As this is a cleptoparasitic species, all flower visits will be for nectar only.
Lieftinck (1969) lists Vicia (Fabaceae) and Thymus (Lamiaceae) as nectar sources.
There are flower visitation records from Greece of the insect visiting Satureja thymbra (Lamiaceae) and Scorzonera lanata (Asteraceae)(T. Petanidou, unpublished database)