Hungry caterpillars, 2008 edition

I enjoyed my experience with the black swallowtails last year, so I decided to see if I could replicate my success with monarchs this year. Last month I purchased and planted a small milkweed plant in my garden expressly for this purpose.It looks like it worked:(click on any picture for a larger version)I don't know if these caterpillars are the offspring of butterflies passing through on the way