Females have two black spots on the upperside forewings, and a black streak on the forewing margins. Males lack the black spots. Both sexes have black wing tips.
Wingspan c 58mm (male), c 63mm (female).
Appears on wing in May, with numbers, augmented by migrants, increasing until August. Generally two broods, sometimes three. Overwinters as pupa.
May - September.
Found throughout the mainland, Western Isles and Northern Isles.