Does your screen porch have deck flooring, with spaces in between the boards? If so, they may very well go "underground" to pupate, because they usually like to pupate in a hidden spot. They may also be eaten, if they pupate in a spot exposed to insects or other predatory critters.
You don't happen to have a butterfly/reptarian cage do you? If it were me, I'd cut off the pieces of MW the individual cats are on and put them in plastic leftovers containers with water in it, and holes punched in the top for the stems or branches. Then they'll pupate inside the cage. Some pet stores sell these cages or you can order one online.
You could make one. Take a fairly big container, put paper towels on the bottom, put the leftovers containers (or other similar, water holding container) on the bottom, cover the top with bridal veil material, and secure the material with clothes pins. Change the food and paper towels as needed.
Good luck! Don't worry - que sera sera!
Sherry

Thanks you so much for your response. I have seen a container at a pet store that I have been thinking about using. Seems like I have seen some pics of them as other people's "houses" on other threads. So I should move them in their current state and continue to feed until they stop eating?

I certainly understand that nature can take care of itself and it did fine before me and will do just as well after. I think this is the same phenomenon that I used to tease my mom about when I was in college. When I was 5 hours away and she had no idea where I was or what I was doing, she never worried or lost sleep. I'd come home at breaks and she would know I went out with friends that she loved and she'd stay up until I came home. I could never understand why she worried more when she knew where I was but it must be something like this. These cats are under my wing(so to speak) and I feel a responsibility not to screw their lives up.

And something about being a mom makes one an expert at borrowing worry!

Thanks again!

Meredith