Small Mottled Willow Spodoptera exigua
Wingspan 26-32 mm.
An immigrant species, occurring mainly in the southern parts of England and Wales, but also found northwards to parts of Scotland. In good years, several hundred may occur.
Arrivals have been noted in most months from February to November, but the peak arrival period is from August to October.
It can resemble some other species, but holds its wings rolled around the body when at rest.
The caterpillars feed on a number of low plants, but are not often found in Britain.