Butterflies have evolved in remarkable ways that help them avoid being eaten by birds, lizards, and other predators.
We think of butterfly wings as being colorful, but many are relatively drab on the underside. Some butterflies protect themselves through camouflage--by folding up their wings, they reveal the undersides and blend in with their surroundings. Through this strategy, known as crypsis, they become nearly invisible to predators.
Bright colors and distinctive wing patterns can, however, be advantageous. The caterpillars of many species feed on toxic plants, and throughout their lives, their tissues are poisonous to predators. The adult butterflies make no attempt to hide themselves; instead, their bright, warning coloration is like a neon sign. A bird that eats one of these toxic butterflies remembers the experience--and avoids repeating it.
Some butterflies simply fool their predators. As caterpillars, they feed on nontoxic plants, and when they become adult butterflies, they are perfectly good food. However, they have evolved wing colors and patterns that look almost exactly like those of the toxic species--a phenomenon called mimicry. Birds and lizards, who have learned to avoid bold warning coloration, leave these imitators alone.