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Kluge N.J. & Novikova E.A. 2014
Systematics of Indobaetis Müller-Liebenau & Morihara 1982, and related implications for some other Baetidae genera (Ephemeroptera)
Zootaxa 3835 (2): 209–236
preview
Abstract
Imagoes, subimagoes and eggs of Indobaetis costai Müller-Liebenau & Morihara 1982 are described for the first time; additional larval characters of I. costai and I. starmuehlneri Müller-Liebenau & Morihara 1982 are reported. A new species Indobaetis microfolius sp.n. is described based on larvae, male subimago reared from larva and female subimago extracted from mature larva. New combination Baetis michaelohubbardi (Selva-kumar et al. 2012) comb.n. is proposed for a species originally attributed to Indobaetis, based on presence of hind protoptera, three maxillary dentisetae and other characteristics. Newly discovered diversity within the holophyletic taxon Indobaetis disprove formerly erected idea about close relationship of Indobaetis and the muticus-group. Thus, the senior genus-group name for the holophylum including the muticus-group, is Takobia/g1; in rank-based nomenclature the names Alainites Waltz & McCafferty (in Waltz et al.) 1994 and Acerbaetis Kang & Yang (in Kang et al.) 1994 should be junior synonyms of Takobia Novikova & Kluge 1987 (new synonymy). Neotropical taxon Caribaetis Kluge 1992 is accepted as genus (stat.n.), rather than a synonym of Fallceon, based on the original diagnosis of subgenus Caribaetis and taking into account significance of such character as presence of posterior seta on claw, shared with Indobaetis, Baetodes and some other taxa; resultant new combinations are proposed: Caribaetis planifrons (Kluge 1992) comb.n., Caribaetis alcarrazae (Kluge 1992) comb.n. and Caribaetis grandis (Gonzalez-Lazo & Salles 2007) comb.n. A new species synonymy in Fallceon is proposed, based on the presence of a hind wing costal hook in both species: Fallceon poeyi (Eaton 1895) = F. nikitai McCafferty & Lugo-Ortiz 1994 syn.n.
Introduction
Material and methods
1. Systematic position of Indobaetis
1.1. Baetungulata-non-Baetofemorata
1.2. Historical
1.3. Notes about Nigrobaetis, Takobia and Alainites
1.4. Notes about Labiobaetis
1.5. Notes about Pseudocloeon
2. Characters of Indobaetis
2.1. General remarks
2.2. Shape of larval frons
2.3. Setae on mandibles
2.4. Right prostheca
2.5. Excavation of second segment of maxillary palp
2.6. Hypopharynx
2.7. Presence of posterior seta on larval claw
2.8. Scales on larval abdominal terga
2.9. Presence of posterior prolongation of larval paraproct
2.10. Pose of subimaginal gonostyli developing in larva
2.11. Sterno-styligeral muscle
2.12. Number of tarsal segments
2.13. Microlepides on subimaginal tarsus
Müller-Liebenau & Morihara (1982) established the genus Indobaetis for two species from Sri Lanka. These authors accepted the genus Baetis in wide sense, including species later placed to the genera Nigrobaetis Kazlauskas (in Novikova & Kluge) 1987, Takobia Novikova & Kluge 1987, Alainites Waltz & McCafferty (in Waltz et al.) 1994, Labiobaetis Novikova & Kluge 1987 and others. According to the original description, the genus Indobaetis was regarded to be a sister taxon of the muticus-group of the genus Baetis, so the genus Baetis was accepted as a paraphyletic taxon. Other authors placed the muticus-group either to the genus Nigrobaetis (e.g., Kazlauskas 1972), or to the subgenus Nigrobaetis of the genus Baetis (e.g., Novikova & Kluge 1987, 1994), or to the genus Alainites (e.g., Waltz et al. 1994). In its turn, Alainites is regarded to be a plesiomorphon, belonging to the holophylum with the senior name Takobia Novikova & Kluge 1987 (Novikova & Kluge 1994); the same was stated by Waltz et al. (1994), who separated the genus Alainites from Takobia by plesiomorphies only (see Discussion, 1.3). Hereafter this taxon is referred to as Takobia/g1, following the system of rank-free hierarchical nomenclature based on the Code (Kluge 2004). Till recently, the assumption about relationship between Indobaetis, Nigrobaetis, Takobia and Alainites remains to be generally accepted, and some authors refer this assemblage as "Indobaetis-complex" (Lugo-Ortiz & De Moor 2000; Gattolliat et al. 2008).
Prior to this study, Indobaetis was known only as larvae, and such important character, as pose of subimaginal gonostyli developing under larval cuticle, had not been described. In this paper we give additional description to the type species of Indobaetis—I. costai Müller-Liebenau & Morihara 1982. Relationship of Indobaetis and Takobia/g1 (incl. Alainites) appears to be doubtful: besides characters common with Takobia/g1, Indobaetis shares common characters with Labiobaetis Novikova & Kluge 1987 and Papuanatula Lugo-Ortiz & McCafferty 1999a.
The taxa Nigrobaetis/g1 (incl. Takobia) and Labiobaetis comprise about 150 species distributed in Holarctic, Ethiopian and Oriental regions; among them, there are so well-known European species as mutica Linnaeus 1758 [Ephemera], nigra Linnaeus 1762 [Ephemera] and atrebatinus Eaton 1870 [Baetis]. Valid binomina of these species depend upon systematic position of Indobaetis: if unite either Nigrobaetis, or Takobia, or Alainites, or Labiobaetis with Indobaetis, the senior genus-group name would be Indobaetis. Because of this, understanding of systematic position of Indobaetis is important.
Besides Indobaetis costai and I. starmuehlneri, a new species I. microfolius sp.n. from India is described here; this allows to make significant changes to the diagnosis of Indobaetis and to reevaluate characters which were regarded to be synapomorphies of Indobaetis and Takobia/g1 (incl. Alainites).
Imagoes were reared from larvae in cages placed in natural current water. All material, used in this study, will be permanently deposited in the Zoological Institute of the Russian Academy of Sciences (Saint Petersburg, Russia), but is temporarily located in the Department of Entomology of Saint Petersburg State University. In the lists of material examined, the following arbitrary signs are used: L – larva; S – subimago; I – imago; L-S-I♂ – male imago reared from larva, with larval and subimaginal exuviae; L-S-I♀ – female imago reared from larva, with larval and subimaginal exuviae; S-I♂ – male imago reared from subimago, with subimaginal exuviae; L-S♂ – male subimago reared from larva, with larval exuviae; L/S♂ – male subimago extracted from mature larva.
Slides are made in Canadian balsam. In order to examine the sterno-styligeral muscle of fresh specimens, genitals were kept in hot water during one or several hours, to dissolve non-translucent white inclusions.
Indobaetis Müller-Liebenau & Morihara 1982
(Figs 2–75)
Type species: Indobaetis costai Müller-Liebenau & Morihara 1982.
General characteristic given to Indobaetis by Müller-Liebenau & Morihara (1982) should be modified as the following.
Apomorphies of Indobaetis.
(1) Each mandible has incisor and kinetodontium completely fused together forming an integral plate with cutting edge widened, evenly dentate and vaulted ventrally, so that its part corresponding to incisor is less projected medially than its part corresponding to kinetodontium (Figs
46–48; Müller-Liebenau & Morihara 1982: Figs 1f,
2f 
).
(2) Prostheca of right mandible is slender and pointed, not bifurcate (Figs 47,
48; Müller-Liebenau & Morihara 1982: Figs 1f, 2f ) (see
Discussion,
2.4).
(3) Maxilla has 2 dentisetae: 1st dentiseta (most distal) is thick and adjacent to maxillary canines (as in many other Baetidae); 2nd dentiseta is sharply arched and pressed to the first dentiseta, so that its middle part is hidden between the first dentiseta and the canines; 3rd dentiseta is absent; setae of median-dorsal row form a compact bunch, basally adjacent to the second dentiseta and distally diverging from it (Figs 10, 51). In other Baetidae three dentisetae, initial for Tridentiseta Kluge et al. 1995, are retained (Kluge 2004: Figs 28B, D).
(4) Larval tibia has a regular row of stout setae on outer margin, different from setae of a regular row on outer margin of femur (Figs 22, 67, 68).
(5) Larval claw has distal denticle enlarged, with at least one strong seta posteriad of it (Figs 42, 58) (see Discussion, 2.7).
(6) Hind wings are absent; larva has no vestiges of hind protoptera (Müller-Liebenau & Morihara 1982: Figs 1i,
2g ).
(7) Tergalii of first pair are lost, only 6 pairs of tergalii are present.
(8) In mature larva buds of subimaginal gonostyli are folded by «Labiobaetis-type» (Figs 28, 29); this character is known only for I. costai (see Discussion, 2.10).
(9) On fore leg of female subimago and imago 1st tarsomere is completely fused with 2nd tarsomere, so the tarsus is 4-segmented (Figs 2–4, 5 ), like tarsi of middle and hind legs (Fig. 11). This character is known for I. costai and I. microfolius sp.n. In most other Baetidae fore tarsus of female subimago and imago has 1st tarsomere well separated from 2nd tarsomere (Fig. 1) (see Discussion, 2.12).
Character of Indobaetis of unclear phylogenetic polarity.
(10) In subimago, 1st and 5th tarsomeres are covered mainly with pointed microlepides, other tarsomeres mainly with blunt microlepides (Figs 5–8, 11–17); this character is known for I. costai and I. microfolius sp.n. (see Discussion, 2.13)
Plesiomorphy of Indobaetis.
(11) Sterno-styligeral muscle is retained (Figs 21, 24, 54); this character is known for I. costai and I. microfolius sp.n. (in contrast to Labiobaetis, Baetosternata and some other taxa, whose sterno-styligeral muscle is completely lost—see Discussion, 2.11).
Characters variable among species of Indobaetis. Larval habitus varies from Nigrobaetis-like in I. costai and I. starmuehlneri (i.e., with head bowed ventrally, head and thorax laterally compressed, three caudalii and their primary swimming setae well developed) to Acentrella-like in I. microfolius sp.n. (i.e., head and thorax flattened ventrally, paracercus reduced, and swimming setae lost). Frons varies from narrow and keeled to wide and flat (Figs 40, 41, 55). Maxillary palp, being 2-segmented (as in all Baetungulata), has 2nd segment either incised (in I. costai), or not (in other species—Fig. 51). Transverse row of fine setae on glossa is either present (in I. costai and I. starmuehlneri), or absent (in I. microfolius sp.n.—Fig. 50). Labial palp either has structure usual for Baetidae (in I. starmuehlneri), or has 2nd segment unusually narrowed (in I. costai), or has 2nd and 3rd segments completely fused together and lacking muscle (in I. microfolius sp.n.—Fig. 52). Patella-tibial suture, being equally developed on all legs (that is characteristic for Anteropatellata), either has normal shape (in I. costai and I. starmuehlneri—Fig. 22), or is smoothed and stretches along tibia (in I. microfolius sp.n.—Fig. 67). Larval paraproct either has tongue-like denticulate prolongation of inner posterior edge (in I. costai and I. starmuehlneri—Figs 38, 39), or with posterior margin non-expressed (in I. microfolius sp.n.—Fig. 72).
Distribution. Southern India and Sri Lanka.
Species composition. 3 species: Indobaetis costai Müller-Liebenau & Morihara 1982, I. starmuehlneri Müller-Liebenau & Morihara 1982 and I. microfolius sp.n.
Comments. Selva-kumar et al. (2012) described Indobaetis michaelohubbardi based on larvae from southern India. Subsequent reexamination of the type specimens reveals that this species has hind protoptera and other characters of Baetis s.str. (K.G. Sivaramakrishnan, personal communication). In the photo (Selva-kumar et al. 2012: Fig. 34) three maxillary dentisetae are visible, that allows to exclude this species from Indobaetis. According to the photos (Selva-kumar et al. 2012: Figs 29–38) this species belongs to subgenus Tenuibaetis Kang & Yang (in Kang et al.) 1994 of the genus Baetis s.str. So, the valid binomen is Baetis michaelohubbardi (Selva-kumar et al. 2012), comb.n.
Indobaetis costai Müller-Liebenau & Morihara 1982
(Figs 2, 3, 5–35, 38, 39, 41–44)
Material. SRI LANKA: Uva province., Badulla district, Haputale 15–23.I.2011, coll. N. Kluge & L. Sheyko: 5 L-S-I♂, 1 L-S/I♂, 1 L-S♂, 7 L-S-I♀, 1 L-S/I♀, 2 L-S♀, S-I♀, 34 larvae; the same district, Lemastota Oya, 20–21.I.2011, coll. N. Kluge & L. Sheyko: 27 larvae; Sabaragamuwa province, river Seetha Sangula, Dalhausie near Sri Pada (Adam's Peak), 24–26.I.2011, coll. N. Kluge & L. Sheyko: 10 larvae; Central province, Nuwara Eliya district, Ginigathhena (17 km N Hatton), 31.I–3.II.2011, coll. N. Kluge & L. Sheyko: 1 larva.
Larva.
CUTICULAR COLORATION: Dorsum of head, thorax and abdomen nearly uniformly light brown, with diffusive lighter areas; medioposterior sigilla either lighter than background (Müller-Liebenau & Morihara 1982: Fig.
3 ), or of the same color. Thoracic and abdominal sterna colorless. Legs nearly uniformly light, femora can be slightly diffusively darkened on inner and outer sides. Caudalii nearly uniformly light brownish, proximally darker and distally lighter.
HYPODERMAL COLORATION: Either not expressed, or posterior margin of each abdominal tergum bordered by darker brown, as in imago (Fig. 20).
SHAPE AND SETATION: Head moderately narrowed; frons between antennae bases elevated, but flat; arms of frontal suture angulated (Figs 41, 44). 2nd segment of labial palp, being unusually narrowed, retains muscle which moves 3rd segment. Pronotum with length less than ½ width (Fig. 43). Patella-tibial suture developed on all legs (Fig. 22). Tergalii unable for rhythmic respiratory movements. Caudalii with well-developed primary swimming setae on lateral sides of paracercus and median sides of cerci. Other characters as described by Müller-Liebenau & Morihara (1982).
MALE GENITALS. Subimaginal gonostyli developing under cuticle of mature male larva, are bent medially-cranially, so that 1st and 2nd segments are directed medially, and 3rd segment is directed medially-cranially (Figs 28, 29).
Subimago.
CUTICULAR COLORATION: Pronotum light brow with colorless blanks. Mesonotum light brown, with medioparapsidal suture, sublateroscutum and lateral area of scutellum contrastingly colorless (Fig. 18). Thoracic sterna and pleura with light membranes and brown sclerites; posterior part of postsubalar sclerite with sharply convex dorsal margin (Fig. 19). Wings gray. Cuticle of legs nearly uniformly light brownish. Cuticle of abdominal terga and sterna uniformly light grayish-brown, with small lighter medio-anterior and medio-posterior sigilla.
HYPODERMAL COLORATION: Similar to imago (see below).
TEXTURE: On fore leg of male subimago, 1st tarsomere covered with pointed microlepides; 2nd–4th tarsomeres covered with blunt microlepides, with pointed microlepides near distal margin; 5th tarsomere covered with pointed microlepides (Figs 6–8). On middle and hind legs of both sexes 1st+2nd, 3rd and 4th tarsomeres covered with blunt microlepides, with pointed microlepides near distal margin; 5th tarsomere covered with pointed microlepides (Figs 11–17). Fore leg of female (4-segmented—see below) with the same texture as on middle and hind legs (Figs 2, 5 ).
Imago, male. Head light brown with ocher. Turbinate eyes high, nearly cylindrical, slightly widened apically, uniformly red (Fig. 25). Thorax light brown with ocher membranes, dorsally slightly darker brown. Wing with basal sclerite and very bases of longitudinal veins light brownish; remainder parts of veins, including costal brace, pale or colorless; wing membrane colorless. Cross veins flattened and widened, but not colored (Fig. 23). Pterostigma with few oblique veins, which can be either anastomozed (Fig. 23), or simple. Hind wings absent. Fore legs uniformly light ocher; middle and hind legs lighter. On fore leg tibia 2 times longer than femur, tarsus 2 times shorter than tibia (i.e. subequal to femur). On middle and hind legs tibia 1.25 times longer than femur, tarsus 3 times shorter than tibia. Abdominal segment I light brownish; segments II–VI whitish, but not translucent; segments VII–X ocher with brownish; each tergum I–X with brown band on posterior margin (Fig. 20). Genitals light brownish. Cerci uniformly light ocher.
GENITAL STRUCTURE (Figs 21, 24): Unpaired sterno-styligeral muscle present. Gonovectes weak and slightly bent. Unistyligers with convexities on median sides. Gonostylus with 1st segment conic and not separated from 2nd segment; 3rd segment narrow and elongate.
Imago, female. Head light brown with ocher, flattened, short and wide, with eyes small and widely separated (Fig. 26). Thorax light brown with ocher. Legs uniformly light ocher. Wing with longitudinal and cross veins brown, membrane slightly colored with pale ocher. Fore leg has the same structure as middle and hind leg, with tarsus 4-segmented (Fig. 3). Abdominal terga either nearly uniformly ocher-brown, or each tergum ocher in middle part and brown in anterior, posterior and lateral parts. Abdominal sterna ocher.
Egg (Figs 30–35). About 0.1 mm length, subcylindrical. Chorion thin, armed with stick-like ridges which are connected by their ends and form irregular net with large cells; in middle of each cell locates a shallow round protuberance surrounded by smaller protuberances; other surface of cell covered by irregular protuberances. Micropile small, round, often locates at point where several ridges are connected.
Dimension. Fore wing length 4.5–5 mm.
Distribution and habitat. Sri Lanka. Larvae are common in various mountain streams with stony bottom.
Indobaetis starmuehlneri Müller-Liebenau & Morihara 1982
(Fig. 40)
Material. SRI LANKA: Uva province., Badulla district, Lemastota Oya, 20–21.I.2011, coll. N. Kluge & L. Sheyko: 1 larva.
Larval characters. Head narrower than in I. costai, frons between antennae bases forms a keel; arms of frontal suture shallowly arched (Fig. 40). 2nd segment of labial palp retains muscle which moves 3rd segment. Pronotum with length less than ½ width (as in Fig. 43). Patella-tibial suture developed on all legs (as in Fig. 22). Caudalii with well-developed primary swimming setae on lateral sides of paracercus and median sides of cerci. Other characters as described by Müller-Liebenau & Morihara (1982).
Subimago, imago and eggs. Unknown.
Distribution. Sri Lanka.
Indobaetis microfolius sp.n.
(Figs 45–75)
Material. Holotype: L-S♂ {specimen [IV] (5)}: INDIA, state Karnataka, Shivamogga district, a small mountain forest stream—tributary of river Agumbe-hole between village Malandur and the road Agumbe—Sringeri, about 4 km ESE of Agumbe, 16.I.2013, coll. N. Kluge, L. Sheyko. Paratypes: the same locality, 1 L/S♀, 1 larva.
Larva.
CUTICULAR COLORATION: Dorsum of head, thorax and abdomen uniformly light brown. Thoracic and abdominal sterna colorless. Legs nearly uniformly light brown. Caudalii nearly uniformly light brow.
HYPODERMAL COLORATION: Abdominal terga can be brown, as in subimago.
SHAPE AND SETATION: General shape Acentrella-like: flattened ventrally, with enlarged legs and shortened abdomen. Head, pronotum and mesonotum with protoptera densely covered with placoid sensilla (Fig. 45). Head wide; frons between antennae bases flat; arms of frontal suture shallowly arched (Figs 45, 55). Labrum with regular submarginal row of 7–8 thick pointed setae on each side (Fig. 49). Each mandible with incisor and kinetodontium completely fused together forming plate widened distally and vaulted ventrally; prostheca of right mandible slender and pointed; each mandible without setae on median margin between prostheca and mola (Figs 46–47). Maxillary palp without incision (Fig. 51). Hypopharynx with dense apical tuft of long spines (Fig. 71). Labium (Fig. 50, 52) with glossae slightly shorter and much narrower than paraglossae; paraglossa swollen in middle. Glossa terminated by single long, widened proximally and pointed seta; its median margin with 2 setae near apex; lateral margin with 2 more slender setae near apex; other setae absent. 2nd and 3rd segments of labial palp fused together, wide, without muscle which initially moves 3rd segment. Pronotum unusually long, with length exceeding ½ width (Fig. 59). Outer side of femur with regular row of long stout setae; each seta parallel-sided, with apex dentate (Fig. 69); two setae near apex of femur shorter, with apices more smooth (Fig. 66). Outer-dorsal side of tibia with regular row of stout setae; each seta terminates by slender process and bears numerous fine short processes on its side directed toward distal end of tibia (Fig. 68). Patella-tibial suture of all legs modified to a shallow groove running along tibia close to row of stout setae and terminates near tibial apex (Figs 66–68). Claw with distal denticle enlarged, other denticles smaller; two setae arise by sides of distal denticle—one on anterior and another on posterior side of claw (Fig. 58). Abdominal terga with scales in small semicircular nests lacking operculae (Fig. 65). Posterior margin of each tergum I–X with irregular, minute, pointed denticles in lateral parts and wider denticles in middle part (Figs 60, 64). Abdominal sterna without scales and posterior denticles, each with one pair of small denticulate fields near anterior-lateral corner (Fig. 61). Tergalii I absent; tergalii II–VII unusually small, not longer than ½ of tergum length; anterior and posterior costae developed only on proximal part of tergalius; trachea not visible (Figs 53, 60, 62). Paraprocts without distinct posterior margins; each paraproct with one or two denticles (Fig. 72). Paracercus reduced to several segments (3, 10 and 13 segments in three specimens examined), without lateral swimming setae or their vestiges (Fig. 75); ventral side of paracercus with fields of dense minute spines adjacent to posterior margin of each segment (Fig. 74); dorsal side with flat triangular denticles on posterior margins of segments (Fig. 73). Cerci without swimming setae or their vestiges; distal margin of each segment with flat triangular denticles (Figs 73, 74).
Subimago.
CUTICULAR COLORATION: Mesonotum light brown, with medioparapsidal suture, sublateroscutum and lateral area of scutellum contrastingly colorless (as in Fig. 18). Thoracic sterna and pleura with light membranes and brown sclerites; posterior part of postsubalar sclerite without dorsal convexity. Wings gray.
HYPODERMAL COLORATION: In both sexes, abdominal terga uniformly dark brown with irregular small light dots; sterna light (Fig. 70).
TEXTURE: On fore leg of male subimago, 1st tarsomere covered with pointed microlepides; 2nd–4th tarsomeres entirely covered with blunt microlepides; 5th tarsomere covered with pointed microlepides (as in Figs 6–8). On middle and hind legs of both sexes 1st+2nd, 3rd and 4th tarsomeres covered with blunt microlepides; 5th tarsomere covered with pointed microlepides (as in Figs 11–17). Fore leg of female (4-segmented—see characteristics of Indobaetis) with the same texture as on middle and hind legs (Fig. 4).
Imago, male. Unknown. Judging by male subimago, has following features. Turbinate eyes unusual in shape, with facetted surface much narrower than base (Fig. 57); in subimago, turbinate eyes uniformly dark red. Abdominal terga uniformly dark brown with irregular small light dots; sterna light (Fig. 70).
GENITAL STRUCTURE (Fig. 54): Unpaired sterno-styligeral muscle present. Gonovectes weak and slightly bent. Gonostylus has 1st segment not narrowed toward apex and sharply separated from 2nd segment; 3rd segment truncate.
Imago, female. Unknown. Judging by female subimago extracted from mature larva, abdominal terga uniformly dark brown with irregular small light dots (as in male—Fig. 70); thoracic and abdominal sterna light ocher.
Eggs. Unknown.
Dimension. Fore wing length 2.5 mm.
Distribution and habitat. Southern India (Western Ghats). Larvae were collected in a small forest stream, where water level is extremely low in dry season.
Comparison. Larva of Indobaetis microfolius sp.n. differs from other Indobaetis and most other Baetidae by completely fused 2nd and 3rd segments of labial palp (Fig. 52), longitudinal patella-tibial suture (Fig. 67) and very small tergalii (Fig. 53). From other Indobaetis it differs also by absence of transverse row of setae on glossae (Fig. 50), absence of posterior prolongation of paraproct (Fig. 72), Acentrella-like habitus, vestigial paracercus with modified armature (Fig. 74), loss of primary swimming setae on cerci and other characters.
Male subimago (and probably imago) of I. microfolius sp.n. differs from I. costai and most other Baetidae by turbinate eyes narrowing apically (Fig. 57). From I. costai it differs also by entirely dark abdominal terga (Fig. 70) and shape of gonostyli.
1. Systematic position of Indobaetis
1.1. Baetungulata-non-Baetofemorata. All characters of Indobaetis undoubtedly testify that it belongs to the subsequently subordinated taxa: Tetramerotarsata Kluge 1997 > Liberevenata Kluge 1997 > Turbanoculata Kluge 1997 > Anteropatellata Kluge 1997 > Baetovectata Kluge & Novikova 2011 > Baetungulata Kluge & Novikova 2011 (Kluge & Novikova 2011). Its patella-tibial suture is equally developed of fore and other legs of larva and female subimago and imago, that is characteristic for Anteropatellata. In male genitals, gonovectes are bent in the manner characteristic for Baetovectata (Fig. 24); wing has mainly two marginal intercalaries per space (Figs 23, 56), that is also characteristic for Baetovectata. Claw of mature larva has one row of denticles, characteristic for most Baetungulata; as in other Baetungulata, tergalii are unable for respiratory movements; maxillary palp is two-segmented; on fore tarsus of male subimago segments 2–4 are covered mainly by blunt microlepides (Figs 6–8).
Indobaetis does not belong to Baetofemorata Kluge & Novikova 2011: in contrast to all Baetofemorata, larval femora if Indobaetis have no villopore; distal tarsal segment of each leg of subimago is covered by pointed microlepides (Figs 5, 6, 15).
1.2. Historical. Before the genus Indobaetis was described, all Eurasian species recently placed to Baetovectata, were attributed to two artificial genera—Baetis (characterized by presence of hind wings) and Pseudocloeon (characterized by absence of hind wings). Later, the taxon Baetis s.l. was accepted as comprising two-winged representatives (former "Pseudocloeon") and was divided into more natural taxa, regarded either as subgenera (Novikova & Kluge 1987, 1994), or as genera (Waltz & McCafferty 1987b; Waltz et al. 1994). Originally, splitting of the Eurasian species of the former genus Baetis to Baetis s.str., Nigrobaetis and Labiobaetis, was based mainly on pose of their subimaginal gonostyli developing under cuticle of mature male nymph: in Nigrobaetis they have apices directed caudally or laterally-caudally, in Labiobaetis they have apices directed medially-cranially, and in Baetis s.str. they have intermediate position with apices directed medially-caudally (Novikova & Kluge 1987). For Indobaetis this character had not been described, and remained unknown till recently. Based on the finding detailed herein, we now know that at least the type species of Indobaetis has pose of developing gonostyli of the «Labiobaetis-type» (Figs 28, 29). While in Palearctic fauna taxa Nigrobaetis/g1 (incl. Takobia) and Labiobaetis are clearly outlined and well distinguishable one from another, the Oriental taxon Indobaetis has combination of characters common both with Nigrobaetis/g1 and Labiobaetis.
1.3. Notes about Nigrobaetis, Takobia and Alainites. Taxa under these names undoubtedly belong to the plesiomorphon referred either as "non-Baetis complex of Baetinae" (Waltz et al. 1994; Waltz & McCafferty 1997), or as "Baetungulata-non-Baetofemorata" (Kluge & Novikova 2011). In a rank-free classification, hierarchy of these taxa is the following:
[1] Nigrobaetis/g1 (incl. Takobia), or Nigrobaetis s.l.
[1.1] plesiomorphon Nigrobaetis/g2 (sine Takobia), or Nigrobaetis s.str.
[1.2] Takobia/g1 (incl. Alainites, Acerbaetis).
The genus Nigrobaetis (corresponding to Nigrobaetis/g1) was originally proposed by Kazlauskas (1972), who gave its diagnosis and listed known species; the type species was reported in this publication only in indirect form as a reference to the "Baetis niger Gruppe", and on this ground the name Nigrobaetis was regarded to be unavailable (Hubbard 1979). Formal availability of the genus-group name Nigrobaetis has been established in our publication (Novikova & Kluge 1987), where we referred to the private communication by Kazlauskas and designated the type species Ephemera nigra Linnaeus 1761 in a direct form. Waltz et al. (Waltz et al. 1994, Waltz & McCafferty 1997) stated that the author of the name Nigrobaetis should be not Kazlauskas, but Novikova & Kluge, because "Kazlauskas (1972) work was abstracted without bibliographic reference or discriminating description". Actually, Kazlauskas (1972) gave the following characteristics to Nigrobaetis: "die zweite Ader der Hinterflugel ist gegabelt; die Mikroskulptur der Larven ist trapezartig, die Augen rücken fast aneinander". In agreement with the Article 50.1.1 of the 4th edition of the International code of zoological nomenclature, authorship of the name Nigrobaetis belongs to Kazlauskas, with the date of publication by Novikova & Kluge (Hubbard 1990), and should be "Nigrobaetis Kazlauskas (in Novikova & Kluge) 1987".
Waltz and McCafferty (1997) also stated, that "Novikova & Kluge (1994) incorrectly placed ... certain species of Alainites and Takobia in Nigrobaetis. That concept is polyphyletic because it includes species of both the Baetis complex and non-Baetis complex". Actually, we placed in Nigrobaetis not certain, but all examined species of Alainites and Takobia. The genus Baetis s.l. sensu Novikova & Kluge 1987 corresponds to the holophyletic taxon Baetungulata Kluge & Novikova 2011, which includes the subordinated holophyletic taxon Baetofemorata Kluge & Novikova 2011 (= "Baetis complex" sensu Waltz & McCafferty 1997); holophyly of these two taxa have never been questioned. In this case, Waltz and McCafferty mixed the "genus Baetis" sensu Novikova & Kluge with the "genus Baetis" sensu Waltz & McCafferty; such confusions often appear if use classifications with limited number of formal ranks (Kluge 1999).
The taxon, which in the rank-free nomenclature has the name Nigrobaetis/g1, can bear either subgeneric rank (subgenus Nigrobaetis sensu Novikova & Kluge 1987), or generic rank (genus Nigrobaetis sensu Kazlauskas 1972), or higher rank; in all cases it includes type species of the genus-group names Nigrobaetis Kazlauskas (in Novikova & Kluge) 1987, Takobia Novikova & Kluge 1987, Alainites Waltz & McCafferty (in Waltz et al.) 1994 and Acerbaetis Kang & Yang (in Kang et al.) 1994, among which the senior genus-group name is Nigrobaetis. Validity of this name is based on our conclusion that the type species of an older genus-group name Indobaetis Müller-Liebenau & Morihara 1982 does not belong to this taxon.
The type species of Takobia is Centroptilum maxillare Braasch & Soldan 1983; it differs from all other Baetungulata by long claws lacking denticles; because of this, the taxon Takobia was originally described as a monotypic subgenus and opposed to the subgenus Nigrobaetis (Novikova & Kluge 1987). After rearing imagoes from larvae of the species maxillare [Centroptilum] and of the closely related species kogistani Novikova & Kluge 1994 [Baetis (Nigrobaetis)], it became clear that the unusual claw structure of maxillare [Centroptilum] is not primitive, but derived one, and this species should be attributed to the muticus-group within Nigrobaetis (Novikova & Kluge 1994). However, Waltz et al. (1994) established for the muticus-group a new genus Alainites with the type species mutica Linnaeus 1758 [Ephemera], and separated Alainites from Takobia by plesiomorphies only: "The autapomorphies associated with Takobia distinguish that genus from Alainites, and include in the adult the posteriorly produced head capsule, and in the larvae the highly modified maxillary palps, the increased setation on the mouthparts and labrum, and the extreme reduction or loss of claw denticles". These authors could not determine circumscription of their plesiomorphon Alainites: they placed the species kogistani [Baetis (Nigrobaetis)] to the genus Takobia (Waltz & McCafferty 1997), in spite of the fact that according to the previously given diagnosis (Waltz et al. 1994) it should be placed to Alainites.
Nearly simultaneously with Alainites, another genus-group name for the same muticus-group was established—Acerbaetis, with another type species—Baetis (Acerbaetis) clivosus Chang & Yang (in Kang et al.) 1994. Subjective synonymy of Alainites and Acerbaetis was proposed by Waltz & McCafferty (1997) and have not been questioned.
The muticus-group in wide sense constitute the holophyletic taxon Takobia/g1, whose rank can be either subgeneric, or generic, or other, but lower, than the rank of Nigrobaetis/g1 in the same classification. In all cases Takobia/g1 includes type species of the genus-group names Takobia, Alainites and Acerbaetis, among which the senior genus-group name is Takobia. Validity of this name is based on our conclusion that the type species of an older genus-group name Indobaetis does not belong to this taxon.
Following the Hennig's (1950) principles of phylogenetic systematics, it is used to avoid paraphyly. Temporary presence of plesiomorphon can be justified, only if it is necessary for establishing of a holophyletic taxon. For example, at the present step of knowledge, it would be impossible to establish a holophyletic taxon Takobia/g1 (incl. Alainites, Acerbaetis) without recognition of a temperate plesiomorphon Nigrobaetis/g2. But if a holophylum, which should be reflected in classification, consists of a single species, it does not need a name other than the name of species, so it is unnecessary to unite all related species in a plesiomorphon. Because of this, in the rank-based nomenclature, it is used to establish subjective synonymy between names of a monotypic holophylum and a plesiomorphon ancestral to it; according to the International code of zoological nomenclature, the valid name should be the formally oldest one, independently if it has been originally given to a small aberrant group, or to a large plesiomorphon. This approach is generally accepted, in spite of the fact that in some cases it leads to changing binomina of many species. In systematics of Baetidae, such example is the generally accepted synonymy established by McCafferty & Waltz (1990: 783) between the names Camelobaetidius Demoulin 1966 (which was originally given for a single aberrant species) and Dactylobaetis Traver & Edmunds 1968 (which was originally established for a plesiomorphon comprising more than 13 species described at that time); as the name Camelobaetidius is the senior one, binomina of 17 species of the former Dactylobaetis have been changed. For the same reason, the genus-group name Takobia (originally given for a single aberrant species, whose systematic position was unknown), and the names Alainites and Acerbaetis (both originally given for a larger plesiomorphon) should be regarded as subjective synonyms: Takobia Novikova & Kluge 1987 = Alainites Waltz & McCafferty (in Waltz et al. 1994 syn.n. = Acerbaetis Kang & Yang (in Kang et al.) 1994 syn.n.; in accordance with this, binomina of the species formerly attributed to the genus Alainites should be changed. Unlike the rank-based nomenclature, in the rank-free hierarchical nomenclature formal subjective synonymy is absent, and original binomina are used (Kluge 2004).
The taxon Takobia/g1 (incl. Alainites, Acerbaetis) differs from Nigrobaetis/g2 by a single character: larval paraproct has a prolongation of posterior margin (see 2.9). Waltz et al. (1994) stated that Alainites differs from Nigrobaetis also by "body laterally compressed" (in Nigrobaetis "cylindrical") and by shorter terminal segment of gonostylus. Actually, cross section of body depends on muscles contraction, being similar in all Nigrobaetis/g1. Long terminal segment of gonostylus occurs in some species, which Waltz & McCafferty (1997) placed to Alainites (e.g., in talasi Novikova & Kluge 1994 [Baetis]).
Nigrobaetis/g2 is a plesiomorphon, because it differs from Takobia/g1 (incl. Alainites, Acerbaetis) only by a plesiomorphy—absence of prolongation of larval paraproct.
Nigrobaetis/g1 (incl. Takobia) has no unique autapomorphies, but is characterized by a constant combination of characters, each of which is found in some other taxa: larval frons is always narrowed and forms a keel (see 2.2); glossae are not much wider than paraglossae; labial palp with second segment not greatly projected, third segment not narrowed and indistinctly truncated; larval claws (usually with one row of denticles characteristic for Baetungulata) not strongly hooked, without middle and subapical setae (see 2.7); larval abdominal terga always with scales in trapezoid nests with corner operculae (see 2.8); paracercus always well-developed; primary swimming setae of cerci and paracercus always well-developed; hind wing, if present, with second longitudinal vein usually forked; developing gonostyli are always folded in the «Nigrobaetis-type» pose (see 2.10) (Fig. 76); sterno-styligeral muscle is always retained (see 2.11).
Jacob (2003: 123) have included Baetis macdunnoughi Ide 1937 to Nigrobaetis s.l. (which he accepts in subgeneric rank) and have synonymized Acerpenna Waltz & McCafferty 1987b with Nigrobaetis. At present, we do not accept this synonymy, because the examined representative of Acerpenna has the pose of developing subimaginal gonostyli of «Labiobaetis-type» (Fig. 77), but not of «Nigrobaetis-type» which occurs in all Nigrobaetis/g1 (Fig. 76).
Sroka (2012) assumed paraphyly of the plesiomorphon Nigrobaetis/g2 and sister relationship between N. gracilis and Alainites, but have not reported any apomorphy to support this assumption.
Besides Nigrobaetis/g1 the same structure of hind wings with forked second vein and non-hooked costal process is present in Notogean taxa described under generic names Offadens Lugo-Ortiz & McCafferty 1998b, Andesiops Lugo-Ortiz & McCafferty 1999b, Edmundsiops Lugo-Ortiz & McCafferty 1999c and some others. In contrast to Nigrobaetis/g1, larvae of these taxa have frons non-narrowed and flat.
1.4. Notes about Labiobaetis. The taxon Labiobaetis Novikova & Kluge 1987 was originally established as subgenus of the genus Baetis s.l., and then was raised to genus rank by McCafferty & Waltz (1995). Its systematic position is unclear: it undoubtedly belongs to Baetungulata, but occupies transitional position between Baetofemorata (= Baetis complex) and Baetungulata-non-Baetofemorata. While in true Baetofemorata femoral patch is always well expressed in a form of compact group of small setae, in Labiobaetis it is either absent, or represents a spaced group of setae. Because of this, Labiobaetis is placed either to "Baetis complex" (McCafferty & Waltz 1995, Waltz & McCafferty 1997), or to Baetungulata-non-Baetofemorata (Kluge & Novikova 2011).
Labiobaetis is characterized by a number of derived characters, some of which are not fond in other taxa: larval scapus sometimes has an apical-lateral projection; maxillary palp sometimes has subapical excavation on inner side of second segment (see 2.5); labium has paraglossae widened and glossae diminished; labial palp has more or less greatly enlarged inner-apical projection of second segment. Each of these characters is present in some species of Labiobaetis, but absent in others. McCafferty & Waltz (1995) established a separate genus Cymulabaetis characterized by absence of projection on scapus and absence of excavation on maxillary palp; but there are species with all possible combinations and transitional states of these characters, so the name Cymulabaetis have been synonymized with Labiobaetis (Lugo-Ortiz & McCafferty 1997). Variability of these characters is so great, that it is difficult to mark boundary between Labiobaetis and some other taxa.
In contrast to Nigrobaetis/g1, in Labiobaetis developing gonostyli are always folded in the «Labiobaetis-type» pose and sterno-styligeral muscle is always absent (36 species are examined). The same characters are found in some other taxa, which are not related to Labiobaetis (see 2.10 and 2.11 below).
Monaghan et al. (2005) and Gattolliat et al. (2008) have suggested a phylogeny reconstruction of Afrotropical and some other Baetidae based on rDNA. Their cladogram has important coincidences with our conclusions based on morphological data. However, these authors compared their results only with the old division of Baetidae into Baetinae and Cloeoninae sensu Kazlauskas 1972, which was based on the USSR fauna, and completely ignored the modern division of Turbanoculata into the plesiomorphon Afroptilinae Kluge 1997 and the holophylum Anteropatellata Kluge 1997, which has much better coincidence with their cladogram. Among other conclusions, they state that the genera Labiobaetis and Pseudopannota are "polyphyletic". But on their cladogram (Monaghan et al. 2005: Fig. 1; Gattolliat et al. 2008: Fig. 1) both taxa are shown not as polyphyletic, but as paraphyletic: Labiobaetis as ancestral for Pseudopannota + Ophelmatostoma, and Pseudopannota Waltz & McCafferty 1987a as ancestral for Ophelmatostoma Waltz & McCafferty 1987a. Possibly, this is correct: our examination of a mature male larva of an undescribed species of Pseudopannota reveals absence of sterno-styligeral muscle and the «Labiobaetis-type» of gonostyli folding, that is characteristic for Labiobaetis. Possibly, Pseudopannota + Ophelmatostoma is an aberrant group within Labiobaetis s.l., and Ophelmatostoma is an aberrant group within Pseudopannota s.l. To confirm this assumption, more material on Pseudopannota s.l. should be examined. Unfortunately, the papers by Monaghan et al. (2005) and Gattolliat et al. (2008) contain only final trees resulted from calculations, but not any concrete molecular characters (nucleotide sequences common for certain taxa), which would allow to speculate about their synapomorphic or symplesiomorphic nature and to include them into further phylogenetic analysis.
Sroka (2012) assumed sister relationship between Labiobaetis and Nigrobaetis/g1. This assumption was based solely on examination of two European species of Labiobaetis, whose larvae resemble Nigrobaetis/g1 in narrowed frons and body, while diversity of non-European species of Labiobaetis was ignored.
1.5. Notes about Pseudocloeon. Originally, the genus Pseudocloeon Klapálek 1905 was established for all baetid species which have double marginal intercalaries and lack hind wings. Now it is generally accepted, that hind wings have been reduced independently in many groups of Baetovectata (i.e., Baetidae with double intercalaries), so the genus Pseudocloeon in its original sense is polyphyletic. At present, two-winged species of Baetovectata are attributed to various more natural taxa. The name Pseudocloeon has priority upon names of all these taxa, but till now we do not know to which of them it should be attributed. The type species of Pseudocloeon is P. kraepelini Klapálek 1905 described as male imagoes from Bogor (former Buitenzorg) in Java; larva of this species is unknown. Lugo-Ortiz et al. (1999) regarded Pseudocloeon to be a senior synonym of Labiobaetis (which also includes two-winged species). Subsequently (e.g., Gattolliat 2001; McCafferty et al. 2010), this synonymy had not been recognized, because shape of gonostyli of P. kraepelini is different from typical for Labiobaetis.
Since our previous discussion on the status of Pseudocloeon (Kluge & Novikova 2011) the following information has been added. We have got one male imago belonging to P. kraepelini, collected by S. Melnitsky at light, 23.II.2008, near river Ci Liwung in the botanic garden of Bogor. One of us (N. Kluge) intensively collected larvae in the same place of this river 31.VIII and 1.X.2012, but could not find any specimen of P. kraepelini. Among 5 species of Baetidae, whose larvae were found in this place, 3 species lack hind wings; these are Acentrella (Liebebiella) vera (Müller-Liebenau 1982b) [originally Pseudocloeon verum], Labiobaetis sp. and Nigrobaetis (s.str.) sp.; male imago, reared from larva of Labiobaetis sp., does not agree with characters of P. kraepelini.
Examination of the fresh male imaginal specimen reveals that P. kraepelini has no sterno-styligeral muscle. This means, that among two-winged Baetidae inhabiting this area, P. kraepelini cannot belong neither to Nigrobaetis/g1 (incl. Takobia), nor to Cloeodes Traver 1938 s.l. (including Centroptella Braasch & Soldan 1980), nor to Acentrella/fg1 (sensu Kluge & Novikova 2011), whose male imagoes retain sterno-styligeral muscle. By the same reason, Indobaetis cannot appear to be a synonym of Pseudocloeon.
Possibly, P. kraepelini belongs to the group comprising two-winged Philippinean species Baetis luzonensis Müller-Liebenau 1982a and B. realonae Müller-Liebenau 1982a and an undescribed species from Sulawesi, whose male imagoes are unknown.
2.1. General remarks. The principle of cladoendesis takes into account the fact, that the same character in different taxa can be conservated or non-conservated (Kluge 2012). "Quae in uno genere ad Genus stabiliendum valent, minime idem in altero necessario praestant" (Linnaeus 1751: paragraph 169). In contrast to this, some modern matrix methods for cladogram building demand to put into a matrix each character as equally significant for all taxa under consideration, that makes such matrices unnatural.
Formerly, conclusions about phylogenetic position of Indobaetis were based on two Ceylonese species only. Recent discovery of the new species Indobaetis microfolius sp.n., which has synapomorphies with the type species of Indobaetis, but differs from it by many characters, allows to reevaluate some characters of Indobaetis.
2.2. Shape of larval frons. Frons between antennal bases differs among species of Indobaetis: in I. starmuehlneri it is narrowed and forms a convex keel (i.e., triangular in cross section) (Fig. 40); in I. costai it is also narrowed and projected, but with flat surface (i.e., trapezium in cross section) (Fig. 41); in I. microfolius sp.n. it is not narrowed and flat (Fig. 55). In Nigrobaetis/g1 (incl. Takobia) form of frontal keel is constant in all species. Besides Nigrobaetis/g1, the same constant frontal keel is present in all species of the Caribbean taxon Fallceon Waltz & McCafferty 1987b (sensu Kluge 1992b). In Labiobaetis form of frons varies among species, from wide and flat to more or less narrowed and keel-like projected. In some other baetid taxa presence/absence of frontal keel also varies from species to species.
2.3. Setae on mandibles. In our earlier paper (Novikova & Kluge 1987) we stated that
Nigrobaetis has setae between prostheca and mola at least on right mandible. Actually, in various species of Nigrobaetis/g1 (incl.
Takobia), small and sparse setae are either present on both mandibles, or on right mandible only, or absent on both mandibles. In some species (e.g.,
N. muticus and related species) vestigial setae are present in some individuals, being absent in others (Kazanci & Thomas 1989: Figs 1a–d
). Among
Indobaetis, setae are constantly present on right mandible of I. costai and
I. starmuehlneri (Müller-Liebenau & Morihara 1982: Figs 1f, 2f ), but absent on both mandibles of
I. microfolius (Figs 46–48).
2.4. Right prostheca. In all Turbanoculata prosthecae of mandibles are modified: at least prostheca of left mandible is directed medially, integral and stick-like, being separated into processes only at apex (Fig. 46). In most other mayflies, including Siphlaenigma, both prosthecae are brush-like, separated to diverging processes nearly from base, directed medially and proximally (Kluge 2004: Fig. 26C); this resembles a bunch of setae, from which prostheca has evolved.
In selected taxa of Turbanoculata prostheca of right mandible is not stick-like, but has a characteristic shape of two diverging setae, most proximal of which is longer and usually directed proximally, toward mola. This character was regarded to be an autapomorphy of the group comprising
Baetis muticus and Baetis navasi, i.e., to Takobia/g1 (incl. Alainites) (Müller-Liebenau & Morihara 1982: Fig.
7 ). But actually, besides Takobia/g1, the same shape of right prostheca occurs in
Nigrobaetis acinaciger (Kluge 1983 [Baetis]) and N. hageni (Eaton 1884
[Baetis]), which, unlike Takobia/g1, have no prolongation of paraproct. Just the same shape of right prostheca occurs in various evidently non-related taxa among Protopatellata (e.g., some
Dabulamanzia Lugo-Ortiz & McCafferty 1996a), among Baetovectata-non-Baetungulata (e.g.,
Cloeodes Traver 1938) and among Baetungulata-non-Baetofemorata (e.g., Andesiops Lugo-Ortiz & McCafferty 1999b). At the same time, this bifurcate shape of right prostheca never occurs in taxa other than Turbanoculata.
Thus, both types of right prostheca (stick-like directed medially and bifurcate seta-like directed proximally) have been encoded in the genome initial for Turbanoculata. In phylogenetic analysis of Turbanoculata, both types of right prostheca should be regarded as alternating plesiomorphies, no one of them being an apomorphy. At the same time, conservation of this or that type of right prostheca can be an autapomorphy of a certain taxon within Turbanoculata.
In Nigrobaetis/g1 both these types of right prostheca are found. In Labiobaetis right prostheca is conservatively stick-like. In Indobaetis right prostheca has peculiar shape, being very slender, but not bifurcate.
2.5. Excavation of second segment of maxillary palp. Among Indobaetis, it is present in
I. costai, being absent in I. starmuehlneri and I. microfolius sp.n.
(Fig.
51; Müller-Liebenau & Morihara 1982: Figs 1d, 2d ). In the same way its presence/absence varies among species of
Labiobaetis. In other taxa this character is not found.
2.6. Hypopharynx. In all three species of Indobaetis hypopharynx bears on its apex a dense tuft of long, stout, seta-like spines
(Fig.
71; Müller-Liebenau & Morihara 1982: Figs 1e, 2e ). Similar tuft of spines is present in selected species of
Labiobaetis and Papuanatula, but not in any species of Nigrobaetis/g1.
2.7. Presence of posterior seta on larval claw. In Baetungulata larval claw usually is not long and more or less strongly hooked apically; its inner margin usually bears one row of denticles asymmetrically located nearer to anterior side of claw. In certain taxa of Baetungulata, claw bears one of two types of setae: either subapical, or posterior ones. Subapical (or preapical) setae are always two and located symmetrically by sides of the hooked apical part of the claw much distad of denticles (Kluge & Novikova 2011: Fig. 32). Presence/absence of subapical setae varies from species to species in certain baetid taxa adapted for inhabitance on stones in rapid streams: Rhodobaetis, Acentrella, Andesiops and others. In literature the term "subapical seta" is often applied to seta of another type, much thicker and located more proximally (Kluge 1992a, Lugo-Ortiz & McCafferty 1996b). In order to distinguish these two types of setae, it is better to term the last one "posterior seta". The posterior seta is thick and located near the most distal denticle, asymmetrically on posterior side of the claw (Fig. 42). Setae of these two types (subapical and posterior ones) are never present together. The posterior seta is so characteristic, that looks like an autapomorphy of a certain taxon. But other characters testify that this seta had to appear or disappear several times.
The posterior seta is present in selected taxa of Baetungulata, either belonging or not belonging to Baetofemorata. Among Baetungulata-non-Baetofemorata, these are American taxa Baetodes Needham & Murphy 1924, Prebaetodes Lugo-Ortiz & McCafferty 1996b, Moribaetis Waltz & McCafferty 1985, Mayobaetis Waltz & McCafferty 1985, Caribaetis Kluge 1992a and Spiritiops Lugo-Ortiz & McCafferty 1998a; Asian taxa Indobaetis and Papuanatula Lugo-Ortiz & McCafferty 1999a. Among Baetofemorata, this is Baetis javanicus Ulmer 1913 and some other Oriental species. No one representative of Nigrobaetis/g1 and Labiobaetis has the posterior seta.
All three known species of Indobaetis have the posterior seta; I. microfolius sp.n. has also unusual anterior seta (Fig. 58).
Lugo-Ortiz and McCafferty (1996b) proposed the "Baetodes complex" and stated that
"The Baetodes complex is a distinct, monophyletic grouping of Neotropical and southwestern North American baetine (Ephemeroptera: Baetidae) genera having subapical setae on the lateral margin of the tarsal claws of the larvae and a distinct distomedial projection on the basal segment of the genital forceps of male
adults". Here under the "subapical seta" they mean posterior seta, and under the "basal segment" they mean unistyliger (which bears gonostylar muscle and often has distomedian projection). These authors ignored
Indobaetis and other Asian taxa, for which the posterior seta had been described. Their opinion about status of this character contradicts their previously expressed opinion, that
"The presence or absence of ... unpaired subapical setae on the larval tarsal claws are variable among species of other baetid genera, and we do not consider these characters to be of generic significance
..." (Lugo-Ortiz et al. 1994). Basing on this statement, they regarded
Fallceon Waltz & McCafferty 1987b (characterized by absence of the posterior seta) and
Caribaetis Kluge 1992a (characterized by presence of the posterior seta) to be synonyms (Lugo-Ortiz et al. 1994). In spite of the fact that presence of posterior seta is not enough to prove holophyly of the
"Baetodes complex", this character should not be ignored at all. Particularly, all species of
Fallceon have conservative combination of characters: claws have no posterior setae and frons forms a keel (see
2.2), while all species of Caribaetis have claws with posterior seta and flat frons; these characters allow to separate two distinct taxa
Fallceon and Caribaetis (Kluge 1992a, b). Uniting Caribaetis and
Fallceon to one genus, Lugo-Ortiz et al. (1994) did not report any characteristics for this genus, other than
"there are no significant differences in the
mouthparts" (which actually are in the both taxa plesiomorphic and indistinguishable from Nigrobaetis/g2) and
"presence of a distinct costal hook in the hindwings". Situation with the costal hook of the hind wing should be clarified. All species of
Fallceon and Caribaetis really have this costal hook. But these authors contradicted themselves, when established a new species
Fallceon nikitai McCafferty & Lugo-Ortiz 1994, which differs from Fallceon poeyi (Eaton 1885) by a single character—presence of the costal hook. Actually, lectotype of
F. poeyi has the costal hook (Kluge 1992b: Figs 8, 9 
), as well as all other specimens of the type series; thus,
F. poeyi = F. nikitai, syn.n. If Fallceon is treated as a genus,
Caribaetis also should be a genus (stat.n.), and the following binomina are valid:
Caribaetis planifrons (Kluge 1992) comb.n. (originally in Baetis),
Caribaetis alcarrazae (Kluge 1992) comb.n. (originally in Baetis) and
Caribaetis grandis (Gonzalez-Lazo & Salles 2007) comb.n. (originally in
Fallceon).
2.8. Scales on larval abdominal terga. Initially, type of scales was used to divide the paraphyletic genus
Baetis in its traditional sense into natural species groups (Müller-Liebenau 1969). Wide translucent scales on larval abdominal terga and some other parts of the body are characteristic for Baetidae, being not found in other taxa; probably, plesiomorphic condition of scale nests is trapezoid, with operculae on corners [Kluge 2004:
Turbanoculata (12)]. Such scales are present in many Protopatellata and many Baetovectata-non-Baetofemorata, particularly in all Nigrobaetis/g1. Among
Indobaetis, such scales are present in I. costai and I. starmuehlneri
(Fig.
9; Müller-Liebenau & Morihara 1982: Figs 4, 6 ), while in
I. microfolius sp.n. scale nests are diminished and lack operculae (Fig.
65). In Labiobaetis scale nests are semicircular, without operculae; this type of scale nests occurs also in such non-related taxa as Baetosternata and
Cloeoninae.
2.9. Presence of posterior prolongation of larval paraproct. Paraproct is a paired ventral sclerite of the 10th abdominal segment, which is the true last segment of insect body (Kluge 2004). In most Baetidae larval paraproct terminates posteriorly by a well-expressed denticulate margin, whose denticles are directed posteriorly; shape of denticles is often species-specific. Takobia/g1 (incl. Alainites, Acerbaetis) and formerly known species of Indobaetis have a prolongation of paraproct, stretched on posterior side of the 10th abdominal segment; margins of this prolongation bear denticles, and its apex is especially densely denticulate. Till recently, this character was regarded to be a synapomorphy of Indobaetis and Takobia/g1 (incl. Alainites, Acerbaetis), not found in any other taxa. However, it is present also in some species of Papuanatula Lugo-Ortiz & McCafferty 1999a. While in all species of Takobia/g1 (incl. Alainites, Acerbaetis) larval paraproct has similar structure, being well-expressed, regularly denticulate and produced into a rather wide posterior prolongation (Fig. 36), in Indobaetis and Papuanatula structure of larval paraproct is different and highly varies among species: in some species of Papuanatula posterior margin of paraproct is well-expressed and regularly denticulate, without prolongation (as in most Baetidae); in I. costai, I. starmuehlneri and some undescribed species of Papuanatula posterior margin of paraproct is only partly expressed and bears a narrow, arched, denticulate prolongation (Figs 37–39); in I. microfolius sp.n. and some undescribed species of Papuanatula paraproct has no distinct posterior margin, but gradually turns to membrane which surrounds the anal opening (Fig. 72).
2.10. Pose of subimaginal gonostyli developing in larva. Significance of this character for baetid systematics have been well demonstrated (Novikova & Kluge 1987, 1994; Kluge 1992a, b, 2004; Kluge & Novikova 2011); but most authors ignore this character, so it is still unknown for many species. In all examined Protopatellata and Anteropatellata-non-Baetovectata developing gonostyli are directed laterally («Cloeon-type» and «Afroptilum-type») (52 species examined). In all examined Baetovectata developing gonostyli are directed either caudally («Nigrobaetis-type» and «Callibaetis-type»), or caudally-medially («Baetis-type»), or medially («Labiobaetis-type»).
The «Labiobaetis-type» of gonostyli folding means that developing subimaginal gonostylus is bent within vestige of larval protogonostylus in such a way, that its apex is directed medially, and its most posterior point is not the apex, but a convex lateral side of gonostylus (Figs 28, 77). Such gonostyli folding is found in several taxa of Baetovectata-non-Baetungulata, Baetungulata-non-Baetofemorata and Baetofemorata, that testifies about independent origin of this type of gonostyli folding.
Among Baetovectata-non-Baetungulata, the «Nigrobaetis-type» of gonostyli folding occurs in Cloeodes Traver 1938 (15 species examined) and Waltzoyphius Lugo-Ortiz & McCafferty 1995 (1 species examined); the «Labiobaetis-type» occurs in Paracloeodes Day 1955 (2 species examined), Apobaetis Day 1955 (1 species examined) and Rivudiva Lugo-Ortiz & McCafferty 1998a (2 species examined).
Among Baetungulata-non-Baetofemorata, most taxa, including all Nigrobaetis/g1, have the «Nigrobaetis-type» of gonostyli folding (Fig. 76); the «Labiobaetis-type» occurs in Labiobaetis (36 species examined), Papuanatula (3 species examined), Mystaxiops venatoris McCafferty & Sun 2005, Echinobaetis phagas Mol 1989, Pseudopannota Waltz & McCafferty 1987a (1 species examined) and Acerpenna Waltz & McCafferty 1987b (1 species examined) (Fig. 77). Among Indobaetis, I. costai has the «Labiobaetis-type» (Figs 28, 29), while for I. starmuehlneri and I. microfolius sp.n. this character is unknown.
Among Baetofemorata, most taxa have the «Baetis-type» of gonostyli folding, but Acentrella/fg1 has the «Labiobaetis-type» (Kluge & Novikova 2011).
2.11. Sterno-styligeral muscle. Initially, mayfly genitals have an unpaired sterno-styligeral muscle, whose contraction bends styliger ventrally and at the same time rotates penial arms, which protrude penis (Kluge 2004). In Baetidae median part of styliger is reduced, so that the initially unpaired styliger is transformed to a pair of separated unistyligers, each bearing one gonostylus and containing the muscle—adductor of gonostylus (Kluge & Novikova 2011). Unistyliger looks like a limb segment, so some authors wrongly take baetid unistyligers for the first segments of gonostyli (actually gonostyli of mayflies, as well as abdominal styli of any Hexapoda, never have intrinsic muscles). While unistyligers of all Baetidae are externally similar, their possibilities are different: in some taxa they are able to adduct under action of the unpaired sterno-styligeral muscle; in some taxa the sterno-styligeral muscle is retained, but unable to move unistyligers; in some taxa the sterno-styligeral muscle is lost. Loss of the sterno-styligeral muscle took place repeatedly in some taxa, both among Protopatellata and among Anteropatellata-Baetovectata. In some cases presence or absence of this muscle characterizes a high-rank taxon. In Indobaetis the sterno-styligeral muscle is retained (Figs 24, 54), as well as in all Nigrobaetis/g1; in contrast to them, in all Labiobaetis and Papuanatula the sterno-styligeral muscle is completely lost.
The sterno-styligeral muscle (which terminates on the ventral surface of the body) is often thin, translucent and poorly visible; it should not be confused with the paired intersegmental muscle, which is always well developed (Fig. 24) and terminates deeper, on the common base of paraprocts (Kluge & Novikova 2011).
2.12. Number of tarsal segments. The taxon Tetramerotarsata is characterized by reduction of number of tarsomeres of middle and hind legs of subimago and imago: 1st tarsomere (synsclerotic with tibia, as characteristic for Ephemeroptera) is completely fused with 2nd tarsomere, so that total number of tarsomeres is 4 (including the proximal one, synsclerotic with tibia)
(Fig.
11). On fore leg, tarsus usually retains all 5 tarsomeres; among them, 1st tarsomere is strongly shortened [Kluge 2004: paragraph
"Liberevenata (3)"]. On fore leg of male imago (but not subimago) 1st tarsomere is always well expressed, being separated from tibia by a longitudinal groove which provides rotation of the tarsus (Kluge 2004:
Figs 10C–F). On fore leg of male subimago, as well as on fore leg of female subimago and imago, 1st tarsomere can be poorly expressed, being synsclerotic with tibia and strongly shortened. In male it is always well separated from 2nd tarsomere
(Fig.
6). On fore leg of female imago and subimago 1st tarsomere is usually well separated from 2nd tarsomere, in the same way as on fore legs of male
(Fig.
1; Kluge 1997: Fig. 9 
). In contrast to this, in
Indobaetis 1st and 2nd tarsomeres of female fore legs are completely fused together
(Fig. 2–4,
5
), in the same way as on middle and hind legs. Formerly, such condition was known only for
Siphlaenigma janae Penniket 1962 and was regarded to be peculiar for Siphlaenigmatidae, which is the sister taxon to Liberevenata (Kluge 1997, 2004). Presence of such structure in Indobaetis means, that it repeatedly appeared in non-related taxa within Tetramerotarsata.
2.13. Microlepides on subimaginal tarsus. The term "microlepide" was introduced by Kluge & Novikova (2011: 4), but had not been illustrated. Here are shown microtrichiae and two types of microlepides—pointed and blunt ones (Figs 5–8, 11–17). Texture of subimaginal tarsi can be examined either from subimagoes, of from subimaginal exuviae, or from mature nymphs ready to molt to subimago (Fig. 4). Texture of fore legs of male, fore legs of female and other legs can be different, while texture of middle and hind legs of both sexes is usually identical. In the case, when a most part of tarsal segment is covered by blunt microlepides, its basal and/or apical parts can be covered by pointed microlepides (Figs 5, 12). In some mayfly taxa all tarsal segments are covered by microtrichiae, like tibia and other parts of leg. Imaginal tarsus can have texture different from the subimaginal one; often imaginal texture is poorly expressed.
In all Baetidae subimaginal tarsi are covered by microlepides; microtrichiae can be present on first tarsomere only. In Baetidae other than Baetungulata (Protopatellata, Cloeoninae and others) all microlepides are pointed. Various taxa of Baetungulata usually have either all tarsomeres covered by pointed microlepides, or terminal tarsomere covered by pointed microlepides and other tarsomeres covered by blunt microlepides, or all tarsomeres covered by blunt microlepides.
Texture of subimaginal tarsi of Indobaetis is similar to that of some species of Nigrobaetis/g1 and Labiobaetis.
In all examined Baetungulata-Baetofemorata all tarsomeres of all legs of both sexes are covered by blunt microlepides; pointed microlepides can be present only on basal and/or apical parts of some tarsomeres.
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