The Two-Tailed Swallowtail is the largest Western Tiger Swallowtail. They stand out because they are bright yellow and huge in size, with two tails on each hind wing. They are found in western North America from Canada south to Central America. The caterpillars are apple green with camouflage markings. They feed on willow, cherry and ash. They can be found in semi-arid canyons, moist canyon bottoms, foothills, mid-level mountain areas, and gardens. The Two-Tailed Swallowtail is the Arizona state butterfly. I found these at Bubbling Ponds Preserve in the Verde Valley in Arizona.