Microlithosia laosana Bayarsaikhan & Bae, n. sp.

(Figs. 1, 4)

Type materials. Holotype: 1 ♂, Laos, Prov. Xieng Khouang, Ban Tha (N19˚43′0.70″, E103˚35′24.20″, Alt: 1204 m), 30.VI.2017 (Y.S. Bae, S.M. Na, D.J. Lee, J.H. Ko and T.K. Lee), Gen. Slide No. INU ˗1846L . Paratypes (4 ♀): Laos. 1♀, Prov. Bolikhamsai, Phou Khao Khouay NP. (N18˚30′11.37″, E102˚58′05.52″, Alt: 648 m), 9.XI.2015 (Y.S. Bae, B.S. Park, S.M. Na, J.W. Kim and D.J. Lee), Gen. Slide No. INU ˗1817L ; 1 ♂, Prov. Bolikhamsai, Phou Khao Khouay NP. (N18˚28′25.28″, E103˚05′6.11″), 1.IV.2016 (Y.S. Bae, B.S. Park, S.M. Na, J.W. Kim and D.J. Lee), Gen. Slide No. INU ˗1832L ; 1 ♂, Prov. Xieng Khouang, Ban Tha (N19˚44′50.20″, E103˚37′28.10″), 29.VI.2017 (Y.S. Bae, S.M. Na, D.J. Lee, J.H. Ko and T.K. Lee), Gen. Slide No. INU ˗1845L ; 1 ♂, Prov. Xieng Khouang, Ban Tha (N19˚44′50.20″, E103˚37′28.10″), 1.VII.2017 (Y.S. Bae, S.M. Na, D.J. Lee, J.H. Ko and T.K. Lee), Gen. Slide No. INU ˗1847L.

Diagnosis. This species is similar to members of shaowuica- species group by general appearance, which including: Microlithosia shaowuica Daniel, M. umbripuncta (de Joannis), and M. nanlingica Dubatolov, Kishida & Wang. All species of this group have the forewing with a discal and a costal dark spots, and roundly convex costal margin. However, M. laosana n. sp. is differs from members by having the slightly convex forewing costal margin, about 1/3 of apex, plus the dark discal and claviform spots, and diffused distal area (Figs. 1–3; Daniel 1954: 135).

In male genitalia, all species of shaowuica- species group have asymmetrical distal and basal saccular process and vesica with field of small spines. On its turn, M. laosana Bayarsaikhan & Bae, n. sp. presents symmetrically branched distal saccular processes and aedeagus with a bundle of slender spines and field of short spines (Figs. 4– 6; Daniel 1954: 135, Abb. 97).

Description. Adult (Fig. 1). Length of forewing 8˗10 mm. Head and thorax yellowish brown. Ground color of forewing yellow brownish, costal margin slightly convex about 1/3 of apex, a clear dark discal and a diffuse dark claviform spots; cilia pale yellowish. Hindwing white yellowish; cilia as in forewing. Abdomen pale, with yellowish tuft.

Male genitalia (Fig. 4). Uncus slender, hook-shaped, with small spine at tip, with almost same length of tegumen; cucullus tapering to apex, shark dorsal fin-shaped; distal saccular process slender, curved downwards, with two asymmetric branch, reaching apex of valvae; basal saccular process stout, finger-shaped, bearing stout setae throughout its length, and with an apical spine, left basal saccular process twice longer than right; juxta domeshaped; aedeagus short, stout, with a long medial process; vesica with a bundle of slender spines and field of short spines.

Female unknown.

Distribution. Laos (Ban Tha, Prov. Xieng Khouang; NP. Phou Khao Khouay, Prov. Bolikhamsai).

Etymology. The species is named the country of type locality (Laos).