Longevity of bombus terrestris workers (Hymenoptera: Apidae) in relation to pollen availability, in the absence of foraging

The need for protein of Bombus terrestris workers was investigated by examining the effect of pollen availability on their longevity. Workers were kept under three conditions: provided with sugar solution only, with sugar solution and pollen ad libitum, and with sugar solution and pollen for 6 hours. Worker survival curves differed significantly among all conditions. Pollen deprivation led to a strong decline in survivorship whereas access to pollen for 6 hours only had a small and transient positive effect. This indicates that adult bumblebees have an ongoing need for protein food throughout their lives and confirms the observation that workers that eat pollen without subsequently feeding larvae do so for their own needs. There was no correlation between worker size and longevity, indicating that the reported higher mortality of foragers is not due to their bigger size. Our results show that, when environmental variables are excluded, workers die of senescence after about two months.