From Washington To You
An island marble butterfly perched on vegetation on San Juan Island.
Photograph by E. Adams, U.S. Fish and Wildlife Service, May 22, 2023. Public domain.

From Washington to you

Island Marble Butterfly

American Camp prairie · San Juan County · rediscovered 1998

Thought extinct since 1908, this fuzzy green-and-white butterfly turned up at American Camp in 1998 — and is now federally endangered.

The island marble butterfly (Euchloe ausonides insulanus) was believed extinct after 1908, when the last known specimens came from Vancouver and Gabriola islands in British Columbia. In 1998 it was rediscovered during a prairie butterfly survey at American Camp on San Juan Island.

NPS calls it one of the rarest butterflies in North America. Adults look fuzzy, with marbled green, yellow, white, and black wings that span less than 2 inches. Today the few hundred remaining animals inhabit a small area on San Juan Island. They have been extirpated from Lopez Island.

The U.S. Fish and Wildlife Service listed the butterfly as endangered in 2020. Critical habitat covers about 812 acres, 744 of them at American Camp. NPS biologists collect 100 to 300 eggs and caterpillars each spring. About 80 to 90 percent survive in the rearing lab, compared with about 5 percent of eggs in the wild. The sources below are San Juan Island National Historical Park pages.

  • Wildlife & Ecology

Sources (1)

Last reviewed: September 21, 2026

Keep wandering

  • nearby

    American Camp

    Lieutenant Colonel Silas Casey sited the U.S. camp in 1859 outside British naval range — for a Pig War that was never fought.

  • nearby

    English Camp

    Royal Marines camped on a Coast Salish shell bank on Garrison Bay while the United States and Britain argued over who owned the San Juans.

  • nearby

    The Pig War

    The United States and Great Britain nearly went to war over San Juan Island. The only casualty was a pig.