As this is a cleptoparasitic species, all flower visits will be for nectar only.
Westrich (1989) lists the following flowers as nectar sources: Buphthalmum salicifolium, Senecio jacobaea (Asteraceae).
Celary (1995)(citing Noskiewicz 1925) lists Inula, Tanacetum vulgare and Jacobaea vulgaris (Asteraceae) as nectar sources.
Celary (2007), and Kasparek (2015) list plants of the families Apiaceae, Asteraceae and Boraginaceae as nectar sources. Schmalz (1998) reports visits to Hieracium sp. and Leontodon autumnalis (Asteraceae)