Spreading Their Wings
Butterflies bred in a Chicago lab are fluttering their way back to Illinois swamps.
One by one, 80 swamp metalmark butterflies emerged from their chrysalises. It was the spring of 2013, and the newly formed insects were stretching their wings for the first time inside a lab within Chicago’s Peggy Notebaert Nature Museum. Named for the flecks of silver markings, these butterflies were soon heading to the Bluff Stream Fen, a spring-fed wetland about 40 miles northwest of downtown—and the place where the last swamp metalmark fluttered its wings in Illinois, way back in 1939.
Doug Taron, the museum’s curator of biology, had raised the 80 insects from eggs to caterpillars to butterflies ready for release into the wild. Eighty individuals may not seem like a lot, especially considering that Taron wants to repopulate close to 50 acres of preserved land with them, but that’s all he had at the time—and it was still more than the entomologist had ever seen in one place. Butterflies—from monarchs to metalmarks—have fallen on bad times, but it's encouraging to know people have dedicated their careers to trying to save them. Taron is one of those people.
In the weeks after their release, he kept tabs on the metalmarks and saw signs of them getting ready to mate in the wild. When he returned the following summer, however, there was no trace of the insects—not even as much as a chewed up leaf to give them away. Taron’s not willing to write them off yet, though. These bugs, after all, are hard to find.
Taron would know. He’s collected rare metalmark eggs and females from elsewhere in the Midwest and continues to raise his butterflies in the lab. This summer he’ll be out in the fen again, seeing if they take to it. If all goes well, he’ll have even more to set free next spring. “We would be doing this even if I had seen them [last summer].”
Swamp metalmark butterflies—and the thistles their caterpillars eat—thrive only in fens. These wetlands sit atop limestone, which makes their alkaline water rich in minerals. Unfortunately, the state’s fens have been disappearing due to development and the slow creep of woody invasive trees and shrubs, such as stiff dogwood and white snakeroot.
Metalmarks were once abundant in Bluff Spring Fen, but mining, draining for development, dumping, and off-road vehicles left the wetland in ruins in the last century. The diverse native flora there—including spikesedge and shrubby cinquefoil—led Cook County to protect the area in 1980. Preserve managers and volunteers then began converting the land to the swamp it once was. The metalmarks, however, were already gone.
Five years ago Taron began collecting females from Indiana swamps for what would become his butterfly nursery. He could have taken them from Wisconsin, too, but he opted for more southern populations that may fare better as the climate warms.
Each trip, he captures about three to six metalmarks (not wanting to take too many from the wild) and keeps them in a plastic cup contraption, threading a thistle through a hole at the bottom. Chemicals receptors on a female butterfly’s feet let her know that she’s on the right plant and can lay eggs. Taron also puts a Q-tip wetted with diluted honey in the cup to give her a snack.
Once caught, the butterfly is off to the museum to lay eggs and enchant guests visiting the indoor butterfly lab. Volunteers harvest the tiny pink eggs—each about half the size of a poppy seed—placing them one by one onto moistened pieces of tissue paper within petri dishes. About two weeks later, they hatch.
This production process is promising but limited. Having the metalmarks mate within the lab would be easier, but the butterflies are very reluctant to court in captivity. “I joke that we play Barry White in the lab,” Taron says. Unfortunately, nothing seems to set the mood.
After a few years of trial and error, Taron has adapted his methods and says that this year might prove to be the most successful yet. Now, he’ll be making two trips into the field instead of one, and he'll keep caterpillars from the later trip over the winter. He’ll place them in a chest freezer programmed to mimic the temperatures and daylight of a typical Illinois winter. With any luck, next summer he’ll have more than twice as many butterflies to release—at least 160 (each female lays 70 eggs on average, but not every one hatches).
It still doesn’t sound like a lot, but it’s a start and, possibly, the best chance metalmarks have in the region. Today it’s Bluff Stream Fen, and tomorrow…well, I know of a few marshes spots along Chicago’s western edges that could do with a little more flutter.
This article was originally published on onEarth, which is no longer in publication. onEarth was founded in 1979 as the Amicus Journal, an independent magazine of thought and opinion on the environment. All opinions expressed are those of the authors and do not necessarily reflect the policies or positions of NRDC. This article is available for online republication by news media outlets or nonprofits under these conditions: The writer(s) must be credited with a byline; you must note prominently that the article was originally published by NRDC.org and link to the original; the article cannot be edited (beyond simple things such grammar); you can’t resell the article in any form or grant republishing rights to other outlets; you can’t republish our material wholesale or automatically—you need to select articles individually; you can’t republish the photos or graphics on our site without specific permission; you should drop us a note to let us know when you’ve used one of our articles.
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