Rhyacobates 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 : 67-70

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.10064079
persistent identifier	https://treatment.plazi.org/id/045E878D-FF9E-297E-38A2-FB7672FA0ADC
treatment provided by	Plazi
scientific name	Rhyacobates Esaki, 1923
status

Treatment

Revised key to species of Rhyacobates Esaki, 1923 View in CoL

Note: The males of Rhyacobates spp. do not exhibit many reliable characters for species identification. In most species, the shape of the proctiger, especially its lateral lobes, and the shape of the paramere, preferably to be used in combination, are the only characters for species identification. However, species identification of Rhyacobates are more reliable when associated female specimens are present in the samples.

1. Both sexes: both mesonotum and metanotum completely black, without median yellow marking ( Figs 3A–B View Fig , 4A–B View Fig ) ........................................................................................................................... 2

– Both sexes: mesonotum with median yellow marking ( Figs 3C–R View Fig , 4C–M, O View Fig ) ............................... 4

2. Female: body relatively robust, width 3.1–3.2, ratio of body width: length> 0.36; abdominal mediotergite I swollen, nearly as long as two posterior terga together ( Fig. 3I View Fig ); posterior margin of abdominal mediotergite VII without median process; posterior margin of abdominal segment VII dorsally without process, ventrally with a narrow median process ( Fig.5H View Fig ). Male: middle trochanter without spines; lateral lobes of proctiger distinctly angular ( Fig. 6H View Fig ); paramere strongly thickened at middle, with scattered short setae on distal part ....................... R. constrictus Tran & Nguyen, 2016 View in CoL

– Female: body relatively slender, width 2.3–3.0, ratio of body width: length <0.29; abdominal mediotergite I not swollen, nearly as long as mediotergite II; posterior margin of abdominal mediotergite VII with a median process; posterior margin of abdominal segment VII dorsally with a pair of processes, ventrally with a semicircular median process ( Figs 16E View Fig , 18E View Fig ). Male: middle trochanter with 3–5 spines ( Figs 16J View Fig , 17I View Fig ); lateral lobes of proctiger subtrapezoid or broadly rounded ( Fig. 6A–B View Fig ); paramere not thickened at middle, distal part without setae ( Fig. 8A–B View Fig ) .................. 3

3. Female: body length 8.8–9.3, connexival process of abdominal segment VII short, with relatively blunt apex ( Fig. 16D View Fig ). Male: body length 6.5–6.9; lateral lobes of proctiger subtrapezoid ( Fig. 6A View Fig ); apical part of paramere relatively slender, distinctly curved ( Figs 8A View Fig , 16L View Fig ) .............. R. bui sp. nov.

– Female: body length 11.2–11.9, connexival process of abdominal segment VII long, with pointed apex ( Fig. 18D View Fig ). Male: body length 7.7–8.0; lateral lobes of proctiger broadly rounded ( Fig. 6B View Fig ); apical part of paramere relatively stout, not distinctly curved ( Figs 8B View Fig , 18K View Fig ) .................................. ........................................................................................................................... R. elongatus sp. nov.

4. Female: metanotum completely black, without yellow markings ( Fig. 3F, K, M View Fig ). Male: length of middle tibia ca 1.8–2.1 times length of hind tibia ............................................................................ 5

– Female: metanotum with median yellow stripe. Male: length of middle tibia usually less than 1.8 times length of hind tibia (except in R. edentatus View in CoL : 1.9–2.0, and R. takahashii View in CoL : 1.5–1.8) ................. 7

5. Female: posterior margin of metanotum with a pointed median process ( Fig. 23C–D View Fig ); abdomen short, ventral length ca 0.2 times body length; posterior margin of abdominal segment VII with long connexival processes and laterally with a pair of pointed processes ( Fig. 23F, H View Fig ). Male: ventral length of abdomen ca 0.3 times body length; lateral lobes of proctiger rounded; paramere stout, with middle part thickened ( Figs 8E View Fig , 23M View Fig ) ............................................ R. anderseni Tran & Yang, 2006 View in CoL

– Female: posterior margin of metanotum without process; abdomen longer, ventral length ca 0.5 times body length; posterior margin of abdominal segment VII with long connexival processes and laterally with a pair of short angular processes or without distinct process ( Figs 5J, L View Fig , 30F–G View Fig ). Male: ventral length of abdomen ca 0.4–0.5 times body length; lateral lobes of proctiger angular; paramere slender ............................................................................................................................................... 6

6. Female: abdominal segment VII with connexiva reaching or overlapping each other on dorsum, thus covering most of mediotergites VII and VIII; posterior margin of segment VII with a pair of pointed lateral processes ( Figs 3M View Fig , 30G View Fig ). Male: metanotum chiefly black, without yellow markings; proctiger laterally with angular lobes produced into distinct process directed postero-ventrad ( Figs 7C View Fig , 30K View Fig ) ................................................................................................... R. malaisei Andersen & Chen, 1995 View in CoL

– Female: abdominal segment VII with connexiva not reaching each other on dorsum, thus mediotergites VII and VIII exposed; posterior margin of segment VII without distinct lateral processes ( Fig. 3K View Fig ). Male: metanotum with a very thin yellow median stripe; lateral lobes of proctiger angular but without distinct process ( Fig. 7A View Fig ) .................................................................... R. gongvo Tran & Yang, 2006 View in CoL

7. Female: abdominal segment VII without any posterior processes; connexiva of segments IV–VII meeting each other along midline of dorsum; posterior margin of sternum VII relatively obtuse, without distinct process ( Fig. 28D–E View Fig ). Male: length of middle tibia ca 1.9–2.0 times length of hind tibia .......................................................................................... R. edentatus Andersen &Chen, 1995 View in CoL

– Female: abdominal segment VII with posterior processes; connexiva converging and partly meeting each other at segment VII or not meeting each other; posterior margin of sternum VII ventrally with distinct process or presenting an arc shape ( R. angustus View in CoL ). Male: length of middle tibia ≤ 1.8 times length of hind tibia ............................................................................................................................ 8

8. Both sexes: pronotum chiefly yellowish, mesonotum with a broad yellowish median marking; metanotum with laterally expanded yellow marking ( Fig. 3R View Fig ). Female: abdominal segment VI with small but distinct connexival processes; segment VII also with a pair small connexival processes, ventral margin bilobate. Male: lateral lobes of proctiger subtrapezoidal ( Fig. 7H View Fig ) ........................... ........................................................................................................... R. zetteli Tran & Nguyen, 2016 View in CoL

– Both sexes: pronotum, mesonotum, metanotum chiefly black, with a narrower median marking. Female: abdominal segment VI without connexival processes; ventral margin of segment VII not bilobate. Male: lateral lobes of proctiger rounded or angular .......................................................... 9

9. Female: abdominal segment VII without connexival processes ( Figs 20E, G View Fig , 31E–F View Fig ); abdominal mediotergite I elongate, not shorter than two subsequent terga together. Male: body length 5.4–6.3 ......................................................................................................................................................... 10

– Female: abdominal segment VII with connexival processes; abdominal mediotergite I not elongate, nearly as long as mediotergite II. Male: body length 6.2–8.4 .........................................................11

10. Both sexes: abdominal mediotergite I swollen and large, nearly as long as three subsequent terga together ( Fig. 20A, H View Fig ). Female: abdominal mediotergite II medially hidden beneath mediotergite I except laterally; abdominal terga II–V extremely short; abdominal segment VII as in Fig. 20E–G View Fig . Male: body length 5.9–6.3 ................................................................................... R. turgidus sp. nov.

– Both sexes: abdominal mediotergite I shorter than two subsequent abdominal mediotergites together ( Fig. 31A, G View Fig ). Female: abdominal mediotergite II not covered by mediotergite I; terga II–V normal sized, not shortened ( Fig. 31A View Fig ); abdominal segment VII as in Fig. 31D–F View Fig . Male: body length 5.4– 5.9 ............................................................................................. R. recurvus Andersen & Chen, 1995 View in CoL

11. Female: posterior margin of abdominal sternum VII with an acute median process. Male: body length 6.2–7.4 ................................................................................................................................. 12

– Female: posterior margin of abdominal sternum VII with an obtuse median process or presenting an arc shape. Male: body length 7.5–8.4 ............................................................................................. 14

12. Female: posterior margin of abdominal mediotergite VII with a short median process ( Fig. 35E View Fig ); connexival processes of abdominal segment VII long and directed postero-ventrad ( Fig. 35E–G View Fig ). Male: lateral lobes of proctiger rounded ( Figs 7G View Fig , 35M View Fig ); paramere strongly curved at basal fourth as in Figs 8M View Fig , 35N View Fig , relatively straight on apical half .................................... R. takahashii Esaki, 1923 View in CoL

– Female: posterior margin of abdominal mediotergite VII without median process; connexival processes of abdominal segment VII short, angular, directing upwards ( Figs. 22E View Fig , 25G–I View Fig ). Male: lateral lobes of proctiger angular; paramere more curved on apical half ....................................... 13

13. Female: posterior margin of abdominal segment VII laterally with a pair of rounded process ( Fig. 22D–E View Fig ). Male: middle trochanter without spines; paramere strongly curved at basal third, as in Figs 8D View Fig , 22K View Fig ....................................................................... R. abdominalis Andersen & Chen, 1995 View in CoL

– Female: posterior margin of abdominal segment VII with laterally with a pair of long, pointed processes ( Fig. 25E–J View Fig ). Male: middle trochanter with 3–6 spines; paramere sinuate, as in Figs 8F View Fig , 25N View Fig ................................................................................. R. chinensis Hungerford & Matsuda, 1959 View in CoL

14. Female: connexival processes of abdominal segment VII distinctly bilobate; posterior margin of abdominal mediotergite VII with a short median process. Male: posterior lobes of proctiger angular ( Fig. 7B, F View Fig ) ..................................................................................................................................... 15

– Female: connexival processes of abdominal segment VII angular, not bilobate; posterior margin of abdominal mediotergite VII without median process. Male: posterior lobes of proctiger rounded ( Fig. 7E View Fig ) .......................................................................................................................................... 16

15. Female: subtriangular yellowish marking on metanotum wide, with larger apex angle; inner lobe of bilobate connexival processes of abdominal segment VII elongate ( Fig. 29D, F View Fig ). Male: paramere sinuate ( Figs 8H View Fig , 29L View Fig ) .................................................................... R. lundbladi ( Hungerford, 1957) View in CoL

– Female: subtriangular yellowish marking on metanotum relatively thin, with sharp apex angle; inner lobe of bilobate connexival processes of abdominal segment VII very short ( Fig. 34D–E View Fig ). Male: paramere strongly curved at basal third, with hook-shaped apex ( Figs 8L View Fig , 34L View Fig ) .............................. .......................................................................................................... R. svenhedini ( Lundblad, 1934) View in CoL

16. Female: posterior margin of mediotergite VII with a median process; abdominal sternum VII with broadly rounded posterior margin ( Fig. 3G View Fig ); mesosternum anteriorly blackish with subtriangular yellow marking on posterior part, not divided by a blackish line. Male: middle trochanter without spines; paramere strongly curved at basal third, with narrow apex .................................................... ...................................................................................................... R. angustus Tran & Nguyen, 2016 View in CoL

– Female: mediotergite VII without median process; posterior margin of sternum VII angularly produced in the middle ( Fig. 33D–G View Fig ); mesosternum chiefly blackish with two median yellowish spots, divided by a blackish line ( Fig. 33B View Fig ). Male: middle trochanter with 3–5 spines; paramere strongly curved at basal fourth, with hook-shaped apex ( Figs 8K View Fig , 33L View Fig ) ........................................... ..................................................................................................... R. scorpio Andersen & Chen, 1995 View in CoL