The Ulysses butterfly typically has a wingspan of about , but depending on
subspecies has some variations in size (western subspecies largest). The upperside of the wings are an iridescent electric blue; the underside is a more subdued black and brown. The colours are produced by the microscopic structure of the scales, a phenomenon called
structural colouration. The female of the species is different from the male in that she has little crescents of blue in the back, upside sections of her hindwings, where there is only black for males. When the butterfly is perched the intense blue of its wings is hidden by the plainer brown under side of its wings, helping it to
blend in with its surroundings. When in flight, the butterfly can be seen hundreds of meters away as sudden bright blue flashes. Males are strongly attracted to the color blue, including blue objects which are sometimes mistaken for females.
Karl Jordan in Seitz (83-85) provides a full account of
ulysses forma pdf ==Similar species==