Baetiella marginata Braasch, 1983

Vasanth, M., Selvakumar, C., Subramanian, K. A., Sivaramakrishnan, K. G. & Sinha, Bikramjit, 2020, New record of the genus Baetiella Uéno, 1931 (Ephemeroptera: Baetidae) from India with description of a new species and new records for five species, Zootaxa 4763 (4), pp. 563-578 : 574-575

Baetiella marginata Braasch, 1983

( Figs 61–75 )

Material examined. 8 larvae, INDIA, Arunachal Pradesh, Lower Subansiri district, Duskilo stream, 27.62776 N, 93.84365 E, 1662 m, 12.vi.2017, colls. K. A. Subramanian & M. Vasanth (Reg. No. I/E/251).

Mature larva. Body length 4.5–5.0 mm ( Fig. 61 ); cerci 4.0– 4.5 mm, median caudal filament with 15 segments.

Head. Antennae ( Fig. 62 ) light brown, approximately 2 times the width of head; dorsal surface of scape, pedicel and flagellum with a row of setae. Labrum ( Fig. 63 ) rectangular, approximately 2.0 times wider than long; anteromedian with a small rounded lobe at the base, and each side with one medial long seta and a row of 11 robust, simple submarginal setae, fine and simple setae scattered posteriorly; ventrally bordered with feathered setae along the anterior margin. Hypopharynx ( Fig. 64 ) with lingua rounded and superlinguae broadly truncate, covered with abundant fine setae. Left mandible ( Fig. 65 ): outer and inner incisors fused with 3 denticles medially, prostheca robust with 5 blunt and 2–3 acute denticles apically. Right mandible ( Fig. 66 ): outer incisor with visible fusion line, without denticles and inner incisors with 3 denticles, inner incisor margin smooth without fine setae, prostheca with denticles apically and distinctly more slender than the one on left mandible, edge between prostheca and molar smooth with no serration, molar plate-like. Maxillae ( Fig. 67 ) with three canines and three dentisetae on crown of galealacinia, a row of 4–5 long basal setae and basis of galealacinia with hump seta; maxillary palpus 2-segmented and terminal segment subequal to basal segment and with a small tip at apex. Labium ( Fig. 68 ) glossae shorter than paraglossae, with a row of 8–9 stout setae along the inner margin dorsally and 2 long robust blunt setae at the apex; paraglossae approximately 2 times wider than glossae, with 3 rows of setae ventrally and 2–3 stout acute setae along the inner margin dorsally; labial palpus 3-segmented, terminal segment conical with stout setae and a distinctive tip at apex, 3/4 of 2nd segment; 2nd segment with an inner-apical lobe and a row of 5–6 setae along the outer margin; dorsal surface with numerous pores on the basal segment.

Thorax. Coloration pale yellow with dark brown maculae on pronotum, dorsum without tubercles. Posterior margin of metanotum without protuberance medially ( Fig. 61 ). Hindwing pads reduced. Legs slightly paler than thorax, femora creamy shaded with light brown medially and a brown longitudinal stripe near dorsal margin, tibiae and tarsi brown. Femora with a row of short and simple setae on dorsal margin, approximately 1/4 of femur width; femoral villopore reduced; tibiae with irregular row of dense, fine, simple setae dorsally; tarsi with a row of sparse, fine, simple setae dorsally and a row of 6 robust, pointed setae ventrally increasing in length towards apex ( Figs 69–71 ); tarsal claw with a row of 6 denticles ( Fig. 72 ). All legs without coxal gill.

Abdomen. Dorsally pale yellow. Abdominal terga IV–IX light brown each with a pair of dark brown elongateoblique medioanterior sigilla. Posterior margin of terga without posteromedian protuberance ( Fig. 61 ); terga surface without round scale-like and fine setae, terga VI–IX posterior margin with blunt denticles. Abdominal sterna generally yellowish-white; posterior margins of sterna I–X smooth without any denticles or scale-like setae. Gills on segments I–VII, oval and without visible tracheation, surface scattered with numerous pores, margin smooth with fine simple setae ( Figs 73–74 ). Paraproct with numerous pores on surface and 10–12 stout setae along the inner margin ( Fig. 75 ). Median caudal filament reduced to 15 segments, cerci equal to the body length ( Fig. 61 ).

Diagnosis. Baetiella marginata Braasch, 1983 can be distinguished from other species of this genus by the following combination of characters: (i) vertex of head and dorsal surface of thorax without tubercles or elevation ( Fig. 61 ); (ii) abdominal terga without dorsal protuberance ( Fig. 61 ), surface of terga and sides of sterna each with numerous pores; (iii) hindwing pads minute; (iv) gills present on segments I–VII ( Fig. 61 ), oval and without tracheation, surface scattered with numerous pores on surface, inner margin smooth with long fine setae ( Figs 73–74 ); (v) paraproct with numerous pores on surface and 10–12 stout setae along the inner margin ( Fig. 75 ); and (vi) median caudal filament reduced to 15 segments ( Fig. 61 ).

Distribution. India (Arunachal Pradesh) ( Fig. 81 ) and Nepal.

Remarks. Braasch (1983) described Baetiella marginata based on the larvae from Nepal. Here we provide an improved larval description of B. marginata , based on fresh material from our collections. Our new data represent the first report of this species from India.

Figures

FIGURES 81. Distribution map of Baetiella in Arunachal Pradesh, India.

FIGURES 61–75. Larva of Baetiella marginata Braasch, 1983. 61. Dorsal view; 62. Antenna; 63. Labrum; 64. Hypopharynx; 65. Left mandible; 66. Right mandible; 67. Maxilla; 68. Labium; 69. Foreleg; 70. Midleg; 71. Hind leg; 72. Hind tarsal claw; 73. Gill IV; 74. Gill VII; 75. Paraproct.