I wage a daily war with the heater in my house. It’s a so-called “Smart heater,” with more buttons on the thermostat than your average cell phone; it either heats the house until I could bake a pie on the kitchen counter or it stays off until frost forms inside the windows. Some mornings I would swear that it isn’t just intelligent, it’s evil. As the frost melted this morning I watched my honeybees take their first flights. I realized that for a bunch of insects, they’ve got a pretty good system in place.
Honeybees have a remarkably specific set of needs: Not too warm in the summer. Not too cold in the winter and 94.3 degrees in the brood nest with just a smidgeon of humidity. Fortunately the hive doesn’t have a central heating unit – it has 30,000 of them. Each and every bee is a miniature heating system.
Their heater is based around the same set of equipment that runs their air conditioner in the summer – their wings and the muscles which drive the wings. The flight muscles in a honeybee do not attach directly to the wings. One nifty side effect of this is that bees can trigger their flight muscles without shooting up and crashing into the lid on the hive. The result is like letting a car idle on a cold morning; it doesn’t go anywhere but the engine gets hot.
In the winter I start my wife’s van so she doesn’t have to climb into a car that feels like an icebox. One morning I started her van…and she did not go out. I figure it ran for hours before it finally ran out of gas. “The van won’t start, and it’s cold,” she said on the phone. I was never clear on which one aggravated her the most. Honeybees have a similar problem. Running their engine keeps them warm but costs fuel – honey. If they run out of gas they will die but letting the cluster cool too far is not an option. A chilled bee with a crop full of honey will freeze to death just as surely as the starving bee head down in an empty cell. To understand that you need to know how a bulldozer is like a bee.
Terry was a bull dozer driver who once did pipeline work in Alaska. He was from far West Texas, and in his vernacular you changed a flat tar on your car, and rubbing sticks together would build a far. When sautéed in whiskey like he usually was, he actually became more understandable. In the evenings he would drink until his blood could be used as deicing fluid. Then, powered by ethanol and regret he would launch into stories. Most of them involved a deadline, a bulldozer, Terry, and a miracle wrought by combining the latter two.
I was struggling to start the charcoal grill when he glanced over and said “I could teach y’all a thing or two about building fires. Learned it in Alaska, I did.” Learned-it-in-Alaska-I-did was well known as code for “Hand Terry a drink if you don’t want to get him started” but we were out and I was bored so he continued.
“Built a brushfire every morning under the cat,” he slurred. Cat lovers, put away your claws; I knew he mean the Caterpillar bulldozer, the “only woman that never left him, cheated on him, or turned him in to the police.”
“You built a fire under the bulldozer?” He wiped his nose on his sleeve, slung his feet off the lawn chair and swung to focus both of his eyes as best he could on me.
“See, gets cold up there. And diesel, diesel don’t burn when it’s cold. You let that cat get cold and you’ll never get it going again. Not till spring, or you borrow a blowtorch, or you build a fire under it.”
“Don’t they have electric block heaters?”
“Boy, you got an extension cord that’ll reach to Anchorage? If you can’t build a fire you got to keep it running.”
We leave Terry in his alcohol induced reverie to take a look at the intersection of honeybees and construction machinery. Honeybees do not run on diesel – they run on sugar, carbohydrates. Still, like Terry’s beloved Caterpillar their flight muscles have a definite operating temperature. Should the temperature of a bee’s thorax drop below 10.6 degrees Celsius the flight muscles will shut down. At that point the muscles are so cold they won’t start again without something else warming them. You can’t build a brushfire fire under a bee. Please don’t try.
So the bees have to keep warm just to be able to keep warm. But who decides how warm is warm enough, and how cold is too cold? The colony don’t have single thermostat – each bee has her own. Every honeybee has their own threshold for “time to light the fire” and “time to take off that sweater.” It’s one of the traits inherited through drones – workers from different fathers have different thresholds for heating and cooling. The result is that a genetically diverse colony is kept at more even temperature as hundreds of tiny heaters come off and on at different temperatures. It’s like if I warmed up the van for my wife and then turned it off to save gas. Then when it cooled down I went out and turned it back on and then back off. Now imagine that you have to do this for months on end, twenty four hours a day. This is exactly what the bees in the cluster do.
If that were the only way to keep warm I’d park the van in my living room. You might think that if the van were parked in the living room I wouldn’t need to warm it up, but thanks to that heater you would be sadly mistaken. Having the van inside would have a number of benefits: First, it would free up the carport for more beekeeping equipment. Secondly, the heat radiating from the engine would warm the rest of the room as well as the inside of the vehicle. There are two downsides that I see: Carbon monoxide poisoning and having to explain to my neighbors why there’s a van in the house. My wife would never tolerate having to explain that to the neighbors. Still, the idea isn’t all wrong, because it’s the same location clustering bees choose to park their heaters.
In real estate, three things matter: Location, Location, and Location. In honeybee clusters the same is true. Only the bees inside the cluster make a concerted effort to raise the temperature. That isn’t cruelty to the outer bees – it is efficiency. The inside bees are in the best position to share heat with their sisters. Their wing muscles actually grow more efficient as they get warmer, so the inside bees are best suited for generating the most heat. There is another reason for this as well, one that isn’t immediately obvious.
In order to divine the other reason why the inside bees do the heating and are kept the warmest, you would need to tattoo a hive. Well, maybe not tattoo it, just mark every single bee. All of them, each with a different color based on what day they were hatched. Then you’d force the bees to cluster by sticking them in a freezer. Then you’d take the cluster apart, layer by layer, counting the bees by color. What you would discover is that the cluster order is not random. The bees at the center of the cluster are the youngest. The bees on the outside are the older bees, sacrificed as insulation so that the colony preserves its hope in the safest, warmest areas. Oh, and any drones that happen to be around in cluster conditions, they’ll make their way to the center too. This seeming waste is in fact required, because drones are sperm containers with wings and chilled sperm is ruined. So the drones are no gentlemen – they’ll elbow their way to the center and let the women face the cold. To add insult to injury, drones are poor heaters compared to the workers, even in the cozy heart of the cluster. No wonder the girls kick them out.
The mantle bees get the bad end of the deal. They act as living insulation, growing ever colder as temperatures drop. Their abdomens rapidly drop to near ambient temperature. They will run their flight muscles just enough to keep them operational. When they can no longer warm themselves they pass into a chill coma, still holding tight. In a chill coma the bees appear dead until their temperature rises. When it does they will twitch and skitter and take off on a mad hunt for something to eat. Never forget about the chill coma. I had a friend drop off a mating nuc that had frozen to death for me to look at. We went downstairs to look at honey labels. The nuc stayed upstairs on the table. I can still hear the screams.
So, to recap: Honeybees keep warm by idling their engines. The cluster acts as a massive traffic jam full of minivans pressed bumper to bumper, cargo rack to undercarriage, where the vans in the center have their engines fired up and the climate control cranked to 94.3 degrees. Every single driver turns their car on or off as needed to keep others warm, except the outer layer of minivans. The drivers on the outside layer of minivans have to sit and shiver and wonder how badly their paint job is getting messed up. If one van begins to run out of fuel it can siphon it from a neighbor, unless the neighbor is all out. At the center of the heap of vehicles are the youngest drivers with the newest model cars, along with the car factory forewoman. If the minivans get too cold the drivers pass out, but if things warm up they might be able to wake up and drive to a gas station and refill. Finally, all of the male drivers were thrown out before the convention started and refused to stop and ask for directions back to the hive. If the workers had just explained that the alternative was spending months in the dark with thousands of females with nothing to do but talk, the drones would probably have left willingly.
Every afternoon at 2:00 my heater comes on, convinced that we will be getting out of bed soon and the house should be warmed. It continues in this pattern until sometime in late September, when the display switches to “summer” mode and essentially refuses to come on at all. The honeybees handle the change of seasons with ease. Millions of years have programmed their thermostats with not only daily patterns but entire seasons, based not on a digital clock but a sundial. Whether it is heating the cluster through the winter dark or raising cooling breezes under August sun, the bees can handle it. They balance thirty thousand tiny heaters to stave off the cold and keep the brood just right. In the spring I think I’ll bring one in to look at my thermostat. It’s either that or read the manual. In reality I know one of those two isn’t an option at all. Of course I’ll ask the bees.