Omalium amplissimum, Shavrin, 2023

Shavrin, Alexey V., 2023, A revision of the genus Omalium Gravenhorst, 1802 (Coleoptera: Staphylinidae: Omaliinae) of the Himalayan region, Zootaxa 5369 (2), pp. 151-206 : 162-164

3.2.2.2.1. Omalium amplissimum sp. n.

( Figs 11 , 19 , 24 , 27–29 )

Type material. Holotype ♁: ‘E-NEPAL,D: Taplejung | E-slope Pathibara | 3500–3750m, 13.V. | 2016.leg. J.Schmidt | 27°26’N, 87°46’E’ <printed>, ‘HOLOTYPE | Omalium | amplissimum sp. n. | Shavrin A.V. des. 2023’ <red, printed> (NME).

Paratypes: 1 ♁ (dissected), 1 ♀ (dissected): same data as the lectotype, with additional red printed label : ‘ PARATYPE | Omalium | amplissimum sp. n. | Shavrin A.V. des. 2023’ (1 ♁: cSh; 1 ♀: NME).

Redescription. Measurements (n=3): HW: 0.50–0.57; HL: 0.38–0.42; OL: 0.12–0.16; TL: 0.08–0.11; AL (averaged): 1.12; PL: 0.37–0.43; PWmax: 0.57–0.65; PWmin: 0.51–0.62; ESL: 0.78–0.99; EW: 0.78–0.94; MTbL (averaged): 0.40; MTrL (averaged): 0.21 (MTrL 1–4: 0.09; MTrL 5: 0.12); AW: 0.81–0.90; AedL: 0.42; BL: 2.70– 3.50.

Habitus as in Fig. 24 . Body reddish-brown, with slightly paler lateral portions of pronotum and elytra; paratergites yellowish-brown; antennomeres 6–11 and mouthparts reddish; antennomeres 1–5 and legs yellow-brown. Punctation of head irregular, dense and deep, finer and sparser on apical portion of clypeus, very dense and deep in middle portion between anteocellar foveae, with interstices between punctures as broad as one nearest puncture, laterobasal portions between eyes and anteocellar foveae with dense and deep punctation; nuchal constriction with moderately dense and fine punctation; punctation of pronotum dense and deep, about as that on middle portion of head, finer and sparser on lateral portions and significantly sparser in mediobasal third; scutellum without punctures; punctation of elytra about as that on pronotum, coarser and denser in basal portion and around scutellum, slightly sparser in middle portion of each elytron and relatively finer along suture; abdominal tergites with very indistinct, fine and sparse punctation. Anterior portion of head with dense transverse microreticulation, anterioapical depressions with dense and coarse subdiagonal meshes, infraorbital portions without or with fine longitudinal meshes; nuchal constriction with dense and fine isodiametric sculpture; pronotum without microreticulation or with fine and sometimes indistinct transverse meshes in medioapical portion; scutellum with fine isodiametric microsculpture or without it; elytra without or with very fine diagonal (middle portion) or longitudinal (apical portion) microreticulation between punctures.

Head 1.3 times as broad as long, with moderately broad clypeus and strongly convex supra-antennal elevations, posteriolateral margins of clypeus stretching posteriad toward level of middle or posterior third length of eyes. Lateral portions of clypeus with deep and long anteriomedian depressions, slightly longer or reaching level of anterior margin of eyes. Middle portion between eyes and infraorbital portions distinctly elevated. Dorsal surface with narrow diagonal and elongate elevations between punctures in laterobasal portions of clypeus and on infraorbital area. Middle portion between eyes with narrow longitudinal elevations between punctures; each lateral portion between clypeus and eye with narrow elongate wrinkle markedly stretching laterad toward temple and with additional moderately short diagonal one to two wrinkles between it and posterior margin of eye. Anteocellar foveae very deep and moderately long, slightly convergent latero-apicad toward level of about anterior third of eyes. Temples 1.4–1.5 times as long as longitudinal length of eyes, with rounded temporal angles, with indistinct and very obtuse postocular ridges. Ocelli large and convex, located distinctly behind level of postocular ridges, distance between ocelli about twice as long as distance between ocellus and posterior margin of eye. Antennomeres 4–10 progressively broadened apicad, apical six antennomeres with strong pubescence; scape about two and a half times as long as broad, antennomere 2 oblong, distinctly narrower than scape, 3 distinctly narrower and slightly shorter than 2, 4 small, suboval, about as long as broad, distinctly shorter than 3, 5 slightly longer than 4, 6–7 slightly longer and broader than 5, 8 sightly longer and broader than 7, 9–10 slightly broader than 8, apical antennomere 1.1–1.3 times as long as 10, from middle gradually narrowed toward rounded apex.

Pronotum relatively small and slightly convex, 1.5 times as broad as long, slightly broader than head, widest in apical third, gradually rounded anteriad and distinctly narrowing posteriad toward obtuse posterior angles. Apical angles not protruded anteriad.Anterior margin rounded, slightly concave in middle and distinctly shorter than slightly rounded basal margin. Surface of disc with two indistinct or distinct wide longitudinal depressions, broadened basad; one paratype with additional narrow and moderately deep longitudinal depression in medioapical portion; laterobasal portions deeply and widely impressed; each lateroapical portion with curved narrow elevation reaching middle of pronotum; surface between all pronotal depressions strongly and widely elevated. Median surface of disc without or with diagonal and transverse elevations between punctures.

Elytra about as long as broad, slightly more than twice as long as pronotum, subparallel or indistinctly broadened in posterior portion.Lateral margins marginated, hind margins straight.Middle surface of each elytron with transverse and diagonal (basal portion) or longitudinal (middle and apical portions) elevations between punctures.

Abdomen convex, about as broad as or slightly narrower than elytra.

Male. Antennomeres 8–10 slightly transverse. Posterior margin of abdominal tergite VIII straight or slightly rounded. Posterior margin of abdominal sternite VIII rounded.Aedeagus wide and moderately short, with wide basal portion, gradually narrowed toward middle, with short median lobe, from widest basal portion gradually narrowed to middle and from middle distinctly broadened apicad toward slightly broadened apical portion with truncate apical margin and very small subacute apex; mediolateral portions with elongate sclerotized accessory plates, slightly curved and rounded apically and connected with middle part of median lobe; parameres very wide, significantly longer than apex of median lobe, from widest middle gradually narrowed apically, with four moderately long apical setae and additional short preapical seta located on inner side of each paramere; internal sac narrow and long, with two fields of elongate spines in middle and basal portions ( Fig. 27 ). Lateral aspect of the aedeagus as in Fig. 28 ; apical portion of median lobe moderately narrow ( Fig. 29 ).

Female. Antennomeres 8–10 less transverse. Posterior margins of abdominal tergite VIII and sternite VIII rounded. Accessory sclerite moderately short, with wide basal portion, gradually narrowed toward acute apex ( Fig. 11 ). Spermatheca not recognized.

Comparative notes. Based on the general shape of the forebody and the shape of wide basal portion of the aedeagus, O. amplissimum sp. n. is similar to O. bilobum sp. n., from which it can be distinguished by the broader antennomeres 7–9, coarser punctation and microsculpture of the head and the pronotum, the shape of the pronotum widest in apical third, with apical angles not protruded anteriad, the slightly narrower and longer elytra, different shapes of the apical portion of the median lobe and significantly longer parameres, and details of the internal structure of the internal sac. Omalium amplissimum sp. n. can be distinguished from all species of the genus by shapes of apical portion of the median lobe and very wide parameres.

Distribution. Omalium amplissimum sp. n. is known only from the type locality in eastern Nepal ( Fig. 19 ).

Etymology. The specific epithet is the Latin adjective amplissimus, - a, - um (very wide). It alludes to the very broad basal portion of the aedeagus and the parameres.

Bionomics. Specimens were collected by sifting leaf litter at elevations from 3500 to 3750 m a.s.l.

Figures

FIGURE 19. Distribution of Omalium in the Himalayan region: O. acutangulum sp. n. (circles), O. amplissimum sp. n. (star), O. beesoni (squares), O. cariosum (diamonds), O. flavotestaceum sp. n. (triangles).

FIGURES 8–18. Female accessory sclerite (Figs 8, 10–16, 18) and spermatheca (Figs 9, 17) of Omalium: 8–9—O. acutangulum, 10—O. amicorum, 11—O. amplissimum, 12—O. bilobum, 13—O. alticola, 14—O.beesoni, 15—O. altivagans, 16–17—O. marginatum, 18—O. scapulare. Scale bar: 0.1 mm.

FIGURES 24–26. Habitus of Omalium: 24—O. amplissimum (paratype), 25—O. bilobum (paratype), 26—O. altivagans (Kashmir). Scale bars: 1.0 mm.

FIGURES 27–29. Aedeagus of Omalium amplissimum (paratype): 27—aedeagus, parameral view, 28—aedeagus, lateral view, 29—median lobe, lateral view. Scale bar: 0.1 mm.