New queens will be raised and just before they hatch out of their cells, the old queen leaves with most of the workers.
They depart en masse in a tight cluster - the queen is vital to their survival so she's in the middle, well protected.
The swarm will often settle on a tree branch or fence or some other structure from which they hang in a ball.
From there, scouts go out, looking for a new home.
They'll report back over a period of hours or even a couple of days. Somehow, the swarm will reach a consensus about their new abode and will launch into flight again, heading directly there.
They gorged themselves on honey before leaving, so are primed to make wax and start building honeycomb, in which the new bees are raised and food is stored.
"A swarm has only one thing on its collective mind: finding a new home. As long as you don't disturb them, they are extremely unlikely to cause you any trouble, so there's no need to be nervous," says Jake Schultz, who's leading UCOL's new Certificate in Apiculture (beekeeping).
A swarm is a particular and distinctive sight (see photo). You may see many hundreds of bees buzzing around a particular tree. That's not a swarm. Rather the bees have found a choice food source.
Also know the difference between bees and wasps.
"Wasps are smooth and hairless, with bright yellow and black stripes. They also have a tiny 'waist'," explains Jake. New Zealand honeybees may have dark or yellow stripes and their bodies are furry.
So if you see a genuine swarm, grab a quick photo if possible and call in a beekeeper.
Report the size, location, and how long the swarm has been there.
You can reach Jake on 022 068 8734 or ucolbees@gmail.com - you'll help the student beekeepers with their learning and UCOL with its apiculture research.