As this is a cleptoparasitic species, all flower visits will be for nectar only.
Flowers visited: Potentilla (Rosaceae); Pulicaria dysenterica, Senecio jacobaea and Crepis (Asteraceae) appear to be the only British records, but elsewhere in Europe it visits Lotus corniculatus (Fabaceae); Rubus fruticosus agg., Potentilla erecta (Rosaceae); and Hypochoeris radicata (Asteraceae) (Jørgensen, 1921; F.K. Stöckhert, 1933) and might be expected to do the same in Britain.
Westrich (1989) lists the following nectar sources in Germany: Picris hieracioides, Lapsana communis, Hypochoeris radicata, Leontodon autumnalis, Hieracium umbellatum (Asteraceae); Lotus corniculatus (Fabaceae); Rubus fruticosus, Potentilla (Rosaceae); Veronica chamaedrys (Scrophulariaceae).
Elfving (1968) lists Chamerion angustifolium (Onagraceae); Lapsana communis, Leontodon autumnalis (Asteraceae); Veronica chamaedrys, Veronica officinalis (Plantaginaceae)