Siphlonurus lacustris Eaton, 1870

Qiang, Xin-He & Zhou, Chang-Fa, 2025, The species diversity and phylogeny of the genus Siphlonurus Eaton, 1868 from China (Ephemeroptera: Siphlonuridae), Zootaxa 5711 (1), pp. 1-56 : 17

Siphlonurus lacustris Eaton, 1870 (first record from China)

Figures 9–10

Siphlonurus lacustris Eaton, 1870: 7 (male imago, from Europe).

Siphlonurus zetterstedti Bengtsson, 1909: 9 (synonymized by Brekke 1965: 12).

Siphlonurus pyrenaicus Navás, 1930: 53 (synonymized by Puthz 1977: 169).

Siphlonurus nuessleri Jacob, 1972: 144 (synonymized by Puthz 1977: 169).

Siphlonurus lacustris : Eaton 1885: 217; Grandi 1960: 71 (nymph and male imago); Studemann et al. 1988: 309 (male and female imago); Studemann et al. 1992: 80; Gaino & Rebora 2001: 41 (egg); Bauernfeind & Soldán 2012: 73.

Material examined: 3 nymphs, Xingan National Forest Park, Yichun City , Heilongjiang Province, 13–14.VII.2016, Juan Yan Luo , Wei Zhang , and Ze Hu ; 1 nymph, Laocaohe , Mohe City , Daxinganling District , Heilongjiang Province, 52.833392°N, 122.591656°E, ca. 480 m, 16–19.VII.2024, Xinhe Qiang , Ningning Wang , and Yuxian Sun ; 3 nymphs, 2♀ imagos, 1♂ imago, Wuying Forest Park , Fenglin County, Yichun City, Heilongjiang Province, 48.204776°N, 129.209142°E, ca. 300 m, 17–20.VII.2024, Dewen Gong and Xuhongyi Zheng; 1♀ imago, ♂ imago, Liujiazi, Gaoleng Town , Fangzheng County , Harbin City, Heilongjiang Province, 45.731443°N, 129.290088°E, ca. 330 m, 21–22.VII.2024, Dewen Gong and Xuhongyi Zheng .

Description: see Bauernfeind & Soldán (2012), Studemann et al. (1988) and Gaino & Rebora (2001).

Distribution: The species is found throughout the Palaearctic region, but it is the first record from China here. It is found in Heilongjiang Province.

Diagnosis

Mature nymph: Body length 14.0–16.0 mm, wingpads without spots ( Figs 9A, B ). Length ratio of first segment of maxillary palp to galea-lacinia about 1.0: 0.9, inner margin of maxillary palp segment II straight ( Fig. 9C ). Posterolateral spines on terga I–IX gradually larger from anterior to posterior, length ratio of posterolateral spine on tergum IX to its tergum = 1.0: 3.0 ( Figs 9D, E ). Each abdominal sternum with an inverted U-shaped marking ( Fig. 9B ). Posterior margin of abdominal sternum IX slightly convex ( Fig. 9E ). Dorsal surface and posterior margin of tergum X with stout and pointed spine-like setae, lateral margins lack ( Fig. 9F ). Outer margins of dorsal and ventral lamellae of both gills I and II concave, costal rib of dorsal lamella in gill II shorter than half of anterior margin ( Figs 9G, H ). Outer and posterior margins of gill III concave, proximal plate of gill VII well developed ( Figs 9I, J ).

Male imago: Body length 11.5–15.0 mm, wings transparent, all legs generally light brown ( Figs 10A–C ). Posterolateral spines of abdominal segments VIII and IX relatively small ( Figs 10D–G ). Each abdominal sternum with an inverted U-shaped marking ( Fig. 10F ). Inner margin of basal segment of forceps with a projection, length of penis subequal to styliger ( Figs 10 D, E ). Dorsal elongation of penis short, sharp, and spineless, dorsal sclerotized transverse band of penis expanded in the middle, inner margin of each penis lobe with 5–6 long spines, outer margin with approximately four small spines, each penis lobe with a short and wide projection posterolaterally ( Figs 10H–J ).

Female imago: Body length 13.0–15.0 mm, wings transparent. Color pattern similar to male ( Fig. 10K ). Sternum VII extended posteriorly into a triangular lobe, sternum VIII with funnel-shaped dark brown sclerotized line ( Fig. 10L ).

Remarks: see remarks of S. polyspineus sp. nov.

Figures

FIGURE 9. Nymph of Siphlonurus lacustris: (A) nymph (dorsal view); (B) nymph (ventral view); (C) maxilla; (D) abdominal terga I–IV (dorsal view); (E) abdominal sternum IX of female (ventral view); (F) abdominal tergum X (dorsal view); (G) gill I; (H) gill II; (I) gill III; (J) gill VII.

FIGURE 10. Imago of Siphlonurus lacustris: (A–J) male structures: (A) male imago (lateral view); (B) forewing; (C) hindwing; (D) genitalia (dorsal view); (E) genitalia (ventral view); (F) abdomen (dorsal view); (G) abdomen (ventral view); (H) penis (dorsal view); (I) penis (ventral view); (J) magnification of spines on penis lobe; (K) abdomen of female imago (ventral view); (L) sternum VII of female imago.