Pollen is the colony's only source of protein, fat, vitamins and minerals — nectar supplies sugar for energy, but larvae and nurse bees need pollen to grow and to produce brood food. A forager lands on a flower and uses her front and middle legs to comb loose pollen grains out of the branched hairs covering her body, moistens the grains with a little regurgitated nectar, and packs them into a dense pellet in the corbicula — the smooth, concave "pollen basket" on the outside of each hind tibia, fringed with stiff hairs that hold the load in place in flight.
A single strong colony can bring in tens of kilograms of pollen over a season, and nurse bees typically eat pollen directly to produce protein-rich brood food in their hypopharyngeal glands — the larvae themselves are usually fed that processed food rather than raw pollen grains.
A forager honeybee combs pollen from her hairy body into the pollen baskets on her hind legs across flower species of different protein content, then delivers each load to the hive where the colony's protein reserve shapes brood health.
Each species' pollen carries a different protein content; the forager's pellet colour blends toward whatever she has visited, and delivered loads move a running colony protein average that directly sets brood size and colour in the comb.
Set how many flower species are blooming, adjust flight speed, and optionally focus the forager on one species. Watch the pellet grow on her hind leg, then track colony protein and brood health as loads are delivered.
The corbicula, or pollen basket, is not lined with hairs like the rest of the leg — it is a smooth concave surface fringed by stiff bristles that clamp the moistened pollen pellet in place during flight.