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 lab our in five post-emergence colonies of the primitively eusocial wasp Ropali dia 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 di stinct groups of individuals, based on their spatial distribution relative to the nest. Individuals could be assigned to a group based on: whether the y spent most of their time near or away from the nest (first principal comp onent, 75% variance), whether they sat on or next to the comb when in the n est vicinity (second principal component, 16% variance); or whether they sa t on or off the capped cells (that contain pupae) when sitting on the combs themselves (third principal component, 6% variance). Colonies had either o ne or two reproductive individuals, but the distinct groups they belonged t o could vary. In three monogynous colonies reproductive individuals spent t he majority of their time sitting on capped cells. In two polygynous coloni es, primary reproductives were also located on capped cells but the seconda ry reproductives, with smaller oocytes, were located either next to the nes t or on the capped cells of a second comb. In all colonies levels of aggres sive interactions were low. These findings indicate that spatial position i s an important component of social organisation and that there are multiple pathways through which an individual can achieve reproductive dominance. F inally, comparison with other Ropalidia species shows that the pattern of s ocial organisation varies in this wasp genus.