THE VIRGINIAN-PILOT
Copyright (c) 1996, Landmark Communications, Inc.
DATE: Monday, October 14, 1996 TAG: 9610120058
SECTION: DAILY BREAK PAGE: E1 EDITION: FINAL
SOURCE: BY MARY REID BARROW, STAFF WRITER
LENGTH: 102 lines
A HANDFUL of scrub pines cling to the windswept tip of the Eastern Shore near the Chesapeake Bay-Bridge Tunnel.
The bent and gnarled trees are the final stop for monarch butterflies before they make the arduous Bay crossing to Virginia Beach on their fall migration to Mexico. Their wings folded in repose, the monarchs hang like Christmas ornaments as they rest for the night or ride out bad weather.
This time of year you can find some of the creatures suspended in the needles on any given day, said Richard R. Mills, who teaches biology at Virginia Commonwealth University in Richmond and is involved in a national tagging program to track the monarchs' migrations.
``If you're lucky and it's cold enough, you might see thousands of them,'' Mills said. ``They come back to the same trees every year.''
This year, to gain further understanding of the butterflies' phenomenal journey, Mills and some of his graduate and undergraduate students are participating in Monarch Watch, a national tagging program.
Monarchs are the only true migrating butterfly. It is possible that some monarchs actually make the trek all the way from Canada to the Mexican mountains where they spend the winter hibernating, suspended from the fir tree needles, and then make the return trip, Mills said. Most mate and lay eggs along the way leaving the next generation to complete the round trip.
Migrating songbirds and hawks funnel down the Eastern Shore and congregate at Wise Point to wait for the right wind currents to cross the Bay. Monarchs do the same thing.
``Sometimes they spread their wings at a 90-degree angle,'' Mills said, ``and just let the wind blow them across.''
They gather at the Chesapeake Bay-Bridge Tunnel, not because it is a guide across the Bay, Mills noted, but because it also follows the shortest route to the other side.
Although seemingly delicate in every way, from their ornate orange and black wings to their minute black and white bodies, monarchs are tough. Black veins in their orange wings serve as strong struts that reinforce the fragile wings for a grueling migration.
The butterflies also are tough enough to be handled by Mills and his students who recently went down to Wise Point to spend an afternoon tagging some of the gathering. A butterfly net swished just once over the pine branches yielded a number of monarchs to be tagged.
As one person would hold a tiny insect with its wings folded, another would use acrylic glue to attach a square of thin plastic on the underwing, tapping it slightly with the eraser end of a pencil. Each butterfly would be held for a few moments longer to let the glue dry.
When released, the creatures appeared to be on autopilot, returning immediately to the scrub pines and hanging there, their new tags highly visible on folded wings. Each tag has a number and instructions for writing a University of Kansas professor with details of when and where the tag was found.
Mills, who has a doctorate in entomology, has been studying monarchs in the laboratory as well as for 15 years from his summer home on the Eastern Shore. He has observed that the monarch's major migration is down the bayside along the beach, the critters flying singly about 5 feet off the ground. One in 15 will stop for goldenrod nectar, the monarch's prime food during migration.
Scientists don't know much about what allows generations of monarchs to make the same migration down the Eastern Shore and on to Mexico, beyond thinking the antennae has some magnetic sense.
Since most butterflies don't live to make the round trip, much less the return the following year, the same butterfly never roosts in the scrub pines along Route 13 at Wise Point either. Biologists surmise that previous generations have left behind an odor on the pines, that draws the newcomers to the roosting spot.
``It's probably chemical,'' Mills said, ``such a small amount of it, we would have a hard time identifying it.''
Although tough, monarchs cannot survive freezing weather. Their migration through this area can go as late as the end of November but they must make it to Mexico before freezing weather sets in along the way.
In more tropical Mexico, temperatures in the mountains drop low enough to slow the butterflies' metabolism for hibernation, but not below freezing, which would kill them.
``They live off their stored resources until they come back off the mountain in March,'' Mills explained, ``and go to Texas and Louisiana.''
In Texas and Louisiana, most monarchs breed and lay eggs and leave the migration back east and north to the next generation. Biologists know this because the monarch caterpillar feeds on milkweed plants, and milkweeds from different parts of the country have different chemical imprints that linger in the adult butterfly.
Now, tagging also may help biologists learn more about where the butterflies go when they migrate. For example, they think that some migrate directly to Mexico whereas others go all the way around the tip of Florida, even stopping off in Cuba and the Dominican Republic, Mills said. The chance of tag return is slim, he said, but just one tag can indicate a migration route.
Although found tags are to be reported to the University of Kansas, Mills is interested in hearing from anyone who finds tags applied by him and his students. Those numbers range from DT281 to DT300 and from HB080 to HB461.
Send a post card to him at the Biology Department, Room 202, Virginia Commonwealth University, 816 Park Ave., Richmond, VA 23284. ILLUSTRATION: MARY REID BARROW
The Virginian-Pilot
[Color Photo]
VCU students are helping out this year in Monarch Watch, a national
program to tag and track monarch butterflies. by CNB