Fly identification?

[bigzee]

The last few weeks I've seen a particular fly around in the countryside over here, but I don't recall seeing it before and don't know what it is. In the absence of a photo or specimen I will attempt to describe it:

It is about the same size as a large house fly, but moves less quickly, and is distinctive in having a tapered body/abdomen than hangs down at 45 degrees. It seems to be black in colour and present in swarms. They do not seem to be a pest to humans as they did not enter my open car window at lunchtime, and at an outdoor lunch at a nature reserve last weekend they were not diving on our tucker like the usual types.

Any clues anyone?, as my limited literature on the subject sheds no light, nor does google.

[JonnyP]

Try looking up St Marks fly.. Sounds about right to me, and the right time of year for them. Its the males that will group up and dance, as per most flies..
I saw plenty of them at the RV during the plant walk..

[fish]

other wise known as bibio marci or the hawthorn fly. great time for fishing an imitation by fly rod for the wild brown trout down our way.

[bigzee]

Yep - they look like the ones I'm on about. They may not attack our food but the unattractive way they flop about in the air is enough to put you off anyway!

Thanks for setting me straight on that one gents...ya learn summats new every day!