Rhoenanthus hunanensis Han & Zhang & Zhou 2021, new status
Creators: name: Han, Na
name: Zhang, Min
name: Zhou, Chang-Fa
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Ephemeroptera
Potamanthidae
Rhoenanthus
Rhoenanthus hunanensis

description: Rhoenanthus hunanensis (You & Gui, 1995) new status
Figs 2–5, 6 A–D, 7–8, 11
Neopotamanthus hunanensis You & Gui, 1995: 118, Fig. 125. Types: male and female, from Hunan province, China (based on Neopotamanthus hunanensis Zhang, 1987: 7, unpublished master thesis, authorship unavailable).
Rhoenanthus (Potamanthindus) youi: Bae & McCafferty 1991:29–30 [based on some materials of Neopotamanthus hunanensis Zhang, 1987: 7; nec Rhoenanthus youi (Wu & You, 1986), partial mis-identification].
Rhoenanthus hunanensis: Kluge 2004: 223.
Distribution: China (Hunan, Fig. 11).
Mature Nymph (in alcohol, Figs 2–4): body length 20.0 mm, antennae 6.0 mm, cerci 10.0–12.0 mm, terminal filament 12.0 mm. Body yellowish brown.
Head: Yellowish to pale brownish, compound eyes large, ecdysial line pale; distance between two compound eyes 3.0x diameter of eye (Fig. 2 A–B); antennae 3.0x head in length, basal yellowish and gradually pale, articulations with tiny hair-like setae (Fig. 2C).
Mouthparts: Labrum: 1/3 head width, hair-like setae on dorsal surface, anterior and lateral margins, those on anterior margin shorter and denser than marginal setae (Fig. 3A). Mandibular tusks approximately 2.0x head length, taper from base to apex, slightly bent inward; apical 3/4 brown, basal 1/4 pale, triangular, with scattered spine-like denticles and additional hair-like setae on outer margin (Figs 2 A–B, 3D–E). Hypopharynx: superlinguae extended into falcate lobe-like structure, lateral margins with sparse hair-like setae, and anterior margin with denser hair-like setae; lingua heart-shaped (Fig. 3B). Maxilla: apex of galea-lacinia with 2 large dentisetae and a tuft of brush-like setae anteriorly, those near dentisetae relatively denser and stouter than others; inner margin with a row of bristlelike setae, outer margin and cardo with hair-like setae; maxillary palpi 3-segmented, length ratio from proximal to apical 1.4: 0.9: 1.5; segment 1 subequal to galea-lacinia in length, with setae on outer margin; both inner and outer margins of segment 2 with scattered hair-like setae, segment 3 with scattered but longer hair-like setae on entire surface (Fig. 3F). Labium: paraglossae expanded laterally, with dense hair-like setae on both surface, those on free margins relatively longer and denser; surface of glossae with hair-like setae; labial palpi 3-segmented, length ratio from basal to distal 1.1: 0.6: 0.9, basal segment broader than others, with row of setae on outer margin and sparse tiny setae on inner margin; outer margin of segment 2 with row of sparser but longer hair-like setae; outer margin of segment 3 with longer hair-like setae than those on other segments, apically with rows of irregularly stout bristlelike setae on dorsal surface, and with scattered hair-like setae on ventral surface (Fig. 3C).
Thorax: pronotum extended laterally and forwards forming acute anterolateral corners, dorsal surface with irregularly pale and brown spots, with a dorsal semicircular ridge to interlock with head, anterior points of ridge extended into acute projections (Fig. 4I); Mesonotum and metanotum with some pale markings dorsally; wing pad brownish yellow (Fig. 2 A–B). Forelegs: coxa and trochanter with sparse hair-like setae on margins; length ratio of femora: tibiae: tarsi=2: 2.3: 1; femora yellowish, free margins and surface with sparse stout bristle-like and hair-like setae, those on inner margins denser and longer; dorsal surface of tibiae with rows of relatively long and sporadic setae, inner margin with additional row of spine-like setae apically; tarsi similar to tibiae in structure except those setae on free margins shorter and sparser but with more spine-like setae on inner margin (Figs 2A, 4A). Midlegs: coxae with sparse setae and an acute projection dorsally; length ratio of femora: tibiae: tarsi=2.8: 2.6: 1.0; femora wider and flatter than tibiae and tarsi, dorsal surface with sporadic spine-like setae, inner and outer margins with row of spine-like setae and scattered hair-like setae; tibiae with clear patellar-tibial fusion suture and an acute apical denticle, rows of hair-like setae and stout spine-like setae on whole surface of tibiae, those of ventral surface shorter; tarsi with hair-like setae on dorsal and free margins but those on margins much sparser and shorter than dorsal line (Figs 2A, 4D, 4G); Hindlegs slightly longer than midlegs with a slightly broader femora, length ratio of femora: tibiae: tarsi=3.6: 2.8: 1.0; setation patterns similar to midlegs except ventral surface of tibiae without setae while inner margin of femora with tuft of setae or villopore subapically (Fig. 4H). Claws of all legs similar, with dark hooked apex (Fig. 4B).
Abdomen: middle of terga I–X with an unconspicuously longitudinal pale stripe, lateral margins of terga with hair-like setae, posterolateral angles of tergum 9 slightly extended into sharp point; gills on terga I–VII, gill I much smaller than others, 2-segmented, with sparse hair-like setae (Fig. 4F); gills II–VII bifurcated into two fibrilliform lamellae; apex of them narrower than the bases, black tracheae visible (Figs 2A, 4C). Caudal filaments yellowish, with whorls of short hair-like setae on articulations and additional swimming setae on both sides (Fig. 2A).
Male imago (in alcohol, Figs 5 A–D, 6A–D): Body length 19.0 mm, antenna 1.5 mm, forewing 15.0 mm, hindwing 5.0 mm, cerci 21.0 mm, median terminal filament 7.0 mm. General color reddish to dark brown (Fig. 5).
Head: Head red to dark brown dorsally, distance between compound eyes less than diameter of one eye; basal part of compound eyes blackish but apical one gray. Ocelli with black basal band. Antennae pale yellowish (Fig. 5).
Thorax: pronotum with irregular purplish stripes and dots. Membranous areas between coxae and thorax enlarged, making prosternum extremely narrowed medially and with near X–shaped marginal ridges (Fig. 7A); median depression of mesothoracic furcasternum parallel (Fig. 7A). Forewings transparent, with purplish pigments on basal, costal and medial areas, MA forked near middle of wing (Fig. 6A). Apical half of hindwing purplish to reddish brown, costal projections acute; MP 2 connected to MP 1 near half length (Fig. 6B). Forelegs: purplish to brown, except tarsal segments II–IV and basal half of segment V; length ratio of femora: tibiae: tarsi=1.3: 1.7: 0.9; tarsal segment lengths in decreasing order=2, 5, 3, 4, 1. Midlegs: pale to yellowish, length ratio of femora: tibiae: tarsi=1.4: 1.5: 0.8; length of tarsal segments in decreasing order=4, 1, 2, 3. Hindlegs: length ratio of femora: tibiae: tarsi=1.6: 1.5: 0.3, other structures similar to midlegs. All legs with 2 claws, one sharp and one blunt.
Abdomen: overall purple to brown, each tergum with U-shaped dark brown stripes on dorsal surface, those stripes on terga II–VIII more pronounced; terga I–IX with pale longitudinal stripe medially and additional 2 pairs of pale droplet stripes submedially. Genitalia: forceps 3-segmented, length of basal segment 4.5x length of two terminal segments combined; penes brownish, Y-shaped (0.7x length of forceps), furcated beyond 1/3 of the subgenital plate; apex of penis tapered, genital pore in ventral position (Fig. 6 C–D). Caudal filaments with purplish base but others segments pale, surface with tiny setae; every five segments with purplish ring; terminal filament 1/4–1/3x cerci in length.
Male subimago (in alcohol): Body length 18.2 mm, forewing 14.0 mm, hindwing 4.0 mm; cerci 19.0 mm, median terminal filament 6.0 mm; General color purplish to brown; foretibiae slightly longer than forefemora, foretarsi 0.7x foretibiae length, tarsal segment lengths in decreasing order=2, 5, 3, 4, 1; other characters similar to male imago.
Female imago: Body length 29.0 mm, antenna 2.3 mm, forewing 26.0 mm, hindwing 4.0 mm; cerci 34.0 mm, median terminal filament 17.0 mm. General color reddish to brown.
Generally similar to male but with slightly paler color, especially wings and abdomen. Tibiae of forelegs slightly longer than femora, tarsi 0.4x of tibiae in length, tarsal segments lengths in decreasing order=2, 5, 3, 4, 1; Midlegs: pale, tibiae slightly longer than femora, length of tarsi 0.4x length of tibiae; length of tarsal segments in decreasing order as 4, 1, 2, 3; Hindlegs similar to midlegs. Subgenital plate (posterior sternum VII) semi-lunar lobe, posterior margin of sternum VIII thickened into a triangular lobe (Fig. 7B); subanal plate with a shallow median notch posteriorly (Fig. 7B). Terminal filament 1/3–1/2x cerci.
Egg (Fig. 8). Egg oblong with two polar caps, length ca 182 μm (including polar cap), width at equator ca 88μm, and chorionic surface with tiny tubercles, a round micropyle at equator and additional 6 round knob-terminated coiled threads (KCTs).
Materials examined: Holotype ♂, paratypes 2♂♂ 16♀♀, 3♂♂ subimagoes, 8L, Tongdao County, Hunan Province, collected by Jun ZHANG, Shusheng SHE, VI-1986; 5L, Dahe Port, Hongjiang City, Hunan Province, China, collected by Jun ZHANG, Shusheng SHE, VII-1985; 1♂ subimago, Chishui Alsophila National Nature Reserve, Chishui City, Guizhou Province, collected by Yanli DU, Huaijun XUE, 10-V-2000.
Diagnosis: This species can be distinguished from others in the same genus by the following features: in nymphs: 1) shape of mandibular tusks: relatively longer, straighter and slender; apical 2/3 brown, without setae, basal 1/3 triangular, pale, with spines and setae (Figs 2 A–B, 3D–E); 2) relatively longer foretibiae (clearly longer than forefemora, Figs 2A, 4A); 3) all surface of midtibiae with hair-like setae (Figs 2A, 4D, 4G); in adults: 1) segments II–IV and half base of segment V of foretarsi yellow to white (Fig. 5); 2) forewing and hindwing with numerous conspicuous large reddish to brown markings or dots (Fig. 6 A–B); 3) for male, penis lobes slightly longer than half basal segment of forceps, and genital pore on ventral side of penis (Fig. 6 C–D); 4) for female, subgenital plate pale, slightly round on posterior margin (Fig. 7B); 5) subanal plate shallowly notched on median posterior margin (Fig. 7B).
The nymph of this species is somewhat similar to those of R. magnificus and R. obscurus because of their smooth apical mandibular tusks (setae and spines on base only, Figs 2 A–B, 3D–E). But the latter two have distinctly broader inward tusks (Fig. 10G). The other three species (R. youi, R. coreanus and R. sapa) have spines on whole tusks (see Fig. 10A, 10D). The ventral surface of midtibiae of R. hunanensis has hair-like setae which is unique among the known species.
The male of R. hunanensis is close to that of R. youi because of penial shape and length, and color pattern on body and wings. However, the genital pores of this species open on the ventral surface of penes subapically (Fig. 6 C–D) while in R. youi, it opens apically. In addition, apex of R. hunanensis penis is sharp. In contrast, the apical genital pore of R. youi makes the apex of penis concaved or forked (Fig. 6 E–F).
Female adults of R. hunanensis and R. youi are very close and hard to differentiate. But the reddish brown stripes and markings on wings of the former species are slightly clearer, subgenital plate is more rounded, lateral extensions of terga VIII and IX are smaller, and the concave posterior margin of subanal plate is shallower than those of R. youi.
description: Published as part of Han, Na, Zhang, Min & Zhou, Chang-Fa, 2021, The genus Rhoenanthus Eaton, 1881 in China with the redescription of R hunanensis You & Gui, 1995 (Ephemeroptera: Potamanthidae), pp. 563-577 in Zootaxa 4903 (4) on pages 565-570, DOI: 10.11646/zootaxa.4903.4.5, http://zenodo.org/record/4434875