The frosted elfin butterfly returns home to North Florida

The spring sun glinted off the cars rolling through Ichetucknee Springs State Park, but the caravan wasn’t headed to the park’s famous recreation spots. It was there for conservation, and the scientists in the lead were towing the precious cargo: tiny green caterpillars. Entering a trail road typically closed to visitors, the cars bounced along in deep, sandy grooves and snagged branches on their undercarriages.

When the group finally stopped, word reached the front that not everyone had made it. But even a blown tire couldn't stop the crew. They caught up on foot, unwilling to miss the main event: releasing caterpillars of the frosted elfin butterfly (Callophrys irus).

Though they were at the center of attention on release day, frosted elfins are often overlooked. “The butterfly is very easy to miss if you don't know what you're looking for,” said Jaret Daniels, curator of Lepidoptera at the Florida Museum of Natural History’s McGuire Center for Lepidoptera and Biodiversity.

With wingspans of about an inch, the butterflies are a muted grey-brown color and have a light dusting of frosty white scaling on their hind wings. They are rather inconspicuous and rarely studied in this region, which means scientists have some notable gaps in their understanding of the species. “We're trying to disentangle some things with this butterfly,” Daniels said. “Everything that we do in the lab is pioneering because nobody has reared this insect in captivity in the Southeast before. We're learning a lot of new things about it.”

Daniels’ lab, which led the introduction at the state park, has been raising the rare frosted elfin for over two years. Once found throughout the eastern United States and southern Canada, the butterfly’s range has been reduced significantly to scattered populations, with development and fire suppression threatening its remaining pine forest and sandhill habitats. It has been listed as endangered, threatened or of conservation concern in 11 U.S. states and is currently being considered for federal protection under the U.S. Endangered Species Act. Frosted elfins have already gone extinct in Canada and several other states. Today, thanks to a broad collaborative effort, Florida has the largest remaining population in the Southeast.

This spring, researchers in the Daniels lab successfully reared some 400 caterpillars. Keeping enough in the lab to ensure a healthy population for next year, they released the additional 253 caterpillars into their historic North Florida range.

In preparation for the inaugural release, researchers placed three dozen caterpillars, each one vibrant green and barely the width of a fingernail, in clear plastic condiment cups with a leafy sprig for food. In Florida, the frosted elfin caterpillars only eat sundial lupine (Lupinus perennis), a plant with clusters of purple flowers and palmlike leaves radiating out from the center of tall stalks.

The caterpillars may be small, but they can pack away a lot of food. In the lead-up to the release, the scientists were making three trips a week to local patches of sundial lupine to collect enough to satisfy the lab’s hungry caterpillars.

Fortunately, Ichetucknee Springs State Park has plenty of sundial lupine on the menu. The site where the release group gathered had short, blackened saplings, remnants of a previous fire and a green understory blanketed with shin-high plants interspersed with bursts of purple lupine blooms.

“They love the flowers. They’re like superfood for them,” Daniels said as researchers gently placed the caterpillars on the leaves of the lupines. “We’re releasing them onto a fantastic buffet for them to enjoy.”

Half of the caterpillars were placed on plants inside of “catios,” pop-up, mesh tents that, while intended for feline pets, may also protect the caterpillars against birds and other potential predators. By monitoring the caterpillars inside and outside of the tents, scientists can determine their effectiveness, which will inform how they conduct future releases.

After about a week munching on the plant, the caterpillars crawl down the stalk and begin the next step of their life cycle as pupae buried under the leaf litter or in the sand for the winter.

In addition to protecting them from predators and cold temperatures, burying underground is an effective defense against fire, which is both a concern and a necessity for the frosted elfin. The timing, frequency and intensity of fires are key. The researchers coordinate with the park’s prescribed burn schedule to protect the frosted elfin, while also allowing the fire to create the open forest understory that the sundial lupines need to thrive. The caterpillars are especially vulnerable to fire, so the prescribed burns need to take place after they pupate. The team also released the caterpillars at two different sites in the park, so when fire goes through one patch, nearby habitat can offer a refuge.

“The fire is critical, but you wouldn’t want to have the habitat for an entire population burn at one time,” Daniels said. “It takes several years to rebound after fire, so the only realistic way to think about restoring these butterflies is to build in safeguards.”

In the spring, researchers hope to find frosted elfin butterflies and use genetic testing to glean insight into their dispersal and colonization patterns. After a quick, nonharmful sample is taken, a DNA analysis can reveal the identity of the butterfly's mother, and because offspring from the same individual were placed together, scientists can determine each butterfly’s original release site. From this, the team can infer which butterflies are moving around and which reintroduction sites are most successful.

Researchers hope to continue these releases and eventually create a self-sustaining population of frosted elfins at the state park. But such an achievement would likely take multiple years. “Conservation recovery work doesn't happen overnight,” Daniels said. “We want to make sure what we do is founded on good science, and we build in the time we need to be successful.”

In the coming year, the team will release caterpillars at another site in North Florida, and Daniels plans to eventually expand this work beyond the state. He is currently collaborating with biologists in Virginia to collect and establish a breeding population of their frosted elfins in his lab, which is the first step toward one day releasing the butterfly to sites across their state.

“We have some fantastic partners, and that makes all the difference in everything from permitting to on-the-ground work,” Daniels said. “In science and conservation, it takes a village to make this happen.”

Partners involved in the frosted elfin release include Tall Timbers Research Station, the Florida Fish and Wildlife Conservation Commission and the Florida Park Service.