— Isabella Bledsoe, Land Bank Summer Intern

On Monday, May 4th, 2020, the U.S. Fish and Wildlife Service listed the island marble butterfly (Euchloe ausonides insulanus) as an endangered species. There are approximately 200 island marble butterflies on San Juan Island and the main population is located at American Camp, in the San Juan Island National Historic Park.The marble butterfly is roughly the diameter of a golf ball from wingtip to wingtip. The top of its wings is white with occasional black markings, while the bottom of the wings has a greenish-yellow marbled pattern. It was thought to be extinct until it was found on San Juan Island and Lopez Island in 1998. Since then, volunteers and land managers have worked to restore the butterfly’s shoreline prairie habitat, which has declined due to development, deer browsing, mowing and other contributors.

WDFS photo island marbleThe butterfly’s main food sources are mustard plants, such as the field mustard (Brassica rapa) and tall tumble mustard (Sisymbrium altissimum). The butterfly lays eggs in the mustard flowers, and full-grown adults emerge in the spring. Local restoration efforts have focused on increasing breeding grounds through planting mustard plants – and have seen some success.

A year ago this month, a marble butterfly was seen in one of the San Juan Preservation’s habitat plots located within the Land Bank’s Frazer Homestead Preserve, which is close to American Camp. This was one of the first appearances of the marble butterfly outside of American Camp in years, and it is a sign that restoration efforts are working and it cause for celebration. The butterfly was named Amelia, and we’re hoping that her offspring will be seen this season.

Cover image courtesy of Washington Department of Fish and Wildlife
Image in text courtesy of National Park Service