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Flight plan.  The importance of butterflies



The last monarch butterfly of the season. We watched it flit across the meadow, a protein matchstick with wings. No, not wings, but gaudy flags, orange and black, semaphoring southward, Mexico bound. We stood in rapt contemplation until it disappeared beyond the brook. Adiós, amigo. Hasta la vista. See you next year, or rather your nieces and nephews of the next generations.

The monarchs arrive in our New England meadows in late spring and early summer. They mate and lay eggs on the leaves of milkweed, and milkweed only. The eggs hatch a few days later, and the larvae feed on milkweed leaves. The leaves contain poisons, but these seem not to bother the monarch caterpillars. They store up the toxins in their bodies, which deters birds from eating them. The yellow-white-and-black striped caterpillars molt a few times, then pupate. Inside the chrysalis the larva rearranges its molecules, maintaining the toxins. The caterpillar's six stumpy front feet are turned into the butterfly's slender legs. Four bright wings develop, as do reproductive organs. The caterpillar's chewing mouth parts become adapted for sucking. A few weeks later the adult butterfly bursts forth with its glorious flags and toxic flesh. Few birds are dumb enough to take a bite.

There may be three or four monarch broods in a summer. Then, in September or early October, the last generation of adults heads south. No one knew where they went until 1975, when Canadian zoologist Fred Urquhart discovered hoards of monarchs roosting in a few patches of mountainous forest in central Mexico. Adult butterflies from all over eastern North America congregate in these clumps of trees and rest through the winter, as thick as leaves. The migration of the monarchs is one of the epic journeys of the animal kingdom. They fly by day and rest by night, singly or in groups. Millions finally arrive in Mexico. We talked of this epic journey as we watched the last monarch of autumn drift out of the meadow, beyond the brook, sunward, southward, called by some mysterious inner voice to a clump of fir trees thousands of miles away. Why didn't earlier broods of summer hear the call? A seasonal trigger, certainly. A chill in the air. The waning sun. And then the voice, speaking a language whose words are chemical, compelling, irresistible: "Take wing. Follow me. Down along the spine of the Appalachians, across the flat croplands of the Gulf Coast, into the mountains of Mexico."

How do they do it? How does a butterfly that has never made the journey know when to depart and where to go? That tiny pinch of toxic flesh with bright postage-stamp wings? This much seems certain: The call, the map, the navigational skills were there in the egg, somehow encoded in the monarch's DNA. Not, of course, in the way maps and directions are stored in the memory of an automobile or airplane navigation system. It is far more subtle than that. What the DNA encodes for are proteins. The proteins are a language of chemical geometry that speaks through the monarch's nervous system: "Ven, sígueme! Come, follow me." No one knows how the language evolved, nor does anyone yet understand the vocabulary or syntax. A butterfly's DNA is more voluminous than our own, 40 times more voluminous! Most of the butterfly's DNA is probably junk—long strands of useless garble, the derelict residue of the butterfly's evolutionary history. Other parts code for the successive body designs of an insect that goes through metamorphosis. Somewhere in that encyclopedia of information is the invitation to a journey whose origin is lost in the depths of time.

The migration of the monarchs is just one of the many miracles of life that await explication by science. Make no mistake, someday the miracle will be unraveled, the DNA sequenced, the proteins decoded, the subtle environmental signals and their receptors mapped—if only the monarch survives long enough for its secrets to be exposed. Its survival, of course, is in jeopardy. Those patches of Mexican forest where the monarchs roost are threatened by logging. Only a few sanctuaries are protected, and those precariously. The noxious chemicals we put into the air and soil here at home don't help. Our milkweed meadows are giving way to suburban housing and commercial "parks." That we might willfully delete from the universe so wondrous a thing as the monarch migration is a possibility too sad to be reckoned. In The Magic Mountain, the novelist Thomas Mann defines life this way: "It was a secret and ardent stirring in the frozen chastity of the universal; it was a stolen and voluptuous impurity of sucking and secreting; an exhalation of carbonic gas and material impurities of mysterious origin and composition." Gushy, over-the-top prose, yes, but why not? Life is gushy and over-the-top. What could be more over-the-top than those clouds of colorful flyers, pumpkin and salmon and flame, beating their way from our northern meadows to havens of fir trees in Mexico?

A few years ago it was my privilege to visit the Mexican monarch sanctuaries. Getting there wasn't easy: a six-hour drive west from Mexico City over sometimes frightening mountain roads, with an overnight stay along the way in Zitácuaro. A mile-long climb by foot along a rugged trail deep in volcanic dust to 10,500 feet, then a drop into a canyon forested with firs. We had seen a hint of what we were looking for as we passed through the mountain village of Angangueo on our way to the refuge: hundreds of bright orange monarch butterflies dancing in the air, casting fluttering shadows on walls, faces, pavement. The villagers went about their business as if these angelic presences were the most normal thing in the world. But nothing could have prepared us for what we saw when we finally got to the tiny patch of forest where 20 million monarchs covered the trees. When, occasionally, sunlight flooded through a break in the clouds, the butterflies took flight in their billowing millions. If you listened carefully, you could hear the soft rush of their wings. As I watched, wide-eyed and dropped-jawed, it occurred to me that among this teeming mass of monarchs might be one of those we had watched the previous fall in New England meadows.

To certain people, these few patches of Mexican forest are merely stands of lucrative timber. Threatened by conspiracies of greedy landowners and corrupt politicians, they are what monarch expert Lincoln Brower calls the insect's "Achilles' heel." Not long after the discovery of the monarch roosting places, conservationists, led by Mexican poet Homero Aridjis, pressured the Mexican government into establishing small sanctuaries enclosing the principle areas of congregation and holding the logging interests at bay. But now the butterflies face another threat, and I was part of it as I scrambled under the fluttering trees with my camera: ecotourism. Today, growing numbers of sightseers troop through the forest to see one of the great wonders of the natural world. Can the refuges sustain such popularity?

As I made the long climb along the dusty trail that led to the clustered butterflies, I observed the other people who made the trek. A few were Yanqui tourists like myself, with our fanny packs, Vibram soles, expensive cameras and binoculars. But the great majority of folks along the trail were Mexican, and, as far as I could see, they were not the sort of affluent, middle-class sightseers you'd meet in Yellowstone or Yosemite. They were people of all ages—old men and women, children, and everyone between—apparently country people or city dwellers who had not yet abandoned country ways. Like the rest of us, they struggled along the steep trail, choking on dust.

I don't want to condescend or romanticize: It may be that these people were propelled toward the insects by the same combination of curiosity and wonder that motivates visitors to Old Faithful or the Grand Canyon. But I don't think so. The only place I have seen similar assemblies of trekkers—the very old and the very young making a difficult climb—is on the holy mountains of western Ireland on the annual days of religious pilgrimage. As we reached the tiny clump of trees festooned with butterflies as thick as jungle foliage, we Yanks buzzed about, snapping pics, taking notes, storing up impressions with which to later regale our friends back home. The Mexicans by and large sat silently in the forest, kids in laps, eyes somberly fixed on the massed monarchs. It was difficult to read their emotions, but I saw these same expressions 25 years ago among the traditional faithful on the summit of Ireland's Mount Brandon.

I can't prove this, but I believe that many of the Mexican visitors to the Chincua Monarch Sanctuary were driven by the same urge that might have led them on another weekend to the Virgin's shrine at Guadalupe: a sense of the holy. And further, I think that unless those of us with our Vibram soles and fanny packs can reclaim a sense of the holy, the monarchs don't have a chance. I don't mean to sound mystical. The "holy" thing I am talking about is not some supernatural intrusion into creaturedom. Whatever it might be, it resides in the ceaselessly spinning DNA and chemical machinery that causes a creeping caterpillar to rearrange its molecules into a winged angel, and sends the angel beating down across a continent to a patch of trees it has never seen before.

The philosopher William James said, "At bottom, the whole concern of religion is with the manner of our acceptance of the universe." What I think I saw on the faces of the Mexican visitors to the Chincua Sanctuary was a dignified and unquestioning acceptance, an understanding that what they saw was natural and right and utterly essential to the completeness of creation. The poet E. E. Cummings wrote of acceptance "for everything which is natural which is infinite which is yes."

Science and politics alone will not save the monarchs any more than they will save other threatened species and habitats, any more than they will save the northern milkweed meadows. What is required is something that we have by and large lost in the high-tech, high-velocity, virtual world of the developed countries: a deeply felt, unintellectualized, instinctive "yes"—that behind the gaudy delight of 20 million butterflies hanging on fir trees, there is a holy power of which we are a part, and from which we separate ourselves at our peril.

Chet Raymo is professor emeritus of physics at Stonehill College and science columnist for the Boston Globe. This essay is adapted from The Path: A One-mile Walk Through The Universe, to be published in April 2003 by Walker & Company. Published by arrangement with Walker & Company.

Photo by Gary Wayne Gilbert.

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