According to the author of Butterfly Gardening for the South, one of the host plants for white peacocks is"ruellia occidentalis" and "probably several other ruellias are used as well."

I planted our native petunias, R. carolinensis, in my garden and on various parts of the property, hoping that buckeyes (closely related to white peacocks) would use them, but they never have. They still only use Agalinis, which is just now getting some size on it. If you find any white peacock caterpillars on your ruellia, I'd love to see a picture!

Sherry