Communication and recognition are essential for social life. Social insects are good model systems to study social behavior and complexity because their societies are evolutionarily stable and ecologically successful. Ants, in particular, show a large variety of adaptations and are extremely diverse. In ants, social interactions are regulated by at least three levels of recognition. Nestmate recognition occurs between colonies, is very effective, and involves fast processing. Within a colony, division of labor is enhanced by recognition of different classes of (...) individuals. Ultimately, in particular circumstances, such as cooperative colony founding with stable dominance hierarchies, ants are capable of individual recognition. The underlying recognition cues and mechanisms appear to be specific to each recognition level, and their integrated understanding could contribute to the identification of the minimum requirements for the emergence of sociality. (shrink)