Labiobaetis tricolor (Tshernova, 1928)

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 : 95-96

Group tricolor

( Figs 1–60 )

Group tricolor: Kluge 1997: 189 .

Name of the group. Among species included in this group, Labiobaetis propinquus ( Walsh, 1863) has a name older than Labiobaetis tricolor ( Tshernova, 1928) . However, this group is not named « propinquus group», but « tricolor group» to avoid confusion with the « propinquus group» proposed by Morihara & McCafferty (1979a; 1979b) for all Labiobaetis .

Larval characters

Antenna: scape with distolateral process. The same in some other Labiobaetis , including the type species, L. atrebatinus . For the species lacking this process, a separate genus Cymulabaetis McCafferty & Waltz, 1995 was established, but at present it is not accepted ( Lugo-Ortiz & McCafferty 1997).

Labrum: setae forming submarginal arc are simple and sparse; the first two setae after the central seta are closely together ( Fig. 13 ). This character is known for L. tricolor (illustrated in Ikonomov 1962: fig. 13:1), L. propinquus (illustrated in Morihara & McCafferty 1979a: fig. 11; 1979b: fig. 30b), L. calcaratus ( Keffermüller, 1972) (personal observation by Kluge) and L. pulchellus (illustrated in Müller-Liebenau & Hubbard 1985: fig. 6a). The same in some other species groups, but in contrast to some other Labiobaetis (including the type species, L. atrebatinus ), which have the submarginal setal arc consisted of other kinds of setae (e.g. feathered, lanceolate, or spatulate), or consisted of simple setae, but without two setae brought together.

Hypopharynx: medial tuft of stout setae well developed and short ( Fig. 17 ).

Maxillary palp: distal excavation of inner margin present ( Fig. 18 ).

Labium: Paraglossae wide; labial palp with broad distomedial protuberance of 2nd segment and conical 3rd segment ( Fig. 16 ). The same in many other Labiobaetis .

Abdominal cuticular coloration: Varies individually from uniform color pattern on all abdominal terga I–IX ( Figs 10, 12 ) to differentiated, with tergum V having largest unpaired median blank ( Figs 4, 7, 11 ). This individual variation is known for L. pulchellus (see below) and for L. tricolor : uniform coloration of L. tricolor is illustrated by Ikonomov (1962: fig. 12), contrasting coloration with largest median blank on the 5th tergum is illustrated by Müller-Liebenau (1969: Abb. 113).

Imaginal characters

Gonostyli: 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 ). Probably, such shape of gonostyli occurs in this group only.

Penial bridge: Projected caudally forming a pair of rounded lobes with deep concavity between them, with sharply pointed, sclerotized denticle arising from middle of this concavity ( Figs 56, 57, 60 ). The same structure of the penial bridge occurs in L. atrebatinus and L. frondalis ( McDunnough, 1925) (both these species differ from the tricolor group by non-angulate 1st gonostylus segment and by widened setae of the submarginal arc on the larval labrum).

Hind wing: The described species of the tricolor group have narrow hind wings with two longitudinal veins, either lacking costal projection (in L. tricolor , L. propinquus and L. pulchellus – Figs 20, 22, 24, 26 ), or with a small costal projection (in L. calcaratus ). One of us (Kluge) has reared material of an un-described species from Sulawesi, which belongs to the tricolor group and completely lacks hind wings.

Distribution. Holarctic and Oriental Region.

Species composition. Following species are known as larvae and imagines reliably associated by rearing: Palaearctic Labiobaetis tricolor, Nearctic L. propinquus, Palaearctic L. calcaratus and Oriental L. pulchellus . Some other Oriental species belonging to this group are described either only as imagines, or only as larvae. Particularly, Labiobaetis ulmeri ( Müller-Liebenau, 1981) known as male imago from Sumatra has the structure of gonostyli and penial bridge characteristic for the tricolor group.

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).