# Bee Behavior Explained: Bearding, Washboarding, Dancing, and Sleep
You walk out to the hive on a warm evening and something is going on that you have never seen before. A curtain of bees hanging off the front. Or hundreds of them rocking back and forth on the outside wall in unison, like they are polishing it. Your first thought is that something has gone wrong.
Usually nothing has. Most of what bees do in plain sight has a good explanation, and knowing which is which saves a lot of unnecessary worry. One of these behaviors, though, has been studied for more than a century and still has no agreed explanation at all, which is worth knowing before you read an article that confidently tells you otherwise.
Bearding: bees hanging on the front of the hive
On a hot, humid evening you may find a mass of bees clustered on the outside of the hive, sometimes hanging several inches deep below the entrance. They are mostly still, with no obvious destination or task, simply sitting on the outside of their own hive.
This is called bearding, and it is a heat and space response. A hive full of bees is a hive full of small furnaces, and moving a portion of the population outside lowers the heat load in the box while freeing up room for the bees still working inside. It tends to appear late in the day, in the hottest part of summer, and it disappears overnight.
The thing worth saying plainly, because it is what most people are afraid of when they search: bearding is not swarming. A swarm leaves in a dramatic cloud and settles in a cluster somewhere away from the hive, usually in a tree or on a fence. Bearding bees stay put on their own hive front and go back inside when it cools. Our swarm management guide covers what an actual swarm looks like and how to prevent one.
Bearding does carry one useful signal. If a colony beards persistently, night after night, it is telling you it is crowded, and adding a box is a reasonable response.
Washboarding: the behavior nobody can explain
This one is genuinely strange, and it is the reason to be skeptical of confident answers.
You will see a group of bees spread across the outside face of the hive, each one gripping the surface and rocking rhythmically backward and forward, working the wood with their mandibles and front legs. They are spaced out rather than clumped, and they move in a loose synchrony that makes the whole hive front look like it is shimmering. It can go on for hours.
Now the honest part. Washboarding has been observed and studied for well over a century, and there is still no confirmed explanation for it.
The leading theories each have something going for them and none has been settled. Bees may be cleaning or polishing the surface. They may be spreading or reading scent. They may be sanitizing the area around the entrance. Or it may be coordinated social behavior that serves no single purpose we would recognize as a job. What is observed reliably is that it increases in hot weather and that it is usually done by younger bees.
Plenty of articles will hand you one of those theories as settled fact. It is not, and a behavior this visible remaining unexplained after a hundred years of people watching it is more interesting than a tidy answer would be.
Fanning, and how to tell the three apart
The third thing you will see on the hive front is the only one whose purpose is fully understood.
Fanning bees plant themselves with their abdomens angled down and beat their wings hard, driving a current of air through the hive. They do it to cool the colony, and they do it to evaporate water out of nectar on its way to becoming honey, which our guide to how bees make honey covers in detail. On a warm evening during a strong flow, you can often hear it from several feet away.
The three are easy to separate once you know what to look for. Bearding bees are still. Washboarding bees rock rhythmically in place. Fanning bees stand anchored with their wings a blur.
The waggle dance
Inside the hive, in complete darkness, a returning forager does something genuinely extraordinary.
She runs a figure-eight pattern on the vertical face of the comb, and the straight middle portion of that run, the waggle, carries the information. The angle of that run relative to straight up encodes the direction of the food source relative to the sun. The duration of the run encodes how far away it is. Other bees crowd around, reading the movement, and then fly out to a location they have never visited.
Karl von Frisch worked out what the dance meant and shared the Nobel Prize in Physiology or Medicine in 1973 for it. It is worth pausing on what is actually happening: an insect is communicating an abstract vector, direction and distance, symbolically, to an audience that cannot see her, on a vertical surface, in the dark.
Do bees sleep?
Yes, and this is settled rather than speculative.
Honey bees display all three of the behavioral hallmarks scientists use to define sleep. They enter a period of quiescence, becoming still with their antennae drooping. Their response threshold rises, meaning it takes more to get their attention. And their sleep is homeostatically regulated, which is the important one: a bee deprived of sleep will sleep more afterward to make up for it, exactly as a mammal does.
The finding that makes this more than a curiosity ties directly back to the dance. Research by Barrett Klein and colleagues, published in PNAS, showed that sleep-deprived bees perform less precise waggle dances. Their directional signaling degrades, which means the bees receiving those instructions fly less efficiently and the colony forages worse.
A tired bee gives bad directions, and the whole hive pays for it. That is a startlingly familiar problem for an insect to have.
How do bees fly?
You have probably heard that science says bumblebees should not be able to fly. It is one of the most repeated pieces of misinformation about insects, and it is worth clearing up.
The mechanics were worked out properly by Michael Dickinson and colleagues at Caltech, published in PNAS in 2005. Honey bee wings do not sweep in the long arcs you might imagine. They travel through a surprisingly short arc, roughly 90 degrees, and rotate as they come back, beating up to 230 times per second. That combination of short stroke and rapid rotation generates a leading edge vortex, a small spinning mass of air that forms over the top of the wing and provides much of the lift.
Their flight muscles are unusual too. Bee flight muscle has to operate fast and at a near-constant frequency to generate enough power, which is why bees adjust their flight mostly by changing stroke amplitude rather than by beating faster or slower.
As for the myth: it traces back to an old back-of-envelope calculation that treated a bee’s wing as a fixed airfoil, like the rigid wing of an aircraft. Under those assumptions the numbers really do not work. But a bee’s wing is not a fixed airfoil, it is a flapping and rotating surface generating vortices, and once you model it correctly the flight is unremarkable. The bee was never violating physics. The model was just wrong. Our bee anatomy guide covers the four wings and the hooks that link them in flight.
Other things you will see at the entrance
A few more behaviors worth recognizing.
Orientation flights are the one most often mistaken for trouble. On a warm afternoon, young bees leaving the hive for the first time hover in front of it in loose arcs, facing the entrance, memorizing its position and surroundings. The air fills with bees and it looks like a swarm starting, but they are facing the hive rather than leaving it, and it is over in half an hour.
Guard bees station themselves at the entrance and check arrivals, challenging bees that do not smell like the colony.
Robbing is the one that genuinely needs action. Bees from other colonies try to break in and steal stores, and the flight becomes frantic and directionless rather than orderly, often with fighting at the entrance. It is most common during a dearth and after careless feeding, which our feeding bees guide covers avoiding.
Undertaking is quieter. Bees carry their dead out of the hive and drop them some distance away, which is why you may find a small scatter of bodies below and in front of a healthy colony.
Frequently asked questions
Why are my bees hanging outside the hive?
That is bearding, and it is a normal response to heat and crowding rather than a sign of swarming. Bees move outside to reduce the heat load in the box and free up space, then go back in as it cools. If it happens night after night, the colony is probably telling you it needs another box.
Do bees sleep?
Yes. Honey bees show all three behavioral markers of sleep: they become quiescent, they respond less readily to stimuli, and they make up lost sleep afterward. Research published in PNAS found that sleep-deprived bees signal less precisely in the waggle dance, which reduces how efficiently the rest of the colony forages.
What is washboarding?
Washboarding is a rhythmic rocking motion bees perform on the outside surface of the hive, working the wood with their mandibles and forelegs, often for hours and most commonly in hot weather. Despite more than a century of observation, there is no confirmed explanation for why they do it.
Your next step
If you are worried what you saw was a swarm getting ready to leave, our swarm management guide covers the actual warning signs. To understand what all that fanning is achieving, read how bees make honey. And for the body doing all of this, see our bee anatomy guide.
Sources
- Klein et al., PNAS, sleep deprivation impairs precision of waggle dance signaling in honey bees.
- Caltech, deciphering the mystery of bee flight, on Dickinson’s wing stroke and frequency research.
- Carolina Honeybees on washboarding, one of several overviews noting the behavior remains unexplained.