Death recognition by undertaker bees

Abstract

Dead conspecifics removal is important of being social to avoid pathogen transmission, which resulted in the evolution of a specific caste of undertaking workers in all hives bee species. However, it is mysterious that how the undertakers distinguish death and life instantly. Through integrative studies of behavioural tests and chemical analyses, a novel mechanism for dead conspecifics recognition is found in the Asian bee Apis cerana cerana Fabricius. The bees detect quickly the death of conspecifics based on decreased cuticular hydrocarbon (CHC) emissions, caused by the cooling of the dead bee. Specifically, with the decline of body temperature in death, the CHC emission was reduced. Undertakers perceived the major CHCs. Addition of synthetic CHCs, followed by heating, inhibited undertaking behaviour. Among these CHCs, heptacosane and nonacosane are the major compounds in a natural bee hive, providing a continuous signal associated with life. Via changing the vapour pressure then the ratio of emitted compounds encoding the physiological status of signal sender, insect chemical communication can be finely tuned by body temperature. This straightforward death recognition mechanism requiring little cost can be universal in animal living in social groups, especially in the social insects. Body temperature affected behaviour can response to increasing frequency of extreme weathers in global climate change, which help explain the recent worldwide bee health problem.