Fly heaven

A couple of clumps of Eryngium (Sea Holly) in the garden have been covered in flies all day - there must have been seven or eight different species. This one was most attractive, but I haven't yet had time to track it down (at least to the level of genus) in my books. There is so much going on in my little garden (168 sq metres) - why do I need to spend time at the nature reserve, which is 3630 times the size? Don't answer that!!