A univoltine species; mid May to August, occasionally into September (Else & Edwards, 2018; Stanisavljević, 2000). Amiet et al. (2004) give a flight period in Switzerland from late-April to mid-September. Baldock et al. (in prep.) report flight activity from April and May in the Balearic Islands (Spain).
Parasites and predators The megachiline bees Stelis punctulatissima and S. phaeoptera, the sapygid wasps Sapyga quinquepunctata and S. clavicornis (van der Zanden, 1982), and possibly the chrysidid wasps Chrysura radians (Morgan, 1984) and Chrysis fulgida (Arnold, 1908) are probable cleptoparasites and parasitoids of O. leaiana, as they have sometimes been seen about its nest entrances. Banaszak & Romasenko (1989) additionally cite the chrysidid wasp Chrsis pustulosa.