A univoltine species; end of June to late September (exceptionally October). The small form of this species, which is presumed to be cleptoparasitic on Colletes marginatus, flies earlier in the season (June to July) than that which attacks the cells of Colletes succinctus (late July onwards)(Else & Edwards, 2018). Amiet et al (2007) give a flight period in Switzerland from the June to early October