Monarch Butterfly

The monarch butterfly, called scientifically Danaus plexippus, or “sleepy transformation” in reference to their ability to metamorphosize from a striped yellow, black and white caterpillar to an orange and black butterfly. Monarch butterflies were originally found in both North and South America, but they are now no longer found in South America. North American monarchs can be found in two groups: the western monarchs and the eastern monarchs. Smaller populations can be found in Hawaii, Portugal, Spain, Australia, and New Zealand. 

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Females lay their eggs individually on a milkweed plant, stuck on with homemade glue. Over 2-5 weeks, they will lay 300-500 eggs. The eggs hatch into caterpillars after a few days, and then focus on growing. They only eat milkweed, which is toxic, but monarchs have evolved to tolerate it and in result are poisonous to eat. Their black and orange distinctive coloring warns predators of this, which some other species of butterflies have used to their advantage by mimicking the pattern. In two weeks they spin chrysalis around themselves, entering the pupa stage, and a week or two later emerge as an adult monarch butterfly. Adults feed on nectar from many native plants including milkweed. They will only live a few weeks, except for the migratory generation born in the fall that will live up to 8 months. 

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 Monarch butterflies are famous for their migration, but not all monarchs migrate. Monarchs born in the spring and early summer don’t migrate, instead immediately reproducing. If they are born in the late summer or fall, they will migrate to escape the coming winter. Western monarchs lay their eggs in the warmer months west of the Rocky Mountains and before the winter migrate to southern California, while eastern monarchs breed in the Great Plains and Canada in the warmer months and in Central Mexico overwinter. Some may fly 3,000 miles.

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Once the eastern monarchs reach Mexico they wait out the winter in oyamel fir trees. After winter they begin flying north, but they will never get back to Canada. Instead they stop along the route and lay eggs, and their children will continue the journey. It may take 4-5 generations to actually get to Canada. Western monarchs, on the other hand, head to the coast of California to wait for winter to end. In spring they head back to various other western states. Monarchs make this long journey by using the sun as well as their own magnetic compass to navigate. They also have genetically efficient muscles that help them make such a long flight. Another fascinating feature of this butterfly is how they communicate. They talk using scents and by releasing chemicals, and their colors convey their poisonousness to predators.