Key to adult males of Sri Lankan Onomastus

1. MA with pleated prolateral branch (Figs 5 A, 6B; Benjamin 2010: fig. 27a.........................................2

- MA without pleated prolateral branch.....................................................................3

2. Prolateral branch of MA, hook-shaped (Figs 5 A, 6B)....................................... O. corbetensis sp. nov.

- Prolateral branch of MA with rounded tip (Benjamin 2010: fig. 27a).................................. O. rattotensis

3. Terminus of MA bifurcated (Figs 2 A, 3A)..................................................................4

- Terminus of MA not bifurcated, globular with stout or pointed tip................................................5

4. Prolateral branch of MA terminus, smaller than the retrolateral branch (Benjamin 2010: fig. 10a)............ O. nigricauda

- Prolateral and retrolateral branches of equal size (Figs 2 A, 3A).............................. O. jamestaylori sp. nov.

5. Terminus of MA globular but without any prominent apical hump (Fig. 8 A)...................... O. maskeliya sp. nov.

- Terminus of MA with apical hump........................................................................ 6

6. Terminus of MA with pointed tip (Benjamin 2010: fig. 22a)...................................... O. quinquenotatus

- Terminus of MA with stout tip (Benjamin 2010: fig. 23b).......................................... O. pethiyagodai