A desert bee thermoregulates with an abdominal convector during flight

Area of Science:

• Insect physiology
• Behavioral ecology
• Thermoregulation

Background:

• Endothermic insects, like the Sonoran Desert bee (Centris caesalpiniae), thermoregulate to optimize flight performance.
• Males of this species cease flight as ambient temperatures peak, suggesting a need for thermal management.

Purpose of the Study:

• To identify the thermoregulatory mechanisms employed by male Centris caesalpiniae bees during flight.
• To investigate how environmental temperature influences their physiological responses.

Main Methods:

• Measurements of tagma temperature, wingbeat frequency, water loss rate, metabolic rate, and tagma mass in flying bees across a range of air temperatures (19-38°C).
• Utilized a heat budget model to analyze thermoregulatory strategies.

Main Results:

• Thorax temperature was maintained between 38-45°C, while head and abdomen temperatures were lower and less regulated.
• Increased use of the abdomen as a heat convector was observed as air temperature rose, indicating active heat transfer.
• Mass-specific metabolic rate increased with temperature, and water loss rate increased with air temperature but was a minor thermoregulatory mechanism.

Conclusions:

• Male Centris caesalpiniae primarily regulate thorax temperature during flight by increasing convective heat loss via the abdomen at higher ambient temperatures.
• This mechanism allows for sustained flight activity during cooler morning hours and avoidance of overheating during peak temperatures.