Acroneuria songhaitiani sp. nov.

Figs. 5–9.

Adult habitus (Figs. 5–6). Three ocelli. General color yellow. Head slightly wider than pronotum; anterior ocellus smaller than posterior ones, with a dark posterior spot; posterior ocelli each with a dark spot, the two spots separated or connected. Antenna dark brown and slender, subequal in length to the abdomen, apical segments paler. Pronotum pale, with obscure rugosities, anterior corners sharp. Wing membrane subhyaline, veins pale brown; apices of wings pale. Coxae pale; distal part of femur, tibia and tarsi dark brown. Cercus pale, apical segments dark.

Male (Figs. 5, 7, 8). Body length 20.0– 21.5mm; forewings length ca. 23.5 mm, hindwings length ca. 21.0 mm. Tergum 9 without sensilla basiconica. Tergum 10 with a large, heart-shaped sensilla basiconica patch. Paraprocts sclerotized, subtriangular and upcurved, apically with a small triangular spine. Posterior margin of sternum 9 with a rounded hammer. Aedeagus (Fig. 8C) mostly membranous, basally constricted, apical half with two oblique sclerites, each sclerite covered with spinules.

Female (Figs. 6, 9). Body length ca. 26.0 mm; forewings length ca. 29.0 mm, hindwings length ca. 26.0 mm. Subgenital plate from half-length of sternum 8, broadly rounded, posterior margin truncate, reaching posterior margin of sternum 9 (Fig. 9A). Sternum 9 with a triangular posterior margin.

Egg (Figs. 9B, C). Length ca. 0.4 mm, width ca. 0.2 mm. Color generally pale brown; acorn-shaped. Collar flat, sclerotized and very small. Chorion smooth, without micropyles.

Type material. Holotype: male, Vietnam: Quang Nam Province, Tay Giang District, Axan Commune, Song Kool River, 15.83 N, 107.31 E (Fig. 1), 1300m, July–August 2019, light trap (ICJUST) . Paratypes: 1 male and 2 females, same data as holotype (ICJUST) .

Etymology. The species is named for Dr. Hai-Tian Song for obtaining the specimens. The name is used as a noun.

Remarks. The new species can be easily distinguished from known Vietnamese Acroneuria species by the two closely-located, oblique sclerites of the aedeagus and by the unnotched subgenital plate of the female.