Thesis Colloquium at CES on 22 April 2019 at 10:00 am titled "A place for everything and everything in its place: Spatial organization of individuals on the nests of Ropalidia marginata" by Nitika Sharma from CES, IISc
Animals across taxa and habitats are known to use available space non-randomly. They are known to concentrate their space use around locations rich in food, mates or refuges. There could also be cascading effects of such disproportionate use for the individual itself, its conspecifics or even the landscape it inhabits. In addition to using their habitats non-randomly for foraging, avoiding predators and optimizing homing routes; some social insects were also discovered to use their nest space non-randomly. We tested if the primitively eusocial paper wasp Ropalidia marginata used its nest space non-randomly and indeed found a majority of individuals using parts of the nest more intensively than expected by chance (spatial fidelity). We tested several hypotheses that were primarily based on studies on ants, to understand the relationship between the social and spatial organization of individuals in social insect colonies. We found that the non-random space use by adults within R. marginata nests is a result of maximizing nutritional exchange and minimizing disease spread in the densely populated colonies. In addition, in order to understand the role of non-random space use by adults on task performance, we tracked individuals while they performed the task of food distribution, as it is the most conspicuous and important task in social insect colonies. We found that wasps within a feeding bout cooperatively (and often repeatedly) fed the randomly distributed larvae, thus minimizing the chances of any larvae going hungry. Each wasp that fed larvae in a feeding bout optimized its feeding route by minimizing the distance per unit larvae it fed. We conclude that understanding the spatial organization of adults might help us better understand the mechanism of efficient division of labour on social insect nests.