The Drinker Euthrix potatoria
Wingspan 45-65 mm.
This species gets its English (and Latin) name from the habits of the caterpillar, which is supposed to have a liking for drops of dew.
The yellowish females are slightly larger than the orange-brown male, but both sexes usually show the two distinctive white spots on the forewing.
Flying at night, in July and August, the males especially are attracted to light.
Grasses and reeds form the bulk of the foodplants, and the species is fairly common in the southern half of Britain.