Meet the Karner Blue, A Rare Butterfly on the Rebound

karner blue
S.H. LeeNovelist Vladimir Nabokov, best known for “Lolita,” was the first to identify the Karner blue butterfly.

If you’re in the right place at the right time this summer, an endangered species the size of a postage stamp may flit past you in a flash of blue wings and gray underside. Karner blue butterflies, named after a town in the Capital District region of New York where they were first discovered, have a wingspan of only 1 inch but reward observers with their outsize charm.

“I’m always super-happy to see them each spring,” says Kathleen O’Brien, a wildlife biologist with the New York State Department of Environmental Conservation who has focused on protecting Karner blue butterflies since 1994. Two generations of Karner blues complete their life cycles each year, with the first brood hatching in April or May and flying into June, and the second hatching in late June or early July and flying into August. Thanks to the work of O’Brien and others, the size of those broods is growing.

The tiny butterflies—which live in parts of southern New Hampshire and Great Lakes states, such as Michigan and Wisconsin, in addition to New York—were first identified and described by Vladimir Nabokov, a skilled lepidopterist better known for writing the novel Lolita.

Picky Eaters
Karner blue caterpillars eat only wild blue lupine, which thrives in dry, sandy soils and partially shaded areas; think oak savanna and pine barrens. Unfortunately for very hungry caterpillars, development and fire suppression have constricted these habitats. Without natural fires or artificial management, shrubs and trees crowd out lupine and other plants categorized as early successional ecosystems.

O’Brien and others working to preserve Karner blue populations focus on habitat: cutting down trees in managed areas, pulling stumps to make mowing easier, and scraping the ground to bare sand before planting lupine seeds. In lupine-friendly areas, such as the Albany Pine Bush, a large inland pine barrens between Albany and Schenectady, N.Y., prescribed burns help maintain habitat.

Interstate Trade
Preservation efforts don’t stop there. When New Hampshire, which named Karner blues the state butterfly in 1992, could no longer find the species within its borders, New York came to the rescue. In 2000, New York officials started sending Karner blue eggs to be tended at a New Hampshire facility. When the blues emerged from their chrysalises as butterflies, they were released. That reintroduction has led to a stable Concord-area population of about 3,000.

These days, New York sends about 25 female butterflies to New Hampshire each summer, receiving hundreds of pupae in return the following spring. Once they emerge as adults, these next-generation Karner blues are released together in New York in a process called accelerated colonization, which increases their chances of finding mates and reproducing.

Safety in Numbers
Although the Karner blue remains endangered (listed in New York in 1977 and nationally in 1992), its population seems to be on the rebound, thanks to management efforts. In 2007, the first brood in the Albany Pine Bush was estimated at 700 and the second at 850. By 2015, the first brood numbered about 14,600 butterflies and the second 18,700.

Those numbers dipped somewhat in 2016, probably due to a warm winter, O’Brien says. Still, the population for the Albany Pine Bush is considered self-sustaining at 3,000, although O’Brien prefers to see many more: “So you feel comfortable that, in a bad year, they won’t all disappear.”

The protection of lupine habitat has also aided the frosted elfin (threatened in New York and endangered in New Hampshire) and the Persius duskywing (endangered in New York). They, too, eat lupine as caterpillars, though not exclusively. “Whole fleets of things that depend on this habitat have become rare,” O’Brien says. “The work to help Karner blues has helped them too.”


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Heather Stephenson

AMC Outdoors, the magazine of the Appalachian Mountain Club, inspires readers to get outside and get engaged. Learn more.