ELGIN — Endangered butterflies are getting ready to be released in suburban Chicago.
The Swamp Metalmark butterflies were bred at the Peggy Notebaert Nature Museum's in Chicago by museum biologists. The butterflies are known for their reddish-brown wings that are lightly checkered.
Biologists have been growing the population in the museum's conservation lab by treating eggs differently to keep them more hydrated. They're set to be released at Bluff Spring Fen in Elgin sometime around Aug. 26.
Biologists have spent the last six years working to re-introduce Swamp Metalmarks to Illinois.
Museum officials say the butterflies have "charming personalities."
The 100-acre Bluff Spring Fen features wetlands, woodlands, prairies and savannas with mineral-rich water in its springs and streams. It is considered an ideal habitat for rare and endangered species.