The papilio thersites ia a butterfly endemic to Jamaica, also known as the Thersites swallowtail and, intriguingly, the false Androgeus swallowtail. Pictured on the stamp are male butterflies; the females are brown with a yellow curve arcing across their wings.
As you’ll see if you follow these links, the Wiki entry for this particular butterfly is somewhat short. To give you value for money, then, I searched for Thersites. Poor old Thersites. He was a bit player in the Iliad, later resuscitated by Plato, Shakespeare, Sterne and Goethe, and seems to have become a go-to for any writer who wanted to portray physical ugliness (there’s an element of cruelty in how he is treated by writers).
Back to false Androgeus: there are two listings for people called Androgeus in Greek mythology. The one that seems to work best is linked below and is a tale of mistaken identity, death, adoptive identity and general confusion. For completeness, I should tell you there is a Androgeus Swallowtail butterfly, found in Mexico and Central America; why this Jamaican lovely should be a false Androgeus and connected so deeply with someone deemed so ugly is beyond me…