Key to the known species of Pagastia Oliver of Holarctic region

Males

1. Eyes hairy. Aedeagal lobes reduced (subgenus Hesperodiamesa Sublette). Basal lobe of gonocoxite small..................................................................................... P. (H.) sequax (Garrett, 1925) (Fig. 18)

- Eyes bare or pubescent. One or two aedeagal lobes present (subgenus Pagastia Oliver). Basal lobe of gonocoxite large.... 2

2. Both median and lateral aedeagal lobes present. AR 2.5-4.2.................................................... 3

- Only lateral aedeagal lobe present. AR 1.0–2.42............................................................. 6

3. Antepronotum with dorsal and lateral setae in widely separated groups. Median aedeagal lobe digitated and widest in distal part................................................................................................ 4

- Antepronotum completely covered with setae. Median aedeagal lobe widest medially, then tapering abruptly and with the apex forming a sharp hook.......................................... P. (Pagastia) partica (Roback, 1957) (Figs.16–17)

4. Gonostylus subapical with "heel".................... P. (P.) nivis (Tokunaga, 1936) (Makarchenko 2006, Fig. 180, 5–10)

- Gonostylus subapical without "heel"...................................................................... 5

5. Apex of the gonostylus is angled.............. P. (P.) orientalis (Tshernovskij, 1949) (Makarchenko 2006, Fig. 181, 1–5)

- Apex of the gonostylus is broadly rounded............................................................................................. P. (P.) altaica Makarchenko, Kerkis et Ivanchenko, 1997 (Makarchenko et al. 1997, Fig. 1)

6. Anal point absent. AR 1.0–1.2. Alula of wing with some setae............. P. (P.) subletteorum sp. nov. (Figs. 1–6, 19–20)

- Anal point present. AR 1.54–2.42. Alula without setae........................................................ 7

7. Anal point almost parallel-sided in dorsal view; lateral aedeagal lobe tapering to thin apex........................... 8

- Anal point tapering to apex; lateral aedeagal lobe wide in distal part............................................. 9

8. Anal point with rounded apex and without apical peg.................... P. (P.) orthogonia Oliver, 1959 (Figs. 7–13, 21)

- Anal point with pointed apical peg. AR 1,56–1.75............. P. (P.) hidakamontana Endo, 2004 (Endo 2004, Figs. 1–6)

9. Anal point narrow, tapering to pointed apex, without apical peg; gonostylus in basal part with outer angle-shaped projection. AR 2.18–2.42................ P. (P.) tianmumontana Makarchenko et Wang, 2017 (Makarchenko &Wang 2017, Figs. 17)

- Anal point widest in basal part and thin apically, pointed and often with apical peg; gonostylus without outer basal projection. AR 1.81–2.10............................... P. (P.) lanceolata (Tokunaga, 1936) (Makarchenko 2006, Fig. 180, 1–4)