Siphlonurus palaearcticus ( Tshernova, 1930 )

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 : 29-32

Siphlonurus palaearcticus ( Tshernova, 1930)

Figures 18–19

Oniscigaster palaearcticus Tshernova, 1930: 217 (female, from Russia).

Siphlonurus binotatus : Imanishi 1940: 232; Bae 1997: 408; Quan et al. 2002: 258 ( nec Siphlonurus binotatus ( Eaton, 1892) : 302, mis-identification).

Siphlonurus binotatus : Bajkova 1979: 56 ( nec Siphlonurus binotatus ( Eaton, 1892) : 302, mis-identification revealed by Soldán et al. 2009: 655).

Siphlonurus brodskyi Bajkova, 1979: 57 (synonymized by Kluge 1985: 12).

Siphlonurus palaearcticus : Kluge 1982: 114 (all stages); Tshernova et al. 1986: 123; Bae & Soldán 1997: 151; Bae & Andrikovics 1997: 159; Bae & Yoon 1997: 50 (catalogue); Hwang & Bae 2001: 49 (all stages); Wang et al. 2009: 196 (list); Zhou 2013: 204 (list, first record from China); Zhou et al. 2015: 106 (nymph and male); 254 (list); Han et al. 2016: 45 (comparison).

Material examined: 21 ♀ imagos, 6♂ imagos, Weihe Yulin Forest Farm, Shangzhi City, Heilongjiang Province, 8–16.VII.1993, Youwen Li and Changhai Sun; 7 nymphs , 60 ♀ imagos, Yalu River, Bugt Town, Yakeshi City , Inner Mongolia, 48.44625°N, 121.54724°E, ca. 670 m, 2–4.VIII.2007, Changfa Zhou, Hui Xie, and Shilei Wang; 3 nymphs , 10 ♀ imagos, Jiliu River, Mangui Town, Genhe City , Inner Mongolia, 52.02925°N, 122.02733°E, ca. 630 m, 12.VIII.2007, Shilei Wang and Hui Xie; 1 nymph , 2♀ imagos, Erdao Baihe Town, Fusong County, Jilin Province, 23–25.VII.2008, Shilei Wang and Guo Zhao; 2 nymphs, Changbai Mountain , Manjiang Town , Fusong County , Jilin Province, 41.9485°N, 127.5907°E, 10.VIII.2022, Xuhongyi Zheng ; 5♀ imagos, Badaohe, Guanmen Mountain, Benxi City , Liaoning Province, 41.146595°N, 124.148296°E, ca. 300 m, 20–24.VII.2023, Shuang Qiu and Xinye Liu ; 2♀ imagos, 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 .

Description: see Kluge (1982) and Hwang & Bae (2001).

Distribution: China ( Heilongjiang Province, Jilin Province, Inner Mongolia); Russia, Korea; Mongolia.

Diagnosis

Mature nymph: The body length 13.0–15.0 mm, wingpads with spots ( Figs 18A, B ). Length ratio of first segment of maxillary palp to galea-lacinia about 1.0: 1.0, inner margin of maxillary palp segment II convex apically ( Fig. 18C ). 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: 4.0 ( Figs 18D, E ). Each abdominal sternum with an inverted U-shaped marking ( Fig. 18B ). Posterior margin of abdominal sternum IX slightly convex ( Fig. 18E ). Dorsal surface and posterior margin of tergum X with stout and pointed spine-like setae, lateral margins lack ( Fig. 18F ). Outer margins of dorsal and ventral lamellae of both gills I and II straight, costal rib of dorsal lamella in gill II shorter than half of anterior margin ( Figs 18G, H ). Outer and posterior margins of gill III straight, proximal plate of gill VII well developed ( Figs 18I, J ).

Male imago: Body length 12.0–13.0 mm, all crossveins of forewing dark brown, with long dark brown stripe near middle of both forewing and hindwing. Forelegs entirely brown, midlegs and hindlegs entirely light brown ( Figs 19A–C ). Each abdominal sternum with inverted U-shaped marking ( Fig. 19D ). Posterolateral spines of abdominal segments VIII and IX relatively small ( Figs 19E, F ). Inner margin of basal segment of forceps with projection, length of penis subequal to styliger ( Figs 19E, F ). Dorsal elongation of penis wide and arched with few spines apically (approximately 2–3 spines), dorsal sclerotized transverse band of penis without expansion, each penis lobe distinctly sclerotized, apex densely covered with spines (approximately 12–14 spines), additional long and slender projection between dorsal elongation and each penis lobe, tip of this projection with two spines ( Figs 19G–I ).

Female imago: Body length 13.0–14.0 mm, wings with brown stripe. Color pattern similar to male. Sternum VII extended posteriorly into a rectangular lobe, medially concave. Sternum VIII with a pair of funnel-like sclerotized line ( Fig. 19J ).

Remarks

Among Siphlonurus species reported in China, only four species ( S. davidi , S. dongxi , S. orientalis sp. nov., and S. palaearcticus ) exhibit wing pigmentation in their adult stage. Among them, S. davidi , S. dongxi , and S. orientalis sp. nov. share a similar wing pigmentation pattern: forewing with dark brown crossveins and large dark brown spots between C and Rs 1; distal half of hindwing light brown, with a spot near middle of R1 and a brown stripe near forking point of MA ( Figs 4B, C , 6B, C , 14B, C ), while S. palaearcticus displays a distinctly different pattern: all crossveins of forewing are dark brown, with dark brown stripes near middle of both forewing and hindwing ( Figs 19B, C ), making it easily distinguishable. Additionally, penis lobe structure of S. palaearcticus is highly unique, featuring an additional slender projection between dorsal elongation and penis lobe, with two spines at its apex ( Fig. 19G ), which is a characteristic not observed in other Chinese Siphlonurus species.

In terms of nymphal morphology, S. palaearcticus combines characteristics of both northern-distributed species ( S. chankae , S. immanis , S. lacustris , S. polyspineus sp. nov., and S. zhelochovtsevi ) and southern-distributed species ( S. davidi , S. dongxi , and S. orientalis sp. nov.). For example, each abdominal sternum of S. palaearcticus bears an inverted U-shaped marking ( Fig. 18B ), lateral margins of tergum X lack stout spine-like setae ( Fig. 18F ), and costal rib of dorsal lamella in gill II is shorter than half of anterior margin ( Fig. 18H ) – features aligning with those of northern-distributed species. On the other hand, outer margins of dorsal lamellae of gills I and II are straight, and outer and posterior margins of gill III are also straight ( Figs 18G–I ) – traits resembling those of southern-distributed species.

Additionally, S. binotatus is likely not distributed in China at present, as this species is currently known only from Japan. The S. binotatus reported by Imanishi (1940) is likely S. palaearcticus . The nymphs of Siphlonurus species are difficult to distinguish morphologically, and both S. binotatus and S. palaearcticus have pigmented wingpads, which can easily lead to mis-identification. Therefore, Imanishi (1940) reported S. palaearcticus in China, while we tentatively exclude S. binotatus from the Chinese fauna.

Figures

FIGURE 4. Imago of Siphlonurus davidi: (A–I) male structures: (A) male imago (lateral view); (B) forewing; (C) hindwing; (D) abdomen (dorsal view); (E) abdomen (ventral view); (F) genitalia (dorsal view); (G) genitalia (ventral view); (H) penis (dorsal view); (I) penis (ventral view); (J) sternum VII of female imago.

FIGURE 6. Imago of Siphlonurus dongxi: (A–I) male structures: (A) male imago (lateral view); (B) forewing; (C) hindwing; (D) abdomen (ventral view); (E) genitalia (dorsal view); (F) genitalia (ventral view); (G) genitalia (lateral view); (H) penis (dorsal view); (I) penis (ventral view); (J) sternum VII of female imago.

FIGURE 14. Male imago of Siphlonurus orientalis sp. nov. (made from the holotype): (A) male imago (lateral view); (B) forewing; (C) hindwing; (D) abdomen (dorsal view); (E) abdomen (ventral view).

FIGURE 18. Nymph of Siphlonurus palaearcticus: (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 19. Imago of Siphlonurus palaearcticus: (A–I) male structures: (A) male imago (lateral view); (B) forewing; (C) hindwing; (D) abdomen (ventral view); (E) genitalia (dorsal view); (F) genitalia (ventral view); (G) magnification of penis lobe; (H) penis (dorsal view); (I) penis (ventral view); (J) sternum VII of female imago.