Monarch butterflies will only lay their eggs on milkweed, and monarch caterpillars will only eat milkweed, because they need that toxin to actually create what they are as a species.
As borboletas-monarcas só põem os ovos nas asclépias, e as lagartas monarcas só comem asclépias, porque precisam dessa toxina para criar o que são enquanto espécie.