Effects of light and density on herbivory in California live oaks (Quercus agrifolia) were studied at the border of oak woodland and grassland habitats. Location of sampled trees varied in amount of light and tree density. Herbivory, as estimated by insect abundance, percentage of leaves eaten, and percentage of leaf area eaten, showed significant variation between habitat types. Light availability significantly impacted herbivory, which increased as a function of shade for all measurements of herbivory. Leaf thickness, which estimated physical impacts of ecosystem variation on the trees, was inversely proportional to shade. Density had no effect on either herbivory or leaf thickness.