Something is eating my Poppy.....please help

Hello,

I am new to this forum and came across it by accident so I wonder if there is anybody out there that can help me with my dilema.  I have planted so many poppies over the last 2 or 3 years and every time the leaves are being eaten by something..... I cannot see any signs of slugs or any other culprits for that matter on the part of the leaves that are left... Please help as they are such lovely flowers!!!!  many thanks