Midlatitude survival ofAnticarsia gemmatalisHübner, the velvetbean caterpillar, is related to cooling degree-days (°C-days<10.9°C). Model construction required a cooling degree-day algorithm and spatial distributional-data of velvetbean caterpillar populations in Florida from November to March (inclusive). Model input required lower and upper developmental thresholds of the velvetbean caterpillar and site-specific minimum and maximum daily temperatures. Model output was cooling degree-days per 24 h per site. Total cooling degree-days at each site were used to delineate the midlatitude survival boundary for velvetbean caterpillar. The model was validated quantitatively. Extended calculations with the model delineated a midlatitude survival boundary in south Texas slightly south of Mission and Harlingen. Field-collected velvetbean caterpillar in Texas and Mexico validated the model's calculations.