The monarch, Danaus plexippus, is perhaps the best-known butterfly in North America. I got to study them up close this past autumn while painting out at Riverbend Ponds natural area. There were literally dozens of these well-traveled beauties fueling up on rabbitbrush bloom before heading south for the winter.
What do monarchs have to do with the concept of "warning"? Apparently their bright orange color and distinctive markings serve as a blinking neon sign to birds and other predators that says, "DON'T EAT ME. I'M HIGHLY POISONOUS!"
This warning is so effective that it was long theorized that the Monarch's look-alike, the Viceroy butterfly (Limenitis archippus) had adopted strikingly similar colors/patterns so they would be mistaken for a deadly Monarch and left alone. However it was recently discovered that the Viceroy is poisonous in its own right, and is now listed in textbooks as an example of Müllerian mimicry; i.e. organisms that happen to look like one another, but are both harmful.