The name probably derives from the "Common Yellow Dung-fly", S. stercoraria, which is one of the most abundant and ubiquitous flies in many parts of the northern hemisphere.
I think all (with black antenna) are the common Scatophaga stercoraria. I'm not sure if IMG_6950s.jpg also is the same species. Probably a Scatophaga sp. Presuming these are from Europe.