Wingspan 13-19 mm
Although when well-marked this species is fairly distinctive, poorly-marked specimens are difficult to separate from other Bactra species.
The adult moths fly in June and July and occupy damp marshy habitats. It is locally common over much of the British Isles.
The larvae feed in the stems of rushes such as commmon club-rush (Schoenoplectus lacustris) and compact rush (Juncus conglomeratus), hollowing out the stem.