Siphlonurus immanis Kluge, 1985

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 : 14

Siphlonurus immanis Kluge, 1985

Figures 7–8

Siphlonurus chankae : Bajkova, 1979: 53 ( nec Siphlonurus chankae Tshernova, 1952 ) (nymph from Russia).

Siphlonurus immanis Kluge 1985: 18 (imagos and nymph from Russia); Hwang & Bae 2001: 47 (nymph); Quan et al. 2002: 258 (first record from China); Tiunov & Tiunova 2007: 23; Zhou 2013: 204 (list); Zhou et al. 2015: 254 (list).

Material examined: 15 nymphs, Sanbao Village, Songfengshan Town, Acheng District , Harbin City , Heilongjiang Province, 1.IV.2023, Qiang Dong ; 200 nymphs, 20 nymph exuviae, Erdaohzi , Sanbao Village , Songfeng Mountain Town , Acheng District , Harbin City , Heilongjiang Province, 45.245339°N, 127.263786°E, ca. 260 m, 27–28.IV.2024, Xinhe Qiang , Muhe Deng , and Mengyao Li ; 5 nymphs, Dashihe , Xinxing Village , Acheng District , Harbin City , Heilongjiang Province, 45.233113°N, 127.154525°E, ca. 370 m, 29.IV.2024, Xinhe Qiang , Muhe Deng , and Mengyao Li ; 3 nymphs, Tangwanghe , Haolianghe Town , Nancha District , Yichun City , Heilongjiang Province, 46.431801°N, 129.374393°E, ca. 110 m, 4.V.2024, Xinhe Qiang , Muhe Deng , and Mengyao Li ; 100 nymphs, 50 nymph exuviae, 60 ♀ imagos, 28 ♂ imagos, Erdaohzi, Sanbao Village , Songfeng Mountain Town , Acheng District , Harbin City, Heilongjiang Province, 45.245339°N, 127.263786°E, ca. 260 m, 23–29.V.2024, Xinhe Qiang and Xiaofang Chen .

Description: see Kluge (1985, adult and nymph) and Hwang & Bae (2001, nymph).

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

Diagnosis

Mature nymph: Body length 18.0–25.0 mm, wingpads without spots ( Figs 7A, B ). Length ratio of first segment of maxillary palp to galea-lacinia about 1.0: 1.0, inner margin of maxillary palp segment II straight ( Fig. 7C ). 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: 2.0 ( Figs 7D–F ). Each abdominal sternum with inverted U-shaped marking ( Fig. 7B ). Posterior margin of abdominal sternum IX nearly straight ( Figs 7E, F ). Dorsal surface and posterior margin of tergum X with stout and pointed spine-like setae, lateral margins lack ( Fig. 7G ). 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 7H, I ). Outer and posterior margins of gill III concave, proximal plate of gill VII well developed ( Figs 7J, K ).

Male imago: Body length 20.5–22.0 mm, all legs brown ( Fig. 8A ), wings transparent ( Figs 8C, D ). Posterolateral spines of abdominal segments VIII and IX relatively large ( Fig. 8E, F ). Each abdominal sternum with inverted Ushaped marking ( Fig. 8F ). Inner margin of basal segment of forceps with projection, length of penis subequal to styliger ( Figs 8G, H ). Dorsal elongation of penis slender and spineless, dorsal sclerotized transverse band of penis without expansion, two penis lobes separated, each tip bifurcated, outer bifurcation distinctly sclerotized, ventral side with a translucent membranous structure, inner margin of each penis lobe with 4–6 small spines basally, outer margin concave near the middle ( Figs 8I, J ).

Female imago: Body length 27.0–29.0 mm, wings transparent ( Fig. 8B ). Color pattern similar to male ( Fig. 8K ). Sternum VII extended posteriorly into a triangular lobe, sternum VIII with W-shaped dark brown sclerotized line ( Fig. 8L ).

Remarks: This species is close to S. chankae . The detailed comparison is presented in the remarks of S. chankae .

Figures

FIGURE 7. Nymph of Siphlonurus immanis: (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 sternum IX of male (ventral view); (G) abdominal tergum X (dorsal view); (H) gill I; (I) gill II; (J) gill III; (K) gill VII.

FIGURE 8. Imago of Siphlonurus immanis: (A) male imago (lateral view); (B) female imago (lateral view); (C–J) male structures: (C) forewing; (D) hindwing; (E) abdomen (dorsal view); (F) abdomen (ventral view); (G) genitalia (dorsal view); (H) genitalia (ventral view); (I) penis (dorsal view); (J) penis (ventral view); (K) abdomen of female imago (ventral view); (L) sternum VII of female imago.