Spicebush Swallowtail butterflies have a beautiful iridescence on their lower wings. The females show blue (this is a female), and the males shine green.
Our woods are filled with spicebush shrubs which is why we have a number of these lovely insects. They also like to eat (as caterpillars) sassafras and tulip poplar. Adults are nectar feeders.
Their range is generally east of the Rocky Mountains with some in the southern areas of Canada.
This picture was taken June 8, 2011, in Green Lane, PA.