Wingspan 45-65 mm. The yellowish females are slightly larger than the orange-brown male but both sexes usually show the two distinctive white spots on the forewing.

Most frequent in marshy places and riversides but also in drier grassy terrain.

Flying at night, in July and August, the males especially are attracted to light.

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. Grasses and reeds form the bulk of the foodplants.

The species is fairly common in the southern half of Britain. In a recent survey to determine the status of all macro moths in Britain this species was classified as common.

Fairly common in Leicestershire and Rutland, but possibly declining. L&R Moth Group status = A (common and resident)