This research will test the effects of previous folivory on subsequent folivorous insect species via alterations in the shared host plant, particularly alterations in phenology. Specific factors hypothesized to influence such interactions, including extent of folivory (partial vs. complete consumption of leaves), amount of partial damage an dits effect on the third trophic level (natural enemies), timing of folivory and long-term effects of folivory, will be examined. These factors will be tested in a series of observations and manipulative experiments involving leafchewers (early-season feeders) and leafminers (late-season feeders) on the Emory oak, Ouercus emoryi. Preliminary evidence suggests such factors can change the outcome of interactions between seasonal folivores, and thus influence population dynamics and organization of folivorous insect communities. The project will quanfify phenological and chemical changes associated with varying folivory and their effects on colonization, local extinction, survival, causes of mortality, and fecundity of the leafmiing species on Emory oak. Although accumulating evidence indicates that plants change following folivory, the precise effects on subsequent insect species are equivocal. Yet such information is crucial in unerstanding how plant-mediated interactions influence population dynamics and organization of folivorous insect species sharing host plants.