Understanding Swarms: Prevention, Capture and Rehousing
A swarm is a natural sign of a healthy, thriving colony. Learn how to read the signs early, prevent unwanted swarms and safely capture them.
A swarm is one of nature's most spectacular sights — tens of thousands of bees leaving their hive in a buzzing cloud, settling briefly on a branch or fence post, and then moving on to a new home. For the beekeeper, it's a mixed experience: a sign that your colony was healthy and strong, but also a loss of half your workforce at exactly the wrong time of year.
Why Bees Swarm
Swarming is the honeybee colony's primary method of reproduction. When a colony becomes large, congested, and the queen is running out of space to lay, the workers begin raising new queens. As the first new queen cell is nearly ready to hatch, the old queen leaves with roughly half the colony's adult bees — this is the swarm.
The swarm clusters nearby (usually within 100 metres) for anywhere from a few hours to three days while scout bees locate and agree on a new nest site. Then, when consensus is reached, the whole cluster flies to its new home — often a hollow tree, a cavity in a wall, or an unoccupied hive.
Back in the original colony, the first virgin queen hatches, kills her sisters (or the workers do), mates on her mating flights, and begins laying — re-establishing the colony, now with a younger queen.
Swarm Season in Sweden
In Sweden, the main swarming season runs from late May to mid-July, peaking in June. The trigger is a combination of colony strength, congestion, and day length. A strong colony on a warm, still day in early June with queen cells developing is a swarm risk — inspect every 7 to 10 days during this period.
Reading the Warning Signs
Queen cells: The most reliable indicator. Queen cells built along the bottom edges of frames (swarm cells) indicate the colony intends to swarm. Emergency queen cells built mid-frame (after a queen has been lost) are different — but still require attention. Check every frame systematically.
Congestion: Bees clustering densely outside the hive entrance (bearding) in warm weather is normal ventilation behaviour, but during May–June it can also signal that the colony has run out of space inside. Add a super if you haven't already.
Egg-laying reduction: As queens prepare to swarm, workers slim her down so she can fly. Egg-laying slows or stops in the week before swarming. If your usually productive queen has apparently stopped laying, check immediately for queen cells.
Prevention Strategies
Inspect regularly. During May–June, inspect every 7 days without fail. This is the single most effective prevention strategy.
Provide space. Add honey supers before the colony needs them. A hive with no space to expand is a hive that will swarm.
Destroy swarm cells (selectively). If you find queen cells, you have options — but simply cutting all cells is only a short-term fix. The colony will build more within days. Use cell destruction as part of a broader swarm management plan (see our article on the Demaree method).
Clip the queen's wing. Clipping one front wing prevents the queen from flying. The swarm will still emerge but cluster immediately outside the hive entrance, unable to leave. You can then recapture it easily. This is controversial — some beekeepers consider it unkind — but it gives you time to respond.
Capturing a Swarm
If a swarm has already left, act quickly. Swarms are at their gentlest when clustered — the bees have gorged on honey before leaving and have no home to defend.
What you need: An empty brood box with frames (drawn comb is best), a sheet or tarpaulin, a smoker, and gloves.
On a branch: Place the box under the cluster. Give the branch one sharp shake. The bulk of the bees will fall into the box. Place the box on the sheet with the entrance slightly raised. If the queen is in the box, the remaining bees will walk in. If not, the cluster will re-form on the branch.
On a flat surface (fence, post): Use a bee brush to gently sweep bees into the box. Be patient — this takes time.
Once the bees have entered the box, leave it in place until dusk, then close the entrance and move it to its permanent location.
Rehousing the Swarm
Install the swarm in a clean hive with drawn frames if possible — foundation works but slows establishment. Feed immediately with 1:1 sugar syrup to stimulate comb building and brood rearing. Check for a laying queen after 10–14 days. A swarm that has settled and has a laying queen will build up rapidly if there is a nectar flow available.