This photo is of Papilio cresphontes also known as the Giant Swallowtail. This butterfly is a swallowtail and is common across the southern United States. Adults feed on a variety of nectar sources in gardens and the caterpillars are referred to as "orangedogs." The larval stages feed mainly on citrus and can be a pest especially in non-commercial settings.
This photo was taken at the Boston Museum of Science's Butterfly Garden Exhibit in the Spring of 2005.