Insect societies such as those of ants, bees, wasps, and termites account for nearly half of the insect biomass in some habitats. Cooperation and division of labour are two important features responsible for their evolutionary success and ecological dominance. Their division of labour can be of two kinds: reproductive and non-reproductive; the first regulates who will reproduce in the colony (queen) and who will not (worker), whereas the second regulates what kind of tasks a worker will perform. Using the Indian paper wasp Ropalidia marginata, we investigated the minimum requirements for the emergence of cooperation and division of labour. To do so we reared wasps in the laboratory as singletons, pairs or triplets. We show that (i) all wasps in pairs and triplets cooperate with each other to build nests and rear brood, (ii) two wasps are adequate for the emergence of reproductive division of labour and cooperation and that three wasps are both necessary and sufficient for the additional emergence of non-reproductive division of labour and (ii) reproductive division of labour and cooperation are inadequate for increasing productivity, which comes about only with the addition of non-reproductive division of labour. By observing the social interactions between the wasps in the pairs and triplets, we show that aggressive interactions, often called dominance-subordinate interactions mediate the emergence of both reproductive and non-reproductive division of labour. In pairs, the dominant individual invariably becomes the queen while the subordinate individual becomes the worker. In triplets, the most dominant individual becomes the queen, the next most works at home while the least dominant individual works away from home. Wouldn’t it be nice to know how division of labour is organised in other animals, including humans?
Brahma, A, Mandal, S and Gadagkar, R. 2018. Emergence of cooperation and division of labor in the primitively eusocial wasp Ropalidia marginata, Proc Natl Acad Sci USA, doi: 10.1073/pnas.1714006115
Centre for Ecological Sciences; 11th January 2018