SEPTEMBER
2004

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

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Check out these books by Tom Turpin:

Flies in the face of fashion

What's Buggin You Now?

 

 

 

09-23-04

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Monarch Good Name for Aristocratic Butterfly


Insect common names sometimes reflect characteristics of the insect -- names like green Junebug or sulfur butterfly do just that. Other names, such as corn borer or stinkbug, say something about the behavior of the insect. Some insect names merely reflect human perceptions. The hercules beetle is a big, strong insect, and the luna moth has a moon-shaped marking on its wings.

We humans have even borrowed titles of nobility with which to dub insects. For instance, the viceroy and queen butterflies. There is a royal walnut moth. One of the most recognizable insects is the monarch butterfly. There is no name higher on the peerage scale than monarch!

Monarch is a good name for this brown butterfly with the black markings. The monarch isn't the largest butterfly in the world. It isn't even one of the prettiest. But the monarch is one of the most-loved insects in the world. The reason that the monarch butterfly is so adored by the human population is because it does something that few insects do. It migrates. Many insects move from place to place, and some manage to travel great distances. But few insects migrate.

Not only does the monarch butterfly migrate, it can cover as many as 2,000 miles in flights from Canada to the mountains of Mexico. In the animal world, movements of such distances are not uncommon. Many birds fly that many or more miles in their annual seasonal migrations. Whales move hundreds of miles from northern to southern hemisphere in their migrations. Salmon return to spawn in rivers after traveling great distances and maturing in the ocean.

But the monarch migrations are different from the other great animal migrations, and this is why we are so interested in the majestic butterfly. First, bird and mammal migrations involve individuals who have traversed the route before. New migrants have to learn the route. The salmon are returning to their place of birth, apparently using chemical clues in the water to find their way home.

Monarch butterflies that accumulate in the mountains of Mexico to spend the winter have never been there before. They are not going home. They have not learned the location from experienced travelers. But, somehow, the monarch just knows the way. Much to the delight of men everywhere, they don't even have to stop to ask directions!

The exact factors that the monarch uses to find the winter site is not known. As they say, "It's in the genes." The genetic code of the insect steers it unerringly to the place that hundreds of generations have gone before. It is one of the miracles of nature.

The miraculous journey by a fragile butterfly has endeared the insect to people everywhere. We worry when monarchs are now seen in the fall, floating southward over fields and garden. We wonder why the number of monarchs we see is less than last year or the year before.

Monarch butterfly populations are like other insect populations. Numbers of individuals can vary widely from year to year. There are several factors that influence monarch populations. Very important is the wintering success rate. An unusually cold winter in the mountains of Mexico can kill a high percentage of the individuals. When this happens, reduced numbers of monarchs begin the northern migration in the spring.

During the northern migration, weather can influence the reproductive success of the butterfly. Wet and cool weather, as we experienced over much of the Eastern United States this year, is not good for egg laying and survival of the newly hatched caterpillars.

Like all insects, the availability of food is essential to success. In the case of the monarch, it depends on plants generally known as milkweeds. These plants are considered weeds by most people and are eliminated in fields and roadsides, thus reducing caterpillar food for the monarch. As with other insects, there are predatory insects that feed on the young caterpillars. We humans also destroy countless numbers of butterflies with our trucks and automobiles.

It is indeed a tough life as a monarch, either the human or the insect type. This alone is reason enough to appreciate the sight of the beautiful monarch butterfly winging its way to a winter destination. Have a good trip, old chap!

 

 

Writer: Tom Turpin
Editor: Olivia Maddox