We had trouble this summer with some leaf-eating pest. It ate hostas, but other flower leaves too. Nothing was ever visable! No aphids, no worms, grasshoppers, or any other insect I could find. I was told at the nursery it was slugs or snails, but never saw any, or found any slime trails. Whatever it was has come inside with a beautiful containered colleous. I reasoned that, if it were night phantoms crawling out of the soil to eat the leaves, I'd just change the soil. So, I re-potted this week. (I couldn't find anything in the soil either!)But, the leaves are still being eaten! Oh, the culprit does leave one bit of evidence; small, black particles I assume are "droppings", i.e., dung. I don't know what to do since I don't know what I'm dealing with. It hasn't spread to any other plants (thankfully.) Any advice on the invisable culprit?