A type of butterfly with a tail that looks like the tail of a bird called a swallow.
Swallowtail butterflies are usually thought of as very pretty and delicate.
Examples:
I saw a swallowtail in the garden.
The swallowtail has yellow and black wings.
The swallowtail butterfly is very beautiful.
The swallowtail flies around the flowers.
The swallowtail is the prettiest butterfly in the world.
I want to catch a swallowtail and keep it in a jar.