Figure 2.

Experimental setup (i.e., two-box system) used for the feeding choice experiment. Nest chamber was kept into the dark with one small willow candy for brood initiation; feeding chamber was provided with syrup, kept under 12 h natural light conditions and divided in two compartments for worker pollen choice. Workers were enabled to freely move between the two chambers through a tube connection. Three pollen combinations were used namely, heather/multifloral, sunflower/multifloral, and heather/sunflower. All combinations were tested with infected and uninfected microcolonies. Nine microcolonies were used per treatment (infection*pollen combination).