Sweltsa dilatata Zhang, Li & Li, sp. nov.

(Figs. 1–3, 6a–6b, 7)

Adult habitus. (Figs. 1a–1b, 3a). General body color pale in ethanol. Head with a large, rectangular median dark brown marking covering ocellar area and frons; compound eyes dark, ocelli with dark rings, anterior ocellus paler; antennae pale, distal flagella slightly darker. Brown rugosities present posterior to each eye (Figs. 1a, 3a). Pronotum with wide, dark median stripe and dark brown rugosities, dark margins narrow. Meso- and metanotum with darkbrown U-marks. Wing membrane transparent (Fig. 1b); legs pale. Abdominal tergum 1 with anterior margin dark brown and terga 1–2 with lateral margins dark brown, tergum 1 with median triangular stripe, terga 2–7 each with median trapezoidal stripe, tergum 8 with median elliptical stripe, stripe generally dark brown. Cerci pale brown with long whorled setae.

Male. (Figs. 2, 6a–6b, 7). Forewing length 10.3 mm (n=3); hindwing length 9.2 mm (n=3). Tergum 9: medial portion membranous, transverse ridge strongly band-shaped in dorsal aspect, the ridge slightly elevated in lateral aspect (Figs. 2a–2b). Sternum 9: subgenital plate broad, posterior margin trapezoidal (Fig. 2e). Epiproct long and recurved, gradually changes from black to brown from the base to the median portion, apex pale; parallel-sided for its most length with slightly wider base and narrower apex in dorsal view; in lateral view, apex swollen, rounded and slightly bent upwards, the median portion of epiproct is narrow (Figs. 2c–2d, 6a–6b, 7).

Female. (Fig. 3). Forewing length 9.3 mm, hind-wing length 8.2 mm. Habitus is generally similar to the male, but a pair of anterolateral areas of median ocellus is pale (Fig. 3a). The subgenital plate of sternum 8 is triangular with truncate tip and subapical constriction, and expanded in lateral view. Posterior margin of the subgenital plate with a small triangular notch (Figs. 3b–3d).

Type Material. Holotype male (HIST), CHINA: Chongqing municipality, Wuxi County, Yintiaoling National Natural Reserve, Hongqi Management and Protection Station, 1117m, 31.5090 N, 109.8196 E, 2022.IX.22, leg. Xulong Chen. Paratypes: 1 male, same data as holotype; 1 male, Chongqing municipality, Wushan County, Wulipo National Nature Reserve, Xiaocangping, 2200 m, 31.4112 N, 110.0890 E, 2022.VIII.11, leg. Yameng Wang ; 1 female, Chongqing municipality, Wuxi County, Yintiaoling National Natural Reserve, Shimenzi, 2267.5m, 31.5029 N, 109.7229 E, 2022.VIII.15, leg. Yao Yao.

Etymology. The Latin “dilatata ” refers to the epiproct in lateral view with a swollen apex.

Distribution. China (Chongqing municipality).

Remarks. The color pattern of head and pronotum of Sweltsa dilatata sp. nov. is similar to S. baiyunshana Li, Yang & Yao, 2014 and S. bilobata Mo, Ye, Wang & Li, 2020 . However, the new species can be distinguished from S. baiyunshana and S. bilobata by the median portion of epiproct being narrower and the teardrop-shaped apex in lateral view. In S. baiyunshana, the epiproct is gradually widened from the base to the apex and the apex bears a tongue-like cap which is absent in the new species. In S. bilobata, the basal half of epiproct is narrow and the apical half is wide in lateral view. Additionally, the female subgenital plate of the new species is narrower and triangular with truncate tip and subapical constriction which is easy to distinguish the females of S. baiyunshana and S. bilobata .