Royal jelly is a milky secretion produced in the hypopharyngeal and mandibular glands of young "nurse" worker bees, aged roughly 5–15 days old. Every larva in the colony — worker, drone or queen — is fed royal jelly for its first three days of life. From day four onward, worker and drone larvae are switched to a diet of diluted honey and pollen ("bee bread"), while a larva destined to become a queen is bathed in royal jelly continuously throughout its five-to-six day larval period, in far greater quantity.
A single UK apiary can graft 20–40 day-old larvae onto artificial queen cups at once; each accepted queen cell can yield 200–400mg of harvestable royal jelly if pulled at the right stage — hobbyist beekeepers usually raise only a handful of queens per season rather than farming jelly commercially.
A 3D cutaway of honeycomb cells where nurse bees secrete and top up royal jelly for developing larvae — switch between ordinary worker brood and a grafted queen-rearing frame, and simulate harvesting the pooled jelly.
Worker and drone larvae get royal jelly only for their first three days before switching to honey and pollen, while grafted queen larvae stay bathed in it continuously — the biological basis of caste determination and of commercial harvesting.
Choose worker brood or queen-rearing mode, drag the larva age slider through the 0–6 day cycle, adjust nurse feeding rate to see more bees visiting cells, and press Harvest to pull jelly from queen cups and tally the yield.
UK beekeepers who raise their own queens graft day-old larvae into artificial cups with a fine grafting tool — the same technique, scaled up, is what commercial royal jelly producers use to harvest hundreds of milligrams per cell.