(Fischer von Röslerstamm, 1839)[Synonyms: Gynnidomorpha manniana]
Wingspan c. 10-13mm.
This species is locally common in southern parts of England, with records ranging norhwards to Lancashire and Yorkshire, and North Wales. It inhabits river banks, ditches and the margins of streams.
The larvae feed on water mint (Mentha aquatica) and gipsywort (Lycopus), living inside the stem, inside which they overwinter.
Adult moths fly from evening into the night, and are on the wing typically in June and July.