Omalium alienum, Shavrin, 2023

Shavrin, Alexey V., 2023, Three new species of Omaliopsis Jeannel, 1940 and Omalium Gravenhorst, 1802 from Taiwan (Coleoptera: Staphylinidae: Omaliinae, Omaliini), Zootaxa 5244 (2), pp. 173-181 : 176-178

Omalium alienum sp.n.

( Figs. 10–17 )

Type material examined: Holotype ♁ ( Fig 10 ; dissected; left antennomeres 5–11, 1eft apical protarsomere and left mesotarsus missing): ‘ TAIWAN Hualien | Hsien, Taroko N.P. | Nanhushi Hut | 2220m 8.V.1990 | A. Smetana [T48]’ <printed>, ‘HOLOTYPE | Omalium | alienum sp.n. | Shavrin A.V. des. 2023’ <red, printed> ( CNC).

Paratypes: 1 ♀ (dissected): ‘ TAIWAN Nantou | Hsien, Houhuanshan | 3100m 20.IV.1990 | A. Smetana [T12]’ <printed> ( cSh ); 1 ♀: ‘ TAIWAN Nantou Hsien | Yushan N.P. SW slope | blw. Yushan Mn. Pk. | 3650m 14.V.1991 | A.Smetana [T80]’ ( CNC); 1 ♀ (left antennomeres 10–11 missing): ‘ TAIWAN Nantou Hsien | Yushan N.P. SW slope | blw. Yushan Mn. Pk. | 3650m 15.V.1991 | A.Smetana [T82]’ <printed> (cSh); 1 ♀ (dissected): ‘ TAIWAN Taichung Hsien | Hsueshan , above Shan- | Liu-Gieu Hut 3200m | 8- 10.V.[19]91 A.Smetana [T70]’ <printed> ( CNC). All paratypes with additional red printed label: ‘PARATYPE | Omalium | alienum sp.n. | Shavrin A.V. des. 2023’.

Description. Measurements (n=5): HW: 0.60–0.62; HL: 0.41–0.45; AL (holotype): 1.20; OL: 0.15–0.17; TM: 0.09–0.10; PL: 0.45–0.57; PW: 0.75–0.84; ESL: 0.92–1.00; EW: 1.02–1.10; AW: 0.97–1.11; MTbL (holotype): 0.57; MTrL (holotype): 1.33 (MTrL 1–4: 0.09; MTrL 5: 0.12); AedL: 0.42; TL: 2.96–3.65 (holotype: 3.20).

Habitus as in Fig. 10 . Head, pronotum, and mediobasal and apical portions of elytra in some paratypes darkbrown; lateral and basal portions of pronotum and elytra reddish brown; antennomeres 7–11 and abdomen brown (paratergites slightly paler, three paratypes with slightly darker abdominal tergites); mouthparts, antennomeres 1–6 and legs yellow-brown (maxillary palpi in one paratype darker); tarsi yellow. Head with irregular punctation: sparser and finer in apical portion between antennal insertions (apical part of head without punctures), denser and deeper in middle, sometimes with impunctate transverse area in middle between level of anterior third of eyes and/or in front of anteocellar fovea; pronotum with regular, sparse, moderately large and deep punctation; punctation of pronotum moderately large and deep, about as that on middle of head, sparser and slightly finer in middle and mediobasal portions; scutellum with several very fine punctures; punctation of elytra dense, irregular, finer and sparser in middle along suture or larger, deeper and coarser in middle (one paratype); abdomen without visible punctures. Forebody without microsculpture except for apical portion of head with distinct transverse microreticulation and scutellum with very fine transverse meshes; abdomen with distinct and dense microsculpture: transverse on abdominal tergites III–V and isodiametric on tergites VI– VIII.

Head slightly elevated in middle and infraorbital portions, 1.3–1.4 times as broad as long, with very wide clypeus gradually narrowing basad; temples moderately short, 1.6–1.7 times as long as longitudinal length of eyes; temporal angles rounded; anteocellar foveae very deep, diagonally stretching towards margins of clypeus, reaching level of middle length of eyes; each latero-apical portion between margins of eyes and antennal insertion with two moderately long ridges, ridge nearest to clypeus extending from about antennal insertion to level of middle of eye; distance between ocelli very short, about twice as long as distance between ocellus and posterior margin of eye. Eyes large, convex, markedly longer than temples. Apical palpomere of maxillary palpi more than three times as long as preceding segment. Antennomeres reaching middle or basal third of pronotum when reclined, antennomeres 6–10 with strong pubescence, antennomere 8 slightly and antennomeres 9–10 distinctly transverse; basal antennomere long, about as long as antennomeres 2–3, more than two and a half times as long as broad, antennomere 2 suboval, about twice narrower than basal antennomere, 3 narrow, about as long as 2, 4 small, slightly longer than broad, 5 slightly longer than 4, 6 slightly broader than 5, 7 slightly broader than 6, 8 slightly broader than 7, 9 slightly shorter and broader than 8, 10 indistinctly broader than 9, apical antennomere about 1.3 times as long as 10, from about middle gradually narrowed toward subacute apex.

Pronotum 1.4–1.6 times as broad as long, 1.2–1.3 times as broad as head, widest in middle, gradually narrowing towards rounded anterior angles and relatively sharply narrowing towards subacute posterior angles; anterior margin rounded, slightly protruded anteriad, about as long as rounded posterior margin or slightly shorter; each latero-apical portion of disc of pronotum with narrow semicircular ridges, reaching middle length of pronotum (some paratypes without or with indistinct ridges); paramedian impressions distinct, wide, beginning from about medio-apical portion, broadened and stretching mediobasal area; longitudinal portion between impressions distinctly elevated in some specimesn; latero-basal impressions wide and deep.

Elytra slightly broader than long, 1.1 times as long as pronotum, from basal portion slightly broadened posteriad; posterior margins straight; surface of elytra between punctures in mediobasal and middle portions slightly elevated in some paratypes. Wings fully developed.

Metatarsi more than twice shorter than metatibia.

Abdomen slightly narrower or broader than elytra, with two small and oval wing-folding patches in middle of abdominal tergite IV, with narrow palisade fringe at apical margin of tergite VII.

Male. Posterior margin of abdominal tergite VIII truncate ( Fig. 11 ). Apical margin of abdominal sternite VIII rounded ( Fig. 12 ). Aedeagus wide and short, with very wide basal portion slightly narrowed apicad; median lobe moderately wide, with somewhat rounded apical margin; dorsal plates very wide, with straight apical margins; parameres short, strongly broadened apically and strongly curved inwards, with three short apical setae, distinctly exceeding apex of median lobe; internal sac complicated, wide and long, with two long and curved sclerotized structures in basal portion ( Fig. 13 ). Lateral aspect of the aedeagus as in Fig. 14 .

Female. Posterior margin of abdominal tergite VIII truncate ( Fig. 15 ). Posterior margin of abdominal sternite VIII rounded ( Fig. 16 ). Female genital segment as in Fig. 17 ; accessory sclerite with broad basal portion, gradually narrowed apicad. Spermatheca not recognized.

Comparative notes. The new species is difficult to compare with other described species of Omalium due the unusual morphology of the aedeagus. Based on the wide median lobe and dorsal plates, O. alienum sp.n. is somewhat similar to some Western Palaearctic species of the xambeui group ( Zanetti 1987, 2002): European O. xambeui Fauvel, 1876 and Western Asian O. cribriceps Fauvel, 1900 , but differs from them by the narrow apical part of the median lobe, the different shape of the very wide parameres and different morphology of the internal sac. Omalium alienum sp.n. can be distinguished in habitus from other Taiwanese species ( O. latissimum sp.n.) by the longer body and paler abdomen, different shape of the pronotum (widest in middle) and slightly shorter elytra.

Distribution. The new species is known from several localities in Nantou Hsien, Hualien Hsien and Taichung Hsien in central Taiwan.

Bionomics. Specimens were taken by sifting forest floor litter at elevations from 2220 to 3650 m a.s.l. The holotype was collected in old coniferous forest with lust undergrowth and was taken at a large creek by sifting of wet layers of fallen leaves, accumulated at bases of large rocks close to the water (A. Smetana, pers. comm.).

Etymology. The specific epithet is the Latin adjective alienus, - a, - um (strange). It alludes to the unusal Acrolocha -shaped aedeagus.

Figures

FIGURES 10–17. Omalium alienum: 10–habitus (holotype), 11–male tergite VIII (dorsal view), 12–male sternite VIII (ventral view), 13–aedeagus (lateral view), 14–aedeagus (parameral view), 15–female tergite VIII (dorsal view), 16–female sternite VIII (ventral view), 17–female genital segment. Scale bars: 0.1 mm.