Mellie , sorry to hear about your larvae cat dying . At least you gave it a chance , Hopefully all the others will live, grow, and pupate delightfully
As far as purple Coneflowers , don't take this wrong but ,, I have a ground hog that agrees with you , It is eating all my flowers except the purple coneflowers , it can eat syrica milkweed ,
In the Butterfly garden if a plant is not chewed up I feel like a failure
it can eat syrica milkweed , 
