If any insect can be called iconic, it is the monarch butterfly. The butterflies, with their large orange and black wings, are easily one of the most recognizable insect species in the United States, and they have been a familiar sight around much the country for generations. But the monarch butterfly is now threatened like never before. Over the last 25 years, nearly one billion butterflies have disappeared, a population decrease of over 90 percent. There are only about 30 million monarch butterflies left, and they are now at the center of $3.2 million restoration effort and may soon be listed as a threatened species under the Endangered Species Act. How did we get here?

It is amazing that caterpillars turn into butterflies, and it is even more amazing to understand how caterpillars turn into butterflies. The caterpillar to butterfly metamorphosis is one of the great wonders of nature, so below we explain exactly how a caterpillar turns into a butterfly, going through several stages called ‘instars’, as well as situate this transformation in the larger life cycle of butterflies.