This is one of two harmless southeastern U.S. snakes whose bright colors have apparently evolved to mimic the highly venomous Eastern Coral Snake (Micrurus fulvius). The other mimic is the Scarlet Kingsnake (Lampropeltis elapsoides). I had yet to see either of those other two somewhat similar-looking snakes when I saw this one, but I did run across L. elapsoides not too far away a few years later.

The white blur in the upper right corner of this photo is the reflection of the flash off of a flying bug, one of approximately seventeen bajillion such bugs that swarmed around me and my flashlight beam as I tried to get this squirmy snake to stop squirming. (A few of the bugs are visible on the pavement here.) The bugs didn't seem to bite, but they did want to fly into every available orifice by the dozens. So despite this being quite a beautiful serpent, I didn't spend much time trying to get good photos.