As we did not record one Swallow Prominent in the garden last year I thought when I opened the trap this must be another Lesser SP...but I was wrong. I thought it timely therefore to post a photo to remind everyone of the difference. The moth, who was about to become a model, decided not to co-operate and did his best to keep his wings tightly shut whenever he saw the camera!
So, this is the best I could do and just to emphasise what you should be looking for I have ringed the area and included a better photo just in case you find a more co-operative beastie.
The tornal wedge shape on the fore wing is not considered totally reliable so the wavy line through the dark area on the hind wing is worth checking particularly as we get lots of individuals here that have the wedge half and half, it may be different in other areas.
To recap; wavy white line = SP. no wavy white line LSP.