Key to the Leuctridae Klapálek, 1905 known from or expected in the Korean Peninsula

1. Tergum X and paraprocts modified. Males................................................................. 2.

- Tergum X and paraprocts unmodified. Females............................................................ 19.

2. Paraprocts forming a long subanal probe curved up over tergum IX. Body larger than 10 mm ....................................................................... Megaleuctra Neave, 1934; M. saebat Ham & Bae, 2002 (South Korea)

- Paraprocts curve back over tergum X at maximum. Body smaller than 10 mm ..................................... 3.

3. Paraprocts divided into paired sclerites.................................................................... 4.

- Paraprocts united into a single, though sometimes complex organ............................................... 5.

4. Inner paraproct lobe forming a specillum much longer than the reduced outer (main) paraproct lobe. No projections on terga VI–VII................................. Despaxia Ricker, 1943; D. asiatica Zwick, 2010 ( North Korea, South Korea)

- Specillum not much longer than the elongated apex of the outer paraproct lobe. With tergal projections on terga VI–VII (Figs. 1–2).................... Leuctra Stephens, 1836; L. fusca tergostyla Wu, 1973 (China, Russia, North Korea, South Korea)

5. Tergum X undivided, sometimes with median furrow (Figs. 8–9). Paraleuctra Hanson, 1941 ......................... 7.

- Tergum X divided into hemiterga (Fig. 11)................................................................. 6.

6. Tergum X with central plate between hemiterga. Sternum IX without posterior prolongation.... Rhopalopsole Klapálek, 1912 (Oriental Realm, Palaearctic China and Japan; not yet known from Korea)

- Tergum X without central plate, hemiterga nearly touching (Fig. 11). Sternum IX with distinct posterior prolongation (Fig. 12). Perlomyia Banks, 1906 ............................................................................... 10.

7. Cercus with a single apical projection........ P. okamotoa (Claassen, 1936) (Russia and Japan; not yet reported from Korea)

- Cercus forked or with pair of apical teeth (Fig. 4)............................................................ 8.

8. Cercus forked. Subanal probe without distinct apical lobes......... P. cercia (Okamoto, 1922) (Russia, Japan, South Korea)

- Cercus with two apical teeth. Subanal probe with apical lobes (Fig. 5)........................................... 9.

9. Ventral lobes larger than dorsal lobe at the apex of subanal probe (Fig. 7)............ P. malaisei Zwick, 2010 (South Korea)

- Dorsal lobe larger than ventral lobes at the apex of subanal probe (Fig. 6)..... Paraleuctra paramalaisei sp. n. (South Korea)

10. Cercus globular, without apical spine (Fig. 23)............................................................. 11.

- Cercus elongated and/or with apical spine (Fig. 19)......................................................... 15.

11. Tergum X with a pair of mesal knobs (e.g. Fig. 19).......... P. mahunkai (Zwick, 1973) (Russia, North Korea, South Korea)

- Tergum X without knobs or spines (Fig. 11)............................................................... 12.

12. Tergum IX with distinct posteromedial lobe (Fig. 16)....................... P. koreana sp. n. ( North Korea, South Korea)

- Tergum IX with paired lobe (Fig. 11), or lobe vestigial or lacking (Fig. 19)....................................... 13.

13. Epiproct with undivided base, apical half abruptly bent foreward (Figs. 23, 25)..................................................................................... P. martynovi (Zhiltzova, 1975) (Russia, North Korea, South Korea)

- Epiroct with divided base, apical part claw-like (Figs. 11, 13)................................................. 14.

14. Apex of epiproct evenly bent and tapering, its tip is straight............................................................................................ P. smithae Nelson & Hanson, 1973 (China, Russia, North Korea, South Korea)

- Apex of epiproct dilated above the callus, its tip is slightly curved towards its base (Fig. 13).................................................................................................... Perlomyia baei sp. n. (South Korea)

15. Cercus short (Fig. 19)............................................... P. lamellata sp. n. ( North Korea, South Korea)