Isonychia moyarensis Vasanth, Selvakumar and Subramanian

Vasanth, M., Selvakumar, C., Subramanian, K. A., Babu, R. & Sivaramakrishnan, K. G., 2019, A new record of the family Isonychiidae (Insecta: Ephemeroptera) from the Western Ghats, India with a description of new species, Zootaxa 4586 (1), pp. 162-170 : 163-169

Isonychia moyarensis Vasanth, Selvakumar and Subramanian n. sp

( Figs 1–28 )

Material examined. Holotype: larva, INDIA, Tamil Nadu, Nilgiri District, Moyar River, Mudumalai Tiger Reserve , Theppakadu , 11°34.787 N, 076°35.208 E, 864 m, 01.iv.2016, coll. R. Babu [ZSI/SRC-I/E 281] . Paratypes: 2 male imagoes, 1 female imago [ZSI/SRC-I/E 282] and 5 larvae [ZSI/SRC-I/E 283], coll. R. Babu, same data as holotype; 1 larva, Tamil Nadu, Coimbatore District, Mettupalayam , Kallar River , 11°20.293 N, 076°52.925 E, 386 m, 30.iii.2016, coll. R. Babu [ZSI/SRC-I/E 284] .

Description. Male imago. Body length 10–12 mm ( Fig. 1 ), forewing 10–11 mm ( Fig. 3 ), hindwing 4–5 mm ( Fig. 4 ).

Head: Blackish grey; ocelli blackish; antennae reddish brown; margin of transverse shelf reddish ( Fig. 2 ).

Thorax: Thorax pale yellow; pronotum pale yellow with submedian black maculae anterolaterally, posterior edge tinged with greyish band; mesonotum brownish yellow with a pair of submedian semilunar marks anteriorly and two long dark stripes laterally ( Fig. 2 ). Femur and tibia of forelegs brown; apices of tarsal segments brownish ( Fig. 5 ); middle leg pale white; femur and tibia tinged with yellow; tarsal segments pale ( Fig. 6 ); hind legs yellowish; femur, tibia and tarsi uniformly pale ( Fig. 7 ). Length (mm) of segments in forelegs: femora 1.5–2.0; tibia 2.1–2.3; tarsal segments 1.5–1.8 ( Fig. 5 ). Wings hyaline; forewing with longitudinal yellowish black maculae in costal, subcostal and median areas; anterior six cells in costal area dark yellow, cross veins in longitudinal bands and those fringing distal ½ of the posterior edges clouded with yellowish brown. Cubital and anal areas pale with few cross veins ( Figs 3–4 ).

Abdomen: Terga dark orange to reddish brown; terga I–IX with brownish maculae on lateral edges; terga VII and VIII with paired pale yellow submedian stripe ( Fig. 1 ). Sterna yellowish red; sterna IX pale yellow. Genitalia pale brown; penes hyaline, without serrations or large spines and with distal angles rounded; second segment of gonostylus uniformly convex ( Fig. 8 ). Caudal filaments pale yellow with dark brown distal edges of each segment.

Female imago. Body length 14–15 mm.

Head: Blackish grey; ocelli blackish; antennae reddish brown; margin of transverse shelf reddish.

Thorax: Thorax pale yellow; pronotum pale white with submedian black maculae anterolaterally, posterior edge tinged with greyish band; mesonotum brownish yellow with a pair of submedian semilunar marks anteriorly and two long dark stripes laterally. Femur and tibia of forelegs reddish brown; tarsal segments of foreleg pale with brownish posterior edges. General colour of middle leg pale white; femur and tibia tinged with yellow; tarsal segments pale; hind legs yellowish; femur, tibia and tarsi uniformly pale. Length (mm) of segments in forelegs: femora 1.3–1.5; tibia 1.6–1.8; tarsal segments 0.9–1. Wings hyaline; forewing with longitudinal reddish-brown bands.

Abdomen: Terga light orange to reddish brown; terga I–IX with brownish maculae on lateral edges; terga VII and VIII with paired pale yellow submedian stripe ( Fig. 10 ). Sterna pale yellow; segment X deeply cleft on the sterna ( Fig. 9 ). Caudal filaments pale yellow with dark brown distal edges of each segments.

Mature larva. Body length 12–13 mm, cerci 7–8 mm. ( Figs 11–28 )

Head: Clypeus entirely dark brown; frontal carina light, frons behind median ocellus dark; epicranium with light median longitudinal stripe; antennal segments dark brown ( Fig. 13 ), posterior edges yellowish. Labrum yellowish with thick hair like setae dorsally and apically ( Fig. 16 ). Labium pale yellow, glossae pointed apically, paraglossae slightly expanded laterally, apical segment of labial palp with rows of hair-like setae on outer margin ( Fig. 17 ). Mandibles dark brown with yellowish area, with three teeth on each incisor, prostheca well developed ( Figs 18, 19 ). Maxillae pale brown; terminal segment of maxillary palp with dense rows of hair-like setae ( Fig. 20 ). Lingua hypopharynx with anterolateral lobes, superlinguae weakly expanded, apically dense row of hair-like setae ( Fig. 21 ).

Thorax: Pronotum and mesonotum dark brown, with median longitudinal stripe; mesonotum with a pair of submedian semilunar marks anteriorly and two long dark stripes laterally ( Figs 11, 14 ). On each leg femur light, with two wide transverse dark brown bands; tibia and tarsus each with transverse brown band in middle ( Figs 22– 24 ); length (mm) of segments: foreleg 1.5, 1.7, 0.7 ( Fig. 22 ); middle leg 1.7, 1.3, 0.7 ( Fig. 23 ); hindleg 1.9, 1.0, 0.7 ( Fig. 24 ); dorsal claw with 8 denticles ( Fig. 25 ); ventral cleft of hind femur usually with 6 spines.

Abdomen: Abdominal terga dark yellow ( Fig. 11 ); terga II–IX with median dark brown maculae progressively larger with dark brown slanting streaks in lateral margins ( Fig. 11 ); abdominal sterna pale yellow ( Figs 12, 15 ); abdominal terga X pale yellow in anterior ¼ and dark brown in posterior ¾ ( Fig. 11 ); posterolateral projections on abdominal segments I – VII blunt and progressively longer those of segments VIII – IX, sharp and distinct ( Figs 11– 12 ); abdominal tracheal gills I – VII unbranched ( Figs 26–28 ); cerci dark brown with a dense row of long fine bristles along inner margin, paracercus light brown, ¾ of cerci length ( Figs 11–12 ).

Etymology. This species is named after the type locality, the Moyar River (tributary of Bhavani River), Nilgiri District, Tamil Nadu State, India.

Distribution. Tamil Nadu ( India).

Diagnosis. Imagoes of I. moyarensis is a member of the subgenus Isonychia s.s since the styliger between the gonostylii pedestals is strongly reduced, deeply separating the gonostyli pedestals ( Fig. 8 ). The penes lack serrations and large spines ( Fig. 8 ). Imagoes of I. moyarensis cannot be directly compared to imagoes of known Oriental species at this time. Available description of the known Oriental species of Isonychia lack diagnostic characters for direct comparisons of these species. However, I. moyarensis can be probably distinguished from Oriental species by the combination of the forewing with longitudinal rusty brown maculae in the costal, subcostal and medial areas ( Fig. 3 ), femur and tibia of foreleg brown, and tarsal segments pale with brownish apices ( Fig. 5 ), penes distally rounded and lacking serrations, second segment of gonostylus uniformly convex ( Fig. 8 ), and female sternum X deeply cleft ( Fig. 9 ).

Larvae of I. moyarensis are typical of the subgenus Isonychia , with forecoxal gill as a tuft of multibranched filaments ( Fig. 22 ). It can be distinguished from other Oriental species, for which larvae are known, by the following combination of the characters: posterior margins of abdominal terga II–IX with median dark brown maculae progressively larger with dark brown slanting streaks in lateral margins ( Fig. 11 ), trachea of abdominal gills I – VII unbranched ( Figs 26–28 ), posterolateral projections on abdominal segments I – VII blunt and progressively longer those of segments VIII – IX, sharp and distinct ( Figs 11 – 12 ), and abdominal terga X pale yellow in anterior ¼, dark brown in the posterior ¾ ( Fig. 11 ).

Figures

FIGURES 1–7. Adult male of Isonychia moyarensis n. sp. 1. Dorsal view; 2. Head and thorax; 3. Forewing; 4. Hindwing; 5. Foreleg; 6. Midleg; 7. Hind leg.

FIGURES 8–10. Adult of Isonychia moyarensis n. sp. 8. Male genitalia; 9. Female imago, subanal plate; 10. male abdomen, lateral view.

FIGURES 11–15. Larva of Isonychia moyarensis n. sp. 11. Dorsal view; 12. Ventral view; 13. Antenna; 14. Thorax and head; 15. Lateral view of abdomen.

FIGURES 16–23. Larva of Isonychia moyarensis n. sp. 16. Labrum; 17. Labium; 18. Left mandible; 19. Right mandible; 20. Maxilla; 21. Hypopharynx; 22. Foreleg; 23. Midleg.

FIGURES 24–28. Larva of Isonychia moyarensis n. sp. 24. Hind leg; 25. Mid tarsus; 26. Gill I; 27. Gill III; 28. Gill VII.