There are only two records from Lewis, the most recent in May 2022. The flight period is May to June in mixed woodland and copses. The larval food-plants are birches (Betula spp.) and other broadleaved trees plus shrubs. It has a distinctive single deep scallop on the hindwing and the white moon-shaped marking on the forewing give rise to the common name.

References: 
Leverton, R. & Cubitt, M. (2024). The Larger Moths of Scotland.
Waring, P. & Townsend, M. (2018 third edition). Field Guide to the Moths of Great Britain and Ireland.