The Crescent Helotropha leucostigma
Wingspan 37-44 mm.
Locally widespread throughout Britain, this is a species of damp, marshy woodland and moorland.
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.
It flies in August and September, the eggs overwintering and hatching in spring when the larvae feed on the stems of marshland plants, such as yellow flag (Iris pseudacorus).