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The large marble butterfly (Euchloe ausonides) was proposed for listing in 2023 through a petition submitted by the Xerces Society.

The large marble butterfly is found in 16 states ranging from Alaska to New Mexico and as far east as Michigan. Despite its widespread distribution, studies have ranked the large marble as one of the western butterfly species most at risk of extinction in the next 50 years. Large marble populations are threatened by widespread habitat degradation, introduced predators, pesticide exposure, climate change, and inadequate regulation across the states in which it is found.

One large marble subspecies, Euchloe ausonides ausonides, is of particular concern, in danger of extinction in almost the entirety of its present range. The petition requests this subspecies be listed as Endangered. The Xerces Society’s petition also requests that five additional subspecies (E. a. coloradensis, E. a. mayi, E. a. ogilvia, E. a. palaeoreios, and E. a. transmontana) are listed as Threatened. All of the populations have been declining.

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