Reasons why extra hive space may not reduce swarming

“How can I prevent swarming?” is a common question. An equally common answer is, “Give the bees more space so they are not crowded.” From this we get, “Crowding causes swarming.” Let’s look at that a little more closely.

In his book Honeybee Democracy, Thomas Seeley writes, “To this day, no one knows what specific stimuli the worker bees are sensing and integrating when they make the critical decision to start the swarming process.” To me, that statement makes a whole lot more sense than, “crowding causes swarming.”

Swarming correlates with crowding

Seeley admits that several things correlate with swarming, including “congestion of the adult bees, numerous immature bees, and expanding food reserves.” But causation and correlation are two different things. We don’t know if crowding causes swarming or if swarming causes crowding or if there is a third factor that causes both. All we know is that these conditions often occur at roughly the same time.

I can say for a fact that a colony will often release a secondary or tertiary swarm shortly after the first. The colony at that point has lost perhaps 2/3 of the adult population, so it is no longer overcrowded. Still, the swarms leave anyway. Swarming is complex, and the reasons for things are not at all obvious.

Experimenting with bees

Now, since there is a correlation between crowding and swarming, it makes sense to experiment with crowding to see if we can prevent swarming by alleviating the crowded conditions. What some beekeepers have found is they can delay or sometimes prevent swarming by opening up honey barriers that have been built above the brood nest. There is nothing wrong with trying these methods, even though we can’t say exactly why they sometimes work.

However, these machinations, such as spreading the brood nest or checkerboarding above the brood nest, need to be performed in advance of the colony’s decision to swarm. Once the colony has made the decision, there is little a beekeeper can do—short of splitting—to stop the progression. Like an avalanche tumbling down the mountainside, once it starts it just keeps going.

So if you want to prevent swarming using one or more of the “foolproof” methods that have surfaced over the years, you must be proactive. You cannot wait until bees begin flowing from the hive entrance to drop a super on the hive.

Unfortunately, this is the point when I usually hear from beekeepers. “I thought my bees were going to swarm so I gave them an extra super and they swarmed anyway.” Or worse, “My mentor said my bees were going to swarm, so he added a super and they swarmed anyway.” Mentor? If the bees have already decided to swarm, you can add 17 supers and it won’t change a thing.

Swarming is a process

To prevent swarming, you must plan in advance of the bees.
To prevent swarming, you must plan in advance of the bees. © Rusty Burlew.

So when do the bees decide to swarm? Well, it’s hard to say. But the first thing you might notice is the construction of swarm cells, or perhaps backfilling of the brood nest with nectar. Once the queen cups are begun and an egg laid, it takes approximately 16 days for a mature virgin to emerge. That tells you that the decision to swarm must come at least two weeks before the event.

During that time, a lot of changes are made in the colony. Queen rearing goes full throttle. Egg laying by the queen is reduced, and the queen is made skinny so she can fly. Also during this time, the workers’ wax glands are gearing up for production, the workers stuff themselves with honey, and the whole lot of them become lethargic—often hanging around the hive entrance waiting for the signal to leave. In addition, scouts may start looking for real estate.

Too little, too late

With all the preparation that takes place within the colony, and all the physiological changes occurring within the bees themselves, you can see that dropping a super on your hive will make little impression on them. They are simply not going to say, “Oh look, more space! Let’s call this off.” Nope. Not on your life.

The take-home message is clear. There is nothing wrong with playing with your bees and trying to prevent them from swarming. We’ve all done it. But if you’re serious about it, you need to start before they start. Have a plan. Know what you’re trying to do, and don’t be surprised if they end up swarming anyway.

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  • Hi all

    Most experienced beekeepers know techniques that drastically reduce swarming. The main problem is that sometimes spring comes on so fast that there isn’t time to do the work.

    The easiest thing to do is to add supers and often this is enough. The most radical is to divide the colonies into two or more, and while this is almost certain to prevent swarming, it can also prevent getting any spring honey.

    The best plan is to remove brood and bees from the better colonies, just prior to the historic swarm period, These can be use to make splits. By taking a few frames at a time, even several times, one keeps the colony from building too fast.

    Experience shows that the colonies will raise more brood than they would have if they had been left alone, creating a net gain and preventing swarming at the same time. The main problem with this technique is that it requires years of experience to be able to judge when and how much to take.

    Most people are too timid and don’t cut the hives back enough. Experienced beekeepers know that the bees will bounce back, will be in better shape than if they had been left alone. Good timing is everything.


  • Hey, Rusty!
    I’m told that a slatted rack on the bottom of the first brood box is a deterrent to swarming (?).

    Also, when drone cells start showing up is another indication of preparation by the bees before swarming. What say you?

    Green Bay, Wisc.

    • Ken,

      I’ve had slatted racks on all my hives for at least ten years, and I have no shortage of swarms.

      Drones signal the beginning of swarm season because you can’t have reproductive swarms without them. Likewise, when the drones are being tossed, swarm season is definitely over.

  • I had long thought it was common knowledge that you can seldom stop swarming once the girls start making preparations?

    As for the reasons for swarming? Who really knows? We know that lack of space can trigger it… either from overpopulation or things like being honey bound. I think it’s also clear that there a biological imperative at work as well. The colony’s ‘biological clock’ is ticking. Since honey bees are rather notoriously opportunistic, it’s hardly surprising that they’d take advantage of such surpluses.

    I’ve always guessed that swarming was triggered from one from column A and one from column B, so to speak. I really lean toward the idea that they’re always in ‘swarm mode’ and just waiting for the conditions to get right. That would seem to make the most sense from an evolutionary standpoint.

  • From reading, it seems a Snelgrove board can work to prevent a swarm if placed at the right time and used correctly. “The Many Uses of a Snelgrove Board” by M. W. Shaw is a good resource.

  • Hi Rusty,
    I am a very new bee keeper and, per your recommendation, I have a slatted rack on each of my hives. I have no experience with hives without a slatted rack. I live in Wyoming – very cold winters and very hot summers. I’ve noticed that about every fourth bee exiting the hive ends up flipped on its back trying to exit the hive. Do you think this problem has to do with the slatted racks or does this also happen in hives without the slatted racks. The racks are installed with the deep side down and the the 4-inch wide solid part to the front. Thank you for your time.

  • Thank you rusty! For all the swarming advice! I beekeep for the love of the bee and the improvement of the bee population, but honey is nice to get too. Since my bees have decided to swarm soon, I felt a lot of pressure from my surrounding keepers to prevent at all costs, when my inclination is to let them swarm and go from there. Honey is a wonderful reward for a keepers efforts, but it isn’t more important than the bees. Every keeper I’ve spoken to immediately says “well if they swarm there goes your honey harvest.” Still, I’m not too worried.

    Thanks so much for your wisdom on this touchy subject.

    • Alison,

      “There goes your honey harvest.” That’s nonsense, too. I have lots of swarms and more honey than I can handle. People so enjoy being melodramatic.

  • I have been laid up in the hospital for about two weeks or twenty days. When I inspected my bees prior to beginning my visit I noticed I had quite a bit of new brood and young bees. I don’t recall any supersedure cells. What are the chances of my girls taking a midnight escape? Seems likely they may have another hatch before I can get to them.

  • One of my new nucleus colonies just swarmed. I set the new hive up with a solid bottom board, screened bottom board, and a slotted bottom board. I put the 2nd brood box on when about 7 frames in the bottom brood box were covered with bees. Two weeks later the queen was gone, with her gang. They hadn’t even started building out the 2nd brood box. Why bees swarm is a mystery…and highly annoying.

    • Julian,

      I wouldn’t say the reason for swarming is a mystery. Without colony reproduction, it wouldn’t take long for honey bees to completely disappear.

  • Hi Rusty,

    I started with two hives in 2015. They both swarmed and I caught two of them. 4 hives going into and coming out of winter. I tried to prevent swarming spring 2016 – checker boarding, splitting, rotating brood boxes and they still swarmed. Also started having swarms fly in from somewhere else, which was so cool! I had 11 hives coming into spring 2017. 7 out of the 11 swarmed. So I had 26 swarms out of the 7 hives plus I had 3 large swarms fly in from somewhere else. I tried to prevent by rotating brood boxes, removing the queen cells every 7 days, replacing brood frames with empty ones and giving them enough room using supers. I still got 260 # of honey too! I sold all 29 swarms. Went into winter with 12 hives and into spring this year with all 12. This year I did nothing but rotate brood boxes. That was the only time I opened them up this spring other than putting supers on. They are all healthy and producing a lot of honey. Last fall I started putting these light weight fence poles around the perimeter of my electric fenced in bee yard. 8 total. I put on each an old sock and saturated these soxs with original pine-sol. We have a lot of black bears in the area and I read somewhere bears don’t like the smell. I do it religiously every night. (Of course not through the winter). All 12 of these hives are doing amazing this year. I have 2- 4 supers on all of them. Not one of these hives swarmed this year….not one swarm flew in either.

    So….I did nothing with opening up my hives and letting all those bee smells saturate the air and also just let them do their thing. Plus, I have the smell of pine-sol flowing through the air. Not sure if it’s a combination of both of those or not to explain why I had 0 swarms. What do you think?

    Linda from NY

  • Ha Rusty this is what I have been trying to do for the last 2 years I do complete inspection every other week on all the hives it is a lot of work but it has helped me control the swarming I was doing them every week but when I found out how long it takes a queen to be born that is when I backed off a little. doing my inspection I move all brood down to the bottom every time and if there is a lot of capped brood I will add another box on top of them, for when they are born. for them to have space to move, it is drown comb and if I do not have enough of that I checkerboard board with new and used all the stores go on top I also use non restricted brood areas I have 20 hives and it is a lot of work but it has really helped if I see and starter cups I remove them I keep notes as well because with so many hives I can not remember what I seen in each hive. since I have been doing this I have not lost any bees so far. but it is something I tried doing and just thought I would share it with u. u have a wonderful day and I think u do a wonderful job I enjoy reading every thing u write

  • I believe there are two types of swarms: reproductive and congestive. Instinctively bees swarm to reproduce. This reproductive swarm usually occurs before the main nectar flow so that both the parent colony as well as the swarm colony have the greatest opportunity to grow and survive the upcoming winter by taking advantage of the soon-to-be flow. In order to head off reproductive swarms, beekeepers need to be proactive a few weeks before the main nectar flow. Here in mid-MD, that would mean, perhaps, making splits such as removing the queen via a reverse split in mid-April. On the other hand, congestive swarms can occur at any time that the bees feel there are too many adult bees in the hive, too few open cells for laying, or too little space to process the incoming nectar. I think it is this congestive swarm that most of us are concerned about preventing and attempt to do so by adding boxes, opening the brood nest, checkerboarding, etc. Am I correct in this line of thinking?

  • From reading, it seems a Snelgrove Board would prevent swarming if placed at the correct time and used correctly. “The Many Uses of A Snelgrove Board” by M.W. Shaw is a good resource about how to use one. I think I need to practice with empty boxes and a board to get it down correctly.

  • Hi Rusty, haven’t posted in a while but been reading everything. Both of my colonies died last winter – one went into fall queenless I believe and the other made it right to the end of April and then condensation got them. So I started over this spring with 3 packages in my redesigned top-bar hives. I made them so I could incorporate quilt boxes.

    I have left them plenty of room as they built up but one colony (actually in the same hive body as my swarm last year) seems to have decided to prepare to swarm or supersede? There are queen cups as well as at least 8 capped queen cells. Both on the sides as well as the face of the comb. I saw no eggs or larva – just capped brood – so wondered if they are superseding their queen. Couldn’t find her either.

    So…I’ve never done a split before but don’t want to lose a bunch of bees either. I took two bars with capped brood and 5 of the capped queen cells and 1 bar of honey and put them in a nuc box. I left the other bar with 3 capped queen cells in the original hive because of the chance they are trying to replace a dead or poor queen.

    Am I nuts? Should I have removed or crushed all the queen cells? It seemed like too few bees in the nuc, should or could I move a bar of bees and capped brood to the nuc from one of the other colonies?

    Thanks so much!

  • Hi

    Totally agree. Natural queen cells are too good to waste. If you find them and can use them, lucky day. There is some talk about “using swarm cells breeds bees that swarm.” Not really true, breeding bees is not that simple. Besides, swarming is what bees do, given the right conditions.


  • Hi Rusty,

    You have helped me several times over the last year and I always find your advice to be sound and well thought out. I need your opinion on a little problem. I have 13 hives and doing inspections today, I noticed that 3 of my hives have a massive amount of swarm cells and I think 1 of the 3 may have already swarmed (and it was my strongest hive). We went through the hive twice and could not find our marked queen. There were probably a dozen queen cells. Most were capped, except one or 2 that looked like they may have already hatched (although, we couldn’t find the virgin queen either). I did an inspection 2 weeks ago and there were no queen cells (or cups). The strange thing is that all 3 hives have lots of space. My hive configuration is the following –> Screened Bottom Board, Slatted Rack, (2) Deep Brood boxes, Imirie Shim, Queen Excluder, Medium Super. I have had the Medium Supers on for a month (because they were at blueberry pollination). All 3 hives that have swarm cells, still have not built any comb in the Medium Supers. I find bees up in the super. But for whatever reason, they are refusing to build comb there. The rest of my hives are all doing great and all have the same configuration. No swarm cells in the other 11 hives, and they are all building comb in their supers and filling it with honey. I don’t know why 3 hives are refusing to build up there. I even put a couple frames of drawn comb in each of the supers. I suspect that the reason they are swarming is because they think they are out of room (even though they are not). I was planning on splitting my hives this week. Will that stop my other 2 hives (that still have queens, but around a dozen swarm cells) from swarming? Would I just remove the frames that have queen cells and place them in a Deep or nuc with some frames of brood/bees? I have lots of extra equipment. I just don’t want to lose anymore bees. I was heartbroken to see that my strongest hive had lost their queen and that she took a large amount of the population with her. I put a swarm trap out (with some Lemongrass oil). But I am not sure if that will work because I looked all over our property (high and low), and couldn’t find the swarm. She had to leave recently (if she did) because there are still lots of uncapped larvae that don’t look much older than 3 days. Any advice you can give me would be greatly appreciated!

    • Nate,

      I’m not sure what your question is. A healthy colony will swarm. It’s the honey bee way of reproducing. Ten empty boxes piled on top will not stop a swarm once the bees have the reproductive urge. Also, virgin queens are hard to spot because they are often small. You may have just missed seeing her. Honey bees will not draw out comb if they are not ready, and since all colonies are different just like children are different, you can’t expect them all to behave the same way. You will always be frustrated if you try to “make” bees do something. You just give the bees resources but let them make the decisions. All beekeepers lose an occasional swarm. It happens. You just move on.

  • Thanks Rusty. I checked the nuc a couple days ago and the cells are still capped but I thot it was a bit early. Never looked in the other hive box but they were acting pretty normal so I’m hoping I averted a swarm this time.

    Thanks again.

  • Rusty,

    It seems heavy-handed, but what would happen if you cut down a queen excluder and secured it in front of the entrance? The workers could still enter and exit freely, but the queen (and drones) would be imprisoned in the hive, thus preventing a swarm.

  • An update. I’ve been waiting to see if I was going to get a queen or 2. The hive I split wasn’t getting ready to swarm…the queen must have failed. Glad I left 3 queen cells in there! They now have larva and capped brood and are looking healthy. The nuc has a good queen back as well. Got larva and capped brood there too. Just finished a new hive so will be moving the new colony into it in the next day or so.
    First successful split! I’m pretty elated! Thanks for your advise!

  • Rusty
    You have given me helpful advice in the past. I am a novice beekeeper (3rd year, South Central PA) with two hives that appear to have successfully overwintered as of today. I have been feeding both with fondant and pollen patties. As this is the first time in 3 years that my colonies survived the winter I’m uncertain how to proceed in the spring. One of the colonies was very strong going into winter with numerous bees and much stored “honey” (from syrup in the fall) and still has a lot of bees as evidenced from the number of bees visible on warmer days. I have not yet inspected either colony this spring (March 25) but plan to look for queen cells by tipping up the brood boxes in a day or so, weather permitting. The hives have 2 deep brood boxes and a super. What should I be looking for other than the presence of queen cups and queen cells? I am concerned about swarming because this is such a numerous colony. If I find queen cells, I will probably set up a nuc to bank the queens. Does this seem a reasonable approach to a numerous colony in the early spring? Thanks for any advice.

    • Pam,

      Reasonable, yes, but you still need to think about swarming. Sometimes they will swarm even without leaving a new queen behind. You might want to split the largest colonies to avoid a swarm. Later in the year you can recombine if you don’t want to overwinter extra colonies.

  • Thanks for the help, Rusty I plan to follow your advice on “How to make a swarm-control split.” However, I need to make sure there are drones around, correct? I am in South Central PA. How do I know there are drones, other than seeing them in the hive or on the landing board? You indicated that it was best to confine the queen. Do you mean in a queen cage? and just temporarily, correct?

    Thanks again


    • Pam,

      When you see drones in your own hives, you can assume others are around.

      I don’t remember what the queen caging discussion was regarding. But for short periods of time, a queen cage is usually just fine.

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