Western Honey Bee - Thermoregulation

Thermoregulation

The honey bee needs an internal body temperature of 35 °C (95 °F) to fly — which is also the temperature maintained within the cluster. The same temperature is required in the brood nest over a long period to develop the brood, and it is the optimal temperature for the creation of wax. The temperature on the periphery of the cluster varies with the outside air temperature and in the winter cluster, the internal temperature may be as low as 20–22 °C (68–72 °F).

Honey bees are able to forage over a 30 °C (54 °F) range of air temperature, largely because they have behavioural and physiological mechanisms for regulating the temperature of their flight muscles. From very low to very high air temperatures, the successive mechanisms are: shivering before flight and stopping flight for additional shivering, passive body temperature regulation in a comfort range that is a function of work effort, and finally, active heat dissipation by evaporative cooling from regurgitated honey sac contents. The body temperatures maintained differ depending on caste and expected foraging rewards.

The optimal air temperature for foraging is 22–25 °C (72–77 °F). During flight, the rather large flight muscles create heat, which must dissipate. The honey bee uses a form of evaporative cooling to release heat through its mouth. Under hot conditions, heat from the thorax is dissipated through the head; the bee regurgitates a droplet of hot internal fluid — a "honeycrop droplet" – which immediately cools the head temperature by 10 °C (18 °F).

Below 7–10 °C (45–50 °F), bees become immobile, and above 38 °C (100 °F), their activity slows. Honey bees can tolerate temperatures up to 50 °C (122 °F) for short periods.