Omalium angustissimum, 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 : 187-189

3.2.5.2.1. Omalium angustissimum sp. n.

( Figs 58 , 66–69 )

Type material. Holotype ♁ ( Fig. 58 ; right apical metatarsomere missing; dissected): ‘ NEPAL, Manaslu Mts , | Dudh Pokhari Lekh | upper Dordi Khola | Valley, 15.–17.IV.2003 | 2600– 2300 m NN | leg. J. Schmidt’ <printed >, ‘ HOLOTYPE | Omalium | angustissimum sp. n. | Shavrin A.V. des. 2023’ <red, printed> (NME).

Description. Measurements: HW: 0.55; HL: 0.37; OL: 0.14; TL: 0.08; AL: 0.93; PL: 0.43; PWmax: 0.65; PWmin: 0.57; ESL: 0.82; EW: 0.86; MTbL: 0.35; MTrL: 0.18 (MTrL 1–4: 0.05; MTrL 5: 0.13); AW: 0.87; AedL: 0.58; BL: 2.76.

Habitus as in Fig. 58 . Body dark-brown, with slightly paler elytra; antennomeres brown, with yellowish basal portions of antennomeres 2–5; mouthparts and legs yellow-brown; tarsi yellowish. Punctation of head moderately dense and large, sparser in middle portion of clypeus and on infraorbital portions, distinctly denser and coarser between eyes; nuchal constriction with moderately dense punctation; punctation of pronotum dense, about as that on middle portion of head, distinctly larger and deeper in middle and sparser in lateroapical and mediobasal portions; scutellum with several very fine punctures; punctation of elytra very dense, about as that on middle of pronotum, distinctly coarser and larger in mediobasal portions and slightly sparser and finer along suture. Anterior portion of clypeus with traces of very fine transverse microsculpture; pronotum, scutellum and elytra without microsculpture; abdominal tergites with very dense strong isodiametric microreticulation.

Head 1.4 times as broad as long, with broad clypeus and distinctly convex supra-antennal elevations, with deep and wide anteriomedian depressions, reaching level of anterior third of eyes; posteriolateral margins of clypeus stretching posteriad toward level of posterior third of eyes. Surface of head between basal margins of clypeus and middle with several irregular elongate and narrow wrinkles between punctures, portion between eyes with longitudinal elevations, infraorbital portions irregularly elevated between punctures, without longitudinal wrinkles, surface of nuchal constriction with several strongly elevated longitudinal wrinkles. Anteocellar foveae very deep and short, reaching level of basal third of eyes. Temples 1.7 times as long as longitudinal length of eyes. Distance between oceli slightly less than twice as long as distance between ocellus and posterior margin of eye. Antenna with antennomeres 5–10 progressively broadened apicad and slightly transverse antennomeres 9–10; antennomere 3 about as long as 2, 4 slightly more than twice shorter than 3, 5 slightly broader than 4, 6 slightly broader than 5, 7 broader than 6, 8 broader than 7, 9 longer and broader than 8, 10 broader than 9, apical antennomere 1.3 times as long as 10.

Pronotum 1.5 times as broad as long, 1.1 times as broad as head, widest in middle, gradually rounded toward widely rounded apical angles and strongly narrowed posteriad, with parallel-sided laterobasal margins. Surface of disc with two long and wide longitudinal depressions and suboval moderately deep depression in medioapical portion; lateral portions widely impressed, deeper in mediolateral parts, latero-basal portions distinctly impressed. Medioapical portion with irregular longitudinal elevations between punctures.

Elytra slightly broader than long, about twice as long as pronotum, from middle slightly broadened posteriad. Surface of each elytron with irregular longitudinal and diagonal elevations between punctures (mediobasal part without elevations).

Male. Posterior margin of abdominal tergite VIII rounded. Posterior margin of abdominal sternite VIII concave. Aedeagus with very wide basal portion, gradually narrowed toward middle, with narrow and long median lobe, from widest basal portion gradually narrowed apicad toward small rounded apex; mediolateral portions with elongate sclerotized accessory plates rounded apically; parameres wide, significantly shorter than apex of median lobe, with two long apical and two preapical setae; internal sac long and wide, with transverse elongate sclerotized structure in basal portion ( Fig. 66 ). Lateral aspect of the aedeagus as in Fig. 67 ; apical portion of median lobe distinctly curved apically, inner margin of median lobe with two large obtuse teeth in preapical and middle portions ( Fig. 68 ).

Female unknown.

Comparative notes. Based on the shapes of rounded temples, the pronotum widest about the middle, more narrowed posteriad than apicad, O. angustissimum sp. n. is similar to O. nigrum , from which it differs by the apical angles of the pronotum not protruded anteriad, broader parameres and details of the morphology of the aedeagus (see the key above).

Distribution. The species is known only from the type locality in Manaslu Mt., central Nepal ( Fig. 69 ).

Etymology. The specific epithet is the Latin angustissimus, - a, - um (very narrow). It alludes to the narrow median portion of the aedeagus.

Bionomics. The type specimen was collected by sifting litter at elevations from 2600 to 2300 m a.s.l.

Figures

FIGURE 69. Distribution of Omalium in the Himalayan region: O. angustissimum sp. n. (circle), O. kumari sp. n. (triangles), O. latocavum sp. n. (diamond).

FIGURES 56–58. Habitus of Omalium: 56—O. marginatum (holotype), 57—O. scapulare (Nepal, Bagmati), 58—O. angustissimum (holotype). Scale bars: 1.0 mm.

FIGURES 66–68. Aedeagus of Omalium angustissimum (holotype): 66—aedeagus, parameral view, 67—aedeagus, lateral view, 68—median lobe, lateral view. Scale bar: 0.1 mm.