Same problem here too. I have 2 tiny plants that survived but it's not enough to feed them for very long. So far they are eating the stems and dead leaves. I'm just going to let nature do its thing so hopefully the small surviving plants will get a chance to grow a bit beforr any more catapillars come along.
This isn't of much help now, but for future reference, the native purple passion vines and also coral honeysuckle are great food for caterpillars too, but you have to have an area to let it grow and climb. My honeysuckle is fine, but the passion vine is burned from the cold.
@Lillybean, I have monarch butterfly caterpillars.
@Cajunmom: Oh nice! I do not have any milkweed, so that's probably why do not have any of those The fritillary caterpillars love the passion vine and come around every year, but they arrive much later than the monarch caterpillars.