Q: What is biting my canna leaves?
A: It’s a canna leaf roller, specifically the larger canna leaf roller, as opposed to the lesser canna leaf roller.
A moth, called the Brazilian skipper, lays her eggs on the canna leaves. When the pests hatch, they stitch the edges of the young leaves together, making a perfect hiding place. Keep an eye on the leaves as they unfurl and pull them apart.
The “bite marks” you see are caused when the caterpillar chews straight through a young leaf before it unrolls.
If you find a grub, flip it onto a surface nearby where a bird can get a snack. If you have too many plants to watch individually, spray the leaves as they unroll with Bacillus thuringiensis (click for sources).