Tenuibaetis arduus ( 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 : 522-526

Tenuibaetis arduus ( Kang & Yang, 1994)

( Figs 7A–C , 8A–F , 9A–G )

Baetis (Tenuibaetis) arduus in Kang et al n. sp. 1994: 29

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

Tenuibaetis arduus Fujitani, Hirowatari & 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, 11.III.2018, Coll. Bikramjit Sinha (Reg. No. I /E/331) ; 2 larvae, INDIA, Arunachal Pradesh, Tawang district, Nuranang falls, Jang , 27°35′23″ N, 91°58′54″E, 07.III.2018, Coll. Bikramjit Sinha (Reg. No. I /E/539) .

Description. Mature larva ( Figs 7A–C ). Body length 5.3–5.6 mm; cerci length 2.5–2.7 mm; paracercus length 1.5–1.8 mm; antenna 1.1× as long as head capsule length.

Coloration ( Figs 7A–C ). Head dark brown medially pale with a pair of dark spots; base of clypeus pale yellow. Thorax brown with bright median, dorsal suture, mesothorax medially with bright striation and abdomen dorsally dark brown with two dark spots in medial area, abdominal segment IX with U-shaped pale white striation, segment X brownish white. Head, thorax and abdomen ventrally brown, somewhat brighter than dorsally. Legs light brown; femur dorsally pale and apical margin dark brown, distomedially dark brown; claws distally dark brown; caudal filaments brown.

Morphology. Antenna ( Fig. 8A ). Scape and pedicel sub-cylindrical, flagellum with rounded spines apically and fine, simple setae on apex of segments.

Labrum ( Fig. 8B ). Subrectangular with length 0.7× 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+3 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. 8D ). Incisors fused. Outer and inner set of denticles with four 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 set of denticles with three 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 slender. Apex of mola tuft of setae present. Both mandibles with lateral margins almost straight; basal half with fine, simple setae scattered over dorsal surface.

Hypopharynx ( Fig. 8C ). Lingua about as long as superlingua; lingua longer than wide; apically triangular with medial tuft of stout setae; distal half not expanded. Superlingua with distal margin straight; lateral margins rounded; fine, long, simple setae along distal margin; short, pointed setae along lateral margin.

Maxilla ( Fig. 8E ). Galea-lacinia with one simple, robust apical seta under the crown. Inner dorsal row of setae with three dentisetae, distal dentiseta, tooth-like; middle dentiseta biserrate and proximal dentiseta, furcation strongly developed and abducted. Medially with one feathered spine-like seta and 4–5 long, simple setae. Maxillary palp 1.5× as long as length of galea-lacinia; two segmented. Segment I equal in length to segment II. Apex of segment II rounded without nipple. Setae on maxillary palp fine and simple setae over surface of segments I and II.

Labium ( Fig. 8F ). Base of glossa broad, towards narrowing apex; paraglossa shorter; inner margin with eight spine-like setae increasing the length of distally; apex with three long and one medium, robust, pectinate setae; outer margin with five long, spine-like setae; ventral surface with fine, short setae. Paraglossa subrectangular, slightly curved inward; apex rounded, with three rows of long, simple, robust, pectinate setae apically; dorsally with three medium, simple setae; ventrally long setae near inner margin. Labial palp 3 segmented; segment I 0.7× of length of segments II and III combined. Segment II slightly produced inward to form a moderately expanded lobe at distal corner, dorsally with a row of 5–6 long, simple setae; Segment III conical, slightly pointed apically; covered with short, spine-like simple setae. Segments I, II and III with fine simple setae scattered over dorsal surface.

Hind wing pads. Present, well developed.

Foreleg ( Fig. 9A ). Ratio of foreleg segments 1.4:1.0:0.8:0.2. Femur. Length ca. 2.5× maximum width. Dorsal margin with a row of ca 21–22 long, curved, apically rounded setae; length of setae 0.22× maximum width of femur. Apex rounded with a row of short, stout, pointed setae, many stout lanceolate setae on lateral surface. Villopore well developed. Dorsal margin of tibia with a row of fine simple setae; ventral margin with a row of 6–9 spine-like setae and a tuft of long, fine, simple setae; anterior surface scattered with stout, spatulate setae. Tibia. 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. Inner margin with a row of spine-like setae. Claw distally pointed and curved ( Fig. 9C ) with one row of 11 denticles and 5–6 stripes apically.

Terga ( Fig. 7A ). Surface with scattered V-shaped scale bases and scattered fine, simple setae. Posterior margin of each segment a pair of small spots; tergum IX pale white with row of V- shaped spines.

Gills ( Figs 9D–F ). Single lamellate gills present on segments I–VII. Margin with small denticles intercalating fine, simple setae. Tracheae obscure.

Paraproct ( Fig. 9G ). Distally not expanded, with 13–14 marginal stout spines. Surface scattered with V-shaped scale bases, micropores fine, simple setae, with a patch of notched scales. Cercotractor with medium, marginal spines.

Diagnosis: Tenuibaetis arduus can be differentiated by the following combination of characters: (i) labrum deeply cleft without “V” shaped marking medially ( Fig. 8B ); (ii) abdominal posterior marginal spines blunt ( Fig. 7A ); (iii) color pattern of thorax and abdomen distinct ( Figs 7A–C ); (iv) tracheation of gills obscure ( Figs 9D–F ); (v) claw with one row of 11 denticles ( Fig. 9C ).

Distribution: Taiwan and India (Arunachal Pradesh).

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

Figures

FIGURES 7. Larva: Tenuibaetis arduus, A, color pattern, dorsal view (arrow indicated U shaped spines); B, habitus, lateral view; C, color pattern, ventral view.

FIGURES 8. Larva: Tenuibaetis arduus, A, head, frontal view; dorsal view: B, labrum; C, hypopharynx; D, left mandible (arrow indicated denticles); E, maxilla; F, labium.

FIGURES 9. Larva: Tenuibaetis arduus, dorsal view: A, foreleg; B, hind leg; C, claw; D, gill I; E, gill IV; F, gill VII; G, paraproct.