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D4027-1headline bar  A monarch butterfly feeds on a sunflower**Image Number D4027-1** A monarch butterfly, *Danaus plexippus,* feeds on sunflower nectar. Monarchs are poisonous to their predators, such as birds, because as caterpillars they ingest large amounts of *Asclepias* plants, primarily milkweed, which contain steroids that act in heart-arresting ways. The steroids remain and are redistributed when a caterpillar turns into a butterfly.  Photo by Peggy Greb.  640 pixels wide: (D4027-1.jpg)   Please visit our Image Gallery.


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