Key to species of the genus Trachyusa

1. Body slender; mesoscutum slender,>1.00X longer than wide; antenna longer than body length........................ 2

- Body stout; mesoscutum comparatively robust, <1.00X longer than wide; antenna as long as or shorter than body length.... 5

2. Head transverse, 1.70–2.20X wider than long medially........................................................ 3

- Head cubic, 1.50–1.60X wider than long medially...................................... Trachyusa aurora (Haliday)

3. Mesoscutum with short midpit (Belokobylskij 1998: plate 109, fig. 5); sternaulus long, wide, conspicuously extending to poste- rior edge of mesopleuron; 1m-cu slightly postfurcal (Belokobylskij 1998: plate 109, fig. 4)... Trachyusa indrik Belokobylskij

- Mesoscutum with long midpit (Fig. 7); sternaulus short, becoming inceasingly inconspicuous toward posterior edge of mesopleuron (Fig. 6); 1m-cu slightly antefurcal (Fig. 1)....................................................... 4

4. Notauli wide anteriorly and narrow posteriorly, sculptured (Belokobylskij 1998: plate 109, fig. 6); metacoxae more or less sculp- tured; mesosoma and metasoma black or dark reddish brown; first flagellomere 3.50–4.30X longer than apical width; head

width 1.70–1.90X longer than medial length; (Belokobylskij 1998: plate 109, fig. 7)....... Trachyusa vasilisk Belokobylskij - Notauli wide and with deep sculpture (Fig. 4); metacoxae smooth (Fig. 10); mesosoma and metasoma yellow (Fig. 1); first flagellomere 4.50–5.75X longer than apical width; head width 1.67–2.25X longer than medial length (Fig. 4)......................................................................................... Trachyusa whartoni Yao, sp. n. 5. Notauli on posterior half of mesoscutal disc deeply impressed (Papp 1967: fig. 2); mesoscutum black; first metasomal tergum usually more slender (Papp 1967: fig. 3).............................................. Trachyusa szepligetii Papp

- Notauli on posterior half of mesoscutal disc at most shallowly impressed (Papp 1967: fig. 8); mesoscutum brownish yellow; first tergum rather robust (Papp 1967: fig. 9)........................................... Trachyusa bucephala Papp