Why do Bees Swarm?

When do Bees Swarm?

Why do Bees Swarm?

One of the most disappointing things that can happen to a beekeeper is to have a hive swarm. After it happened to us, we decided we really needed to find the answer to why do bees swarm? If we knew why, maybe we could prevent it from happening in the future.

When we’re talking about bees swarming in this article, we’re not talking about the aggressive attack that can come from a hive when it feels like it’s in danger. We’re talking about the natural dividing and multiplying of a hive.

Now, if you’re not the beekeeper a swarm is an amazing thing to see. We get calls quite often from people who have a ball of bees on a tree branch and are wondering what to do with it. Most of the time, we’ll go get it or call a beekeeping friend who will go get it.

When bees are swarming they are actually the tamest they’ll probably ever be. First of all, the bees are weighted down with full bellies of honey so they can’t fly very fast. And secondly, they have two goals; protect the queen and find a new place to live. Everything else is secondary to those two goals. So, they ball up and surround the queen and wait for the scouts to tell them where to go.

It’s very unlikely to get stung by a hive that is swarming but if you do there are many home remedies for bug bites and stings that are great to know about.


Why do Bees Swarm?

Bees swarm for a couple of reasons but the number one reason is that their living space is too crowded. Things are rocking along in the hive, the queen is laying eggs, the workers are caring for the brood, honey is being made, honeycomb is being drawn out and filled. There is plenty of nectar and pollen for the bees. The weather is nice and sunny without being too hot. It’s like bee paradise.

Then all of the sudden, some bees decide it’s too crowded and convince the queen to leave with them. Or maybe the queen decides it’s too crowded and summons the workers to go with her; we don’t really know whose idea it is to begin with. But the queen is a good ruler and would never just up and leave her subjects. So she makes sure they have plenty of brood – enough to replace all the bees she’s taking with her. Then she stops laying so she can slim down a bit before she flies off.

The workers who are going with her stop foraging and start eating. They pack all the honey they can into their little bodies in preparation for the flight. Scouts start looking for a new place to build a home.

This behavior starts to worry the bees who are staying behind so the young workers who can produce wax start constructing queen cells towards the bottom of the frames. And when the first of the queen larva reaches pupating age and her cell is capped, the old queen knows it’s time to leave.

So, she and about half the hive leave to find a new home – it might be an old tree or abandoned building. Hopefully someone will spot them and call a beekeeper who can put them in a box in his apiary or give them to a bee farming friend.

The bees that stay behind will (ideally) raise a new queen and life will continue as normal. They are about three weeks behind in work but they now have space to grow and all is good.


When do Bees Swarm?

Fortunately, it’s very uncommon for a hive to swarm the first season. They just haven’t had time to set up home and fill it all up to the point of needing extra space in just a few months. However, in subsequent years they will fill up their hive sooner and swarming will be more likely. 

A good rule of thumb is that when you notice that seven of the 10 frames are drawn out with wax, it’s time to add another. When the lower deep has seven frames full of wax, add another deep. When that second deep has seven frames full of wax add a queen excluder and a honey super. When the super is 70% drawn out, add a second super. Keep adding a super each time 70% of the frames are drawn out with wax.

This means that in the spring and early summer when nectar is really flowing you have a higher chance of the bees swarming. You’ll want to make sure to check on your hives every 10 days or so during the nectar flow and add boxes as needed.

When the nectar flow slows down so will hive growth but don’t think you no longer have to check on them. You’ll want to make sure to continue adding boxes when the top box is 70% full of drawn out wax. If a hive swarms late in the summer or early fall, it might not be able to recover before winter sets in. So be sure to give them the room they need when they need it.

Speaking of late summer, sometimes the hive isn’t crowded, it just feels that way to the bees because it’s hot and there isn’t enough ventilation. You can provide a little extra ventilation by gluing a short piece of a popsicle stick to each of the corners of the inner cover. If you live in a warm climate you could just do this to all of your inner covers as part of your bee hive plans since you don’t have to worry about harsh winters.

Even if the hive has plenty of room, if the queen is several years old there is the likelihood of the hive swarming. Because the workers will start raising a new queen when they think their queen is getting too old to lay eggs, many beekeepers will requeen their hives every year to help keep a hive from swarming. This works really well if it fits in with your beekeeping strategy.

One last thing, if you notice that the workers are making queen cells and think they might be preparing to swarm you can remove all of the queen cells by cutting them out of or off the frame. The hive will not swarm if there is not a replacement queen in the works. But you have to be certain you get all of them. It only takes one queen larva to reach pupating age to let the old queen, who already wants to leave, know it’s time to go.

So, why do bees swarm? Because it’s nature’s way of making sure that bees divide and multiply so that they will survive. Of course in nature this is a wonderful thing, but in apiaries swarming can lead to weak hives and less honey.

Have you ever had a hive swarm?

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