What leaves are poisonous to caterpillars?

Certain leaves contain compounds that are toxic to caterpillars, including those from plants like milkweed, foxglove, and some species of nightshade. Milkweed, in particular, contains cardiac glycosides, which can be harmful or even lethal to many caterpillar species. However, some caterpillars, like those of the monarch butterfly, have adapted to feed on these toxic plants, gaining protection from predators. Other poisonous plants can deter caterpillars from feeding, impacting their growth and survival.