Bombs for Butterflies

Bay Journal, Rare butterflies find refuge thanks to explosions at Pennsylvania training base

t’s the most unlikely of after-effects: Bombing, exploding grenades, artillery fire and dirt-churning tank maneuvers at Pennsylvania’s Fort Indiantown Gap have produced grassland habitat that’s ideal for the last notable population of beautiful and rare regal fritillary butterflies in the Eastern U.S.
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Lucky visitors get to walk among the butterflies that have been described as “monarchs dipped in chocolate.” Their forewings are bright red-orange, similar to monarchs. But their hindwings are darker, and the undersides of the hindwings are black with a striking array of white spots.

Regal fritillaries are vanishing or declining in much of their range. And Fort Indiantown Gap is the only place in the Eastern U.S. where you are likely to see them.

The undulating fields on a former farm are a medley of grasses and wildflowers that thrive on fires and newly disturbed earth. The 17,000-acre base includes five of these fields, totaling about 250 acres spread over 7 miles, that are intensely managed to coddle regals. But the butterflies also heavily use another 2,000 or so acres of training and firing ranges that are constantly pulverized and occasionally catch fire and burn.

“It actually gets a little beat up. What we don’t want is for the field to turn into a bunch of trees,” Swartz said.

These early successional fields harbor the plants, flowers and grasses needed by regals in their three growth phases. The caterpillars feed on arrowhead violets and other plants. In winter, when the caterpillars are still only the size of a grain of rice, they hunker down in welcoming microclimates provided by a variety of grasses such as little bluestem. Adult butterflies need nectar plants such as field thistle, milkweed and bee balm to survive.

Regal fritillaries are listed as critically imperiled in Pennsylvania, and the U.S. Fish and Wildlife Service is soon expected to announce its decision on a petition by scientists to declare eastern fritillaries threatened or endangered and thus get federal protection.

Sightings of regals at the site go back to 1958, when a famous moth field guide author was stationed there. But it was not until the Pennsylvania Department of Conservation and Natural Resources did a flora survey in the 1990s that the rare species became more widely known to scientists.

That observation led to a federal environmental impact statement and the adoption of a conservation plan to protect the butterflies at the fort. When the military proposed a new firing range in regal habitat in the mid-1990s, the North American Butterfly Association filed a lawsuit to stop it.

As a result, more formal conservation and protection protocols were drawn up, including a staff of wildlife biologists who are now stationed at the base for ongoing studies and to doctor habitat that regals find ideal. Invasive plants are pulled out by hand.

Prescribed burns are also part of the regimen. Usually, they are set intentionally, though live ammunition triggers others. Fortunately, adult regals fly away and caterpillars seem to survive, though Swartz said scientists aren’t sure how.

We have at least two fritillaries in our area, the Great Spangled Fritillary, the Variegated Fritillary, and the possibility to two more, the Gulf and Meadow Fritillaries. For what it's worth, it's not all that clear to me  what distinguishes fritillaries from other butterflies, but there are strong similarities in the patterns of the species called fritillaries.