Today I found something zipping around my apartment. It, like most flying insects, started smashing itself into the window screen, and so I went to take a look, and some pictures. They aren't very good pictures.
It appears to be a Steel Blue Cricket Hunter. A wasp from the Sphecidae family, Chlorion aerarium is related to other thread-waisted wasps such as the mud daubers, and digger wasps.
They look very similar to Blue Mud Daubers, but I live in the Northeast and Blue Mud Daubers range from Tenessee to Mexico. I live a little too far north for them I think, and therefore I think it's safe to assume there was a Steel Blue Cricket Hunter in my apartment.
Chlorion aerarium hunts crickets. Like most parasitic wasps, this one uses the crickets to incubate and feed its young. They actually eat sap from plants. Apparently they have been known to sublet Cicada Killer burrows, which I run into all the time.
The good news is I persuaded the wasp to fly out of my window without stinging me. Lucky me, lucky wasp.