Division of labor by division of risk according to worker life expectancy in the honey bee (Apis mellifera L.)

The hypothesis that the division of labor in foraging honey bee workers is a consequence of division of risk among foragers with differing life expectancies was tested using a dynamic programming model and field experiment. Honey bee workers collecting water were captured in the middle of one cold day and one warm day in April, May and July. We investigated whether workers infected with Nosema apis or workers with worn wings undertake foraging in poorer weather conditions more often than do healthy workers or workers with unworn wings. On each pair of days, the ratio of diseased workers and workers with worn wings was usually significantly higher on the cold day than on the warm day. The result that risky tasks are more often undertaken by workers with shorter life expectancy is in favor of the predictions of the model.