A Marsh/ Black-spotted Snipefly, Raghio tringarius, or similar species, a group sometimes called Downlooker Flies from their habit of perching on tree trunks looking downward for prey. Proboscis said to be like beak of a Snipe (bird), hence Common Name. They suck blood or predate by sucking aphids/ other invertebrates. #ScottishWildlife #InvertFest #Snipefly
Good info on Rhagio Downlooker Snipeflies here:
https://www.wildlifetrusts.org/wildlife-explorer/invertebrates/flies/downlooker-snipefly