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Endangered butterfly soars again in Elgin fen

Elg8/29/13--Scientists Doug TarKaren Kramer Wilsfrom Chicago's Peggy Notebaert Museum released 18 swamp metalmark butterflies rare species thhas been extinct northern

Elgin, 8/29/13--Scientists Doug Taron and Karen Kramer Wilson from Chicago's Peggy Notebaert Museum released 18 swamp metalmark butterflies, a rare species that has been extinct in northern Illinois for over 70 years, into Bluff City Fen Thursday morning. | Jon Langham/For Sun-Times Media

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Updated: October 1, 2013 6:25AM

ELGIN — With a spiked “hairdo” down its back, the inch-long swamp metalmark butterfly is “the punk rocker of butterflies,” biologist Doug Taron jokes. And with just two vegetables on its menu for 80 percent of its life, it’s one of nature’s fussiest eaters.

It’s the latter quirk that has made the little metalmark extinct in Illinois since the 1980s, and an endangered species nationwide.

But Thursday, in a small Cook County Forest Preserve District nature preserve hidden away between Elgin’s Bluff City Cemetery and the Metra West railroad line, the swamp metalmark flew again in northern Illinois for the first time in perhaps 70 years.

Taron, curator of biology at the Peggy Notebaert Nature Museum in Chicago, and his museum colleague Karen Kramer-Wilson, released 18 adult metalmarks. He and Wilson had reared them from the egg in a Notebaert Museum laboratory as part of a project to restore the metalmark to Illinois.

The 18 were released in the Bluff Springs Fen, 40 acres of a swampy 150-acre nature preserve where springs flowing upward through limestone create a kind of chemistry in the water that encourages the growth of fairly rare plants such as the purple-flowered swamp thistle. The swamp thistle and a close relative in the thistle family are the only kind of plants that swamp metalmarks eat while they are caterpillars and that they also depend on to provide shelter through cold Illinois winters.

Named for tiny silver-colored flecks on both sides of their wings, adult swamp metalmarks are a boring rust color on the top but a golden yellow underneath.


Taron said metalmarks go through two generations a year. After eating thistle leaves for two months in the spring, metalmark caterpillars form a cocoon-like chrysalis. A few weeks later, they emerge as full-grown (though still just 1-inch-long) adults. Eating only enough flower nectar to keep up their strength, the adults mate, lay eggs and die about two weeks after emerging.

The eggs they laid in mid-spring then hatch into new caterpillars that repeat the process, laying eggs and dying in August or September. The caterpillars that emerge from those eggs produce their own chemical antifreeze (glycerol) and spend the winter under the ground-hugging leaves of a swamp thistle plant so they can begin the same process the next spring.

The last swamp metalmarks seen in northern Illinois were spotted at Bluff Springs Fen in 1939. Over the next few decades, Taron says, the fen’s once-open, sunny flower fields became choked with invasive trees and brush that left the metalmarks without enough swamp thistle plants to survive.

The culprit is obvious, Taron believes: Local and state policies that call for wildfires to be put out whenever they begin, rather than letting them burn as the fires did in the Prairie State’s frontier days so they can kill off the oak trees and invasive bushes that were ruining the fen.

Beginning in the 1980s, a group of enthusiasts called the Friends of the Fen — which included Taron even before he went to work for the Notebaert Museum — started to reverse that by staging prescribed burns and cutting down excess trees and brush.

Taron and Kramer-Wilson expect to release about 100 more of the rare insects at the fen over the next two weeks. All are descended from four fertilized female metalmarks that Taron collected in southern Indiana in June.

This is the sixth year that Taron has been working on the project, and steady refinements in the laboratory-rearing process meant the museum finally had enough full-grown butterflies to release to the wild. Taron said one key breakthrough was figuring out how to give the chrysalises enough water but not too much water.

The four Indiana mothers laid about 320 eggs, and 118 of those have survived to form chrysalises. “We lose some at every step,” Kramer-Wilson said. ”Some eggs never hatch. Some of the newborn caterpillars fail to thrive and just die. Some of the caterpillars that form chrysalises never emerge as adult butterflies.”

Still, she said, that one-third survival rate is phenomenal compared to what would have happened to those 320 eggs out in the wild. Lots of other creatures have butterflies or caterpillars or insect eggs on their own menu, from birds to dragonflies to wasps to stink bugs to spiders to lizards to flies.

“The most mortality comes in the caterpillar stage, when some wasps and flies plant eggs on the caterpillar that eats it out from the inside,” Taron said.

Goodbye, kids

As Taron and Kramer-Wilson lifted the last of the first batch of adult butterflies on their fingers and placed them onto wild golden glow flowers that would provide them with nectar to drink, a pair of dragonflies — one of many wild creatures that eat butterflies in a fen — swooped and looped a few feet overhead.

“We hope the dragonflies have a very successful population, eating things other than the swamp metalmark butterfly,” Taron said. “We have also worked to restore some endangered species of dragonfly at the fen.”

Taron and Kramer-Wilson said that after months of slaving seven days a week to keep alive the four butterflies — then their 320 eggs, then about 120 caterpillars — letting them go felt like a great climax, but it did have a dark side.

“This is like raising kids for years and then sending them off to college,” Kramer-Wilson said.

“ — But a college where the professors might eat them,” Taron said.

Taron said it was a good sign that the 18 adults released Thursday seemed to be staying in the immediate area. If they wander too far apart, they might never find mates and could die without laying eggs.

“We hope this will re-establish a self-sustaining population at the fen,” Taron said. He said they will know for sure when they search thistle plants for caterpillar damage this winter and then look for live metalmarks — those 118 butterflies’ children — next spring.

But even without the metalmark, the restorations have made Bluff Spring Fen’s rare brand of ecology thrive. Taron said the 40 acres contain 60 other species of butterfly and some 400 species of plants, many of which can grow only in limestone-spring fens.

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