Isonychia ignota (Walker, 1853)

Qiang, Xin-He & Zhou, Chang-Fa, 2023, A preliminary review of Isonychia Eaton, 1871 from Chinese mainland with a re-description of I. kiangsinensis Hsu, 1936 (Insecta, Ephemeroptera, Isonychiidae), ZooKeys 1178, pp. 115-141 : 115

Isonychia ignota (Walker, 1853)

Baetis ignotus Walker, 1853: 571 (type locality: unknown, probably western Europe; holotype, male, in Natural History Museum, London; figured by Kimmins 1960: 275).

Isonychia ignota : Eaton 1871: 135.

Isonychia ferruginea Albarda, 1878: 128 (synonymized by Eaton 1885: 205).

Siphlurus sp.: Rostock 1878: 88 (synonymized by Eaton 1885: 205).

Chirotonetes ignotus : Eaton 1885: 205.

Palingenia roeselii Joly, 1871: 3 (adults and nymph) (transferred to Jolia by Eaton 1881: 192) (synonymized by Needham 1905: 28).

Isonychia (Isonychia) ignota : Kondratieff and Voshell 1983: 134; Tiunova et al. 2004: 7 (nymph and adults).

Isonychia hainanensis She et You, 1988: 29 (adults) (synonymized by Tiunova et al. 2004: 7).

Material examined.

3 male imagos, 9 female imagos, 8 male subimagos, 2 female subimagos, and 15 nymphs, Bawangling , Hainan Province, China, 14-IX-2015, collected by Qin Si, Junzhi Sun, Juanyan Luo.

Diagnosis.

The nymph of this species can be identified by its body with a pale midline from head to abdominal terga VII, tergum X with dark posterior half, and its gills with spines along whole margins (Fig. 2A, B ). The male imago is characterized by its wings without any markable painting or pigments, MP of hindwing forked more apically than MA, and two forking points are distinct (Fig. 2C, D ), almost total dark forelegs, especially its foretarsi (apical segment usually darker) (Fig. 2G ), penes with clear membranous processes ventrally, and apical margin of penis distinctly convex (Fig. 2H-J ). The body color is almost brownish to dark brown, with a clear median, longitudinal, pale line on terga I-X, anterior margins of each tergum pale (Fig. 2F ). Female imago has a similar color pattern of body and foreleg to the male. Veins of wings are reddish brown to dark, very clear. Posterior margin of sternum IX is shallowly concave (Fig. 2E ).

Generally, the males of this species can be identified by their uniform dark forelegs and shorter segment II of gonostyli. The nymphs can be classified by their gills (color and spine pattern) and color pattern of their abdomen.

Description.

See Tiunova et al. (2004).

Distribution.

China (Hainan province); Mongolia; Russia; Western Europe ( Tiunova et al. 2004).

Remarks.

This species was first recorded in China as I. hainanensis by She and You (1988). However, Tiunova et al. (2004) synonymized it with the species I. ignota . We checked the holotype of the former species and found only very delicate and slight differences between them, like color and shape of penes, but we believe those differences are caused by long-term storage in alcohol of the holotype. In April 2023, we also visited some localities of the types in Hainan Island, China, and collected many specimens of the genus Isonychia . However, we did not find any of I. hainanensis . Therefore, we think this synonym is correct. Our record shows the species I. ignota has a wide distribution, from western Europe to southern China.

Figures

Figure 2. Imaginal and nymphal structures of I. ignota A nymph (dorsal view) B gill VII C forewing of male D hindwing of male E subanal plate of female (ventral view) F body of male imago (dorsal view) G foreleg of male H male genitalia (ventral view) I penes (dorsal view) J membranous processes (ventral view).