Diagnosis. The T. austriacus species subgroup (species complex sensu STRAKA 2005) differs from the T. pompiliformis species subgroup mainly by two very consistent characters in the males. In the T. austriacus species subgroup, the fore femoral notch is slightly shiny to shiny, not elevated and with distinct small setae, and setae on the volsellar apical process are uniformly (or nearly so) directed ventrally. In the T. pompiliformis species subgroup. the surface of the fore femoral notch is densely microsculptured, slightly elevated and with a distinct step on the inner margin, and the setae on the lower surface of the fore femoral notch are hardly visible (magnification 30×) and ventral setae on the volsellar apical process randomly directed (see figures in STRAKA 2005). In the T. pompiliformis group, females also have the malar space and adjacent part of genae with distinctly different punctation than in the T. austriacus species subgroup, however only T. austriacus resembles species of T. pompiliformis subgroup in this character.

Species included. Tachysphex austriacus Kohl, 1892, T. pekingensis Tsuneki, 1971, T. prismaticus Straka, 2005, and T. stysi sp. nov.