Wings of Silk, Will of Iron
Monarch butterflies, beautiful black-and-orange fluttering insects of the spring and summer, can be found throughout the world. North American monarchs are special, however, because they migrate incredible distances – up to 3,000 miles each way. Amazingly, they fly to the same wintering grounds year after year, even though each butterfly rarely lives longer than a few months. How do these tiny creatures know where they’re going? How do they avoid getting lost, especially in strong winds? Scientists are still trying to answer these questions. Here’s a list of some potential answers they’ve come up with.

What do you think? Monarch butterflies migrate thousands of miles to the same locations. How do they find their way? They use the position of the sun and an internal compass to guide them. They take cues from other migratory insects and birds, following them southward. They use sunset glow and star patterns. They sense chemicals in the air that are unique to the region. The correct answer is #1

Most of the time, monarch butterflies are loners. They flutter around bushes and sip nectar all by themselves. However, when winter approaches, more than 100 million monarchs gather together from all over the United States and Canada to travel southward. In the spring, they gather again for their northern migration. North American monarchs travel in two main geographic groups: Those east of the Rocky Mountains migrate primarily to Mexico, while those west of the Rockies generally spend their winters in coastal California. No one knows exactly how monarchs repeatedly find the same roosting sites, but scientists have several theories.

One theory is that the butterflies orient themselves by the sun’s position, which relates to their interpretation of the time of day. If a monarch’s “internal clock” indicates that it’s morning, for example, the butterfly will fly to the east. To test this theory, scientists collected monarchs and kept them in a controlled environment, exposing them to light at different times to shift their internal clocks. When the butterflies were released in the afternoon, they flew as if the sun were in the morning position. But monarchs are masters of navigation even on overcast days, so they must have other ways of finding the right direction. They may, in fact, have a kind of internal geomagnetic compass. In recent studies, monarch butterflies exposed to strong magnetic pulses showed signs of disorientation when released on overcast days.

It’s possible that monarchs also use landscape features as cues. They simply settle down for the winter on the first suitable hillside or tree they come to – which just might be the same hillside or tree that previous generations wintered upon. Monarch flocks alter their flying patterns once they reach the general area where they will winter, swooping low to find their ancestral roosts. We may never know for sure how these delicate creatures navigate, but their mysteries intrigue us; there is as much wonder in a monarch’s journey across a continent as there is in a flap of its colorful wing.

Fast Facts Just like humans, monarch butterflies rest at night. Spring and early-summer monarchs live 3-6 weeks, but latesummer and early-fall monarchs live 6-9 months and are the ones that make the long journey south. A migrating monarch travels 50-80 miles per day (4-6 miles per hour). Monarch larvae eat only milkweed. At their wintering sites, monarchs sleep in clusters hanging from trees. A monarch’s wingspan is only 3-4 inches, making the migration even more remarkable. Monarchs cannot fly at temperatures below 55 degrees Fahrenheit, and they cannot move at all below 40 degrees Fahrenheit.

Butterfly Links
Monarch Watch:
www.monarchwatch.org

The Why Files:
http://whyfiles.org/006migration/index.html

Journey North:
www.learner.org/jnorth/

Nature Works:
www.nhptv.org/natureworks/monarch.htm

Texas Monarch Watch:
www.tpwd.state.tx.us/nature/education/tracker/monarch/

Monarchs in the Classroom:
www.monarchlab.umn.edu/SO/so.html

USGS - Butterflies of North America:
www.npwrc.usgs.gov/resource/distr/lepid/bflyusa/bflyusa.htm