October 2015 Biodiversity Spotlight

Monarch Butterfly Danaus plexippus

Photo courtesy of Court Whelan


For many, Monarch Butterflies are a sign of fall as they make their journey south to overwinter.  Monarch Butterflies are easy to recognize with their bright orange wings outlined in black. Their larval stage and chrysalis are also eye-catching:  Caterpillars are striped with white, black, and yellow, and their chrysalis’ are mint green with gold spots.


This year marked the 40th anniversary of the discovery of the Monarch’s largest wintering site in the Transvolcanic Mountains of Mexico.  The majority of Monarch Butterflies embark on this migration to Mexico every year with some populations overwintering in California and Florida.  It takes approximately four generations of Monarchs to complete the entire journey each year.  The cycle begins in February and March when overwintering Monarchs come out of their winter torpor, mate, and deposit eggs.  The next two generations of Monarchs only live two to six weeks. During that time, these generations mate, fly north, and deposit eggs.  Only the final generation in this cycle will migrate south.  Instinctively, these Monarchs know to travel south (although earlier generations flew north), and they will live six to eight months with some traveling over 1,000 miles to reach their overwintering sites.

Conservation status continues to be reviewed as their populations dwindle. Loss of habitat and extreme weather are the largest threats to the overwintering populations in Mexico.  In the United States, the decline of native milkweed (Asclepias), their host plant, has threatened breeding and larval success.

Milkweed illustration by Dale Johnson


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Additional Captions: The left image within the text was taken by Andrei Sourakov in Mexico. The right image was taken by Jillian Goodwin.The map was created by Paul Mirocha. Visit his blog post about Monarch migration and download a free milkweed poster.