They're Always in the Last Place You Look

Frosted Elfin

Globally Rare Butterfly Found at a New Site in Pennsylvania

From distant planets to penicillin, some of the greatest scientific discoveries have happened by chance. Betsy Leppo, an invertebrate zoologist with the Pennsylvania Natural Heritage Program, knows this all too well after learning about a new population of the globally rare frosted elfin butterfly in Huntingdon County, Pennsylvania.

“We were actually looking for a different rare butterfly at that time,” she said, “but in the process of all that, we just serendipitously encountered these naturalists in the field.” Naturalists John and Becky Peplinski told them about the elfin site. It was the first new site documented in Pennsylvania in recent decades.

When U.S. Fish and Wildlife Service biologist Nicole Ranalli got word of the discovery, she was surprised by the depth of their survey records, complete with photos and observation dates. “They had some really detailed information,” she said. “You don’t generally get that.”

Pennsylvania now had two sites with confirmed populations of frosted elfin. For Leppo and Ranalli, it was a sign the species could make a comeback.

Frosted elfin records stretch as far back as the early 1800s. Scientists have extensive information about sites where the butterfly used to be, and less data about where they persist. The Service and state agencies recently invested in surveys across the Northeast to update records.

While the new site is not in past records, Leppo doesn’t think they were far away because unlike monarch butterflies, frosted elfin aren’t able to travel long distances. “Their populations do move around a little bit,” Leppo explained. “But they’re not strong fliers. Odds are there was a population around there, just not in that exact spot.”

The frosted elfin’s historic range is far and wide. It stretches down the entire east coast from southern Canada to Florida and goes as west as Texas. But this rare butterfly has been extirpated from Vermont, Georgia and Illinois due to the gradual disappearance of suitable habitat.

This invertebrate is not associated with a conventional butterfly habitat. Instead of living in lush meadows, frosted elfin, along with the plants upon which they lay eggs and their caterpillars feed, thrive in young habitats with dry, sandy soil. The elfin populations of Pennsylvania have only been observed using yellow wild indigo (Baptisia tinctoria) for their life cycle, but other populations in the butterfly’s extensive range also use lupine as their host plant.

Henry's Elfin in my back yard

The Frosted Elfin is very similar to Henry's Elfin, which is at least reasonably common around here, if you look in the right places at the right time (about a 1 month window in early spring).  I can usually find them at that time picking fights with the Spring Azures that hang around the back yard. They're pretty cryptic, and it's easier to see them when they chase the azures out of their territory. I'd be hard pressed to actually identify a Frosted as opposed to Henry's if one showed up.

Reportedly, their list of favorite foods is a bit more diverse than the Frosted:

Caterpillar Hosts: Diverse plants texana) in Texas; dahoon (Ilex cassine), American holly (I. opaca), and yaupon (I. vomitoria) in Florida and North Carolina. Redbud (Ceris canadensis), huckleberries and blueberries (Vaccinium species), Mexican buckeye (Ungnadia speciosa), and Viburnum species are selected in other locations.

Which just goes to show it doesn't pay to be a picky eater.