Oligolectic on Campanula (Campanulaceae) species, including Campanula trachelium, Campanula glomerata and Campanula rotundifolia (Amiet et al., 2004; Sedivy et al., 2008; Westrich, 1989). There are some instances of pollen collection from species other than bellflowers; for example, M. Edwards (pers. comm.) has observed a female foraging from Geranium (Geraniaceae) in a West Sussex garden.
In Britain the species visits the following species, probably as nectar sources: Malva sylvestris (Malvaceae); Geranium pratense (Geraniaceae); Rubus laciniatus (Rosaceae); Sedum acre (Crassulaceae) Jasione (Campanulaceae); and Taraxacum (Asteraceae).
Chelostoma campanularum also visits the orchid Cephalanthera rubra (Orchidaceae) in both Britain and on the continent. In Britain, this is an endangered species, confined to about five known sites in southern England (Fisher, 1987; Whitten, 1991; Jenkinson, 1995). Very few of the rose-coloured flowers are produced by these plants (Perring & Farrell, 1977) and it does not seem to be known if cross pollination occurs. In Hampshire, Chelostoma campanularum has been observed visiting open flowers of Cephalanthera rubra, possibly effecting pollination (D. Ball, pers. comm.).
In Finland, Käpylä (1978) analysed one pollen load which comprised 92% Caryophyllaceae pollen (probably Stellaria graminea), another which contained 33% Brassicaceae pollen and finally a third load which included 12% Ranunculus pollen. Pekkarinen (1998) lists only Campanula (Campanulaceae) as a pollen source in Finland.
Käpylä (1978) observed that nectaring mainly occurs in Asteraceae, Caryophyllaceae, Brassicaceae and Potentilla (Rosaceae). According to his field observations and pollen analysis, males show only weak specialisation, visiting many more plant species than females. Besides Campanula they visit Potentilla (Rosaceae) and Asteraceae.