Conserved hormonal and molecular mechanisms underlying behavioural maturation in open- and cavity-nesting honey bees

Division of labour in honey bees is based on a process of behavioural development where the worker bee successively performs different tasks at different ages. Workers start with tasks related to brood care and nest maintenance and move on to become foragers. This process of worker behavioural maturation is well studied in Apis mellifera. Juvenile hormone is one of the major drivers of this behavioural maturation, which is also accompanied by changes in brain physiology and anatomy including changes in neuronal gene expression and connections of neurons. Recent studies have identified whole networks of genes associated with specific tasks like nursing, guarding and foraging. Based on this detailed knowledge in A. mellifera, we ask whether major characteristics of the behavioural maturation process and the underlying hormonal and molecular changes are similar or different in two other honey bee species, the phylogenetically ancestral open-nesting A. florea and the more derived cavity-nesting A. cerana. Our behavioural studies show that workers of A. florea exhibit a slower pace of behavioural maturation and on average start foraging at a later age. However, the basic hormonal and molecular changes associated with onset of foraging are similar between both species. Based on our findings, we propose that evolution of accelerated behavioural maturation in cavity-nesting species is likely attributed to changes in the temporal dynamics of juvenile hormone titres.