Omalium golovatchi, Shavrin, 2025

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 : 208-209

3.2.2.3. Omalium golovatchi sp. nov.

( Figs 2 , 6–7 , 14 , 21 )

Type material examined. Holotype ♂ ( Fig. 2 ; dissected): ‘КемеровскаЯ обл., Заповедник | «КУЗнецкий АлатаУ», БольшаЯ | ЦерковнаЯ, 26 км ЮЮЗ | Белогорска, 1300–1450 м н.У.м., | над границей леса, 26.08.1993. | С. Головач и В. Грачёв [Kemerovo Area, Kuznetsk Alatau Nature Reserve , Bol`shaya Tserkovnaya , 26 km SSW Belogorsk, 1300–1450 m a.s.l., timberline, 26.08.1993. S. Golovatch & V. Gratchev leg.]’ <printed>, ‘HOLOTYPE | Omalium | golovatchi sp.n. | Shavrin A.V. des. 2025’ <red, printed> (ZMM) .

Paratypes: 3 ♂♂, 1 ♀ (dissected): same data as the holotype (2 ♂♂: cSh; 1 ♂, 1 ♀: ZMM) ; 2 ♂♂ (dissected) , 2 ♀♀ (dissected): ‘КемеровскаЯ обл., НовокУЗ- | нецкий р-н, Ю с.КУЗедеево, | “Липовый Остров”, бассейн | р.Кондома, склоны распадков | блиЗ р.Малый Тёш. Подстилка, | мхи, дернина под липой с | пихтой и береЗой, высокотра- | вьем, Злаками, осокой, | 20.07.1994. А.Б. Рывкин, №28 [ Kemerovo Area , Novokuznetskiy District , S Kuzedeevo vill., “Lipovyi Ostrov”, basin of Kondoma River , slopes of mountains near Malyi Tyosh River . Litter, mosses, sod under linden with fir and birch, high grasses, grains, sedges, 20.07.1994, A.B. Ryvkin leg. N28]’ <printed> ( ZMM). All paratypes with additional red printed label: ‘ PARATYPE | Omalium | golovatchi sp.n. | Shavrin A.V. des. 2025’.

Description. Measurements (n=9): HW: 0.52–0.60; HL: 0.35–0.39; OL: 0.12–0.15; TL: 0.07–0.10; AL (holotype): 1.07; PL: 0.41–0.50; PWmax: 0.65–0.77; PWmin: 0.55–0.66; ESL: 0.62–0.81; EW: 0.85–0.97; MTbL (holotype): 0.52; MTrL (holotype): 0.21 (MTrL 1–4: 0.09; MTrL 5: 0.12); AW: 0.90–1.00; AedL: 0.52–0.57; BL: 2.72–3.45 (holotype: 3.05).

Habitus as in Fig. 2 . Body yellow-brown to reddish-brown, with darker head and abdomen (lateral portions of pronotum, elytra and paratergites of abdomen paler); mouthparts, antennae and legs yellowish to yellow-brown (tarsi usually slightly paler). Head with dense and moderately large punctation, sparser and finer on clypeus and larger and denser in middle; neck with dense or moderately sparse punctation about as that in middle part of head; punctation of pronotum irregular and sparse, in medioapical portion about as that in middle of head but slightly larger, coarser and deeper, mediobasal part usually with sparser and finer punctation with median elevation sometimes without punctures in middle and mediobasal third, lateral portions with sparse and large irregular punctation (one specimen with fine and sparse punctation in middle); scutellum without punctures; punctation of elytra very dense, significantly larger, deeper and coarser than that in medioapical part of pronotum, finer around scutellum and finer and sparser along suture, each elytron with distance between punctures in middle about as long as diameter of nearest puncture; abdominal tergites with dense and fine punctation, sparser and less distinct in middle of each tergite and on abdominal tergites VI–VIII. Anterior portion of clypeus with dense transverse microsculpture, laterobasal parts of clypeus with irregular, dense and diagonal microreticulation, median and infraorbital portions without visible meshes; neck without or with fine transverse sculpture; scutellum with dense and moderately coarse isodiametric sculpture; abdomen with dense isodiametric microreticulation. Apical part of head with several erect and moderately long setae; lateral margins of pronotum with several fine and short setae, visible in some specimens; abdomen with relatively dense and short setae; anterior and posterior margins of pronotum, and posterior margin of elytra with row of very short cuticular fringe.

Head 1.4–1.5 times as broad as long, with distinctly elevated middle part and infraorbital portions, with broad clypeus and strongly distinctly explanate supra-antennal elevations; anteriomedian depressions deep, wide and elongate, each reaching level of anterior margin or anterior third of eye; posteriolateral margins of clypeus subparallel, stretching posteriad toward level of anterior third of eye. Each laterobasal portion of clypeus with irregular diagonal narrow wrinkles, infraorbital portions with irregular elevations between punctures and narrow longitudinal elevations in posterior portions, sometimes forming three to four elongate wrinkles, with significantly more elevated wrinkle on the level of lateral margin of neck; each mediodorsal margin of infraorbital portion near eye with irregular diagonal wrinkles. Anteocellar fovea sublinear, deep and elongate, each reaching level of anterior third or apical margin of eye. Temples convex, 1.5–1.7 times as long as longitudinal length of eye, from posterior margin of eyes gradually narrowed toward neck. Nuchal constriction moderately wide and deep. Ocelli small, indistinct in paler specimens; distance between ocelli about twice as long as distance between ocellus and posterior margin of eye. Antenna with elongate antennomeres 1–7, slightly elongate 8 and slightly transverse 9–10; antennomere 3 about as long as and distinctly narrower than 2, 4 slightly shorter than 3, 5 slightly longer than 4, 6 slightly broader than 5, 7 slightly broader than 6, 8 slightly shorter and broader than 7, 9–10 slightly shorter and broader than 8.

Pronotum distinctly convex in middle, with significantly broadened and impressed, flattened and explanate lateral portions, 1.5 times as broad as long, from widest middle significantly more narrowed posteriad than anteriad. Apical angles broadely widened, slightly protruded anteriad. Anterior margin widely rounded, slightly shorter than rounded posterior margin. Laterobasal margins widely concave in front of subacute hind angles. Lateral portions narrowly marginated, with distinct crenulate lateral edges, each with deep and significantly broadened elongate depressions slightly behind middle. Surface of disc with two elongate and moderately deep longitudinal depressions, broadened in mediobasal portion, with additional oval fine to moderately deep medioapical depression; each lateroapical portion with indistinct or distinct curved narrow elevation, reaching about middle of pronotum; surface between all pronotal depressions strongly and narrowly elevated. Medioapical portion with irregular diagonal and longitudinal elevations between punctures in some specimens.

Elytra short, 1.1–1.3 times as broad as long, 1.5–1.6 times as long as pronotum, flattened in middle, distinctly broadened posteriad; lateral portions widely impressed and strongly explanate; lateral margins with distinct irregular elevations, stronger in middle; hind margins straight of slightly rounded. Dorsal surface of each elytron with strong diagonal elevation between punctures. Hind wings fully developed, but moderately small.

Metatarsi distinctly more than twice shorter than metatibia.

Abdomen without wing folding patches in the middle of abdominal tergite IV and with indistinct narrow palisade fringe on apical margin of abdominal tergite VII.

Male. Posterior margin of abdominal tergite VIII straight or slightly concave. Posterior margin of abdominal sternite VIII truncate or slightly concave. Aedeagus with broadened basal portion, gradually narrowed toward middle; median lobe narrow, elongate, from middle slightly narrowed apicad toward rounded apex; mediolateral portions with short sclerotized accessory plates, slightly curved lateroapicad, each rounded apically; parameres relatively wide, significantly shorter than apex of median lobe, distinctly curved in preapical portions, each with two long apical and two long preapical setae; internal sac wide and long with two oval and two narrow sclerotized structures in basal portion ( Fig. 6 ). Lateral aspect of the aedeagus as in Fig. 7 ; apical portion gradually narrowed toward apex slightly curved ventroapicad.

Female. Posterior margin of abdominal tergite VIII straight. Posterior margin of abdominal sternite VIII rounded. Accessory sclerite with wide basal portion strongly narrowed toward narrow elongate apical part with small rounded apex ( Fig. 14 ). Spermatheca not recognized.

Comparative notes. Based on the presence of linear anteocellar foveae and the general shape of the aedeagus, O. golovatchi sp. nov. belongs to the Caesum group ( Zanetti 1987). Based on the general shape of the median lobe in parameral and lateral view, it somewhat similar to the Palaearctic O. littorale Kraatz, 1857 , known from the western Palaearctic region, including Central Asia (Shavrin 2023), but differs from it by the narrower shape of the forebody. It can be easily distinguished from all species of this group by the shape of the forebody, with significantly broadened and explanate lateral portions of the pronotum and the elytra, large, dense and coarse punctation on the significantly shortened elytra, with strong elevations between punctures, the lack of the wing folding patches in the middle of abdominal tergite IV, the morphology of the aedeagus and the shape of the female accessory sclerite.

Distribution. Omalium golovatchi sp. nov. is known only from two localities in the southern part of Kemerovo Area, Russia ( Fig. 21 ).

Etymology. Patronymic; the species is named to honour Sergei I. Golovatch (Moscow), one of the collectors of the type material.

Bionomics. Specimens were collected from 340 to 1450 m a.s.l. by sifting litter and mosses in mixed forests.

Figures

FIGURE 21. Distribution of Omalium in eastern Palaearctic region: O. golovatchi (triangles), O. subsolanum (circles).

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 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.