Rhyacobates elongatus, Leng & Tran, 2023

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 : 22-26

Rhyacobates elongatus sp. nov.

urn:lsid:zoobank.org:act:34F2BA54-0EE7-4FF0-BE46-11B774AB7BE9

Figs 3B , 4B , 5B , 6B , 8B , 17–18

Diagnosis

Body length of apterous females 11.25–11.88, of apterous males 7.70–8.00. In both sexes, mesonotum and metanotum completely black, without median yellow stripe ( Figs 3B , 4B ). Female: posterior margin of mediotergite VII with a distinctly long median process ( Fig. 18A, D ); posterior margin of abdominal segment VII with five processes, including an elongate, tapering process terminating each connexivum, a pair of blunt processes laterally, and a semicircular median process ventrally ( Fig. 18D–F ). Male: middle trochanter with 4–5 small spines on distal part; middle femur with small spines along its length, with irregular distances between spines ( Fig. 18I ); length of middle tibia ca 1.4 times length of hind tibia; proctiger laterally with broadly rounded lobes ( Figs 6B , 18J ); paramere relatively stout, curved at basal fourth, distal part tapering towards slightly curved and rounded apex ( Figs 8B , 18K ).

Etymology

The name elongatus refers to the pair of elongate connexival processes of sternum VII and also to the elongate medial process on posterior margin of mediotergite VII of the female ( Figs 2B , 18A, D–F ).

Material examined

Holotype ( Fig. 17A–B )

VIETNAM • ♀ (apterous); Hà Tĩnh Province, Vũ Quang National Park, Khe Nam Châm stream, site #2, downstream; 18°17′20.7″ N, 105°21′38.5″ E; 21 Apr. 2022; A.D. Tran et al. leg.; TAD2209; ZVNU .

Paratypes ( Fig. 17C )

VIETNAM • 4 ♁♁, 6 ♀♀ (apterous), 7 ♁♁, 1 ♀ (macropterous); same collection data as for holotype; ZVNU • 1 ♁, 1 ♀ (apterous); same collection data as for holotype; NKUM • 2 ♁♁, 2 ♀♀ (apterous), 1 ♁ (macropterous); same collection data as for holotype; ZRC • 4 ♁♁, 1 ♀ (apterous); Hà Tĩnh Province, Vũ Quang National Park, Khe Nam Châm stream, site #1, upstream; 18°17′31.5″ N, 105°21′18.7″ E; 21 Apr. 2022; A.D. Tran et al. leg.; TAD2208; ZVNU • 1 ♁, 1 ♀ (apterous); same collection data as for preceding; NHMW .

Description

Apterous female

MEASUREMENTS. Body length 11.25–11.88 (holotype 11.38), width 2.67–2.97 (holotype 2.43), head width 1.46, interocular width 0.62, eye length (dorsal view) 0.68; relative lengths of antennal segments I–IV: 4.20: 1.17:1.26: 0.92; pronotum: length 0.82, width 1.57; mesonotum: length 2.72, width 2.43; metanotum: length 0.92, width 2.55; abdomen length (ventral view) 4.95; abdominal sternum VII: length 1.58, width 1.26; abdominal mediotergite I: length 0.36, width 1.12; relative lengths of leg segments (femur: tibia: tarsal segment I:tarsal segment II): fore leg: 4.40:3.60: 2.15: 0.90, middle leg: 11.88: 6.40: 3.28:0.41, hind leg: 11.88: 4.75:0.12: 0.17.

C OLORATION. Median black spot of head posteriorly bifurcate. Pronotum mainly black with a median brownish-yellow spot. Mesonotum and metanotum completely black, without yellow markings ( Figs 3B , 18A ). Connexivum dorsally blackish. Venter of female mainly light yellow, except mesosternum and mesopleuron black antero-laterally ( Fig. 18B ). Metasternum and abdominal venter light yellow.

ABDOMEN. Abdomen relatively long, caudal part moderately curved dorsad ( Figs 5B , 18C ). Connexiva erect on abdominal segments I–VI, parallel to each other above mediotergites, reflexed over terminal terga ( Figs 5B , 17A , 18C ). Abdominal mediotergite I not swollen, with sparse silvery pubescence laterally ( Fig. 3B ). Abdominal segment VII elongate, in lateral view nearly as long as three preceding abdominal segments, completely enclosing genital segments; ventral length of sternum VII nearly as long as two preceding sterna. Abdominal connexiva convergent towards abdominal apex ( Figs 17B , 18A, D ). Posterior margin of abdominal segment VII with five processes, including an elongate, tapering process terminating each connexivum, a pair of blunt processes laterally, and a semicircular median process ventrally ( Fig. 18D–F ).

Macropterous female

Similar to apterous female in general structure and coloration with following exceptions: pronotal lobe covering most of mesonotum; posterior margin of pronotal lobe broadly rounded and slightly lighter colored (dark-yellowish).

MEASUREMENTS. Body length 10.81, width 2.53, head width 1.44, interocular width 0.59, eye length (dorsal view) 0.65; relative lengths of antennal segments I–IV: 4.10: 1.08: 1.19:0.94; pronotum: length 3.23, width 2.38; mesonotum width 2.53; metanotum: length 0.67, width 2.59; length of fore wing: 7.65; abdomen length (ventral view) 4.70; abdominal sternum VII: length 1.50, width 1.17; abdominal mediotergite I: length 0.35, width 1.08; relative lengths of leg segments (femur: tibia: tarsal segment I: tarsal segment II): fore leg: 4.20: 3.40: 2.03: 0.90, middle leg: 11.88: 6.19: 3.20: 0.44, hind leg: 11.88: 4.95: 0.14: 0.21.

Apterous male

MEASUREMENTS. Body length 7.70–8.00, width 2.08–2.22, head width 1.33, interocular width 0.54, eye length (dorsal view) 0.59; relative lengths of antennal segments I–IV: 3.78: 1.10: 1.26: 0.92; pronotum: length 0.72, width 1.35; mesonotum: length 2.25, width 1.94; metanotum: length 0.73, width 1.98; abdomen length (ventral view) 3.30; abdominal sternum VII: length 0.36, width 1.12; abdominal mediotergite I: length 0.25, width 0.72; relative lengths of leg segments (femur: tibia: tarsal segment I: tarsal segment II): fore leg: 4.13: 3.15: 1.26: 0.72, middle leg: 11.38: 5.56: 2.75: 0.41, hind leg: 11.44: 3.93: 0.13: 0.16.

C OLORATION. Median black spot of head posteriorly bifurcate. Pronotum and mesonotum mainly black with a median brownish-yellow spot. Mesonotum and metanotum completely black, without yellow markings ( Figs 4B , 17C , 18G ). Connexivum dorsally blackish. Mesosternum blackish with thin yellow median stripe on anterior two-thirds and light yellow posterior third ( Fig. 18H ). Metasternum and abdominal venter light yellow.

LEG. Middle trochanter with 4–5 small spines on distal part; middle femur with small spines scattered along its length, not forming a distinct row ( Fig. 18I ).

GENITALIA. Abdominal segment VIII slightly dorso-ventrally depressed. Genitalia slightly directed ventrad. Pygophore elongate, apical end subovate. Proctiger laterally with broadly rounded lobes ( Figs 6B , 18J ). Paramere relatively stout, curved at basal fourth, distal part tapering towards the slightly curved and rounded apex ( Figs 8B , 18K ).

Macropterous male

Similar to apterous male in general structure; pronotal lobe similar to that of macropterous female.

MEASUREMENTS. Body length 8.90–9.35 (including wings), width 2.20–2.34, head width 1.32, interocular width 0.52, eye length(dorsal view) 0.63; relative lengths of antennal segments I–IV:3.80: 1.07: 1.24: 0.92; pronotum: length 2.91, width 2.08; mesonotum width 2.13; metanotum: length 0.61, width 2.01; length of fore wing: 6.40; abdomen length (ventral view) 3.20; abdominal sternum VII: length 0.50, width 1.12; abdominal mediotergite I: length 0.29, width 0.67; relative lengths of leg segments (femur:tibia: tarsal segment I: tarsal segment II): fore leg: 4.00: 3.06:1.19:0.68, middle leg: 11.00:5.50: 2.78: 0.41, hind leg: 10.94:3.83: 0.11: 0.15.

Distribution

Vietnam: Hà Tĩnh.

Comparative notes

Rhyacobates elongatus sp. nov. is probably a sister species of R. bui sp. nov.; see comparative notes under R. bui .

Figures

Fig. 3. Photographs of bodies of Rhyacobates spp. in dorsal view (females), apterous form if not stated otherwise.A. R. bui sp. nov. B. R. elongatus sp. nov. C. R. turgidus sp. nov., apterous form.D. R. turgidus sp. nov., dealated macropterous form.E. R. abdominalis Andersen & Chen, 1995. F. R. anderseni Tran & Yang, 2006. G. R. angustus Tran & Nguyen, 2016, holotype (ZVNU). H. R. chinensis Hungerford & Matsuda, 1959. I. R. constrictus Tran & Nguyen, 2016. J. R. edentatus Andersen & Chen, 1995. K. R. gongvo Tran & Yang, 2006. L. R. lundbladi (Hungerford, 1957). M. R. malaisei Andersen & Chen, 1995. N. R. recurvus Andersen & Chen, 1995. O. R. scorpio Andersen & Chen, 1995. P. R. svenhedini (Lundblad, 1934). Q. R. takahashii Esaki, 1923, dealated macropterous form. R. R. zetteli Tran & Nguyen, 2016. Scale bar = 3 mm.

Fig. 4. Photographs of bodies of Rhyacobates spp. in dorsal view (males), apterous form if not stated otherwise.A. R. bui sp. nov.B. R. elongatus sp. nov.C. R. turgidus sp. nov.D. R. abdominalisAndersen & Chen, 1995. E. R. anderseni Tran & Yang, 2006. F. R. chinensis Hungerford & Matsuda, 1959. G. R. edentatus Andersen & Chen, 1995. H. R. gongvo Tran & Yang, 2006. I. R. lundbladi (Hungerford, 1957). J. R. malaisei Andersen & Chen, 1995. K. R. recurvus Andersen & Chen, 1995. L. R. scorpio Andersen & Chen, 1995. M. R. svenhedini (Lundblad, 1934), apterous form. N. R. svenhedini, macropterous form. O. R. takahashii Esaki, 1923, dealated macropterous form. Scale bar = 3 mm.

Fig. 5. Photographs of bodies of Rhyacobates spp. in lateral view (apterous females). A. R. bui sp. nov. B. R. elongatus sp. nov.C. R. turgidus sp. nov.D. R. abdominalisAndersen & Chen, 1995.E. R. anderseni Tran & Yang, 2006. F. R. angustus Tran & Nguyen, 2016, holotype (ZVNU). G. R. chinensis Hungerford & Matsuda, 1959. H. R. constrictus Tran & Nguyen, 2016. I. R. edentatus Andersen & Chen, 1995. J. R. gongvo Tran & Yang, 2006. K. R. lundbladi (Hungerford, 1957). L. R. malaisei Andersen & Chen, 1995. M. R. recurvus Andersen & Chen, 1995. N. R. scorpio Andersen & Chen, 1995. O. R. svenhedini (Lundblad, 1934). P. R. takahashii Esaki, 1923. Q. R. zetteli Tran & Nguyen, 2016. Scale bar = 3 mm.

Fig. 6. Proctiger of Rhyacobates spp. in dorsal view (males). A. R. bui sp. nov. B. R. elongatus sp. nov. C. R. turgidus sp. nov. D. R. abdominalis Andersen & Chen, 1995. E. R. anderseni Tran & Yang, 2006. F. R. angustus Tran & Nguyen, 2016. G. R. chinensis Hungerford & Matsuda, 1959. H. R. constrictus Tran & Nguyen, 2016. I. R. edentatus Andersen & Chen, 1995. Scale bar = 0.2 mm.

Fig. 8. Paramere of Rhyacobates spp. in lateral view. A. R. bui sp. nov. B. R. elongatus sp. nov. C. R. turgidus sp. nov. D. R. abdominalis Andersen & Chen, 1995. E. R. anderseni Tran & Yang, 2006. F. R. chinensis Hungerford & Matsuda, 1959. G. R. edentatus Andersen & Chen, 1995. H. R. lundbladi (Hungerford, 1957). I. R. malaisei Andersen & Chen, 1995. J. R. recurvus Andersen & Chen, 1995. K. R. scorpio Andersen & Chen, 1995. L. R. svenhedini (Lundblad, 1934). M. R. takahashii Esaki, 1923. Scale bar = 0.2 mm.

Fig. 17. Photographs of Rhyacobates elongatus sp. nov. A–B. Holotype, apterous female (ZVNU). A. Lateral view. B. Habitus, dorsal view. C. Habitus of paratype, apterous male (ZVNU), dorsal view. Scale bar = 3 mm.

Fig. 18. Morphological features of Rhyacobates elongatus sp. nov. A. Body of female, dorsal view. B. Body of female, excluding head and prothorax, ventral view. C. Body of female, lateral view. D. Abdominal end of female, dorsal view. E. Abdominal end of female, ventral view. F. Abdominal end of female, lateral view. G. Body of male, dorsal view. H. Body of male, excluding head and prothorax, ventral view. I. Basal part of right middle leg of male, ventral view. J. Proctiger of male, dorsal view. K. Left paramere, lateral aspect, two different views. Scale bars: A–I = 1 mm; J–K = 0.2 mm.

Fig. 2. Habitus of Rhyacobates spp. in dorsal view (females), apterous form if not stated otherwise. A. R. abdominalisAndersen & Chen, 1995.B. R. chinensis Hungerford & Matsuda, 1959.C. R. lundbladi (Hungerford, 1957). D. R. scorpio Andersen & Chen, 1995. E. R. svenhedini (Lundblad, 1934). F. R. takahashii Esaki, 1923, dealated macropterous female. Scale bar = 3 mm.