Metrocoris sicilis, 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 : 131-133

Metrocoris sicilis , new species

( Figs. 20, 21 , 39 , 94–99 )

Material examined. Holotype (apterous male) and allotype (apterous female): VIETNAM: Hanoi, Ba Vi N’Park, stream near Coste 400, ca. 550 m asl, coll. Ngo Q.H. et al., 16 December 2011, TAD1120 ( ZMHU).

Paratypes: VIETNAM: Hanoi: 2 males, 6 females (apt), same locality data as Holotype ( ZMHU) ; 2 males, 2 females (apt), Ba Vi N’Park , small creek by main road to summit, ca. 9.5 km from park head quarter, ca. 600 m asl, coll. Tran A.D., 11 June 2010, TAD1014 ( NHMW, ZRC) ; 1 male, 1 female (apt), 1 male (mpt), Ba Vi N’Park, stream near Coste 400, ca. 550 m asl, coll. Ngo Q.H. & Tran A.D., 27 April 2012, TAD1210 ( ZMHU) ; 3 males, 12 females (apt), Ba Vi N’Park , nr. Son Tay, W. of Ha Noi, third small stream on lower road, 625 m asl, vic. 21°03′32″N, 105°21′16″E, water temp. 18.5°C, 4 April 2000, CL 4393, coll. J.T. Polhemus & P. Nguyen ( USNM, BPBM) ; 3 males, 2 females (apt), Ba Vi N’Park , nr. Son Tay, W. of Hanoi, second small stream on lower road, 615 m asl, 21°03′32″N, 105°21′13″E, water temp. 18°C, 4 April 2000, CL 4392, coll. J.T. Polhemus & P. Nguyen ( USNM, BPBM) . Phu Tho Prov.: 1 male, 1 female (apt), Xuan Son N’Park, Kim Thuong, Tan Ong stream, site 3, ca. 4 km from Chin Tang waterfall, coll. Tran A.D. et al., 28 August 2013, TAD1342 ( ZMHU) .

Diagnosis. Both sexes: body dorso-ventrally compressed (more conspicuous in females); fore femur slender (ratio length/width: males, 7.43–8.44; females, 6.44–7.42), subapically constricted, ventral surface with sub-apical elevation (more prominent in males) ( Fig. 95 ). Male: antennae with dense hairs along segments 1–3 ( Fig. 94 ); pro-, meso- and metanotum, pleura, and abdominal tergum 1 with scattered black setae; genitalia small, abdominal segment 8 short, pygophore and proctiger simple, longer than wide; paramere long, falciform, curved dorsad at distal one-third, apex broadly rounded ( Figs. 39 , 96 ); endosoma dorsal sclerite long, recurved and expanded apically, apical accessory sclerite distinctly visible, lateral sclerite slender and short, two pairs of thin accessory lateral sclerites present, ventral sclerite short ( Figs. 97, 98 ). Female: thoracic segments without black setae; sternum 7 large, about as long as previous sterna together, posterior margin narrow, straight ( Fig. 99 ).

Description. Size: apterous males: length 5.43–6.00 (holotype: 5.13), width 3.09–3.52 (holotype: 2.98); macropterous male: length excluding wings 5.13 (including wings 7.28), width 3.09; apterous females: length 4.63–5.25 (allotype: 5.00), width 2.85–3.45(allotype: 3.16).

Colour ( Figs. 20, 21 ). Apterous morph: Interocular area with light brown mark or without dark mark. Antenna: segment 1 yellowish at proximal part and brown at distal part, segments 2–4 light brown to dark brown. Dorsum of thorax yellowish with usually slender blackish markings. Pronotum with median black T-shaped mark at anterior margin and confluent with two dark brown or black marks near anterolateral margin. Mesonotum: black mark on anterior margin connected with lateral stripes and median longitudinal stripe; lateral stripes running towards but not reaching posterior margin; sublateral stripes usually confluent with posterolateral marks; mesopleura with a longitudinal light brown stripe on each side. Metanotum with black mark running along anterior and lateral margins, confluent with medial longitudinal mark and metacetabular stripes, bordering broad yellowish background; metacetabular stripes black, running throughout its length. Fore femur with apical dark ring and a longitudinal mark on external side connected with ring; fore tibia and tarsus brown or dark brown. Middle and hind legs: femora mostly yellow, usually with distal part brown; tibiae and tarsi dark brown. Abdomen mainly blackish dorsally, tergum 1 with one broad yellowish mark running across width of tergum; terga 3–7: posterior part with yellow marks medially. Venter bright yellowish. Macropterous morph: Pronotum with dark mark on anterior margin, confluent with the median longitudinal stripe, but not connected with dark mark on lateral margin between anterior corner and humeri; two light brown sublateral marks running toward apex of protonal lobe but not confluent with the median stripe; posterior margin between humeri and apex light yellowish. Fore wings mainly dark brown, anterior margin yellowish, posterior part of wings light brown.

Apterous male (holotype): Head width 1.58; interocular width 0.59; eye size 0.81. Lengths of antennal segments 1–4: 3.13: 1.35: 0.99: 0.76. Pronotum length 0.38. Mesonotum length 1.53. Lengths of leg segments: fore leg: 2.60: 2.35: 0.14: 0.76; middle leg: 7.15: 5.75: 2.13: 032; hind leg: 7.15: 4.28: 0.32: 0.38. Fore femur slender, width of femur: 0.35, ratio length/width: 7.43; other characteristics of fore femur as in Diagnosis above. Abdomen length on ventral view: 1.12, pregenital length 0.54; sternum 7 slightly longer than sterna 5 and 6 combined, length 0.16. Genitalia of male: segment 8 short, length 0.27, width 0.63; characteristics of pygophore, proctiger, paramere, and endosoma as in Diagnosis above.

Apterous female (allotype): Head width 1.52; interocular width 0.54; eye size 0.77. Lengths of antennal segments 1–4: 2.05: 0.97: 0.88: 0.73. Pronotum length 0.38. Mesonotum length 1.44. Lengths of leg segments: fore leg: 2.19: 1.95: 0.13: 0.63; middle leg: 6.15: 4.50: 1.86: 0.27; hind leg: 6.15: 3.48: 0.27: 0.35. Fore femur slender, width 0.34, ratio length/width: 6.44. Abdominal venter length 1.23, length of tergum 7: 0.23, length of sternum 7: 0.63. Shape of sternum 7: see Diagnosis above. Connexival margin with long hairs.

Macropterous male: Head width 1.62, interocular width 0.63, eye size 0.77. Lengths of antennal segments 1–4: 2.97: 1.37: 0.99: 0.82. Pronotum: apex of pronotal lobe rounded, median length 2.91, humeral width 2.50. Fore wing length 5.5. Lengths of leg segments: fore leg: 2.72: 2.44: 0.17: 0.81; middle leg: 7.10: 5.56: 2.20: 0.34; hind leg: 6.90: 4.30: 0.33: 0.40. Fore femur slender, width 0.38, ratio length/width: 7.16. Abdomen length on ventral view: 1.14, pregenital length 0.50; sternum 7 slightly longer than sterna 5 and 6 combined, length 0.17. Other characteristics as in apterous males.

Macropterous female unknown.

Remarks. Metrocoris sicilis , new species, clearly belongs to the M. ciliatus group (sensu Chen & Nieser, 1993). It differs from other species in this group by the combination of following characteristics: dense hairs on antennal segments 1–3 of the male; both males and females with the fore femur sub-apically constricted, and its ventral surface with a sub-apical elevation; longer, sickle-shaped parameres; and the shape of sternum 7 of females. It is most similar to M. triangulatus due to triangular shape of body, but can be separated from the latter by the characteristics above.

To date, four species belonging to the M. ciliatus species group have been found in Vietnam: M. ciliatus , M. inthanon , M. triangulatus , and M. sicilis new species. Among these, two species, M. sicilis and M. triangulatus , are most closely related to each other, due to the triangular appearance of the body, the dorso-ventrally compressed body, the structure of the endosoma, and the general shape of sternum 7 in the female. Metrocoris sicilis can be easily separated from M. triangulatus by having the fore femur of both sexes with a sub-apical elevation on the ventral surface, antennal segments 1–3 of the male with dense and long hairs, the genitalia relatively larger, and the male paramere longer, with a broadly rounded apex. In M. triangulatus , the fore femur of both sexes is simple, without a sub-apical elevation on the ventral surface, the antenna of the male has only a dense pilosity of shorter hairs on segments 2 and 3, the genitalia are small, and the paramere is short, tapering towards a narrow apex.

Etymology. The word “ sicilis ” in Latin means sickle (see Brown, 1956). The species epithet refers to the sickle-shaped paramere, and is used as a noun in apposition.

Distribution. Vietnam: Hanoi (Ba Vi), Phu Tho (Xuan Son) ( Fig. 140 ).

Habitats. This new species was found on forest streams.

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. 94–99. Morphological features of Metrocoris sicilis, new species. 94: right antenna of male. 95: right fore leg of male. 96: left paramere. 97, 98: endosomal sclerites, lateral and dorsal views. 99: abdomen of female, ventral view (94, 95 same scale; 96–98 same scale).

Fig. 140. Distribution records in Vietnam of Metrocoris ciliatus, M. inthanon, Metrocoris sicilis, new species, and M. triangulatus.