Fornicating flies, Bibio anglicus

 A pair of fornicating flies settled on my trousers this afternoon on the Downs. Click on any picture to enlarge it.

 They obligingly crawled onto my finger without disturbing their copulation activity.  They are Bibio anglicus.

 The male has a big head and big eyes.  The female has a smaller head and smaller eyes.  Her head is black and her body redish.