The worker bee explained

The age sequence

The sequence follows glandular development rather than a schedule, which is why it is flexible. A colony that loses its foragers will push young bees into foraging early, and one short of nurses can reverse the process — reactivating brood-food glands in bees that had already moved past that stage.

Why foraging is last

Foraging is dangerous. A forager flies several kilometres a day, is exposed to predators, weather and pesticides, and wears out her wings. Colonies therefore send their oldest bees, whose remaining value is lowest — a strategy of spending the individuals who have least life left.

A summer worker lives about six weeks and spends the last two or three of them foraging. Her total lifetime honey production is around a twelfth of a teaspoon.

Sterile but not entirely

Workers have ovaries, and in a normal colony they are suppressed by queen pheromone and by brood pheromone. They also police one another: workers detect and remove eggs laid by other workers, which keeps the colony's reproduction in the queen's control.

When a colony loses its queen and cannot replace her, that suppression fails. Workers begin laying, and because they are unmated every egg becomes a drone. It is the terminal stage of a queenless colony.

What a worker's body is for

• Brood-food glands in the head, producing royal jelly for larvae and for the queen.
• Wax glands on the underside of the abdomen, producing the scales that become comb.
• A honey stomach separate from the digestive gut, for carrying nectar and water.
• Pollen baskets on the hind legs, for carrying packed pollen.
• A barbed sting, which kills her if she uses it on a mammal.
• A Nasonov gland that releases an orientation scent to guide nestmates.

The winter worker

A bee reared in autumn is a different animal. She has an enlarged fat body, high vitellogenin levels, undeveloped brood-food glands that will activate in spring, and a lifespan of five to six months. She does almost nothing over winter except cluster, shiver and eat, and her job is to survive until there is brood to rear.