Caenis maduraiensis Balasubramanian and Muthukatturaja, new species

(Figs. 1–3, 5–30)

Type material. Holotype (in ethanol): male imago (reared from nymph) (Reg.No. SRC/ ZSI-I/E 469) from India, Vandiyur pond, Madurai district, Tamil Nadu state, 9.viii. 2019, 124 m, 09°54’51” N, 78°10’52” E, Balasubramanian & Muthukatturaja Cols. Paratypes (in ethanol): one female imago (reared from nymph) (Reg.No. SRC/ ZSI-I/E 470) and 5 mature nymphs (Reg.No. SRC/ ZSI-I/E 471), same data as holotype. Balasubramanian & Muthukatturaja Cols.

Additional material (ZMTC). 156 male imago (reared from nymph), 254 female imago (reared from nymph) and 245 mature nymphs, India, Vandiyur pond, Madurai district, Tamil Nadu state, 19.viii. 2019, 124 m, 09°54’51” N, 78°10’52” E, Balasubramanian & Muthukatturaja Cols.

Diagnosis. Caenis maduraiensis sp. nov.: Nymph: (i) anterior margin of labrum with row of long bipectinate setae laterally and a group of highly fringed setae behind emargination; (ii) fore femora with transverse row of bifid spines; middle and hind femora with sparse bifid spines; (iii) hind claw long, slender and hooked with row of denticles; (iv) abdominal tergum II with pointed medial projection and pointed teeth on the posterior margin. Imago: (i) prosternal triangle with slightly concave sides, tip acutely pointed; (ii) tarsomere I extremely short; (iii) tarsomere II apically with tongue-shaped projections on single side; (iv) apical part of forceps narrowed to the tip, with a long apical spine, and few trichomes on surface; (v) cross veins of forewing arranged singly except in R 1 and R 4; (vi) MP forked at near 1/3 of distance from base to margin; (vii) fore tibia two times longer than femur and (viii) female subanal plate apically truncated.

Mature nymph (in 95% ethanol) (Figs. 1, 5–19): Body length (excluding cerci) 3.1–3.4 mm; cerci length 3.5–4.0 mm; median caudal filament 4.2–4.5 mm; length of head 0.4 mm; width of head 0.7 mm; antennae length 1.3 mm; length of fore femora/ tibia/ tarsi/ claw (mm) 0.7/0.5/0.3/0.2; length of middle femora/ tibia/ tarsi/ claw (mm) 0.6/0.37/0.25/0.18 and length of femora/ tibia/ tarsi/ claw (mm) viz., 0.65/0.6/0.4/0.15. General body coloration yellowish brown dorsally and pale ventrally, mature specimens generally paler; legs pale brown. Head brownish yellow; scape and pedicel of antennae pale brown without hairs, flagellum translucent; labrum (Fig. 5) broadly emarginated, dorsum with long setae, anterior margin with row of bipectinate setae longer laterally and a group of highly fringed setae behind emargination; mandibles (Figs. 6, 7) with broad incisors, outer margin of mandibles with long thin setae, left mandible with 7 thin setae below the molar, with elevated hump between prostheca and molar; maxillae (Figs. 8, 9) with 3 prominent teeth on galea–lacinia, ventral base of inner margin of galea with tuft of thin setae, distal portion of cardo with cluster of bipectinate stout setae, maxillary palp 3 segmented, segment I broad, segment I and II subequal in length, segment III longer, inner margin of segment III with row of 13 bipectinate setae; hypopharynx (Fig. 10): anterior margin of lingua with long setae, superlingua with small hair-like setae at anterior margin; labium with glossae (Fig. 11) ovate with stout spines at outer margin, mesal margin of glossae with thin setae, inner and outer margin of paraglossae with thin spines directed anteriorly, labial palp 3 segmented, segment II slightly longer than segment I, segment III short; outer margin of segment II with stout spines, outer margin of segment I with row of bipectinate setae, segment III triangular with 2 rows of stout setae ventrally, inner margin of segment III with row of stout spines. Thorax brownish yellow; lateral margins of pronotum convex, anterolateral margins with pair of spine-like setae and wider than posterolateral margins. Legs pale brown covered with scales, tibiae and tarsi light pale. Foreleg (Fig. 12): trochanter with transversal row of stout spines; outer margin of femur with few setae and spines, near ½ of dorsal surface with transversal row of bifid spines, inner margin with few stout spines, ¼ of dorsal surface with few long hairs; tibia with 3 bifid spines at mesal margin, inner distal margin with long bipectinate setae; few long hairs on tibia; tarsi with row of stout spines on inner margin, mesal margin with bipectinate spine; few long hairs on tarsi; claw long, slender and slightly hooked. Middle leg (Fig. 13): trochanter with two bifid spines; outer margin of femora with long spines, ½ of inner margin with stout spines and remainder with bifid spines, dorsal surface with sparse bifid spines; inner margin of tibia with row of stout spines; ½ of tarsi with short bipectinate setae at mesal margin, claw long, slender and slightly hooked. Hindleg (Fig. 14): trochanter with bifid spine; inner and outer margin of femur with long spines, ½ of dorsal surface with few bifid spines; inner margin of tibia with row of stout spines, outer margin with thin setae; tarsi similar to midleg; claw (Fig. 15) long, slender and hooked with row of denticles. Abdomen. Terga VII–X yellowish brown; tergum II with pointed medial projection and pointed teeth on the posterior margin; posterior margin of terga VII–IX with row of long setae; abdominal sterna III–IX pale brown. Gills (Figs. 16–19): pale brown; gill I (Fig. 16) 2-segmented, distal segment 4 times longer than proximal segment; gill II (Fig. 17) brown, covered with scales; margins evenly covered with long setae, inner margin with row of fringed setae; gills 3–6 (Figs. 18, 19) roughly triangular and with more than 15 multifid fimbriae with more than 2 branches; pigmented areas of the gill surface alternating with non-pigmented transparent tracheae. Cerci pale brown with whorls of setae in each segment.

Male Imago (in alcohol) (Figs. 2, 20–27): body length, 2.2–2.5 mm; cerci length, 8.8–9.1 mm; terminal filament, 9.6–9.9 mm; length of head 0.15 mm, width of head 0.5 mm; length of antenna 0.5 mm; length of forewing 1.85–2.05 mm; width of forewing 1.0– 1.3 mm; dorsal diameter of eye 0.1 mm; distance between compound eyes 0.125 mm; length of segments in foreleg femur/ tibia/ tarsus (mm): 0.45/0.9/0.6; length of tarsal segments 1 to 5 (mm): 0.03/0.28/0.12/0.11/0.06. Head (Fig. 20) pale brown, anterior margin and area around antennal base pale brown; scape and pedicel of antennae pale brown, flagellum translucent. Thorax yellowish brown; prosternal triangle with slightly concave sides, tip acutely pointed (Fig. 21). Legs: foreleg (Fig. 23–25) pale brown, middle and hindleg translucent; fore femur brown, tibia washed brown and two times longer than femur; tarsomere I extremely short; tarsomere II apically with tongue-shaped projections on single side; tarsomeres II–IV provided with short spines (Figs. 24–25); segment V short. Wings: Forewings (Fig. 22) oval, with few cross veins; cross veins arranged singly except in R 1 and R 4; two cross veins at near ½ of R; MP forked at near 1/3 from base; CuA not forked. Veins C and Sc brown basally and washed brown distally, remaining veins translucent.Abdomen: tergum I–VI pale brown remaining terga translucent; sterna whitish. Genitalia (Fig. 26) pale brown, penis lobes completely fused and produced laterally; styliger sclerite broad with short apophyses; forceps slender, apical part narrowed to the tip, with a long apical spine, and many trichomes on surface (Fig. 27); cerci and terminal filament translucent with whorls of setae in each segment.

Female Imago (in alcohol) (Figs. 3, 28–30): body length, 4.3–4.6 mm; cerci length, 3.2–3.5 mm; terminal filament, 4.0– 4.3 mm; length of head, 0.3 mm, width of head, 0.8 mm; length of antenna, 0.6 mm; length of forewing, 3.2–3.5 mm; width of forewing, 1.4–1.7 mm; distance between compound eyes, 0.58 mm; dorsal diameter of eye, 0.12 mm; length of segments in foreleg femur/tibia/tarsus (mm): 0.52/0.73/0.63; length of tarsal segments (mm): 0.035/0.35/0.12/0.15/0.075. Head (Fig. 28) pale brown; anterior margin and area around antennal base pale brown; scape and pedicel of antennae pale brown, flagellum translucent. Thorax yellowish brown; prosternal triangle with concave sides, tip acutely pointed (Fig. 29). Legs: foreleg pale brown remainders translucent; tarsomere II much longer than others. Wings: veins C and Sc brown basally and washed brown distally, remaining veins translucent. Abdomen: terga I–VI pale brown remaining terga translucent; sterna whitish; cerci and median terminal filament translucent; posterior margin of sternum IX truncated (Fig. 30).

Etymology. The species name maduraiensis refers to the locality, Madurai, Tamil Nadu where the new species was collected.