Infected honeybee foragers incur a higher loss in efficiency than in the rate of energetic gain.

Parasites, by altering the nutritional and energetic state of their hosts, can significantly alter their foraging behaviour. In honeybees, an infection with Nosema ceranae has been shown to lower the energetic state of individual bees, bringing about changes in behaviours associated with foraging. Comparing the foraging trip times, hive times in between trips, and the crop contents of uninfected and infected foragers as they depart on foraging trips and return from them, this study examined how any differences in these variables influence alternative foraging currencies. The results show that infected bees take longer foraging trips, spend shorter time in the hive between successive trips and bring back less sugar from each trip. These changes have a stronger adverse effect on their efficiency of energetic gain as compared with their rate of energetic gain, which has important implications for individual and colony life history.