WELCOME BACK

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The monarch butterfly is winging its way back to the Midwest after experiencing a rough winter. The monarch, our state insect, is not in danger of extinction, but Illinois environmentalists will monitor the population closely after thousands were killed by a snowstorm in the Sierra Madre.

by Michael R. Jeffords

Bright orange and black monarchs should begin reappearing this month in our fields and backyards. For the most part, they won't be the same butterflies that left the previous fall, but their children, returning to complete an age-old cycle. Still, a few tattered, faded individuals may make it all the way back from Mexico, their countenance somewhat dimmed by an unusually harsh snowstorm in their winter home. This summer, the butterfly counters will pay special attention to the monarch and to the more recent effects of a capricious Mother Nature.

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Long before states had official flowers, trees, grasses or insects, the monarch butterfly piqued human curiosity.

C.V. Riley, a pioneer entomologist, noted as early as 1878 that Midwestern populations of monarchs underwent birdlike migrations, heading north each spring and moving south each autumn. F.A. Urquhart, a monarch researcher for more than 40 years, later devised a butterfly tagging system involving thousands of collaborators and was able to confirm that monarchs generally moved in a southwesterly direction each autumn.

Where they went, however, remained a mystery until the winter of 1975, when two of Urquhart's associates discovered that monarchs from eastern North America overwinter south of the Tropic of Cancer in the mountains of central Mexico. The two located millions of nonreproducing monarchs at high altitudes resting on Oyamel fir trees (also called sacred fir). Their numbers were so great the branches sagged with their weight. Fir trunks were so densely clad with bright orange monarchs they mimicked the shingle-like scaling found on each individual's wings.

How these multimillions of monarchs traveled there each year and then returned north is perhaps the best-known feature of this remarkable creature, but it is not the entire story.

Read virtually any popular article or book about butterflies and the authors invariably use descriptors such as "gossamer-winged" or "fragile," "delicate," "lacy" or "ethereal" when referring to butterfly wings. Such adjectives are singularly inappropriate when applied to monarchs. They are tough little beasts.

Last fall I was returning from a field trip and whacked into a monarch at nearly 40 mph. It lodged under the windshield wiper of my car. The specimen seemed to be in good shape, so I extricated it from the wiper, as any good entomologist would, thinking to place it in the Natural History Survey's collection. I soon found, though, that it was not dead, only stunned. In a few minutes it recovered and was again winging its way south. Toughness would seem to be an appropriate characteristic for an insect that may travel as far as 2,000 miles to winter in Mexico, then return the following spring to the southern United States.

The story of migration really begins with the last generation of monarchs produced in the Midwest. In most Illinois summers, we have three generations or broods of monarchs, but the last one is unique as it does not reproduce. (We call that reproductive diapause.) When the cool days of September and October approach, monarchs begin to congregate and head in a generally southwesterly direction. As far as scientists know, they stop their flights as dusk approaches and form temporary clusters on trees or shrubs. These groups may break up the next morning or stay put for a few days, depending on the weather.

Although I was familiar with monarch butterflies as a child — the monarch is the first, and often only butterfly that children know by name — I did not experience true monarch migratory behavior until a few years ago. Illini Grove, a University of Illinois landmark planted by botanist Thomas Burrill in 1871, harbored a migratory assemblage for several days that October. (Several other sites in Urbana, mostly backyards, also played host to the welcome visitors.) Although the monarchs only numbered in the hundreds, or possibly a few thousand, I was impressed, even awed. I could only imagine what feelings the masses of monarchs must engender among the residents of their traditional overwintering havens of coastal California (for the monarch populations west of the Rockies) and central Mexico.

The monarch's life history, like all good stories about insect life cycles, begins with an egg. A female monarch is an excellent, if somewhat narrowly focused botanist and chooses only milkweeds on which to entrust her young. These common plants of Illinois roadsides, fields and prairies, also found throughout North America, are not so common chemically; most are laced with toxic compounds called cardenolides or heart poisons.

If eaten, these chemicals can cause irregular heartbeats, but have a somewhat more obvious effect on unsuspecting ingesters — they cause emesis or, less poetically, vomiting. Monarch caterpillars don't seem to mind the poisons, though, and even incorporate these chemicals into their bodies as a potent defense against predators. Even adults that emerge after five caterpillar molts and pupation, retain the toxins.

As any school child can tell you, both monarch caterpillars and adults advertise their distastefulness to the world. The caterpillars are colorfully banded with alternating white, yellow and black stripes, while the bright orange and black adult coloration is worthy of any highway traffic warning sign. Entomologists have a name for this — aposematic coloration.

Does this warning system work? Judge for yourself. In one study, a young blue jay that consumed a single monarch vomited nine times in less than 30 minutes. The next monarch it encounters, or anything remotely resembling one, will most likely be strictly off its menu. Other jays that were fed monarchs actually retched at the mere site of a monarch.

When autumn wind and weather conditions are favorable, the butterflies glide up on rising air currents and soar skyward. Glider pilots have observed monarchs as high as 4,000 feet above the ground. The journey can take 75 days, and individuals may average 30 miles per day to reach the high altitude forests of the Sierra Madre where they will spend the winter.

The journey gives new meaning to the words "genetic memory," for these individuals are three to five generations removed from the spring migrants who came north the previous year. This inherited behavior can be summarized quite simply: Migration is activated each autumn and spring; migration is repressed in winter and summer; and the direction of migration switches 180 degrees between autumn and spring (south in autumn, north in spring).

The monarchs are well-adapted to the Mexican montane forests. The cold allows them to lower their metabolic

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rates and activity from mid-November to mid-March while they rest quietly in the familiar dense clusters on the firs. They must conserve their fat reserves if they are to have enough energy for the return flight. Occasionally, large numbers of butterflies will fly off to drink water or fly above the canopy to cool off if direct sunlight should hit them for extended periods.

As the winter proceeds, mating frequency increases in preparation for the return home. After the spring equinox, monarchs return to Gulf Coast states and lay eggs on southern milkweeds to produce the first generation of new adults. These migrate northward, laying eggs as they go, as far as south as Canada. Up to three generations are produced in the upper Midwest, with two produced in the South. The final, nonreproducing generation, often the great-great-great-grandchildren of the spring migrants, must then make the long return flight.

This remarkable behavior alone could qualify the monarch as an insect any state could be proud of, and Illinois made its feelings official in 1975. Gov. Dan Walker, to the delight of Illinois schoolchildren, signed the legislation that designated the monarch as our state insect.

While the species is in little danger of extinction — Western populations are on an upswing and overwinter in protected coastal California areas while a resident population also occurs in Florida — the biological phenomenon that centers around eastern migration may be endangered.

Should we care? While each of us must find the answer to this question, several points are worthy of note. How monarchs navigate to distant locations that they have never visited is a mystery to scientists and one that merits study. On a more personal level, monarchs are a symbol of wildness, beauty and an ultimate freedom that is likely the envy of all of us. Should the monarch follow the passenger pigeon into the finality of extinction, we must all become significantly poorer.

How are they threatened? The story is the same as it is for most species:

Habitat destruction by humans is the culprit. Progressive deforestation is opening the Mexican forests and affording the overwintering monarchs less than ideal conditions for survival.

An increase in so-called "eco-tourism" may help to heighten awareness and may ultimately provide the revenue to preserve the endangered habitat of the overwintering monarchs. (Ironically — however ecologically sound the motives — an increase in visitors to the monarchs' winter home may also disturb the butterflies and deplete their fat reserves.)

Early this year, however, the monarchs weathered a more sudden and natural phenomenon; a rare snowstorm in Mexico may have killed as many as 15 percent to 35 percent of the monarchs. Many top scientists believe the snowstorm will have little impact on monarch populations in the long term. Nevertheless, all have adopted a wait-and-see attitude.

Previous data from annual 4th of July butterfly counts (the butterfly equivalent of the Christmas bird count) from 1977 to 1994 have shown that, while year-to-year fluctuations in monarch numbers occur, often coinciding with unusual weather events, monarch numbers appear to be relatively stable.

What does all this mean for Illinois' monarch population? This year monarch numbers may be somewhat down, but the species will have ample generations during this and succeeding springs and summers for populations to recover. Monarchs will, though, receive special attention from The Nature Conservancy's butterfly monitoring program this year and from volunteers who collect data.

With a little help from its friends, this most beloved of butterflies will continue to grace the Midwestern landscape — making its yearly epic journey from the backyards of Illinois to the boughs of ancient firs in the Mexican highlands then back again each succeeding spring.

Michael R. Jeffords is an entomologist at the Illinois Natural History Survey, a division of the Illinois Department of Natural Resources. A free-lance writer and photographer, he is a co-author of Illinois Wilds, a collection of essays and photographs of 15 of Illinois' native habitats.

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