Choroterpes 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 : 215-217

Differences between Ch. nigrescens and Ch. ndebele

These two South African species are similar in general appearance of larvae, subimago and imago and most reliably differs by the following characters:

In larva: Labrum in Ch. ndebele has usual shape ( Figs 22–24 ), in Ch. nigrescens —with unusually deep median incision ( Fig. 20 ). Other larval characters distinguishing these species are setation of legs, denticles on abdominal terga and shape of sternum IX in male (see above).

In winged stages (subimago and imago of any sex): Hind wing in Ch. ndebele has usual shape ( Fig. 73 ), in Ch. nigrescens —with unusually reduced apical part ( Fig. 75 ).

In male imago (besides hind wing structure), Ch. ndebele and Ch. nigrescens differ by structure of penis ( Figs 78 and 82 ).

In female subimago and imago (besides hind wing structure): Egg of Ch. ndebele has two polar caps consisted of large papillae pressed together; hidden longitudinal rods are undulate, with a row of vesicles between rods of each pair ( Figs 90–98 ). Egg of Ch. nigrescens has no polar caps; its hidden rods are straight, and vesicles are absent ( Figs 84–89 ). Eggs of these two species can be distinguished using light microscope.

Figures

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 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 90–98. Eggs of Choroterpes (Afrochoroterpes) ndebele. 90–91, under scanning electron microscope; 92–98, after treating by lactic acid, in transmitted light: 92, detached chorion in Canadian balsam; 93–96, one and the same fragment of chorion: 93–94, in Canadian balsam, focus on external and internal sides; 95–96, in glycerin, focus on external and internal sides; 97, optic section in glycerin; 98, surface view in glycerin. Abbreviations: pap, papilla; ves, vesicle.

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.