Isonychia kiangsinensis Hsu, 1936

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 kiangsinensis Hsu, 1936

Isonychia kiangsinensis Hsu, 1936: 323 (male, male subimago). Types from Shang Jao, Sheng Mi, Jiangxi province, China.

Isonychia kiangsinensis : Gui 1985: 80; You and Su 1987: 334 (nymph); You and Gui 1995: 23; Su and Zhou 1998: 28; Gui et al. 1999: 326; Zhou et al. 2015: 118 (adult, nymph); Tiunova et al. 2004: 2; Vasanth et al. 2019: 169; Muthukatturaja et al. 2021: 284).

Material examined.

Designated neotype (male imago), Leiguling Water, Wuyishan Nature Reserve, Jiangxi Province, China, 27°99142′N, 117°89111′E, 424 m, 4-VI-2005, collected by Lianfang Yang, Christy Jo Geraci. 80 male imagos, same data as the neotype ; 1 male imago, 2 female imagos, 1 male subimago, 4 female subimagos, 1 nymph, and 7 exuviae of nymphs, grass carp Pond , Jingning She Autonomous County, Lishui City, Zhejiang Province, China, 11-12-VIII-2020, collected by Xuhongyi Zheng, Zhenxing Ma ; 1 male imago, 5 female imagos, and 2 male subimagos, Dagu Mountain Scenic Area , Yi County, Huangshan City, Anhui Province, China, 4-X-2021, collected by Xuhongyi Zheng, Dewen Gong ; 7 nymphs and 3 exuviae of nymphs, Nanping City , Fujian Province, China, 118°7′38″E, 26°38′12″N, 190 m, 4-V-2021, collected by Zhengxin Ma, Xuhongyi Zheng ; 16 male imagos and 20 female imagos, Daqiutan , Jiulianshan Forest Farm, Longnan County, Jiangxi Province, China, 10-XII-2005, collected by Changfa Zhou, Changhai Sun.

Diagnosis.

The male imago of the species I. kiangsinensis can be identified by following characters: (1) the body is almost pink to reddish brown (Fig. 3A, D ). (2) wings totally transparent except semitransparent pterostigma, without any other markable painting or pigments (Fig. 4A, B ). (3) each penis near triangular with oblique apical margin (Fig. 4E ); (4) inner margin of segment II of gonostylus slightly concave or straight; the combined length of segments III and IV subequal to segment II (Fig. 4C, D ). (5) forefemora and foretibiae totally dark brown; foretarsal segments I-IV pale in basal half and dark in apical half, segment V gray to dark (Fig. 3E ); (6) foretarsi are longer than tibiae, their length ratio is 1.1: 1.0 (Fig. 3E ).

In contrast to I. ussurica ussurica Bajkova, 1970, I. ussurica sibirica Tiunova et al., 2004, and I. vshivkovae vshivkovae Tiunova et al., 2004 (see below), I. radhae Muthukatturaja et al., 2021, forewings of I. kiangsinensis are transparent, without clear markings (Fig. 4A, B ). Unlike I. guixiensis , I. ignota , and I. moyarensis Vasanth et al., 2019, abdomen of I. kiangsinensis is pink to reddish, with a distinct median pale line but without any obvious dark markings (Fig. 3D ). Although I. kiangsinensis and I. ignota have similar transparent wings and gonostyli (segment II is relatively short), their penes and forelegs are different: (1) I. kiangsinensis has triangular penes (Fig. 4C-E ), but those of I. ignota are nearly cylindrical with convex apical margins; (2) foretarsi of I. kiangsinensis have pale basal 1/2 and dark apical 1/2 (Fig. 3E ), but those of I. ignota are totally dark; (3) foretarsi of I. kiangsinensis are longer than foretibiae while foretarsi of I. ignota are subequal to or shorter than foretibiae.

Four characters can be used to separate nymphs of I. kiangsinensis from other species: (1) abdominal terga I-X with clear pale median longitudinal line (Fig. 7A, C ), (2) each gill lobe with two to three spots, the largest one in the middle dark purple, (3) gill lobes VI and VII with spines on apical margins (Fig. 10F, G ). (4) Tergum X pale in anterior 1/2, brown in posterior 1/2 (Fig. 10J ). Compared to known nymphs of Asian Isonychia species, gills of I. kiangsinensis usually have three markings, a large median purple one and two small brown ones. This character is somewhat unique. Generally, this species is larger, more reddish than others, and is distributed south of Yangtze River, China.

Description.

Also see Hsu (1936) or You and Su (1987). Male imago (in alcohol, Figs 3 , 4 ): body length 15.0-16.0 mm, cerci 33.0-35.0 mm, forewings 14.0-15.0 mm, hindwings 7.0-8.0 mm. Body generally pink to reddish brown, head, and thorax slightly deeper than abdomen (Fig. 3A-D ). Head: compound eyes almost covered all head, with dark 1/3 lower portion and grey to dark 2/3 upper portion; two eyes contiguous or near contiguous, only a very narrow suture between them. Ocelli with dark basal band, upper portion pale. Antennae pale, ventral surface of scape and pedicle pigmented with brown dots or irregular markings. Anterior margin of head nearly straight (Fig. 3B ). Thorax: pronotum and anterior 1/3 mesonotum with clear dark brown longitudinal stripes but midline pale, median 1/3 mesonotum with a pair of dark brown oblique stripes sub-medially, mesoscutellum and metascutellum dark, other parts reddish brown to brown, including sterna. Basisternum of mesothorax narrowed progressively from anterior to posterior, apex bluntly expanded (Fig. 3C ).

Wings totally transparent except semi-hyaline pterostigma, crossveins of all wings clear (Fig. 4A, B ). Veins of forewings yellowish to reddish, MA forked at apical 1/3, MP forked slightly baser than Rs, asymmetrical; four pairs of forked and two unforked intercalaries between CuA and CuP, A connecting to hind margin with two veinlets (Fig. 4A ). Hindwings with very shallow and blunt costal process at base. MA and MP forked equally, both of them forked symmetrical (Fig. 4B ). Forelegs with deep reddish or chocolate forefemora and tibiae, apical 1/2 of each tarsus except segment V dark but basal 1/2 pale, segment V of foretarsi pale to grey (Fig. 3E ); gill relics of forecoxa gray to dark (Fig. 3E ); two claws similar, blunt, and plate-like (Fig. 3F ). Midleg and hindleg pale, claws similar too but both of them acute (Fig. 3G-I ). Length ratio of forefemora: tibiae: tarsi = 1.0: 1.4: 1.6, length ratio of foretarsal segments from I to V = 1.0: 0.8: 0.6: 0.5: 0.4; length ratio of mid-femora: tibiae: tarsi = 1.0: 1.3: 0.6, length ratio of mid-tarsal segments from I to V = 1.0: 1.2: 0.8: 0.8: 1.4; length ratio of hind femora: tibiae: tarsi = 1.0: 0.9: 0.5, length ratio of hind-tarsal segments from I to V = 1.0: 0.9: 0.7: 0.5: 1.2. Abdomen: terga reddish brown to pink, with a median longitudinal pale line, posterior margins of each tergum brown to dark, deeper than other parts. Base of cerci reddish brown, other part pale, surface with tiny setae. Terminal filament pale to reddish brown, six or seven segments (Fig. 3D ). Genitalia: subgenital plate deeply incaved with a semi-circular median lobe; inner surface of second segment of gonostylus concave; length ratio of four segments of gonostylus from base to apex = 1.0: 7.0: 3.5: 2.5 (Fig. 4C, D ). Two penes fused at basal 1/3 but bifurcated at apical 2/3, slightly bent laterally; each penis near triangular with a sharp apex (Fig. 4E ).

Male subimago (in alcohol, Fig. 4F, G ): body length 12.0-13.0 mm, cerci 19.0-20.0 mm. Length ratio of forefemora: tibiae: tarsi = 1.0: 1.1: 1.0, length ratio of foretarsal segments I: II: III: IV: V = 1.0: 0.6: 0.6: 0.6: 0.8; length ratio of mid-femora: tibiae: tarsi = 1.0: 0.8: 0.4, length ratio of mid-tarsal segments I: II: III: IV: V = 1.0: 0.7: 0.8: 0.4: 1.0; length ratio of hind femora: tibiae: tarsi = 1.0: 0.6: 0.5, length ratio of hind-tarsal segments I: II: III: IV: V = 1.0: 0.8: 0.5: 0.6: 1.5. Body duller than male imago, wings semi-hyaline, amber to brown. Crossveins of wings surrounded with grey to dark cloud (Fig. 4F ). Genitalia generally similar to those of male imago but apical margin of penes only slightly oblique, second segment of gonostylus thickened (Fig. 4G ).

Female imago (in alcohol, Figs 5 , 6 ): body length 20.0-21.0 mm, cerci 42.0-44.0 mm, forewings 19.0-20.0 mm, hindwings 7.8-8.8 mm. Length ratio of forefemora: tibiae: tarsi = 1.0: 1.5: 1.6, and length ratio of foretarsal segments from I to V = 1.0: 0.9: 0.8: 0.5: 0.8; length ratio of mid-femora: tibiae: tarsi = 1.0: 1.1: 0.5, and length ratio of mid-tarsal segments from I to V = 1.0: 0.9: 0.6: 0.6: 1.5; length ratio of hind femora: tibiae: tarsi = 1.0: 0.8: 0.5, and length ratio of hind-tarsal segments from I to V = 1.0: 0.9: 0.5: 0.5: 1.5. Body color pattern similar to male but paler (Fig. 5A ). Compound eyes dark, distance between them ~ 3 × diameter of ocellus. Two dark dots on occiput nearby eyes (Fig. 5C ). Gill relics of forecoxa gray to dark (Fig. 5D ). Veins of wings clearer than males, MP of hindwing forked more apically than MA (Fig. 6A, B ). Abdomen more reddish than male, posterior 1/2 of tergum and sternum usually deeper than anterior 1/2 (Fig. 5E ). Sternum VII extended posteriorly into a small lobe (Fig. 6D, E ), sternum IX narrowed progressively and smoothly from base, posterior margin incaved into semi-circular shape (Fig. 6C ).

Female subimago (in alcohol, Fig. 5B ): body length 14.0-15.0 mm, cerci 17.0-18.0 mm. Length ratio of forefemora: tibiae: tarsi = 1.0: 1.3: 0.6, length ratio of foretarsal segments I: II: III: IV: V = 1.0: 0.6: 0.7: 0.4: 0.8; length ratio of mid femora: tibiae: tarsi = 1.0: 0.7: 0.4, length ratio of mid-tarsal segments I: II: III: IV: V = 1.0: 0.8: 0.6: 0.4: 1.2; length ratio of hind femora: tibiae: tarsi = 1.0: 0.7: 0.3, length ratio of hind-tarsal segments I: II: III: IV: V = 1.0: 0.7: 0.6: 0.5: 1.5. Similar to female imago but body duller and wings semi-hyaline, amber to brown.

Nymph (in alcohol, Figs 7 - 10 ): body length 13.0-17.0 mm, cerci 8.0-10.0 mm, terminal filament 5.0-6.5 mm; body brown to dark amber, with a clear pale median longitudinal line; legs and tail with pale and dark bands, gills with purple markings (Fig. 7A-D ). Head: genae brown, lateral 1/3 clypeus brown but median 1/3 pale; scape and pedicel of antennae darker than others, antennae smooth. Length of antennae ~ 3 × width of head. Frontal carina pale, area between three ocelli brown, midline of head pale, area between median ocellus and compound eyes pale too. Frontal carina between two antennae, very sharp. Vertex smooth and convex. Dark base of ocelli clear (Fig. 7E, G ).

Mouthparts: dorsal surface and anterior margin of labrum with long hair-like setae, dorsal surface with additional bristles, ventral surface with two oblique lines of hair-like setae; anterior margin almost straight, lateral margins slightly convex (Fig. 8A ). Left mandible: apex of both inner and outer incisor divided into three denticles, outer incisor slightly thinner than inner one; prostheca composed with a distinct spur and a tuft of spines (Fig. 8B ). Right mandible: outer and inner incisor divided into two denticles, prostheca composed with a tuft of spines, a line of hair-like setae on mesal margin near molar (Fig. 8C ). Hypopharynx: lingua nearly circular, with hair-like setae on ventral apex; superlinguae with straight lateral margins, apex with hair-like setae too (Fig. 8D ). Maxillary palpi yellowish brown, length ratio of segments I and II = 1.0: 2.0; apical segment covered with dense hair-like setae and slightly broader than basal one. Two gill tufts between maxilla and labium (Fig. 8E ). Galea-lacinia of maxilla with two apical canines, mesal margin with a row of hair-like setae, one distinct spine among them. Crown of maxilla and outer 1/2 surface of both sides with hair-like setae, an additional row of short hair-like setae near canine on ventral surface (Fig. 8F ). Glossae and paraglossae of labium heart-shaped, the latter broader than the former, surface of them with dense hair-like setae, those on margins longer. Labial palpi darker, basal segment: apical segment = 1.0: 2.0, outer margin with long hair-like setae, inner 1/2 surface of it with brush-like setae (Fig. 8G ).

Thorax: color brown, with a median pale line and several irregular pale dots or markings on dorsal surface. Mesosternum and metasternum with a projection respectively directed posteriorly, the latter one broader and shorter (Fig. 7F ). Gill tuft on forecoxa with pale body but gray filaments. Femora of foreleg with three pale bands on base, middle and apex respectively, tibiae with two pale bands on base and apex, apical 1/2 of tarsi pale, claw pale but with golden apex (Fig. 9A ). Inner margin of foreleg with long hair-like setae but outer margin with bristles; apical spine of tibiae ~ 3/4 tarsi, it slightly bent. Claw with five or six denticles (Fig. 9B ). Femora: tibiae: tarsi of foreleg = 1.0: 1.0: 0.6. Color pattern of midleg similar to foreleg, both outer and inner margins with spine-like setae only. Claw of midleg with eight or nine denticles (Fig. 9C, D ). Femora: tibiae: tarsi of midleg = 1.0: 0.6: 0.4. Color and setae pattern of hind leg similar to midleg (Fig. 9E ). Ventral cleft of hind femora usually with four spines (Fig. 9F ). Femora: tibiae: tarsi of hind leg = 1.0: 0.5: 0.3.

Abdomen: brown, with a pale median line on terga I-VI, an additional pair of pale median oval dots beside line. Posterolateral angles of terga I-VII extended into blunt lobe while those of terga VIII and IX extended into spines (Fig. 7A-D ). Gills I-VII similar in color and structure but larger progressively from anterior to posterior except dorsal gill lobes I-V without apical spines. Each gill lobe with three sclerotized ribs, two along margins and one nearly on middle of dorsal surface. Each gill with three purple dots, a bigger median one, a small apical one and the smallest anterolateral one. Front margin of each gill lobe slightly straighter than hind margin; ventral gill filament tuft with purple median 1/2, other parts pale (Fig. 10A-G ). Sternite IX with distinct semi-circular shape cleft in both sexes (Fig. 10H, I ). Anterior 1/2 of tergum X pale, posterior 1/2 brown (Fig. 10J ).

Caudal filaments: mesal margin of 2/3 cerci and bilateral margins of terminal filaments with strong hair-like setae. Tail with pale band at 2/3 length (Fig. 7H ).

Egg. Spherical, densely covered with subequal tubercles, without clear reticulation (Fig. 11A, B ); one micropyle observed (Fig. 11C ).

Distribution.

China (Jiangxi, Fujian, Anhui, Zhejiang provinces).

Remarks.

The holotype and paratypes of this species were lost. Both the newly found specimens and original descriptions of Hsu (1936) show this is a valid species; therefore, a male from Jiangxi Province, China (same province as the types) is designated here as its neotype.

The nymphs of I. kiangsinensis have posterolateral projections on terga VIII and IX (Fig. 7A-D ), which was missing in the description of You and Su (1987). However, Vasanth et al. (2019) and Muthukatturaja et al. (2021) reported wrongly that I. kiangsinensis has projections on terga I-IX.

Figures

Figure 3. Structures of I. kiangsinensis male imago A habitus (lateral view) B head (dorsal view) C thorax (ventral view) D abdomen (dorsal view) E foreleg (arrow indicating the gill relics on forecoxa) F claw of foreleg G midleg H hindleg I claw of midleg.

Figure 4. Male structures of I. kiangsinensis A-E male imago F-G male subimago A forewing B hindwing C male genitalia (ventral view) D male genitalia (dorsal view) E penes (ventral view) F habitus (lateral view) G genitalia (ventral view).

Figure 5. Female structures of I. kiangsinensis A imago (lateral view) B subimago (lateral view) C head of imago (dorsal view) D head and prothorax of imago (ventral view, arrow indicating the gill relics on forecoxa) E abdomen of imago (dorsal view).

Figure 6. Structures of I. kiangsinensis female imago A forewing B hindwing C subanal plate D abdominal segments VII-X (ventral view) E abdominal segments VII-X (lateral view).

Figure 7. Nymphal structures of I. kiangsinensis A female nymph (dorsal view) B female nymph (ventral view) C male nymph (dorsal view) D male nymph (ventral view) E head of female F thorax of female (ventral view) G antenna H caudal filaments.

Figure 8. Mouthparts of I. kiangsinensis nymph A labrum B left mandible C right mandible D hypopharynx E maxilla F galea-lacinia of maxilla G labium.

Figure 9. Nymphal legs of I. kiangsinensis A foreleg B apical spine of foretibiae C midleg D claw of midleg E hind leg F ventral cleft of hind femur (ventral view).

Figure 10. Nymphal structures of I. kiangsinensis A - G gills I-VII H female sternite IX (ventral view) I male sternite IX (ventral view) J tergite X (dorsal view).

Figure 11. Egg of I. kiangsinensis A overall view B surface enlarged C micropyle.