Key to males of Ngirhaphium

1 Mesonotum and tergites metallic blue. Antenna with apical aristal article filiform and much longer than basal article (Singa- pore). Genitalia as in Figures 8 and 11 ..................................... N. caeruleum Grootaert & Puniamoorthy

- Mesonotum and tergites mainly metallic green. Antenna with apical aristal article shorter or about half as long as apical article................................................................................................... 2

2 Cerci in lateral view nearly as long as dorsal surstyli (Figs 3, 4).............................. N. chutamasae sp. nov.

- Cerci in lateral view longer than dorsal surstyli (Figs 7, 9).................................................... 3

3 Dorsal surstylus elongate, digitiform with truncate apex (Figs 9, 12) slightly shorter than cercus. Cerci with narrow apex, set with 2 apical setae (Fig. 12).................................................. N. murphyi Evenhuis & Grootaert

- Dorsal surstylus with very wide apex (Fig. 7) much shorter than cercus. Cerci with expanded apex set with many yellow setae (Fig. 10)............................................................ N. sivasothii Grootaert & Puniamoorthy