MADISON, WI – Conservationists are shining a light on a rare, orangish-brown resident of Wisconsin’s wetlands that is currently fighting for its survival.
The Swamp Metalmark (Calephelis muticum), a small butterfly known for the distinctive metallic spots adorning its wings, remains one of the state’s most vulnerable endangered species. According to the Wisconsin Department of Natural Resources (DNR), these butterflies are highly specialized, thriving only in very specific environmental conditions that are becoming increasingly rare across the Midwest.
According to wildlife experts, the Swamp Metalmark does not actually live in traditional swamps despite its common name. Instead, the species is found exclusively in “calcareous fens”—mineral-rich wetlands fed by calcium-laden groundwater. These unique ecosystems are characterized by low vegetation and sedges, providing the delicate balance necessary for the butterfly’s life cycle.
According to information provided by the DNR on Monday, the survival of the Swamp Metalmark is intrinsically linked to the presence of the Swamp Thistle (Cirsium muticum). This specific plant serves as the sole host upon which the butterflies lay their eggs. Because the Swamp Thistle only grows in high-quality calcareous fens, the loss of these wetlands directly leads to the disappearance of the butterfly population.
While many of the highest-quality remaining fens are currently protected within Wisconsin’s state natural areas, the species remains at risk due to habitat fragmentation. The DNR continues to monitor these protected zones to ensure the preservation of the calcium-rich groundwater and the Swamp Thistle populations essential for the Swamp Metalmark’s continued existence in the state.
