Found this magnificent beastie hiding under the porch stoop. Thanks to v. belov at bugguide for confirming it’s a giant water scavenger beetle, Hydrophilus ovatus.

It flipped itself upside-down while I was photographing other stuff at the light, and started making a horrible buzzing sound. When I flipped it back over, it quickly scurried off the porch step and went diving into the dirt below.