Tom Pawlesh never fully appreciated the magnitude of the Monarch butterfly migration each fall until he happened to look up one day while sitting on the back patio of his Jefferson Hills home.

	Doreena Balestreire/Post-Gazette
	Tom Pawlesh of Jefferson Hills with a male Monarch butterfly that he tagged as part of Monarch Watch.

There, at tree top level, he spied a Monarch heading southwest. Pawlesh has always been a nature freak, "a naturalist with a camera," as he puts it, but as he and his wife, Marina, gazed upward, he was startled to see one Monarch after another follow the same southwestern path in the sky.

Later, he was again filled with wonder while at work as a pilot for US Airways. Sitting in the cockpit one day, waiting for passengers to board in Charlotte, he and another pilot marveled at the Monarchs flying above them.

"There they were, about one a minute, going over the Charlotte airport," he said.

With reddish-brown wings outlined in black, the Monarch is a hard butterfly to ignore -- at eye level. But the millions of Monarchs now heading to Mexico can be easy to miss, unless you look up.

There should be plenty to see for those who look in the next few weeks, as the fall migration over Pennsylvania reaches its peak.

"We're expecting a really good migration," said Chip Taylor, an entomologist at the University of Kansas who directs Monarch Watch, a network of volunteers, students and researchers who study the Monarch butterfly, Danaus plexippus. The population has rebounded strongly since January 2002, when a winter storm in central Mexico wiped out 70 to 80 percent of the overwintering Monarchs.

Doreena Balestreire/Post-Gazette
Tom Pawlesh releases a Monarch butterfly he has just tagged.

A dry fall can make the long migration difficult for the butterfly, but if wet conditions persist, the mountain tops of central Mexico should be thick with Monarchs by November.

This is a particularly busy time for members of Monarch Watch, including Pawlesh and his family, as volunteers across the country capture Monarchs, glue a round, numbered tag to the underside of the left wing, and release them to continue their migration.

It's the 12th year for the tagging program, which is helping scientists develop a better understanding of the Monarch population, where the butterflies originate and how successful they are in reaching their wintering grounds in Mexico.

A butterfly tagged by the Pawleshes in their backyard on Sept. 12, 2001, was recovered by Monarch Watch in Mexico's El Rosario Butterfly Sanctuary the next spring. It had travelled 1,869 miles.

		Walking and tagging Tom Pawlesh of Jefferson Hills will lead a Butterfly and Nature Weekend from Friday through Sunday at the Davis Hollow Outdoor Center in Moraine State Park. lon Saturday and Sunday, Pawlesh will discuss Monarchs and the Monarch Watch tagging program, including field work in which participants will capture and tag butterflies. The weekend program, which runs from 6 p.m. Friday through 1:30 p.m. Sunday, is sponsored by the North Country Trail Association and a limited number of overnight accommodations are available at the Davis Hollow center for $55. But anyone is welcome to drop in for any part of the program at no cost, Pawlesh said. Donations are accepted. Slide shows are scheduled at 8 p.m. Friday and 8 a.m. and 8 p.m. Saturday. Field work will be from 9 a.m. to noon and 1:30 to 4:30 p.m. Saturday and 9 a.m. to 1:30 p.m. Sunday. For more information, contact Bob Tait at the North Country Trail Field Office at 724-290-4141 or visit the Web site www.butleroutdoors.com People interested in participating in this year's Monarch Watch tagging still have time, but need to act quickly, said Chip Taylor, director of the program. The program has 300,000 tags to distribute and, as of last week, was down to its last 50,000. Those will all be gone by next week, he predicted. For more information, or to order tags, visit the Monarch Watch Web site, www.monarchwatch.org. -- Byron Spice

No other butterfly migrates quite like the Monarchs of North America and scientists have yet to figure out quite how the insect does it. The adult Monarchs now on the wing were laid as eggs in late July and early August. None of them have been to Mexico, yet somehow they find their way more than 1,800 miles and somehow manage to add a bit to their half-gram weight in the process.

Scientists only learned where the Monarchs were overwintering in 1975. East of the Rockies, the Monarchs fly to the mountains west of Mexico City; Monarchs west of the Rockies migrate to the California coast.

After spending the winter in the Mexican mountains, huddled together at night on tree trunks and branches, these same butterflies will make the return trip, snacking on milkweed as they go.

"It's a giant, latitudinal smorgasbord," said John Rawlins, head of invertebrate zoology at the Carnegie Museum of Natural History. Different subspecies of milkweed prosper at different latitudes, he noted, so the traveling butterflies will experience a variety of tastes as they go.

The milkweed diet makes Monarchs as unappetizing to eat as they are beautiful to look at. Other, tastier butterflies, such as the Viceroy and Queen, mimic the Monarch's coloration in hopes of discouraging predators.

Back in the north, the returning Monarchs will lay the eggs of a new generation. But unlike the long-lived migratory generation, these summer butterflies will live only a matter of weeks. All told, they manage to squeeze in four or five successively larger generations in the course of a summer, until they produce a final, long-lived migratory generation.

"It's a tropical bug with a lifeway that exploits frost-resistant milkweed," Rawlins said. Monarchs elsewhere, such as the Caribbean isle of Hispaniola where he is participating in a biodiversity survey, don't migrate this way, but rather move relatively small distances only as food supplies and weather conditions change. Many butterflies and other insects can survive cold winter weather and thus don't need to migrate.

"We're learning things all the time about this population and this migration," Taylor said. For instance, the migration is not as chaotic as scientists suspected it might be. Rather, it is highly predictable from year to year, with the peaks varying only by a matter of days, depending on the vagaries of weather. Beginning in Canada and the northern states, the butterflies move in a mounting wave across the country toward Texas and, ultimately, Mexico.

The migration is so precisely timed, Taylor said, that researchers suspect the butterflies take their migrating cues from the sun and its position in the sky, or the characteristics of its light, rather than on the weather.

"But," he added, "we're not sure about that."

One of the curiosities is that Monarchs from the eastern United States have a harder migration than those from the Midwest, with longitude appearing to play a greater role than the distance traveled. For every 300 Monarchs tagged in the East, the researchers recover one from the Mexico overwintering grounds, compared with three butterflies for every 300 tagged in the Midwest.

The researchers pay villagers $5 for each tagged Monarch they recover, usually by sifting through dead butterflies on the ground. It can take three or four hours to find one tagged butterfly, Taylor noted. Only about one in 20,000 butterflies in the Mexican butterfly sanctuaries, El Rosario and Sierra Chincua, have tags, so it's not profitable to shake trees or capture or kill butterflies in search of the tagged bugs.

Still, Monarch Watch manages to recover about 3 percent of all the tags, a larger recovery rate than any bird-tagging program, Taylor added.

Pawlesh, who will host a butterfly tagging and education program this weekend at Moraine State Park, took his family to visit El Rosario near the village of Angangueo in February 2000.

Being in the midst of millions of butterflies, clinging in bunches to tree trunks, their wings extended to gather the warmth of the sun, or swooping down into a shallow stream for water, was a remarkable experience, he said.

"You can hear all those wings flying around," he recalled. "It sounds like fall leaves, but it's just millions of butterflies."