This caterpillar is a sly one as it's very hard to see on a quick pass. These guys are on a volunteer hesperis matronalis and I noticed the leaves were quickly getting defoliated. I had some seedling hesperis growing in pots that faced a similar phenomenon a couple months ago. All of them were quickly defoliated but I never noticed the culprit. Now I think I just wasn't looking hard enough. Anyone have any thoughts?
Looks like a caterpillar of the cabbage white butterfly (Pieris rapae); they will feed on many members of the cabbage family, which includes your plant.
http://www.fcps.edu/islandcreekes/ecology/cabbage_white.htm
Ok, that makes sense to me. Thanks for the id help.
