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A species identified as Euleia heraclei, (No 3 in the rogues gallery above,) was chestnut brown. This one is tending towards black. Can they be the same species?
Looking at your photo again I'm a bit more certain of my ID. The wings are twisted down so what I took to be the leading edge of the wing is the trailing edge.
Many thanks, Mark
Lat/Lng: 51.44, -0.02
OS grid ref: TQ377730