How do busy bees avoid overheating from flying?

Amazing stuff! 

Was it necessary to kill the bumble bees to make these measurements? "Upon completion of the experiments, unneeded individuals were humanely euthanized in accordance with approved protocols." and "To precisely measure this airflow’s cooling potential, Glass and his colleagues then euthanized 18 bumble bees. Into each they inserted a tiny temperature probe, heated the body to 50°C, and placed it into a wind tunnel that could mimic the air patterns and velocities the team had measured around a hovering bumble bee."

"... But no one had quantified the cooling that comes from air flowing around a bumblebee’s body generated by its beating wings. ...

They calculated that as a bumblebee hovers in place, the breeze it generates can lower the insect’s body temperature by 5°C. The “whopping” magnitude of that cooling means that this fanning effect is a big deal for a flying insect  ..."

From the abstract:

"Understanding how flying insects manage heat exchange is critical for predicting their survival in dynamic thermal environments. To fly, insects propel air downwards to offset body weight, inducing airflow over their bodies. Remarkably, the potential cooling effect of this self-generated airflow is largely unstudied.

We measured induced airflow and wingbeat kinematics for hovering bumble bees (Bombus impatiens) across a range of body sizes and then measured the cooling effect of airflows of the same magnitude in a vertical wind tunnel. We combined these data in heat balance models to predict transient and equilibrium body temperatures of hovering bumble bees with and without self-generated wind. Measured self-induced airflow was substantial (up to 1 m s−1) and varied with body size and wingbeat kinematics, contributing significantly to thermal stability. Without this self-induced airflow, simulated bees of all sizes rapidly overheated across a range of environmental conditions, highlighting the importance of this overlooked heat-loss mechanism in the heat budget of flying insects.

Our findings suggest that shifts in wingbeat kinematics required for altered force production not only affect energetics and, therefore, heat production, but also alter the induced airflow and associated convective heat loss."

ScienceAdviser

How do busy bees avoid overheating from flying? "New measurements could help predict pollinators’ ability to withstand climate change [??? really]"

Induced airflow cools hovering bumble bees (open access)

Fig. 1 Factors affecting the body temperature of a hovering bumble bee in still air. To stay airborne, a bumble bee relies on flight muscle metabolism