No insects employ as varied thermoregulatory behavior as the honey bee Apis mellifera. They fan their wings to create cool air currents, spray water to induce evaporative cooling, and act as heat shielders by absorbing heat into their bodies and dissipating it to the hive periphery. This incredible thermoregulatory behavior is primarily used to protect developing brood, who can only survive in a narrow temperature range between 32-35°C. While the ability for honey bees to cool their hive in cases of acute heat are well documented, these behaviors may be maladaptive if carried out chronically. Active thermoregulatory behaviors like fanning are energetically expensive, and passive behaviors like heat shielding that expose bees to high temperatures can decrease adult lifespan. In order to determine whether honey bees can adaptively respond to chronic heat stress we heated a small test area of eight honey bee hives to 42°C for 8 hours a day for 3 months. Once per week for the duration of the study we measured the comb contents within the heated experimental area, as well as an identical sized unheated control area. Contents were divided into 2 categories: temperature sensitive brood, and temperature resistant non-brood.
Results/Conclusions
Over the course of the study we saw a significant decrease in brood presence and a significant increase in non-brood presence in heated areas, complemented by the opposite trend in non-heated areas. This study is the first to provide experimental evidence that honey bees can dynamically reorganize the structure of their comb to protect brood from areas repeatedly exposed to dangerous conditions.