As the summer wanes, the butterflies emerge

Nature: The tiger swallowtails' season is here, generating interest and fascination over the insects.

August 11, 1999|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

Fluttering over your garden or impaled on your windshield wiper, those big, black-and-yellow butterflies seem to be everywhere in Maryland these days.

Entomologists say the lovely bugs are most likely tiger swallowtails.

"From the last week of July into August, it really becomes common, and they're so beautiful it's hard not to notice," says Robert Robbins, chairman of entomology at the Smithsonian Institution's National Museum of Natural History.

The 4- to 5-inch swallowtails, flashing patches of orange and blue near their tails, have emerged in recent weeks in their winged adult phase. Now they're busy feeding on flower nectar and searching for mates.

"That's what it's all about for them," says John A. Davidson, entomology professor emeritus at the University of Maryland, College Park.

"The male bumps into a female, and you can see them go 'round and 'round in the air. It's a dance in the air, the courting flight," he says. Once they've mated, the females go to find a host plant to lay their eggs on -- mostly tulip poplars and wild cherry trees.

"That's why we have so many of them [swallowtails]; there is wild cherry in all the hedgerows," Davidson says.

No hard scientific evidence has been reported of a swallowtail (Papilio glaucus) boom in Maryland or anywhere in their eastern range from Ontario to Florida. But if their populations are up here, several factors -- natural and manmade -- could be at work.

"We had a really mild winter, and sometimes that will favor some things," Davidson says. Unlike the monarch butterflies, which migrate south for the winter, the swallowtails spend the winter here in their pupal stage, attached to plants in weather-hardened cases called chrysalises. A winter with extended bitter cold might kill some.

It's also possible that the hot, dry summer has reduced populations of the swallowtails' insect predators, allowing more butterflies to mature.

"But I don't think we really know," Davidson says.

Robbins suspects the answer might lie less in Mother Nature, and more in human nature.

"People are beginning to notice butterflies more than they used to," he says.

Butterflies just seem to be "in."

More than 2,800 people have joined the North American Butterfly Association since its founding in 1992, and more people than ever turned out this year for the group's annual July 4 butterfly count.

New field guides are being published all the time, Robbins says, and optics manufacturers are marketing binoculars and cameras specially designed for butterfly observations.

Growers are even raising them in captivity to release at weddings. Environmentalists discourage the practice, however, fearing that, among other things, it could spread diseases to wild populations.

Stevanne Auerbach, director of San Francisco-based Butterfly Lovers International, says people are nurturing wild butterflies, hummingbirds and other backyard denizens because they're concerned about the environment.

"We hear so much about global issues we can't do anything about. But if we can attract birds and butterflies, it brings people in touch with the very primal issue of the survival of our planet," she says.

Homeowners are augmenting their gardens with plants and shrubs whose nectar-rich flowers attract the insects. One of the most popular at Maryland nurseries is the buddleia, or "butterfly bush."

"They're in full bloom now, and they're incredible attractants for the tiger swallowtails," Robbins says.

"It's not impossible that, with the great emphasis on planting flowers that butterflies will nectar at, that we are increasing their numbers," Robbins says. "More likely, we are simply making their lives easier."

Next in line, after the swallowtails have laid their eggs and died, are the monarchs.

"We'll start seeing the monarchs flying through our area right about now, the very first ones," Robbins says. The southward migration lasts into October, as the black and orange beauties head toward their wintering grounds in the mountains of central Mexico.

"Most years," he says, "if you sit out on the national Mall, you can see the monarchs flying over. They're really that common."

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