Two Reasons to Swarm

Like us, bees need space in which to live their lives. They need a place to raise brood, to store honey and pollen and more. In the spring and summer, a colony can expand quite dramatically, both in numbers and in the space needed.  When space starts becoming too limited, bees need a solution.

Their solution is to swarm.

But there is a broader reason why bees swarm, beyond simply needing more space.

When we think of bee reproduction, we think about the queen laying eggs, the eggs emerging as adult bees and so on. This represents reproduction at the level of the individual bee.

When bees swarm, a single colony becomes two. This can be considered reproduction at the colony level and it is an essential element of the way bees live and survive.

Swarming for Space

The most obvious and easy-to-assess reason bees swarm is simply to resolve a lack of space. While this happens in nature when a colony grows beyond the capacity of its home, it is particularly common in the small, purpose-built wooden boxes we call a beehive.

We actually cater quite well for our bees, using structures that be expanded with relative ease. This allows the beekeeper to hopefully anticipate the potential for swarms and act accordingly. But that isn't always possible, and bees may eventually swarm.

Bees swarming

The basic principle is rather simple and boils down to the following process (somewhat simplified and expanded below):

  • For whatever reason, the colony decides it needs to swarm
  • Future queens are prepared, in queen cups
  • Before any new queens emerge, the existing queen and about half of the bees in the colony leave the hive, searching for another home
  • The first queen in the old hive will hatch and make sure she becomes the only adult queen
  • The remaining bees consider her their new queen
  • We now have two colonies, each approximately half the size of the original one, living in different locations

As with anything associated with bees, there is nuance to why and how they do this, but that is the swarm process, in a nutshell.

Swarming to Reproduce

The colony acts, in many ways, as an organism unto itself. The collective "wisdom" of the colony greatly outweighs the awareness of any one bee. Like any organism, the colony needs to survive and is also motivated to reproduce. It is through swarming that the colony reproduces.

The creation of two colonies from one is a natural, positive event supporting the rapid growth of a colony. With a queen in each colony, separate brood-rearing efforts can take place, therefore accelerating the number of bees created collectively.

What Happens During a Swarm

The Decision to Swarm

As we discussed above, some trigger will exist to initiate the swarming intention. In our example, we have a beehive where the colony is starting to exhaust the space available, as it fills frames with brood and honey. So, the colony elects to swarm.

Preparation for Swarming

Queen cups are created by workers on a regular basis. But the queen will not ordinarily lay eggs in them. That changes when swarming is imminent. Her laying an egg in a queen cup illustrates an amazing level of planning - she plans to leave and she is also preparing a queen that will take over in the existing hive.

Bee Swarm

Up until this point the old queen has been laying eggs and is heavy. She isn't in a position to fly well. Since she will be leaving soon, she needs to lighten up. The workers achieve this by reducing her feedings and she will stop laying eggs. This means there is a gap in the egg-to-adult timeline of the colony.

The Swarming Event

Soon after all this preparation the swarm will start. The queen and 50% - 60% of her offspring will leave. There are usually a few steps to this relocation to a new home.

  1. Leave the hive and temporarily move to an interim location. In what is one of nature's more dramatic events, tens of thousands of bees will stream out of the hive together. They will choose a nearby location as an interim place to rest, keeping in mind that the queen isn't a great flyer at this point. This initial stop might well be within a stones throw of the original hive.
  2. Scout the nearby area for permanent locations. With the swarm clustering around the queen at the interim location, scout bees will then start checking the area for suitable final locations. At this point some magic happens, including a remarkable form of debate and voting among the scout bees. This is described in glorious detail in the beautiful and iconic book Bee Democracy by Thomas D Seeley.
  3. Move to the final location. With that decision made, democratically, the swarm will fly off to the chosen location and begin its life in their new home.

The group of bees swarms is called the prime swarm. Back at the original hive, the first queen will soon emerge from her queen cup. She will hunt down her as-yet-unborn sister queens and kill them while they remain in their queen cups. She will be helped by some worker bees who help clear the wax capping, so she has access for the killing. Once she has completed that process, she now becomes the queen of the initial hive.


At this point, there is another direction the colony can take. The new virgin queen and workers may ALSO swarm, again with a significant number of bees from the colony, though smaller than the original swarm. This secondary event is called an after swarm. In rare cases, the process may occur again and again - multiple after swarms - until the hive is depleted.

How can I help prevent the chances of a swarm?
Depending on the type of beehive you use, you have the option to add new boxes to expand the available space.

The Beekeepers View

Watching for Signs of Swarming

bee swarmThe underlying conditions are the first sign of a potential swarm. If your bees are expanding rapidly, are in full-blown brood-rearing mode and storing large amounts of honey, you should be carefully monitoring the use of frames within the hive.

It is your role to watch for these signs and take early, proactive action to avoid swarming.

A Source of Bees

Swarming is not bad! As a beekeeper, swarming bees can be an excellent source of bees when looking to establish a new hive. Catching a swarm is one of beekeeping's most exciting and satisfying steps and it is important for the beekeeper to realize the opportunity here.

Catching a swarm is not quite as scary as it might seem at first. PerfectBee doesn't recommend this as a source of bees of the first time beekeeper, but as you gain experience it's a very viable option.

For the layman, a swarm of bees is sometimes a terrifying thought, even though that concern is generally overstated. Around the country, beekeepers promote "swarm catching" services. Given that the end result may be a new colony - for free or even for a small profit - it's something of a win-win, when done for the right reasons.

22 thoughts on “Why and How Bees Swarm”

  1. Rohan Harindra Wickramasinghe

    I have heard it said that strains of honey bees in some regions of Sri Lanka are genetically more predisposed to swarming than those in other parts of the country. Is that really a matter of inheritance or due to different climatic conditions? What is the experience in other countries, please ?

  2. I have been keeping bees for a very long time and have enjoyed all of PerfectBees education as a refresher. Thanks for all you do. I have been referring your site to any new beekeepers and interested folks I come across.

    One thought on Swarms: When I was first introduce to beekeeping I expanded my bee yard solely collecting swarms. It was as you mentioned an inexpensive method to expand. However in the past few years I was introduced to OTS “On Time Splitting” order to maintain strong colonies. The club I belong to holds a “hands-on-workshop in late April to introduce the process and it’s benefits.

    Thank you for your generous pieces.


  3. After reading your article, I got a little nervous, as I just recently bought my two nucs for my weekend getaway place. Now I have to worry about the bees leaving me. oh madonna mia.. now I need to put empty nuc boxes near the area. Thanks for the info.

    1. Drawn Comb is the completed wax honey comb that bees will “draw” onto a frame or foundation. The comb can be used to raise brood or store honey and pollen.

  4. To Lynn, Gary and Scott,

    Swarms! What fun. Count your blessings if you have a chance to catch one and watch your cursing (chuckling) when its your own hive that swarms. When your own hive swarms its a lost season and at least where I’m at, because of the short season, it will mean close observation and likely feeding to make sure the hive that swarmed is able to put away enough stores to make it through the winter.

    That said, its always advantageous to have a nuc box or empty hive situated nearby in case one of your own hives swarms. After all, these are free bees! DO NOT place any honey in a swarm box, but instead, bait it with drawn comb without honey. Honey will attract robbers and a swarm will avoid the bait hive you have set out. You can also use a commercial swarm attractant if you want but use it sparingly. Too much and the bees will avoid it as well.

    Did you know that only about 1 in 5 swarms survive? A swarm must quickly find a suitable home, build comb and put away enough stores to make it through their first winter. Your catching the swarm not only adds to your apiary but also gives the bees a much greater chance for survival.

    1. I’m an incredibly lucky 1st year beek w/an overwintered hive. Watching to make sure they don’t swarm. I’m sure I’ll read this article over again (& again…) in the next few days. THANKS!

    2. I recently started keeping a hive. I had never really thought about it until I saw a swarm in my neighbors tree. I then called a friend who has bees and he came and captured the swarm. Now the colony is in my yard so I’m reading this info to learn more about what I’m doing.

    1. I placed an empty pot same as the old one nearby. they didn’t select the hive and the swarm came out and clustered. I collected the swarm and put that in the nearby hive. I saw no activity for 3 days and at day 4 I placed the swarm in the other empty hive but the next day the swarm came out , I put in the other hive same was the case . I tried all four hive I have empty but failed to settle the swarm and I let them leave at the end.
      I saw that swarm doesn’t settle nearby permanently.

  5. I have concerns that my 2 hives will become 6 very quickly. Does this mean beeks should have a spare hive at all times?

    Thank you!

  6. I’m relatively new to beekeeping. My neighbor started his first hive 2 years ago. He now has 4 hives outside and an observation hive indoors. This season, we captured 11 swarms, starting in March, which is very early for swarming, and with the last one in September. I kept one of the early June swarms to begin my first hive.
    Capturing swarms is fun. The little ladies are very passive and cooperative during a swarm.

    He had a nuc box from his original purchase and I built two additional nuc boxes for capturing the swarms.

  7. According to other beekeepers, when the workers sense either that the old queen is failing , or that hive is getting too crowded, they will take a “fresh” egg and place it in a queen cell, and take care of it. When the new queen hatches, the old queen will try to kill her, but she is protected by the workers. The old queen will then leave the hive (swarm), leaving a virgin queen in the hive. She now has to mate and then start laying eggs. This time period causes the hive to weaken because some bees die before the new queen gets started. I used to cut all queen cells out that I found, but finally realized that if the old queen suddenly fails, the bees are rushed to build a queen cell (that sometimes isn’t suitable) before they can raise another replacement queen. Then we get into laying workers. Only solution I,ve found there is to divide the hive into two boxes, see which one is queenless, and buy it a replacement. At least you’ve saved half of them.

  8. Today i caught a swam of bee …swaming from my old langtroth hive…its very impressive to increse the no

  9. Anne-Mary Judge

    We just caught a swarm from one of our hives this afternoon, are hoping they’ll stick around in their new digs.

  10. Incredible how they have everything down to almost a science. Our local beekeepers association has a couple of folks who will catch swarms for people. They are presenting at our April meeting. Looking forward to their presentation.

Leave a Comment

Your email address will not be published. Required fields are marked *