On May 30th, I showed a couple of images of what I supposed was the leaf-miner Cheilosia semifasciata. This identification has now been confirmed by a leading European authority on leaf miners (his website is: www.bladmineerders.nl). It turns out that this is an extremely rare species that needs a very specific habitat: Navelwort (or close ally) in deep shade. But even when suitable environments are examined in detail, they are usually not found, so something else must be an influencing factor.
This species is so scarce and under-documented that I have decided to show all the details I have, in the hope that others might be able to record it, too.
Here is a shot of the location I found it in:
The bank on the left had Navelwort all the way along it, but the mining stopped abruptly at the line where the sunlight started.
Here's a (flash!) shot showing how obvious the miner is:
Have a look at your shaded Navelworts and see if you have any.