Periacma falcata Wang, sp. nov.

(Figs 3, 20)

Type material. CHINA, Yunnan: Holotype ♂, Qinlangdang (27º69′N, 98º27′E), Mt. Gaoligong, Nujiang, 380 m, 28.V.2017, leg. KJ Teng et al., slide No. XZX20831. Paratype: 1♂, same data as holotype.

Diagnosis. The new species is similar to P. rectignatha Wang et Li, 2006 in male genitalia. It can be distinguished by the costal part of the valva more dilated before the apex, the apex of the sacculus obliquely truncate and the aedeagus with distal 1/4 produced to a sub-rectangular plate. In P. rectignatha, the costal part of the valva is not dilated before the apex, the apex of the sacculus is narrowly rounded, and the aedeagus is produced to a sub-digitate process distally.

Description. Adult (Fig. 3). Wingspan 14.5 mm.

Head. Vertex and frons yellow, mottled with black scales. Labial palpus yellow, basal segment black on outer surface, second segment widely ringed with black scales before apex. Antenna with scape black on dorsal surface, yellow on ventral surface; flagellum yellow, annulated with black on dorsal surface.

Thorax. Mesonotum black, except yellow at proximal base; tegula yellow, with a black spot at base. Forewing yellow, with black scales; costal margin black at base; dorsum with a black speckle at base, diffused obliquely outward to basal 1/3 of cell; discal and plical spots black, small; postmedial fascia black, from beyond middle of costal margin oblique outward to tornus; apical fascia black, diffused, narrowed and approaching postmedial fascia; terminal dots black, evenly spaced along termen; fringe concolorous to forewing. Hindwing grey; fringe grey except yellow at base. Legs yellow, except four distal tarsomeres of foreleg and tarsomeres 3 4 of midleg black; on ventral surface, coxa of foreleg with an elongate black stripe; on dorsal surface, foreleg with black scales on femur, tibia black on basal half, tarsus black at middle of first tarsomere, midleg with a few black scales on femur, tibia black at base and anuulated with black on distal half, tarsus black at middle of first tarsomere and at base of second tarsomere; on outer surface, tibia of hindleg black at base, with black scales on distal half, tarsus black at middle of first tarsomere, tarsomeres 2-3 with a few greyish black scales.

Male genitalia (Fig. 20). Uncus slightly narrowed to before apex, laterally setose, apex folded, slightly extending outward laterally. Gnathos with basal arm shorter than ventral plate; ventral plate sub-rectangular, wider than long. Valva with basal half of costal part narrow and parallel sided, distal half slightly wider and subparallel to before rounded apex, densely setose; costa concave medially; dorso-proximal process clubbed, slightly dilated distally, with long setae; sacculus about half length of costal part of valva, gradually narrowed from base to middle length, distal half unifromly narrow to before obliquely truncate apex, curved ventrad like a sickle. Saccus short, rounded anteriorly, triangularly produced posteriorly. Aedeagus longer than 3/4 length of costal part of valva, widened to basal 3/7, then uniform to 6/7, distal 1/7 produced to sub-rectangular plate widened apically, with three distal processes: two short spine-shaped processes arising from beyond distal 1/4 laterally, one spatulate process arising from distal 1/3, reaching before apex.

Female unknown.

Distribution. China (Yunnan).

Etymology. The specific epithet is derived from the Latin falcatus, referring to the shape of the distal half of the sacculus.