As this is a cleptoparasitic species, all flower visits will be for nectar only.
Flowers visited in GB (Else & Edwards, 2018): Prunus (Rosaceae); Torilis japonica, Smyrnium olusatrum, Pimpinella major, Oenanthe, Angelica, Pastinaca sativa, Heracleum, Daucus (Apiaceae); Euphorbia (Euphorbiaceae); Jasione (Campanulaceae); Senecio, Pulicaria, Anaphalis, Solidago, Eupatorium, Achillea ptarmica, Cirsium palustre, Cirsium arvense, Sonchus arvensis (Asteraceae).
Celary (1991) lists the following nectar sources in Poland: Berteroa
incana (Brassicaceae); Fragaria vesca, Potentilla argentea, Potentilla arenaria (Rosaceae); Daucus carota (Apiaceae); Calluna vulgaris (Ericaceae); Veronica chamaedrys (Scrophulariaceae); Thymus serpyllum (Lamiaceae); Jasione montana (Campanulaceae); Helichrysum arenarium, Achillea millfolium, Anthemis arvensis, Matricaria chamomilla, Senecio jacobaea, Cirsium arvense, Leontodon autumnalis, Taraxacum officinale, Hieracium pilosella (Asteraceae).
Pawlikowski & Kruszynski (1997) list Senecio vernalis (Asteraceae) as a nectar source in Poland.
Mavromoustakis (1948) reports nectaring visits on Cyprus to the following species: Alyssum troodi (Brassicaceae); Anthemis arvensis (Asteraceae); and unspecified Apiaceae.