Elm Spanworm Ennomos subsignaria
Wingspan c. 40mm.
This North American species has been recorded in Britain just once, as an adventive, in 1984, when an adult was reared from a pupa found amongst asparagus at Covent Garden in London.
It is unlike any of the British Ennomos species, having unmarked white or creamy upperwings.
In its native habitat it has been described as a pest species that occasionally causes defoliation damage to a range of different tree species.