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Great set of photos, Jeremy! Males are certainly easier than females and I think the clear view of the antennae in the 2nd picture really helps to rule out fuscipes, where the flagellum is short and there is a hump on inside of the flagellum. Both can be ruled out from that picture.
Edit: Having said which, the first picture seems to show a hump on inside of the antennae! The problem of photo IDs...
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I've checked the original pictures again and find they're spread over about 12 minutes. There could be three individuals here. The only ones I know are the same are pics 1 & 6, followed by pics 2 & 3, The one in 2 & 3 might even be dead. I recall it seemed trapped in web, and when I prodded it, it sort of moved ie. it was pliable, and I picked it up from the underside of the leaf and placed it on top and opened the wings without any resistance. I wonder if that makes more sense of the 'hump' you've spotted in image 1.
If your id is based on 2 & 3 then I can safely leave them and put the others separately as assorted beris? I'll do that. I would've thought they were just chloromyia at the time which in turn I'd just learnt to tell from melanostoma etc. Yes I know. I remember even thinking I could collect the ill one but couldn't imagine what I'd do with it. It seems so many flies ago..
Edit: or I could just leave it, as you think. I did want to ask if the the antennae of male geniculata are slightly shorter than the female?
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I'd be happy with the above as evidence of at least one Beris geniculata; even if there is another species involved I don't think I could confirm another one from these photos, the really dark legs look much more like geniculata than anything else. Let's see what ophrys thinks as well though.
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Just had a look at a male of each and the male fuscipes has a lot of yellow on the legs and a very short flagellum, in comparison to the geniculata. On the basis of that, I'd say all the above are almost certainly geniculata. I have very little experience of fuscipes beyond a couple of specimens, though.
Edit: By sheer coincidence, I am just going through some flies from a local spring-fed valley and in there was a male Beris fuscipes! Quite a good record for here and again with quite pale tibiae and tarsi in comparison to your flies.
might as well add the rest then. I hesitated at geniculata initially as I thought the antennae a bit short
Lat/Lng: 51.5559, -0.0242
OS grid ref: TQ370859