Rhyacobates turgidus, Leng & Tran, 2023

Leng, Zhaoqi & Tran, Anh Duc, 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 : 26-30

Rhyacobates turgidus sp. nov.

urn:lsid:zoobank.org:act:A61745D8-0A50-4E9C-89CA-B557C637ED2E

Figs 3C–D, 4C, 5C, 6C, 8C, 19–20

Diagnosis

Body length of apterous females 7.82–8.50, of apterous males 5.90–6.31. In both sexes, abdominal mediotergite I distinctly swollen and large, about as long as the three subsequent abdominal terga together ( Figs 3C–D, 4C, 20A–B, H). Female: pronotum mainly black with a median brownish-yellow spot; mesonotum and metanotum mainly black with a median brownish-yellow stripe ( Figs 3C, 19A, 20A); abdominal mediotergite I with a median brownish-yellow stripe; abdominal terga II–VI distinctly short ( Figs 3C–D, 20A–B); abdominal mediotergite II medially hidden beneath the abdominal mediotergite I but not laterally ( Figs 3C, 20A); laterosternites of connexivum VII expanded dorsad, folded mesad, but not meeting in middle of abdominal dorsum; posterior margin of sternum VII with a short and pointed median process ( Fig. 20E–G). Male: middle trochanter with one spine; middle femur with scattered small spines, not arranged in distinct row ( Fig. 20J); length of middle tibia ca 1.4 times length of hind tibia; proctiger with angular lobes laterally ( Figs 6C, 20K); paramere relatively slender, strongly curved at basal third, distal part tapering towards hook-shaped apex ( Figs 8C, 20L).

Etymology

The species epithet is derived from the Latin adjective ʻturgidusʼ, meaning ʻswollenʼ and refers to the extremely large abdominal mediotergite I.

Material examined

Holotype ( Fig. 19A)

CHINA • ♀ (apterous); Sichuan Province, Lu-zhou City , He-jiang County, Tian-tang-ba; 106°15′09.5″ N, 28°35′3.6″ E; 741 m a.s.l.; 9 Aug. 2016; Chen-guang Zheng leg.; NKUM.

Paratypes ( Fig. 19B)

CHINA • 3 ♁♁, 3 ♀♀ (apterous), 1 ♀ (dealated macropterous); same collection data as for holotype; NKUM • 3 ♀♀ (apterous); Chongqing City, Si-mian Mountain ; 28°36′30.4″ N, 106°22′19.2″ E; 895 m a.s.l.; 10 Aug. 2016; Yan-fei Li leg.; NKUM • 1 ♁, 4 ♀♀ (apterous); Sichuan Province, Lu-zhou City, Xu-yong County, Hua-gao-xi National Nature Reserve ; 28°16′19.4″ N, 105°32′27.6″ E; 741 m a.s.l.; 15 Aug. 2013; Yang Liu and Zhen Ye leg.; NKUM .

Description

Apterous female

MEASUREMENTS. Body length 7.82–8.50 (holotype 8.20), width 3.01–3.60 (holotype 3.48), head width 1.48, interocular width 0.71, eye length (dorsal view) 0.43; relative lengths of antennal segments I– IV: 3.89:1.02: 1.18: 0.92; pronotum: length 0.81, width 1.65; mesonotum: length 3.78, width 3.25; metanotum: length 0.84, width 2.84; abdomen length (ventral view) 2.94; abdominal sternum VII: length 1.56, width 1.05; abdominal mediotergite I: length 0.86, width 1.71; relative lengths of leg segments (femur: tibia: tarsal segment I:tarsal segment II): fore leg: 3.94:3.38: 1.93: 0.88, middle leg: 11.12: 6.88: 4.25:0.45, hind leg: 11.35: 5.41:0.16: 0.24.

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 ( Figs 3C, 19A, 20A). Connexivum dorsally brownish-yellow. Abdominal mediotergite I with a median yellow stripe. Mesosternum chiefly blackish with a median subtriangular yellowish spot ( Fig. 20C). Abdominal venter light yellow.

ABDOMEN. Abdomen relatively short, almost straight ( Fig. 5C, 20D). Connexiva erect on abdominal segments I–VI, parallel to each other above mediotergites, reflexed over terminal mediotergites ( Fig. 20A–B).Abdominal mediotergite I distinctly swollen, nearly as long as three subsequent abdominal terga together, sparsely covered with silvery pubescence on each side; abdominal terga II–VI distinctly short in length ( Figs 3C–D, 20A–B). Abdominal mediotergite II medially hidden beneath abdominal mediotergite I, but laterally exposed ( Figs 3C–D, 20A). Abdominal segment VII elongate, nearly as long as two preceding abdominal segments together, length of ventral margin distinctly longer than that of dorsal margin in lateral view ( Figs 5C, 20D); laterosternites of connexivum VII expanded dorsad, folded mesad, not meeting in middle of abdominal dorsum ( Fig. 20E). Abdominal sternum VII tapering caudad, posterior margin with a short and pointed median process ( Fig. 20E–F).

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 ( Figs 3D, 20B).

MEASUREMENTS. Body length 7.81, width 2.90, head width 1.45, interocular width 0.66, eye length (dorsal view) 0.53; pronotum: length 2.97, width 2.41; mesonotum width 2.90; metanotum: length 0.67, width 2.51; abdominal sternum VII: length 1.05, width 1.49; abdominal mediotergite I: length 0.67, width 1.19.

Apterous male

MEASUREMENTS. Body length 5.90–6.31, width 2.14–2.20, head width 1.32, interocular width 0.60, eye length (dorsal view) 0.42; relative lengths of antennal segments I–IV: 3.28: 0.92: 1.03: 0.87; pronotum: length 0.71, width 1.41; mesonotum: length 1.30, width 2.14; metanotum: length 0.71, width 1.82; abdomen length (ventral view) 1.98; abdominal sternum VII: length 0.46, width 0.83; abdominal mediotergite I: length 0.46, width 0.85; relative lengths of leg segments (femur: tibia: tarsal segment I: tarsal segment II): fore leg: 3.33: 2.88: 1.02: 0.63, middle leg: 8.72: 5.41: 2.66: 0.43, hind leg: 8.95:3.78: 0.16: 0.23.

COLORATION. 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 black, without yellow markings ( Figs 4C, 19B, 20H). Connexivum dorsally blackish ( Figs 4C,

19B). Mesosternum chiefly blackish with a median subtriangular yellowish spot ( Fig. 20I). Abdominal venter dark-yellow.

ABDOMEN. Abdomen relatively short. Abdominal mediotergite I extremely swollen ( Figs 4C, 20H), nearly as long as three subsequent abdominal terga together.

LEG. Middle trochanter with one spine; middle femur with scattered small spines, not arranged in distinct row ( Fig. 20J).

GENITALIA. Abdominal segment VIII ventro-laterally impressed. Pygophore large, ovate. Proctiger with angular lobes laterally ( Figs 6C, 20K). Paramere relatively slender, strongly curved at basal third, distal part tapering towards hook-shaped apex ( Figs 8C, 20L).

Distribution

China: Chongqing, Sichuan.

Comparative notes

Rhyacobates turgidus sp. nov. is closely related to R. recurvus and R. constrictus . These three species possess a robust body and similar outline of abdominal segment VII ( Fig. 3C, I, N). Rhyacobates turgidus can be distinguished from R. constrictus by median yellowish stripes on the mesonotum, metanotum and abdominal mediotergite I ( Figs 3C, 20A), which are absent in R. constrictus . Rhyacobates turgidus can be distinguished from R. recurvus by the following characteristics: (1) in lateral view, R. turgidus has a nearly straight abdomen ( Fig. 5C, 20D), whereas R. recurvus has its abdomen curved dorsad ( Figs 5M, 31C); (2) R. turgidus has an extremely swollen abdominal mediotergite I, which is nearly as long as the three subsequent abdominal tergites, and distinctly short abdominal terga II–VI ( Figs 3C–D, 20A–B), whereas abdominal terga I–VI of R. recurvus are relatively normal-sized ( Figs 3N, 31A).