Yellow jackets are wasps.
That's technically true, and I couldn't tell you what specific species got me, but it's a common brown wasp you see all over the DC region under almost any eave. Yellow jackets are primarily found in holes in the ground, though I did find a humongous nest inside the wall of my house when I had deck replaced with a porch. I knew there was a nest inside the porch light fixture, so a couple of days before construction started I sprayed the fixture so the construction guys wouldn't get stung.
Well, when they tore the drywall down inside the space they discovered a huge nest - 18" long and about 6" wide - inside where the electric wire ran. Those little bastards had a FAR more extensive next and much larger population than I had ever guessed. If I had not sprayed and the had broken into the wall there, there would have been 500 yellow jackets angry and loose in the house. Oh man, what a disaster that would have been.