Epeorus (Epeorus) bifurcatus Braasch & Soldán, 1979

Vasanth, M., Selvakumar, C., Subramanian, K. A., Sivaramakrishnan, K. G. & Sinha, Bikramjit, 2021, Contribution to the study of Epeorus Eaton, 1881 (Ephemeroptera: Heptageniidae) from India, Zootaxa 4991 (3), pp. 499-522 : 503

Epeorus (Epeorus) bifurcatus Braasch & Soldán, 1979

( Figs 18–34 )

Material examined: 2 larvae, India, Arunachal Pradesh, West Kameng, Dirang, Showda village , Dirang river , 27.3267528 N, 92.2318027 E, 1877 m, 13.iii.2018, coll. Bikramjit Sinha [ZSI/ SRC-I /E/297] ; 1 larva, India, Arunachal Pradesh, Upper Dibang Valley, Mipi, Mipi river , 28.96643 N, 95.8061 E, 1455 m, 31.x.2017, coll. Anil Kumar & Party [ZSI/ SRC-I /E/312] ; 15 larvae, India, Arunachal Pradesh, West Kameng district, Sangti valley, Khechalu , Khendo Rong (stream), 27.420841 N, 92.269538 E, 1790 m, 12.iii.2018. coll. Bikramjit Sinha [ZSI/ SRC-I /E/320] .

Description: Larva: Body length 9.8 mm; length of cerci 10.4 mm. Body generally dark brown ( Fig. 18 ).

Head: Length 1.7 mm, width 2.9 mm; light brown ( Fig. 18 ); subquadrangular; anterior and lateral margins convex, with rows of hair-like setae directed anteriorly. Compound eyes black. Antennae with scape, pedicels and flagella light brown ( Fig. 22 ). Labrum brown with deep median notch on anterior margin, long hair-like setae laterally ( Fig. 23 ). Hypopharynx as in Fig. 24 . Mandibles without scattered setae along the molar area; incisors serrated, outer incisor longer than inner incisor ( Figs 25–26 ). Maxilla as in Fig. 27 . Labium ( Fig. 28 ) as in the previous species.

Thorax: Pronotum pale brown with indistinct band in middle and pair of dark spots; mesonotum brown ( Fig. 18 ). Legs ( Figs 29–31 ): Femora light brown, hypodermal spot on middle, outer margin with long setae and dark brown maculae medially; distal end with blunt spine; dorsal surface with scattered stout short thickened setae ( Fig. 31a ); tibia pale brown with long hair-like setae on outer margin; claw with 3 small denticles ( Fig. 32 ).

Abdomen: Abdominal terga light brown, terga II–IX with pair of short submedian spines ( Figs 18, 20 ); tergum II yellowish, terga III and IV with indistinct pale patches on middle, terga V–VIII with light middle band; terga II–IX with small setae along midline ( Fig. 21 ); segments II–VII with long postero-lateral extensions; sterna light yellowish without markings ( Fig. 19 ). Gill I triangular ( Fig. 33 ); gills II–VII oval ( Fig. 34 ). Cerci with row of hairlike setae dorsally.

Diagnosis: The larva of Epeorus (E.) bifurcatus can be distinguished from other species of this genus by the following combination of characters: (i) posterior margin of abdominal terga II–IX with pair of short submedian spines ( Figs 18 & 20 ); terga II–IX with small setae along midline ( Fig. 21 ); and (iii) gill I larger than others ( Fig. 33 ).

Distribution: Vietnam, Thailand and India (Arunachal Pradesh).

Remarks: The larva of this species was described from Vietnam by Braasch & Soldán (1979). Subsequently, Nguyen & Bae (2004) redescribed the larva of E. bifurcatus based also on specimens from Vietnam. Braasch & Boonsoong (2010) reported this species from Thailand; we provide a supplementary larval description based on our material, which represents the first record of the species for India.

Figures

FIGURES 18–24. Larva of Epeorus (Epeorus) bifurcatus 18. Dorsal view; 19. Abdomen ventral view; 20. Abdomen dorsal view; 21. Posterior margin of abdominal terga V; 22. Antenna; 23 Labrum; 24. Hypopharynx.

FIGURES 25–34. Larva of Epeorus (Epeorus) bifurcatus 25. Left mandible; 26. Right mandible; 27. Maxilla; 28. Labium; 29. Foreleg; 30. Midleg; 31. Hindleg; 31a. Dorsal surface of femur; 32. Claw; 33. Gill I; 34. Gill III.