A narrowly oligolectic species: Campanulaceae (Pesenko in Banaszak, 1995). Usually associated with Campanula rotundifolia, and C. glomerata occasionally with Campanula trachelium.
Pekkarinen (1998) lists only Campanula (Campanulaceae) as a pollen source in Finland.
Michez (2004) lists the following species: Campanula gracilis, Campanula latifolia, Campanula medium, Campanula persicifolia, Campanula rapunculoides, Campanula rotundifolia,
Campanula trachelium (Campanulaceae).
Celary (2005) lists the following pollen forage species in Poland: Campanula glomerata, Campanula patula, Campanula persicifolia and Campanula trachelium (Campanulaceae). Other pollen sources cited by Celary are Campanula rapunculoides (Celary, 1991), Campanula rotundifolia (Alfken, 1912; 1913), Campanula sibirica (Ruszkowski et al, 1998) and Jasione montana (Campanulaceae)(Banaszak, 1974).
More rarely, and purely for nectar: Centaurea jacea, Centaurea scabiosa, Cichorium intybus, Eupatorium cannabinum, Tanacetum sp. (Asteraceae); Sedum telephium (Crassulaceae); Knautia arvensis (Dipsacaceae); Lathyrus latifolius, Medicago media, Trifolium pratense (Fabaceae); Malva sp. (Malvaceae); Symphytum officinale (Boraginaceae); Geranium pratense, Geranium sanguineum (Geraniaceae); Prunella spp., Thymus serpyllum (Lamiaceae); Veronica spicata (Plantaginaceae).
The males hae been observed taking refuge in flowers of Malva moschata (Malvaceae) in inclement weather (Litt, 1999).
Levchenko (2009) lists the following as forage sources in the Moscow region of Russia: Campanula trachelium, Campanula bononiensis, Campanula persicifolia (Campanulaceae); Geranium palustre, Geranium pratense (Geraniaceae); Veronica teucrium (Plantaginaceae).