Microscydmus (Microscydmus) tibialis, Jałoszyński, 2019

Jałoszyński, Paweł, 2019, Unexpected diversity of Microscydmus Saulcy & Croissandeau in Japan (Coleoptera: Staphylinidae: Scydmaeninae), Zootaxa 4679 (3), pp. 539-552 : 546-547

Microscydmus (Microscydmus) tibialis sp. n.

( Figs 6 , 14 , 22 , 30 )

Type material. Holotype: JAPAN (Kôchi Pref.): ♂, two labels: "( Kôchi : JAPAN) / Kuroson / Nishitosa-mura / 21. VI. 1999 / M. Sakai leg." [white, printed]; " MICROSCYDMUS (s. str.) / tibialis m. / P. Jałoszyński, 2019 / HOLOTYPUS " [red, printed] ( EUMJ).

Diagnosis. Body length ~ 0.7 mm; frons and vertex with very fine, inconspicuous punctures; bristles on tempora and vertex short and sparse; protibia not thickened distad, with apical portion tapered, apical comb of nine teeth occupies apical tibial margin, teeth directed toward base of tibia; aedeagus with symmetrical, lightly sclerotized endophallus that contains two pairs of small dark droplet-like structures in sub-basal region; parameres nearly straight.

Description. Body of male ( Fig. 6 ) slender, slightly flattened, pigmentation moderately dark brown, vestiture light brown; BL 0.69 mm.

Head ( Fig. 14 ) broadest at eyes, HL 0.11 mm, HW 0.15 mm; tempora weakly arcuate, about as long as 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 uniformly and evenly covered with fine, inconspicuus punctures; setae sparse, short and suberect, bristles on tempora and vertex distinct; long posterolateral setae on vertex not found. Antennae slender, AnL 0.29 mm, antennomeres I and II strongly elongate, III–X each transverse, XI about as long as broad.

Pronotum in dorsal view nearly circular, broadest distinctly in front of middle, PL 0.20 mm, PW 0.20 mm; anterior margin weakly arcuate; anterior corners not marked; sides strongly rounded; posterior pronotal corners distinct, obtuse-angled; posterior margin nearly straight; pronotal base with an indistinct, short and shallow transverse groove, lateral pits not discernible. Punctures on disc fine, inconspicuous; setae sparse, short, suberect; lateral bristles sparse and moderately long.

Elytra together oval, broadest slightly in front of middle, EL 0.38 mm, EW 0.25 mm, EI 1.50; humeral calli distinct; elytral base with large and deep basal impression; adsutural area indistinctly impressed in anterior half; apices of elytra separately rounded. Punctures on elytra as fine as those on head and pronotum; setae short, sparse and nearly recumbent.

Protibia ( Fig. 22 ) not thickened distad, with apical portion tapered, apical comb of nine teeth occupies apical tibial margin, teeth directed toward base of tibia.

Aedeagus ( Fig. 30 ) slender, AeL 0.13 mm, endophallus lightly sclerotized, with an elongate cup-shaped median component containing two pairs of darkly sclerotized, small droplet-shaped structures; parameres nearly straight, each with one apical seta.

Female. Unknown.

Distribution. Japan, southern Shikoku.

Etymology. The adjective tibialis refers to the unusually shaped protibial modification in males.

Remarks. This species has the smallest adults of all Japanese Microscydmus ; only M. oharaensis has a comparable body length. The aedeagus of M. tibialis has uniquely shaped endophallic structures, with four small sclerotized 'spots' between base and middle; also the protibial comb composed of nine teeth directed toward base of tibia is unusual.

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).