Yukikoa mashimai Nakamura sp. nov.

Japanese name: Sumondake-shiributo-jôkai

(Figs. 1, 3a–d, 5, 6)

Type material. Holotype, male (KURA, JI 186436), “ JAPAN: Honshû / Niigata-ken, Sanjô-shi / Osoba, Sumon-dake, Ô-take/37˚ 24' 35.45" N 139˚ 07' 24.59" E/alt. 1429m, 11-VI-2022 / Gô Mashima leg./ΞẽffiñḆṪÑƃkƃ, 真 嶋Dz”·

Description (holotype). Male. Body small and wide. BL 10.3 mm. Dorsal surface almost reddish brown, mandibles, and maxillary palpi, and antennae blackish brown, legs reddish brown in middle and hind tibia and blackish brown in other parts, ventral surface and labial palpi almost blackish brown though vaguely reddish brown on middle area of each abdominal segment. Body closely covered with brown pubescence, which is shorter on antennomeres 3–11.

Head slightly shorter than width, dorsum depressed between antennal sockets; eyes small, globular and prominent, interocular distance 3.13 times as wide as the diameter of an eye; mandible arcuate and pointed at apex; apical segments of labial and maxillary palpomere triangular; antennae reaching 3/5 of elytra, filiform but weakly serrate in basal three segments, comparative lengths of antennomeres as follows: 2.05: 1.00: 1.36: 2.11: 2.19: 2.19: 2.17: 2.10: 1.90: 1.78: 2.19.

Pronotum transverse trapezoidal, widest at posterior angles, PW/HW 1.59, PW/PL 1.78, anterior margin weakly emarginate, posterior margin gently protruding in lateral halves and emarginate in the middle, lateral margins slightly wavy, all angles obtuse and rounded, disc almost flat though provided with convex areas along the anterior margin and along median line only at posterior half of pronotum with a medio-longitudinal furrow not reaching the anterior and posterior margins. Scutellum triangular with blunt apex. Elytra short and wide, almost parallel in the basal 1/6, then greatly dilated posteriad with the broadest point at posterior 3/10, apex normally rounded, HEW/PW 1.09, MEW/PW 1.57, EL/HEW 2.24, EL/MEW 1.56. Legs slender, each femur mostly straight, each tibia mostly straight though feebly arcuate in basal part.

Genitalia elongate; each ventral process of paramere moderately slender, broad at apical portion and forming a hook with pointed tip towards inner-ventral side; dorsal plate of paramere with apical margin weakly arcuate and shallowly emarginate at the middle, lateral sides weakly narrowed anteriorly, ventral surface provided with a transverse protuberance at the middle of each side with each lateral tip slightly exceeding over the lateral edges of dorsal plate; each laterophyse slender and almost parallel with rounded apex in ventral and dorsal view, stout and curved in lateral view, with the tip towards the protuberance on the ventral side of dorsal plate, the apex slightly exceeding the ventral process and the protuberance on the ventral side of dorsal plate.

Female. unknown.

Differential diagnosis. Yukikoa mashimai sp. nov. resembles Y. maniwana Okushima et Takahashi, 2010 from Okayama Pref. in general appearance. Still, they can be distinguished by the characteristics of male genitalia (see details in the key).

Distribution. Japan (Honshu, Niigata Pref., Mt. Sumondake-Ôtake (= Sumon-ôtake)).

Collecting circumstance. According to the collector, the holotype was collected when it was blown up to the top of the mountain, fell onto the snow cornice, and was cooled and unable to move (Fig. 5).

Etymology. The specific name is in honor of Mr. Gô Mashima, who discovered this new species.