Gut microbiota of the European earwig (Forficula auricularia)
Gut microbes typically play a role in the expression of many host traits, such as development, reproduction and behaviour. More recently, it has been suggested that the latter effect may favour the evolution of sociality in hosts, as microorganisms could make them more sociable to increase host contacts and thus improve their transmission. Although this prediction has received contrasting support from theoretical work, the potential role of gut microbes in the transition from solitary to social life has not been empirically investigated. Here, we addressed this question using the European earwig, an insect that retains the unique ability to naturally switch between solitary and social life.