July to August. Common and well distributed to England, becoming more coastal to the north and in Scotland. Their name is derived from the habit of the caterpillars which are said to like drops of dew.

Distinguished from other large eggar moths by the diagonal cross line on the forewing and two small white spots. Males are usually a warm reddish-brown with yellowish patches. The females are larger and can vary in colour from deep yellow to a very pale buff, whitish or a darker reddish-brown similar to the male. In the fens of East Anglia the males are often yellowish.

The adults fly at night and are attracted to light, the males especially.