Little flashes of blue iridescence flitting through the garden quickly caught my attention.

A number of black butterflies sport blue iridescence in their wing scales, including the Pipevine Swallowtail, female Eastern Black Swallowtail, Red-spotted Purple, and the Spicebush Swallowtail. Which one was gracing our garden today?

The newly emerged beauty was a Red-spotted Purple, which I had not seen for several years! The much tastier (to birds) Red-spotted Purple Butterflies are thought to have evolved to mimic the foul tasting and toxic Pipevine Swallowtail. Red-spotted Purple caterpillars eat non-toxic leaves of Serviceberry, oaks, Black Cherry, aspens, birches, Eastern Cottonwood, and hawthorns, which would make both the caterpillars and adults appetizing to birds. By mimicking the Pipevine Swallowtail, which eats toxic foliage of plants in the genus Aristolochia, the mimics–Red-spotted Purple, Spicebush Swallowtail, and female Eastern Black Swallowtail–find some protection, to a certain degree.

Under wing, or ventral wing pattern

Upper wing, or dorsal, wing pattern

The beautiful blue iridescence in butterfly wings is created from the microscopic ridges, cross-ribs, and other structural layers of the individual scales, which play with light waves to reflect brilliant blues and speckles.

We had just watered the garden and I think the Red-spotted Purple was drinking up droplets of water. Perhaps there was salt or some necessary nutrients in the droplets when mixed with the foliage.