As this is a cleptoparasitic species, all flower visits will be for nectar only.
Celary (1991) lists the following species as nectar sources in Poland: Heracleum sphondylium, Angelica sylvestris, Daucus carota (Apiaceae); Jasione montana (Campanulaceae); Achillea millefolium, Bellis perennis, Cirsium arvense, Taraxacum officinale (Asteraceae).
Flowers visited in UK (Else & Edwards, 2018): Caucalis, Foeniculum vulgare, Angelica,Pastinaca sativa, Daucus (Apiaceae); Eupatorium, Tripleurospermum, Cirsium arvense (Asteraceae).
Mavromoustakis (1948) lists the following nectar sources in Cyprus: Ammi (Apiaceae) and Mentha longifolia (Lamiaceae).