Baetiella imanishii 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 : 572-574

Baetiella imanishii Braasch, 1983

( Figs 48–60 )

Material examined. 3 larvae, INDIA, Arunachal Pradesh, Lower Subansiri, Pa stream, 27.74791 N, 94.03462 E, 284 m, 14.vi.2017, colls. K. A. Subramanian & M. Vasanth (Reg. No. I /E/249); 2 larvae, Arunachal Pradesh, Lower Subansiri district , Rashpothar , ca 45 km SE of Tamen, outskirts of TVWls, Parsen River , 27.713413 N, 94.179297 E, 475 m, 19.ix.2016, coll. Bikramjit Sinha (Reg. No. I /E/250).

Mature larva. Body length 4.5–5.0 mm ( Fig. 48 ), cerci 3.5–4.0 mm, median caudal filament absent.

Head. Antennae light brown, approximately 1.5 times the width of head; dorsal surface of scape and pedicel without fine setae. Labrum ( Fig. 50 ) rectangular, approximately 2.0 times wider than long; anteromedian notch deep with a small rounded lobe at the base, and each side with one medial long seta and a row of 7 robust, simple submarginal setae, fine and simple setae scattered posteriorly; ventrally bordered with feathered setae along the anterior margin. Hypopharynx ( Fig. 51 ) with lingua rounded and superlinguae broadly truncate, covered with abundant fine setae. Left mandible ( Fig. 52 ): incisors fused with 7 denticles, prostheca robust with 4 blunt and 3–4 acute denticles apically. Right mandible ( Fig. 53 ): incisors with visible fusion line, outer incisors with 3 denticles and inner incisors with 4 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. 54 ) with three canines and one dentiseta on crown of galealacinia, a row of 4–5 long basal setae and basis of galealacinia without hump seta; maxillary palpus 2-segmented and terminal segment shorter than basal segment and with a small tip at apex. Labium ( Fig. 55 ): glossae shorter than paraglossae, with a row of 7–8 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 a distinctive tip at apex; the 2nd segment with an innerapical lobe; dorsal surface with numerous pores on the basal segment.

Thorax. Coloration pale yellow, dorsum without tubercles. Posterior margin of metanotum with a protuberance medially ( Fig. 48 ). Hindwing pads absent. 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 long and simple setae on dorsal margin, approximately 1/3 to 1/2 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 3–4 robust, blunted setae ventrally increasing in length towards apex ( Figs 56–57 ); tarsal claw with a row of 6–7 denticles and a pair of bowed subapical setae ( Fig. 58 ). All legs without coxal gill.

Abdomen. Dorsally pale yellow. Posterior margin of terga I–X each with a single posteromedian protuberance ( Figs 48–49 ); terga surface scattered with round scale-like and posterior margin with blunt denticles. Abdominal sterna generally yellowish-white; surface of sterna V–IX with scattered pointed setae posterior margins of sterna I–IV smooth without any denticles or scale-like setae, but sterna IV–IX with blunt denticles. Gills on segments I–VII, oval and without tracheation, surface scattered with numerous pores, margin smooth with fine simple setae, coloration white or reddish depending on the type of habitats ( Fig. 59 ). Paraproct with numerous pores on surface and 5–6 oval scale-like setae along the inner margin ( Fig. 60 ). Median caudal filament reduced to one segment, cerci subequal to the body length ( Fig. 48 ).

Diagnosis. Baetiella imanishii can be distinguished from other species of this genus by the following combination of characters: (i) all posteromedial protuberances on terga single ( Fig. 48 ); (ii) tergum X with a posteromedian protuberance ( Fig. 49 ); (iii) dorsum of labrum with a row of 7 robust submarginal setae ( Fig. 50 ); (iv) 2nd segment of labial palp with small inner-apical lobe ( Fig. 55 ); and (v) inner margin of paraprocts with oval scale-like setae ( Fig. 60 ).

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

Remarks. Shi & Tong (2015) argued that B. imanishii should be considered nomen dubium since it was established by Braasch (1983) based on the description of an unnamed species of Baetiella provided by Uéno (1955), who described it based on a single larva with no holotype designation. However, since a series of larval material broadly in agreement with the description provided by Uéno (1955) was collected in the present investigation, we do not agree with the proposal made by Shi & Tong (2015).

Figures

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

FIGURES 48–60. Larva of Baetiella imanishii Braasch, 1983. 48. Dorsal view; 49. Abdominal terga IX–X; 50. Labrum; 51. Hypopharynx; 52. Left mandible; 53. Right mandible; 54. Maxilla; 55. Labium; 56. Foreleg; 57. Hind leg; 58. Hind tarsal claw; 59. Gill V; 60. Paraproct.