Rhyacobates takahashii Esaki, 1923

Leng, Zhaoqi, Tran, Anh Duc & Ye, Zhen, 2023, Taxonomic review of Rhyacobates Esaki, 1923, with descriptions of three new species (Hemiptera: Heteroptera: Gerridae), European Journal of Taxonomy 893 (1), pp. 1-73 : 63-66

publication ID	https://doi.org/ 10.5852/ejt.2023.893.2285
publication LSID	lsid:zoobank.org:pub:D9DA4879-BC1D-4947-96E8-7D574DE334BA
DOI	https://doi.org/10.5281/zenodo.10064073
persistent identifier	https://treatment.plazi.org/id/045E878D-FFE2-297A-3A5E-FA33742E0934
treatment provided by	Plazi
scientific name	Rhyacobates takahashii Esaki, 1923
status

Treatment

Rhyacobates takahashii Esaki, 1923 View in CoL

Figs 2F View Fig , 3Q View Fig , 4O View Fig , 5P View Fig , 7G View Fig , 8M View Fig , 35 View Fig

Rhyacobates takahashii Esaki, 1923: 388 View in CoL , pl. 1 (original description).

Rhyacobates takahashii View in CoL – Esaki 1925: 60. — Matsuda 1960: 273–276, figs 656–658, 660, 663, 674–676, 678. — Andersen & Chen 1995: 55, figs 2–5 (with remarks).

Diagnosis

Body length of apterous females 8.60–10.88, of apterous males 6.20–7.32. Female: pronotum mainly black with a median brownish-yellow spot; mesonotum and metanotum mainly black with a median brownish-yellow stripe ( Fig. 35A View Fig ); posterior margin of abdominal mediotergite VII with a short median process ( Fig. 35E View Fig ); posterior margin of abdominal segment VII with three processes, including a relatively slender, angular process terminating each connexivum, and a pointed median process ventrally ( Fig. 35F–G View Fig ). Male: middle trochanter with one spine; middle femur with scattered small spines, not arranged in distinct row ( Fig. 35L View Fig ); length of middle tibia ca 1.5–1.8 times length of hind tibia; proctiger with angular lobes laterally ( Figs 7G View Fig , 35M View Fig ); paramere relatively slender, strongly curved at basal fourth, distal part tapering towards hook-shaped apex ( Figs 8M View Fig , 35N View Fig ).

Material examined

Non-type specimens

CHINA – Guangxi Province • 5 ♁♁, 2 ♀♀ (apterous); Lai-bin City, Jin-xiu County; 23°55′51.6″ N, 110°10′46.6″ E; 524 m a.s.l.; 26 Jul. 2019; Ze-zhong Jin leg.; NKUM. – Taiwan Island GoogleMaps • 1 ♁ (apterous); Taitung, Xinwulixi, Xinwuli bridge; 2 Dec. 2001; H.H. Tan, K. Lim and Y.M. Ju leg.; THH0199; ZRC • 1 ♀ (apterous); Taipei County, Wulai, Fusan ; 24°46.973′ N, 121°30.106′ E; 336 m a.s.l.; 6 Apr. 2004; A.D. Tran leg.; TAD0402; ZRC GoogleMaps • 3 ♁♁, 7 ♀♀ (apterous); Pingtung County, Henchun, Wangsha stream; 22°02.351′ N, 120°45.852′ E; 39 m a.s.l.; 8 Apr. 2004; A.D. Tran leg.; TAD0406; ZRC GoogleMaps • 4 ♁♁, 2 ♀♀ (apterous), 2 ♁♁, 1 ♀ (macropterous); Yilan County, Yuanshan, Dahu stream; 24°45.218′ N, 121°39.777′ E; 147 m a.s.l.; 12 Apr. 2004; A.D. Tran leg.; TAD0412; ZRC GoogleMaps • 7 ♁♁, 9 ♀♀ (dealated macropterous); Taizhong City, Ba-xian Mountain ; 24°17′55.1″ N, 120°45′41.5″ E; 5 Jun. 2011; Qiang Xie leg.; NKUM GoogleMaps .

Supplemental description

Apterous female

MEASUREMENTS. Body length 8.60–10.88, width 2.59–2.90, head width 1.84, interocular width 0.85, eye length (dorsal view) 0.68; relative lengths of antennal segments I–IV: 4.10: 1.05:1.22:0.81; pronotum: length 0.90, width 1.84;mesonotum: length3.05,width 2.94; metanotum:length 0.92, width 2.65;abdomen length (ventral view) 4.66; abdominal sternum VII: length 1.87, width 1.29; abdominal mediotergite I: length 0.35, width 1.11; relative lengths of leg segments (femur:tibia:tarsal segment I:tarsal segment II): fore leg: 4.46: 3.62: 2.01:0.90, middle leg: 12.40:6.86: 2.98: 0.38, hind leg: 12.73: 4.57:0.11:0.14.

C OLORATION. Median black spot of head posteriorly bifurcate. Pronotum mainly black with a median brownish-yellow spot. Mesonotum and metanotum mainly black with a median brownish-yellow stripe ( Fig. 35A View Fig ). Abdominal tergum I with a median yellow marking. Connexivum dorsally brownish-yellow. Mesosternum chiefly blackish with a median subtriangular yellowish spot ( Fig. 35B View Fig ). Abdominal venter light yellow.

ABDOMEN. Abdomen relatively short, curved dorsad towards end ( Fig. 35D View Fig ) or nearly straight. Connexiva erect on abdominal segments I–II, converging along dorsal midline of IV–VI segments, meeting erectly above terminal mediotergites ( Fig. 35A View Fig ). Abdominal segment VII elongate, nearly as long as three preceding abdominal segments together ( Figs 5P View Fig , 35D View Fig ). Posterior margin of abdominal mediotergite VII with a short median process ( Fig. 35E View Fig ). Posterior margin of abdominal segment VII with three processes, dorsally above terminating each connexivum with a relatively slender process directing ventrad, ventrally with a pointed median process ( Fig. 35E–G View Fig ).

Dealated macropterous female

Similar to apterous female in general structure and coloration with following exceptions: thorax with a pronotal lobe, anterior part with a subrhombic yellow marking, posterior part elongate, covering most of mesonotum; posterior margin broadly rounded and brownish ( Fig. 3Q View Fig ).

MEASUREMENTS. Body length 10.01, width 2.86, head width 1.51, interocular width 0.60, eye length (dorsal view) 0.58; relative lengths of antennal segments I–IV: 3.98: 1.08:1.22:0.98; pronotum: length 3.12, width 2.41; mesonotum width 2.86; metanotum: length 0.73, width 2.62; abdomen length (ventral view) 4.80; abdominal sternum VII: length 1.46, width 1.79; abdominal mediotergite I: length 0.39, width 1.15; relative lengths of leg segments (femur:tibia: tarsal segment I:tarsal segment II): fore leg: 4.68:3.85:1.91: 0.97, middle leg: 12.47: 6.77: 3.32:0.33, hind leg: 13.31:5.13: 0.17: 0.23.

Apterous male

MEASUREMENTS. Body length 6.20–7.32, width 1.80–2.09, head width 1.43, interocular width 0.59, eye length (dorsal view) 0.60; relative lengths of antennal segments I–IV: 3.58: 1.04:1.07:0.84; pronotum: length0.76, width 1.55; mesonotum:length 2.16, width 2.09;metanotum:length0.69, width 1.88; abdomen length (ventral view) 2.69; abdominal sternum VII: length 0.53, width 1.22; abdominal mediotergite I: length 0.34, width 0.70; relative lengths of leg segments (femur:tibia: tarsal segment I:tarsal segment II): fore leg: 3.49: 2.91:1.06:0.62, middle leg: 10.02: 5.11: 2.17: 0.35, hind leg: 10.04: 2.79:0.11:0.13.

C OLORATION. Median black spot of head posteriorly bifurcate. Pronotum mainly black with a median brownish-yellow spot. Mesonotum mainly black with a median brownish-yellow stripe. Metanotum chiefly blackish, without yellow markings ( Fig. 35I View Fig ). Connexivum dorsally blackish. Mesosternum chiefly blackish with a median subtriangular yellowish spot, narrower than that of female ( Fig. 35K View Fig ). Abdominal venter light yellow.

LEG. Middle trochanter with one spine; middle femur with scattered small spines, not arranged in distinct row ( Fig. 35L View Fig ).

GENITALIA. Abdominal segment VIII ventro-laterally impressed. Pygophore large, ovate. Proctiger with rounded lobes laterally ( Figs 7G View Fig , 35I View Fig ). Paramere relatively slender, strongly curved at basal fourth, distal part tapering towards hook-shaped apex ( Figs 8M View Fig , 35J View Fig ).

Dealated macropterous male

MEASUREMENTS. Body length 6.39, width 1.85, head width 1.22, interocular width 0.47, eye length (dorsal view) 0.49; relative lengths of antennal segments I–IV: 3.24:0.93: 0.90: 0.79; pronotum: length 2.40, width 1.81; mesonotum width 1.85; metanotum: length 0.49, width 1.68; abdomen length (ventral view) 2.29; abdominal sternum VII: length 0.53, width 0.97; abdominal mediotergite I: length 0.25, width 0.69; relative lengths of leg segments (femur:tibia: tarsal segment I:tarsal segment II): fore leg: 3.66:3.11:1.34: 0.60, middle leg: 10.48: 5.32:2.26:0.33, hind leg: 11.02: 3.56: 0.13: 0.18.

Distribution

China: Guangxi (first record); Taiwan ( Andersen & Chen 1995).

Comparative notes

The female of R. takahashii can be distinguished from all other species of Rhyacobates by the combination of following characters: in the females, the posterior margin of abdominal segment VII has three processes, including an erect, elongate and angular process terminating each connexivum, which is directed ventrad, and a pointed, slender median process ventrally ( Fig. 35F–G View Fig ).