Termorregulação e atividade de forrageamento de melipona subnitida no bioma caatinga

This study aimed to evaluate the effect of the distance between the hive and the food source on the body temperature (TS), foraging activity and thermoregulatory mechanisms of the stingless bee Melipona subntida in the Caatinga biome. In addition, we developed an index for the evaluation of thermal stress conditions for bees (TSIB). M. subnitida bees were trained to forage in an artificial feeder containing 1.5 M sucrose solution ad libitum at 15, 50 or 100 m distance from the hives. The foraging activity was recorded by the number of bees in the feeder. TS was obtained by infrared thermography in three different body regions: head, thorax, and abdomen. Simultaneously, the meteorological variables were recorded. Absorbed solar radiation (RABS) and thermoregulatory mechanisms (convective heat exchange (HC) and long-wave radiation exchange (HR)) were estimated using biophysical equations. TSIB was obtained through two statistical methods: principal component analysis and multiple regression analysis. The greater the distance between the hive and the food source, the smaller the number of foraging bees. TS is influenced by distance and, in large part, by the meteorological conditions of the Caatinga biome. The higher the air temperature and solar radiation, the smaller the number of foraging bees and the higher TS. Body cooling by the HC increased as the wind speed rose and when the air temperature was low. However, this mechanism became inefficient in high air temperature, not being enough to compensate for all the heat received from the environment by RABS and HR. The bees had difficulty maintaining the thermal equilibrium with the environment when the food source was 100 m away from the hives. In general, the thermal equilibrium was reached in 15 and 50 m. The TSIB is given as: TSIB = 9.43 + 0.018 𝑅𝑆 + 4.895 𝑈 − 0.856 𝑇􀮺 + 0.291 𝑈𝑅 + 1.562 𝑇􀯀 , with R2 = 0.834