Solitary and semisocial behaviour in the <i>Corynura</i> group: new findings in a clade sister to all other Augochlorini bees (Hymenoptera: Halictidae)

The great diversity of social organisation present in the tribe Augochlorini makes these bees prime candidates from which to study the evolution of social behaviour. The Corynura group, sister to all other augochlorines, is comprised by three southern South American genera: Callistochlora, Corynura and Halictillus. The nest architecture and social behaviour of Ca. aureoviridis, Co. ampliata, Co. bruchiana, Co. nahuelita, H. amplilobus and H. reticulatus were studied in Argentina. Conclusive evidence of solitary and semisocial behaviour were found in a group where only communal behaviour had been confirmed. Two species presented socially polymorphic populations. Previous studies are reviewed and all data analysed considering species’ flying periods. The possibility of eusocial behaviour is briefly discussed considering environmental factors. Since some of the species visit crops, these results are useful to develop techniques to manage native bees for pollination.