Pagastia Oliver, 1959

Makarchenko, Eugenyi A. & Hansen, Dean C., 2020, Pagastia (P.) donoliveri sp. nov. - a new Nearctic alpine stream chironomid species (Diptera: Chironomidae: Diamesinae) from the Beartooth Mountains, Wyoming U. S. A., Zootaxa 4755 (1), pp. 171-176 : 175

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) ( Makarchenko 2019, 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 distally. 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) ( Makarchenko 2019, Figs.16–17)

4. Gonostylus subapically with “heel”................ P. (P.) nivis (Tokunaga, 1936) ( Makarchenko 2006, Fig. 180, 5–10)

– Gonostylus subapically without “heel”.................................................................... 5

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

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

6. Anal point absent. Alula as well as M 1+2, M 3+4, and Cu 1 of wing with setae................................................................................ .. P. (P.) subletteorum Makarchenko ( Makarchenko 2019, Figs. 1–6 , 19–20)

– Anal point present. Alula and M 1+2, M 3+4, Cu 1 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 broad in distal part........................................... 10

8. Anal point with rounded apex and without apical peg.. P. (P.) orthogonia Oliver, 1959 ( Makarchenko 2019, Figs. 7 –13, 21)

– Anal point with pointed apical peg........................................................................ 9

9. Gonostylus with small basal lobe in outer side; apically rounded, without “heel”. AR 1.56–1.75............................................................................. P. (P.) hidakamontana Endo, 2004 ( Endo 2004, Figs. 1–6 )

– Gonostylus with rounded basal lobe in outer side and with lobe like “heel” apically. AR 1.22–1.26........................................................................................ P. (P.) donoliveri sp. nov. ( Figs. 4 , 6, 7, 9 )

10. 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, Fig. 17)

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

Figures

FIGURES 1–3. Pagastia (P.) donoliveri sp. nov., male. 1, head in frontal view; 2, pronotum and mesonotum in dorsal view; 3, part of thorax in lateral view.

FIGURES 4–5. Pagastia (P.) donoliveri sp. nov., male. 4, hypopygium in dorsal view; 5, lateral aedeagal lobes. Scale bars: 50 µm.

FIGURES 6–9. Pagastia (P.) donoliveri sp. nov., male. 6–7, parts of hypopygium in dorsal view; 8, apex of anal point with peg; 9, gonostylus.