Key to the males of Ephucilla naja group of the world

1. Flagellum entirely black................................................................................ 2

- Flagellum black, brownish beneath; species from India ..................................... E. ludovica (Cameron)

2. Median ocellus enlarged, MOD 1.00~ × OL, with posterior longitudinal carina; second inner subapical denticle on mandible reduced; mesosoma more or less yellowish red; metasoma with bluish metallic luster; parapenial lobe with small lobe on outer margin; cuspis robust, convergent apically, with long setae on ventral face and few on inner face...................... 3

- Median ocellus moderate, MOD 0.79–1.00 × OL, without posterior carina; second inner subapical denticle on mandible distinct; mesosoma black; metasoma black; parapenial lobe simple, without outer lobe; cuspis elongate, compressed, without distinct ventral face, with long setae on inner face; species from Taiwan ....................... E. guentheri (Zavattari)

3. Parapsidal line long; mesopleuron beneath with precoxal impunctate line; at least ventral half of mesopleuron, metapleuron and propodeum black; cuspis wider.......................................................................... 4

- Parapsidal line short; mesopleuron beneath without impunctate line; mesosoma entirely yellowish red; cuspis slender; species from Amami-ôshima Is., Japan ........................................................... E. yoshitakei sp. nov.

4. Tegula rounded posteriorly, hardly reaching mesoscuto-scutellar articulation, ~1.53 times longer than wide; apical fringes on T2–T3 sparse; species from Ryûkyû, Japan ................................................................. 5

- Tegula postero-laterally projecting, reaching mesoscuto-scutellar articulation, more than 1.54 times longer than wide; apical fringes on T2–T3 dense; species from Taiwan ................................................ E. naja (Zavattari)

5. Metanotum yellowish red; species from Okinawa-jima Is., Japan .................................. E. suginoi sp. nov.

- Metanotum black; species from Yaeyama Isls., Japan ........................................ E. brevitegula sp. nov.