swallowtail Definition

a deeply forked and tapering tail (as of a swallow)

tailcoat

any of various usually large brightly marked butterflies (family Papilionidae, especially genus Papilio) with each hind wing typically having an elongated process

a usually dark-colored New World swallowtail (Papilio polyxenes) having yellow spots on the wing margins and a black spot centered within a larger orange spot on the hind wing inner edge

a large widely distributed swallowtail (Papilio glaucus) of eastern North America that in the male is largely yellow with black margins and black stripes on the wings and in the female is usually similarly marked in the north but is very often all or mostly black in the south; also : any of several closely related black and yellow swallowtails (such as P. rutulus of western North America)