As hard as bees toil during their peak seasons—pollinating and generally making sure humanity doesn’t come crashing down in a Biblical-level disaster—you’d think the colder months would bring some kind of hibernation or rest, even if it means snowy death.

For bumblebees, that’s generally true. Unable to tolerate lower temperatures, mass bee graves in northern regions are not an uncommon sight, with only the queen retiring to a warm crevice. But for the honey bee, winter is a time to buckle down and labor even harder in an all-out effort to extend their life span.

Their secret: fly without actually moving.

A single honey bee will typically die of exposure once temperatures plummet to 28 degrees. In order to survive, a colony will need to (literally) huddle together to create a communal furnace fueled by their body heat. That’s generated by the bees contracting muscles in the thorax responsible for flight. The wings remain still, but the energy created can raise a bee’s core temperature.  

Having morphed into tiny space heaters, the bees arrange themselves into a cluster not unlike a football huddle, their little bee heads touching and their abdomens (which are cooler) facing out. The outermost layer flirts with a cooler temperature of 46 degrees, chilly but survivable. They comprise the shell, or “mantle,” that protects the queen. In the core, insulated by layers of bees, the temperature can get up to a downright toasty 95 degrees.

Bees also react to environmental changes. If things cool down further, they can contract and raise the temperature; warmer ambient weather allows them to relax and spread out a little. The mantle isn’t always stuck with the worst job, either. They can regularly burrow their way into the core to enjoy the bee equivalent of a cozy fireplace.

Typically, the bigger the cluster, the less each individual bee will have to work in order to maintain their thermostat setting, and the better the chance is for overall survival. But a huddle of any size requires energy, and their stockpile of honey might be just far enough away in the hive that breaking off from the group could mean death. The cluster will usually move in unison to reach untapped honey stores.     

Despite the ability of the honey bee to adapt to frigid temperatures, in modern times their survival often requires beekeeper intervention. Bees in particularly cold regions benefit from a layer of fiberglass insulation around the colony. Beekeepers also keep honey stores stocked to ensure the bees will have enough fuel.