Microscydmus (Microscydmus) elytratus, Jałoszyński, 2019

Jałoszyński, Paweł, 2019, Unexpected diversity of Microscydmus Saulcy & Croissandeau in Japan (Coleoptera: Staphylinidae: Scydmaeninae), Zootaxa 4679 (3), pp. 539-552 : 545-546

Microscydmus (Microscydmus) elytratus sp. n.

( Figs 5 , 13 , 21 , 29 )

Type material. Holotype: JAPAN (Kôchi Pref.): ♂, two labels: "(Kôchi: JAPAN) / Kuroson / Nishitosa-Village / 22-23. V. 1999 / Tatsuya Kan leg." [white, printed]; " MICROSCYDMUS (s. str.) / elytratus m. / P. Jałoszyński, 2019 / HOLOTYPUS " [red, printed] ( EUMJ) . Paratypes (3 exx.): 3 ♀♀, same data as for holotype, except for 21. VI . 1999; all paratypes with yellow PARATYPUS labels (cPJ, EUMJ) .

Diagnosis. Body length ~ 1.1 mm; entire frons and vertex with distinct but shallow and diffuse dense punctures; bristles on tempora and vertex moderately long and dense, well-visible; protibia gradually thickened distad, with apical comb of six teeth that occupy distomesal margin; elytra between middle and posterior third with an oval circumsutural patch of long and dense setae directed toward suture; aedeagus with conspicuous spherical vesicular structure in sub-basal region of median lobe; parameres strongly recurved.

Description. Body of male ( Fig. 5 ) moderately slender, slightly flattened, pigmentation moderately dark brown, vestiture light brown; BL 1.10–1.13 mm (mean 1.11 mm).

Head ( Fig. 13 ) broadest at eyes, HL 0.23 mm, HW 0.25 mm; tempora weakly arcuate, slightly longer than eyes; posterior margin of vertex nearly straight, vertex and frons confluent and convex; supraantennal tubercles weakly elevated but well-defined; eyes large, strongly convex and coarsely faceted. Frons and vertex uniformly and evenly covered with small and dense but shallow and diffuse punctures; setae sparse, short and suberect, bristles on tempora and vertex relatively short but well-visible; vertex with a pair of long posterolateral setae. Antennae slender, AnL 0.49–0.50 mm (mean 0.49 mm), antennomeres I and II strongly elongate, III indistinctly transverse, IV–VI each about as long as broad, VII–X each transverse, XI about as long as broad.

Pronotum in dorsal view nearly circular, broadest slightly in front of middle, PL 0.26–0.28 mm (mean 0.27 mm), PW 0.33 mm; anterior and posterior margins weakly arcuate; anterior corners not marked; sides strongly rounded in anterior half, in posterior half slightly sinuate; posterior pronotal corners distinct, obtuse-angled; pronotal base with a well-defined, short transverse groove deepened at each end, lateral pit near each hind corner present, but barely discernible, very small and obscured by dense punctures. Punctures on disc conspicuously dense, slightly larger than those on head, but very shallow and with diffuse margins; setae sparse, short, suberect; lateral bristles dense and relatively long, well visible.

Elytra together oval, broadest distinctly in front of middle, EL 0.60–0.63 mm (mean 0.62 mm), EW 0.43–0.45 mm (mean 0.44 mm), EI 1.39–1.41; humeral calli distinct; elytral base with large and deep basal impression; adsutural area not impressed in anterior half; apices of elytra separately rounded; small oval circumsutural region between middle and posterior half slightly impressed and surrounded by dense, long setae directed toward suture. Surface of elytra finely shagreened, individual punctures not discernible; setae short, sparse and nearly recumbent.

Protibia ( Fig. 21 ) gradually thickened distad, with apical comb of six teeth that occupy distomesal margin.

Aedeagus ( Fig. 29 ) moderately slender, AeL 0.18 mm, endophallus with long median tubular component abruptly broadened in its proximal portion to form a spherical vesicle; parameres strongly sinuate, each with one apical seta.

Female. Externally similar to male, with weakly thickened protibiae lacking apical combs, and elytra lacking posteromesal patch of modified setae; BL 1.10 mm; HL 0.23 mm, HW 0.25 mm, AnL 0.40 mm; PL 0.28 mm, PW 0.30 mm; EL 0.60 mm, EW 0.43 mm, EI 1.41.

Distribution. Japan, southern Shikoku.

Etymology. The adjective elytratus refers to the modified elytra in males.

Remarks. This is a giant among Japanese species of Microscydmus , the only one with adults distinctly exceeding 1 mm in length. The elytral patch of modified setae is unique among Palaearctic species of this genus. Similarities and differences in relation to M. kochiensis , a species with the most similar aedeagus, were discussed in remarks for the latter species.

Figures

FIGURES 1–8. Dorsal habitus of males. Microscydmus okinawanus sp. n. (1); M. oharaensis sp. n. (2); M. nishimeanus sp. n. (3); M. kochiensis sp. n. (4); M. elytratus sp. n. (5); M. tibialis sp. n. (6); M. yusuharanus sp. n. (7); M. omogonus sp. n. (8).

FIGURES 9–16. Heads of males in anterodorsal view. Microscydmus okinawanus sp. n. (9); M. oharaensis sp. n. (10); M. nishimeanus sp. n. (11); M. kochiensis sp. n. (12); M. elytratus sp. n. (13); M. tibialis sp. n. (14); M. yusuharanus sp. n. (15); M. omogonus sp. n. (16). Arrowheads show posterolateral vertexal setae.

FIGURES 17–24. Apices of male protibia in dorsal (17–21, 22–24) and ventral (22) views. Microscydmus okinawanus sp. n. (17); M. oharaensis sp. n. (18); M. nishimeanus sp. n. (19); M. kochiensis sp. n. (20); M. elytratus sp. n. (21); M. tibialis sp. n. (22); M. yusuharanus sp. n. (23); M. omogonus sp. n. (24).

FIGURES 25–32. Aedeagus in ventral view. Microscydmus okinawanus sp. n. (25); M. oharaensis sp. n. (26); M. nishimeanus sp. n. (27); M. kochiensis sp. n. (28); M. elytratus sp. n. (29); M. tibialis sp. n. (30); M. yusuharanus sp. n. (31); M. omogonus sp. n. (32).