Microscydmus (Microscydmus) kochiensis, Jałoszyński, 2019

Jałoszyński, Paweł, 2019, Unexpected diversity of Microscydmus Saulcy & Croissandeau in Japan (Coleoptera: Staphylinidae: Scydmaeninae), Zootaxa 4679 (3), pp. 539-552 : 544-545

Microscydmus (Microscydmus) kochiensis sp. n.

( Figs 4 , 12 , 20 , 28 )

Type material. Holotype: JAPAN (Kôchi Pref.): ♂, two labels: "( Kôchi : JAPAN) / Kuroson / Nishitosa-mura / 23. V. 1999 / M. Sakai leg." [white, printed]; " MICROSCYDMUS (s. str.) / kochiensis m. / P. Jałoszyński, 2019 / HOLOTYPUS " [red, printed] ( EUMJ) . Paratypes (3 exx.): 2 ♀♀, same data as for holotype, except for 21. VI. 1999 and 22-23. V. 1999, both Tatsuya Kan leg.; 1 ♀, " Kôchi : JAPAN / Ohdaba / Kuroson / 18. x. 1997 / M. Sakai (litter)" [white, printed]; all paratypes with yellow PARATYPUS labels (cPJ, EUMJ) .

Diagnosis. Body length ~ 0.8 mm; entire frons and vertex with distinct, deep, well-defined and very dense punctures; bristles on tempora and vertex short but well-visible; protibia not thickened in apical region, with apical comb of four teeth that occupy distomesal margin; aedeagus with conspicuous ovoid vesicular structure in sub-basal region of median lobe; parameres strongly recurved.

Description. Body of male ( Fig. 4 ) slender, distinctly flattened, pigmentation moderately dark brown, vestiture light brown; BL 0.81 mm.

Head ( Fig. 12 ) broadest at eyes, HL 0.15 mm, HW 0.18 mm; tempora weakly arcuate, about as long as 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 but distinct, well-marked and conspicuously dense punctures; setae sparse, short and suberect, bristles on tempora and vertex short but well-visible; long posterolateral setae on vertex not found. Antennae slen- der, AnL 0.30 mm, antennomeres I and II strongly elongate, III–X each distinctly transverse, XI about as long as broad.

Pronotum in dorsal view nearly circular, broadest in front of middle, PL 0.21 mm, PW 0.23 mm; anterior margin weakly arcuate; anterior corners not marked; sides strongly rounded; 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 similar as those on head, conspicuously dense; setae sparse, short, suberect; lateral bristles dense and relatively long, well visible.

Elytra together oval, broadest distinctly in front of middle, EL 0.45 mm, EW 0.30 mm, EI 1.50; humeral calli distinct; elytral base with large and deep basal impression; narrow adsutural region in anterior half of each elytron indistinctly impressed; apices of elytra separately rounded. Punctures dense but superficial and very small and diffuse, much less distinct than those on head and pronotum; setae short, sparse and nearly recumbent.

Protibia ( Fig. 20 ) not thickened in apical region, with apical comb of four teeth that occupy distomesal margin.

Aedeagus ( Fig. 28 ) moderately slender, AeL 0.13 mm, endophallus with long median tubular component gradually broadened in its proximal portion to form an ovoid vesicle; parameres strongly sinuate, each with one apical seta.

Female. Externally similar to male, also with thickened protibiae, but lacking apical combs; BL 0.83–0.85 mm (mean 0.83 mm); HL 0.15 mm, HW 0.19–0.20 mm (mean 0.20 mm), AnL 0.30–0.33 mm (mean 0.32 mm); PL 0.20–0.23 mm (mean 0.22 mm), PW 0.23–0.25 mm (mean 0.24 mm); EL 0.45–0.48 mm (mean 0.47 mm), EW 0.33 mm, EI 1.38–1.46.

Distribution. Japan, southern Shikoku.

Etymology. Locotypical, after Kôchi Prefecture.

Remarks. No other Far Eastern species have so distinctly and densely punctate both the head and pronotum. The male protibial comb composed of only four teeth is similarly small and occupies a similar area on the tibial apex as those in some European species (revised and illustrated by Orousset (2017)), but the aedeagi of the latter do not have the large, sub-basal vesicular structure in their endophalli, and their parameres are nearly straight or weakly curved, whereas M. kochiensis has conspicuously recurved, sinuate parameres. The shape of parameres and the sub-basal vesicular endophallic structure are similar in M. kochiensis and M. elytratus ; both species have been collected in the same area. However, despite similarities in the aedeagi, their body length is conspicuously different ( M. kochiensis is much smaller than M. elytratus ), and male secondary sexual characters differ profoundly. In M. elytratus the elytra bear a posteromedian patch of modified setae (absent in M. kochiensis ); and the protibial comb in M. elytratus is composed of six teeth, vs. only four teeth in M. kochiensis .

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).