Figure 4. Thermal imaging data showing how the temperature of a Trigona carbonaria bee varies with time.

(A) Composite image of a bee immediately after completing a flight (T = 0) and at 5 s intervals whilst the temperature of the bee cools until close to the ambient temperature. (B) Plots of Trigona mean (+/− s.d.) bee body temperature versus time starting immediately after completing one of four different activities [not flying for at least 5 min (resting), flying, drinking from a feeder that is warmer than the ambient temperature, and drinking from an ambient temperature feeder] at ambient temperatures of (B) 23°C, (C) 30°C and (D) 34°C. At an ambient temperature of 30°C the data for bee relative temperature is consistent with that observed at 23°C: at both 23°C (B) and 30°C (C) ambient temperatures a flying bee attains a temperature that is hotter than that of a resting bee, and drinking from a warm feeder allows bees to maintain these higher temperatures. At an ambient temperature of 34°C (D), drinking from a warm feeder raises bee temperature to well above what is maintained during active flight. This suggests that drinking warm nectar may be an advantage at lower ambient temperatures when it allows bees to maintain a flight temperature during the time it takes them to imbibe nectar, but at higher ambient temperatures the warmer nectar may cause the body temperature to exceed the flight range and no longer provide a benefit. For B–D at T = 0, plots with the same number of stars within a figure are not significantly different (P>0.05); plots with a different number of stars are significantly different (P<0.01; Mann Whitney U test).