Swamp Metalmark Reintroduction Project
S. Borkin, MPM
The swamp Metalmark butterfly, Calephelis mutica, is the only member of the Riodininac that occurs in Wisconsin. Both in the alkaline fens where the butterfly lives, but populations of the butterfly are rare in the state. Reflecting this, the butterfly was listed as a state endangered species in 1989.
Swamp Metalmarks were first reported at RNC in the mid-1970s, but by the early 1990s, it was no longer found. Following selective tree and brush removal (primarily Ninebark and Tamarack) in the fen-like area at RNC, efforts to reestablish the butterfly were initiated in 1994 with the translocation of adults from other population sites and larvae raised from eggs laid by a captive female. The population was monitored by counting larvae found on host Swamp Thistle plants. Distribution within the habitat was noted also. In 1999 and 2000, no additional adults or larvae were introduced.
The population level in 2000 was nearly identical to that of 1999, which may indicate that the site in its present condition has reached its carrying capacity. In fall of 2000, 17 host plants hosting 38 larvae were located. These will continue to be monitored. Long term monitoring of this population is essential to obtain baseline information to learn more about natural fluctuations due to weather and to develop guidelines for best management practices.
Learn more about Sue Borkin and the Milwaukee Public Museum