Tenuibaetis Kang & Yang, 1994

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.), Zootaxa 5277 (2), pp. 201-258 : 207-208

publication ID	https://doi.org/ 10.11646/zootaxa.5277.2.1
publication LSID	lsid:zoobank.org:pub:73ED69F3-3887-460D-86DE-C9F1302C8EC3
DOI	https://doi.org/10.5281/zenodo.7893476
persistent identifier	https://treatment.plazi.org/id/03F487D0-A370-4D49-A2DB-FF43FA24EBC1
treatment provided by	Plazi
scientific name	Tenuibaetis Kang & Yang
status

Treatment

Subgenus Tenuibaetis Kang & Yang View in CoL View at ENA (in Kang, Chang & Yang) 1994

( Figs 1–284 View FIGURES 1–4 View FIGURES 5–12 View FIGURES 13–21 View FIGURES 22–30 View FIGURES 31–32 View FIGURES 33–41 View FIGURES 42–43 View FIGURES 44–46 View FIGURES 47–49 View FIGURES 50–51 View FIGURES 52–59 View FIGURES 60–68 View FIGURES 69–77 View FIGURES 78–82 View FIGURES 83–88 View FIGURES 89–91 View FIGURES 92–101 View FIGURES 102–111 View FIGURES 112–115 View FIGURES 116–124 View FIGURES 125–128 View FIGURES 129–134 View FIGURES 135–143 View FIGURES 144–145 View FIGURES 146–153 View FIGURES 154–159 View FIGURES 160–168 View FIGURES 169–180 View FIGURES 181–183 View FIGURES 184–190 View FIGURES 191–194 View FIGURES 195–201 View FIGURES 202–207 View FIGURES 208–210 View FIGURES211–214 View FIGURES 215–224 View FIGURES 225–229 View FIGURES 230–236 View FIGURES 237–241 View FIGURES 242–248 View FIGURES 249–252 View FIGURES 253–256 View FIGURES 257–264 View FIGURES 265–274 View FIGURES 275–278 View FIGURES 279–284 )

Species Baetis ursinus: Novikova 1991: 793 View in CoL ; Kluge 1997b: 193 (larva).

Subgenus Tenuibaetis Kang & Yang View in CoL (in Kang & Chang & Yang) 1994: 26 (larva).

Genus Tenuibaetis: Fujitani, Hirowatari & Tanida 2003: 126 View in CoL (imago, larva).

Type species: Baetis pseudofrequentus Müller-Liebenau 1985 .

Diagnosis. The subgenus Tenuibaetis is characterized only by a combination of characters, each of which is found in some other taxa of Baetofemorata.

Labial palp: 2nd segment is not significantly projected medially, 3rd segment is nearly symmetric, pointed, with both margins slightly convex ( Figs 23 View FIGURES 22–30 , 46 View FIGURES 44–46 , 82 View FIGURES 78–82 , 158 View FIGURES 154–159 , 194 View FIGURES 191–194 , 252 View FIGURES 249–252 , 281 View FIGURES 279–284 ). The same in the group lutheri of Baetis ; similar in Baetiella .

Larval legs differentiated: Femur of fore leg is wider than others, widest in proximal part; if cuticle of femur is pigmented, fore femur has large proximal blank lacking stout setae, while middle and hind femora have no such blank ( Figs 25–27 View FIGURES 22–30 , 47–49 View FIGURES 47–49 , 70–75 View FIGURES 69–77 , 129–131 View FIGURES 129–134 , 160–162 View FIGURES 160–168 , 188–190 View FIGURES 184–190 , 232–234 View FIGURES 230–236 , 253–255 View FIGURES 253–256 ). Among Baetis , the same in the group lutheri ; among other mayflies, similar shape of femora and the proximal blank of fore femur occur in certain Leptophlebiidae ( Kluge 2020: fig. 9; Kluge, Srinivasan et al. 2022: figs 64–66; Kluge, Vasanth et al. 2022: figs 27–29).

Stout setae on larval femora (either two-channel, or pseudo-bifurcate) are located not only near outer and inner sides, but also on middle area of anterior (dorsal) side ( Figs 31 View FIGURES 31–32 , 47–49 View FIGURES 47–49 , 83–88 View FIGURES 83–88 , 129–132 View FIGURES 129–134 , 160–162 View FIGURES 160–168 , 202 View FIGURES 202–207 , 232–234 View FIGURES 230–236 , 253–266 View FIGURES 253–256 View FIGURES 257–264 View FIGURES 265–274 , 279 View FIGURES 279–284 ). The same in many other mayflies, including certain species of Baetis groups vernus, buceratus, subgenus Rhodobaetis .

Scales on larval abdominal terga: Wide, in semicircular sockets ( Figs 199–200 View FIGURES 195–201 ). The same in many other Baetis , but not in the group lutheri .

Tergalii: All seven pairs present, oval; tergalius I often much smaller than others ( Figs 73 View FIGURES 69–77 , 184 View FIGURES 184–190 , 239 View FIGURES 237–241 ). The same in most other Baetis s. l. In Baetis (Tenuibaetis) sp. from Thailand, the first tergalius is relatively large ( Fig. 284 View FIGURES 279–284 ).

Larval pose. When swimming, larva does not stretch its legs along the body, but after short swimming passively falls down with its legs bent down and abdomen often bent on back ( Fig. 128 View FIGURES 125–128 ); larva of B. (T.) hissaricus bents its legs, but abdomen retains straight ( Kluge 1983, Novikova 1991). The same in Acentrella , Baetiella and some nonrelated mayflies (e.g. Ephemerellidae ), in contrast to majority of Baetis , which retain ability to swim stretching legs backward along the body.

Larval cuticular coloration: Varies from nearly uniformly brown ( Figs 184 View FIGURES 184–190 ) or diffusively maculated, to brown with contrasting V-shaped or transverse blank on mesonotum ( Fig. 28 View FIGURES 22–30 ) and contrasting blanks on abdomen; in this case abdominal tergum IV is lighter then neighboring ones ( Fig. 24 View FIGURES 22–30 ). The species name of the first described species, Baetis ursinus , was given as an allusion to the similarity of its dorsal V-shaped blank to the ventral white marking of the Asian bear ( Ursus thibetanus Cuv. )

Gonostyli. Male imaginal gonostylus with terminal (3rd) segment short ( Figs 42–43 View FIGURES 42–43 , 54–55 View FIGURES 52–59 , 98, 101 View FIGURES 92–101 , 112–114 View FIGURES 112–115 , 144–145 View FIGURES 144–145 , 181–183 View FIGURES 181–183 , 225, 227 View FIGURES 225–229 , 276–277 View FIGURES 275–278 ).

Sterno-styligeral muscle: Varies from vestigial with remnants of cross striation ( Figs 228–229 View FIGURES 225–229 ) to completely absent ( Fig. 145 View FIGURES 144–145 ).

Hind wing. Hind wing, if present, with two longitudinal veins and short costal projection ( Fig. 13 View FIGURES 13–21 ). The same in many other Baetis , in contrast to representatives having three veins or lacking costal projection.

Variability of hind wings. Most species of Tenuibaetis have hind wings as large as in most other species of Baetis s. l.; in this case larval protoptera are also well-developed ( Figs 13–14 View FIGURES 13–21 ). In female, hind wings are often somewhat smaller or at least narrower than in male ( Figs 34–35 View FIGURES 33–41 , 56–57 View FIGURES 52–59 , 109–111 View FIGURES 102–111 , 138–139 View FIGURES 135–143 , 178–179 View FIGURES 169–180 ).

In B. (T.) parvipterus ( Fujitani et al. 2011) hind wings of female are greatly diminished ( Fujitani et al. 2011: fig. 5b). In B. (T.) octomaculatus sp. n. hind wings of both sexes are diminished ( Fig. 15 View FIGURES 13–21 ), but larval protoptera are nearly as large as in the species with full-sized hind wings ( Figs 17, 19 View FIGURES 13–21 ); in female, imaginal hind wing is as small as its larval protopteron, so that it develops under larval cuticle without crumpling ( Figs 18–19 View FIGURES 13–21 ); in contrast to it, male hind wing is larger than protopteron and is crumpled before molt ( Figs 16–17 View FIGURES 13–21 ), as in most other mayflies and most other insects. Thus, in contrast to most other mayflies, in Tenuibaetis size of hind protopteron of larva does not allow to make conclusion about size of its imaginal hind wing.

In B. (T.) panhai Suttinun et al. 2022 and B. (T.) bialatus sp. n., hind wings are completely absent in both sexes ( Fig. 20 View FIGURES 13–21 ); larvae of these species have no any vestiges of hind protoptera ( Fig. 21 View FIGURES 13–21 ).

Characters common with other Baetis .

Femoral patch (villopore). Equally developed on all femora of larva ( Figs 230–231 View FIGURES 230–236 , 256 View FIGURES 253–256 ).

Subimaginal gonostyli folded under larval exuviae. Pose of the ́Baetis - type » or the ́Acentrella - type », i.e. with the 2nd and 3rd segments directed medially ( Kluge & Novikova 2011) ( Figs 241 View FIGURES 237–241 , 275 View FIGURES 275–278 ).

Texture of subimaginal tarsi. All tarsomeres of all leg pairs covered mostly with blunt microlepides ( Fig. 180 View FIGURES 169–180 ). The same in all other Baetofemorata (Kluge 2022).

Egg. Oval, chorion rugose, without regular relief ( Fig. 224 View FIGURES 215–224 ).

Distribution. Central and Eastern Asia: East Palaearctic and the Oriental Region.