As this is a cleptoparasitic species, all flower visits will be for nectar only.
Celary (1991) lists the following plant species as nectar sources: Thymus serpyllum (Lamiaceae); Jasione montana (Campanulaceae); Solidago virgaurea, Tanacetum vulgare, Cirsium arvense, Centaurea scabiosa, Centaurea jacea, Sonchus arvensis, Hieracium umbellatum (Asteraceae); Eryngium campestre (Apiaceae). Pawlikowski & Kruszynski (1997) add Senecio vernalis (Asteraceae) as a nectar source in Poland.
Mavromoustakis (1948; 1951; 1952; 1953) lists Calendula persica (Asteraceae) and Eryngium creticum (Apiaceae); Limonium sp. (=Statice)(Plumbaginaceae); Rubus ulmifolius anatolicus (Rosaceae); Mentha longifolia (Lamiaceae); Tamarix sp. (Tamaricaceae) and Gagea chlorantha (Liliaceae) as nectar sources in Cyprus
Males will nectar at flowers of Solidago virgaurea (Asteraceae)