We needed military clearance to get in, but it was worth it. In a field of native little bluestem grasses, tucked between two ridges, several mature field thistles supported dozens of nectaring regal fritillary butterflies. Most were the larger, brighter, black and deep orange-colored females although we did spot a few dull-colored, worn-out males, as well as two other fritillaries–the great-spangled and aphrodite–Leonard’s skipper, and an orange sulphur butterfly.
My husband Bruce and I, accompanied by four biologists associated with the Pennsylvania chapter of The Nature Conservancy (TNC), spent a late August day at a military base in southcentral Pennsylvania visiting the last-remaining population of regal fritillary butterflies in Pennsylvania and “perhaps the only remaining viable population in eastern North America,” according to a preliminary research paper written by Roger Latham, the principal investigator for the project.
Oldtimers in Pennsylvania still remember seeing regal fritillaries in undisturbed meadow and wetland habitats. But one by one the colonies of regals winked out, not only in Pennsylvania but throughout eastern North America. Once the butterflies ranged in localized populations from southern New Brunswick in Canada to North Carolina. By the late 1950s, the northern colonies as far south as Massachusetts were mostly gone except for a few offshore islands in Massachusetts and Rhode Island. Those colonies too disappeared one by one, and in 1992 the last colony, on Block Island, died out.
By then the only known colony left in eastern North America was the one we were visiting. It had been discovered in the late 1980s. Because it is on a military base, several years of negotiations were necessary before TNC biologists, assisted by volunteers, could begin to monitor the population.
Today TNC manages three areas of regal fritillary butterflies totaling 165 acres and two comparison areas without fritillaries totaling 92 acres, under a Memorandum of Understanding (M.O.U.) with the Pennsylvania Department of Military and Veterans Affairs. They have an office on the base, and their work is funded by the National Guard Bureau though the Pennsylvania Army National Guard under a five-year cooperative agreement for TNC to assist in the base’s regal conservation program and provide other natural resource services.
“Our office wouldn’t be here without the funding of the military…some of the staff at the base have put forth a lot of effort toward the regal conservation program,” says Deanna Zercher, project manager of TNC’s regal fritillary habitat restoration and management study.
What does a military base have that the rest of eastern North America does not?
“Probably the largest area of upland native grassland in the mid-Appalachian region,” Latham writes in his research paper. “Soil disturbance and repeated fires…on land used for decades by various branches of the military as practice ranges for armored vehicles, artillery, and anti-tank attack bombers”…have produced…”a modern-day analog of habitat formerly maintained for thousands of years by native American burning and bison grazing and trampling.”
“The military,” Deanna Zercher told us, “is not geared to purposely changing the habitat like farmers are. They don’t plant exotic species so the natives remained.”
And native plants are what regal fritillaries seem to require. As larvae they feed on violet species. The Pennsylvania colony feeds almost exclusively on arrow-leaved violets, Viola sagittata, a native that grows only on highly disturbed sites. As adults they nectar most frequently on the native field thistle Cirsium discolor, butterfly milkweed Asclepias tuberosa, and common milkweed A. syriaca and hide and rest in the shade of low-growing bushy shrubs and grasses such as the field of little bluestem where we first saw them.
It was a perfect day for butterflies–warm, clear, and sunny. The spectacularly-colored females had just emerged from a three-week resting period or diapause after a hectic courtship. Soon they would be searching for places to lay their eggs. Usually the females drop to the ground and walk around depositing large numbers of eggs, one at a time, over a period of several weeks, on or near violet leaves. Although no one knows how many eggs a wild regal fritillary lays, researchers raising regal fritillaries in captivity had one female that laid 2450 eggs!
By late August and early September, when they lay their eggs, violet leaves are drying up so once the eggs hatch, in 10 to 14 days, the tiny caterpillars have nothing to eat. Instead, they search for shelter in the meadow duff where they rest until spring. Those that survive their long diapause begin feeding on the violet leaves as soon as they emerge from the soil in April. The caterpillars are black, white, orange, and red, seemingly bright enough to be easily spotted on the green leaves.
Not so, says research associate Pete Mooreside. It was his job to look for larvae in large patches of arrow-leaved violets. First he would search for nibbled violet leaves. Then he would try to spot movement.
“It was easiest for me to locate violets by slowly walking through fields. I’d often bend down to inspect violets or to search the immediate area surrounding a violet…after spending over 30 hours searching in this manner, I found six regal larvae.”
“It’s really tricky to see them because they are often resting, wrapped up in duff and warm season grasses,” he told us.
Despite finding so few larvae, they at least had an idea of where they fed, what they were eating, and when they were eating. Although most fritillary species, including regals, were thought to feed mostly at night, Mooreside found only one when he attempted a short night search. Another investigator, in Kansas, discovered that three out of 12 larvae fed during the day.
By the middle of May, the caterpillars have molted five times before pupating for six weeks. The males emerge first from their chrysalises at the end of June and nectar principally on common milkweed. The females emerge a week to ten days later. Then both sexes nectar on butterfly milkweed.
The females often rest in the shade at the base of shrubs and small trees where the males seek them out and mate with them. By the middle to the end of July the males start to die out. The females too disappear.
“They go into semi-hibernation, probably to conserve their energy reserves and to hide out from further harassment by the males,” says Latham.
After resting the first three weeks in August, the females emerge to begin again the life cycle of regal fritillary butterflies. Then, after laying their eggs, they die.
The Nature Conservancy biologists are eager to learn more about the life history and ecology of regal fritillary butterflies so they wil know how to properly manage habitat to save them from extinction. Although the Great Plains and Midwest have larger populations of regal fritillaries, they too are dwindling.
Here in Pennsylvania the regal fritillary butterfly is a state endangered species. To further complicate the matter, recent DNA studies by researcher Barry Williams indicate that the Pennsylvania regal fritillaries (and another smaller, recently-discovered population in Virginia) have several mutational differences from the Midwest and Great Plains populations. Williams estimates that our population has been separate from those further west for over 400,000 years.
Williams also found, by measuring the size of the spots on the underside of the wings in museum specimens, that the eastern regal fritillaries had smaller spots or none at all. In other words, the eastern regal fritillary is probably a distinct subspecies that should be protected under the Federal Endangered Species Act.
TNC biologists are trying to find habitat management methods that will save the eastern regal fritillary butterfly from extinction at the military base and that can be used to re-establish populations at other sites. Although their studies are preliminary, some of their more interesting findings are that “active regal habitat had significantly less total plant cover than nearby, similar habitat lacking regals” and that “violet densities were significantly higher in [an accidentally] burned area…total plant cover was significantly lower…and percentage of bare ground was significantly higher in the burned area.” In summary, “regal fritillary habitat differs from similar, nearby, unoccupied grasslands…in having nearly one-fifth less total plant cover and one-third less cover of plants other than grasses,” Latham writes in his research paper.
They have also been planting more common milkweed, butterfly milkweed, and field thistle in experimental plots and, with the help of volunteers, removing invasive plants such as mile-a-minute. To create more grasslands, they have been removing Virginia pines that have been taking over in some of their research plots.
On the day of our visit, they checked another experimental plot, one that had been scarified by an armored tank to see what would happen. There we found a few field thistles, a few regals, and a tiger swallowtail butterfly. Initial results of that experiment seemed to indicate that in the short run, there were less native grasses and more nonnative grasses in the area and that plant cover in general decreased to less than half of what had been there before. But this study, like the others, are long range studies that will take years to resolve.
There was no doubt that the first spot we had visited, with stony patches and “millions of violets,” as Deanna enthusiastically told us, as well as several mature field thistles in a sea of little bluestem, was the best site.
We had bumped over dirt roads for several miles to reach all the sites, and I was surprised at the peace and serenity of the place. I had expected to hear helicopters and planes and even shooting on a military base.
All the biologists were enthusiastic about their work and the site. Research assistant Pat McIlhenny, his binoculars slung around his neck, didn’t miss a bird or butterfly. Once he pointed out a red-headed woodpecker. He also told us they had found 71 species of butterflies on the base so far including the blackdash and frosted elfin.
“We’ve seen turkeys, black rat snakes and deer and signs of black bears, coyotes, and bobcats,” he said. There are also timber rattlesnakes, copperheads, and unexploded ordnances to look out for.
Still, the entire area is one of the largest, relatively-untouched wild areas in central Pennsylvania–17,000 acres including the adjacent Stony Creek (State Gamelands 211) and St. Anthony’s Wilderness, of which 165 acres are devoted to regal fritillary butterflies.
Will it be enough to save the eastern regal fritillary from extinction? With the continual cooperation of the military and the hard work and dedication of the biologists, it is difficult to believe that they will fail.