The Xerces blue (''Glaucopsyche xerces'') is a recently extinct

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

butterfly Butterflies are winged insects from the lepidopteran superfamily Papilionoidea, characterized by large, often brightly coloured wings that often fold together when at rest, and a conspicuous, fluttering flight. The oldest butterfly fossi ...

in the gossamer-winged butterfly family,

Lycaenidae Lycaenidae is the second-largest family (biology), family of butterflies (behind Nymphalidae, brush-footed butterflies), with over 6,000 species worldwide, whose members are also called gossamer-winged butterflies. They constitute about 30% of ...

. The species lived in coastal sand dunes of the Sunset District of the

San Francisco Peninsula The San Francisco Peninsula is a peninsula in the San Francisco Bay Area that separates San Francisco Bay from the Pacific Ocean. On its northern tip is the City and County of San Francisco. Its southern base is Los Altos and Mountain View, ...

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

. The Xerces blue is believed to be the first American butterfly species to become extinct due to

loss of habitat Habitat destruction (also termed habitat loss or habitat reduction) occurs when a natural habitat is no longer able to support its native species. The organisms once living there have either moved elsewhere, or are dead, leading to a decrease ...

caused by urban development. The last Xerces blue was seen in 1941 or 1943 on land that is now part of the

Golden Gate National Recreation Area The Golden Gate National Recreation Area (GGNRA) is a U.S. National Recreation Area protecting of ecologically and historically significant landscapes surrounding the San Francisco Bay Area. Much of the park is land formerly used by the Unite ...

Name

The specific name derives from the French spelling of "Xerxes", the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

name of the Persian kings

Xerxes I Xerxes I ( – August 465 BC), commonly known as Xerxes the Great, was a List of monarchs of Persia, Persian ruler who served as the fourth King of Kings of the Achaemenid Empire, reigning from 486 BC until his assassination in 465 BC. He was ...

and

Xerxes II Xerxes II (; ; ; died 424 BC) was a Persian king who was very briefly a ruler of the Achaemenid Empire, as the son and successor of Artaxerxes I. After a reign of forty-five days—where he only had control over the Persian heartlands— ...

of the fifth century BC. An endangered

invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...

conservation group known as the Xerces Society is named after the Xerces blue.

Taxonomy

Genetic analysis of museum specimens published in 2021 confirmed that the Xerces blue represented a distinct species within the genus '' Glaucopsyche'', with its closest relatives being '' Glaucopsyche australis'' ''and Glaucopsyche pseudoxerces,'' with this group most closely related to '' Glaucopsyche lygdamus'' (the silvery blue). Xerces_Blue

Extinction and ecology

The species was first described and documented in 1852. It was characterized by blue wings with white spots. The butterflies fed on vegetation belonging to the genus '' Lotus'' and ''

Lupinus ''Lupinus'', commonly known as lupin, lupine, or regionally bluebonnet, is a genus of plants in the legume family Fabaceae. The genus includes over 199 species, with centre of diversity, centres of diversity in North America, North and South A ...

''. The loss of the ''Lotus'' plant that the butterfly fed on while in its

larval A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

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. ''Lupinus'', the Xerces blue's other vegetative food source, was not suitable for the

larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

l stages. Preserved specimens are found in

California Academy of Sciences The California Academy of Sciences is a research institute and natural history museum in San Francisco, San Francisco, California, that is among the largest List of natural history museums, museums of natural history in the world, housing over ...

, Bohart museum, and the

Harvard Museum of Natural History The Harvard Museum of Natural History (HMNH) is a natural history museum housed in the University Museum Building, located on the campus of Harvard University in Cambridge, Massachusetts. It features 16 galleries with 12,000 specimens drawn fr ...

Reestablishment efforts

Efforts are ongoing to reestablish related butterflies in the Xerces blue's former habitat. The

Palos Verdes blue The Palos Verdes blue (''Glaucopsyche lygdamus palosverdesensis'') is a small endangered butterfly native to the Palos Verdes Peninsula in southwest Los Angeles County, California, United States. As its distribution has been proven to be limited ...

(''Glaucopsyche lygdamus palosverdesensis''), which is considered a

Los Angeles Los Angeles, often referred to by its initials L.A., is the List of municipalities in California, most populous city in the U.S. state of California, and the commercial, Financial District, Los Angeles, financial, and Culture of Los Angeles, ...

cousin of the Xerces, is being reared in labs. A new Xerces-like subspecies of the silvery blue ('' Glaucopsyche lygdamus''), which the Xerces blue was thought to be a subspecies of has been discovered as well, and has been analyzed as a potential way to revive the Xerces blue. Successful reintroduction efforts of the silvery blue occurred in 2024 in a collaboration between the Presidio Land Trust, National Park Service, and California Academy of Sciences, among other groups. In 2025, silvery blue offspring were documented in the Lobos Creek Valley Dunes, implying successful reproduction within the Presidio. Releases of silvery blues have continued in 2025.

References

External links

Xerces.org – An invertebrate conservation society
{{Taxonbar, from=Q1042181 Glaucopsyche Butterflies described in 1852 Extinct insects since 1500 Extinct butterflies Extinct animals of the United States Natural history of the San Francisco Bay Area Species made extinct by human activities Species that are or were threatened by urbanization Species that are or were threatened by habitat loss