Diaphania costata (Fabricius) (Lepidoptera: Crambidae) is a leaffolder on Apocynaceae in the Neotropics and the southeastern United States. Adult moths photographed or captured at light in the United States have been commonly misidentified, and the species’ Nearctic distribution has been poorly documented. We provide diagnostic characters for larval and adult stages, compare it to related Old World taxa, and describe the damage to ornamental Vinca L. The species is not restricted to Texas but occurs as far east as the Atlantic Coast and as far north as Virginia. Specimens collected in daily surveys over many years indicate that the range of D. costata spread naturally from Louisiana and Texas from the 1980s into the 2000s.