"Social insects include some of the most ecologically dominant species in both temperate and tropical areas, and represent a major evolutionary transition in the development of complexity. Insect societies are consequently of considerable interest for biologists and the general public. One emergent field of special interest is the interaction between social insects and their parasites both because of the role these are likely to have played in the evolution of sociality in insects and the parallels with the challenges presented to our own societies by disease. However, most studies of social insect parasites have been limited to those that cause obvious symptoms of infection, whereas many are more cryptic. These include the ubiquitous bacterial parasite Wolbachia which has been the subject of an explosion of research in non-social insects in recent years. This project will use leaf-cutting ants as a model system to examine for the first time experimentally the fitness effects of Wolbachia infections in social insects. It will involve interdisciplinary collaboration and advanced training in key scientific skills (ecology and population genetics) that my molecular genetic PhD did not include. The fellowship will greatly enhance my potential for achieving a position of professional maturity and independence as a broadly trained biologist."