Key to males of species of Neoperla from Hainan Province, China.

1. Tergum 9 with a pair of small rounded nodules medially (see figs. 85–86 in Wu 1973)...................... N. binodosa

-. Tergum 9 without above mentioned nodules................................................................ 2

2. Hemitergal process of tergum 10 very long and sharp, reaching posterior margin of tergum 8 (see figs. 110–111 in Wu 1938)........................................................................................... N. longispina

-. Hemitergal process of tergum 10 not very long and sharp, not reaching tergum 8................................... 3

3. Tergum 7 with a sub-trapezoidal process, tergum 8 with an upcurved sclerite...................................... 4

-. Tergum 7 without sub-trapezoidal process, tergum 8 without upcurved sclerite..................................... 5

4. Aedeagus curved (see fig. 4 in Yang & Yang 1995)................................................ N. hainanensis

-. Aedeagus straight, process of tergum 7 with a pair of cornuted lobes laterally (see fig. 3 in Yang & Yang 1995).. N. bicornuta

5. Aedeagus without lobes (Figs. 3–4)......................................................... N. minuta sp. nov.

-. Aedeagus with lobes................................................................................... 6

6. Aedeagus exhibits an S-shaped curve laterally (see figs. 3–4 in Kong et al. 2014)......................... N. bicurvata

-. Aedeagus not S-shaped................................................................................ 7

7. Aedeagus with only two small lobes (Figs. 7–8)........................................... N. wuzhishana sp. nov.

-. Aedeagus with more than two lobes....................................................................... 8

8. Aedeagus with an elongated ventral lobe and two small dorsal lobes (see Figs. 5–6 in Kong et al. 2014).... N. furcomaculata

-. Aedeagus with more than three lobes...................................................................... 9

9. Aedeagus with four small lobes and a large lobe (see figs. 1–2 in Kong et al. 2014).......................... N. baisha

-. Aedeagus with four small lobes and two large lobes (Figs. 14–16).............................. N. sexlobata sp. nov.