Isocapnia guentheri (Joost, 1970)

(Figs. 4–6)

Capnia guentheri Joost, 1970: 38.

Isocapnia guentheri: Zhiltzova 1972: 122; Zhiltzova 2003: 404; Zenger & Baumann 2004: 81; Teslenko & Bazova 2009: 1061; Teslenko & Zhiltzova 2009: 182; Judson & Nelson 2012: 20; Chen & Du 2017: 20.

Female (Figs. 4–6). Forewing length 6.9 mm (n=1). Body generally dark brown. Head slightly wider than pronotum; compound eyes black, three ocelli each with obscure dark margins (Fig. 4a). Precoxal bridge fused with basisternum; furcasternum fused with basisternum and furcasternal arms (Fig. 4b). Wings macropterous, subhyaline with brown venation; forewings with two costal cross veins before end of Sc (Fig. 5). Sternum 8 medially membranous, subgenital plate deeply incised, and the sclerotized portion flush with the preceding membrane, lateral sclerites subtriangular with rounded angles (Fig. 6c).

Material examined. 1 female (HIST), China: Heilongjiang Province, the Greater Khingan Mountains area, Huzhong District, Xiangyang South Road, Dabaishan Hotel, 522 m, 51.6001º N, 124.3540º E, 2023. VIII. 10. leg. Weihai Li, Yao Zhang.

Distribution. Eastern Palaearctic species. China (Heilongjiang Province); Mongolia; Russian Far East (from Chukchi Peninsula to Primorskii Territory and Sakhalin Island).

Remarks. This species was originally described from Mongolia (Joost, 1970) and has also been documented throughout the Russian Far East (Zenger & Baumann 2004). This is the first record of this species, and the fourth species of this genus recorded from China (Yang & Du 2024). Sternum 8 simply and straightly truncate but exhibits a typical blunt V-shaped pattern (Fig. 6a). There are some slight variations in the female subgenital plate. Sternum 8 with membranous pale area at medial portion anteriorly. Subgenital plate is reduced, forming only a semicircular median sclerite on the posterior margin of sternum 8, accompanied by a pair of lateral sclerites. Sternum 9 with two sclerotized spots on each lateral portion (comparing Figs. 6c–d with Fig. 6b). The subgenital plate of this female are generally in close agreement with the illustrations in Teslenko (2009). And there is a minor difference with the original illustrations (Joost 1970). However, the general shape in outline is identical and hence considered here as intraspecific variation.