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August 26, 2011


New, state endangered butterfly documented on installation

The regal fritillary butterfly has been sighted at Fort McCoy.

Tim Wilder, endangered species biologist for Fort McCoy’s Natural Resources Branch (NRB), said that at first glance the butterfly resembles a monarch butterfly but is slightly smaller.
PHOTO: A male regal fritillary butterfly. Photo by John Polk
A male regal fritillary butterfly is among the butterflies being surveyed by the Fort McCoy Natural Resources Branch Endangered Species program. (Photo by John Polk)

NRB personnel are about halfway through a survey for the regal fritillary butterfly. The butterfly is listed as a state of Wisconsin endangered species and a federally listed species of concern, he said.

Regal fritillaries were first documented on Fort McCoy in 2010, when five were observed. To determine if this was just a fluke, surveys for regal fritillaries are being conducted in 2011.

“To date, more than 70 observations of the butterfly have been documented in numerous locations on the installation,” Wilder said.

Wilder said it isn’t clear how long the butterfly has been at Fort McCoy — if it recently found its way to Fort McCoy or has been here for a while.

The regal fritillary is part of a genus, which includes the Aphrodite fritillary and the great spangled fritillary. Both of those butterflies also are found at Fort McCoy, which can make it challenging to positively identify the regal fritillary.

Regal fritillary males tend to be slightly smaller than females and spend a considerable amount of time flying throughout their habitat area searching for females. Wilder said the females are more secretive, making them more difficult to observe.

The butterflies generally are found in an area of tall grass or prairie vegetation. Adults will nectar on a wide variety of plants to include bergamot, various thistles, common milkweed, and butterfly weed. Larvae feed on the violet plant family.

Adult butterflies emerge in late June or early July with the flight lasting until late August or early September.

The butterfly also is found at Fort Indiantown Gap, Pa., and has been co-existing with training there, he said.

“I don’t think the butterfly will have that much impact on ground training here,” Wilder said. “It may have some impact on activities that permanently remove habitat, like building construction.”

Fort McCoy NRB personnel will help manage the installation’s land to support the butterfly. Controlling brush through mechanical means, herbicides, and prescribed fire all will all be considered.

The frequency of prescribed burns will be monitored to ensure the regal fritillary butterfly is not negatively affected.

(See related story.)

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