|Asterocampa celtis, Hackberry Emperor|
The Hackberry Emperor's species epithet "celtis" refers to their preference for the hackberry tree, Celtis occidentalis. Their larvae only eat the leaves of trees in this genus. The adults, however, eat dung and rotting fruit. I happen to have a dog who produces abundant dung and a peach tree in my backyard, and a couple hackberries on my property. I really threw a party for them. No wonder I've seen them all over the place.
Now that I've got a picture and put a name to this butterfly, it's the caterpillar I'm after. Hackberry emperor adults are perfectly charming, if a little drab. Their caterpillars are spectacular. Their heads are framed by a shield of spikes and they have two spiked tails on their rump. You can find pictures here and here.
Hackberry emperor caterpillars hide themselves in folded leaves during the day and come out at night to feed. Supposedly shining flashlights up into the canopy after dark is a good way to spot them. I'd love to get a look at these fantastical caterpillars, so I may very well try.