The life cycle and brood development

By Dwight Davis, Founder

Updated October 2026

On this page5

Three castes, three timetables Why 21 days matters Why 16 days matters more than people expect What you can read from it References

Almost every timing decision in beekeeping comes from two numbers: how long a worker takes to emerge, and how long a queen takes. Knowing them turns guesswork into arithmetic.

Three castes, three timetables

All three start as the same fertilized or unfertilized egg and diverge on diet and cell size.

Caste	Egg to emergence	As an egg
Queen	16 days	about 3 days
Worker	21 days	about 3 days
Drone	24 days	about 3 days

Each spends about three days as an egg. After that the larva is fed, the cell is capped, and development finishes out of sight, which is the part that matters for both disease and mites.

Why 21 days matters

It sets how fast a colony can respond to anything. A colony that loses population today cannot replace it for three weeks, which is why a problem spotted late is a problem that compounds before any fix takes effect.

It also sets the brood break arithmetic. Twenty-one days with no capped worker brood is twenty-one days that varroa has nowhere to reproduce, which is why splits and requeening have a mite benefit as well as a population cost.

Why 16 days matters more than people expect

Egg to emerged queen is about 16 days, and that is why two weeks is the inspection interval in spring. A colony can start queen cells the day after you close up and have a virgin queen emerging before a three-week inspection cycle brings you back. By then the old queen and half the bees have gone.

It is the same number behind splits: a queenless half needs about a month to raise, mate and start laying, and that gap is the real cost of dividing a colony.

What you can read from it

Eggs mean a queen laid within three days. The most useful single observation in an inspection.
Eggs but no capped brood, in season, means a queen that started recently.
Capped brood but no eggs means she stopped, and you have about three weeks of emerging bees before the population falls.
Drone brood in worker cells means a laying worker or a failing queen, and it looks like domed cappings across a scattered pattern.

References

eXtension Bee Health. Seasonality of Brood and Adult Populations; American and European Foulbrood. bee-health.extension.org

Penn State Extension. Honey Bee Management Throughout the Seasons; A Quick Reference Guide to Honey Bee Parasites, Pests, Predators, and Diseases. extension.psu.edu

University of Georgia Extension. Honey Bees and Beekeeping (B1045). extension.uga.edu

Written from published extension guidance, not from a laboratory. Local climate, local forage and the state of your particular colony override anything general said here.