Key to Chinese species of the genus Omalus 1. T3 with wide semitransparent rim (≥ 1 MOD).............................................................. 2 - T3 without semitransparent rim or with narrow semitransparent rim (≤0.5 MOD)................................... 5 2. Mesoscutum weakly wrinkled; notauli distinct and complete.................................. O. corrugatus sp. nov. - Mesoscutum polished without wrinkles; notauli indistinct or absent............................................. 3 3. Tarsal claw with four teeth............................................................... O. timidus (Nurse) - Tarsal claw with three teeth............................................................................ 4 4. Mesoscutellum evenly punctate and with two anterior foveae; metanotum gibbous with round and subequally spaced punctures.................................................................................. O. hainanensis sp. nov. - Mesoscutellum largely polished and without anterior foveae; metanotum prominent with irregular and large punctures without interspaces....................................................................... O. potanini (Semenov) 5. Tarsal claw with four teeth............................................................................ 6 - Tarsal claw with three teeth............................................................................. 8 6. Mesoscutum weakly wrinkled............................................. O. probiaccinctus Wei, Rosa, Liu & Xu - Mesoscutum polished, at most punctate................................................................... 7 7. Body light metallic green with golden reflections; medial vein short and strongly arched. O. stella (Semenov & Nikol'skaya) - Female body metallic blue sometimes with violet reflections and male body metallic blue to green, often dorsally blackish; medial vein longer and gently curved.................................................... O. aeneus (Fabricius) 8. Notauli distinct and deep............................................................................... 9 - Notauli indistinct and shallow, impressed as fine lines....................................................... 10 9. Pronotum with scattered and shallow punctures medially; metasoma pear-shaped; T2 distinctly wider than T1; T3 with median notch V-shaped.................................................................. O. berezovskii (Semenov) - Pronotum almost impunctate medially; metasoma distinctly elongate; T2 not wider than T1; T3 with median notch shallowly indented................................................................. O. tibetanus Wei, Rosa, Liu & Xu 10. Mesoscutellum without anterior foveae...................................... O. helanshanus Wei, Rosa, Liu & Xu - Mesoscutellum with two anterior foveae................................................................. 11 11. Tegula fully metallic blue; mesopleuron without striae among punctures; propodeal angle indistinct. O. imbecillus (Mocsáry) - Tegula transparent brown, with faint metallic reflections anteriorly; mesopleuron with striae among punctures; propodeal angle distinct and stout.................................................... .. O. pseudoimbecillus Wei, Rosa, Liu & Xu

Published as part of Rosa, Paolo, Wei, Na-Sen & Xu, Zai-Fu, 2015, Contribution to the genus Omalus Panzer, 1801 of China, with descriptions of two new species (Hymenoptera, Chrysididae), pp. 67-76 in Zootaxa 4013 (1) on pages 68-69, DOI: 10.11646/zootaxa.4013.1.4, http://zenodo.org/record/289413