Baetis (Tenuibaetis) frequentus Muller-Liebenau & Hubbard 1985
Creators: name: Kluge, Nikita
name: Srinivasan, Pandiarajan
name: Sivaruban, T.
name: Barathy, S.
name: Isack, Rajasekaran
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Ephemeroptera
Baetidae
Baetis
Baetis frequentus

description: 3. Baetis (Tenuibaetis) frequentus Müller-Liebenau & Hubbard 1985
(Figs 5–14, 60–124)
Baetis frequentus Müller-Liebenau & Hubbard 1985: 539 (larva).
Indobaetis michaelohubbardi Selva-kumar, Sundar, & Sivaramakrishnan 2012: 127 (larva), syn.n.
Baetis (Tenuibaetis) michaelohubbardi: Kluge & Novikova 2014: 215.
Material examined (ZIN). INDIA: Tamil Nadu state, Palni Hills near Kodaikanal, Levinge stream downstream of Pamparpuram, 29.I–3.II.2016, coll. N. Kluge & L. Sheyko: 1 L-S-I♁, 1 L-S-I ♀, 24 larvae; river Palar downstream Perumal Malai, 5.II.2016, coll. N. Kluge & L. Sheyko: 1 L-S♁, 8 larvae.
SRI LANKA: boundary between Uva province and Central province, tributary of river Uma near Randenigala dam, 14–15.I.2011, coll. N. Kluge & L. Sheyko: 3 L-S-I♁; Uva province, Badulla district, Haputale Forest and river Lemastota Oya, 15–23.I.2011, coll. N. Kluge & L. Sheyko: 12 L-S-I♁, 3 L-S♁, 8 L-S-I ♀, 3 L-S ♀, 68 larvae; Sabaragamuwa Province, Ratnapura District, Belihuloya, river Belihul oya and Kirikatu oya, 15–26.I.2020, coll. N. Kluge & L. Sheyko: 2 larvae; Sabaragamuwa Province, Dalhausie near Sri Pada (Adam’s Peak), river Seetha Gangula, 2–10. II.2020, coll. N. Kluge & L. Sheyko: 3 L-S-I♁, 2 L-S-I ♀, 1 L-S ♀, 15 larvae; south-eastern slope of Sri Pada, river Battulu Oya, Fishing Hut, 8–9. II.2020, coll. N. Kluge & L. Sheyko: 3 larvae.
Descriptions
Larva. CUTICULAR COLORATION: (Figs 60–74): Head brown (Fig. 69). Pronotum brown to brown with blanks, with sigilla either of same color as background, or lighter than background, or darker than background; mesonotum and fore protoptera brown, with more or less contrasting blanks (Figs 63–68, 74). Thoracic pleura brownish, sterna colorless. Legs vary from brown with blanks (Fig. 64) to mostly colorless with brown maculae (Fig. 68); if fore femur dark with expressed proximal blank, shape of proximal blank subtriangular or comma-like, with inner-distal angle stretched distally (Fig. 75). Abdominal terga vary from nearly uniformly brown to more or less contrasting; tergum IV either nearly as dark as others (Fig. 64), or colorless laterally (Fig. 66). Caudalii uniformly brown.
HYPODERMAL COLORATION: Either not expressed, or abdominal terga with dark brown line on posterior margin and other markings as in imago (as in Figs 92, 94, 97, 100. 103, 110).
SHAPE AND SETATION: Labrum of medium proportions (Figs 80–81; Müller-Liebenau & Hubbard 1985: fig. 1a). Mandibles as in original description (Figs 78–79; Müller-Liebenau & Hubbard 1985: 539, fig. 1e). Labial glossae, paraglossae and palp as in original description (Fig. 82; Müller-Liebenau & Hubbard 1985: fig. 1b–c).
Hind protoptera present (Fig. 14; Müller-Liebenau & Hubbard 1985: 1 f).
Stout two-channel setae forming row along outer side of femur (including two subapical setae) elongate, blunt, distally widened, flattened and twisted (Figs 90–91). Distal part of outer side of femur and anterior-apical margin of femur with small, pseudo-bifurcate setae, as on tibiae (Figs 89–91). Anterior side of femur with colorless oval scales in semicircular sockets (Figs 88, 91) (as on abdomen). Stout setae on anterior side of femur varying from long to short and from two-channel to pseudo-bifurcate, being different in different populations and individuals (see below) (Figs 83–88).
Tibia of each leg with pseudo-bifurcate setae on outer side and along patella-tibial suture (Figs 5–11, 89).
Denticles on posterior margins of terga vary from triangular (Fig. 76; Müller-Liebenau & Hubbard 1985: fig. 18) to blunt (Fig. 77); absent or sparse on tergum I, sometimes also on tergum II. Denticles on posterior margin of sternum triangular, present only on sternum IX, sometimes also on sternum VIII; in male row of denticles not interrupted by protogonostyli. Paraproct with small denticles (Müller-Liebenau & Hubbard 1985: fig. 1h). Tergalii with oval scales in semicircular sockets. Tergalius I much smaller than others (Fig. 73; Müller-Liebenau & Hubbard 1985: fig. 1j). Paracercus significantly smaller than cerci (Müller-Liebenau & Hubbard 1985: fig. 1i).
Subimago. CUTICULAR COLORATION: Head colorless, antennae brown. Pronotum with light brown and colorless areas. Mesonotum with ochre, light brownish and dark brown areas (Fig. 104). Thoracic pleura and sterna with light brownish and dark brown areas (as in Fig. 215). Legs brownish (Figs 107–108). Abdominal terga light brownish; terga IX –X either as dark as others, or lighter.
HYPODERMAL COLORATION: As in imago.
Imago, male (Figs 92–103, 105–106). Head ochre.Antennae ochre.Turbinate eyes with facetted surface varying from red (Fig. 94) to ochre bordered with brownish (Figs 96, 102); stem varying from reddish to ochre or whitish. Thorax from brown (Fig. 94) to ochre with light brown (Fig. 102). Forewing with membrane entirely colorless; veins from ochre (nearer to wing base) to brown; pterostigma with few oblique cross veins and disconnected vein fragments (Fig. 102). Hind wing full-sized, colorless, with short and non-hooked costal projection, with 2 longitudinal veins (Figs 13, 109). Legs either uniformly ochre, or with diffusive reddish markings (Figs 93, 95, 99, 105–106). Middle and hind tarsi with 2 apical spines (on 1st+2nd and 3rd segments). Abdominal terga and sterna ochre with brownish or reddish, with lateral areas darker and median areas lighter; terga IX –X lighter than others; terga I– IX or some of them either with contrastingly dark brown band bordering posterior margin and not reaching lateral margins (Fig. 103), or without such bands. Cerci ochre or light brown. Gonostyli light brown; 1st segment relatively narrow, only slightly narrowing toward apex (nearly parallel-sided); 3rd (terminal) segment short and petiolate (Figs 98, 101, 112). Gonovectes gently bent, light brownish. Sterno-styligeral muscle either vestigial (Fig. 115), or absent (Fig. 98).
Imago, female (Fig. 110). Coloration similar to that of male. Hind wing as in male or slightly narrower (Fig. 111). All tarsi with 2 apical spines (fore tarsus on 2nd and 3rd segments, middle and hind tarsi on 1st+2nd and 3rd segments).
Dimension. Forewing length of male 3.5–4.5 mm, of female 5–6 mm.
Distribution. Southern India and Sri Lanka.
Variability. Stout setae on anterior side of femur vary from long to short and from two-channel to pseudo-bifurcate. In some Ceylonese individuals from Sri Pada all these setae are long, clavate and clearly two-channel (Figs 84–86), as on the drawing in the original description (Müller-Liebenau & Hubbard 1985: fig. 1g). Some individuals from the same locality have these setae short and pseudo-bifurcate; some individuals have mixture of various setae, both long and short, both two-channel and pseudo-bifurcate with branched walls inside (Fig. 83). In Ceylonese individuals from Haputale and Uma these setae are mostly short, varying from two-channel to pseudo-bifurcate (Figs 87–88). The Indian individuals from Levinge stream also have these setae short, mostly pseudo-bifurcate (Figs 75).
Larval cuticular coloration greatly varies among Ceylonese individuals, even from one locality (Figs 60–68). Indian individuals from Levinge stream have less variable coloration, nearly uniformly brown (Figs 69–75).
Coloration of male imagines and shape of fore femur vary among Ceylonese individuals as in the Figs 93–101.
Comments. Originally, Baetis (Tenuibaetis) frequentus was described from Sri Lanka. Sivaramakrishnan & Venkataraman (1990), Balaji et al. 1990 and Selvakumar et al. 2012 reported this species from southern India, but it is unclear if they determined it correctly or not. As proceeds from the original description, B. (T.) frequentus differs from other species by the pseudo-bifurcate setae on outer sides of tibia and neighboring areas of femur and tarsus (Müller-Liebenau & Hubbard 1985). Kubendran et al. (2015) described larvae and imagines from Tamil Nadu state in India, which they determined as ́Tenuibaetis frequentus ». Judging by the drawings (Kubendran et al. 2015: figs 10–11), thick setae on outer side of larval tibia and tarsus are stout, pointed and look integral in transmission light, but not pseudo-bifurcate; so these larvae cannot belong to B. (T.) frequentus. Male imagines described as ́Tenuibaetis frequentus » were not reared from larvae, and their belonging to the same species is not proven.
Synonymy of B. michaelohubbardi. Selva-kumar, Sundar and Sivaramakrishnan (2012) described larvae from southern India under the name Indobaetis michaelohubbardi Selva-kumar et al. 2012. This description contained significant errors, because of which the species was wrongly attributed to the genus Indobaetis Müller-Liebenau & Morihara, 1982. Kluge and Novikova (2014) transferred it in the subgenus Tenuibaetis of the genus Baetis. According to the original description of B. (T.) michaelohubbardi, its ́hindwing pads absent» (Selva-kumar et al. 2012: 127). Later K.G. Sivaramakrishnan (personal communication) reported that actually the type specimens have hind protoptera (Kluge & Novikova 2014: 215). Recently, C. Selvakumar kindly provided us with photos of the holotype of this species (Figs 116–124). Judging by them, it is conspecific with B. (T.) frequentus.
description: Published as part of Kluge, Nikita, Srinivasan, Pandiarajan, Sivaruban, T., Barathy, S. & Isack, Rajasekaran, 2023, Contribution to the knowledge of the subgenus Tenuibaetis Kang & Yang 1994 (Ephemeroptera, Baetidae, Baetis s. l.), pp. 201-258 in Zootaxa 5277 (2) on pages 217-226, DOI: 10.11646/zootaxa.5277.2.1, http://zenodo.org/record/7889695