This paper expands on previous observations of Australian green carpenter bees by providing information about nesting substrates and the life cycle of Xylocopa (Lestis) aeratus and Xylocopa (Lestis) bombylans from more than 450 colonies from South Australia and New South Wales. Voltinism differs between the two species, but does not appear to vary within species from different locations, such as X. aeratus colonies on Kangaroo Island, South Australia and at Woy Woy, New South Wales. The architecture of nests (unbranched or branched) is related to the substrate diameter and may allow variation in social behaviour because different provisioning strategies can be used in the two nest types. Both species have some multifemale colonies for most of the year and this includes the brood-rearing period. Differences in voltinism, nest type and the occurrence of multifemale colonies during brood production are likely to lead to variation in social organisation within and between species.