The Rivulet Perizoma affinitata
Wingspan 24-30 mm.
A widely distributed species in Britain, but local in northern Scotland and Ireland, occupying woodland margins, hedgerows and grassy embankments.
The main flight period is between May and July, when it is often attracted to light.
Red campion (Silene dioica) is the preferred foodplant, the caterpillars living inside the seed capsules, eating the seeds.