Choroterpes ( Afrochoroterpes ) nigrescens Barnard 1932

Kluge, Nikita J., 2025, Redescriptions of Choroterpes nigrescens Barnard 1932 and Ch. ndebele Agnew 1962 with notes about egg structure of Choroterpes Eaton 1881, Megaglena Peters & Edmunds 1970 and Klugephlebia Selvakumar et al. 2016 (Ephemeroptera, Leptophlebiidae), Zootaxa 5711 (2), pp. 203-222 : 205-211

Choroterpes ( Afrochoroterpes) nigrescens Barnard 1932

( Figs 1–10 , 20–21 , 28–35 , 43–56 , 75 , 76–80 , 84–89 )

Choroterpes nigrescens Barnard 1932: 248 ( ♂ & ♀ imago, larva); Agnew 1962: figs 4c, d ( ♂ imago, larva).

Choroterpes ( Choroterpes) nigrescens : Peters & Edmunds 1964: figs 13–14, 78, 96, 105, 115, 132–134 ( ♂ imago, larva); Peters & Edmunds 1979: figs 38–39 (imago); Kluge 2022: 178 (subimago).

Material examined. SOUTH AFRICA, Western Cape province: Wolwekloof river near falling into Witte river ( Bain’s Kloof ), Tweede Tol campsite, 33°34ʹS, 19°08ʹE, 20–22.I.2019, coll. N. Kluge & L. Sheyko: 2 L-S-I ♂ , 5 L-S-I ♀, 11 S-I ♂, 2 S-I ♀, 112 larvae; Wolfkloof, Keurbooms river ( 8 km WNW Swellendam ), 33°59ʹS, 20°22ʹ30ʹʹE, 25–26.I.2019, coll. N. Kluge & L. Sheyko: 2 L-S-I ♂ , 1 L-S ♂, 2 S-I ♂, 2 S-I ♀, 20 larvae; Homtini river (1.5 km NW Rheenendal , 15 km NW Knysna), 31.I–1.II.2019, coll. N. Kluge & L. Sheyko: 10 larvae .

Larva. CUTICULAR COLORATION. Head brown. Pronotum and mesonotum brown with few lighter areas ( Fig. 1 ). Thoracic pleura ochre-brown, sterna colorless. Legs ochre-brownish, each femur with diffusive longitudinal lighter area; on femur of fore leg, lighter area wider in proximal part ( Figs 3–5 ). Abdominal terga either uniformly light brownish-ochre, or with diffusive lighter and darker areas evenly repeated on terga II–IX; sterna lighter ochre ( Fig. 2 ).

HYPODERMAL COLORATION. Head and thorax with brown markings. Femur of each leg with more or less expressed longitudinal brown macula at middle and transverse brown macula near apex ( Fig. 8 ). Abdominal terga with extensive brown maculae (as in imago— Figs 6–7 ).

SHAPE AND SETATION. Labrum with very deep median emargination; due to this, distal transverse setal row sharply bent V-like, proximal transverse setal row less sharply bent V-like ( Fig. 20 ). Mandibles with outer margin very convex ( Fig. 21 ).

Stout setae on anterior side of all femora few and small ( Fig. 28 ). Arched pectinate setae near inner margin of posterior side of hind femur relatively small ( Fig. 29 ). Inner side of middle tibia without pectinate setae ( Fig. 31 ). Pectinate setae on hind tibia few, small and located on posterior side only ( Fig. 33 ); anterior side of hind tibia with row of stout, non-pectinate setae ( Fig. 32 ).

Posterior margins of abdominal terga I–VIII with very small, pointed denticles ( Fig. 34 ); terga IX–X with larger pointed denticles ( Fig. 35 ). Abdominal sterna without denticles. In male larva, posterior margin between protogonostyli concave; protopenes short ( Fig. 80 ).

Winged stages. In both sexes, hind wing with blunt costal projection and reduced apical part, so that wing apex locates between ends of RSa and RSp, and margin between apex of costal projection and wing apex straight or convex ( Fig. 75 ; Barnard 1932: fig. 38b; Peters & Edmunds 1964: fig. 13; Peters & Edmunds 1970: fig. 39).

Subimago. CUTICULAR COLORATION. Head with colorless and light ochre-brown areas; flagellum of antenna brown. Pronotum ochre-brown. Mesonotum with lighter and darker ochre-brown areas: medioscutum with achromozone light ochre-brownish, chromozone only slightly darker ( Fig. 79 ). Thoracic pleura and sterna with ochre-brown and colorless areas. Wings colorless, with microtrichiae dark brown. Legs uniformly ochre-brown. Abdominal terga and sterna uniformly ochre-brown, sigilla of same color. Medio-posterior area of styliger lighter ( Fig. 77 ). Caudalii uniformly ochre-brownish.

HYPODERMAL COLORATION. As in imago: each femur with large brown maculae at middle and at tip (as in Figs 9–10 ); abdominal terga with brown and ochre maculation (as in Figs 6–7 ).

TEXTURE. On legs of all pairs of both sexes, 1st–4th tarsomere covered with microtrichia (as tibia), 5th tarsomere covered with very sharply pointed microlepides similar to microtrichia (Kluge 2022: table 15).

Imago, male. Head brown. Dorsal eyes dull reddish-brown. Thorax brown, equally dark on dorsal, lateral and ventral sides; membranous areas of lateral side whitish. Fore and hind wings with membrane translucent, from colorless to ochre-brownish, veins brown ( Fig. 75 ). Legs ochre-brown, with large darker brown maculae at middle and tip of femur; fore legs darker than middle and hind legs ( Figs 9–10 ). Abdominal terga with brown and ochre maculation ( Fig. 6 ). Genitalia— Figs 76, 78 . Caudalii brown (cuticular coloration) with segment joinings narrowly bordered by dark brown (hypodermal coloration).

Imago, female. Head and thorax lighter than in male, ochre with brown. Coloration of wings, legs and abdomen as in male ( Fig. 7 ).

Egg ( Figs 84–89 ). Elongate and narrowed, spindle-shaped, without polar caps, without papillae and vesicles. Under scan electron microscope (SEM), egg looks as having deep longitudinal grooves running from one pole to another ( Fig. 84 ). Chorion is armed with longitudinal ladder-like structures, each formed by a pair of straight, rigid rods connected by short, fine anastomoses ( Fig. 85 ); the anastomoses are hidden in the longitudinal grooves between the rods and not visible under SEM. All rods are well visible both in glycerin and Canadian balsam, but anastomoses are visible in glycerin and invisible in Canadian balsam.

Dimension. Fore wing length (and approximate body length) 7–8 mm.

Comments. Barnard (1932) described and figured abdominal color of larva as having contrasting pale spots on dark brownish background ( Barnard 1932: fig. 38c and p. 249). Actually, this is the hypodermal coloration, the same as in imago and subimago ( Figs 6–7 ); larval abdominal cuticle of this species is either unicolor pale ochre lacking any markings, or with pale areas different from hypodermal ones ( Fig. 2 ).

Figures

FIGURES 1–10. Choroterpes (Afrochoroterpes) nigrescens. 1–5, larval exuviae (1, half of pronotum and mesonotum; 2, abdomen; 3–5, fore, middle and hind legs); 6, abdomen of male imago; 7, abdomen of female imago; 8, larva; 9–10, fore and hind legs of male imago.

FIGURES 20–27. Larval mouthparts. 20–21, Choroterpes (Afrochoroterpes) nigrescens (20, labrum; 21, left mandible); 22–27, Choroterpes (Afrochoroterpes) ndebele (22–24, labrum; 25, left mandible; 26, maxilla; 27, labium).

FIGURES 28–35. Choroterpes (Afrochoroterpes) nigrescens, larval exuviae. 28, hind femur, focus on anterior side; 29, the same, focus on posterior side; 30–32, fore, middle and hind tibiae, focus on anterior side; 33, hind tibia, focus on posterior side; 34–35, posterior margins of abdominal terga V and IX.

FIGURES 43–56. Choroterpes (Afrochoroterpes) nigrescens. 43–49 and 50–56, tergalii of I–VII pairs of two individuals.

FIGURES 71–75. Wings. 71–74, Choroterpes (Afrochoroterpes) ndebele: 71–72, fore and hind wings of male imago; 73, enlarged hind wing; 74, hind wing of female developing in larval protopteron; 75, Choroterpes (Afrochoroterpes) nigrescens, hind wing of male imago.

FIGURES 76–83. 76–80, Choroterpes (Afrochoroterpes) nigrescens: 76, genitalia of male imago; 77, subimaginal exuviae of genitalia; 78, penis of male imago; 79, subimaginal exuviae of right half of mesonotum; 80, larval exuviae of protogonostyli and protopenis; 81–83, Choroterpes (Afrochoroterpes) ndebele: 81, genitalia of male imago; 82, penis of male imago; 83, larval exuviae of protogonostyli and protopenis. Abbreviations: acz, achromozones of medioscutum and submedioscutum; cz, chromozones of medioscutum and submedioscutum.

FIGURES 84–89. Eggs of Choroterpes (Afrochoroterpes) nigrescens. 84, under scanning electron microscope; 85–89, after treating by lactic acid, in transmitted light in glycerin: 85, detached chorion; 86, optic section; 87–89, surface view.