The commoner yellow form of the Eastern Tiger Swallowtail is a frequent visitor to the garden at this time of the year. I always enjoy seeing them, but the appearance of this dark morph female in the bergamot a few days ago was something to crow about.
All dark morphs of the species are female. They are examples of Batesian mimicry, a phenomenon in which members of a harmless species evolve to resemble another species which is toxic or unpalatable. The lady mimics the poisonous Pipevine Swallowtail butterfly, thus gaining a measure of protection from predators.



