Very small tachinid fly, about 3 or 4mm,common on Angelica at the moment. Too windy today to get a decent photo.
No interactions present.
I agree, but you also have to be careful to eliminate females of obesa, which can look very similar but that have pale hairs on the gena and usually a little dusting on the front of the thorax. If you then check the halteres barbifrons will be yellow, pusilla brown. The parafrontal will also be silvery and bare outside the frontal row, while barbifrons will be dark with many hairs between the frontal row and the edge of the eye - particularly towards the antennal base.
That's great, Chris...thank you. I have taken a fair few of these for checking over the last couple of days, on Angelica at a local wood (most umbels seem to have a couple), and so far have found a couple of pusilla and one small obesa, but most seem to be barbifrons on basis of yellow halteres and hairs on parafrontal area. Your detail here fits really well with the specimens I have looked at, so really useful, thank you very much.
I'll send you the records at the end of the year.
My Flickr photos...
Lat/Lng: 53.88803380063, -0.89153409004211
OS grid ref: SE729441
Woodland Trust reserve