Key to species of the genus Oecleopsis (males)

1 Vertex at least three times as long as broad; in lateral view highly elevated, with the posterior margin almost forming a rounded, right angle ................................................................................................................................................... 2

- Vertex less than three times as long as broad; in lateral view not so high, posterior margin not forming a right angle, but with an obtuse rounded outline (Fig. 36) ................................................................................................................ 3

2 Apex of flagellum circular, not bifurcated .................................................................................... Oecleopsis articara

- Apex of flagellum not circular, apical process bifurcated. ........................................................... Oecleopsis petasatus

3 Flagellum not terminating in a bifurcated process (Figs 10, 11) .................................................................................. 4

- Flagellum terminating in a bifurcated process (Figs 4, 5, 20, 21, 31, 32) .................................................................... 7

4 Apex of flagellum with three processes (Figs 10, 11) .................................................................................................. 5

- Apex of flagellum with four processes ........................................................................................... Oecleopsis elevatus

5 Left side of periandrium at apex of aedeagus with a short spine ............................................... Oecleopsis yoshikawai

- Left side of periandrium at apex of aedeagus without a spine...................................................................................... 6

6 Periandrium with a moderately long spine, situated on the right-dorsal margin, directed dorsocephalad..................... ......................................................................................................................................................... Oecleopsis chiangi

- Periandrium with a short spine, situated on the right side of the periandrium at the apex of the aedeagus (Fig. 11) .... .......................................................................................................................................... Oecleopsis spinosus sp. nov.

7 Rami of bifurcation symmetrical, almost equal in length (Figs 4–6) ........................................................................... 8

- Rami of bifurcation asymmetrical, unequal in length (Figs 21, 22, 32, 33) ............................................................... 10

8 Flagellum with two subapical processes (Figs 4, 5) ..................................................................................................... 9

- Flagellum with one subapical process ............................................................................................... Oecleopsis bifidus

9 Spine on right side of periandrium at apex of aedeagus very short (Fig. 4) .................................... Oecleopsis sinicus

- Spine on right side of periandrium at apex of aedeagus very long ............................................. Oecleopsis artemisiae

10 Left ramus of bifurcation rudimentary, only a small protuberance (Figs 20–22)........................................................... .................................................................................................................................... Oecleopsis tiantaiensis sp. nov.

- Left ramus of bifurcation well developed (Figs 31–33) ............................................................................................. 11

11 Length of right ramus of bifurcation about 1.8 times as long as that of left ramus, basiventral area of flagellum with- out a spine (Fig. 31) ........................................................................................................ Oecleopsis wuyiensis sp. nov.

- Length of right ramus of bifurcation about three times as long as that of left ramus, basiventral area of flagellum with a small spine .................................................................................................................................. Oecleopsis mori