Monarch Butterflies May Be Threatened in Their North American Range


At the end of each summer millions of monarch butterflies fly from eastern North America to a dozen small patches of forest in central Mexico where they spend the winter. In the spring the butterflies fly north moving into areas as their food plant, milkweed, comes back. In the summer an individual monarch butterfly lives one or two months. That means that the butterflies that fly to Mexico in the fall are as much as five generations removed from the animals that left Mexico the previous spring. How they get to Mexico when their great great grandparents were the most recent generation to make the trip is a long standing mystery. Recent work suggest that monarchs use the sun to orient and navigate.

Professor Lincoln Brower explained in the June 1994 Environmental Review the treat to monarch winter habitat in Mexico posed by increasing deforestation. A recent paper reports that most of the monarchs collected from over wintering sites in Mexico were born in the most intensively farmed parts of the U.S. Midwest. American-style intensive agriculture using new insecticides and herbicides and bio engineered seeds may well pose another threat to the eastern monarch migration.

We spoke with Chip Taylor, acting chair of the Department of Entomology at the University of Kansas, about monarch butterflies and conservation efforts on their behalf.

PDF IconDownload complete article in pdf: