Swamp Metalmark Returns to Bluff Spring Fen

The swamp metalmark, Calephelis mutica, a deep red-orange butterfly with black and white markings on lightly fringed wings, returned to Cook County's Bluff Spring Fen Nature Preserve in July after an absence of more than 60 years.

The discovery came less than a year after Doug Taron, curator of biology at the Peggy Notebaert Nature Museum, released 30 caterpillars in September 2002 as part of a collaborative project involving the Milwaukee Public Museum, the Illinois Nature Preserves Commission, The Nature Conservancy, Friends of the Fen, and the BP Foundation. The Notebaert Museum, which is home to one of only a handful of butterfly breeding labs in North America, raised the caterpillars from eggs laid by adult metalmarks, which were obtained from Wisconsin.

Collaborators believe that substantial restoration efforts on the site since the early 1980s, which have cleared invasive brush overgrowing much of the metalmark's fen habitat, have been key to the reintroduction's success. Its ecology much improved, the fen now contains a substantial population of swamp thistle (Cirsium muticum), the host plant for the metalmark and one that depends on a sunny open fen.