Borysthenes, Stal, 1866

Key to species of genus Borysthenes View in CoL View at ENA in China (updated from Lyu & Webb 2023)

1 Tegmina markings light yellow, coastal margin with wavy undulations ( Fig. 1K–L View FIGURE 1 , Fig. 6D View FIGURE 6 ); aedeagus with 2 ventral processes sharing a common stem ( Fig. 3Q–T View FIGURE 3 )......................................... B. undulatus sp. nov. (Hainan Island)

- Tegmina markings dark brown or black, coastal margin without wavy undulations; aedeagus with or without 2 ventral processes sharing a common stem................................................................................ 2

2 Tegmina with coastal cell darkened except a slender longitudinal light-colored strip along Sc+RA ( Fig. 1A–D View FIGURE 1 ); aedeagus with 2 ventral processes sharing a common stem ( Fig. 2A, 2I View FIGURE 2 )...................................................... 3

- Tegmina not as above, with coastal cell decorated with spotted marking(s) and/or transverse band(s); aedeagus without 2 ventral processes sharing a common stem.................................................................. 4

3 Tegmina with basal one-third of CuA darkened ( Fig. 1A–B View FIGURE 1 ); male anal segment without long ventrolateral extension ( Fig. 2A View FIGURE 2 )..................................................................... B. xuzhiae sp. nov. (Hainan Island)

- Tegmina with basal one-third of CuA light-colored ( Fig. 1C–D View FIGURE 1 ); male anal segment with an extension of the right ventrolateral margin extremely long, about 3 times the length of the left ventrolateral margin ( Fig. 2I View FIGURE 2 ).................................................................................................... B. mysterius sp. nov. (Hainan Island)

4 Tegmina covered by large irregular dark spots, typically with a curved dark marking extending from icu, covering second m-cu and C3, extending to im, occupying nearly the entire C3 ( Lyu & Webb 2023, Fig. 6G View FIGURE 6 )................................................................................... B. maculatus Matsumura View in CoL ( Taiwan Island, the Ryukyu Islands)

- Tegmina not with large dark spots, second m-cu darkened, sometimes covered by an isolated rounded spot, but never covered by the extension of the dark marking that connect with im, if second m-cu covered by the extension of other marking, then it must be the extension from basal direction, of a transverse dark marking at the level of the nodal line, connecting coastal margin and icua ............................................................................................ 5

5 Tegmina markings in the form of irregular dark bands........................................................ 6

- Tegmina markings in the form of many scattered dark spots.................................................... 9

6 Tegmina with a Y-shaped dark marking with two terminals connected with coastal margin and one terminal reaching icua, usually not covering second m-cu, first m-cu not, or only with a small portion covered by this marking................. 7

- Tegmina with a transverse dark band in the middle, bifurcate posteriorly, connecting coastal margin, icua and second m-cu, first m-cu almost entirely covered by this marking ( Fig. 1I–J View FIGURE 1 ; Lyu & Webb 2023, Fig. 5A–B View FIGURE 5 )............................. 8

7 Tegmina markings thin, with a well-defined dark strip subapically, starts at apical angle and fades before the anal angle, with a V-shaped bending at the level of MP ( Lyu & Webb 2023, 2F); aedeagus with 6 processes.............................................................................................. B. hainanensis Lyu & Webb (Hainan Island)

- Tegmina markings thick and strong, subapically with large clouded marking ( Lyu & Webb 2023, Fig. 5K–L View FIGURE 5 ; Fennah 1956, Fig. 5F View FIGURE 5 ); aedeagus with 2 processes............................................. B. emarginatus Fennah View in CoL (Guangdong)

8 Aedeagus with a long and slender dorsal process curved for ca. 180 degrees, pointing caudally, endosoma with trifurcate process ( Lyu & Webb 2023, Fig. 5D View FIGURE 5 )............................................... B. acuminatus Fennah View in CoL (Hubei)

- Aedeagus without such dorsal process, endosoma with a single process ( Fig. 3I–L View FIGURE 3 )........... B. opacus sp. nov. (Guangxi)

9 Coastal cell of tegmina with one dark spot ( Fig. 1E–H View FIGURE 1 )...................................................... 10

- Coastal cell of tegmina with more than one dark spots ( Lyu & Webb 2023, Fig. 5G–H View FIGURE 5 )............................. 12

10 Tegmina with the spot in coastal cell situated near the apex, icua light-colored ( Lyu & Webb 2023, Fig. 6E View FIGURE 6 ); male pygofer strongly asymmetrical, with right lateral lobe extended caudally.................. B. lacteus Tsaur & Lee View in CoL ( Taiwan Island)

- Tegmina with a dark spot at the middle of the coastal cell, icua covered by a dark spot; male pygofer symmetrical....... 11

11 Spots on tegmina larger, in heavy dark, spot in coastal cell oval ( Fig. 1E–F View FIGURE 1 ); male anal segment with obvious ventrolateral extensions ( Fig. 3A View FIGURE 3 ); aedeagus not laterally compressed ( Fig. 3A–D View FIGURE 3 ).................. B. pantherinus sp. nov. (Guangxi)

- Spots on tegmina smaller, clouded, spot in coastal cell concaved ( Fig. 1G–H View FIGURE 1 ); male anal segment flat, without any ventral extension ( Fig. 2Q View FIGURE 2 ); aedeagus laterally compressed ( Fig. 2Q–T View FIGURE 2 )......................... B. delicatus sp. nov. (Yunnan)

12 Aedeagus with right lateral process curved downward.................................. B. congus Huang (Zhejiang)

- Aedeagus with right lateral process straight, pointing ventro-cephalad ( Lyu & Webb 2023, Fig. 5I View FIGURE 5 )................................................................................................ B. deflexus Fennah View in CoL (Guangdong)