we were having a similar experience, looking through that category. I found some that looked like mine, while others in there look very different - color, body shape and posture. Seems like it would make sense to group them the way you suggest. Who's the fly expert around here?

I just noticed there is a key, that would probably do it. I'll see if I can get it as a download from work, but I'm not sure if we have a JSTOR subscription.

I can't believe you are messing with BugGuide on a Friday night! I thought only old boring people like me did that.

I am actually still at work tonight, burnt out on this project that was supposed to have ended two weeks ago but still lives through a thousand iterations and tweaks requested of me, and needing the occasional distraction. If I weren't at work, I wouldn't be on the computer after a day like today for sure! Despite that, I find BugGuide to be a great place to spend an evening - I decided I must be getting old myself when chilling out at home after a week of work became a preferable way to spend a Friday evening over going out. ;-)

It is, isn't it? It really puzzled me when I found it, before I took some photos I could view larger. Such a strange posture! It looked like it had no butt.