A univoltine species, flying from late May or early June to the end of August. Matache & Ban (2006) note a specimen in October in Romania. Stanisavljević (2000) gives a flight season of June to September in Serbia
Westrich (1989) suggests that there is partial bivoltinism in this species in Germany. Apparently it is usually double-brooded in Canada (Gentry, 1874), but Medler (1959) considers it to be single-brooded in northern Wisconsin.
Parasites and predators The megachiline bee Coelioxys inermis is a common cleptoparasite of this species. Richards (1950) reared a female C. rufescens from a nest of Megachile centuncularis. Nests are also invaded by the chalcid Melittobia acasta (Eulophidae), which attacks both larvae and prepupae (Holm & Skou, 1972; Banaszak & Romasenko, 1998). Banaszak & Romasenko additionally list as either cleptoparasites and inquilines the bees Coelioxys elongata, C. inermis, C. mandibularis and, in the Nearctic region, C. moesta and the chalcid wasps Mellitobia halybii (Eulophidae), Monodontomerus laticornis and M. montivagus.