Hi, I photographed two small flies feeding on the flowers of an umbellfer close to water this weekend (Sept 18th). I think they are tachnid flies, but I'm not sure, and would love to know the speicies.
I have many pictures, so if these fail tot show any key features, I can post more.
The musca and the tachnids do look very similar. In my field guide the lesser housefly (Fanniiidae rather than Muscidae) looked a possible match, but I think the wing veins are wrong. The housefly wing is a better match, but photo in my field guide shows it with an entirely black 'face'. (The picture of a housefly on wkipedia looks more like a lesser housefly, 'according to Collins complete British Insects'). None of the tachnidae in my guides are a perfect match either, but they have bits that look right, and the tachnid study website has hundreds of pictures of tachnid flies, several of which look quite like the ones I photographed, but the angle of the picture, or very dead nature of the specimen make it impossible for the casual viewer (ie, me) to really tell if they are a match.
The key ID clues are apparently a swollen post-scutellum, and a fan of hypopleural bristles. I just don't know enough to tell whether I can't see them in my photos because I don't know what I'm looking at, or because they're not there!
So you're right, it does look like a musca, but not like any specifically shown in my guides, and it also looks like a tachnid, but not any specifically shown in my guides. So I think I still need some help with this ID!