The Edward's Hairstreak is a common butterfly of the eastern United States. Caterpillars use oaks as host plants. Adults sip nectar from various flowers, including goldenrods, sumac, white sweet clover, and, as you can see in this photo, milkweeds. This butterfly's larvae is tended by ants. The ants consume nectar from the larvae and, in return, protect the larvae (and adults) from predators (Ohio DNR).We found this hairstreak in Carleton College's Upper Arboretum (a few minutes after finding the Delaware Skipper of a recent post).