Lesser Swallow Prominent Pheosia gnoma
Wingspan 45-50 mm.
A fairly common moth throughout most of Britain, this species is very similar to Swallow Prominent (P. tremula), but can be identified with care. Compared to that species, gnoma has a more distinct white wedge at the tornus of the forewing, and lacks the wavy white line in the blackish area of the hindwing.
There are two generations, on the wing in May and June, and later in August.
The larvae feed on birch (Betula).