This is why I garden with native plants using organic principles. These are American Lady (Vanessa virginiensis) caterpillars, hosting on perennial Plantain-leaved Pussytoes (Antennaria plantaginifolia). I have two large populations of this plant (as well as some scattered volunteers), the smaller in a great deal of sun, the larger in some shade. I noticed numerous caterpillars on the smaller patch which had been pretty much decimated, so I carefully moved the larvae I could find to the larger patch ten days ago and they made the transition just fine.
This morning we checked this patch again (I had found some additional caterpillars on the smaller patch in the interim and had moved those as well) and could not readily find any caterpillars, although the plants showed evidence of a lot of caterpillar "chew". It's likely many of the caterpillars I initially moved ago have now pupated in various locations in or near the patch of host plants. Within seven to ten days, we should have the next generation of butterflies and the process will begin again, with the females laying eggs within five to seven days of eclosing (emerging from their chryasalids) on their preferred host plants. Meanwhile, I'll carefully tend the patches of host plants so there will be sufficient food for the next generation.
American Lady caterpillars are less "tidy" than some species. When they're rather small (the caterpillar at top right in the photo at left is probably fourth instar, or the fourth larval phase; caterpillars pupate after they reach fifth instar), they manufacture webbing to create leaf "cocoons" to protect themselves from predation. As the
larvae become larger, they cease doing this, as their larger size and their proportionately larger "bristles" make them less palatable for birds to consume. (This does not mean they can't be affected by other predators, including parasitic wasps.)
Other native host plants include other Pussytoes species, including A. neglecta, or Field Pussytoes, annual Sweet Everlasting (Pseudognaphalium obtusifolium) and perennial Pearly Everlasting (Anaphalis margaritacea), as well as other Pussytoes species, including Field Pussytoes (Antennaria neglecta). They adults nectar on numerous species, including pink Prairie or Downy Phlox (Phlox pilosa). The two photos of the nectaring butterfly were taken by my friend Don Schulte of Notable Greetings.