A few weeks ago I was out scouting locations for a tracking class and I noticed these caterpillars. They really seemed to like this plant, as every plant like this I noticed in that area was demolished and had up to a couple of dozen of these caterpillars on each plant. Unfortunately the remnants of the plants were not familiar enough that I could figure out what kind of plant it was.
I tried to identify the caterpillar on cool identification site, but though it returned a result (Utetheisa bella) the pictures of that species look enough different from mine that I suspect they are not the same critter.
