Microscydmus (Microscydmus) okinawanus, Jałoszyński, 2019

Jałoszyński, Paweł, 2019, Unexpected diversity of Microscydmus Saulcy & Croissandeau in Japan (Coleoptera: Staphylinidae: Scydmaeninae), Zootaxa 4679 (3), pp. 539-552 : 540-541

Microscydmus (Microscydmus) okinawanus sp. n.

( Figs 1 , 9 , 17 , 25 )

Type material. Holotype: JAPAN (Okinawa Pref.): ♂, two labels: " JAPAN, OKINAWA Pref. / OKINAWA Is. FIT / OKINAWASHI, 6-9 IX 2003 / CHIBANAGUSUKU-ATO / S. & K. Arai leg." [white, printed]; " MICROSCYD- MUS (s. str.) / okinawanus m. / P. Jałoszyński, 2019 / HOLOTYPUS " [red, printed] ( NSMT).

Diagnosis. Body length ~ 0.9 mm; posteromedian portion of vertex with punctures larger and denser than those on surrounding areas; bristles on tempora and vertex short and sparse, barely discernible; protibia strongly thickened in apical region, with apical comb of ten robust spines that extend from apical onto mesal margin of tibia, the most proximal spine longer and of different shape than the penultimate one; aedeagus with a pair of subapical arcuate structures connected at middle and with strongly elongate lateral components flanking a long tubular structure; parameres nearly straight.

Description. Body of male ( Fig. 1 ) slender, slightly flattened, pigmentation brown, vestiture light brown; BL 0.88 mm.

Head ( Fig. 9 ) broadest at eyes, HL 0.18 mm, HW 0.20 mm; tempora weakly arcuate, slightly longer than eyes; posterior margin of vertex straight, vertex and frons confluent and convex; supraantennal tubercles weakly elevated but well-defined; eyes large, strongly convex and coarsely faceted. Frons and vertex covered with small and shallow but dense and distinct punctures, which on posteromesal portion of vertex are distinctly larger than those on surrounding areas; setae sparse, short and suberect, bristles on tempora and vertex short and sparse; vertex with a pair of long posterolateral setae. Antennae slender, AnL 0.35 mm, antennomeres I and II strongly elongate, III–X each transverse, XI about as long as broad.

Pronotum in dorsal view nearly circular, broadest at middle, PL 0.23 mm, PW 0.23 mm; anterior and posterior margins weakly arcuate, sides strongly rounded, anterior and posterior pronotal corners indistinct, obtuse-angled; pronotal base with a well-defined, short transverse groove, additionally with one tiny pit near each hind corner. Punctures on disc fine and inconspicuous, smaller and shallower than those on head; setae sparse, short, suberect; lateral bristles short and sparse.

Elytra together oval, broadest slightly in front of middle, EL 0.48 mm, EW 0.33 mm, EI 1.46; humeral calli distinct; elytral base with large and deep basal impression; narrow adsutural region in anterior half of each elytron slightly impressed; apices of elytra separately rounded. Punctures about as indistinct as those on pronotum; setae short, sparse and nearly recumbent.

Protibia ( Fig. 17 ) strongly thickened in apical region, broadest at apex, with apical comb composed of ten robust teeth that occupy apical margin and extend onto mesal margin, the most basal spine strongly differs in length and shape from the penultimate one.

Aedeagus ( Fig. 25 ) relatively stout, AeL 0.14 mm, endophallus with long median tubular component flanked by a pair of shorter elongate and nearly symmetrical sclerites in submedian region of median lobe, in subapical region the tubular component connected to a pair of long, arcuate, transverse sclerites; parameres nearly straight, each with one apical seta.

Female. Unknown.

Distribution. Japan, Okinawa-jima.

Etymology. Locotypical, after Okinawa Island and Prefecture.

Remarks. Among Japanese species, M. okinawanus is most similar to M. nishimeanus sp. n. described below. They share the protibiae strongly and abruptly thickened in distal region (either not thickened or thickened gradually, not abruptly, in all remaining Far Eastern Microscydmus ); they also have a similar general body form, relatively indistinct punctures on the pronotum and elytra, but distinct on the vertex, short and sparse bristles on the tempora and vertex, and similar endophallic structures. The apical protibial comb in M. okinawanus is composed of 10 robust teeth that occupy not only the apical margin, but extend onto the mesal margin, and the most basal spine or tooth of the comb strongly differs in length and shape from the penultimate one. In M. nishimeanus , the comb is composed of only six teeth that do not extend onto the mesal tibial margin, and the most basal tooth is inconspicuous, of the same shape and length as the penultimate one. Microscydmus okinawanus is also distinctly smaller than M. nishimeanus .

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).