Periacma nakhonnayokensis Moriuti, Saito et Lewvanich, 1985 (Figs 13, 28) Periacma nakhonnayokensis Moriuti, Saito et Lewvanich, 1985: 28. TL: Thailand. TD: OPU, TDA. Material examined. CHINA, Yunnan: 2♂, Lvshilin, Xishuangbanna, 21, 29.V.2015, leg. ZG Zhang, slide Nos. ZXJ18211, XZX20848. Diagnosis. Periacma nakhonnayokensis can be distinguished from its congeners by the forewing with a large cloudy dark brown distal blotch, and the costa of the valva with a large triangular process at distal 1/5. Redescription. Adult (Fig. 13). Wingspan 15.0‒ 16.5 mm. Head. Vertex and frons whitish yellow. Labial palpus pale orange yellow; first segment with black scales on outer surface; second segment with black scale near apex. Antenna with scape dark brown on dorsal surface, yellow on ventral surface; flagellum yellow, ringed with black except basal 11 flagellomeres dark brown on dorsal surface. Thorax. Mesonotum yellow; tegula yellow, black at base. Forewing pale orange yellow, with yellowish brown scales; costal margin with dense black scales along basal 1/5, forming a dark band; dorsum with a black spot at base; discal and discocellular spots black; postmedial fascia dark brown, broad, from between distal 1/3 and 3/5 of costal margin to dorsum; fringe concolorous to forewing. Hindwing and fringe dark grey. Legs yellow, except three distal tarsomeres of fore- and midlegs black; on ventral surface, foreleg with coxa black; on dorsal surface, foreleg with femur and tibia black, midleg black at apex of femur, tibia black except yellow at apex, tarsus black at middle of first tarsomere and at base of second tarsomere. Male genitalia (Fig. 28). Uncus wide at base, slightly narrow and parallel from near base to basal 2/3, slightly widened from distal 1/3 to obtuse apex. Gnathos with basal arm almost uniformly banded, longer than ventral plate; ventral plate smooth, posterior half uniformly narrow, anterior half broadened, transversely produced and narrowed outward. Valva with costal part subparallel from base to approximately 3/4, slightly narrowed from distal 1/4 to rounded apex; costa straight, with a narrow triangular process at distal 1/5; dorsal-proximal process stout, setose; sacculus 1/2 length of costal part of valva, narrowed from wide base to apex. Saccus obtuse on anterior margin. Aedeagus shorter than costal part of valva, distal 2/5 being an elongate digitate process, with small denticles on ventral surface. Distribution. China (Yunnan), Thailand. Note. This species is newly recorded for the Chinese fauna.

Published as part of Wang, Shuxia & Xu, Zhixin, 2024, Taxonomy of the genus Periacma Meyrick (Lepidoptera: Autostichidae) from China, with a checklist of the world species, pp. 101-129 in Zootaxa 5399 (2) on page 115, DOI: 10.11646/zootaxa.5399.2.1, http://zenodo.org/record/10493947