The honey bee lifecycle

The four stages

EggA white grain about 1.5 mm long, stood on end at the base of a cell. The queen lays it and it stands upright on day one, leans on day two and lies flat on day three, which lets a beekeeper date a cell by eye.
LarvaA legless white grub that does nothing but eat. Workers feed it continuously — a larva is visited over a thousand times a day — and it increases its weight roughly 1,500-fold in six days.
PupaThe cell is capped and the larva spins a cocoon. Inside, the body is substantially reorganised into the adult form. Nothing is fed and nothing is visible from outside.
AdultThe bee chews through the capping and emerges, pale and soft, and begins work almost immediately.

Why caste timing matters

Development time by caste, in days
Stage	Queen	Worker	Drone
Egg	3	3	3
Larva	5.5	6	6.5
Capped and pupating	7.5	12	14.5
Total to emergence	16	21	24

Days from egg to emergence: queen 16 (egg 3, open larva 5.5, capped 7.5), worker 21 (3, 6, 12) and drone 24 (3, 6.5, 14.5). Queen and worker start from the same fertilised egg; a larva fed royal jelly beyond its first three days or so becomes a queen, which the dashed line marks. Typical values; temperature in the brood nest shifts them by a day or so. The capped stage is the one Varroa breeds in, which is why the drone’s longer capped period favours the mite. Sources: The Biology of the Honey Bee. Drawing: HoneyHQ (HEKNO Ltd), original.

The queen's 16 days against the worker's 21 is not a small detail. All three castes come from the same fertilised egg in the queen and worker case — the difference is diet, not genetics — and the shorter development is a consequence of being fed royal jelly throughout rather than only for the first three days.

What decides caste

A fertilised egg becomes a queen or a worker depending entirely on how it is fed. All larvae receive royal jelly for the first three days. Worker larvae are then switched to a mixture of pollen and honey; queen larvae continue on royal jelly throughout. That dietary difference switches on a different developmental programme, producing a larger, longer-lived, fertile female.

Drones are different again. They develop from unfertilised eggs and are therefore haploid, carrying only their mother's genes. A drone has a grandfather but no father, which is one of the stranger facts in animal biology and has real consequences for how relatedness works in a colony.

What an adult worker does with her life

A summer worker lives about six weeks and moves through a rough sequence of jobs as her glands develop and then atrophy. She cleans cells for the first few days, feeds larvae for around a week while her brood-food glands are active, then builds comb, then receives and processes nectar, then guards, and finally forages for the last two or three weeks of her life.

The sequence is a tendency rather than a rota. Colonies reassign bees when circumstances demand it, and a colony that loses its foragers will accelerate young bees into foraging while a colony short of nurses can reverse the process.