Invertebrate geometer?

kw: puzzles, curiosity, geometry, flowers

I took this picture the morning of August 1, 2006. Our little Fall Phlox plant produces a flower or two daily; a bud is visible behind this chewed flower. Each afternoon, I see the new flower(s) in pristine beauty. The next morning, they are variously chewed.

This particular morning some fastidious creature—probably some kind of caterpillar—has eaten only the left half of each petal. The other flower, on the other side of the plant, was chewed in a similar pattern.

In the past, I've seen the ends of the petals removed, or two of the five completely eaten. A curious circumstance, this one!