Obtained the Nearctic Diptera Manual section on these flies. I am going to add the images to my website of body and head shapes. I think this more elongate and shiny thoraxed species is Rainieria. And we only have one species R. antennaepes. Facial and eye shape and the darkened wing markings may be helpful. This is a female again. A side shot of males may easily separate the genera on these flies. Compare this with the likely Taeniaptera species here at bugguide as well.