This would be a new family in the Sphaeroceroidea... Collected 2 on my windows... I've been having fun(?) trying to key this out... the genus would be Gymnochiromyia ( 3 widespread spp.) based on the apparent lack of scutellar setulae.. McAlpine states that the females are commonly found on windows and have been reared from wood debris (which I have plenty of around here)... a second opinion is appreciated, but I'm feeling somewhat confidant about this ID

Here's the key from McAlpine's manual... good to add to the info page...

1a. Scutellum w/ 2-12 discal setulae in addition to 4 marginal scutellar bristles {Chryomya: 3 widespread spp.}
1b. Scutellum w/ 4-6 scutellar bristles only. {2}

2a. Frons w/ 3 pair of strong orbital bristles, the anterior pair incurved. Proepisternal bristle absent. Face w/o a keel {Gymnochiromyia: 3 widespread spp}
2b. Frons usually w/ 2 pair of strong orbital bristles (absent in A. aldrichi), the anterior incurved pair always absent. Proepisternal bristle present, though small. Face usually with a complete median keel. {Aphaniosoma: 3 widespread spp.}