I’m partial to these small powdery blue butterflies. I saw this little fellow along the trail at St. Francis Wood in Libertyville. They are similar to spring azures, but much easier to study as they will settle down for you. Azures are very skittish, in my experience, and difficult to sneak up on.
The little tails off the hind wing resemble antennae. In fact, when at rest or nectaring, eastern-tailed blues rub their hind wings together so it looks like the “antennae” are moving. This confuses predators long enough to allow the insect to escape in the other direction. It seems to work for them, as I have often seen them with a beak-shaped holes in their wings where the tails used to be. I’ve painted this one a bit larger than life.