The reduced risk of predation, increased foraging efficiency and resource sharing of group-living contribute to the dominance of social insects in most terrestrial ecosystems. However, because groupliving increases the frequency of interactions among individuals, it should also lead to greater transmission and prevalence of pathogens (Schmid-Hempel, 2017). Higher pathogen load could represent a substantial cost to social living that is rarely considered in models of social evolution. Comparisons between species of birds or mammals suggest that pathogen load increases with group size (Nunn et al., 2015;Schmid-Hempel, 2017). However, the species involved in such comparisons differ substantially in terms of ecological niches and evolutionary histories. It thus remains unclear if increases in group size result in higher pathogen loads. To test this, one should ideally compare the pathogen load in different social contexts within the same species.