Confidence: It's likely to be this, but I can't be certain.
Notes: Looking at the wing pattern in the photos the two outer dark marks are joined by a very narrow bridge. In the keys and photos of C jaceae where they join at the outer margin they are the same thickness. http://www.diptera.info/photogallery.php?album_id=52&rowstart=60
Sadly O. falcata is not illustrated on this site. May be you could post the photo on the Diptera Info site and let us know the outcome.