honey bee behavior ventilation

Why do bees collect on the bottom board?

Brood nest temperatures remain fairly constant throughout the year at 93°-96° F (34-35° C.) But while a colony in late winter may consist of only 10,000 bees, a summer colony averages about 50,000 bees—and in some cases the summer population may reach 70,000+. With all those bees in the hive, the brood nest has to be cooled to keep it at the ideal bee-rearing temperature.

As temperatures increase in spring and early summer, it is not unusual to see throngs of bees sitting on the bottom board near the entrance to the hive. Even early in the morning after a cold night, they may be all lined up, looking like they are about to swarm.

However, congregating at the entrance is normal behavior for this time of year. Think of it this way:

Even a small cluster in the dead of winter manages to keep the brood nest warm. Individual bees take turns pressing their bodies against the brood and, by doing so, the baby bees are incubated at a cozy ninety-some degrees Fahrenheit.

But as the outside temperature gets warmer, so does the inside temperature. In addition, the number of hive occupants rises dramatically. So, instead of having a heating problem, the hive now has a cooling problem. Too many bee bodies sitting on the brood may make the brood too hot for optimum development.

In addition, the vast number of bees in the colony restricts the air flow through the hive. This occurs at the same time that the bees are trying to dry down the nectar and turn it into honey.

In response to these problems, the bees congregate in different places. They begin by sitting on the bottom board. As temperatures rise even more, the bees may “beard” on the outside walls of the hive, or hang in festoons from the landing board. Think of sitting on the front porch to stay cool on a hot summer’s day—same thing.

Follower boards and slatted racks can both provide additional congregation areas—places where the bees can sit without overheating the brood or restricting air flow through the hive. You can also help by providing screened bottom boards, screened inner covers, and upper entrances—all of which increase air flow through the hive.

I am probably guilty of over anthropomorphizing bees, but it is one of the easiest ways to figure out what they are doing and why. We need to stay warm in winter, and so do they. We need to stay cool in summer, and so do they. When we have excess moisture in our homes, we try to remove it—and so do they.

Remember, though, that even if the air feels chilly to you, the bees have huge numbers of individuals in their homes that we don’t have. So even a modest increase in the outside temperature can have a significant impact on the inside temperature, and the bees react accordingly.


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  • If I can get enough time off work, I hope to build and install some follower boards soon. The slatted racks, which I’d have to build myself with limited carpentry skills, are another story. Thanks for the info.

  • Thank you. As usual, this makes so much sense. It also validates your idea that full sun may not always be the best place for a bee hive, especially in ridiculously “mild” climates, like Florida, where 60° is labeled “chilly”.

    I have a screened bottom board and I am still seeing bearding. I’m thinking of giving my bees some additional shade, or space or both.

  • I haven’t had the chance to build slatted racks yet. But for the time being I have some ekes with 4 x 1.5″ holes with fly screen on them above the inner cover. The inner cover hole is 2.5″ so that should help get some convection flow going on to help remove some heat/humidity within the hive.

  • I’m wondering why I see dead larvae on the screened bottom board of one hive. I have two hives and before putting on an entrance reducer, I looked under the hives to see if I could see any mice. I didn’t. Under one hive I could see a big group of bees in the middle even covering the screening. In the other hive i didn’t see many bees, but I did see about 2 dozen dead larvae, or bits of larvae. There aren’t dead larvae outside the hive, This hive is very quiet and has an Italian queen, and seemed to be doing really well in the summer. The other hive has a definite bussing and has a Carniolan queen. They were both taking in lots of pollen last week, and they both have syrup. Do I need to open it, or maybe they got chilled last week when I opened the hives. It was around 65/70 degrees.

    • First off, dead larvae are not unusual. All year long the workers will expel larvae that they think are sick, deformed, not developing properly, riddled with parasites, or whatever. The percentage of expelled bees may be quite high at times, but it is an important mechanism by which the bees keep the colony healthy. In the fall, you may see more dead larvae than at other times because the bees will also expel any drones. It sounds to me like your hives are doing fine.

  • Rusty,

    Have a question and need a suggestion, I might be in the wrong blog but I have screened bottom boards and you and your colleague, or better half, had a discussion regarding screened bottom boards awhile back during fall and winter months. I have three hives that my bees are clustering under the screen all night and day and I would like for them to go to there right place. Yes I know they are bees LOL! And I can’t tell them where to go, but it’s becoming not thirties but now hundreds.

    It started back when I installed robber screens mid September. Are these still robbers or residents can’t tell. I have removed robber screens and replaced them with 3/4-1″ reducers . There does not seem to be any robbing now to my knowledge and I’ve been checking hives regularly, and outside activity as far as fighting goes. None! I thought about closing the screened bottom board off with the mite board for awhile to redirect them. But I thought I would get your input first, do to ventilation issues. Temperatures are the same as yours I suspect—mid to low 40s, mid to low 60s day time. They do not not leave all day.

    • Dave,

      First, I would dearly love to know who you think my “better half” is. My husband is not a beekeeper and rarely comments on anything I write, unless it’s to correct my grammar. So, I’m really curious.

      Second, it’s been a while since you wrote this comment, so I assume you’ve worked it out. Bees do a lot of bearding in September, and many times I’ve seen mine hanging off the bottom screens. They get over it, eventually. It’s not worth worrying about. The robbing screen reduced the air flow through the hive and they got hot and decided to stay outside. I think closing the mite board would only make it worse, since it further blocks air flow.

  • Feb 28 2014 found newly laid eggs on screened bottom board. Its is the first time I have seen anything like this with my 7 hives just seeing if you had any input.

    • Anthony,

      I don’t have a mental image. Are the eggs on the wire of the screen or are they spanning the holes? Have you seen anything living down there, like a fly or moth or beetle? Is anything attending to the eggs? Too weird.

  • Regarding Dave’s problem with the bees under the screened bottom board, mine do the same thing. It’s 38 degrees here in NC today and there’s a cluster of bees huddled up under there trying to stay warm. I find a lot of dead bees on the ground under the hive. It’s like they don’t know how to get out from under there and die.

  • Rusty, the eggs are on my clean out tray under the screened bottom which I use to check varroa mites and to close up bottom for winter. I am pretty sure they are day-old bee eggs . The hive is the weakest hive I had ever had coming out of winter, and after thinking it over, it might be do to the recent cold snap here in Al and the result of bees clustering too tight to cover all of brood. Out of town working and have not been able to check hive on good days.

    • Anthony,

      It is very possible that workers would decide to shrink a brood-rearing area during a cold snap. However, I have read that the workers usually eat the extra eggs. It is nature’s way of recycling the nutrients that went into the production of those eggs instead of wasting it.

      Do they always eat the eggs? I don’t know the answer to that.

      Many different creatures can live in the debris of a bottom board. Speaking only for myself, I’m sure I couldn’t distinguish day-old bee eggs from dozens of other insect eggs if they weren’t sitting at the bottom of a wax cell. Perhaps that is my own shortcoming, but my guess is those eggs are from something else. Like I said, just a guess.

  • Hi Rusty,

    I live in middle TN and I installed 2 Nucs 5 days ago and noticed tonight that 20-30 bees were grouped together under the hive on the outside of the screen on the bottom board. Is this a normal place for them to congregate? Could it be that they are still getting used to the new home? The bees in this hive are active and feeding heavily on an internal feeder so they seem content. Just thought it was odd. On the other hive there are no bees hanging out in the same place.

  • Rusty, I love your blog! My husband and I are newbees 🙂 and have 2 hives. One hive is robust and healthy. The other hive was also, but suddenly something has changed. We found a huge pile of live bees in front of the hives, like a swarm, but on the grass. We left them overnight to see if they would go back into the hive, but they did not. The next day we gently brushed them onto a shovel and found a queen with them. We put them into a nuc box until we could figure out what was happening. Upon checking our weak hive we found the population low, many dead pupae and larvae on the bottom board and also some dead bees. We could not find evidence of a queen, so we assume the swarm we found on the ground with the queen came from this hive. There was plenty of room in the hive, so they didn’t swarm due to crowding. The number of dead pupae concerns me. What would cause this and is it why the queen left? We want to requeen this hive, but I’m wondering if there is a disease and we would just be wasting time and money. PLEASE HELP!!

    • Tammy,

      I don’t know the answer. Are there enough bees in the hive to form a colony? Are there swarm cells in the hive? It doesn’t sound like a swarm, although swarms have been known to settle on the ground. But all the dead bees, larvae, and pupae makes it sound as if there is a disease of some sort in the hive and perhaps the queen and the rest absconded in order to escape whatever it is. On the other hand, if there are still lots of bees in the hive and queen cells, perhaps it is just a swarm.

      Does anyone else have an opinion?

  • I have a small group bees on the landing all day and they still there in the morning the weather about 73 day and 56 night.

    • David,

      Apparently, that’s where they want to be. I would just leave them alone.

  • Good afternoon ….
    I have a screened bottom board …..is there any use for the bee waste that is found under the screen???…. its seems to be a lot of pollen…i am wondering if there is a way to clean it of the mites and other bad stuff and possibly give it back to the bees of use and eat…

    • I think cleaning it sounds too much like work, but I’ve heard it makes good fertilizer.

  • Hi Rusty, I really enjoy your website and posts. I had a hive that swarmed 3 times in April and then went back into the hive. The third time, it decided to start building a hive under the screen bottom board. I’ve removed the bees twice, placed them into a nuc, but they returned and started to build a new hive. Out of curiosity, I have left them alone and they have a separate queen, eggs, honey, and some of the most beautiful natural shaped honeycomb I’ve seen. The hive they’re under also has a queen, eggs, and is doing a great job collecting honey. Any recommendations as to when I should separate the two hives and give them their own home?

    • Andrea,

      Soon, I think. The longer you wait, the harder it is to do. I would cut those combs at the top and tie them into frames.

  • Thank you for the quick response Rusty. I’ve never tied comb into frames before. This is a pretty large hive and might fit into a deep. Any advise how to do this or video you can refer me to?

    Thanks again.