Pollen collection by honey bees
While we normally think of honey bees collecting nectar, an average-size colony may bring in 100 pounds of pollen in a season. Pollen is an essential part of the honey bee diet, providing a wide range of nutrients including protein, carbohydrates, lipids, vitamins, and minerals.
Although a tough outer coating protects the pollen from environmental stressors, honey bees have enzymes in their digestive tract that split the grains apart at a weak point. The interior is then digested and the empty husks are excreted. Most of the pollen is eaten by nurse bees. They use the nutrition absorbed from it to secrete royal jelly from their hypopharyngeal glands. The jelly is fed to young larvae, including workers, drones and queens. After about three days the jelly is mixed with bee bread—a mixture of whole pollen, honey, and enzymes—and fed to the workers and drones until they spin their cocoons. The queens receive a steady diet of royal jelly throughout their development.
Most bees collect just pollen or just nectar on any trip, but a few carry both at the same time. The pollen is stuffed into hairy receptacles on their hind legs called corbiculae. A single bee can carry about half her own body weight in pollen.
Once back at the hive, the workers stuff the pollen into an awaiting cell. Unlike nectar-carrying bees, pollen-carrying bees have to off-load it themselves. In addition to depositing the pellets from their sacks, they may also groom away any pollen that is stuck to their bodies. The pollen is stored in cells at the perimeter of the brood nest, forming a ring around it. During the brood rearing season, the pollen is stored for only a few days. During the winter it is stored for much longer.
Honey bees usually forage on only one kind of flower on any single trip. This is nature’s way of assuring that plants are cross-pollinated. So a bee going to blackberries, keeps going to blackberries until there are no more blackberry flowers, then she will switch to something else. Honey bees collect pollen even from plants that don’t provide nectar, such as corn. In corn-growing regions, pesticide-contaminated corn pollen is suspected of causing severe health problems within the hive.