Omalium latissimum, 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 : 178-180

Omalium latissimum sp.n.

( Figs. 18–25 )

Type material examined: Holotype ♁ ( Fig. 18 ; dissected; almost the entire left paramere ( Fig. 21 ) missing): ‘ TAIWAN Chiai | Hsien , Alishan | 2200m 26.IV.1990 | A. Smetana [T25]’ <printed>, ‘HOLOTYPE | Omalium | latissimum sp.n. | Shavrin A.V. des. 2023’ <red, printed> ( CNC).

Paratype 1 ♀ (dissected): ‘ TAIWAN — Chiay Co. | Alishan, Road 18 to | Youth Activ. Centre , | 2000 m, tree base hollow | 7.I.2009, leg. [S.] Vit [013]’ <printed>, ‘PARATYPE | Omalium | latissimum sp.n. | Shavrin A.V. des. 2023’ <red, printed> (cSh).

Description. Measurements (n=2): HW: 0.55; HL: 0.40; AL (holotype): 0.99; OL: 0.15; TM: 0.08; PL: 0.51– 0.55; PW: 0.67–0.69; ESL: 0.85–0.86; EW: 0.92; AW: 0.90–0.91; MTbL (holotype): 0.45; MTrL (holotype): 0.24 (MTrL 1–4: 0.07; MTrL 5: 0.17); AedL: 0.65; TL: 2.75–2.80 (holotype).

Habitus as in Fig. 18 . Body dark-brown, with reddish-brown lateral and basal portions of pronotum, elytra and apical abdominal tergites; antennomeres 6–11 brown; mouthparts, antennomeres 1–5 and legs yellow-brown. Head with dense, large and deep punctation, sparser in middle of vertex and denser in middle and infraorbital portions; punctation of pronotum about as that on head, sparser and finer in mediobasal portion; scutellum without punctures; punctation about as that on pronotum, coarser and deeper in mediobasal and lateral portions, finer and sparser in middle along suture.

Head with slightly elevated middle and moderately strongly elevated infraorbital portions, 1.3 times as broad as long, temples 1.8 times as long as longitudinal length of eyes, gradually rounded toward neck; anteocellar foveae very deep and somewhat linear, reaching level of posterior third of eyes; each latero-apical portion between margins of eyes and antennal insertion with two ridges extending to level of middle length of eyes; distance between ocelli about 1.7 times as long as distance between ocellus and posterior margin of eye. Antennomeres reaching basal third of pronotum when reclined, antennomere 7 slightly and antennomeres 8–10 distinctly transverse; antennomere 2 narrower than basal antennomere, 3 slightly shorter than 2, 4–5 shorter than 3, 6 slightly longer and broader than 5, 7 slightly shorter and broader than 6, 8–9 slightly broader than 7, 10 slightly shorter than 9.

Pronotum 1.2–1.3 times as broad as long, 1.2 times as broad as head, widest in about anterior third, gradually narrowing toward slightly protruded apicad obtuse anterior angles and relatively sharply narrowing toward obtuse posterior angles; anterior margin widely rounded, about as long as posterior margin; each latero-apical portion of disc of pronotum slightly elevated but without distinct narrow ridges; paramedian impressions indistinct (holotype) or distinct (paratype), moderately wide and long.

Elytra 1.3 times as long as pronotum; surface between punctures without elevations.

Metatarsi 1.8 times as long as metatibia.

Abdomen slightly narrower than elytra, with two very small oval wing-folding patches in middle of abdominal tergite IV.

Male. Posterior margin of abdominal tergite VIII truncate ( Fig. 19 ). Posterior margin of abdominal sternite VIII widely rounded ( Fig. 20 ). Aedeagus with wide basal portion gradually narrowed toward middle, with very wide and long median lobe, from middle gradually narrowing toward widely rounded apex; parameres narrow, short, reaching middle of median lobe, with three long apical setae; internal sac wide and short, with two long fields of elongate thorns and two narrow, elongate, curved sclerotized structures in basal portion ( Fig. 21 ). Lateral aspect of the aedeagus as in Fig. 22 .

Female. Posterior margin of abdominal tergite VIII ( Fig. 23 ) and sternite VIII ( Fig. 24 ) truncate. Female genital segment as in Fig. 25 ; accessory sclerite with broad basal portion and elongate moderately narrow median portion, gradually narrowed apicad.

Comparative notes. According morphological features provided by Zanetti (1987) and Shavrin (2020b), the new species belongs to the oxyacanthae group. Based on the general shape of the body and the aedeagus, O. latissimum sp.n. is somewhat similar to O. nigrum Coiffait, 1982 , known from Nepal ( Coiffait 1982). The new species can be distinguished from O. nigrum by the smaller body, paler coloration and significantly broader median lobe.

Distribution. The new species is known from two localities in Chiayi Hsien, Alishan Range in southern part of Taiwan.

Bionomics. Specimens were taken by sifting forest floor litter and organic debris in tree base hollow at elevations from 2000 to 2200 m a.s.l.

Etymology. The specific epithet is the Latin adjective latissimus, - a, - um (very broad). It alludes to the broad median lobe.

Figures

FIGURES 18–25. Omalium latissimum: 18–habitus (holotype), 19–male tergite VIII (dorsal view), 20–male sternite VIII (ventral view), 21–aedeagus (parameral view), 22–aedeagus (lateral view), 23–female tergite VIII (dorsal view), 24–female sternite VIII (ventral view), 25–female genital segment. Scale bars: 0.1 mm.