Omalium, Gravenhorst, 1802

Shavrin, Alexey V., 2025, Review of the genus Omalium Gravenhorst, 1802 (Coleoptera: Staphylinidae: Omaliinae: Omaliini) of Siberia and Far Eastern Russia, with notes on some species from Mongolia and Japan, Zootaxa 5646 (2), pp. 199-235 : 230-231

3.3. Key to species of Omalium of Siberia, Far Eastern Russia, Mongolia and Japan

1 Anteocellar foveae narrow, linear......................................................................... 2

- Anteocellar foveae deep, suboval and relatively short or distinctly elongate....................................... 3

2 Lateral portions of pronotum significantly broadened and impressed, strongly narrowed posteriad. Elytra shortened, broader than long. Median lobe relatively narrow ( Fig. 6 ). Female accessory sclerite as in Fig. 14 . Body length: 2.72–3.45 mm. Habitus as in Fig. 2 . Western Siberia ...................................................................... golovatchi

- Lateral portions of pronotum narrowly impressed, slightly narrowed posteriad. Elytra elongate, distinctly longer than broad. Median lobe distinctly broadened in middle ( Fig. 11 in Shavrin & Khachikov (2023)). Female acessory sclerite as in Fig. 48u in Zanetti (1987). Body length: 2.50–3.50 mm. Habitus as in Fig. 1 in Shavrin & Khachikov (2023). Palaearctic region................................................................................................... caesum

3 Lateroapical portions of pronotum strongly protruded anteriad. Aedeagus as in Fig. 1 in Smetana (1975). Body length: 2.50– 2.80 mm. Habitus as in Fig. 41 . Mongolia............................................................ scabrum

- Lateroapical portions of pronotum not or slightly protruded anteriad............................................. 4

4 Elytra yellow-brown................................................................................... 5

- Elytra distinctly darker................................................................................. 8

5 Pronotum relatively small, slightly transverse. Median lobe short and broad; parameres strongly elongate (Fig. 64 in Watanabe (1990)). Body smaller: 2.10–2.20 mm. Japan............................................................ tenue

- Pronotum larger, distinctly transverse. Median lobe long and narrow; parameres distinctly shorter. Body larger........... 6

6 Apical angles of pronotum slightly narrowed anteriad. Lateroapical part of median lobe (if see laterally) with several elongate teeth ( Fig. 29 ). Female accessory sclerite as in Fig. 16 . Body length: 3.25–4.00 mm. Habitus as in Fig. 34 . Kuril islands................................................................................................. kurilicum

- Apical angles of pronotum widely rounded anteriad. Lateroapical part of median lobe different........................ 7

7 Elytra slightly broader than long. Aedeagus as in Fig. 38–39 . Body length: 3.17–3.70 mm. Habitus as in Fig. 35 . Russia (Maritime Province), Japan...................................................................... niponense

- Elytra slightly longer than broad. Body length: 3.70–4.10 mm. Japan....................................... shibatai

8 Antennomeres 6–10 distinctly elongate.Aedeagus as in Fig. 4 . Body length: 3.06–4.10 mm. Female accessory sclerite as in Fig. 17 . Body yellow-brown to reddish-brown. Habitus as in Fig. 1 . Eastern Siberia, Far Eastern Russia, Mongolia... longicorne

- Antennomeres 6–10 slightly or distinctly transverse. Coloration different......................................... 9

9 Body brown to reddish-brown, usually with paler elytra...................................................... 10

- Body usually darker, including elytra..................................................................... 14

10 Pronotum slightly transverse, with dense punctation......................................................... 11

- Pronotum distinctly transverse, with moderately sparse punctation............................................. 13

11 Pronotum somewhat elongate, from widest middle gradually narrowed anteriad and posteriad. Median lobe narrow and elongate; lateroapical part of median lobe relatively wide (if see laterally), forming large preapical tooth ( Fig. 36 )... Female accessory sclerite as in Fig. 15 . Body length: 2.15–3.20 mm. Habitus as in Fig. 33 . Japan, Korea,? China................. japonicum

- Pronotum distinctly transverse, from widest middle or apical third more narrowed posteriad than anteriad. Median lobe different; lateroapical part of median lobe (if viewed laterally) without preapical tooth..................................... 12

12 Median lobe wide and elongate; parameres narrow ( Fig. 46a in Zanetti 1987). Female accessory sclerite as in Fig. 48o in Zanetti (1987). Body length: 2.30–2.50 mm. Habitus as in Fig. 3 . Holarctic region............................... oxyacanthae

- Median lobe narrow, moderately short; parameres wide ( Figs 44, 46 ). Female accessory sclerite as in Fig. 19 . Body length: 1.90–2.60 mm. Habitus as in Fig. 43 . Siberia, Far Eastern Russia, Japan.................................. subsolanum

13 Laterobasal portions of pronotum slightly narrowed posteriad. Median lobe moderately short, with distinctly broadened preapical portion ( Fig. 45c in Zanetti (1987)). Female accessory sclerite as in Fig. 48e in Zanetti (1987). Body length: 3.50–4.00 mm. Holarctic region............................................................................. rivulare

- Laterobasal portions of pronotum more distinctly narrowed posteriad. Median lobe elongate, with slightly broadened preapical portion ( Figs 25, 27 ). Female accessory sclerite as in Fig. 10 . Body length: 2.25–3.70 mm. Habitus as in Fig. 23 . Norway, Siberia, Far Eastern Russia....................................................................... curtipenne

14 Body smaller: 2.20–2.38 mm. Aedeagus as in Fig. 8 . Female accessory sclerite as in Fig. 12 . Body brownish. Habitus as Fig. 24 . Japan........................................................................................ diffine

- Body about or distinctly more than 3.00 mm. Coloration darker................................................ 15

15 Pronotum slightly broader than long. Median lobe from widest middle strongly narrowed toward acute apex; lateroapical part of median lobe narrow (if see laterally), not forming preapical tooth ( Figs. 9–10 in Hayashi (2006)). Body length: 2.70–3.50 mm. Body dark brown to blackish brown. Habitus as in Fig. 1 in Hayashi (2006). Japan...................... hibernum

- Pronotum more transverse, distinctly broader than long. Median lobe different; lateroapical part of median lobe relatively wide (if see laterally), forming preapical tooth.................................................................. 16

16 Pronotum from widest middle gradually narrowed both anteriad and posteriad. Maxillary palpi yellow to yellow-brown. Median lobe significantly broadened; parameres short and narrow (Fig. 53f in Zanetti (2011). Body length: 3.00– 3.50 mm. Body brown to reddish-brown. Habitus as in Fig. 22 . Palaearctic region............................................ septentrionis

- Pronotum from widest middle or preapical third more narrowed posteriad than anteriad. Maxillary palpi distinctly darker. Median lobe narrow; parameres wide and relatively long ( Fig. 49 ). Body length: 2.40–3.10 mm. Body reddish-brown. Habitus as in Fig. 42 . Holarctic region.................................................................... strigicolle

Figures

FIGURES 4–9. Aedeagus of Omalium (Figs 4–5—O. longicorne (Russia: Amur Area, Norskiy Nature Reserve), Figs 6–7—O. golovatchi (paratype), 8–9—O. diffine (Japan: Tokyo)): 4, 6, 8—aedeagus, parameral view, 5, 7, 9—aedeagus, lateral view. Scale bar: 0.1 mm.

FIGURES 10–19. Female accessory sclerite (Figs 10, 12, 14–19) and spermatheca (Figs 11, 13) of Omalium: 10–11—O. curtipenne, 12–13—O. diffine, 14—O. golovatchi, 15—O. japonicum, 16—O. kurilicum, 17—O. longicorne, 18—O. strigicolle, 19—O. subsolanum. Scale bar: 0.1 mm.

FIGURES 1–3. Habitus of Omalium: 1—O. longicorne (holotype), 2—O. golovatchi (holotype), 3—O. oxyacanthae (Russia: Khamar-Daban Mts.). Scale bar: 1.0 mm.

FIGURES 44–49. Aedeagus of Omalium (Figs 44–47—O. subsolanum (Figs 44–45—Russia: Buryatia, valley of Irkut River; Figs 46–47—Japan:Ashiyasu-mura), Figs 48–49—O. strigicolle (Russia:AmurArea, Norskiy Reserve)): 44, 46, 48—aedeagus, parameral view, 45, 49—aedeagus, lateral view, 47—apical part of median lobe, lateral view. Scale bar: 0.1 mm.

FIGURES 41–43. Habitus of Omalium: 41—O. scabrum (paratype), 42—O. strigicolle (Russia: Maritime Province, Sikhote- Alin Nature Reserve), 43—O. clavatum (lectotype). Scale bar: 1.0 mm.

FIGURES 25–30. Aedeagus of Omalium (Figs 25–28—O. curtipenne (Figs 25–26—Russia: Magadan Area, Dukcha; Figs 27–28—O. lacki, lectotype), Figs 29–30—O. kurilicum (holotype)): 25, 27, 29—aedeagus, parameral view, 26, 30—aedeagus, lateral view, 28—apical part of median lobe, lateral view. Scale bar: 0.1 mm.

FIGURES 33–35. Habitus of Omalium: 33—O. japonicum (lectotype), 34—O. kurilicum (holotype), 35—O. niponense (holotype). Scale bar: 1.0 mm.

FIGURES 36–40. Aedeagus of Omalium (Figs 36–37—O. japonicum (Japan: Tsukuba Mt.), Figs 38–40—O. niponense (38— Japan: Futamata; 39–40—Russia: Maritime Province, Sikhote-Alin Nature Reserve)): 36, 38–39—aedeagus, parameral view, 37, 40—aedeagus, lateral view. Scale bar: 0.1 mm.

FIGURES 22–24. Habitus of Omalium: 22—O. septentrionis (Russia: TyumenArea, Ugut), 23—O. curtipenne (Russia: Irkutsk Area, Vitim Nature Reserve), 24—O. diffine (holotype). Scale bar: 1.0 mm.