They are so named because they hunt cicadas and provision their nests with them, after stinging and paralyzing them.
The highest diversity occurs in the region between North Africa and Central Asia.
A few other related genera also are sometimes referred to as "cicada killers", e.g. Liogorytes in South America and Exeirus in Australia.
More recently, it has been suspected that the western cicada killer (S. grandis) represents more than one species.
Alternatively, when they were already well distinct species, significant hybridization has occurred between them, though not enough to fully overcome their reproductive isolation.