A central theme in ecology is understanding the factors that influence interacting animal and plant species. This study focuses on the role of a plant host as a driving force for genetic changes in herbivores. In this study, I focus on tree-feeding lepidopteran larvae found in forests of central Maryland for genetic host-associated differentiation. Larvae were collected from three different tree species at three different sites in Maryland. DNA was extracted from the adult moth for analysis of genetic differentiation. Using Amplified Fragment Length Polymorphism (AFLPs), each species was examined for host- or site-associated genetic differentiation using GeneMapper and neighbor-joining trees were constructed using the Nei Li similarity index. Genetic differentiation is a species-specific phenomenon, i.e., species in the same assemblage respond differently to selective forces associated with host plants and site. This study expands on our knowledge of how generalist species interact with their host plant in a spatially structured environment.