September 2010

The Monarch in Fall
By Alison Gillespie

As the long days of August wane and the golden days of September dawn, my kids and I will be hunting around in our little urban garden for monarchs. We see the butterflies all summer long, but it usually isn’t until late in the season that we begin to get the caterpillars, too. Someone usually spots one while they’re washing the dishes, probably because our kitchen window overlooks the tall stands of milkweed on that side of the house.

Although many people eschew the homeliness of milkweed, we welcomed this native plant into our yard when it sprouted. We like to think that maybe the monarchs that hatch there in August will be the ones that migrate southward, although unless we band them we will never really know for sure. Either way, we love the large white, black, and yellow caterpillars they host and the brown butterflies they become, too.

Monarchs have been insect superstars since the 1970s, when it was discovered that they participate in one of the most unique migration rituals ever witnessed.

It seems that most of the year, these interesting insects stay in one place, and live average butterfly lives that can last anywhere from 2 to 5 weeks. They drink nectar, flutter around in somewhat drunken-looking patterns, mate and lay eggs. New monarch caterpillars hatch and the cycle repeats about five times.

Then, toward the end of summer, the final batch emerges from their chrysalises and the butterflies begin to migrate southward, travelling hundreds or even thousands of miles to reach a winter roost location in the mountains of central Mexico. There, they gather by the millions in the branches of trees, trying to avoid the cold and wet weather that sometimes blows by. When winter is over, these same individual insects will then make their way back as they came, travelling northward into the US again.

Once in the southern US, many of them will stop, lay eggs, and die. The eggs hatch, and the new caterpillars will feast on milkweed, then transform into chrysalises. After they emerge, some will travel farther north. Some will even travel as far as Canada. Wherever they stop they will lay eggs and die and the whole summer cycle will begin again.

This entire chain of events has been called one of the greatest biological mysteries of the world. Very little is known about why the monarchs go through such an elaborate yearly routine. How do the ones that travel south know where to go? How do the ones that travel north know when to stop and lay eggs? Why do they always choose the same spot in Mexico’s transvolcanic mountain belt?

If you’d like to learn about this grand mystery with your kids, there are loads of great resources out to get you started.

Last spring we studied monarchs as a larger geographical study of the country of Mexico, where these insects carry a deep cultural significance. This year I think we will participate in a bit of scientific research; we’ll look for some who might be roosting near here and see if we can spot any as they migrate overhead.

For more info go to:

Monarch Watch
http://monarchwatch.org

Journey North
http://www.learner.org/jnorth/monarch/index.html

Ask a Biologist from Arizona State University
http://askabiologist.asu.edu/migration

To find out more about growing milkweed you can also visit Alison’s own blog:
http://whereyouareplanted.blogspot.com/2009/08/monarch-caterpillars-have-arrived-in.html


Alison Gillespie is a science writer and garden coach who specializes in helping people build wildlife gardens in and around DC. She lives, writes and homeschools her kids in Silver Spring. Her own blog about urban wildlife and environmental issues can be found at www.whereyouareplanted.blogspot.com.

Photo Credit: Karen VanDenBerge, photo available at http://www.creatingonline.com/


Share