Fig 2. Nosema ceranae infection intensity in samples of known-age bees (marked) and mixed-age background bees.

Shown are mean ± SE Nosema ceranae infection intensities of marked bees and background (unknown, mixed-age) bees at each age group/sampling event. Marked bees were recently emerged bees at the first sampling event, nurse-aged bees at the second sampling event and forager-aged bees at the third sampling event. There were significant differences among the age cohorts, as indicated by different letters (P < 0.01).