Observations on the natural history and behaviour of the primitively eusocial wasp Ropalidia cyathiformis (FAB.)(Hymenoptera:Vespidae)

Abstract

This paper reports on natural history and behaviour of the primitively eusocial wasp Ropalidia cyathiformis, which builds small, open, paper carton nests and exhibits an aseasonal nesting cycle. The number of adult wasps on a nest ranges from one to about a hundred, and nests last from a few days to sixteen months or more. Most colonies have a single queen, who is morphologically similar to her workers but has better developed ovaries. Female wasps exhibit several dominance behaviours which are positively correlated with rates of snatching food and building material from incoming foragers,and also of feedinglarvae andbuilding the nest. This suggeststhat behaviourallydominantindividuals specialize in performing intra-nidal tasks includingbrood care. Queens are the most behaviourally dominant individuals of their colonies and appear to inhibit worker reproduction and regulate non-reproductive activities of workers using dominance behaviours. Our observations suggest that R. cyathiformis is a typical example of a primitively eusocial species, in striking contrast to the congeneric R. marginata which exhibits some features reminiscent of more advanced eusociality.Queens of R. marginataare behaviourallydocile and appearto use a non-behavioural (probablypheromonal) method of regulating worker reproduction. Non-reproductive activities of workers in R. marginata are regulated in a decentralised, self-organised manner without the involvement of the queen.Acomparative study of R. cyathiformis and R. marginata will be valuable in understanding the evolutionary transition from primitive to advanced eusociality in general.