Mercedula fuscomarginata Ponomarenko & M. Omelko, sp. nov.

(Figs 1–5, 10, 12–21)

Type material. Holotype: ♂, Borneo, East Malaysia, state of Sabah, 9 km NNW of Keningau, 23.iii 2018 (leg. M. Omelko), GS 355 MP, FSCB.

Paratypes: 1 ♂, 1 ♀, same locality, date and collector, 354 (♂), 359 (♀) MP; 1 ♂, 24 km north of Tawau, 19.viii 2019 (leg. M. Omelko), GS 353 MP, FSCB.

Additional material. 1 ♀, Indonesia, North Sumatra, Bukit Lawang village, 19.ii 2023 (leg. M. Omelko), GS 356 MP; 1 ♀, same locality and collector, 18.ii 2023, GS 358 MP; FSCB.

Diagnosis. New species is very similar in appearance to M. storozhenkoi sp. nov. described below. It can be distinguished by the relatively smaller size of moth, head with two tufts of elongated scales, each of which is placed on sides of frons, and forewing with costal stripe not reaching the level of cell end (Fig. 10). The new species also differs by female genitalia with large funnel-shaped antrum, antevaginal plate setaceous and with lateral drop-like lobes, small band-like postvaginal plate without honeycomb-like structure on surface and relatively small thorn-shaped signa (Figs 15, 16).

Description. Adult (Figs 1–5, 10). Head with two dense tufts of elongated scales, each of which extends from behind antennal socket, covers scapus basally and eye anteriorly (Fig. 3). Flagellum in proximal part with one wide ring formed by four blackish segments before middle, in distal part with four black rings, two first of them equal in width and located just beyond the middle (Fig. 4). Forewing length 3.1–3.2 mm. Forewing light beige, interspersed with brownish scales, located more densely along dorsal margin; with yellowish-brown stripe along costal margin from base to 3/5 of wing length, which widened distally and not reaching level of cell end (Figs 1, 5, 10); distinct small black spot of raised scales at cell end; large greyish brown spot posteriad the latter; and with indistinct brownish band along distal third of costal edge; fringe light beige on costal and outer edges and dark grey on posterior margin. Hindwings and fringe dark grey.

Male genitalia (Figs 12, 13). See the generic description above.

Female genitalia (Figs 14–16). Ovipositor short, membrane between 9 th and 8 th segments about two times shorter than papillae anales. Glandular sac located at the base of apophyses posteriores on dorsal side. Apophyses posteriores and apophyses anteriores equal in length. 8th segment consists of two lateral sclerotisations and two membranous areas between them, of which ventral wider. Ostium placed almost at level of posterior margin of 7 th segment, wide, about half of 8 th segment width, covered by rectangular antevaginal plate bearing small setae on inner surface and two drop-like lobes at each side (Fig. 15). Postvaginal plate as trapezoid transverse band. Antrum funnel-shaped, sclerotised, relatively long, almost equal to 8 th segment in length, immerged under 7 th segment and joined with its posterior margin, which with rounded sclerotised pockets on medial side at each side of antrum; anterior part of antrum weakly sclerotised and flattened in place where passing into ductus bursae. Ductus bursae membranous, smoothly widened towards corpus bursae. Corpus bursae oval with two small thorn-shaped signa, each placed on oval sclerotisation (Fig. 16).

Distribution. East Malaysia (Sabah) and Indonesia (Sumatra).

Etymology. The name of the new species is derived from the Latin roots “ fusc -” and “ margin -”, meaning “dark”, and “border”, referring to the pattern of the moth’s forewing with a dark stripe along the costal edge.

Remarks. Two specimens, both females, collected in Sumatra are not included in type series of M.fuscomarginata sp. nov. since they differ from Malaysian specimens from Sabah by brownish costal stripe (Fig. 5) and some structures of the female genitalia. One of them has relatively narrower and longer antrum and closely placed drop-like lobes of antevaginal plate (Fig. 18), the other female has larger signa and underlying sclerotisation, whereas size of antrum corresponds to that in the paratype (Figs 19–21).