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Richmond Park on fencing, about 2mm

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Looks like Medetera (Dolichopodidae).

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thanks, looking through gallery Medetera tristis looks a good match.

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Dear all,

I would like to point out that Medetera in the Palaearctic is by far the most difficult (and very speciose) of all genera to identify. One of the reasons is that most species do not show decisive diagnostic features, apart from the male genitalia.

So I would recommend to be very cautious with putting names on specimens of this genus, unless important features are well visible.

Cheers,
Marc