Yellow Swallowtail - Dark Morph

A few days ago I posted photos of a female eastern tiger swallowtail butterfly. I learned that while the males are always yellow, the females can be either yellow with some distinctive blue markings, or very dark. A couple of days ago we saw one of the dark females. They have the same blue spots as the yellow-form females, and although they are indeed dark, the wings are translucent when the sun is behind them, creating an interesting effect.

The swallowtails seem very attracted to the purple coneflowers that are growing in our front flowerbed.