It's getting near that time of year again so I thought it might be useful to talk about swarming. *Now I'm into year 4, I'm obviously an expert so I'm going to throw myself to the wolves and write what I reckon I know about swarming, pitched here with the assumption that new and prospective beekeepers are the intended readers.

I'm going to try and break this into three parts:
What swarming is and how, why it occurs and what can be done about it. (this bit)
What goes on, and what to look for inside the colony in the build up to a swarm
Basic Principles behind Managing Swarming with an Artificial Swarm.

What is swarming?
Basically reproduction at a colony level, i.e. how bees reproduce. When it comes to honeybees it is more useful to think of the hive/colony (I tend to use both interchangeably) as being the animal rather than individual bees.

When a colony swarms the existing queen and a good proportion, I'm not going to quote a figure here as different books, websites and groups of beekeepers will give you different percentage numbers, of the existing bees will fill themselves with honey, leave the hive, normally pitch up on a tree branch, fence post or somewhere equally inconvenient to collect them, relatively close by and look for a new home. Left behind is the existing brood, nurse bees and a number of queen cells from which new queens will emerge in approximately 7 days time.

When do bees swarm
Anytime from April to July (typically) dependent on a number of factors we'll look at shortly.

As beekeeper, why should I care if my bees swarm?
Saw someone post this reasonable question somewhere else recently.

Possibly the most important reason is consideration for your neighbours. Most people quite like [the notion of] Bees at the moment, but they don't tend to like a swirling mass of several thousand bees descending on their garden while they're sitting in it. Swarms also tend to view chimneys as suitable places to make a new nest and once they're established in a chimney they're a bugger to get back out again.

From a beekeeping point of view, losing the majority of your flying bees and having no new brood for a few weeks just before the main nectar flow starts also means that you get a lot less honey than you would otherwise.

So how do I stop them?
To be blunt, you can't. All things being equal that hive will want to swarm at some point.
What we try to do is manage that impulse to swarm. Both in terms of reducing their inclination to swarm in the first place and, when they prepare to swarm anyway, managing that so we hopefully don't end up with a big swarm hanging off a neighbour's tree while they're trying to have a BBQ. Dealing with their intention to swarm before they leave the hive not only means we don't have to try and retrieve them out of a tree, but we we have a number of options available to us as to what we do with the bees.

In our association we use the following graphic:

In order for bees to swarm, all three sides of the triangle must be true. Break that Triangle and they can't or won't swarm. It is obviously not that practical to remove the queen or the flying bees, so in employing swarm prevention measures we concentrate initially on trying to control conditions.

As 'conditions' is a pretty vague definition I've attempted to broadly classify some of the range of conditions that can influence the desire to swarm:

I'm not claiming this as an exhaustive list. The top three however are probably the most commonly cited conditions and can act in conjunction with each other to make a hive think it's time to swarm.

Lack of laying room
Talking in very broad generalisations, the books all reckon that queens can lay 2,000 eggs a day, I personally think this number is high and it generally won't apply at all times, but we'll stick with it as an example. At 21 days from egg to emerging that's 42,000 cells required just for brood. A National Brood box has a capacity of approximately 50,000 cells. That doesn't leave much room for pollen and nectar to be stored; which they will at the expense of laying room. If the queen has no room to lay this can trigger the desire to swarm.

Overcrowding and 'poor'/old queen
I've linked these together because I believe in some respects that they're quite closely related in terms of what is going on.

Another picture! This shows the approximate colony population over the course of a year. it's not entirely co-incidental that swarming tends to occur when the colony population is reaching its peak.


An important factor in the regulation of a bee colony is "Queen Substance", a number of Pheromones secreted by the queen and circulated by the workers around the colony.

As the queen ages, the potency/quantity (not sure) of this pheromone reduces. In a crowded hive, it can also become more difficult to distribute enough of the pheromone, both therefore can trigger the impulse to swarm.

For this reason a lot of standard Swarm prevention advice suggests keeping Young queens in the colony.

For both Overcrowding and lack of laying room, supering early can help alleviate congestion inside the hive and ensure that they have plenty of room to store nectar. WHen I have 8-9 frames of bees in the brood box I start preparing supers, when a similar number of frames in the first super are drawn and contain stores I start to add additional supers moving frames with stores up to keep empty frames immediately above the brood nest.

I tend to give a box of comb in the first instance (easier said than done if this is your first season) and then give them empty frames. I've absolutely no evidence for this at all but I suspect that busy bees with wax to draw might be slightly less inclined to think about swarming.

Time of Year/Weather
Jimbo reckons his colonies start thinking of swarming around the third week of May and consistently have done for the past 10 years. With a broad window of opportunity between mid April and July, having a sense of when your bees tend to get it into their heads to swarm comes in handy. The weather can have an impact both in terms of the build up and when a swarm will actually leave. This has been the wettest spring I've seen since I started and only one of my hives is strong enough as a result that I'd think them worth watching out for.

Genetics
I think this is a hard one to quantify but lots is made of "swarmy" bees and eyebrows are frequently raised if you've acquired your bees from a swarm to begin with. Quite why we're quite so willing to blame the bees for being swarmy rather than pointing the finger at the beekeeper I'm not sure but there we go.

I think we can probably safely assume that some bee colonies are more inclined to start preparing to swarm than others though.

Drones
I've included drones as a condition simply because in my limited experience I've never seen a colony try and swarm that hadn't raised their own drones and there weren't drones from other colonies hanging around.

While I do use Drone culling as part of my Varroa IPM I do like to let my bees raise drones. They want to for a start so I don't think that attempting to manage Drones as part of Swarm prevention is likely to have much effect, but it can be an indicator that they might be thinking about it.

Part II - What to look for inside the hive, coming next, comments, criticisms, corrections etc, in the meantime welcome.