bee biology

Why do brood combs turn black?

Darkened brood comb. PIxabay image by RPN

Brood combs turn dark quickly from accumulations of debris. It is a natural process and should not be alarming.

Brood comb can turn dark in one season

It doesn’t take long to discover that brood combs turn black as night after just one season while honey combs stay light for years. What causes this difference?

Several reasons account for the discrepancy. But in truth, a combination of factors causes brood comb to darken more quickly than honeycomb.

Layers of cocoons remain inside the cells

The cocoons that remain in the cell after the bees emerge are the major problem. The cocoons are extremely sticky and, try as they might, the house bees cannot strip them from the comb.

Entomologists say the darkness is caused by the feces that remains woven into the bottom of the cocoons. Although the bees clean and polish the brood cells before reusing them, much of the fecal material remains trapped within the sticky layers.

Sticky surfaces attract hive debris

In addition to feces, the cocoons attract loose hive debris. Items such as dirt tracked in on bee feet (many bees times six), pollen grains, and atmospheric dust get trapped.

Once the young bees emerge, the workers add a layer of propolis to the insides of these cells. The layer of propolis makes the surface smooth and clean. Also, it contains many antimicrobial agents that make for a healthy colony. But propolis is usually dark red or brown, which accounts for even more color change in the brood area.

So the combination of sticky cocoons, bee feces, debris, pollen, and layers of propolis make the brood combs darker and darker.

Brood combs turn black because of heavy use

But, you say, the inside of honey cells are brushed with propolis too. That is true, but the honey cells do not contain cocoons and they are emptied and polished seldom—usually only once a year. Brood cells, on the other hand, can be polished and reused every 21 or 22 days during the spring and summer—a huge difference.

Another difference between honeycomb and brood comb is the amount of bee activity. Once a honey cell is filled, the bees move on to another. But once an egg is laid in a brood cell, the uncapped larvae are fed a thousand times a day—quite a different traffic pattern.

The buildup of cocoons and propolis in brood cells is significant. Some researchers have analyzed brood comb and found that the cells become measurably smaller as the walls become thicker. If you render your own beeswax, you know how much more debris is filtered from dark brood comb than from melted honeycomb. Clumps of this debris, appropriately called “slumgum,” clog strainers and mesh bags, and tiny bits of it darken the liquid wax.

Is dark brood comb harmful to bees?

The question always arises whether dark comb is harmful to bees. In truth, bees love dark comb and it is often used in bait hives to attract wild swarms. I’ve heard rumors of beekeepers using blackened combs for twenty-five years with no ill effects.

Recently, however, there is concern about pesticide build-up in old combs, as well as the accumulation of some pathogens. Many sources now recommend rotating old black comb out of the hive every four or five years, not because of its color but to protect the hive from accumulations of pesticides and pathogens.

Because the combs get dark so fast, it can be hard to tell old ones from new ones. The simple solution is to write the year on the top bars, and replace the dark ones after four or five years.

Honey Bee Suite

The upper part of the comb has never been used for brood and remains light. The lower portion has contained brood and is starting to darken. Flickr photo by Jordan Schwartz.

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  • Here in the UK government bee inspectors recommend changing brood combs at least every three years and preferably all at once using a procedure such as the shook-swarm or Bailey comb exchange. I’ve heard them say that in the wild brood comb will naturally regularly drop off and then be destroyed by wax moths, so that it wouldn’t be hanging around for decades.

    • That makes sense, Emily. Old comb gets very brittle, so it makes sense it would break off as it aged. So once again, nature takes care of its own. Good insight.

  • My husband retrieved a beehive from his work that needed to be taken down. Its comb is black; I believe the hive is very old. The hive was located in a area where chemicals are processed. But these same chemicals my husband comes home covered in every day. The honey is dark and good; it is like espresso, very bold. Is it harmful or how can one tell? Thanks for your response Amanda

    • Amanda,

      The honey is probably just fine. Very dark or black comb happens naturally when it is reused by the bees year after year. Sometimes comb can turn dark after only one year. Dark honey is the result of the type of flowers that the bees collected from. In most cases, the darker the color, the richer the flavor. You are lucky to have found this.

  • Hi Rusty,

    I just had an online chat with another beekeeper and he was convince that dark comb will darken honey that is stored in it. Now, I haven’t seen this to be true myself. Have you heard of this or know anything about the possibility of honey being color by dark (I presume brood) comb? Now, I know that honey color is dependent on what plant the bees have been working, not the color of the comb, but I am open to learning new stuff.



    • Bill,

      I have never heard of dark comb darkening the honey. For one thing, bees polish the inside of brood cells before they are reused. Apparently they remove any loose debris and then use a thin coating of propolis and/or beeswax to seal in anything that might contaminate future brood, honey, or pollen.

      Neither beeswax nor propolis are water soluble, but honey is. This means that debris that is sealed beneath a layer of wax and or propolis will not get dissolved into the water-based honey. Surely honey in dark comb looks darker while it is still in there, but we’ve all seen water-white honey come out of very nasty-looking comb.

  • we had honeycomb in our home after 3-4 years all bees fly away and there is not any bees left and when i cut honey comb it have dark color but there is no honey in there
    i want to what it causes that bees flees away and there is no honey in there

    • Abdullah,

      From here I can’t say why your colony disappeared. If there was no honey at all left in their hive, that could be the reason. Maybe there weren’t enough flowers for them to survive. Also, they could have been plagued by predators, parasites, diseases, or lack of water. The dark brood combs are caused by layers of cocoons which the hatching bees leave behind. Dark comb is completely normal.

  • I tried something new this year. I had seen this done several times. Mixing a small amount of wintergreen oil and diluting it way down then mixing in the sugar water feed. This is for mites and hive beetles that won’t tolerate the small amounts of wintergreen. However, 4-6 weeks later we received a cold snap unexpectedly and I placed an entrance reducer at the front of my hives. 3 hives absconded within the following week leaving plenty of honey behind. My theory is that I mixed the wintergreen a little to stout and when I sealed off the entrance way the wintergreen smell was overwhelming causing them to leave. I could taste it in some of the honey….. maybe bees absconding with honey in the hive has a lot to do with what they foraged on and if they were able to dry the nectar before cold weather caused the hive to be too cold from moisture or a combination of these things. Learned a valuable lesson from this… very disappointing.

    • Ike,

      This doesn’t sound right. How much wintergreen did you use? I’ve mixed it in sugar syrup to use as an attractant and the bees love it. You would have to use large quantities, I think, to get them to abscond. And three hives absconding all at once is almost unheard of. And why would they wait 4 to 6 weeks before they left? Seriously, I think something else is going on here. Did you do a mite count? The colonies may have collapsed from Varroa mites.

  • Would like to reuse plastic frames with dark comb. I doubt there is concern for much in the way of pesticides or other problems. Can I just scrape off the old comb with hive tool, leaving just a thin layer of wax, much like what new plastic frame comes with. Will bees rebuild on this?

  • Hi Rusty,

    A work colleague and I inherited two hives from a previous work colleague in our gardens at work (we are both gardeners). One of the colonies was very active and upon inspection, the colony was in desperate need of space; they had never, to our knowledge, ever been split.

    The second hive was totally empty (we suspect they swarmed), except for a few dead bees and very packed old brood frames.

    As we were fearful the full hive might swarm, we decided to split the hive.

    We purchased new brood frames for the empty hive and placed these and 3 brood frames from the live frame, together with a queen cell into the empty hive, thereby hoping to prevent the one colony from swarming and creating a second colony. A week later though, the bees we moved, appeared very slow, minimal flying in and out of the hive and quite a few dead bees on the floor. The hive we removed them from is doing well and seems very happy.

    We are both quite upset as, we thought we were doing a good service for our bees’ welfare, but it seems, perhaps we have done the opposite.

    Is this low bee activity/death normal when you try to create a new hive?

    Many thanks.

    • Trevor,

      The first hive probably did not swarm, but probably died or absconded.

      The second hive, the one you split, hasn’t had a chance to produce a mated queen. Assuming the queen cell you added was alive and ready to hatch, it will take anywhere from one to three weeks to get her mated and laying, assuming nothing else goes wrong. In the meantime, the bees in the split will reduce in number until the brood begins to hatch. Even if the queen starts laying at the end of just one week, it will be three more weeks before brood starts to hatch.

  • Hello Rusty,

    I have done a lot of searching on your site and a few others looking for an answer to my question of dark brown wax. Most importantly is this wax is brand new.

    Eleven days ago I collected a very old hive out of a cedar log before it went to the mill. This hive had been in this tree for 20-30 yrs that we know of. I collected what appeared to be the ‘newest’ comb, the stuff that was not brittle. I knew it was a old hive so I paid no mind to the fact it was soooo dark.

    After hiving them and keeping them locked up for 36 hrs, I did a very quick inspect looking for the queen and such. (Was kinda worried as I had to vacuum them out of the log.) I saw no new signs of white comb but really did not think about it much. I checked the hive again this evening, wondering if there was brood and such. Again first thing that struck me was I saw no new white comb. However I was seeing new capped brood all in dark brown.

    That’s when I noticed the comb I had put in there was not shifting around inside the rubber bands. In fact the old wax had been expanded with new comb wax – all with very dark brown wax!!!

    To say the least I was flabbergasted!! I started out of the orchard towards my mom with a whole frame of bees with a queen in the middle. Somewhere sanity struck me and I stopped. But I was able to show her and she also agreed with me that it was new comb and it was the same color as the older wax.

    I can take pics so u can see on Sunday. That’s when I’m going to remove the rubber bands with someone to help me.

    I am a bit confused – this does not fit with everything I’ve learned, seen, read – whatever. So thoughts of disease and such are flying through my head – but they appear for all they have been thru, being cut down, carpenter ants attacking their hive, log being repeatedly moved by the loader, vacuumed out of their hive, and locked up for 36 hrs on 90 degree days – they are really healthy.

    If there is one thing I’ve learned with bees – they are going to do what they want however they want. And I’m wondering if this includes dark brown wax. I would prefer your opinion before asking the pros here in Oregon. Last time they asked me to kill 500 bees and send them so they could test them . And then the second time they told me to kill off what now is my largest hive. I know they know their stuff – I’m just not that harsh.

    Your thoughts, opinions will be greatly appreciated.


    • Monica,

      You answered you own question right here: “They are going to do what they want however they want.” I associate white wax with the first nectar flow of spring. New young bees, a delectable supply of fresh nectar, and white wax magically appears. The other time it happens is when a swarm fills up with honey and travels to a new place with their wax glands primed and ready to go. I seldom see white wax the rest of the year.

      Nothing about your colony suggests you should be seeing white wax. It was not early spring, not the beginning of a nectar flow, not brand new bees, not a swarm. It’s just a lot of average age bees making the best of a bad situation.

      I have seen bees completely dismantle brand new sheets of foundation and use it to build elsewhere. I have seen them move wax from one place to another. I have seen them build in one place, and then tear it up and build elsewhere. They do what they must to get by, even though their wax glands are not primed like they are when they were young and the nectar was flowing. Think recycled building materials . . . we all do it.

      There is nothing in what you say to suggest any sign of disease or other problem.

      • Oh good – that’s a relief. I have been very blessed to have healthy hives and am not directly familiar with bee issues.

        So my bee guy (and a lot of others) when I asked if the hive will reuse wax from one area into another – are just mistaken.

        I have personally seen bees working up wax. I put over some wires that where sticking out from the screen bottom board. There was a little bee feverishly cleaning it off and putting the pieces into her pollen ‘baskets’. When I said something about what I had seen, I was strongly corrected – ‘bees don’t reuse wax’. They must have been collecting pollen…

        So I need to trust my instincts and what my eyes see.

        Thank you so much, It’s nice to be able to send a question to another woman and get a insightful answer back.

        • Monica,

          The myth about bees not re-using wax is really common and widespread. I don’t get it. Many, many beekeepers have seen bees move wax and reuse it. The ones who say that bees won’t do it just aren’t looking. You can learn more about bees by watching them than you can by listening be know-it-all beekeepers.

    • I see this often. It’s not new comb but re-processed bits of old comb. I don’t know how they do it but I know they do.

      Also, I often paint melted wax on my plastic foundation to help them build out quicker. They will re-process it into the right shape etc, I have even seen them strip it all off of one and put iy somewhere else.

      • I have read all your posts and I am learning so much. I have a plastic super and would like to know if I can use wax from another hive to coat the plastic, or does it have to come from the same hive that the plastic is on? Hope that didn’t confuse anyone! Thanks in advance for your help.

  • Greetings,

    Please can anyone help? We had a huge bee hive recovered totally dark brownish black color…… and half of its portion is yellowish…..that dark part also contains honey but huge part got worms (white larva) crawling…
    these are African bees (we are in Africa) please suggest what to do with white larva bee hive can we extract honey from it as it has honey… what to do? Should we discard it? As we are tired of bees at our home lol

    • Madiha,

      The brown color comb is older than the yellow color comb. No problem with that and you can extract it. The white larva are most probably wax moths. You can cut them away and extract the rest of the honey.

  • I recently removed some old frames that were black. Replaced with new foundation simply because the black comb looked occluded in many areas and the cell form did not look 100% anymore. I began to question if the queen would even use it to lay. I would rather risk a restart with new frames and have a ‘clear brood nest’ vs. frames she is not going to use.

    • Christopher,

      You have to evaluate these things through the eyes of a bee, not a human. There is nothing a honey bee likes better than old black brood combs, and they are frequently used to help lure swarms. In fact, I save them for that purpose. You can find many stories of beekeepers reusing combs for 25 years. In modern times, however, with so many introduced pathogens and parasites, most beekeepers like to renew them every four or five years.

  • I have a question and couldn’t find a link on this site, so if you’ve covered this already, please let me know!

    I observed new bees emerging from the brood today, but was dismayed to see many, many dead bees halfway out of the brood, all with their proboscis extended. I also witnessed a nurse bee pull a dead bee out of the brood comb. Is it normal to expect a percentage of the brood to mature to adulthood and die in the comb, or is this an indicator of a greater problem or pest? Thank you!

    • Andrea,

      A certain percentage of bees don’t make it into adulthood, just like any other animal. However, many adult bees partially emerged with their tongues out is often a sign of some of the varroa-transmitted viruses. It’s on my list of things to look for in a mite-infested colony. Is it possible your bees have mites? Have you treated them?

  • I have honey bees under the siding of our house. We had a company come out to give us an estimate for removal. We don’t want them killed and would like the honey/wax. The guy told us if the cone was dark it would be bitter due to dirt ect. Sounded rather fishy to me, especially after I did some research.

    Can you tell me why it turns dark and if the darker cone & honey is better or worse?

    I need to know ASAP because it will determine who we chose to do the removal. Honesty goes a long way in our house.

    Thanks! 🙂

    • Leslie,

      First, dark comb and dark honey are two different things. For example, if you put clear water in a brown beer bottle it looks brown, right? Dark comb is dark because bee brood has been raised in it and the cocoons are left inside. Before the cells are reused, the bees clean and polish the insides. This is totally normal. Most of the honey you buy in the store came from similar dark combs. There is no “dirt” involved.

      The bitterness comment is B.S. The flavor and color of honey is totally dependent on the flowers that secreted the nectar. It is plant specific. For example, very clear honey that nearly looks like water comes from certain plants such as fireweed. Honey that is very dark like molasses comes from plants such as buckwheat. Most are somewhere in between. The flavor, aroma, color, and tendency to crystallize are all plant dependent (not dirt dependent).

      Darker honey has more “stuff” in it. But the stuff is vitamins, minerals, antioxidants, flavonoids, pollen, etc. Not dirt. All honey tastes slightly different, and what we like is personal. Most people prefer light-colored honey, but some people like me, prefer it dark. The darker the better. Dark honey could be compared to dark maple syrup, in that the flavors are often richer and more complex. I save my light-colored honey for bee feed, and keep the dark stuff for the family.

      I hope that answer. Let me know what happens.