Ancestral state reconstruction using the stochastic character mapping method of Huelsenbeck et al. (2003), as implemented in phytools (Revell 2012), mapping the evolution of sociality across all hymenopterans, in comparison with the outgroup, Z. nevadensis. The pies at internal and external nodes represent the posterior probability distribution of 1 of 3 possible states: (1) Solitary, (2) Eusociality, and (3) Facultative sociality.