www.ukbutterflies.co.uk

I presume the yellow butterfly is a clouded yellow but is the white one a pale clouded yellow or helice form? Thanks in advance for assistance.

Tricky one this, Ian. Normally, the giveaway is the far more extensive black margins on the uph of helice, but to get that in an image usually requires a backlit shot.

Perhaps Guy or Roger will be able to pass comment?

I Would go helice, as the black seen through the underside forewing is very wide, and has white spots inside it.