Most of the toxin concentarates in the butterflies' wings possible so as not to interfere with the butterfly lifecycle. Don't eat me. The bird in the poem above you would become ill and discomforted about 20 minutes after eating the butterfly and would vomit the monarch. This one experience would teach the bird never to eat monarchs again. In the animal kingdom, a butterfly called the viceroy began to mimic the coloring of the monarch.
Predators avoid the viceroy because they believe it is poisonous.
As the butterflies evolved, natural selection sustained the lives of the colored viceroys and they evolved to look almost exactly like monarchs. This is called Batesian mimicry. The second kind of mimicry is classified as Mullerian. Both the monarch and the milkweed bug have the same bright coloring. They also share the same kind of poison that originates in the milkweed plant.