Meleonoma acutidens sp. nov.

(Figs 1, 23, 45)

Type material. CHINA, Xizang: Holotype ♂, Pailong Village (30.01°N, 95.00°E), Linzhi County, 2031 m, 18.VIII.2018, leg. MJ Qi, slide No. ZXJ19371 . Paratypes, Xizang: 1♀, same data as holotype, slide No. ZXJ19604; 12♂ 4♀, Tongmai Town, Bomi County, 2029 m, 12–16.VIII.2018, leg. MJ Qi, slide Nos. ZXJ18362 ♂, ZXJ18370 ♂; 1♂, Yigong Town, Bomi County, 2230–2247 m, 4–5.VIII.2017, leg. MJ Qi & XF Yang, slide No. ZXJ19374; 2♂ 1♀, Motuo, 2059 m, 8.VIII.2017, leg. MJ Qi & XF Yang, slide No. ZXJ19375 ♂; 1♂, Fangkongdong, Beibeng Town, Motuo County, 750 m, 1.VIII.2018, leg. MJ Qi, slide No. ZXJ19388; Sichuan: 1♂, Hailuogou, Luding, 1695 m, 30.VI.2016, leg. KJ Teng & XF Yang, slide No. ZXJ18361; 2♂, Fengtongzhai, Baoxing, 1723 m, 28.VII.2021, leg. S Yu et al., slide No. ZXJ20017; 1♂, Wolong, Wenchuan, 1889 m, 11.VII.2021, leg. S Yu et al., slide No. ZXJ20023 .

Diagnosis. The new species is similar to M. meyricki Lvovsky, 2015 in features of the male genitalia. It can be distinguished by the costal part of the valva widened from the base to 2/3 its length, the ventral margin of the sacculus evenly arched, and the phallus with a curved band at the distal 1/3. In M. meyricki, the costal part of the valva is widened from the base to basal 1/3, the ventral margin of the sacculus is concave near the apex, and the phallus lacks a distal band (Lvovsky 2015: 773, fig. 14). The new species is also similar to M. tenuispina sp. nov., and the differences between them can be found in the diagnosis of the latter species.

Description. Adult (Fig. 1). Forewing length 4.0–5.0 mm.

Head yellow, greyish brown on frons, tipped with dark brown on occiput. Labial palpus yellow; first and second segments with dark brown scales on outer surface, second segment dark brown at apex; third segment dark brown medially, approximately 2/3 length of second segment. Antenna yellow; scape with scattered dark brown scales; flagellum annulated with dark brown on dorsal surface.

Thorax pale yellow; tegula dark brown, pale yellow apically. Legs yellow, with exceptions on ventral surface: coxa of foreleg with sparse black scales, femur and tibia black except tibia yellow apically, tarsus black except yellow at base of basal tarsomere and at apices of basal two tarsomeres, femora of mid- and hindlegs black mixed with yellow scales, tibia of midleg black except yellow at middle and at apex, tibia of hindleg black distally, tarsus of midleg black except yellow at apices of basal two and apical one tarsomeres, tarsus of hindleg with basal four tarsomeres black except yellow at apices. Forewing elongate lanceolate, apex narrowly rounded; ground colour pale yellow, with scattered dark brown scales; costal margin with dense dark brown scales along basal 2/5, forming a diffused stripe, wider at base, with a small dot at distal 1/4 of costal margin; costal spot dark brown, situated at middle of costal margin, diffuse posteriorly; apical patch large, dark brown; tornal spot dark brown, extending to apical patch; plical spot dark brown, at middle of fold; discal and discocellular spots black, at middle and outer margin of cell, discocellular spots placed one above the other; fringe greyish black, yellow along basal line. Hindwing and fringe greyish brown.

Abdomen. Male genitalia (Fig. 23). Uncus slender, elongate clavate, pointed at apex. Gnathos weakly sclerotized laterally, just exceeding posterior margin of tegumen, inconspicuous anteriorly. Tegumen widened medially, with a large semicircular anterior emargination, laterally narrowed to obtuse anterior end. Costal part of valva narrow at base, gradually widened to 2/3 its length, thereafter narrowed to rounded apex, setose ventrodistally; ventral margin arched outward distally; costal band extending nearly to tip of costal margin; transtilla wide, rounded at apex. Sacculus wide at base, gradually narrowed to preapex, with a tiny tooth at apex, base approximately 1.5 times as wide as base of costal part; dorsal margin with two sclerotized bands: basal band from base curved downward, reaching 1/3 width of sacculus, distal band along distal 3/5 of dorsal margin; ventral margin evenly arched outward. Saccus gradually narrowed from base to rounded apex, approximately 0.5 length of uncus. Juxta circular, with a gap posteriorly. Phallus shorter than costal part of valva, with a curved band at distal 1/3.

Female genitalia (Fig. 45). Papillae anales sub-quadrate, setose.Apophyses posteriores approximately 2.5 times as long as apophyses anteriores. Eighth sternal plate spiculate; posterior margin concave at middle, lined with long setae, slightly convex on anterior margin. Ductus bursae membranous. Corpus bursae membranous, not clearly distinguished from ductus bursae, drop-shaped anteriorly; signum absent.

Distribution. China (Sichuan, Xizang).

Etymology. The specific epithet is derived from the Latin acutidens, referring to the tiny apical tooth of the sacculus.