Prime numbers and cast offs

This post was prompted by a recent search used to reach this website. The question posed was can a prime swarm be led by virgin queen if [the] old clipped queen dies trying to lead a swarm?”

Swarming is the natural way that honey bee colonies reproduce. The process is triggered by a number of factors – overcrowding and diminishing levels of queen pheromone being two of the most important.

A small swarm

A small swarm …

Both these are, directly or indirectly, measures of how strong the colony is. If the queen has nowhere to lay because the box is wall-to-wall brood or stuffed with nectar, the colony is effectively overcrowded. In contrast, if the colony has ample space but there are so many bees that the queen pheromone is ‘diluted’, the colony will sense this indirect measure of strength and make swarm preparations.

In addition, as queens age they naturally produce less queen pheromone; colonies headed by older queens are therefore more likely to swarm than those headed by first year queens.

Prime swarms

You’ll see two definitions of prime swarms. Some define it as the swarm headed by the mated, laying queen and others use it to mean the first swarm to issue from a hive.

They’re usually one and the same thing.

Developing queen cells in the hive are capped on the 9th day after the egg they contained was laid. If the weather conditions are suitable – typically early afternoon on a warm, sunny day – the mated queen leaves the hive with up to half the workers.

This swarm – headed by the mated queen and often containing perhaps 20 – 30,000 bees – is the prime swarm. It’s the first to leave the hive … but it might not be the last …

Captured swarm in 8 frame poly nuc

Captured swarm in 8 frame poly nuc …

Casts (or cast swarms)

Seven days after the queen cells were sealed the new, virgin queen emerges (or ecloses). For the continued viability of the original colony this queen needs to be mated and return to the colony. She does this on a warm, sunny day a few days after eclosion.

However, there are often several developing queen cells remaining in a hive after a prime swarm disappears over the fence to the howling wilderness.

This is where things get interesting.

All sorts of things can happen at this point. If the colony is strong enough it will throw off one or more casts. These are small swarms, headed by a virgin queen. Small is a relative term. They’re small in comparison to a prime swarm. Once started a colony can continue to throw off smaller and smaller casts. Some are these small in comparison to a mug of tea.

The continued loss of bees means the colony may effectively ‘swarm-out’, reducing in strength until perhaps only 10% of the original colony remains. If this happens any opportunity of a honey harvest is also lost and there’s a chance the colony will not recover sufficiently in time to overwinter successfully.

To complicate matters further, if multiple queens emerge casts can contain more than one queen. Sometimes you’ll open a hive at the same time as multiple queens are emerging. It can be bedlam trying to catch half-a-dozen virgins scuttling around a busy brood box.

Hiving casts

Large casts – perhaps football-sized – are worth catching and dumping into a nuc. Once the queen gets mated they can develop into a worthwhile colony. Ted Hooper describes ‘rescuing’ smaller casts by uniting them over a queen excluder on top of the supers on a strong hive. The bees unite and the queen is prevented from entering the hive by the excluder. I’ve not had to do this. I’ve lost one or two colonies that swarmed out but missed the ever-diminishing casts altogether.

A cast ...

A cast …

The cast swarm above was collected in a skep and allowed to settle for a few hours. When I lifted the skep from the sheet to dump the bees into a nuc there was a single bee corpse remaining … a dead queen. The cast obviously contained at least two queens. On checking the nuc a week later, after a week of almost continuous rain, I found a single skittish queen running around. Her behaviour suggested she hadn’t yet had an opportunity to get out and mate.

A cast in the skep ...

A cast in the skep …

And the answer is … ?

Consider again the original question … can a prime swarm be led by virgin queen if [the] old clipped queen dies trying to lead a swarm?”. The answer isn’t necessarily straightforward.

I think I’d argue that a swarm led by a virgin queen, despite being the first swarm to leave the hive, is not a prime swarm. It’s viability still depends absolutely on the virgin getting mated.

I would consider it as a cast.

Clipped queen ...

Clipped queen …

Clipped queens have one wing trimmed to restrict their flight. This is a well-established method of swarm control. If the colony swarms the queen drops to the ground and the swarm often clusters with her under the hive. Colonies with clipped queens usually swarm a bit later in the development cycle of the new queen(s) in the colony. However, they are only delayed by a day or two.

I’m therefore puzzled why – as suggested in the question – there was both a clipped queen and an emerged virgin in the colony simultaneously. Or perhaps there wasn’t, but the query was whether a subsequent emerging virgin would head the swarm …

I’m afraid the puzzle will remain. The question came from an internet search … unless the person who posed it reads this and responds all we can do is speculate.

Or perhaps to establish themselves in your neighbours soffits. The same neighbour who has always complained about your bees chasing their dog and stinging their children. Reason enough to try and not lose swarms.

‡ I know this was a cast headed by a virgin queen because it came from a vertical split in which the queenless half was left overly strong. The clipped and mated queen was ‘all present and correct’ in the queenright half of the split – I checked. I’m intending to write a bit more about how to prevent casts in the future … once I’m a little better at it than I’ve been this Spring  😥

18 thoughts on “Prime numbers and cast offs

  1. WesternWilson

    Nice post David! I have always made swarm prevention splits by taking out the old queen with a goodly court, and letting the original (thence queenless) colony raise up the new queen. The original colony has more bees and stores, and does a great job of queenrearing. However, it is critical to go back into the original hive a week or so after the dequeening to cull or pull out queen cells. There are often 10 or more, and if you leave them all you will get multiple swarms, which defeats the whole purpose of the exercise! Which was demonstrated this spring by a friend who forgot to cull back to the three best cells and had a swarm-a-palooza.

    And thankyou for my new word of the day, eclosion!

    1. David Post author

      I’ve got a half-written post about this. Some people state that queens reared under emergency conditions will not throw off casts. My experience is that this can happen. You then get the question about how many to leave, open or closed, and whether we (as beekeepers) are better at choosing potential queens – which is all they are at this stage – than the colony?

  2. Emily

    What influences whether colonies continue to throw cast swarms, do you know? Is it genetic? It seems like a bad strategy for survival.

    An unrelated question – can unmated virgins ever look as large as a mated queen? We still have no eggs in one of our hives a few weeks after a large new queen was spotted. Could be she’s died I guess.

    1. David Post author

      Hi Emily
      Everything is genetic 😉 Well, more or less.
      I think strength of the colony is a major factor. Really strong colonies seem – in my experience – to be more prone to chucking out loads of casts. Most swarms do not survive. An even greater proportion of casts perish (there’s data on all this). However, it only needs to be successful once for it to be beneficial – in terms of reproduction – so there’s likely to be some genetic selection for the trait (or at least ensuring the trait is not completely lost). Of course, all this is confounded by the influence of loads of additional things like available forage, weather etc. Would a bulgingly strong colony chuck loads of casts off if there was a dearth or poor weather? I don’t know.

      Queens … definitely yes to your question. I’ve seen some teeny tiny mated and very successful queens and some great big bloated virgins. I opened a nuc up last week that has a reassuringly big (because that’s what beekeepers look for, whether it’s a true indication of quality or not) virgin scampering about. I expect (hope!) to find her today, mated and laying. I think behaviour is a much better indication of whether she’s mated than size.

      If it’s a ‘few weeks’ and the weather has been conducive for queen mating I’d be starting to get concerned – perhaps try a test frame? Don’t leave them too long or you might end up with laying workers.

      I hope she reappears!

      1. Emily

        Very useful to know, especially that virgins can look big. I wonder what they are bloated with and why only some appear that way. After going through most of the hive on Saturday and spotting no eggs/brood we were almost convinced they were queenless – only to find a queen with an egg coming out of her bum!

        1. David Post author

          Ha! Anatomically inaccurate but good news nevertheless 😉 I have a couple of hives in the same sort of limbo – there should be a laying queen in there, but I’m darned if I can find her.

          ‘Bloated’ was just a term to indicate size … I suspect they’re just genetically large and/or well fed during development.

          Enjoy the good weather

  3. Lauren

    Such an interesting question and I agree with you that the answer isn’t exactly straightforward. You’ve done a lovely job of covering all of this (and some great pictures too) 🙂

  4. Edward

    So I had a clipped and marked queen she left with the prime swarm, because she could not accompany them, they returned to the hive. (I am assuming this as I was not there) dam that would explain the small knot of bees on the ground I did look at them but did not see any queen Ok I missed that not paying attention. Any way another swarm issued from the hive, could this be a cast swarm if it was it had a huge number of bees and is now in the roof and not my bait hive. My question is. is this cast swarm headed by a virgin queen or could she be mated. Why did they leave at 8pm in the evening? good post interesting reading.

    1. David Post author

      Why did they leave at 8pm? Who knows? Sometimes they do the weirdest things. I suspect they were simply hell-bent on leaving and it was a hot day.
      Was the second swarm a cast headed by a virgin? Assuming it was soon after the first attempted to leave I expect the queen was unmated. If the first tried to leave when the cells were capped you’d still need 7 days for the new queen to emerge and then a few more for her to mature and get out and mate. Clipped queens tend to swarm a bit later. However, if it was a week or less I’d be reasonably certain the swarm in your roof left headed by a virgin.
      Good luck in tempting them out of the roof 😉

  5. Edward

    Thanks for that. If she leaves the roof to get mated when she returns she may just stay put on a frame of old foundation I placed in a Nuc roof upside down over the entrance which I reduced to limit their access, I did this at ten pm so she is probably in there, hope I am not too late. its all an adventure.

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  7. Dorothie

    Hi David
    I arrived on this page from your latest posting.
    I managed to mark and clip my first queen recently (unnecessarily proud of myself!!) My question is about how much you need to take off? As I was a little shaky and didn’t want to take off too much ( or snip anything else!!) I only snipped off a couple of mm. Most books say 25%-30%
    Will this be enough to restrict her flying?
    I have very close neighbours so it’s important to try and avoid swarming in the case of me missing something (as happened last year!)
    I can catch her again and take off some more but don’t want to stress her out more than necessary!!
    Thank you

    1. David Post author

      Hi Dorothie
      I’d cut a bit more off … I usually clip 25-50% off. Her flight will be impeded, but it’ll be good to be certain.
      Remember that clipping doesn’t stop swarming … it stops you losing the swarm (or your neighbour gaining it). Not the same thing at all 😉

  8. Dorothie

    Thanks David. I’ll give it another go!
    I’m keeping a close eye this year….but just in case!
    Love all your posts. so informative


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