Rhyacobates

Tran, A. D. & Nguyen, X. Q., 2016, Three new species of the water strider genus Rhyacobates Esaki, 1923 (Hemiptera: Gerridae) from Vietnam, Zootaxa 4121 (5), pp. 501-516 : 502

Key to species of Rhyacobates occurring in Vietnam

1. Both sexes: mesonotum totally black, without yellow marking. Female: abdominal sternum 7 without connexival process, connexival and posterolateral margins expanded, folded inwards and covering dorsum of genitalia ( Figs. 34–39 )................................................................................................ R. constrictus sp.n.

- Both sexes: mesonotum with median yellow marking. Female: abdominal sternum 7 with connexival process, connexival and posterolateral margins not modified as above............................................................... 2

2. Male: mesonotum with slender yellow median stripe only on posterior half. Female: posterior margin of metanotum with a conspicuous median process; abdomen short, ventral length of abdomen about 0.2 times body length.......... R. anderseni

- Male: mesonotum with yellow median marking distinctly longer than half the length of mesonotum. Female: metanotum without median process; abdomen longer, ventral length of abdomen about 0.4–0.5 times body length.................. 3

3. Body length of male at least 7.3 mm, of female at least 9.8 mm. Female: tergum 7 with median process on posterior margin. 4

- Body length of male at most 7.0 mm, of female at most 10.0 mm. Female: tergum 7 with posterior margin straight, without median process....................................................................................... 5

4. Male: pronotum chiefly yellow; mesonotum with broad, sub-oval yellow median marking; metanotum with broad crownshaped yellow marking ( Fig. 12 ). Female: sternum 7 with short connexival processes; posterior margin of sternum 7 bilobate ( Figs. 21, 22 ).............................................................................. R. zetteli sp.n.

- Male: both pronotum and mesonotum with slender yellow median marking; metanotum without yellow marking. Female: sternum 7 with longer and sub-triangular connexival processes ( Figs. 8, 10 ); posterior margin of sternum 7 without lobe, broadly convex ( Fig. 9 ).................................................................... R. angustus sp.n.

5. Male: yellow stripe on mesonotum about three quarters of mesonotum length, not reaching anterior margin; paramere without hook-shaped apex. Female: abdomen straight, abdominal segment 7 with two long dorsal processes, posterior ventral margin straight and without median projection............................................................. R. gongvo

- Male: yellow stripe on mesonotum almost as long as mesonotum length; paramere with hook-shaped apex. Female: distal half of abdomen curved upwards; abdominal segment 7 without long dorsal process, posterior ventral margin with small and pointed median projection.................................................................... R. abdominalis

Figures

FIGURES 27 – 39. Morphological features of Rhyacobates constrictus sp. n. (27) right fore leg of female. (28) basal part of right middle leg of male, ventral view. (29) proctiger. (30 – 32) left paramere from three different views. (33) endosomal sclerites. (34) body of female, lateral view. (35) apex of abdomen of female, lateral view. (36) abdomen of female holotype, dorsal view. (37) apex of abdomen of female holotype, ventral view. (38, 39) apex of abdomen of female paratype, dorsal and ventral view.

FIGURES 11 – 13. (11) Habitat of type locality of Rhyacobates zetteli sp. n. (12, 13) Habitus of R. zetteli sp. n. (12) apterous male. (13) apterous female (photographed by Tran Anh Duc).

FIGURES 14 – 23. Morphological features of Rhyacobates zetteli sp. n. (14) right fore leg of female. (15) basal part of right middle leg of male, ventral view. (16) proctiger. (17, 18) left paramere, two different views. (19) endosomal sclerites. (20) body of female, lateral view. (21 – 23) apex of abdomen of female, dorsal, ventral, and lateral views respectively.

FIGURES 1 – 10. Morphological features of Rhyacobates angustus sp. n. (1) right fore leg of female. (2) basal part of right middle leg of male, ventral view. (3) proctiger of male. (4, 5) left paramere, from different views. (6) endosomal sclerites. (7) body of female, lateral view. (8) abdomen of female, dorsal view, (9, 10) apex of abdomen of female, ventral and lateral views.