Diduga sphaeracephalus Bayarsaikhan & Bae, n. sp.

(Figs 1a, 1b, 8a, 8b, 15)

Type materials. Holotype: 1♂, Thailand, Chantaburi, Kaosoi Dao, 14.VIII.1981 (leg. H. Kuroko, S. Moriuti, Y. Arita & Y. Yoshiyasu), Gen. Slide No. OPU˗037(INU˗10280) Thailand (Coll. OPU). Paratype. (1 ♀) Thailand: 1 ♀, same to holotype, Gen. Slide No. OPU˗028(INU˗10281) Thailand (Coll. OPU).

Diagnosis. By the wing pattern of this species, it is hardly distinguishable from many others of the genus Diduga. However, in male genitalia, membranous, rounded apex of valva with a upper angle’s spine, and aedeagus vesica with a large stout spine˗shaped and dentate plate˗shaped cornuti; in female genitalia, weakly sclerotized os- tial plate irregularly V˗shaped, and acorn˗shaped corpus bursae heavily covered with small spines wholly, and with diverse sized, strongly sclerotized spines based to strongly sclerotized two bands in thickened top of acorn˗shaped corpus bursae separates this species well from all the other known Diduga.

Description. Adult (Figs 1a, 1b). Length of forewing 5˗5.5 mm in both sexes. Head, patagium and tegula deep yellow. Thorax dark brown. Forewing ground color dark brown, with broad, deep yellow costal margin, which hind border broadly waved; with row of small, dark brown dots in costal and terminal area; cilia deep yellow. Hindwing ground color pale brown; cilia pale brown. Abdomen brown, except deep yellow ventral, with deep yellow anal tuft in male. Male genitalia (Figs 8a, 8b). Uncus waved, heavily covered with setae, apex strongly hook˗shaped, with small apical spine, almost same length with tegumen. Tegumen triangular, weakly sclerotized. Valva stout, symmetric; weakly sclerotized costal margin of valva with roundly broadened in median area, and apex of costal margin finished to a strongly sclerotized, large (1/3 length of costal margin), triangular plate, which plate with a sclerotized apical spine; apex of valva rounded, membranous, with a weakly sclerotized, small, semicircular spur in medial area of membranous apex, and heavily covered with setae. Apex of juxta broadly heart˗shaped. Saccus roundly U˗shaped. Aedeagus stout, and vesica with a large (almost same length with aedeagus), stout spine˗shaped cornutus in apical area and a band˗shaped plate covered with diverse sized spines in opposite side (near apex of aedeagus). Female genitalia (Fig 15). Papillae anales weakly covered with setae. Ostial plate weakly sclerotized, irregularly V˗shaped. Ductus bursae tubular, weakly sclerotized in first 1/3 of length, and strongly sclerotized near cervix of corpus bursae. Corpus bursae membranous, acorn˗shaped, heavily covered with small spines wholly, except top of acorn, which top thickened, with diverse sized, strongly sclerotized spines based to strongly sclerotized two bands.

Distribution. Thailand (Chantaburi and Kaosoi Dao Provinces).

Etymology. The species name is derived from the Greek sphaera (= ball) and cephala (= head), referring to the rounded apex of valva in male genitalia.