Wolbachia is a group of maternally-inherited endocellular bacteria that manipulatearthropod reproduction to favor infected females. While strains of these bacteria have beenfound in all insect orders where at least 17% of all insect species infected, few studies haveinvestigated the distribution and effects of Wolbachia in natural populations. Here I present areview of Wolbachia research in the context of host biology (chapter 2) and I describe originalresearch (chapter 3) that details the distribution and effects of Wolbachia in a Neotropical beetle,Chelymorpha alternans, that is infected with two Wolbachia strains, wCalt1 and wCalt2. Inchapter 3 I describe the two strains based on three Wolbachia genes, I track their distributionacross space and time in host populations throughout the Panamanian isthmus, I determine straineffects on host reproduction, and I show a correlation between environmental effects and theongoing loss of one strain. This is the first study to show the loss of a Wolbachia strain fromnatural populations and I discuss the possible factors responsible for the loss.