I agree Sarah, are those light coloured marks on the apex/termen? I bred some through last year from Hearts tongue fern, but my photos are not very good I'm afraid.
Hi Ina. Yes, there are 4 pale marks near the apex which aren't described or illustrated in the Field Guide. I'd be interested to know what "The Moths of Great Britain and Ireland" says about the markings (I'm afraid I don't have a copy). I've looked at examples of this moth on various internet sites and many have these markings.