Omalium nigrum Coiffait, 1982

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 : 199-201

3.2.5.2.6. Omalium nigrum Coiffait, 1982

( Figs 91 , 96–99 )

Omalium nigrum Coiffait, 1982: 151 [HM according Herman 2001a: 38]

Type material. Holotype ♁ ( Fig. 91 ; dissected): ‘Nepal-Expedit. | Jochen Martens’ <printed>, ‘südl. Dhaulagiri | Dhorpatan | 3000–3200 m | V. 1973 ’ <printed>, ‘TYPE’ <red, printed>, ‘ Holo- [handwritten] | TYPUS’ <red label with black margins, printed; other side of the label: ‘SMF | C. 15030’ [handwritten]>, ‘ Omalium | nigrum | H. COIFFAIT det. 19[printed]79’ <handwritten in black Indian ink>, ‘ Omalium | nigrum Coiff. ’ <handwritten in blue pen>, ‘SNG-Museum | Frankfurt/Main | Loan-000299’ <printed>, ‘ Omalium | nigrum Coiffait, 1982 | Shavrin A.V. det. 2023’ <printed> (SF).

Material examined. NEPAL: SUDURPASHCHIM: 1 ♁: Mahakali / Darchula 10 km NE Ghusa, Chamliya Kh. (former village Shinae), 29°53’35’’N, 80°56’30’’E. 06– 10.06.2005. 2850 m a.s.l., bit fall traps. A. Weigel leg. (NME); BAGMATI: 1 ♁: ‘ Camp 5. NEPAL: 10500’, Chautara Dist. Choche Ridge, 12–17.vi.1983.’, ‘ Ridge Camp 5 17.vi.83’, ‘ Allen, Brendell, Robinson, Tuck, Brit. Mus. 1983-222’ (BMNH) .

Redescription. Measurements (n=3): HW: 0.52–0.55; HL: 0.35–0.39; OL: 0.15; TL: 0.08–0.10; AL (holotype): 0.96; PL: 0.42–0.45; PWmax: 0.61–0.67; PWmin: 0.53–0.55; ESL: 0.82–0.85; EW: 0.86–0.90; MTbL (holotype): 0.42; MTrL (averaged): 0.22 (MTrL 1–4: 0.07; MTrL 5: 0.15); AW: 0.82–0.87; AedL: 0.40–0.47; BL: 2.80–3.00 (holotype).

Habitus as in Fig. 91 . Body dark-brown, with reddish-brown elytra; antennomeres brown, with yellow-brown basal portions of antennomeres 2–3; mouthparts and legs yellowish. Punctation of head moderately dense, large and deep, finer and sparser on clypeus, denser and larger in middle between anteocellar foveae and on infraorbital portions; nuchal constriction with moderately dense and large punctation; punctation of pronotum dense, sparse, slightly larger and deeper than that on middle portion of head, distinctly sparser in medioapical portion and mediobasal third; punctation of elytra about as that on elytra, but slightly coarser and denser around scutellum, and slightly sparser along suture. Apical portion of clypeus with fine transverse microreticulation; pronotum and elytra without microsculpture; scutellum with fine transverse meshes.

Head 1.4 times as broad as long, with very broad clypeus and strongly converx supra-antennal elevations, posteriolateral margins of clypeus relatively strongly narrowing posteriad toward anteocellar foveae.Anteriomedian depressions very deep and wide, reaching level of anterior margins of eyes. Middle portion between eyes and infraorbital portions strongly elevated, with distinct elevations between punctures, without longitudinal wrinkles on infraorbital portions. Anteocellar foveae very deep and wide, indistinctly convergent latero-apicad, reaching level of middle length of eyes. Temples 1.5–1.8 times as long as longitudinal length of eyes, without postocular ridges. Distance between ocelli slightly more than twice as distance between ocellus and posterior margin of eye. Antenna with distinctly transverse antennomeres 9–10; antennomere 3 narrower and slightly longer than 2, 4 slightly longer than broad, about twice as long as 3, 5 slightly longer and broader than 4, 6 slightly broader than 5, 7 about as long as broad, slightly broader than 6, 8 distinctly broader than 7, 9–10 slightly longer and distinctly broader than 8, apical antennomere about 1.3 times as long as 10.

Pronotum convex, 1.4 times as broad as long, 1.2 times as broad as head, widest slightly above middle, gradually narrowed posteriad, with apical angles slightly protruded anteriad. Surface of disc with two very deep and wide longitudinal depressions, reaching mediobasal third, and with additional oval and deep longitudinal depression in medioapical portion. Median portion of disc with distinct diagonal and longitudinal elevations between punctures.

Elytra slightly broader than long, slightly less than twice as long as pronotum, indistinctly broadened in posterior portion. Middle surface of each elytron with distinct longitudinal and portions around scutellum with diagonal elevations between punctures.

Abdomen slightly narrower than elytra.

Male. Posterior margin of abdominal tergite VIII straight. Posterior margin of abdominal sternite VIII slightly concave. Aedeagus with very wide basal portion, distinctly narrowed toward middle, with very narrow and long median lobe, from widest basal portion gradually narrowing toward small rounded apex; mediolateral sclerotized accessory plates very long, widely rounded apically; parameres moderately narrow, distinctly shorter than apex of median lobe, each apical portion of paramere with two moderately short apical and preapical setae; internal sac wide and long, with four elongate sclerotized sclerites in basal portion ( Fig. 96 ). Lateral aspect of the aedeagus as in Fig. 97 ; apical portion moderately narrow, broadened in preapical portion, with distinctly crenulate inner margin ( Fig. 98 ).

Female unknown.

Comparative notes. Regarding the shape of the rounded temples and the pronotum, O. nigrum is similar to O. angustissimum sp. n., from which it can be distinguished by the shape of the apical angles of pronotum slightly protruded anteriad, narrower parameres and details of the morphology of the aedeagus (see the key above).

Distribution. Omalium nigrum is known from three localities in western and central parts of Nepal ( Fig. 99 ).

Bionomics. The type specimen was collected at elevations from 2850 to 3200 m a.s.l. The detailed bionomical data are unknown.

Remarks. Omalium nigrum was originally described based on the holotype from “ Népal, südl. Dhaulagiri, Dhorapan, 3000–3200 m ...”. I studied the holotype of O. nigrum ( Fig. 91 ), which based on the morphology of the body and the aedeagus is conspecific with other studied specimens. The internal sac of the aedeagus of the holotype is fully inflated, and it was sketchy illustrated in Fig. 253 by Coiffait (1982). The internal sac of the male from Chautara District is also completely inflated, and the left paramere of this specimen is strongly deformed. Thus, I illustrated the aedeagus of the specimen from Mahakali ( Figs 96–98 ).

Figures

FIGURE 99. Distribution of Omalium nigrum in Nepal.

FIGURES 90–92. Habitus of Omalium: 90—O. latocavum (paratype), 91—O. nigrum (holotype), 92—O. secretum (Nepal: Parbat). Scale bars: 1.0 mm.

FIGURES 96–98. Aedeagus of Omalium nigrum (Nepal: Mahakali): 96—aedeagus, parameral view, 97—aedeagus, lateral view, 98—median lobe, lateral view. Scale bar: 0.1 mm.