Thats slug & snail damage .. artistic arent they! You can either grab your flashlight and go out at night with a jar of ammonia & water and pluck them off or you can get some slug & snail bait at your favorite store. I use slug & snail bait and go around once a week and scatter it everywhere.

X

Slugs are very intelligent. They have discovered that eating a hole in a furled leaf produces these patterns. There is probably a slug still around admiring its handiwork. :) Pellets work here in the UK too.
Nik

Hi ... I have the same pattern on my leaves ... but they like my hostas better than the cannas.