What a swarm cell is
A swarm cell is a queen cell that worker bees build when a colony is preparing to swarm. It is a larger, peanut-shaped wax cup that hangs vertically from the comb, where workers feed a female larva royal jelly so that it develops into a queen (how a queen bee is born). When the colony swarms, the old queen leaves with a large part of the workers, and the bees left behind raise a new queen from one of these cells.
Swarming is how honey bee colonies reproduce. In beekeeping, “a swarm” is the group of bees that leaves with the old queen to find a new home. See how to attract a swarm with a bait hive if you want to catch one.
Swarm cups versus queen cells
Colonies often build queen cups, which are small, open, empty cups that look like an acorn cap. Cups on their own are common and do not mean a swarm is imminent. A cup becomes a queen cell when the queen lays an egg in it or bees place a larva in it, and workers begin extending it into the longer peanut shape. Cells containing an egg or a larva deserve attention. A capped cell means the larva is pupating and a queen will emerge in several days.
Swarm, supersedure and emergency cells compared
Queen cells are built for three different reasons, and you often have to read several clues to tell them apart.
| Feature | Swarm cells | Supersedure cells | Emergency cells |
|---|---|---|---|
| Trigger | Crowding, strong colony | Failing or old queen | Sudden loss of queen |
| Usual location | Bottom or edges of frames | Often mid-comb, on the face | Face of comb, converted worker cells |
| Number | Often several | Often one to a few | Often several, uneven |
| Shape | Smooth, peanut-like | Similar to swarm cells | Often irregular, shorter |
These patterns are general tendencies, not rules. Experienced beekeepers also look at the colony: does it have a queen, are there eggs, and is the box crowded?
When swarm cells appear
Swarm cells typically show up in spring and early summer, when a colony has grown quickly, forage is available, and brood boxes are crowded. A queen needs roughly sixteen days from egg to emergence. Cells are usually capped around the time the old queen is about to leave, and swarms commonly depart on or soon after the day cells are capped, though this timing varies and can be delayed by bad weather.
If you are unsure when swarm season ends where you live, ask local beekeepers. In many areas it tapers off by mid or late summer, but late swarms do happen. See also reading bee behavior at the hive entrance for signs that appear outside the hive.
How to inspect for swarm cells
During a routine inspection, check the bottom bars and lower edges of the frames in the brood boxes, because swarm cells tend to hang there. Tilting frames or lifting the top box to look underneath can help. During swarm season, inspecting about every seven days (see how often to inspect) is a common recommendation, since swarm preparation can move quickly. Write down what you find: eggs in cups, larvae in cells, capped cells.
What to do when you find them
Beekeepers use several approaches, and the best choice depends on how far along the colony is.
- Add space. If you find only empty cups, adding a super or a brood box and removing crowding may relieve the pressure. Rearranging frames, sometimes called checkerboarding, is another method, though advice on it varies.
- Split the colony. When cells contain larvae or are capped, many beekeepers split the colony so the bees’ urge to reproduce is satisfied without losing a swarm. See how to split a bee hive for walk-away splits and the use of an artificial swarm.
- Do nothing and accept a swarm. Some beekeepers allow it, especially if they can catch the swarm.
Why cutting out cells often fails
It can be tempting to remove all queen cells. Once a colony has the swarming impulse, this often does not stop it, and the colony may swarm anyway or build new cells. If you miss a cell, the colony may swarm with a virgin queen. If you do remove all cells and the old queen leaves, the remaining bees may be queenless. For this reason many beekeepers prefer a split to cell removal, though advice varies and some choose to remove cells in the early stages.
What happens if you do nothing
If the colony swarms, roughly half or more of the bees may leave with the old queen, and the honey crop usually suffers. The colony that stays raises a new queen, which then needs to mate and begin laying, creating a gap in brood production. Swarms can also land where people do not want them, though a swarm is usually docile because the bees have gorged on honey.
FAQ
What are bee cells? Bee cells are the hexagonal wax compartments in the comb. Workers use them to raise brood and store honey and pollen. Queen cells are a different, larger, peanut-shaped type.
What is the 3-3-3 rule for beekeeping? This is used in different ways. One version concerns moving a hive less than three feet or more than three miles. It is not a rule about swarm cells.
Do heavy bearding bees mean swarm cells are present? Not necessarily. See bee bearding to tell them apart.