Bert Gildart: Writer and Photographer

©Bert Gildart: Shenandoah National Park’s Big Meadow has always been the setting for grand activities, having once served as homelands for Native Americans and as one of the first CCC Boy Camps during the FDR administration. Today, exciting events are still occurring here, only this one representing a phenomenal adaptation from nature.

In short the event concerns the life cycle of the colorful monarch butterfly, which has its entire life cycle keyed to the well being of the milkweed plant, a species that proliferates in the open areas of Shenandoah. In other words, this member of the order Lepidoptera has chosen the milk weed as the perfect plant on which to perfect life. Here, it lays its eggs, where the tiny 1/8-inch size eggs emerge several days later as tiny caterpillars. Leaves of the milkweed then serve as sustenance for the caterpillar, which quickly grows.

Within several weeks caterpillars reach full size and soon transform to their pupa stage (known as the chrysalis). Finally, individuals metamorphosis into the incredibly gorgeous monarch butterfly — a species we all recognize by its radiant orange and black patterns.

DEPENDENT ON MILKWEED

Two other things are interesting about the relationship, and the first seems obvious: Why is the monarch keyed to this one plant species? The other interesting thing is less a question then a statement of timing – and that is that several of the events in the life cycle of this insect are occurring right now, meaning about the middle of October, at least here in Shenandoah.

Park Ranger Bob Kuhns put me onto this interesting sequence when I asked him several weeks ago about the soft cyst-like structure that seemed to be prevalent — and that many campers were brushing off from their belongings in apparent disgust. “It’s the chrysalis of the monarch,” said Bob, “and unfortunately many don’t realize that it will soon emerge into a beautiful butterfly. You’ll find most pupas on the milkweed, but as mature caterpillars they may crawl to other nearby structures just before they make this grand transformation.

“Just head on out into Big Meadow and you should find at least several of the stages.”

PERFECT SETTING

That’s precisely the way Janie and I spent the day yesterday. For hours, we wandered the beautiful meadow poking through the milkweed, discovering that not only did the monarch depend on the species but that a host of other species, such as the milkweed beetle, are also keyed to the species. As well, we also found the monarch caterpillar, but no chrysalis. Nevertheless, we had no doubt it depended almost exclusively on the milkweed and we had to wonder — why?

CLICK FOR LARGER IMAGE:  L to R:  Milkweed showing brown seeds and feathery “vectors” of dissimination”; Big Meadow in back ground with milkweed and milkweed bugs in forground; monarch caterpillar feeding on husk of milkweed.

The answer we learned from yet more conversation with our ranger friend Bob, and from reading and from people we met out in the fields of Big Meadow results from a phenomenal condition. Milkweed contains an abundance of a chemical known as cardiac glycoside, which includes the somewhat familiar drug known as digitalis. All of these drugs can produce sickness, often fatal, and most animals and most birds have learned to avoid the species.

WHY AVOID MONARCHS?

Somehow, through the eons of evolution, monarchs have adapted to the plant, but because they do eat the plant it means their bodies contain large amounts of cardiac glycosides. It further means that any bird that eats the monarch will become sick and may die. Most birds, however, have also learned to avoid butterflies with brilliant orange and black coloration, and so the monarch enjoys a relatively predation-free life.

At the moment, Janie and I have been finding lots of caterpillars, but few butterflies. That, however, is the stage of this magnificent species we’re hoping to see yet. In other words, we suspect caterpillars will soon be entering the chrysalis stage and then, in another week or two, be emerging as the magnificent and much heralded monarch butterfly.

We look forward to this magical time here during the autumn of Shenandoah National Park, which we continue to enjoy (see Old Rag).

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THIS TIME LAST YEAR:

Magnificent Moose

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This entry was posted on Monday, October 11th, 2010 at 8:53 am and is filed under National Lands, Natural History/Conservation, Photography, Travel. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.