Wingspan 37 to 44 mm. In addition to the typical form there is a well marked variation, ab. fibrosa, which is just as frequent, as well as several intermediate forms.

A species of damp, marshy woodland and moorland.

It flies in August and September.

The eggs overwinter and hatch in spring when the larvae feed on the stems of marshland plants, such as Yellow Flag (Iris pseudacorus).

Locally widespread throughout Britain. In a recent survey to determine the status of all macro moths in Britain this species was classified as local.

Occasional in Leicestershire and Rutland. L&R Moth Group status = C (very scarce resident or rare migrant).