The Return of Swamp Metalmarks

The swamp metalmark is an endangered species in Illinois. In fact, many people consider it to be extirpated (locally extinct) from the entire state. The reason the butterfly is so rare is that it inhabits an extremely rare type of wetland called a fen. Its caterpillars can only feed on the leaves of swamp thistle and tall thistle. Both grow in fens. We are attempting to re-establish swamp metalmarks to their last known home in Illinois, Bluff Spring Fen near Elgin.

In Indiana I found dozens of metalmarks from a wooded fen near the Ohio River. We brought four females into the laboratory, and set them up in special cages to lay eggs. Over the course of about a week and a half, the butterflies laid over 200 eggs. We are currently waiting for them to hatch. When they do, we will place them on leaves of swamp thistle and rear them to adulthood. We hope to have adults in August when we can release them at their new home. With a bit of luck, they will establish a new population.