The Emerald Swallowtail (Papilio palinurus), also known as the Emerald Peacock or Green-banded Peacock, is a stunning butterfly native to Southeast Asia, found across countries like Malaysia, Indonesia, Thailand, and the Philippines. Its most striking feature is a broad, iridescent band of shimmering green-to-blue scales sweeping across its otherwise velvety black wings, an effect caused by microscopic scale structures that refract light rather than pigment alone, giving it a jewel-like, almost metallic sheen depending on the viewing angle. Adults have a wingspan of roughly 8-10 cm and are typically found in tropical forests, especially near streams and moist areas, where males often gather at mud puddles to absorb minerals. The caterpillars feed primarily on plants in the citrus family (Rutaceae), and like other swallowtails, they possess an osmeterium — a forked, foul-smelling gland that can be everted to deter predators.