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All Epiponini wasps are polygynic, with multiple queens alternating over the colony cycle. There are several potential queens in the early stages of this cycle, but as it progresses, the number of queens is reduced. Because most individuals remain reproductively totipotent, there is great potential for conflicts over reproduction. Workers could have an advantage in controlling queen production because they are much more numerous than queens. Nevertheless, the queen selection process is little known for Epiponini. For this reason, we aimed to study the behaviour of queens and workers during queen selection in multiple species of Epiponini, integrate information from previous behavioural studies, and perform a comparative analysis to interpret changes evolutionarily. We conducted observations on nine species belonging to five genera: Brachygastra, Chartergellus, Metapolybia, Polybia and Protopolybia. Females were individually marked to make direct and video observations. Queen production was artificially induced. A total of 28 behaviours related to queen selection were identified. The most aggressive interactions between castes, such as bite and dart, were lost in the major lineages of Epiponini. Bending display I is an ancient behaviour used as the main dominance display. Behaviours exhibited by workers to test queen status arose in the common ancestor of the Epiponini and are not shared by other polistine wasps. Consequently, the act of workers testing queen status probably was present in the Epiponini ancestor. Ritualized test display and dominance behaviours are used in Epiponini as honest signals of the queen's reproductive potential instead of aggressive behaviours. Caste flexibility had already been suggested as the ground plan for Epiponini and is herein discussed as decisive for colony survival of swarm wasps, because it allows colonies to respond efficiently to different situations that may eventually arise., (© 2023 Willi Hennig Society.)

Neotropical swarm-founding wasps are divided into 19 genera in the tribe Epiponini (Vespidae, Polistinae). They display extensive variation in several colony-level traits that make them an attractive model system for reconstructing the evolution of social phenotypes, including caste dimorphism and nest architecture. Epiponini has been upheld as a solid monophyletic group in most phylogenetic analyses carried out so far, supported by molecular, morphological and behavioural data. Recent molecular studies, however, propose different relationships among the genera of swarm-founding wasps. This study is based on the most comprehensive epiponine sampling so far and was analyzed by combining morphological, nesting and molecular data. The resulting phylogenetic hypothesis shows many of the traditional clades but still impacts the way certain behavioural characters, such as nest structure and castes, evolved, and thus requires some re-interpretations. Angiopolybia as sister to the remaining Epiponini implies that nest envelopes and a casteless system are plesiomorphic in the tribe. Molecular dating points to an early tribal diversification during the Eocene (c. 55-38 Ma), with the major differentiation of current genera concentrated in the Oligocene/Miocene boundary., (© The Willi Hennig Society 2020.)