Wingspan about 15 mm.  This species is distinctive for its rather long and narrow forewings, with a horseshoe-shaped whitish blotch on the dorsum. The hindwings are whitish with a dark border.

Unless identified by a recognised expert, a photo is required. If the photo doesn't show the key ID features then in the comments box describe the size and identifying characters you have observed.

Well wooded areas where Oak is present.

Adult moths fly early in the year, from March to May, and can sometimes be found on the wing in the afternoon. They also fly later at night and come to light.

The larvae feed inside oak-apple galls and other, spongy galls made by Hymenoptera on oak (Quercus). Their presence is sometimes betrayed by frass exuded from the gall.

This species was previously regarded as local and infrequent in Britain. In the Butterfly Conservation's Microlepidoptera Report 2011 this species was classified as Nationally Scarce B, but the introduction of effective pheromone lures has proved that the species is much more common than previously thought.

Once regarded as a rare moth in Leicestershire and Rutland but the introduction of effective pheromone lures has proved that the species is much more common in our area than previously thought.