Labiobaetis pulchellus ( Müller-Liebenau & Hubbard, 1985 )

Kluge, Nikita, Sivaruban, T., Srinivasan, Pandiarajan, Barathy, S. & Isack, Rajasekaran, 2023, Diagnosis, variability, distribution and systematic position of Labiobaetis pulchellus (Müller-Liebenau & Hubbard 1985) (Ephemeroptera, Baetidae, Baetis s. l.), Zootaxa 5264 (1), pp. 94-108 : 96-106

Labiobaetis pulchellus ( Müller-Liebenau & Hubbard, 1985)

( Figs 1–64 )

Baetis pulchellus Müller-Liebenau & Hubbard 1985: 544 (larva).

Baetis (Mullerbaetis) pulchellus: Kang & Chang & Yang 1994 .

Labiobaetis pulchellus: McCafferty & Waltz 1995: 21 ; Kluge 2022: 163 (subimago).

Pseudocloeon pulchellum: Lugo-Ortiz, McCafferty & Waltz 1999: 25 .

Labiobaetis soldani Kubendran, Rathinakumar, Balasubramanian, Selvakumar & Sivaramakrishnan 2014: 2 (larva, J & ♀ imago).

Material examined. 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: 1 L-S-IJ, 1 L-SJ, 2 L-S-I ♀ ( ZIN); Central province, Ginigathhena (17 km N Hatton), 31.I–3.II.2011, coll. N. Kluge & L. Sheyko: L/S ♀ ( ZIN); Sabaragamuwa Province, Dalhausie near Sri Pada ( Adam's Peak ), river Seetha Gangula , 6.II.2020, coll. N. Kluge & L. Sheyko: 1 L-S-IJ ( ZIN).

INDIA: Karnataka state, Udupi district, river Seethanadi near Someswar, 31.II.2013, coll. N. Kluge & L. Sheyko: 1 L-S-IJ ( ZIN); Kerala state, Kottayam district, Erumeli , 18–21.I.2016, coll. N. Kluge & L. Sheyko: 2 L /SJ ( ZIN); Tamil Nadu state, Madurai, river Vaigai , 10.II.2016, coll. N. Kluge & L. Sheyko: 1 S-IJ, 1 S-I ♀ ( ZIN); the same locality, 12.XII.2022, coll. P. Srinivasan & R. Isack: 1 L-S-IJ, 1 SJ, 1 S ♀, 3 LJ, 2 L ♀ ( AMC); Dindigul, Kodaikanal hills, Mangalamkombu stream , 16.II.2020, coll. P. Srinivasan & R. Isack: 2 LJ ( AMC); Theni, Suruli falls , 13.XI.2021, coll. P. Srinivasan & R. Isack: 4 LJ ( AMC).

Additional descriptions

Larva. CUTICULAR COLORATION: Head from brown with colorless blanks ( Fig. 1 ) to light ochre. Pronotum from brown to ochre, with lighter ovoid sigilla; mesonotum from brown with colorless blanks to ochre with lighter and darker areas; fore protopteron from brown to ochre with indistinct lighter striation along longitudinal veins ( Figs 3, 6, 9 ). Metanotum, thoracic pleura and certain areas of thoracic sterna from contrastingly colored with brown ( Fig. 2 ) to nearly colorless. Legs mostly ochre or colorless; each femur at midlength with brown macula adjacent to inner margin; with ( Figs 2 , 27 ) or without ( Fig. 5 ) contrasting brown macula at base. Tibia with brown apex of outer side; tarsus with brown apex of outer side ( Figs 2, 5 , 27 ). Abdominal terga from brown with contrasting blanks to pale ochre with diffusive blanks; submedian sigilla lighter than background; terga I–IX either all with uniform color pattern ( Figs 10, 12 ; Müller-Liebenau & Hubbard 1985: fig. 15; Kubendran et al. 2014: figs 1–4), or differentiated, with different median blanks on different segments; in this case, tergum V always lighter than others or with largest unpaired median blank ( Figs 4, 7, 11 ). Abdominal sterna from nearly colorless ( Fig. 10 ) to brown with lighter submedian sigilla and colorless median blank adjacent to posterior margin ( Figs 4, 7 ). Caudalii light, with brown band just distad of midlength ( Figs 4, 8, 11, 12 ).

Both forms of abdominal coloration, i.e. with the 5th tergum lightest ( Figs 4, 7, 11 ) and with all terga uniformly colored ( Figs 10, 12 ) are found among larvae both from Sri Lanka and from India. Among 20 larval specimens examined, 15 male larvae have contrasting coloration with 5th tergum lightest ( Figs 4, 7, 11 ), and only one reared male specimen from Sri Pada has larval terga uniformly colored (as in Kubendran et al. 2014: fig. 1); all 4 female larvae have abdominal terga uniformly colored ( Figs 10, 12 ).

HYPODERMAL COLORATION: Not expressed.

SHAPE AND SETATION: Described by Müller-Liebenau & Hubbard (1985) and Kubendran et al. (2014). Frons between antennae narrow, but non-carinate ( Fig. 61 ). Scape with distolateral process ( Müller-Liebenau & Hubbard 1985: fig. 6d). Labrum dorsally with long, fine, simple setae scattered over surface; submarginal arc of setae composed of 1 + 3 long, simple setae, the first two setae after the central seta closely together ( Fig. 13 ). Left mandible between prostheca and mola slightly convex, with minute denticles toward mola; mola without apical tuft of setae; right mandible between prostheca and mola convex; mola with apical tuft of setae ( Figs 14–15 ; MüllerLiebenau & Hubbard 1985: fig. 6e). Hypopharynx with medial tuft of stout setae well developed and short ( Fig. 17 ). Maxillary palp with distal excavation of inner margin ( Fig. 18 ; Müller-Liebenau & Hubbard 1985: fig. 6g). Labium with paraglossae wide, with apical setae forming three rows; labial palp with broad distomedial protuberance of 2nd segment and conical 3rd segment ( Fig. 16 ; Müller-Liebenau & Hubbard 1985: figs 6b–c).

Hind protoptera present, in female somewhat smaller than in male ( Figs 19, 21, 23, 25 ).

Legs of all three pairs: Outer side of femur with row of long, stout, blunt setae ( Fig. 28 ) and two such apical setae; apex with short, stout, spatulate setae. Inner side of femur with pointed, lanceolate setae ( Fig. 29 ). Femoral patch (villopore) present on middle and hind legs, vestigial or absent on fore legs. Outer side of tibia with short, blunt, spatulate, stout setae; on apex one longer, blunt, spatulate seta; inner side of tibia with stout, pointed setae ( Fig. 30 ; Müller-Liebenau & Hubbard 1985: fig. 6h). Outer side of tarsus with blunt, stout setae smaller than on tibia. Claw without subapical setae ( Müller-Liebenau & Hubbard 1985: fig. 6i).

All abdominal terga I–X with denticles on posterior margin; denticles on anterior terga smaller and blunt ( Fig. 31 ), denticles on posterior terga larger and pointed ( Fig. 32 ); on tergum IX denticles behind bases of submedian setae smaller of absent ( Fig. 33 ). Abdominal sterna I– VI without denticles; sterna VII–VIII with few spaced, wide, triangular denticles ( Figs 34–35 ); sternum IX with pointed denticles; in male row of denticles interrupted by protogonostyli ( Fig. 36 ). Paraproct with pointed denticles increasing distally ( Müller-Liebenau & Hubbard 1985: fig. 6j). All 7 pairs of tergalii present, tergalii of 1st pair smaller than others ( Fig. 4 ).

Subimago. CUTICULAR COLORATION: Mostly light brownish ( Figs 37–43 ).

HYPODERMAL COLORATION: As in imago.

TEXTURE: On all legs of both sexes, last tarsal segment covered with pointed microlepides; other tarsomeres covered mostly with blunt microlepides, with few pointed microlepides on distal margin ( Figs 38–40 ) ( Kluge 2022).

Imago, male ( Figs 44–50 ). Head brown. Turbinate eyes from red to yellow, widened distally. Thorax dark brown. Fore wing with membrane colorless, veins ochre. Pterostigma with incomplete oblique veins connected with costal vein, but not with subcostal vein. Hind wing narrow, without costal projection, with 2 longitudinal veins ( Figs 20, 22, 24 ). Legs of all pairs ochre, either with red-brown band near apex of femur ( Figs 52–53 ), or without it ( Figs 54–55 ). Middle and hind tarsi with 2 apical spines (on 1st+2nd and 3rd segments). Abdominal terga and sterna mostly ochre or whitish; each tergum II, IV and VI with small brown or reddish spot at midline near fore margin, either without other coloration ( Figs 44, 48 ) or with red area by sides and behind spot ( Figs 45–47, 49–50 ; Kubendran et al. 2014: fig. 18); terga I, III and V lack this spot and red area.

Gonostyli with 1st segment parallel-sided, with prominent rectangular apical-inner angle; 2nd segment narrow in proximal part and wider in distal part; 3rd segment short and roundish, sharply separated ( Figs 56–60 ). Penial bridge projected caudally forming pair of rounded lobes with deep concavity between them, with sharply pointed, sclerotized denticle arising from middle of this concavity; gonovectes sharply bent ( Figs 56, 57, 60 ).

Imago, female ( Fig. 51 ). Head, thorax and abdomen ochre with brown. All tarsi with 2 apical spines (fore tarsus on 2nd and 3rd segments, middle and hind tarsi on 1st+2nd and 3rd segments). Wings as in male; hind wing smaller ( Fig. 26 ).

Egg. Widely oval; chorion smooth, without regular relief; one pole surrounded by fine, narrow, ring-form groove, with or without few indistinct, shallow protuberances just outside groove ( Figs 62–64 ).

Dimension. Fore wing length 4 mm.

Distribution. Southern India and Sri Lanka.

Synonymy of L. soldani . According to the original description, Labiobaetis soldani differs from L. pulchellus by the following characters ( Kubendran et al. 2014: table 1):

Submarginal bristles on labrum: «feathery» in L. soldani , «fine» in L. pulchellus . According to the original description of L. pulchellus «submarginal fine bristles single (not in a dense row)»; here the term «submarginal bristles», refers to the setae located at a distance from the distal margin and present on the drawing, on which the marginal feathery setae are not drawn ( Müller-Liebenau & Hubbard 1985: fig. 6a). According to the original description of L. soldani , its labrum «with an arc and stout setae, long and thin setae medially; distal margin bordered with setae, distolaterally 14 feathered bristles; ventrally with 4 stout, 2 long setae and distomedial arc of very thin setae». On the drawing ( Kubendran et al. 2014: fig. 8), both dorsal and ventral sides of the labrum are drawn together, and the marginal feathery setae are present as well. So different setae are reported as «submarginal bristles» in the comparison of L. soldani and L. pulchellus .

Ratio of paraglossae to glossae in width: «1.8x» in L. soldani , «2x» in L. pulchellus . This difference is less than the possible accuracy of paraglossa measurement.

Apex of labial palp: «slightly pointed» in L. soldani , «pointed» in L. pulchellus . Judging by the original drawings ( Müller-Liebenau & Hubbard 1985: fig. 6b; Kubendran et al. 2014: fig. 13) difference between left and right palps can be greater than between the individuals attributed to these two species.

Hind wing (and hind protopteron of larva): «absent» in L. soldani , «well developed» in L. pulchellus . Actually, the presence of hind wings in L. soldani was overlooked (Kubendran, personal communication).

Pointed setae on the margin of femur: «6» in L. soldani , «8» in L. pulchellus . Such variability is found on different legs of one and the same individual.

Thus, no one species-specific character separating L. soldani from L. pulchellus has been reported. The unusual coloration of male imaginal abdomen, with alternating colored even segments II, IV and VI and colorless odd segments I, III and V testifies that the form described as L. soldani from India is conspecific to L. pulchellus originally described from Sri Lanka.

Figures

FIGURES 1–12. Labiobaetis pulchellus, larva. 1–10, larval exuviae: 1, head; 2, 5, thorax with legs; 3, 6, 9, half of pronotum and mesonotum; 4, 7–8, 10, abdomen and caudalii (1–4, specimen from Karnataka, India; 5–8 and 9–10, two specimens from Sri Lanka; 11–12, larvae from India).

FIGURES 13–16. Labiobaetis pulchellus, larva. 13, labrum; 14–15, left and right mandibles; 16, labium. Abbreviations: a–d, submarginal arc of setae (a, central seta; b–c, first two setae after central seta); ats, apical tuft of setae on mola).

FIGURES 17–26. Labiobaetis pulchellus. 17, hypopharynx with superlingua; 18, maxilla; 19–26, half of larval metathorax with hind protopteron and hind wing of the same individual with the same magnification: 19–20 and 21–22, two males from India; 23–24, male from Sri Lanka; 25–26, female from Sri Lanka.

FIGURES 27–36. Labiobaetis pulchellus, larval exuviae. 27, fore leg; 28, outer side of its femur; 29, inner side of its femur; 30, its tibia; 31–36, posterior margins of male abdominal terga and sterna: 31, tergum III; 32, tergum VIII; 33, tergum IX; 34, sternum VII; 35, sternum VIII; 36, sternum IX.

FIGURES 37–43. Labiobaetis pulchellus, subimaginal exuviae of specimen from Madurai (India). 37, fore leg; 38–39, tibiae and tarsi of fore and middle legs; 40, microlepides on fore tarsus; 41, abdominal terga; 42, genitalia; 43, half of mesonotum.

FIGURES 44–55. Labiobaetis pulchellus, imagines. 44–47, males; 48–50, male abdomina; 51, female; 52, 54, male fore legs; 53, 55, hind legs (44, reared specimen from Madurai; 48, 54–55, non-reared specimen from Madurai; 45, 47, reared specimen from Sri Pada; 49 and 51, two reared specimens from Uma; 46, 59, 53, 53, reared specimen from Karnataka).

FIGURES 56–60. Labiobaetis pulchellus, genitalia of male imagines (56, non-reared specimen from Madurai; 57, reared specimen from Uva; 58–59, reared specimen from Madurai; 60, reared specimen from Karnataka).

FIGURES 61–67. 61–64, Labiobaetis pulchellus: 61, head of larva; 62–64, eggs (extracted from imago, Sri Lanka). 65, eggs of Labiobaetis calcaratus (from Lithuania, river Neris near Vilnius, 15.VIII.1988, coll. N. Kluge); 66, eggs of Labiobaetis tricolor (the same locality, date and collector); 67, eggs of Labiobaetis propinquus (from USA, Maine, 9.VIII.1992, coll. N. Kluge).