This genus has been treated as a subgenus of Omalus by some authors (e.g. Linsenmaier 1959, 1997). It is well characterised by the shape of the metascutellum, which has a large tongue-like projection dorsally (Fig. 38). The posterior margin of T3 is usually extended into a horseshoe-shaped or falcate rim forming truncation (Figs 39–40, 44–46). The female has a row of dense and erect setae along the genal margin (Fig. 41). These setae are replaced by long irregularly placed bristles in the male. The hosts are ground-nesting crabronid wasps, such as Mimesa Shuckard and Mimumesa Malloch (Kimsey and Bohart 1991). The genus is distributed in the Palearctic Region (more than 40 species), North America (8 species), Africa (7 species) and South America (3 species) (Kimsey and Bohart 1991, Linsenmaier 1999, Madl and Rosa 2012). A total of 12 species have been found in Europe (Rosa and Soon 2012), and three of these occur in the Nordic and Baltic countries (Paukkunen et al. 2014).