Saw several of these flies, busily feeding on Common Knapweed.
No interactions present.
This is a female empidid, and compared to the empidid species that I've found, yours looks most like Empis tumida. I can't be absolutely sure of this since I'm not familiar with all that many of the related species, but as far as I can see it's a good match. However, Empis femorata is very similar (down to small differences in the colours of some of the hairs). I can't find any other photos of Empis tumida on the web, but E. femorata can be seen at:
Entomologist and biological recorder
Many thanks for that probable ID Martin; I have no references for Empididae and it sounds like it would be a tough ask for someone at my level even if I did.
Is the short abdomen a sign of it being female? Also, would it have been feeding on nectar or hunting for insects in the flower head? I've always thought that Empididae were all predators.
According to Milan Chlava's book on the genus Empis, this family of flies can be traced back to Mesozoic times, when they were originally predators, before plants had started producing nectar. However, since then many empidid flies have evolved to take advantage of nectar as a food source, and for most species in the genus Empis nectar-feeding is now the main feeding habit, although some are still predatory in part. In particular, the males often catch other insects and provide them to females as a 'wedding present', and the females may require this protein meal in order to develop their eggs successfully. So these flies have interesting and quite complex patterns of behaviour and feeding.
I've only seen the female of this species, but judging by the illustrations the in Chlava the male does have a more slender abdomen, and like many male empids also has quite large and obvious genitalia structures at the tip of the abdomen. The simple pointed tip to the abdomen in your photos shows that it is a female.
Thanks for that information Martin, fascinating stuff.
How useful is a lateral view like this for identifying Empididae? (I have another one from the same site that I was thinking of posting.)
To fully key out empids you may need to see a whole range of characters, including wing venation, hairs and bristles on the legs and various parts of the body, and details of the head. For many species the safest way to identify them is from the male genitalia, which in some species is very distinctive and can be seen from a side view of the tip of abdomen.
So an identification may or may not be possible from a side view, but we might as well have a go!
Lat/Lng: 52.5, -1.2
OS grid ref: SP5497