Euconnus bibaculatus, Jałoszyński, 2022

Jałoszyński, Paweł, 2022, Taxonomy of ' Euconnus complex'. Part XXIV. Intermediate forms between Psomophus, Eupentarius and Euconnus s. str. in the East Palaearctic fauna unify problematic subgenera (Coleoptera, Staphylinidae, Scydmaeninae), Zootaxa 5194 (3), pp. 343-391 : 368-370

Euconnus bibaculatus sp. n.

( Figs 86–91 , 113 )

Type material studied. Holotype ( Japan: Okinawa Prefecture: Iriomote-jima Is. ): ♂, two labels: “JAPAN, OKINAWA Pref. / Iriomote-jima, Funaura / FIT, 11-18.iv.2005 / T. Fukuzawa leg.” [white, printed and handwritten], “ EUCONNUS s. str. / bibaculatus m. / P. Jałoszyński, ’22 / HOLOTYPUS ” [red, printed] ( NSMT) . Paratypes (29 exx): Iriomote-jima Is.: 6 ♂♂, “JAPAN, OKINAWA Pref. / Iriomote-jima, Kanpiree / 80 m, 17-20.iii.2004, FIT / S. Nomura leg.” [white, printed] ; 2 ♂♂, “JAPAN, OKINAWA Pref. / Kanpiree, St. 1 (80 m) / Iriomote-jima / 20.iii.2004 / leg. S. Nomura ” [white, printed]; Ishigaki-jima Is .: ♂, “JAPAN, OKINAWA Pref. / Ishigaki-jima, Shiramizu , / 3-6.v.2004 / Tomayuki Tsuru leg. FIT” [white, printed] ; 2 ♂♂, “JAPAN, OKINAWA Pref. / Ishigakijima, Omoto-dake / 100 m, 15-21.iii.2004, FIT / S. Nomura leg. A1” [white, printed] ; 4 ♂♂, “JAPAN, OKINAWA Pref. / ISHIGAKI-JIMA, Kabira env. / jungle and roadside, 15 I 2017 / leg. P. JAŁOSZYŃSKI” [white, printed] ; ♂, “JAPAN, OKINAWA Pref. / ISHIGAKI-JIMA, Sokobaru / Dam env., forest, 17 I 2017 / leg. P. Jałoszyński ” [white, printed] ; 2 ♂♂, “ Mt. Omotodake / Ishigaki Is. / Okinawa Pref. ”. “ 9. iv. 1986 / S. Nomura leg” [white, printed] ; ♂, “ Mt. Omotodake / Ishigakijima Is.”, “ 22. iii. 1984 / S. Nomura leg.” [white, printed]; Yonaguni-jima Is .: 4 ♂♂, “JAPAN, OKINAWA Pref. / Yonaguni-jima , Mantabaru- / shinrin-kōn, 9-11.iii.2004 / Koji & Shiho Arai leg.” [white, printed] ; 3 ♂♂, “JAPAN, OKINAWA Pref. / Yonaguni-jima, Mt. Kubura- / dake, FIT, 9-12.ix.2004 / Koji & Shiho Arai leg.” [white, printed] ; 2 ♂♂, “JAPAN, OKINAWA Pref. / Yonaguni-jima, Mt. Inbi- / dake, Tull. , 10.ix.2004 / Koji & Shiho Arai leg.” [white, printed] ; ♂, “ Mt. Kuburadake (upside) / Yonagunijima Is. / [ Ryukyu , JAPAN] / 18.iii.2005, S. Nomura leg.” [white, printed]. Paratypes with yellow “ PARATYPUS ” labels similar to that with holotype, deposited in NSMT and cPJ .

Diagnosis. Antennal club trimerous with antennomere 9 distinctly narrower than 10; males lacking secondary sexual characters; aedeagus with pair of conspicuously long sublateral projections flanking dorsal apical plate.

Description. Body of male ( Fig. 86 ) elongate, strongly convex; pigmentation moderately to darkly brown, appendages indistinctly lighter except for clearly lighter tarsi and maxillary palps; body covered with setae distinctly lighter than cuticle; BL 1.24–1.38 mm.

Head much narrower than pronotum, broadest at eyes, HL 0.30–0.33 mm, HW 0.23–0.25 mm; tempora in dorsal view about 3 times as long as eyes, behind eyes strongly and evenly convergent posterad, posterior margin of vertex strongly rounded and short, slightly bulging posterodorsad. Frons and vertex with unremarkable, fine punctures, glossy; setae sparse and suberect, tempora and posterior margin of vertex with dense thick bristles. Antennae short and compact, AnL 0.45–0.50 mm, scape and pedicel each distinctly elongate, antennomeres 3‒8 each slightly transverse (8 indistinctly so), 9‒11 gradually increasing in width and length, 9 slightly and 10 strongly transverse, 11 indistinctly longer than 9 and 10 combined, about 1.3 × as long as broad.

Pronotum subconical, broadest distinctly behind middle; PL 0.31–0.35 mm, PW 0.29–0.35 mm. Base with two pairs of pits, outer pits indistinctly smaller than inner ones, in some specimens faint transverse groove connects inner pits, sublateral carinae indistinct. Punctures and setae on disc similar to those on frons and vertex; sides of pronotum with dense thick bristles.

Elytra together oval, broadest distinctly in front of middle; EL 0.60–0.70 mm, EW 0.45–0.50 mm, EI 1.32–1.47; humeral calli small, elongate, each mesally demarcated by short elongate impression; elytral apices separately rounded. Punctures indistinct, superficial and unremarkable; setae sparse and distinctly longer than those on pronotal disc, suberect.

Legs slender, protibiae unmodified, weakly and evenly curved, with mesal margins slightly sinuate.

Aedeagus ( Figs 87–91 ) moderately elongate, moderately strongly sclerotized, AeL 0.20 mm; median lobe in ventral view broadest in submedian region, dorsal apical plate in ventral view elongate subtriangular with rounded or indistinctly truncate apex, ventral apical plate broad and short, subtrapezoidal, two pairs of elongate projections (inner and outer) are situated between ventral and dorsal plates, outer ones conspicuously long, with rounded apices; endophallic structures symmetrical, lightly sclerotized and poorly delimited. Parameres relatively broad and short, not reaching apex of median lobe, each with 3‒5 long apical setae.

Female. Unknown or indistinguishable from similar species (see Remarks).

Distribution. Japan: southern Ryūkyū: islands Yonaguni, Iriomote and Ishigaki ( Fig. 113 ).

Etymology. The adjective bibaculatus is derived from the Latin noun baculum, a stick. The specific epithet refers to the conspicuous pair of strongly elongate rod-like projections in the subapical region of aedeagus.

Remarks. Males of this species do not have any remarkable secondary dimorphic features, and identification must be made by examination of the aedeagus. The unique pair of the elongate lateral projections of the median lobe is not known in any other members of the E. taiwanus species group. I was not able to find any external characters to distinguish E. bibaculatus from the sympatric E. cryptoiriomotensis and allopatric E. oitaensis described below. For this reason, only males are included in the type series, and females of similar body shape and length collected on the west-southernmost Japanese islands should be treated as impossible to identify by morphological features.

Externally, this species is as variable in the body length and proportions of body parts as E. taiwanus . A moderate variability in the shape of the dorsal apical plate of the aedeagus was found among studied specimens. Most specimens (independently of their origins from Yonaguni-jima, Iriomote-jima or Ishigaki-jima) have the aedeagi similar to the variant shown in Figs 87‒90 . In some, especially from Yonaguni, the apex is broader and more subtriangular, and the median lobe and the pair of subapical projections are slightly stouter (as in Fig. 91 ). However, intermediate forms were found, and it seems that all specimens belong in one species distributed on three islands.

Figures

FIGURE 113. Distribution of Euconnus bibaculatus sp. n., and E. oitaensis sp. n.

FIGURES 86‒91. Euconnus bibaculatus sp. n., male from Iriomote-jima (86‒90) and Yonaguni-jima (91). Dorsal habitus (86); aedeagus in ventral (87, 89, 91) and lateral (88, 90) views.