The flowers produce abundant nectar that attracts various butterflies, including the monarch ("Danaus plexippus"). Until 2007, this butterfly was treated as a subspecies of "Danaus plexippus". The butterfly closely resembles the monarch butterfly ("Danaus plexippus") of the Americas. For example, monarch ("Danaus plexippus") caterpillars feed on milkweed species of varying toxicity. This plant, like many other milkweeds, hosts the monarch butterfly ("Danaus plexippus"). The monarch ("Danaus plexippus") is slightly larger, but is only a rare vagrant. Pine-oak forests in Coahuila are part of the migration route of monarch butterflies ("Danaus plexippus").