The glassy-winged sharpshooter, Homalodisca vitripennis (Germar), vectors the bacterium Xylella fastidtosa that induces Pierce's disease of grape This study determined the effect of temperature on the feeding activity of H vitripennis adults and the resulting production of excreta. The Logan type I model described a nonlinear pattern that showed excreta production increased up to an optimal temperature (33 1 degrees C), followed by an abrupt decline near an estimated upper threshold (36 4 degrees C). A temperature threshold for feeding, at or below which adults cease feeding, was estimated to be 10 C using a linear regression model based on the percentage of adults producing excreta over a range of constant temperatures. A simulated winter-temperature experiment using fluctuating thermal cycles confirmed that a time period above the temperature threshold for feeding was a critical factor in determining adult survival. Using data from the simulated temperature study, a predictive model was constructed by quantifying the relationship between cumulative mortality and cooling degree-hours. In field validation experiments, the model accurately predicted the temporal pattern of overwintering mortality of H vitripenms adults held under winter temperatures simulating conditions in Bakersfield and Riverside. California, in 2006-2007. Model prediction using winter temperature data from a Riverside weather station indicated that H vitripennis adults would experience an average of 92% oyez-wintering mortality before reproduction in the spring, but levels of mortality varied depending on winter temperatures. The potential for temperature-based indices to predict temporal and spatial dynamics of H vitripennis overwintering is discussed