https://phys.org/news/2018-10-big-bees-hotter-temps-smaller.html

"Bees fall along this entire range," explained lead author Meghan Duell, a graduate student at Arizona State University. "Most [insects] employ some means of behavioral thermoregulation. As body size increases, it's more likely that insects will be able to behaviorally and physiologically thermoregulate, especially in flying insects. Bigger bees, like bumblebees or the larger species in the work I'm presenting, are partially endothermic. They can warm themselves by shivering their flight muscles to produce heat but do not constantly physiologically regulate body temperature."

Excessive heat, such as that in the rainforests of Panama where the bees in this study originated from, can limit a bee's ability to fly. "If bees stop flying as often in hot temperatures, the amount of time they have to forage (and therefore pollinate flowering plants) decreases. This can mean they aren't able to collect enough food to maintain the colony," Duell said. "On a large enough scale, this negatively impacts the overall bee population and the plants they pollinate while collecting pollen and nectar for food."