Host-microbe interactions: Microbial organisms (bacteria, yeast, etc.) are ubiquitously found on animal hosts. These microbes can be essential for host development and nutrition, but they can also be pathogenic to the host. Moreover, microbes can use animals to vector between different hosts, facilitating the spread of infectious disease. We study the bacteria that live within filth flies (house flies and blow flies) to understand the evolution of microbes within hosts and the role that these flies play as vectors of pathogenic bacteria.