(Figs. 1–4, 9, 11, 13, 15, 17–22)

Type materials. Holotype. ♂: CHINA: Guangxi Prov., Baise Shi, Tianlin Xian, Cenwanglaoshan, 1300 m, 2– 3.IV.2016, reared from Lithocarpus corneus (HSU 16 D8), emgd. 27. IV.2017 (IOZ).

Paratypes. 5♂♂ 3♀♀, same locality and date as for holotype, reared from Lithocarpus corneus (HSU 16 D8), emgd. 23–27.IV.2016 (3 dissected, genitalia YFH 1122, 1158, 1159) (IOZ, NTNU); 2♂♂ 4♀♀, same locality as holotype, 6–7. IV.2017, reared from Lithocarpus corneus (HSU 17D2), emgd. 30.IV.–1.V.2017 (NTNU). 1♀: VIETNAM: Ha Giang Prov., Meo Vac, 1250 m, 22.V.2014.

Description. Male (Figs. 1–2): FL 16.2–19.6 mm (mean, 18.2 ± 1.4 mm, n = 8); AL 7.2–8.7 mm (mean, 8.1 ± 0.5 mm, n = 8). Head: Hairy, vertex, frons dark brown but sparsely bearing white hairs mesad; a narrow white rim surrounding eye; eye semi-oval, densely covered with long, buff setae; labial palpus porrect, with 3rd segment pointed downwards, covered with dark brown scaling mottled with white laterally; maxillary palpus reduced, inconspicuous; proboscis unscaled; antenna smooth scaled, naked at terminal end of nudum. Thorax: Dark brown dorsad, white ventrad; legs with tarsus of fore leg stubby; white, mottled with brown. Forewing: Termen, costa slightly concave, dorsum straight. Ground color of upperside dark brown, overlaid with large area of metallic green tinged with yellow scaling proximally, covering most of forewing, leaving merely a narrow dark brown margin. Fringe white, prominent. Ground color of underside buff gray. Discal spot forming brown bar edged with white. Distal band of central symmetry system represented as tilted white line edged with brown proximally, strongly dislocated inwards in cell Cu2. Submarginal band and "g"-element (per Nijhout 1991) fused into prominent, dark brown band edged with white, attenuate towards apex. Fringe white, prominent. Hindwing: Contour of wing slightly produced at distal end of M1 and Cu1; Cu2 bearing long, tail-like projection. Metallic scaling on upperside less extensive than that of forewing, with dark brown areas including a patch along costa, narrow bands along termen and dorsum. Narrow, metallic blue line at distal ends of cells along termen. Ground color of underside buff. Discal spot forming brown bar edged with white. Distal band of central symmetry system forming prominent white line edged with dark brown proximally, forming straight line from dorsum to vein Cu1, running outwards in cell Cu1, dislocated proximally as tick-shaped or a straight line in cell Cu2, retracing into straight line in cell 2A, and becoming a slightly curved line in cell 1A. Submarginal band consisting of faint, broad, white band, a black, oval spot enclosed within orange circle in cell Cu1, and a tornal orange patch edged by black and metallic blue scaling anteriorly and posteriorly; "g"-element consisting of a string of arch-like, faint white markings. Fringe white, prominent. Abdomen: Dark brown dorsad, white ventrad. Genitalia (Figs. 9, 11, 13): Ring-shaped sclerites of 9+10 segments with posterior end nearly straight, a transverse notch present anteriorly; saccus flap-like, shallowly depressed; brachium abruptly bent over, forming elongate arm with distal end up-curved; elbow bearing a prominent, simple spine with pointed end; valva pincer-like, bearing two distal, flatten processes, with dorsal one (ampulla) longer, stout basally, twisted half-way, with distal portion thin, dagger-like, pointing meso-posteriad; ventral one (harpe) with distal end pointed, shorter, flattened, slightly up-curved. Phallus elongate, nearly straight with truncated caudal end; aedeagus approximately 1.77x phallobase in length, cornuti present, forming a cluster of small spinules at caudal end. Juxta broad, pincer-like with deep dorsal notch.

Female (Figs. 3–4). FL 16.0– 19.3 mm (mean, 18.2 ± 1.1 mm, n = 8); AL 7.5–8.7 mm (mean, 8.3 ± 0.4 mm, n = 8). Body, wing patterns of underside as described for male except scaling lacking gray tone. Fore leg with tarsus segmented. Wing upperside uniformly brown with prominent, proximal, metallic, pale blue patch on forewing. Metallic blue line at distal ends of cells along termen more prominent than that of male. Genitalia (Fig. 15): Apophyses posteriores elongate, slender, curved, abruptly enlarged, flattened basad. Sterigma with lamella antevaginallis heavily sclerotized, rench-like with prominent, trident, medial cleft; lamella postvaginalis forming moderately sclerotized wall with transverse wrinkles. Posterior half of ductus bursae tubular, weakly sclerotized; anterior half enlarged, pouch-like, membranous. Corpus bursae rounded, bearing a pair of small, discal, signa with invaginated blade. Papillae anales lobe-like, setose.

Immatures. Ova (Fig. 18) approximately 0.73 ± 0.02 mm in diameter, 0.44 ± 0.01 mm in height (n = 8), spherical but compressed, white, surface with fine sculpture forming framework with short stub-like processes. Larvae (Figs. 19–20) with four instars. Head dark brown, glossy. Body slug-like, of typically lycaenid form, with A8 produced laterally in final instar; surface bearing transparent setae. Coloration of body olive-green in younger instars, becoming dark green to brown when full-grown. White chevrons edged by brown subdorsally. A dark, medial, longitudinal line dorsally, abruptly broaden cephalically. T1 shield diamond-shaped. Anal lobe somewhat square. Spiracles dark brown. Full-grown larva 17.0 mm in length (n = 5). Pupae (Fig. 21–22): 11.55 ± 0.49 mm in length, 4.48 ± 0.20 mm in width of T2, 5.52 ± 0.18 mm in width of A3, 4.90 ± 0.23 mm in height of A3 (n = 5); of typical lycaenid form, brown tinged with yellow, mottled with dark brown dorsally, a dark brown medial line present dorsad on abdomen; wings with extensive dark brown markings; spiracles cream white.

Diagnosis. The general morphology of the genitalia (Figs 9, 11, 13, 15) in C. laoshanensis conforms with all congeners, including a straight phallus, cornuti as minute spinules, ductus bursae tubular, sclerotized caudally and pouch-like, membranous cephalically (Shirozu & Yamamoto, 1956). However, C. laoshanensis possesses a few peculiar features not seen in other Chrysozephyrus species, including pincer-shaped valva and elbow position of the brachium forming a simple spine. The valvae of all other Chrysozephyrus species have the harpe only weakly represented, thus not pincer-like in shape; elbow position of brachium is serrate, bearing small spines in other Chrysozephyrus species.

In terms of wing patterns, C. laoshanensis is most similar to the sympatric, Lyonia -associated C. watsoni (Figs. 5–8). They may be separated using the following diagnostic characteristics: The distal band of central symmetry system on the hindwing underside forms a tick-shaped or straight white line in laoshanensis, whereas it forms a broken line in watsoni. The distal band of central symmetry system on the forewing of the male is prominent in laoshanensis, whereas it is obsolete or barely recognizable in watsoni. Dark brown margin on the forewing upperside of the male is narrow, nearly equal in width throughout the length in laoshanensis, whereas it is thicker, broaden anteriorly, forming a prominent dark area at the apex in watsoni. In laoshanensis, the metallic blue scaling on the wing upperside of the female is only found on forewing and pale blue in color; no orange spot is present on the forewing. By contrast, in watsoni, it is blue or purple, sometimes also found on the hindwing, and additional orange spots sometimes are found on the forewing. The brachium possesses a prominent spine at elbow in laoshanensis (Fig. 9), but a conical process with serrate end in watsoni (Fig. 10). The aedeagus is longer than the phallobase in laoshanensis (Fig. 11), but nearly equal in length in watsoni (Fig. 12). The valva is pincer-like with two elongate processes with acute distal end in laoshanensis (Fig. 13), but lobe-like with only a digitate, inwardpointing process in watsoni (Fig. 14). The lamella antevaginallis broad, rench-like with a trident medial cleft in laoshanensis (Fig. 15), whereas it is narrow, bump-like with shallow medial cleft in watsoni (Fig. 16).

Host plant. Lithocarpus corneus var. angustifolius (Fig. 17) in nature.

Bionomics. Univoltine, overwintering as an ovum, which is singly attached on the underside of twigs. Ovum hatch by late March in the type locality. Larva fed on only soft foliage. Adults emerged by late April to early May under laboratory conditions. Eggs were present by early July, laid singly on small twigs of the host plant in shady positions approximately 1–4 m above the ground.

Distribution. China (Guangxi) and northern Vietnam (Ha Giang) for the present.

Etymology. The specific name refers to the abbreviation of the name of the type locality.