postmortems & mysteries

Bees head-down in cells: did they starve?

Many dead bees head-down in their cells.

When you find circles of honey bees head-down in cells, does that mean they starved? Were head-down bees licking the bottom of the cells to get every last morsel of honey?

A reader raised these questions a few weeks ago. Since then, I’ve asked many established beekeepers for their thoughts and observations. To my surprise, I then found a post I wrote back in 2011 that answers my own queries. Forgetfulness is embarrassing, so I wrote this two-part series to refresh my own memory.

My most recent post, “Did your bees die of cold or starvation?” was the preamble to this one. Today I want to review some other details of the winter cluster.

The wizardry of warmth

As I said before, honey bees are wizards at keeping themselves warm. According to Jürgen Tautz in The Buzz About Bees, workers have the ability to “uncouple” their wings from their flight muscles. By rapidly quivering those muscles, the bees produce heat which is used to keep the brood and the clustering adults warm.

Because wing muscles are attached to the thorax, close-up thermal images of nurse bees reveal some with glowing thoraces. These hot bees are known as “heater bees.” Where capped brood is present, a single heater bee presses her thorax down on a wax capping, transferring her heat to the developing pupa, one-on-one.

Large areas of brood are punctuated by a certain number of empty cells, usually about 5-10%. In a clever adaptation, these cells are used by heater bees to warm even more of the surrounding brood. The bees climb into the cells head-first and quiver their muscles.

In the past, the bees in these cells were thought to be cleaning or resting, but with the aid of infrared photography, you can see that the bees are producing large amounts of heat. According to Tautz, other bees, sometimes called “retrievers,” search the hive and bring back honey to feed the exhausted heater bees.

Bees head-down are normal

When temperatures are unusually cold or the cluster is dangerously small, many more bees will go head-down into the brood cells. When brood is not present, the nest is kept at a lower temperature, and the head-down bees don’t work as hard. Additional layers of workers cover the head-down bees and provide insulation to trap the heat.

Head-down bees are not trying to find honey. The tight grouping of head-down bees covered by insulating bees is a heat-conserving and energy-efficient design that is continually fed by the retrievers that bring food (fuel) to the quivering bees. Retrievers are adept at what they do and can collect honey from distant areas when conditions are right. Healthy, well-fed, head-in-the-cell bees are a normal part of a winter cluster.

When things go wrong

But things can go amiss. As I mentioned earlier, you may have illness due to disease or parasites, malnutrition, queen failure, poor genetics, predation, or any number of mishaps. If the colony gets too small to generate enough heat, it will die regardless of food availability. Cold bees enter a state of torpor such that their muscles no longer work. When the bees are that cold, they simply cannot operate.

A beekeeper finding circles of head-down bees may claim his bees died of starvation. While that may or may not be true, it’s virtually impossible to separate the effects of cold and starvation. It’s more of a cold/starvation complex, where each condition exacerbates the other. Were they cold because they couldn’t get food? Or did they starve because they were too cold to move? As one beekeeper explained, the only thing you know for sure is that your bees died while clustered.

Looking for other clues

When you see a pattern of dead head-down bees, especially with food nearby, you know something went wrong in the colony. The head-down bees died while trying to keep themselves warm but were unsuccessful. At this point, it’s the beekeeper’s job to do the postmortem and figure out why the colony wasted away.

Start with DWV

Although certainly not the only cause of colony death, deformed wing virus is a major player and the one I most often suspect. Collapse from deformed wing virus, spread by varroa mites, has such a recognizable pattern that it’s hard to miss.

  • The colony was one of your largest
  • The remaining cluster, if any, is small like a grapefruit
  • You may find a small circle of head-down bees, sometimes covered with a fistful of other bees
  • Only a small amount of brood, often with punctured cappings, remains
  • You find few dead bees anywhere else in the hive
  • Partially-emerged bees, some with tongues protruding, are scattered in the brood area
  • It appears your colony absconded
  • Guanine deposits cling to the ceiling of empty brood cells

The reason matters

Trying to determine the cause of colony death is more than pointing a finger at starvation or cold. Unfortunately, beginners often see the head-down circle of bees and instantly conclude that their bees died in a cold snap, and this relieves them of all responsibility for parasite/pathogen management. But when we fail to pinpoint the real problem, we are bound to repeat the mistake. It’s important to ask yourself why the colony was so small or weak it couldn’t take care of itself.

When you see dead head-down bees in their cells, just remember that live head-down bees are a normal part of a winter cluster. They do not enter cells to lick the bottoms but to maximize their chances of keeping the colony warm. Why they didn’t succeed is for you to figure out.

Honey Bee Suite

A cluster of dead bees head-down in empty brood comb.
These bees died while they clustered and tried to keep warm, but without more information, we don’t know the precipitating cause. Photo courtesy of Jared Watkins.


  • This and the previous entry does nothing more than confirm what happened to my hive – the colony was killed when curious cattle from a known irresponsible rancher tipped the box over during a cold snap. Healthy clusters of bees, some head down (now I know why!), frozen in place. It still hurts, knowing this was my first healthy colony free of yellow jackets, ants, and other myriad causes that killed off its partner colony. It was a swarm from the feral colony in a nearby cottonwood, a multi-year one resistant to all the things beekeepers around here have to deal with. And I’m still feeling the anger. Thank you for your website!

    • Bill,

      I would put a nuc into a single deep brood box. When the colony has expanded to 8 of 10 frames (or about 6 of 8, depending on your equipment style) I would add the second deep brood box. If that fills out pretty well, and you still have a honey flow going on, you will be ready to add your first super.

      • Thank you. Then I think I will let them get established for a period before adding back the upper brood chamber. Yes, I will be feeding also till flow starts.

  • Following my last question. Following installation (depending on answer) should I temporarily keep a single super until population is built up or can I go straight to the two super hive?

  • Thank you Rusty: Here in SE PA our flow starts exactly mid May and runs into July (I have had my colonies on scales for 20 years); I am installing last week of March. Nucs will be new to me this year; you confirmed my thinking.

    Should be plenty of time for expansion before flow begins.

    • Bill,

      You motivated me to look up my old stomping grounds (Benton, PA). It shrunk since I was last there. What do your bees collect?

  • Here in SE PA we have every flowering everything brought to America from around the world over the past generations and are now fully mature. Our primary nectar producers are maples, poplar, and basswoods, in addition to the large variety of wild flowers. A very special tasting honey!!

  • Great article Rusty,

    I have seen the head down cluster of bees many times and have a better understanding now. When I see it again, and I am sure I will, I will use the investigative techniques described here. I now feel better equipped to figure out what perhaps happened.

    Thanks Rusty

  • Someone posted a picture of their dead colony on our club’s FB page…pretty easy to spot dead mites on the dead bees.

  • Hi Rusty, I’ve had the same sadness just last week. We had a rare warm Feb afternoon so I took a quick peek under the covers to check stores and found one colony dead. I found 3 frames identical to your photo, a 5″ circle of head-down bees covered with a layer of, presumably, retrievers, all as dead as a dodo. This colony came to me from a friend last August as I was looking to boost stocks going into winter. She had warned me that they were a bit ‘grumpy’ and may need a new queen this summer. I actually think now that the colony was already queenless when purchased. At that time I had to abandon all inspections because these bees were intent on killing me if I so much as took the cover off! I looked carefully for a dead queen but found none. I also checked for DWV and all seemed well so suspect they were indeed queenless and therefore had no winter bees to get them through the cold days?

    • Ray,

      I had that happen once. The colony was so nasty I couldn’t get near it until it collapsed. It was queenless and had been trying to replace her but failed.

  • Last April I placed 2 nucs in hives, one hive took off and did and is doing well. The other did nothing just stagnated. Checked the queen and looked for eggs and larva, found very little. Kept checking but situation remained the same after 2 wks. I then re-queened. New queen did a little better but not by much. There are no parasites and the other hive is in great shape. Any ideas as to why would be greatly appreciated.

    • Alex,

      By re-queening, you already did the obvious thing. No two colonies ever perform exactly the same, just like two children or two horses. Also, you may be getting drift from one hive into the other. You might try changing the entrance location, or try moving the hives further apart. It may not work, but there might be something in the environment that’s causing them to drift in one direction but not the other.

  • This topic raises so many questions for me: my hives are in the pacific northwest and I’ve been thinking what is causing my string of failures to overwinter hives. I’m 0-3 seasons now and it raises either sadness or anger depending on my mood. What I’m wondering is what is the more likely cause, location or mite management or both? My location is great for summer, at the bottom of the garden under a tree, morning sun and afternoon shade in the summer but maybe the cold damp air pools there in the winter, should I move the hives in October? As for mites I treat in August w/apiguard or MAQS and then oxalic acid dribble in October, but I don’t check (sugar roll) after treating to see if its been effective. All the hives seem to come to the same end, healthy in fall, good amount of stores (one or two supers full), then they seem to dwindle and die by February. Any suggestions would be appreciated.

    • AB,

      In my opinion, mites are important and location is not. My bees are in total shade all year, although about half of them get an hour or so of dappled sun in the early morning. And since they are in the woods, they are also damp all year long. Mold grows on the outside so bad I have to wash them with bleach. But the insides are nice and dry because of moisture quilts and so far, so good with overwintering.

      I don’t know the details, but I’ve heard that Apiguard is virtually useless in a lot of places because resistance has built up. You use more than one product, which is good, but I wouldn’t waste time with Apiguard. I hear variable reports about oxalic, although personally I’ve had good results with the dribble method. MAQS worry me, especially in the fall, because they can cause queen loss.

      A postmortem could tell you a lot more than I can, though. Sift through your hives and look for guanine deposits, if nothing else. That should tell you whether or not the mites got you.

  • Thanks Rusty. I think you just saved me hours of work and a strained back, I was not looking forward to moving hives around, especially if it would be all for naught. I’ll try again this year and wage a merciless battle against mites. I’m thinking I should move up the treatment cycle a bit though, starting mid-July and again mid September, any thoughts? I’ll take a look for the guanine deposits, I think I’ve seen them before but I had assumed it was crystallized honey.

  • It seems I lost both of my healthy colonies in a cold-warm-cold snap. We had a month of sub-freezing temps, followed by a day of 60. At 7 pm it was still in the 50s, by dawn it was 20. Both hives seem to have broken their clusters and then froze spread through out the hive. The bottom board was completely filled with dead bees…it looked like it had been sprayed. Does this seem plausible?

    • David,

      It seems unusual. Normally, the bees would have clustered again as the temperature began drop. It doesn’t take long, so it sounds like they had plenty of time. I wonder how long the dead bees had been accumulating on the bottom board.

    • David,
      In upstate NY this has happened to us in the past under similar circumstances. My guess is that the bees get drowsy and chilled and get caught out of cluster. In our location the sun drops behind a mountain in late afternoon mid-winter causing the solar gain the hives were enjoying to suddenly disappear. So on an unusually warm sunny winter day that plummets below freezing that night, they might not respond quick enough to dropping temps. A postmortem reveals no cluster, just bees scattered about the frames. The bees on the bottom board may have fallen while the others clung to comb or may have accumulated over a longer stretch of time, as Rusty pointed out. If the latter then would they have survived if they had clustered? Hard to say, but if they could have, they should have at least tried to cluster. They keep you guessing.

  • Rusty,

    Just a bit off subject but, the more people I converse with the more I’m convinced how small our world is. Just mentioning it because in your response to Bill you mentioned you resided in Benton at one time. I only live a few miles from there. Definitely a small world.

  • Hi Rusty. Although I haven’t posted, I have been following your site for several months now. I’ve also been emailing other beekeepers links to your postings.

    I just had to write, now that I know where in Pa. you grew up. Benton. I’d never heard of it. I’m originally from Berks County, just a couple of counties south of you. A rural upbringing outside of Gilbertsville, near Boyertown (my high school, class of ’68) helped me develop an intense curiosity and love for animals, nature, and all the environment.

    My beekeeping started when I caught my first swarm, in 1980, while living in the Logan, Utah area after college. My best friend had equipment but no bees. He was off in Alaska fighting fires. I spotted a swarm, hived it up for him ostensibly, but was so bitten by the bug that I decided, “This one’s for me!”

    I kept quite a few hives, up to 30, but got frustrated when living in sw Idaho and having an insurmountable time with AFB spread by an unscrupulous commercial beekeeper who left his infected hives behind when he hauled his healthy hives to California. It was incredibly disgusting, demoralizing, and not something I could combat. Our healthy hives would rob his left-behind, weak, sick ones and then succumb to the foulbrood.

    Two years ago I rekindled my delight in beekeeping by building two top bar hives and getting a package. I read your blog daily and am thrilled with new posts.

    Most fervently I’d like to commend you on your command of the English language. It seems our English teachers in Pennsylvania were “out of this world”. Your writing style is fascinating, your scientific comprehension is encouraging ( I have a biology degree and base nearly all my decisions on environmental considerations), and your patience is rather remarkable.

    A very dear friend of mine, Dr. William Cleveland, DVM, lives immediately outside of Monroe, Washington, so is somewhat close to you. Bill has been keeping honeybees there for quite a number of years and knows a thing or two about these creatures we hold so dear. I’d be glad to facilitate a connection between the two of you if you like.

    Please keep up the wonderful work.

    Roger Watson, Dolores, Colorado

  • Hi Rusty. I lost my bees the end of Sept. I had a bad motorcycle crash in Aug. The first week in Sept I had my neighbor help me remove one full super to harvest. Two other supers were 2/3rds full. Being that I was still recovering it was the end of Sept before I got back down to my hive and found both supers empty and every bee gone. Why would my bees have swarmed in late Sept. with two brood boxes and two supers.

    Vincent. mulac

  • Rusty,

    First of all, thank you so much for your hard work maintaining this blog. I have donated in the past, and I encourage my fellow readers to do the same in 2018!

    I feel the Accidental Beekeeper’s pain, as posted above. I, too lost my hive for the third year in a row. I treated with ApiGuard early and MAQS later, and a sugar roll indicated that the mites were less than 2% going into late fall.

    The colony looked huge, and during a warm day in late January, the girls were buzzing about, pretty as you please. Like many of us in the Northeast, we experienced extreme swings of bitter cold and unseasonably warm weather throughout January and February here in Fairfield County, Connecticut.

    Less than a month later, upon returning from a few weeks in Florida, I snuck a peak on another warmish day. To my surprise and dismay, the hive was dead.

    I will follow up with a full postmortem when the current foul weather breaks, but I am alternating between anger and sadness, just like AB. In fact, I’m beginning to wonder, “Is this just too hard?” Bees survived for millions of years without us, and now, employing the best practices I have read and learned about, I am a bee-killer, not a bee-keeper.

    I don’t give up easily, and have a nuc on order for this spring. As in the past, I will seek advice from local experienced bee-keepers in our Backyard Beekeepers Association. So, we’ll give it another go, but I’m just not sure how much more of this I can take.

    • Barry,

      You’ve probably read my words before. Bees survived millions of years without us. True. But now they have us, and that is the real problem. We’ve stressed them, changed their environment, imported diseases and parasites from all over the world, moved them around from crop to crop, laced their food with poison, forced them to live in pre-fab boxes, fed them things they wouldn’t eat in nature, and then rob their honey. There is no doubt in my mind that “us” is the problem.

      As I’ve also said before, I think varroa and the associated viruses have taken the fun out of beekeeping. We do it because we admire the bees, but keeping them alive and healthy is extremely difficult and often depends on things outside of our control.

      I understand how you feel because not a day goes by that I don’t wonder how much longer I’m willing to deal with it.

  • I’ve searched your site and this seems like the best place to ask this question. When cleaning a dead out what if anything do you do about the dead head down bees in the cells?

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