When I first noticed these little flies feasting on the nectar of Wild carrot flowers, I thought perhaps they were sawflies but, when looking at my photos on my laptop later, I realised their heads were far too small.

Turns out these are some kind of fungus gnat though, according to the NatureSpot website, there are several species with the same bright yellow abdomen. So, although these flies look very like the Sciara hemerobioides shown on that website, I’ve recorded them as Sciara species. As you may have worked out, it’s the larvae that feed on fungus, whereas the adults prefer umbellifers and other flora.