Behavioural and morphological dimorphism of the sexes: an account of two primitively eusocial wasps

Abstract

In social Hymenoptera, foraging, nest building, brood care and all other colony maintenance functions are carried out by the females while males function solely as reproductives. This asymmetry in social roles of the two sexes has led social insect researchers to focus almost exclusively on the females whereas males have remained relatively neglected. We studied two sympatric, primitively eusocial wasps, Ropalidia marginata and Ropalidia cyathiformis, and compared the morphological and behavioural profiles of males and females. Males of both species are smaller in size and weigh less compared to females. Males of the two species live in the nest for different durations. Borrowing from the ecological literature we use novel methods to compute and compare behavioural diversity and behavioural richness and show that females of both species are behaviourally richer and more diverse than the males.

Keywords:

• social wasps
• behavioural diversity
• behavioural richness
• sexual dimorphism

Acknowledgements

This study was supported by the Department of Science and Technology and Ministry of Environment and Forests, Government of India. RS was supported by a Senior Research Fellowship of the Council of Scientific & Industrial Research. All data collection and analysis were performed by RS under the supervision of RG. RS and RG co-wrote the paper. We thank S. Amador, B. Klein, H. Ishak and U. Mueller for constructive comments on an earlier version of this manuscript.

Note

Supplementary material can be viewed online.