In fact, I had moved a few seedlings the day before and yesterday when I checked them out, this. What on earth has been munching the leaf.
I dug around in the soil and this is what I found.
I thought they were my friends. Two years ago the decollate snail started to show up. Like all snails the numbers of this snail have increased as the numbers of the small round snails, pill bugs and slugs has declined. I am very happy about that but is there so little for them to eat that they are now becoming vegetarian. I may have to reduce their population.