bee biology

What is open-brood pheromone?

Open-brood pheromone is just like it sounds, a pheromone given off by uncapped brood. Actually, at least two types of  pheromone are released by open brood and together they allow the brood to regulate and control the actions of the nurse bees. Sounds backwards, but it’s true: the brood controls the workers.

For example, brood ester pheromone (BEP) increases protein production in workers, inhibits worker ovaries, and regulates the capping of brood cells. Another brood pheromone called E-β-ocimene, regulates the activities of workers, managing the nurse-to-forager ratio. According to a recent paper by Maisonnasse, Alban et al., “The production of two different types of pheromones by the larvae, gives a powerful signal to adjust all workers for colony tasks, especially larval care.”

In comparison, BEP is produced by larvae that are four to five days old and is disseminated by larva-to-bee and bee-to-bee contact. E-β-Ocimene is produced by larvae that are newly hatched to about three days old and is volatile, disseminated quickly throughout the nest atmosphere.

From a practical standpoint, open brood can be used to suppress worker ovaries in a colony that has become queenless. After a colony loses the queen, the amount of open brood soon decreases and then disappears. Without open-brood pheromone to suppress the worker ovaries, some of the workers will begin to lay unfertilized eggs which will mature into drones.

The addition of a frame of open brood every week can effectively suppress the worker ovaries until a new queen can be introduced. Some beekeepers have even been able to reverse a laying worker colony by adding open brood for several weeks. Eventually, after the worker ovaries are suppressed, the colony can raise a new queen from the introduced larvae.

Chemical communication in a beehive is complex and surprising, but learning to use the information can be a real trip.



Multiple eggs per cell is evidence of laying workers. Photo by Michael Palmer/

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  • I appreciate your explanations so much. I wish I’d read this post before I asked you about working layers and how they occur.

  • “Looks like Orc mischief to me!” … that is to say looks like fuzzy math to me (which is probably appropriate in the case of bees). I guess I just failed to follow the reasoning behind it. The queen stops laying eggs, that in turn gradually decreases the amount of open brood, which in turn produces laying workers , which in turn start laying unfertilized eggs, which in turn produce open brood (even if it is just drone brood). See where I’m going with it. The process should be self terminating or at best periodical if the effect of open brood are as they are described. I’m not trying to argue, I’m just trying to understand.

    • Art,

      This is a good question. I’ve re-read the article and I don’t see a clear answer in there. But this is what I think, for what it’s worth. By the time you get laying workers, all the worker brood has hatched because it usually takes at least three weeks, often longer, before laying workers develop. So now you have laying workers, old workers, and drone brood in the hive. I don’t know if drone brood produces the pheromones, but even it does, it won’t be effective.

      Remember, the volatile pheromone E-β-Ocimene has a large effect on the nurse/forager ratio. Since drones neither nurse nor forage, it won’t affect them. The other pheromone, BEP, is instrumental in suppressing worker ovaries but it is disseminated by contact. Since drones don’t feed nurses, they don’t have contact with the larvae, so they can’t disseminate the pheromone. The worker “queens” are busy laying eggs, so they won’t be feeding larva either, and hence they can’t disseminate the pheromone. The only bees left to disseminate the pheromone are the few old nurse bees that still remain, and these are dying off. So I don’t believe the level of pheromone circulating in the hive would be high enough to suppress the existing laying workers.

      Anyway, if I can’t find any other information, I will contact the author and ask.

    • Art,

      Another thought. Let’s say enough open-brood pheromone was produced by the drones to suppress the laying workers. Then what? Since the colony can’t raise a real queen, it will die in any case. So, yes, the process is self-terminating whether drone brood produces the pheromone or not.

  • Rusty: I really enjoy this site. The first thing I do every morning is make a cup of coffee and turn on the pc to see what you have posted. Been doing this for 18 months and never deleted anything. Keep up the good work and thanks. Phil

  • Naturally the end result of a colony with a laying worker is dwindling of the colony to nothing. But that’s not what I was referring to when I was talking about self terminating process. If you look at the process step by step you get:

    1. Queen dies
    2. Three weeks later a laying worker develops.
    3 Let’s say, it takes another week for the laying worker to lay enough eggs to have sufficient quantity of brood to have some significant pheromone effect (if there is any to be had with drone brood).

    Assuming that it was a pretty strong colony to begin with, four weeks later there is still plenty of the nurse bees to distribute the pheromone. Now, if you can reverse the laying worker by introducing at this point open brood frames into the colony, the already existing open brood in the colony should have the same effect (or at least the same chances) to reverse the laying worker (unless the drone brood doesn’t produce the pheromone).

    • Art,

      One of the problems is that you usually don’t have one laying worker, but a hundred or perhaps two hundred. Many of the remaining workers are not eligible to be nurses any more. I’m not saying you are wrong. I think it may all hinge on whether or not drone brood produces the pheromones.

  • I tend to think in the practical terms. So to me this article (aside from learning something new) is interesting also from the point of view of solving a problem of a laying worker. If her own brood can suppress a laying worker I could just introduce a new queen after I see laying worker brood and the problem is solved. The new queen starts laying, the laying worker is suppressed – everybody is happy.

  • Michael Bush recommends:

    “The only other really practical method, in my opinion, is to add a frame of open brood every week until they rear a queen. Usually by the second or third frame of open brood they will start queen cells.”

    That would suggest that worker brood can suppress laying workers.

    • Patrick,

      Yes, without a doubt open worker brood suppresses laying workers. That was what the post was about. The question we are debating is whether open drone brood can suppress laying workers.

  • Hey Rusty, regarding the above picture… I have had newly mated queens laying multiple eggs in cells for about a month. It always seems to correct after a period of time. Some of these new queens go on to become monstrous colonies in the second year. I wonder if these queens have highly developed ovaries…

    • Hi Bill,

      You’re right. I should have mentioned that new queens often go through a phase of laying multiple eggs. It reminds me of new laying hens that often produce double or triple-yolked eggs. Probably too many hormones!

  • Hi Rusty,

    How then does one distinguish between a ‘turbo-charged’ queen laying multiple eggs/cell and laying workers with multiple, disorderly deposited eggs/cell. Is it only when the brood gets capped that one can tell the difference? Are there any clues before that? In other words, did I shake out a hive with a perfectly fine queen yesterday?

    With another failed attempt to make a split and have them raise their own queen, I was also trying to wrap my head around the fact that (even abundant) open drone brood does not seem to suppress the egg laying by workers in that nuc.
    Good discussion. Thanks for the excellent blog!

    • Ellen,

      A new queen will lay multiple eggs only for a few days before she falls into a normal pattern. In any case, a queen lays her eggs in the bottom of the cell in the center. Laying workers have much shorter abdomens than queens, so they can’t reach all the way down. Consequently, their eggs end up on the walls of the cell, or on the bottom near the wall. Also, laying workers will lay in cells containing pollen, and a queen won’t do that.

  • From the bees’ point of view, if the queen is dead and can’t be replaced, at least a number of drones means that, as they wander around other hives, they have a chance of reproducing, so their birth hive has one last chance to spread its genes.

  • Given that a laying worker deposits multiple eggs in each cell, how do those eggs develop into drones? Do nurse bees come along and remove all but one egg in each cell?

    • David,

      Laying workers don’t necessarily lay multiple eggs in each cell, it’s more like all the laying workers (there may be hundreds) are all using the same cells. So five or six laying workers may all lay in one cell. Some may lay more than one in a cell, but it’s more complicated than that.

      The egg that ecloses first will probably win and the others will get eaten by the workers.

  • Since a laying worker deposits multiple eggs in each cell, how do those eggs develop into drones?
    Are nurse bees coming along to remove all but one egg in each cell?

  • I performed a split on my thriving 1 year old hive last week, after it survived winter with ample bees occupying two full deep brood boxes and with plenty of food stores. I just checked the split (I gave it 6 frames, included eggs, larvae, pollen, nectar, honey, and bees on the frames).

    On inspecting the original hive the day we did the split, I noticed in the top chamber on one frame a few eggs that were NOT laid neatly in cell centers, they had only 1 egg per cell, but the eggs were not perfectly neatly laid in the center like eggs I saw on another frame. They were kinda on the side of the cell, and I suspected the possibility of a laying worker in the parent hive.

    Today on checking the split to see if they created a queen cell, there was one, but ONLY one queen cell (capped) it is day 7 since the split. What worries me is that I also noticed on another frame some cells with eggs laid in them, maybe a dozen or two dozen such cells in a section – again, there was only one egg per cell and again, they were against the wall, not neatly in center. I KNOW the queen was NOT in the split because I saw her safely in the lower chamber when we did the split, and put a queen excluder on to keep her there, so it is definitely a laying worker.

    Do I need to introduce open worker brood from the parent hive?

    Will the laying worker(s) kill the queen cell?

    Why is there ONLY one queen cell and is this a big problem?

    Part of me wonders if they are making drones to mate the queen when she emerges (because that would make evolutionary sense to me) but I haven’t read about that anywhere and according to what I’ve read, this is not a good thing. It just seemed logical to me. My husband thinks I should leave it alone.

    So I’m wondering if I need to add open worker brood to stop the laying workers. And perhaps I should add more fresh eggs too?

    I don’t think I should put them back in the main hive because it could fill up fast and then they’ll swarm. The point of the split was to prevent a swarm later in the season as the hive was robust.

    • Eva,

      Even healthy, queenright hives have a few laying workers. It’s usually not a problem, and the eggs are usually consumed by other workers when they find them. The fact that there were not multiple eggs is good news. You say you found these eggs on the day you did the split, so I wouldn’t worry about them.

      When this happens, you can always add open worker brood, but here I don’t think it’s necessary. Having only one queen cell is not a problem aDs long as the queen inside it develops normally and as long as she returns safely from her mating flight.

      Drones do not mate mate with their siblings. Any drones produced by your colony will try to mate with virgins queens from other colonies. Inbreeding causes genetically weak bees. Try not to micromanage and give your bees some time to sort this out.

  • One other thing: the eggs that I put in the split from the parent hive were the perfectly centered, laying down eggs, all oriented in the same exact direction, definitely queen eggs.

    I did NOT give the split the weird eggs that I suspected of possibly being from a laying worker because I knew they’d be only drones if they were worker laid eggs.

    Hoping to hear your thoughts on the situation!

    • Eva,

      One thing I didn’t mention, if a colony has a couple of laying workers, it’s not a big deal. Laying workers colonies do not have one or two, they have dozens and dozens, which is why you would see multiple eggs in a cell.

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