Flower feeding animals, like bumble bees, encounter temporal and spatial variations in a floral environment. Bumble bee foragers have to track changing resources individually because they cannot exchange information of resource availability and location. To understand how they respond to a changing environment, it is necessary to observe the resource use of individuals from the same colony in the field for a long term. Therefore, to explore the relationship between the flower availability and the resource use in bumble bees (Bombus diversis), I analyzed pollen samples collected by individually marked foragers. In addition, to reveal the daily resource use at the colony level, I developed an observation system with the web camera and the motion detector that recorded all successive foraging trips for about two months. As a result, the overall resource use of the colony was similar to the mean composition of the numbers of available flowers, though the daily resource use of the colony fluctuated depending on the change of the flower availability. This fluctuation was thought to be caused by the foragers' habit to hardly switch their target species from those they had previously collected. Although such habit is known to be caused by memory limitations, the fluctuation may be a result of a bang-bang control that enables bumble bees to efficiently forage in response to the changing environment.