinctly shortened abdomen, with the apex of the abdomen only reaching the base of the hind coxa, while in the female of M. monticola the apex of the abdomen reaches the apex of the hind coxa. Comparing M. monticola and M. compar, the paramere of M. monticola has no long hairs as seen in that of the latter; M. monticola has a longer sternum 7 (about 1.5 times as long as the preceeding abdominal sterna, versus only about 1.1 times in M. compar, see Chen & Nieser, 1993). It is notable that, among taxa in the M. compar species group, M. monticola has probably the simplest hind coxa and trochanter in the female, being elongated but without significant modification and no long hairs.

Etymology. The name monticola , treated as a noun in apposition, meaning inhabiting (- cola) mountain area (monti -), is given to this species, as it was found in a montane stream.

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

Habitats. Metrocoris monticola has been collected from a small montane stream, at elevation ca. 1400 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. 108–116. Morphological features of Metrocoris monticola, new species. 108: right fore leg of male. 109: proctiger of male. 110–112: left paramere, three different views. 113, 114: endosomal sclerites, lateral and dorsal views. 115: hind coxa and trochanter of female. 116: sternum 7 of female, ventral view (110–114 same scale; 115, 116 same scale).

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