What's been nibbling the water lilies?

Something has been making these neat oval cuts out of the water lily leaves in the pond. Further investigations found the matching cut-out pieces on, near or just under the leaves (see top left in photo). These pieces are actually little pockets and inside each one is a grub.

It is all the work of the Brown China Mark Moth, which lays its eggs under floating leaves and the larva burrows into the leaf for food and protection. When ready to pupate it makes these pockets, each half of cut leaf glued together by silky secretions. Moths are on the wing in June-July, so I'll be looking out for them.