Purple Treble-bar Aplocera praeformata
Wingspan c. 34-40mm.
With just a couple of records in Britain, one in 1919 and the other in 1946, this remains an extremely rare vagrant to these shores. It occurs in continental Europe, where it can be found on the wing in July and August.
It is slightly larger and darker than the two large Treble-bar species in Britain, and fairly distinctive in appearance.
The larval foodplants are St. John's-wort (Hypericum).