The problem with chewing insects such as grasshoppers, beetles, caterpillars (too numerous to name) etc. is they move about and often are difficult to spot among the green foliage. Chewing insects can be large enough to see with the naked eye, but they can be green, brown, black, etc. so look closely and pluck off any you see on this plant or its neighbors as long as the infestation is not too extensive. If it is extensive, maybe you can spray with an organic control for chewing insects recommended by your local garden center, such as Bt or Spinosad. Bt is a contact only control and Spinosad has a 7-10 day residual but spray Spinosad in the early evening after the bees have returned to their hives. Once dry it is safe for beneficials. However, the most benign control is pick and squish. Also look for slime trails to see if the damage is due to slugs/snails, but we think it is likely a chewing insect.