Rhyacobates bui Leng & Tran 2023, sp. nov.
Creators: name: Leng, Zhaoqi
name: Tran, Anh Duc
name: Ye, Zhen
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hemiptera
Gerridae
Rhyacobates
Rhyacobates bui

description: Rhyacobates bui sp. nov.
urn:lsid:zoobank.org:act: 8A1A2DC9-C314-4458-AF0C-752FEECA39C7
Figs 3A, 4A, 5A, 6A, 8A, 15–16
Diagnosis
Body length of apterous females 8.81–9.30, of apterous males 6.50–6.91. In both sexes, mesonotum and metanotum completely black, without median yellow stripe (Figs 3A, 4A). Female: posterior margin of mediotergite VII with a distinctly long, slender median process (Fig. 16A, D); posterior margin of abdominal segment VII with five processes, including a blunt process terminating each connexivum, a pair of blunt processes laterally, and a semicircular median process ventrally (Fig. 16D–G). Male: middle trochanter with 3–4 small spines; middle femur with scattered small spines arranged in a row, but with irregular distance between spines (Fig. 16J); length of middle tibia ca 1.6 times length of hind tibia; proctiger laterally with subtrapezoid lobes, dorsally with brownish setae (Figs 6A, 16K); paramere relatively slender, strongly curved at basal third, distal part tapering towards distinctly curved and narrow apex (Figs 8A, 16L).
Etymology
This species dedicated to Prof. Wenjun Bu (Institute of Entomology, Nankai University, China), in recognition of his contributions to the study ofthe taxonomy, phylogeny and biogeography of Heteroptera.
Material examined
Holotype (Fig. 15A)
CHINA • ♀ (apterous); Guangxi Province, Fang-cheng-gang City, Shang-si County, Shi-wan-da-shan; 21°54′4.1″ N, 107°54′22.1″ E; 300–400 m a.s.l.; 13 Aug. 2019; Zhen Ye and Si-qi Wang leg.; NKUM.
Paratypes (Fig. 15B)
CHINA • 3 ♁♁ (apterous); same collection data as for holotype; NKUM.
VIETNAM • 10 ♁♁, 3 ♀♀ (apterous); L ạng SƠn Province, L ộc Bình, M ẫu SƠn, upstream of Long Đǻu stream; 21°48′59.3″ N, 106°59′56.3″ E; 7 Nov. 2020; A.D. Tran et al. leg.; TAD20-37; ZVNU • 1 ♁, 1 ♀ (apterous); same collection data as for preceding; NHMW • 1 ♁, 1 ♀ (apterous); same collection data as for preceding; NKUM • 2 ♁♁, 2 ♀♀ (apterous); same collection data as for preceding; ZRC.
Description
Apterous female
MEASUREMENTS. Body length 8.81–9.30 (holotype 8.81), width 2.34–2.52 (holotype 2.52), head width 1.41, interocular width 0.75, eye length (dorsal view) 0.62; relative lengths of antennal segments I–IV: 3.34: 1.02: 1.12:0.71; pronotum: length 0.72, width 1.51; mesonotum: length 2.34, width 2.52 (holotype 2.52); metanotum: length 0.84, width 2.21; abdomen length (ventral view) 4.16; abdominal sternum VII: length 1.16, width 1.15; abdominal mediotergite I: length 0.35, width 0.92; relative lengths of leg segments (femur:tibia: tarsal segment I: tarsal segment II): fore leg: 3.56: 2.84:1.46:0.78, middle leg: 10.01:5.94:2.63:0.44, hind leg: 10.16: 3.88: 0.11:0.17.
COLORATION. Median black spot of head reduced, indistinctly bifid or dissolved into smaller spots posteriorly (Fig. 3A). Pronotum mainly black with a median brownish-yellow spot. Mesonotum and metanotum completely black, without yellow markings (Figs 3A, 16A). Connexivum dorsally blackish. Venter of female mainly light yellow, except mesosternum and mesopleuron black laterally (Fig. 16B). Abdominal venter light yellow.
ABDOMEN. Abdomen relatively long, nearly straight, gradually tapering towards apex (Figs 5A, 16C). Connexiva erect on abdominal segments I–VI, parallel to each other above mediotergites, reflexed over terminal mediotergites (Fig. 16A, D). Abdominal mediotergite I not swollen, fully covered with silvery pubescence (Fig. 3A). Posterior margin of mediotergite VII with a distinctly long median process (Fig. 16A, D), about half the length of mediotergite VII (excluding the process). Abdominal segment VII elongate, nearly as long as three preceding abdominal segments, completely enclosing genital segments. Abdominal dorsal margin not curved in lateral view (Figs 5A, 16C). Posterior margin of abdominal segment VII with five processes, including a blunt process terminating each connexivum, a pair of blunt processes laterally, and a semicircular median process ventrally (Fig. 16D–G).
Apterous male
MEASUREMENTS. Body length 6.50–6.91, width 1.62–1.97. head width 1.21, interocular width 0.52, eye length (dorsal view) 0.54; relative lengths of antennal segments I–IV: 3.11: 0.88: 0.98: 1.08; pronotum: length 0.70, width 1.35; mesonotum: length 1.87, width 1.62; metanotum: length 0.65, width 1.60; abdomen length (ventral view) 2.72; abdominal sternum VII: length 0.38, width 0.52; abdominal mediotergite I: length 0.22, width 0.57; relative lengths of leg segments (femur: tibia: tarsal segment I: tarsal segment II): fore leg: 3.01: 2.34: 0.78: 0.52, middle leg: 8.88: 4.65: 2.10: 0.38, hind leg: 8.56:2.97: 0.11: 0.15.
COLORATION. Median black spot of head reduced, indistinctly bifid or dissolved in smaller spots posteriorly (Figs 4A, 16H). Pronotum and mesonotum mainly black with a median brownish-yellow spot. Mesonotum and metanotum completely black, without yellow markings (Figs 4A, 16H). Connexivum dorsally blackish. Mesosternum chiefly blackish with a median subtriangular yellowish spot (Fig. 16I). Abdominal venter light yellow.
ABDOMEN. Abdominal mediotergite I not swollen, nearly completely covered by silvery pubescence (Fig. 4A).
LEG. Middle trochanter with 3–4 small spines; middle femur with a row of irregularly-spaced small spines (Fig. 16J).
GENITALIA. Abdominal segment VIII ventro-laterally depressed. Pygophore large, ovate. Proctiger laterally with subtrapezoid lobes, dorsally with brownish setae (Figs 6A, 16K). Paramere relatively slender, strongly curved basal third, distal part tapering towards distinctly curved and narrowed apex (Figs 8A, 16L).
Distribution
China: Guangxi. Vietnam: Lạng SƠn.
Comparative notes
This new species is closely related to R. elongatus sp. nov. in having an elongate medial process on the posterior margin of mediotergite VII and five processes on abdominal segment VII of the female, including two connexival processes, two lateral blunt processes and a semicircular median process on the ventral side (Figs 16D–F, 18D–F). However, the abdominal mediotergite I of R. bui sp. nov. is fully covered with silvery pubescence, which is much denser than in R. elongatus (Fig. 3A–B). The connexival processes of abdominal segment VII of R. bui are much shorter and blunter (Fig. 16D) than those of R. elongatus (Fig. 18D). The abdomen of the female of R. bui is almost straight (Fig. 16C), whereas that of R. elongatus is curved dorsad in the caudal part (Fig. 18C). These two species are also related to five species (i.e., R. angustus, R. lundbladi, R. svenhedini, R. takahashii, and R. zetteli) in having the median process on the posterior margin of mediotergite VII in the female, but this structure in R. bui and R. elongatus is much longer than that of the five latter species. Furthermore, both R. bui and R. elongatus have entirely black mesonota and metanota (Figs 3A–B, 4A–B), without yellow stripes (in both sexes), which is a character state shared with R. constrictus. Females of R. bui and R. elongatus can be easily separated from R. constrictus by the following characteristics: (1) R. bui and R. elongatus have slender bodies (Fig. 3A–B), whereas R. constrictus has a wider, stouter body (Fig. 3I); (2) the posterior margin of mediotergite VII of R. bui and R. elongatus has a median process (Figs 16A, D, 18A, D), whereas that of R. constrictus lacks a median process (Figs 3I, 26B); (3) the posterior margin of abdominal segment VII of R. bui and R. elongatus has five processes (Figs 16D–F, 18D–F), whereas that of R. constrictus has only one median process ventrally (Fig. 26A–B; also see Tran & Nguyen 2016: figs 36–39).
description: Published as part of Leng, Zhaoqi, Tran, Anh Duc & Ye, Zhen, 2023, Taxonomic review of Rhyacobates Esaki, 1923, with descriptions of three new species (Hemiptera: Heteroptera: Gerridae), pp. 1-73 in European Journal of Taxonomy 893 (1) on pages 18-19, DOI: 10.5852/ejt.2023.893.2285, http://zenodo.org/record/8385630