Euchloe ausonides insulanus
Photo by James Miskelly
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At a Glance
The island marble is the largest subspecies of the large marble (Euchloe ausonides). It was thought to have gone extinct after a 1908 sighting until being identified again 90 years later.
Range: On San Juan Island and Lopez Island in Washington State.
Habitat Type: Coastal shoreline and adjacent prairie.
Primary Diet: Larvae feed on field mustard (Brassica campestris) and tumble mustard (Sisymbria altissimum). Adults use a variety of flowers for nectar.
Estimated Population: The exact number of butterflies is not known but in most years there may be less than 2000.
States with Current Habitat
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The Island Marble Butterfly, which was once thought to be extinct, faces multiple threats to survival and political interference in 2006 appears to have prevented its protection under the Endangered Species Act.
Why Protection is Needed
The Island Marble Butterfly faces threats due to habitat loss from development, road maintenance, invasive plants and weather events such as winter storms that produce large waves.
This butterfly historically lived along coastal grasslands and adjacent prairies in a small part of the Northwest. It disappeared after a sighting in 1908 and was thought extinct until it was found again on San Juan Island, Washington in 1998.
In 2005, two hundred twenty-five surveys were conducted at 110 potential Island Marble sites by staff from the Washington Department of Fish and Wildlife, USFWS, Washington Department of Natural Resources, the Xerces Society, and local volunteers. As a result of these searches, Island Marble butterflies are now found at 19 sites although most have fewer than 5 individuals and only one site is considered large enough to be a viable population.
In 2006, Fish and Wildlife Service issued a positive 90-day finding, indicating that listing for the butterfly may be warranted and initiated a listing determination process. The review was conducted as the result of a petition by Xerces Society and Center for Biological Diversity.
In conversations with the Xerces Society during the review process, Fish and Wildlife Service biologists stated that the butterfly met all of the criteria for listing. However, in September 2006, the same biologists said they were no longer allowed to discuss the listing. In November the Service denied protection to the Island Marble Butterfly without legal or scientific justification.
Additional Information
On May 21, 2008 Scott Hoffman Black, executive director of the Xerces Society, testified about the Island Marble Butterfly before the House Natural Resources Committee during a hearing on political interference in endangered species protections. He supplemented testimony by the Government Accountability Office that indicated at least four high-ranking Interior Department officials – other than Julie MacDonald, who is mentioned elsewhere in this report – had been influencing endangered species decisions.
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