My dear Glory B, you do get some problems.
It looks very much like a leaf miner of some sort, you are quite correct in saying that you have seen them on chrysanthemums, you clever old thing
You also get them on celery, beet,delphinium, holly and lilac.
But i have never seen them on poppies before, with this and the slug damage you really are quite unique.
If it is only on one or two leaves i would just cut them off cleany, so as to leave it pleasing to the eye.
If it does return you might have to resort to spraying, but i don't think this will be the case if you are vigilant.
Kind regards the old Herbal Remedy.
This hot weather makes my hair rustle like pea straw.