Omalus Panzer, 1801

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), Zootaxa 4013 (1), pp. 67-76 : 68

Genus Omalus Panzer, 1801

Omalus Panzer, 1801: 13 . Type species: Chrysis aenea Fabricius, 1787 , by monotypy.

Homalus Saunders, 1873: 411. Unjustified emendation of Omalus Panzer, 1801 .

Omalus Panzer : Linsenmaier 1959: 17 (part., Omalus s. str.); Bohart & Campos 1960: 235 (part., Omalus s. str.); Bohart & Kimsey 1982: 36 (part., Omalus s. str.); Kimsey & Bohart 1991: 243; Rosa 2005: 8; 2006: 100; Wei et al. 2014: 30.

Diagnosis. Omalus Panzer, 1801 is close to Holophris Mocsary, 1890 , Philoctetes Abeille de Perrin, 1879, and Pseudomalus Ashmead, 1902 . It can be distinguished from them by the combination of the following characteristics: head lenticular in frontal view; scapal basin deep, smooth and glabrous, rarely with weak striae; MS usually equal to or longer than 1 MOD, and horizontally bisected by curved genal carina; postocular margin angulated; mandible tridentate; pronotum impunctate medially; mesoscutum impunctate, at most with very sparse and tiny punctures, or weakly wrinkled; mesopleuron with single carina or with weak double carinae, but not well developed as in Holophris , and usually limited to some large foveae ( O. timidus ); in few cases, large foveae aligned along the omaulus, thus resembling the double omaulus of Holophris (e. g. O. imbecillus and O. pseudoimbecillus ); mesoscutellum without anterior foveae or with anterior foveae; transpleural carina reaching apex of propodeal angle; forewing medial cell asetose, medial vein strongly arched and arising before cu-a, stigma short, broad, and apically rounded (the only exception is the O. aeneus species-group, whose medial vein is longer and weakly arched); tarsal claw with three to four teeth; T3 with or without semitransparent rim on posterior margin, and sometimes on T2; apex of T3 with or without median notch.

Distribution. The species of Omalus occur in all zoogeographic regions except Australia. There are 33 valid species: 22 are found in the Palaearctic, two in both the Palaearctic and the Oriental, one in both the Holarctic and the Oriental, two in the Oriental, three in the Nearctic, two in the Afrotropical, and one in the Neotropical Regions. In this paper, four species are reported, including two new species, and two new records from China.