Nogunius sagaensis, Jałoszyński & Nomura, 2021

Jałoszyński, Paweł & Nomura, Shûhei, 2021, A new species of Nogunius Jałoszyński in Japan (Coleoptera: Staphylinidae Scydmaeninae), Zootaxa 5071 (2), pp. 283-288 : 284-287

Nogunius sagaensis sp. n.

( Figs 1–5 , 6 , 11 )

Type material. Holotype: JAPAN (Saga Pref.): ♂, two labels: “FIT(FG-6)x3: Mt. Kashiwa- / dake (237m), Asahimachi / Takeo-shi, Saga Pref. / [ Kyushu , JAPAN] / 33.211448N, 130.018450E / 3-9.vi.2021, S.Nomura leg.” [white, printed], “ NOGUNIUS / sagaensis Jałoszyński & Nomura / HOLOTYPUS, P. JAŁOSZYŃSKI, 2021” [red, printed] ( NSMT).

Diagnosis. Eyes in male large and strongly convex but in dorsal view much shorter than tempora; aedeagus in ventral view about three times as long as broad, with narrow median subtrapezoidal apical projection.

Description. Body of male ( Fig. 1 ) moderately slender, strongly convex, light brown with appendages slightly lighter than head, thorax and elytra, setae yellowish-brown; BL 0.81 mm.

Head ( Fig. 6 ) broadest at eyes, HL 0.16 mm, HW 0.15 mm; tempora in dorsal view much longer than eyes; vertex and frons confluent, together weakly convex; each eye large, strongly convex, in lateral view bean-shaped, with distinct posteromedian emargination, composed of 25 large facets of equal diameters. Punctures on vertex fine, inconspicuous; setae short, sparse and suberect; tempora and posterior margin of vertex densely covered with thick and long bristles. Antennae slender, AnL 0.33 mm, antennomeres 1 and 2 each strongly elongate, 3–8 each about as long as broad or indistinctly transverse, 9 distinctly larger than 8 and slightly transverse, 10 much longer and especially broader than 9, strongly transverse, 11 indistinctly narrower and slightly longer than 10, about as long as broad.

Pronotum subconical with weakly rounded sides, broadest shortly in front of base; PL 0.23 mm, PW 0.18 mm. Anterior and posterior margins weakly convex, base with two pairs of small, distinct pits. Punctures on pronotal disc fine, inconspicuous; setae sparse, short, suberect; sides, especially posteriorly, with sparse, thick bristles.

Elytra together oval, broadest indistinctly in front of middle; EL 0.43 mm, EW 0.31 mm, EI 1.38; humeral calli weakly elevated, basal impressions large, deep, nearly circular; apices separately rounded. Punctures inconspicuous; setae slightly longer and denser than those on pronotum, suberect.

Legs moderately long and slender, unmodified.

Hind wings long, functional.

Aedeagus ( Figs 2–5 ) elongate, in ventral view about three times as long as broad; AeL 0.10 mm; median lobe in ventral view broadest in sub-basal region, with nearly straight sides feebly converging toward truncate apex, median apical projection present, short and subtrapezoidal, with truncate distal margin; in lateral view median lobe strongly curved in proximal third; parameres slender, in lateral view curved, each with one long apical and one long subapical seta.

Female. Unknown.

Distribution. NW Kyushu ( Fig. 11 ).

Etymology. The adjective sagaensis is topotypical, after Saga Prefecture, north-western region of the mainland of Kyushu.

Remarks. Species of Nogunius are morphologically uniform and it is difficult to identify them by external characters. Males, however, clearly differ in the relative size of eyes ( Figs 6–10 ) and a number of ommatidia. Males of Nogunius sagaensis ( Fig. 6 ) have the most convex, most laterally projecting eyes, which are nevertheless much shorter than tempora; each composed of 25 ommatidia. Males of N. sokani ( Fig. 7 ) have the largest eyes of all species, in dorsal view indistinctly longer than tempora; each eye composed of 24 ommatidia. Males of N. aogashimanus ( Fig. 8 ) also have conspicuously large eyes, larger than those in N. sagaensis and slightly shorter than tempora in dorsal view; each eye is composed of 27 ommatidia. Two remaining species, N. kerri ( Fig. 9 ) and N. fukuuzanus ( Fig. 10 ) have strikingly small eyes, only half as long as tempora in dorsal view. Those of N. kerri are composed of only 13, and in N. fukuuzanus of 19 ommatidia. The aedeagi of Nogunius are also relatively uniform ( Fig. 11 ), except for that of N. fukuuzanus , which is conspicuously elongate and slender, unlike much stouter copulatory organs of all its congeners ( Fig. 11 ). The aedeagus of N. sagaensis is most similar to that of N. aogashimanus that occurs on the geographically remote and isolated Izu Islands, over 250 km off the southern coast of Honshu and ~ 900 km east of the collecting site of N. sagaensis . Besides the cephalic and genital characters, proportions of body parts can also help identifying at least some species; useful ratios are compiled in Table 1 .

The holotype male of N. sagaensis has been collected by a flight intercept trap ( Fig. 12 ) set in evergreen forest near the top of Mt. Kashiwadake. This type of FIT was described in Nomura & Idris (2004), and is made of 0.1 mmthin transparent plastic sheet, with a pentagonal barrier, and the receiver filled with water with a spoonful of sorbic acid for preservation.

Figures

FIGURE 11. Distribution of Nogunius species, with comparison of aedeagi.

FIGURE 12. Collection site of Nogunius sagaensis sp. n. on Mt. Kashiwadake.

FIGURES 1–5. Nogunius sagaensis sp. n. Dorsal habitus of holotype male (1), and aedeagus in ventral (2, 4) and lateral (3, 5) views.

FIGURES 6–10. Comparison of key cephalic characters of males of all nominal Nogunius species. Nogunius sagaensis sp. n. (6; HW 0.15 mm); N. sokani (7; HW 0.18 mm); N. aogashimanus (8; HW 0.18 mm); N. kerri (9; HW 0.16 mm); and N. fukuuzanus (10; HW 0.15 mm).