Harvested pollen. Balls of pollen harvested by bees. Bees are dependent on pollen as a protein source and on nectar (or sometimes oils) from flowers as an energy source. Adult female bees collect pollen primarily to feed their larvae, although the adults also feed on it. As a bee travels from flower to flower it crams the pollen baskets on its hind legs with pollen grains for transport back to its nest or hive. During these foraging flights the bee will transfer pollen between flowers of the same species, which allows cross-pollination. Bees are, in fact, the most important pollinating insects.