A queen honey bee inspects each comb cell with her forelegs before laying. In a narrow worker cell she typically releases stored sperm from her spermatheca to fertilise the egg (diploid, 2n); in a wide drone cell she often withholds sperm, laying an unfertilised egg (haploid, n) — this is haplodiploidy, the sex-determination system of bees, ants and wasps.
Once laid, the egg stands upright, glued by its narrow end to the cell floor. Over roughly three days it gradually tips over until it lies flat, then the chorion splits and a legless larva emerges — a visible timeline of gastrulation and organogenesis happening invisibly inside the shell.
Because drones are haploid, they have no father in the usual sense and cannot pass traits to sons — but every one of their sperm cells is genetically identical, a quirk that shapes the unusually high relatedness among worker sisters in a hive.
A 3D cutaway of a single honeycomb cell follows a honey bee egg from the moment it is glued upright to the cell floor through its gradual three-day tilt, curl and hatch into a legless larva — with a fertilisation switch that reveals how haplodiploidy decides whether the egg becomes a female worker or a male drone.
The egg's steady tilt from vertical to horizontal over ~72 hours is a real field cue beekeepers use to age brood, while the fertilisation toggle shows haplodiploidy: fertilised (diploid) eggs become female, unfertilised (haploid) eggs become male drones.
Scrub the hours slider or press play to watch the egg develop in real time. Switch fertilisation on or off to compare diploid and haploid outcomes, and toggle the comb cell width to see the cue a queen senses before deciding whether to release sperm.
A queen can store sperm from her mating flights for years in her spermatheca, releasing a tiny drop to fertilise an egg only when her forelegs sense a narrow worker-sized cell.