Learn · 5 min read
A bee swarm in your garden: why bees swarm, and what to do
Every year in May and June lots of people come across one: a humming, beard-like cluster of bees hanging from a branch, a fence or the eaves. This is a swarm. It looks alarming, but it is actually a colony reproducing naturally – and bees are at their gentlest at this time.
Why do bees swarm?
Swarming is how honey bee colonies reproduce. When a colony grows strong, it raises a new queen, and the old queen flies off with roughly half to two-thirds of the workers to find a new home. The colony left behind carries on with the new queen. A swarm typically has 10,000–20,000 bees. In Hungary, May and June are the main swarming season.
As the old English beekeepers’ saying goes, a swarm in May is worth a load of hay, but a swarm in July isn’t worth a fly: a swarm that leaves late has little time to build up strength before winter.
Why is a swarm so gentle?
Before setting off, the bees fill up on honey – their provisions for the journey. They have nothing to defend – no comb, no brood, no honey stores – so a resting swarm almost never attacks. According to the Hungarian National Beekeepers’ Association (OMME), bees are usually completely harmless when swarming.
The cluster stays in one place for anything from a few hours to a few days, and usually moves on within a day. Meanwhile a few hundred scout bees look for a new home – a hollow tree, a cavity – and “report” on it with a dance. The American researcher Thomas Seeley showed that the swarm decides by a kind of vote: when at least 15 scouts gather at one site at the same time, the swarm gets ready to leave.
What to do if they settle at your place
OMME’s advice:
- Don’t panic, and don’t disturb them: no shouting, no swatting.
- Don’t hose them with water, don’t throw things at them, and don’t spray them with insecticide.
- Keep children and pets away, and close nearby windows.
- Let a beekeeper know as soon as possible.
Who to call
A swarm is collected by a beekeeper. On OMME’s website you can download a list of swarm collectors by region, with several collectors in Budapest too. According to Hungary’s disaster management authority (katasztrófavédelem), which runs the fire service, firefighters only step in if the bees pose a direct danger to life, for example at a school, a nursery or in a busy public place.
If you’re not sure they’re bees, check how to tell a bee from a wasp: for a wasps’ nest you need a pest controller, not a beekeeper.
Who owns the swarm?
Under Hungary’s 2013 act on neighbours’ rights, if the owner of a swarm that has flown off does not recapture it within two days, anyone who takes possession of it can become its owner. In practice, the swarm becomes a new colony for the beekeeper who collects it – so the bees are not lost.
If they’ve moved into a wall
If a swarm isn’t collected in time, the bees may move into a cavity in a wall, ceiling or roof. There they quickly build comb and store honey – a strong colony can store several tens of kilos. If they are killed at that point, the honey left inside starts to ferment and can seep through the wall, and honey and wax treated with poison have to be handled as hazardous waste. That’s why it’s worth calling a beekeeper in the first few days, and then sealing every gap so that a new swarm doesn’t move in.
Terms from the glossary
Sources
- OMME – swarm collection and wasp control (in Hungarian)
- Magyar Mezőgazdaság – Help, the bees are swarming! (in Hungarian)
- Seeley, Visscher and Passino, American Scientist (2006) – group decision making in honey bee swarms
- Cornell Chronicle – Honeybee Democracy
- UC IPM – bee swarms and bees in buildings
- University of Georgia – honey bee swarms and bees in walls
- Act CLXXIV of 2013 (neighbours’ rights), section 2 (3) (in Hungarian)
- Baranya County Disaster Management Directorate – wasp control and swarm collection (in Hungarian)
- Phrases.org.uk – “A swarm in May…”
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