We see bees in visible light, comprising the colors of the rainbow. As we will see, there is another way to observe bees using heat. Bees as small creatures have a lot of surface area for heat loss or gain, relative to the volume of their bodies. In flight, a bee produces a considerable amount of heat in its thorax. Flight muscles occupy approximately 75% of the thorax, and the wings beat almost 250 beats per second to generate sufficient lift to get the bee airborne. These flight muscles have an “operating temperature,” a concept something like a car engine except if they become too cold, besides losing efficiency, their muscles do not function.
On a cool Spring day sometimes bees forage when they could chill. Occasionally, I see them just standing around on the ground. Then in a few minutes, they are gone. Provided they do not get too cold, bees can microvibrate their flight muscles. That is a kind of shivering, to heat their flight muscles up again, at least to fly for a short ways before cooling too much again, to return to their hive. But they could chill and die if they get too cold while on the ground.
The bees thermoregulate the core of the brood nest at a little under 95ºF (35ºC), which is near the core temperature of a person 98.6ºF (37ºC). Different strains of bees, in diverse environments, and using various measuring techniques, gave slightly different temperatures. The one below is a little lower than the one above. Bernd Heinrich, a famous insect physiologist, measured the thoracic temperatures of bees leaving, foraging, and returning to the hive (He also compared European and African bees. I am just using the European bee data.) With this kind of temperature measurements, two starting ones are important, the environmental (surrounding) temperature, called the ambient temperature, and the brood nest temperature, which Heinrich reports as a hive temperature. The ambient temperature was 46.4 – 73.4ºF (8 – 23ºC). The hive temperature was 89.6ºF (32ºC).
Bees leaving the hive were caught for thoracic temperature measurements as they cleaned their antennae, a behavior occurring as the bee stands on the alighting board, a moment before launch (easily observed by the way). Bees leaving the hive had …
