Social insects - especially bees, wasps, ants, and termits - are diverse, abundant, ecologically important, and incredibly successful: in some habitats they may constitute more than forty per cent of the total animal biomass. This book provides an up-to-date account of this group, reflecting the widespread and increasing interest in the ecological and evolutionary causes underlying the evolution of complex animal societies.

The book explains how this high success rate is due to the highly efficient division of labour within social insects' societies, central to which is the number of queens cohabiting within a nest. Queen number affects critical components of social organization such as genetic relatedness, reproductive strategies, sex ratio, and the nature of conflicts among nestmates.

Multiple queen colonies provide one of the most fascinating systems from which to study conflict and cooperation in animal societies, ensuring the book's value for all studying social behaviour.