bee biology

A wealth of working winter bees can energize your colony

Winter bees in snow-covered hives.

A winter bee is wonky because it’s entirely different from a regular worker. In fact, winter bees are so different that some entomologists consider them a separate caste.

As beekeepers, we tend to underestimate the importance of winter bees. We are especially unconcerned late in August, just when the colony is on the brink of producing these winter wonders. On a sultry August afternoon when the cat is long and the air is too hot to move, the next brew may seem more important than the next bee. But that next bee may be the one to shepherd your colony into spring, long after the brew is forgotten.

So what about winter bees makes them so important? And what makes them different from any other bee? According to Remolina and Hughes, winter bees are workers that emerge near the end of the foraging season [1]. Rather than living six weeks like most of their summertime sisters, winter workers may live six months, or even longer. These are the bees that determine whether our colony will survive the winter. And because of that, we beekeepers need to pay them more attention [2].

What makes a winter bee special?

The main difference between a winter bee and any other bee is the presence of enlarged fat bodies in the abdomen. According to Rosanna Mattingly in Honey-Maker, “the fat body puts together, stores, and breaks down not only fats but also proteins, carbohydrates, and other molecules.” [3] Fat bodies also produce vitellogenin, an amazing substance that allows a nurse bee to secrete brood food even in the absence of fresh pollen. Vitellogenin also enhances the immune system and increases lifespan.

Winter bees spend their lives within the nest where they care for the queen, help the colony with temperature regulation, and raise the brood that will inherit the colony in spring. Biologists believe that winter workers evolved as honey bees migrated into colder climates. In areas where cool temperatures prevented the year-round collection of pollen, honey bee colonies needed a system that could see them through the shortage.

Winter bees can be considered a caste

Just as any fertilized egg can become a queen, so can any fertilized egg become a winter bee. Their genetics are identical. In fact, some authors refer to winter bees as a separate caste. A caste in the traditional sense is defined as “a physically distinct individual or group of individuals specialized to perform certain functions in the colony.” The winter worker caste is physically distinct because of the enlarged fat bodies, and those fat bodies have a special function. They produce large amounts of vitellogenin which can supplement or replace a winter pollen supply.

Winter workers are produced when pollen becomes scarce. Just as a queen can be raised by feeding a larva a special diet, a winter worker can be raised by feeding a larva a special diet. But the diet that triggers a winter bee is not extra rich like a queen diet, instead, it is extra lean. Larvae fed a diet deficient in protein can trigger the development of winter bee traits [4].

Because winter bees are produced when pollen is lacking, winter bee production is dependent on local conditions. If you live in an area with plenty of summer rainfall, your winter workers will develop later than someone who has a significant summer dry spell. The important point is that pollen, not temperature, regulates winter bee development [5].

Without pollen, a colony is nothing

As any good beekeeper knows, pollen is the currency of a beehive. While nectar provides energy, pollen provides everything else. You cannot raise bees or children on sugar alone; you also need protein, fat, lipids, vitamins, minerals, antioxidants, and trace elements. Pollen contains all of these and more.

Without a diverse source of high-quality pollen, a colony will collapse. Such a colony cannot produce healthy offspring and cannot perform the many functions necessary for day-to-day life, let alone prepare for lean times.

However, everyday life in a bee colony is fraught with lean times. Pollen can become scarce during protracted wet weather, dry spells, and certainly over winter. Yet a colony does not store pollen on the same scale as it stores nectar. Most pollen storage is used almost as quickly as it is collected, so how does a winter colony survive?

Enter the winter bee

The answer lies within the winter worker. Although we think of pollen storage as occurring in the combs surrounding the brood nest, winter storage of protein actually occurs inside the winter bee. The enlarged fat bodies, along with enlarged hypopharyngeal glands, provide a vast storehouse for vitellogenin and other materials needed to produce brood food.

This hidden treasure is the reason a healthy colony can produce a batch of spring bees long after the last pollen flow has ceased and long before the new one begins.

Even winter bees have their limits

But just as a pollen cell is limited in size, so is a winter bee. As winter bees begin to feed brood, their fat bodies shrink and the glands produce less. Eventually, they can run dry. In many situations, they have enough to get them into spring. But if conditions are bad, if a dry spring follows a harsh winter, the protein may eventually run out.

The possibility of running out has a lot to do with the strength of the colony going into winter, the amount and quality of stored food, the mite load, and the winter weather. For those reasons, many beekeepers find that a supplemental pollen source can make a world of difference in the strength of overwintered colonies.

In an interesting twist, Mattila and Otis found that feeding supplementary pollen to colonies in late summer or early fall did not boost the number of winter bees but merely increased the length of the normal brood rearing season [6]. This makes sense if you consider that the lack of high-quality brood food is what stimulates the production of winter workers. As long as good brood food remains available, normal “summer” bees will be produced.

Their findings suggest that supplemental feeding may be more beneficial after the winter bees have emerged. Many beekeepers follow this pattern, waiting until mid-winter before giving supplements. But even giving supplements early can have benefits because increasing the brood rearing season decreases the length of time winter bees need to survive.

Let’s not forget about Varroa mites

While we’re thinking of winter bees, remember that a weak or virus-infected winter bee will be useless to the colony. I cannot stress enough how important it is to have mites well under control before the winter bees emerge. If a winter worker starts life with a viral infection, that bee’s vitellogenin resources will be lost to the colony. In most of temperate North America that means mites need to be treated before the end of August.

Honey Bee Suite

[1] Remolina SC and KA Hughes. 2008. Evolution and mechanisms of long life and high fertility in queen honey bees. doi: 10.1007/s11357-008-9061-4.

[2] Some authors refer to winter bees as “diutinus,” which is a pretentious word for “long-lived.” Use diutinus if you want to be pompous, but use “winter bees” if you want to be understood.

[3] Mattingly RL 2012. Honey-Maker: How the Honey Bee Worker Does What She Does. Beargrass Press.

[4] Mattila HR and GW Otis. 2007. Dwindling pollen resources trigger the transition to broodless populations of long-lived honeybees each autumn. Ecological Entomology. 32:496-505.

[5] Not everyone agrees on what triggers winter bee development. Other theories include the presence or lack of various pheromones in the brood nest.

[6] Mattila HR and GW Otis. 2007. Manipulating pollen supply in honey bee colonies during the fall does not affect the performance of winter bees. Canadian Entomologist. 139:554-563.

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  • I consider this article as a gladly received New Years present to increase my knowledge about winter bees! Thank you, Rusty!!

    • Thanks, Peter. I’ve been reading up on these guys for weeks, trying to learn enough to write a post. I think they are amazing.

  • I deeply appreciate your winter bees post. I will be giving a presentation in a few weeks to a Girl Scout troop about “Honey Bees and their Honey.”

    Your post could not have come at a better time!

    Thanks so much Rusty for sharing your beekeeper passions and wisdom with us all.

    Happy New Year 2017!
    Have a “Beeutiful” Year Ahead.

    Jim Harper
    OFGC, Chief Beekeeper
    IL Master Gardener

  • What a fabulous article, Rusty!

    I’ve given a Fall and Winter Management talk many times and your article has given me some fresh food for thought. For example, I never knew that the scarcity of pollen triggered the production of winter bees.

    Thanks always for your wonderful site!

  • Wow. What a great article. I have ever increasing appreciation for info on bee biology and behavior. It really helps me think through how I might best support the colonies that I am stewarding.

  • Thats a great article..Thanks a lot Rusty for your knowledge sharing…I’ve learned a lot from you

  • “They produce large amounts of vitellogenin which can supplement or replace a winter pollen supply ”
    Can you elaborate on this information .

    • The vitellogenin stored in the fat bodies is a glycolipoprotein, meaning it is made up of sugars, fats, and proteins. It contains all the components the nurse bees need to make royal jelly. When royal jelly is needed and there is no source of pollen or bee bread remaining in the hive, the nurse bees use their stores of vitellogenin to manufacture the royal jelly.

  • Thank you! I shared on Facebook and wrote that every time I read one of your posts, I learn something new, something interesting, something that will help keep my loaner hive healthier. What a wonderful gift!

  • Rusty,
    Wishing a Happy New Year for you and your bees. This is a great blog post. I think it may be one of your best because the subject is so important. Thanks also for the literature citations. It is a difficult decision when to feed pollen substitute and how much. This post will spur me to read more on the subject this winter. It looks like, as in many things in beekeeping that it is a delicate balancing act, a lot of balls in the air.

  • Hi Rusty,

    Thanks for the post, very informative. I treat with oxalic acid usually at the end of winter before brood appears; if I treat at the end of August I still have brood, is it okay to treat then?


    • Tim,

      There is a lot of disagreement on this. Personally, I treat with oxalic in winter and something different in summer because I don’t want to build up resistance. If you treat with oxalic when brood is present you need three treatments across three weeks. When you do multiple treatments, most sources I’ve read say to use vapor because it’s a bit easier on the bees. For a one-time treatment in winter, dribble is fine.

  • Thanks for the article, Rusty. It is very clear. May I forward the link to the members of the Newfoundland and Labrador Beekeeping Association? We have such a long winter and often wet, windy, foggy April May and June, that winter bees is a good concept for us to be aware of. Luckily we don’t have varroa or trachaeal mites, or I don’t know how we would make it!

  • When bee hives are covered with snow as shown in this picture above, does not the entrance need to be cleared in order to facilitate air circulation?

  • Rusty,
    There is SO much to know about bees; thanks for chipping away at my lack of knowledge. I enjoyed your article about the thermal camera to the point where I bought one (Flir One). The Flir rep assured me it would work with my Ipad. Unfortunately, it works with SOME Ipads, but not mine (too old). Some day some one will make a ther. camera cheaply that operates independently. In the meantime, I’m off to buy a stethoscope.
    Jack Wheatley

  • I love your comment/articles on bees u do a wonderful job I have learned a lot from u thanks for what u do.

  • I love learning new things and I definitely learned something new with this article. I consider your page one of my “go to” sources. Your article did lead to other questions for me though. I was in my hive last week and I was very surprised by the large size of the colony and the amount of capped brood. I expected to see a “winter” colony that was lower in population and broodless. I wanted to do an OA vapor treatment when there wasn’t any brood but that obviously didn’t happen. I posted about it on my local beekeeper association Facebook page and one of the member comments suggested that since we are past the winter solstice the hive population will only increase from here on and that I probably wouldn’t be able to do a treatment on a broodless hive. After reading this article I’m not so sure that is true. It sounds like the queen laying has more to do with resource availability and winter bees and less to do with the length of the day. As a side note I live in the Sacramento valley in Northern California and we have been having a couple of days of rain followed by several days of “warm” daytime temps and I have observed my bees going out and running loaded with pollen. Now that we are getting more prolonged bad weather maybe my give will begin to produce winter bees.

    • Paul,

      I agree with the winter solstice comment. Egg production slowly increases after the winter solstice. Winter bees are produced in the fall as resources are becoming more scarce, but once the days start getting longer, the queen increases egg production and the winter bees will use the resources stored in their fat bodies to feed the brood, unless of course you have pollen coming in. With all that pollen, your bees should do fine. You won’t be able to do a broodless OA treatment, but you can do a treatment with little brood, which is almost as good. Many places don’t have completely broodless periods. I very seldom have zero brood, even in the dead of winter and you are further south than I am. Just do the OA soon before you get more brood for the mites to hide in.

  • Great article, thank you – always a pleasure to read you and compare experience. Thanks from a happy beekeeper in Paris.

    • Hi. Did you get my emails? About five minutes after I talked to you, I got an email saying WordPress had been updated to 4.7.1. As soon as the update occurred, the comments count showed up and so did the categories. I can’t believe I spent 6 weeks battling something I was never going to be able to fix.

  • How can I attach a picture I took of what I believe is a winter bee outside her hive during a brief warm January day.

  • Brilliant post. May have spotted a typo in the August afternoon sentence – ‘when the cat is long’? Maybe cat should be day? Not sure I like your new anti-spam comments system by the way, bit of a palaver when using a phone.

    • Emily,

      “When the cat is long” refers to hot afternoons when cats stretch out to twice their normal length in order to keep cool. At least mine does. Maybe I should not generalize about cat behavior?

      About the captcha code: I am working with a web designer to make improvements, and comment spam is one of those things I have to deal with. But nothing is set in stone at the moment. I’ve given the developer license for “try-its” and I’m keeping an open mind. At any rate, thank you for your opinion. I listen to every one.


      • Ah I see! It is perhaps a US phrase and that’s why I haven’t heard it before. It probably doesn’t get so hot here that the cats need to do that…mine seems to spend most of his time curled up as tight as possible.

        I found the pictures a little hard to see on my phone, so selecting which were mountains (for example) was a bit of a pain. Also the verification expired so I had to go through the process again with multiple sets of pictures. I know reading websites on phones isn’t ideal but it’s useful when you have a feeding baby 🙂 Good to try and cut down on the spam you get though.

        • Emily, what on earth are you talking about? Mountians? Pictures? This is freaking me out. There should be a square box and the words “I am not a robot.” You check the box, assuming you are not a robot. This made be laugh until I realized you are serious. Oh no!

  • Hi Rusty,

    I live in western WA near Olympia. I am a first-time beekeeper as I set up my hive last April. It has been very cold here the last couple of weeks. Today it warmed up to around 45 degrees and I decided to quickly check to see if my bees needed more of the candy board/pollen supplement I gave them this past November when I installed the quilt that you have blogged about.

    Long story short, I believe my hive is dead. There were a lot of dead bees on the candy board and when I removed it there were many dead bees on top of the brood box. I had it open for about two minutes and I didn’t see any live bee or hear anything from within. I was a little shocked because I saw plenty of bee poop in the snow the last couple of days.

    I feel pretty horrible. I Hopguarded in May and August. I fed them 2:1 in September and made the quilt with the candy board. In early December I saw them buzzing in and out.

    Is there any way I can determine what I did wrong? Honestly I am kind of in shock and surprised at how bad I feel. I want to try again this spring but I don’t want to make the same mistake.

    • J,

      It is certainly heartbreaking to lose a colony of bees, especially if it’s your only one. However, you make the assumption that you did something wrong, and I’m not sure you can conclude that. Of course, since I can’t see or examine the hive, I’m guessing here. But in many ways it sounds like a queen failure. If you lose your queen in the fall or winter, your colony cannot raise a new one, so it eventually dwindles and dies. Queen failure is not at all uncommon nowadays, and queen genetics and longevity are things that breeders are concerned with. There are probably many reasons for weak queens including diseases, pesticides, nutritional deficits, and a sub-optimal gene pool.

      Try again next year and consider getting second hive. It’s easier to keep bees doing if you have more than one to work with.

  • Rusty, a little off topic, but I have a beekeeper friend with several hives. In the fall, the bees are vacuumed up and the honey is taken leaving empty boxes only to be filled with newly purchased bees in the spring. I am a single hive, 2nd year beekeeper hoping my girls make the winter here on the Minnesota/Canadian border. (So far so good!). I would like to know a way to try to salvage a colony or two and winter them over even though all the fruits of their labor have been removed. I look forward to your every article and your wealth of knowledge has helped me so much over the last 2 years. Thank you for all you do. Rylan

    • Rylan,

      I’ve never tried to keep a colony all winter on nothing but sugar and pollen substitute, but I’ve come close. For example, I’ve had a few very late swarms which I managed to overwinter with artificial feeding alone. If you are going to try this, I would transfer a few frames of honey from your good hives into the salvaged hive and then feed all winter. Giving them at least some honey and natural pollen will add more amino acids, protein, and vitamins than sugar and pollen substitute alone. You might also try adding something to their sugar patties like Amino-B Booster or Hive Alive to give them some of the micro nutrients they will need. I think you could do it, but you would have to stay on top of it to make sure they don’t starve.

  • I saw your post to the beekeeper that did everything right and no bees jan 17. I have 3 hives, one older larger one is out flying like crazy today, 55 outside in willamette valley. My other two smaller and newer hives 1 deep each appear to be dead. They have plenty of food, and are in a tight cluster next to food. I treated for mites twice last year spring and fall. I put moisture quilts on all the hives above the frames, inner cover on top of quilt box. They all have screened bottoms on a solid board and a slatted rack. The entrance is reduced and I put a board to close up the rear below the screened bottom. I lost all but this big old hive last winter also. I am getting discouraged here. I closed them up again and even tho I am pretty sure they are gone, maybe they are just too cold to move? (not likely). Will do an inspection another time just in case I missed live ones.

    • Hey Bonnie,

      When you do your inspection, take detailed notes on what you find. Note if you find the dead queens, how much food was remaining, evidence of parasites, guanine deposits, brood diseases, deformed wings, or any odd thing. It sometimes helps to look carefully, although not always. I agree, it’s discouraging.

  • Rusty,

    Thank you for the follow-up from my post on 17 Jan. Based on that and your message to Bonnie today, can you suggest a resource or perhaps another blog on how to conduct the postmortem of the hive? I took a few pictures on the 17th when I opened it up but I wasn’t looking for anything particular. To that end, is there any “evidence” that should be collected and preserved/recorded with an inspection of the hive now versus waiting until it warms up for good? At this time I can only say with some degree of confidence that the colony did not starve because there was plenty of candy left on the board. Appreciate your thoughts.


  • Hi Rusty,

    I love reading your blogs, especially because I like learning from another woman beekeeper. You write well which makes the information fun to read. I’ve enjoyed many good chuckles as you post. Really loved the one about grammar and bees/bee’s a while back! I’m a second year beekeeper with two hives. I lost one hive this fall to yellow jackets; the other is hanging in there. I’ll continue to read and learn. Thanks for your posts.
    BTW, my cat gets long in summer, too!

  • Thank you so much for this!

    I am in my first season of beekeeping — and am realizing that I haven’t treated for mites! While I have been checking my bees, I haven’t seen any mites — maybe I haven’t recognized them yet??

    Is it too late for me to treat for mites, just to be safe? Temps are just now below 65, but will come up again to 70 in a week… Should I treat while the temps are low or wait??

    I really don’t want to lose my bees!

    Thank you!!

    • Erika,

      1. To know if your bees have mites, you need to test for them. Sugar roll test

      2. Treatments have different temperature parameters. If you need to treat, you need to pick a method that will work with your temperatures.

      3. If you have an infestation, waiting is a bad idea. Your winter bees are emerging now.

  • Rusty,
    I’m somewhat new (4th year and still a lot to learn). I’m interested in the area you’re in.

    I’m in western North Carolina near Ashville. We see pollen coming in until late fall from goldenrod. Looking in my hive the queen is busy laying. I’m told by more experienced beekeepers that the current eggs will be the winter bees. If you;re correct about the pollen deprived bees, I will not be getting winter bees until late October or November. Our winters are mild compared to some.

    Thanks for the information.

  • What ate the chemical constituents of the smoke sprays that calms bees when their combs are being removed?
    Also why is it so widely assumed that none of all the native weeds frantically pulled up, contain n chemical constituents in their pollen bees can ingest to protect the hive from mite infestations? Allowing native weeds to border garden sites as Hedgerows will likely also prove prove beneficial.

  • Winter bee transition is triggered by the lack of brood pheromone in the colony and reduction in forage coming in.

  • Very interesting and helpful information. And, as always with your articles, succinctly well written.

    Your knowledge database is the best on the internet!

  • Since I have had nothing but bad luck carrying bees through the winter for way too long, I made sure I did everything by the book this year. No exceptions. Around October I checked all of the hives and there were piles of dead bees, way more than I was good with. The hives were still alive tho (I could hear them in there). I put a patty on each hive just to make sure they had enough to eat and check that regularly. The winter has not been a “traditional” winter in Michigan, even tho it is mid-December, temperatures are rising to the mid-50s this week. Checked the bees yesterday, and can’t decide what is really going on in two of the hives and don’t want to open them. The third hive is definitely alive, but again a pile of dead bees. When I cleaned this up I noticed what looked like chewed brood scattered in the bodies. This is a first for me. One thing is for sure: I never thought an insect could make me feel so stupid.

    • Sharon,

      We all view things differently. In winter, when I see a pile of dead bees and chewed brood, I’m totally relieved. If a colony is removing it’s dead and discarding compromised brood, it’s a sign the colony is strong enough to do what it should be doing. Dead bees happen every day, and if the colony is not strong enough to remove the dead, it’s a very bad sign. I can’t remember what the proportion of “birth defects” is in a healthy hive, but I think it’s around 8 percent. These discarded bees may have defects, may be diseased, may have been invaded by mites, or may have just died the way young animals do. To keep the rest of the colony healthy, the rejects must be removed before they become breeding grounds for bacteria.

  • Wait–so protein deficient brood food triggers winter bee development? This is a revelation for me!

    So what would happen if you fed pollen patties 365 days a year? Would they never raise winter bees? I need to get a microscope and learn to ID winter bees so I can test this out.

    Rusty, on the subject of winter bees, I found a guy who overwinters his bees in the Yukon. He is an engineer and has compiled a huge amount of data on colony dynamics during winter. Thought you might be interested–his YouTube channel is Etienne Tardif.

    • Sean,

      Yes, at least that’s the theory. If I understand correctly, honey bees in warm climates don’t need winter bees because they have year-round pollen. And indeed, they don’t have them. Cool right? I’ve read that winter bees were an adaptation that occurred as honey bees migrated into colder climates.

  • Yes it’s an old post I’ve read before but tag you’re it with a question. While I expect the answer is going to be “it depends”, how long into spring given a relatively normal weather pattern would winter bees continue to live in Western Washington? And would they ever actually decide to leave the hive on foraging or cleansing flights in the spring? One of our colonies has exploded in population well beyond anything I find in other 5. Granted this is the same colony that swarmed twice last summer and best guess was with TWO queens [one we assume was virgin?] given they formed into two different swarms and both survived without merging or re-queening either.

    • Gary,

      As far as I know, winter bees make it just long enough to assure the late winter bees are fed and growing. I don’t see them living much longer than that, and I don’t imagine they forage. They have one job to do and then they pass the colony to the new generation.