The significance of symbiosis in fungi-plant systems is well recognised and represented in the scientific literature. However, fungal-insect symbioses are less well understood, except for a few well known examples, even though they appear to be present in almost every terrestrial ecosystem. Recent molecular investigations suggest that there is a great diversity of fungi associated with insects, potentially forming complex and varied symbioses. These relationships could be of great interest from both an evolutionary and ecological perspective. The close association between the yeast, Kodamaea ohmeri and the small hive beetle, Aethina tumida suggests a symbiotic relationship. A. tumida is a serious pest of European honeybees (Apis mellifera) in Australia and the U.S.A. The yeast K. ohmeri appears to be carried by the adult beetle and has been shown to be associated with the fermentation of hive products during development of A. tumida larvae. In order to explore this relationship, we will establish whether the yeast is an obligate or facultative symbiont of this host, the reciprocity of this relationship, and so determine the contribution of the relationship to beetle bionomics and ecology. This will allow qualitative and quantitative evaluation of the nature of their biological, evolutionary and ecological relationships. These investigations will be used as a model to better understand the role of symbiotic microbes in the evolution of insects and their roles in contributing to better exploitation of certain niches in ecological systems.