Did you know that one of the worker bee jobs in the colony can be working as a heater bee?
What does that mean? Pretty much exactly what it sounds like. Heater bees maintain the 92⁰-97⁰ temperature that is needed for brood to properly thrive. They will sit on top of the brood and move the muscles they usually use for flying. This increases their body temperature enough to keep the brood warm. If there is an empty brood cell next to a full one, a heater bee will go in headfirst and do the same thing, heating it from the side.
These are all heater bees keeping brood and SEVERAL capped queen cells warm on a walk away split.