Social and spatial organisation in colonies of a primitively eusocial wasp, Ropalidia revolutionalis (de Saussure) (Hymenoptera: Vespidae)

We investigated individual reproductive flexibility and the division of labour in five post-emergence colonies of the primitively eusocial wasp Ropalidia revolutionalis, by relating behavioural observations of individuals at the nest to their ovarian development. Analysing time-activity budgets with principal components and canonical discriminant analysis revealed three distinct groups of individuals, based on their spatial distribution relative to the nest. Individuals could be assigned to a group based on: whether they spent most of their time near or away from the nest (first principal component, 75% variance), whether they sat on or next to the comb when in the nest vicinity (second principal component, 16% variance); or whether they sat on or off the capped cells (that contain pupae) when sitting on the combs themselves (third principal component, 6% variance). Colonies had either one or two reproductive individuals, but the distinct groups they belonged to could vary. In three monogynous colonies reproductive individuals spent the majority of their time sitting on capped cells. In two polygynous colonies, primary reproductives were also located on capped cells but the secondary reproductives, with smaller oocytes, were located either next to the nest or on the capped cells of a second comb. In all colonies levels of aggressive interactions were low. These findings indicate that spatial position is an important component of social organisation and that there are multiple pathways through which an individual can achieve reproductive dominance. Finally, comparison with other Ropalidia species shows that the pattern of social organisation varies in this wasp genus.