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Northern Virginia’s final stretch of warm, sunny weather is bringing butterflies into view, including monarchs beginning their remarkable journey south.
The orange-and-black travelers pass through the region on their way to the mountains of central Mexico, where as many as 100 million monarchs spend the winter clustered on oyamel fir trees at elevations of 9,000 to 11,000 feet.
A monarch weighs about 598 milligrams—roughly one-fifth as much as a penny—yet some fly 2,000 miles from Canada to their wintering grounds. It is the only butterfly known to make a two-way migration.
In spring, monarchs mate and start moving north. Females lay eggs that develop into adults, and successive generations continue the journey, mating and advancing northward along the way.
Larry Meade, who leads local surveys for the North American Butterfly Association, said the eastern monarch population appears stronger this year than during the previous two years. He attributed the improvement largely to the absence of drought conditions that can damage milkweed and the nectar-producing plants monarchs need.
Meade is scheduled to lead another local survey Sept. 13.
A busy morning at Dyke Marsh
During an Aug. 30 walk at Dyke Marsh Wildlife Preserve, participants counted 15 butterfly species, five dragonfly species and two damselfly species.
Most eyes were trained on vegetation, but one of the day’s memorable discoveries appeared on a concrete curb: a plump, fuzzy luna moth caterpillar measuring three to four inches long. Adult luna moths, among North America’s largest moths, have wingspans of three to four inches.
More than 100 butterfly species have been recorded in Northern Virginia, according to Meade. About 120 species occur across the U.S. mid-Atlantic region.
Butterflies occupy many habitats but are especially noticeable around flowering plants, grasses, trees and wildflowers. At Dyke Marsh, numerous sachems fed on purple ironweed blossoms.
Meade also pointed out common buckeyes, recognizable by the large eye spots along the edges of their wings. Two red-spotted purples appeared to be competing for mates, while yellow-and-black eastern tiger swallowtails drew attention nearby. Female tiger swallowtails occur in two forms: some resemble the yellow males, while others have black wings.
Butterfly losses raise concern
The lively sightings come amid evidence of a steep national decline. More than one-fifth of U.S. butterflies disappeared between 2000 and 2020, according to a Xerces Society report released in June.
The study found that more than 40% of the species assessed had declined by at least half. Two dozen species suffered losses exceeding 90%. Researchers cited pesticide use, habitat destruction and climate change as major causes.
Although adult butterflies may drink nectar from several sources, many species are highly selective about where they lay eggs. Monarchs rely on milkweed, while other insects depend on their own specific host plants for egg shelter and food during the larval and caterpillar stages.
The Xerces Society’s recovery recommendations call for planting host species for caterpillars and maintaining nectar-producing flowers for adult butterflies across the entire growing season. The organization also urges people to avoid pesticides and protect overwintering habitat.
Even a small planting can help. Butterfly-friendly habitat can range from a window box to a field covering several acres, with milkweed and other native nectar plants offering vital food and breeding sites.
Larger efforts are also underway. The Virginia Department of Transportation maintains a wildflower and pollinator habitat program and has installed pollinator-friendly plants at facilities including the Interstate 95 rest area in Dale City.