Tenuibaetis inornatus ( Kang & Yang, 1994 )

Kubendran, T., Vasanth, M., Subramanian, K. A., Gattolliat, Jean-Luc, Selvakumar, C., Jabeen, Fatima & Sinha, Bikramjit, 2022, Two new species and two new records of the genus Tenuibaetis Kang & Yang, 1994 (Ephemeroptera: Baetidae) from Indian Himalaya, Zootaxa 5196 (4), pp. 511-534 : 526-529

Tenuibaetis inornatus ( Kang & Yang, 1994)

( Figs 10A–B , 11A–F , 12A–G )

Baetis (Tenuibaetis) inornatus in Kang et al. n. sp. 1994: 28

Baetiella inornata Waltz & McCafferty, 1997: 136 n. comb.

Tenuibaetis inornatus Fujitani, Hirowatari and Tanida 2003a: 127 n. comb.

Material examined. 1 larva, INDIA, Arunachal Pradesh, West Kameng district, Chakparang stream, Dirang Valley , 27°25′20″ N, 92°17′17″ E, 13.III.2018, Coll. Bikramjit Sinha (Reg. No. I /E/540) .

Description. Mature larva ( Figs 10A–B ). Body length 5.2 mm; cerci length 2.3 mm; paracercus length 1.2 mm; antenna 1.0× as long as head capsule length.

Coloration ( Figs 10A–B ). Head dark brown, medially pale white with a pair of dark spots; base of clypeus pale yellow ( Fig. 10B ). Thorax brown with bright medially, dorsal suture, mesothorax medially with bright yellowish and abdomen dorsally dark brown with two dark spots medial areas ( Fig. 10A ); abdominal segment IX–X pale white. Head, thorax and abdomen ventrally brownish white, somewhat brighter than dorsally. Legs light brown; femur dorsally pale and apical margin dark brown, distomedially dark brown; claws distally dark brown; caudal filaments brownish yellow.

Morphology. Antenna ( Fig. 10B ). Scape and pedicel sub-cylindrical, flagellum with rounded spines apically and fine, simple setae on apex of segments.

Labrum ( Figs 11A–B ). Rectangular with length 0.8× maximum width. Medial emargination of distal margin with a small, apically pointed process. Dorsally with many medium, fine, simple setae; submarginal arc of setae composed of 1+5 simple setae. Ventrally with marginal row of setae composed of lateral and anterolateral long, feathered setae and medial long, bifid, pectinate setae; ventral surface with two short, spine-like setae near lateral and anterolateral margin.

Right mandible ( Fig. 11D ). Incisors fused. Outer and inner sets of denticles with 4+4 denticles respectively. Prostheca stick-like, apically and distolaterally denticulate. Margin between prostheca and mola straight. Tuft of setae at apex of mola present.

Left mandible. Incisors fused. Outer and inner sets of denticles with 4+4 denticles respectively, plus one-minute, intermediate denticle. Prostheca robust, apically with small denticles and comb–shape structure. Margin straight between prostheca and mola. Subtriangular process long and slender, above level of area between prostheca and mola. Denticles of mola apically constricted. Tuft of setae at apex of mola present. Both mandibles with lateral margins almost straight; basal half with fine, simple setae scattered over dorsal surface.

Hypopharynx ( Fig. 11C ). Lingua about as long as superlingua; lingua longer than wide; apically triangular with medial tuft of hair-like setae; distal half not expanded. Superlingua with distal margin straight; lateral margins angulated; fine, long, simple setae along distal margin; short, pointed setae along lateral margin.

Maxilla ( Fig. 11E ). Galea-lacinia with two simple, robust apical setae under crown. Inner dorsal row of setae with three dentisetae, distal dentiseta tooth-like; middle dentiseta slender, biserrate and proximal dentiseta furcation strongly developed and abducted. Medially with one feathered spine-like seta and 4–5 long, simple setae. Maxillary palp 1.2× as long as length of galea-lacinia; two segmented. Segment II 1.2× longer than segment I. Apex of segment II rounded without nipple. Setae on maxillary palp fine and simple setae over surface of segments I and II.

Labium ( Fig. 11F ). Base of glossa broad, towards narrowing apex; paraglossa shorter; inner margin with 10–11 spine-like setae increasing the length of distally; apex with three long and one medium, robust, pectinate setae; outer margin with 5–6 spine-like setae increasing in length distally, base with small medium, simple setae. Paraglossa subrectangular slightly curved inward; apex rounded, with three rows of long, simple, robust, pectinate setae in apical area and 4 medium, simple setae in antero-medial area. Dorsally with a row of five long spine-like setae near inner margin. Labial palp 3-segmented; segment I 0.9× length of segments II and III combined. Segment II only slightly produced distolaterally; inner and outer margin with short and simple setae; dorsally with a row of spinelike medium simple setae; segment III conical, slightly pointed apically; covered with short, stout, spine-like setae. Segments I, II and III with fine simple setae scattered over dorsal surface.

Hind wing pads. Present, well developed.

Foreleg ( Fig. 12A ). Ratio of foreleg segments 1.4:1.0:0.7:0.3. Femur. Length ca. 3× maximum width; dorsal margin with a row of ca 20–21 long, curved, apically rounded setae; length of setae 0.25x maximum width of femur; apex rounded with a row 4–5 short, stout, pointed setae, many stout lanceolate along ventral margin; villopore well developed. Tibia. Dorsal margin with a row of short, stout, pointed setae, fine, simple setae; ventral margin with a row of short, spine-like setae, on apex one stout pointed, simple setae; anterior surface with scattered stout setae, lanceolate; tibio-patellar suture present on basal 2/3 area. Tarsus. Dorsal margin with a row of short, stout setae; ventral margin with a row of spine-like setae. Claw distally pointed and curved with one row of 12–13 denticles ( Fig. 12C ).

Terga ( Figs 10A–B ). Surface with scattered V-shaped scale bases and scattered fine, simple setae. Posterior spines of abdominal terga blunt, abdominal terga of each segment with a pair of small spots; tergum IX–X pale yellow.

Gills ( Figs 12D–F ). Single lamellate gills present on segments I–VII. Margin with small serration, simple setae. Gill I small; tracheae distinct.

Paraproct ( Fig. 12G ). Distally not expanded, with 11 marginal stout spines. Surface with V-shaped scale bases, microspores fine and simple, with a patch of scales. Cercotractor with medium, marginal spines.

Diagnosis: Tenuibaetis inornatus can be distinguished by the following combination of characters: (i) labrum deeply cleft with “V” shaped mark medially ( Figs 11A–B ); (ii) spines at posterior margin of abdominal terga blunt ( Fig. 10A ); (iii) gill I longer ( Fig. 12D ); (iv) claw with 12 denticles ( Fig. 12C ).

Distribution: Taiwan and India (Arunachal Pradesh).

Remarks: This species was originally described from Taiwan based on larvae ( Kang & Yang 1994). Presently, the new record of the larvae Tenuibaetis inornatus from Arunachal Pradesh is an extension of its species distributional range.

Figures

FIGURES 10. Larva: Tenuibaetis inornatus, A, color pattern, dorsal view; B, habitus, lateral view.

FIGURES 11. Larva: Tenuibaetis inornatus, dorsal view:A, labrum; B, labrum closer view (arrow indicated V shape marking); C, hypopharynx; D, left mandible; E, maxilla (arrow indicated dent-seta); F, labium.

FIGURES 12. Larva: Tenuibaetis inornatus, dorsal view A, foreleg; B, mid leg; C, claw; D, gill I; E, gill IV; F, gill V; G, paraproct.