Epeorus (Epeorus) aculeatus Braasch, 1990

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 : 500-503

Epeorus (Epeorus) aculeatus Braasch, 1990

( Figs 1–17 )

Material examined: 1 larva, INDIA, Arunachal Pradesh, Lower Subansiri district, Duskilo stream, 27.62776 N, 93.8437 E, 1662 m, 16.vi.2017, colls. K. A. Subramanian and M. Vasanth [ZSI/ SRC-I / E 289 ] ; 6 larvae, Arunachal Pradesh, West Kameng district, Dirang, Showda village , Dirang river , 27.32675 N, 92.23180 E, 1877 m, 13.iii.2018, coll. Bikramjit Sinha [ZSI/ SRC-I / E 298 ] .

Description: Larva: Body length 9.5 mm; length of cerci 11.5 mm. Body generally dark brown ( Fig. 1 ).

Head: Length 1.7 mm, width 2.4 mm; brown, ( Fig. 1 ); subquadrangular; anterior and lateral margins convex, with rows of dense hair-like setae directed anteriorly; posterior margin slightly concave. Compound eyes black. Antennal scape and pedicel brown, flagellum pale. Labrum dark brown, deeply cleft with median notch on anterior margin; long hair-like setae laterally ( Fig. 5 ). Hypopharynx: Lingua with anterolateral lobes; superlinguae slightly expanded, laterally with rows of dense hair-like setae ( Fig. 6 ). Mandible without scattered setae along the molar; incisors serrated, outer incisor longer than inner incisor ( Figs 7–8 ). Maxilla with row of hair-like setae medially, apical segment of palp with dense row of hair-like setae, basal segment of palp broad ( Fig. 9 ). Labium broad, glossae with U-shaped separation, subtriangular; paraglossae slightly expanded laterally; apical segment of each palp pointed, dorsal surface with dense row of comb setae ( Fig. 10 ).

Thorax: Pronotum brown without clear marks; mesonotum somewhat darker brown with paramedian pair of darker spots anteriorly ( Fig. 1 ). Legs: Femur brown; hypodermal spot on dorsal surface, outer margin with long setae; distal end with blunt spine ( Figs 11–13 ); short stout blunt setae scattered on dorsal surface ( Fig. 11a ), tibia brown with long hair-like setae on outer margin; tarsi dark brown. Claw small with 3 denticles ( Fig. 14 ).

Abdomen: Abdominal terga dark brown, terga II–IX with pair of long, acute, submedian spines ( Fig. 2 ); posterior margin of tergum with hair-like setae medially and with numerous minute spines on segments II–IX ( Fig. 4 ); segments II–VII with long posterolateral extensions ( Fig. 3 ); sterna pale yellowish without markings. Lamellae of gill I somewhat extended beneath of abdomen ( Fig. 15 ). Gills II–VII with costal ribs arched and anal rib straight ( Figs 16–17 ). Cerci with hair-like setae dorsally.

Diagnosis: The larva of Epeorus (E.) aculeatus can be distinguished from other species of this genus by the following combination of characters: (i) posterior margin of abdominal terga II–IX each with pair of long, acute, submedian spines ( Figs 1–2 ); (ii) anterior margin of labrum with deep median notch ( Fig. 5 ); (iii) femur with short stout blunt setae scattered on dorsal surface ( Fig. 11a ).

Distribution: Thailand and India (Arunachal Pradesh).

Remarks: The larva of this species was described from Thailand by Braasch (1990) and male adult was described by Webb & McCafferty (2006); we provide a supplementary larval description based on our material, which represents the first record of the species for India.

Figures

FIGURES 1–8. Larva of Epeorus (Epeorus) aculeatus 1. Dorsal view; 2. Abdomen dorsal view; 3. Abdominal ventral view; 4. Posterior margin of abdominal terga V; 5. Labrum; 6. Hypopharynx; 7. Left mandible; 8. Right mandible.

FIGURES 9–17. Larva of Epeorus (Epeorus) aculeatus 9. Maxilla; 10. Labium; 11. Foreleg; 11A. Dorsal surface of femur; 12. Midleg; 13. Hindleg; 14. Claw; 15. Gill I; 16. Gill III; 17. Gill VII.