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The Xerces blue (Glaucopsyche xerces) is an extinct species of butterfly in the gossamer-winged butterfly family, Lycaenidae. The species lived in coastal sand dunes of the Sunset District of San Francisco peninsula. The Xerces blue is believed to be the first American butterfly species to become extinct as a result of loss of habitat caused by urban development. The last Xerces blue was seen in 1941[2] or 1943[3] on land that is part of Golden Gate National Recreation Area.

Xerces blue
Glaucopsyche xerces.jpg
Samples of the extinct Glaucopsyche xerces butterfly in the collections of the Field Museum of Natural History

Extinct  (1941) (IUCN 2.3)[1]
Scientific classification edit
Kingdom: Animalia
Phylum: Euarthropoda
Class: Insecta
Order: Lepidoptera
Family: Lycaenidae
Genus: Glaucopsyche
G. xerces
Binomial name
Glaucopsyche xerces
(Boisduval, 1852)

Preserved specimens are found in California Academy of Sciences, Bohart museum, and the Harvard Museum of Natural History.[4] The species was first described and documented in 1852.[4] It was characterized by blue wings with white spots.[5] The butterflies fed on vegetation belonging to the genus Lotus and Lupinus.[5] The loss of the Lotus plant that the butterfly fed on while in its larval stages is believed to be one reason for the extinction of the Xerces blue. The plant could not survive in the disturbed soils due to human development, and was no longer available to the Xerces blue.[4][5] Lupin, Xerces blue's other vegetative food source, was not suitable for the Larval stages[5]

Efforts are on to reestablish related butterflies in the Xerces blue's former habitat. The Palos Verdes blue (Glaucopsyche lygdamus palosverdesensis), which is considered a Los Angeles cousin of the Xerces, is being reared in labs. A new Xerces-like subspecies of the silvery blue (Glaucopsyche lygdamus) has been discovered as well.

An endangered invertebrate conservation group known as the Xerces Society is named after the Xerces blue. The specific name derives from the French spelling of "Xerxes", the name of Persian kings Xerxes I and Xerxes II of the fifth century BC.


  1. ^ World Conservation Monitoring Centre (1996). "Glaucopsyche xerces". The IUCN Red List of Threatened Species. IUCN. 1996: e.T9244A12971422. doi:10.2305/IUCN.UK.1996.RLTS.T9244A12971422.en. Retrieved 9 January 2018.
  2. ^ Garth, J.S.; Tilden, J.W. (1986). California Butterflies. University of California Press. ISBN 0520052498.
  3. ^ Powell, J.A.; Hogue, C.L. (1979). California Insects. University of California Press. ISBN 978-0-520-03782-3.
  4. ^ a b c Resources, University of California Agriculture and Natural. "And Then There Were None: Bohart Museum Remembering Xerces Blue Butterfly In Effort to Help Preserve Other Species". Retrieved 2017-04-13.
  5. ^ a b c d Tilden, J. W. (1956). "San Francisco's Vanishing Butterflies" (PDF). The Lepidopterists' News: 113–115.

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