Life cycle and social behavior in a heathland population of Exoneura robusta (Hymenoptera : Apidae): Habitat influences opportunities for sib rearingin a primitively social bee

Montane populations of the allodapine bee Exoneura robusta Cockerell in sou thern Victoria, Australia, have been the subject of numerous studies of soc iality over the last decade. These populations are univoltine and colonies exhibit a semisocial/quasisocial polymorphism. Synchronous brood developmen t and restricted periods of egg laying in these populations severely limit opportunities for sib rearing by older daughters. Here, we report the life cycle and social behavior of a conspecific subcoastal heathland population from southern Victoria. Colony sizes and intracolony relatedness are lower in the heathland population, possibly because the nesting substrate is rela tively short-lived and spatially dispersed. Brood development is relatively rapid at the heathland locality, such that some colonies are able to produ ce a 2nd brood in late summer. As a result, opportunities for sib rearing f requently occur in heathland E. robusta, allowing for quite different forms of alloparental care than occurs in montane populations. The presence of o pportunities for sib-rearing behavior in this species provides evidence of habitat mediation of sociality that is not caused by latitudinal variation.