The Xerces Blue Butterfly
by: Robert C. Kuhmann

"Each extinction is a unique voice silenced in a universal conversation,
of which we ourselves are only one participant


In 1875, San Francisco lepidopterist Herman Behr wrote to his Chicago colleague Herman Strecker, lamenting that the Xerces Blue butterfly was "now extinct (as regards the neighborhood of San Francisco). The locality where it used to be found is converted into building lots, and between German chickens and Irish hogs no insect can exist besides louse and flea. "  Eventually, Behrís prophecy panned out, and the Xerces Blue ceased flying altogether.

Extinction Facts:

The Xerces Blue butterfly (Glaucopsyche lygdamus xerces) is perhaps the most famous of the extinct United States butterflies. It was a fascinating species that was once locally common at suitable habitats on the San Francisco Peninsula. It was of great interest to lepidopterists due to the remarkable variation in wing pattern; indeed, some of these varieties were originally considered to represent distinct species, until it was observed that the various forms readily interbred. The Xerces Blue, in essence, was a sub-species which consisted of only one population, although great variation was present in the individuals comprising the population. From this standpoint alone, the butterfly would have made an excellent subject for genetic, evolutionary, and ecological studies. Xerces was a small butterfly, the upper wing surfaces iridescent blue-violet in the male, brown in the female. Populations inhabited stabilized sandy sites with rather low-growing vegetation, including the former Lone Mountain Cemetery, the Presidio military base (just west of the Naval Hospital and north of Lobos Creek), several locations in the Sunset District (including the western slopes of Twin Peaks), and the Lake Merced area. By the 1930's, the butterfly was restricted to vacant lots.

The last known specimens were taken:

March 23, 1941 by W. H. Lange at the "Presidio" (a few specimens exist in museums). 

Life of a gentle Butterfly:

The Xerces Blue flew generally from mid-March to mid-April. Females laid their eggs on several leguminous plants: Deerweed (Lotus scoparius), Yellow-flowering Beach Lupine (Lupinus arboreus), and a blue-flowering lupine species (possibly Lupinus micranthus). Apparently, Deerweed was the most commonly utilized and preferred caterpillar food. All of the above foodplants are much more widespread than was the Xerces Blue: Deerweed, for example, occurs throughout the California coastal foothills. Close relatives of the Xerces Blue utilize Deerweed and various lupine species at many locations in the western United States. It appears that geographic isolation and climate, rather than food-plant specialization, limited Xerces to the San Francisco Peninsula.

"When the tiny wings of the last Xerces blue butterfly ceased to flutter. . . 



our world grew quieter by a whisper and duller by a hue. "

Left: Glaucopsyche lygdamus xerces (upper-side) - Field Museum, Chicago
Right: (under-side variations) - California Academy of Science

What's in a Name? A Historical note:

Xerxes (the 'c' is replaced by an 'x' and pronounced with a hard 'ks' sound in English) was king of Persia from 486 to 465 BC. A great deal of history revolves around the king and his reign that ended in his murder and in-family fighting that killed several of his heirs. The French entomologist Boisduval named the butterfly for King Xerxes, but retained the French spelling, Xerces.

Extinction may not always have to be forever:

Contrary to the popular conservation aphorism, extinction may not always have to be forever. Occasionally, the thoughtful reintroduction of an organism closely related to an extinct type can result in the functional reconstruction of the animal or plant thought to be lost in toto. The conditions permitting such a Lazarus act are rare, and their employment raises all sorts of philosophical questions. Still, reestablishment of species through their near relatives in restored habitats may be an act worth considering in some cases. I would like to nominate the Xerces Blue as a candidate for radical genetic reconstitution.



Blue butterfly of the Presidio,
Vanished and mourned as extinct.  
Wondrously, could it reappear,
Fluttering light in the grass. 

Et resurrexit tertia die
Et ascendit in coelum
Iterum venturus est cum gloria
Glaucopsyche lydamus xerces. 

"They . . . are simply the littlest of things that run the World. "

The USA and the World - What is left?

The United States is home to some 700 species of butterflies; 14 of them are listed as endangered or threatened by the U. S. Fish and Wildlife Service. Gone forever are the Xerces Blue, Sthenele Satyr, Pheres Blue, Strohbeen's Parnassius, and the Atossa Fritillary. Worldwide, the World Conservation Union cites 332 butterflies as being in trouble. But population data for most of the 20,000 known butterfly species is scant to nonexistent, and recent surveys in the Amazon River Basin suggest that another 2,000 species have yet to be discovered. We have no idea how many butterfly species are lost as we say goodbye to an acre of rain-forest with every heartbeat.  

The Great Spirit surely weeps:

Psychologists have not begun to ponder the emotional toll of the loss of fellow life. Nor have theologians reckoned the spiritual impoverishment that extinction brings. To forget what we had is to forget what we have lost. And to forget what we have lost means never knowing what we had to begin with. That would be among the greatest tragedies of all.

- Mark Jerome Walters, Program Director for Environment, Nathan Cummings Foundation in New York City


Litany to the Extinct (USA Butterflies)

Lone Mountain Cemetery was my last home. . 
Glaucopsyche lygdamus xerces
I was drowned when army engineers built a dam. 
Parnassius clodius strohbeeni

Air Force radar took my home in just a blip. 
Speyeria nokomis coerulescens
Violet on Mt. Pinos was my sole food. 
Speyeria adiaste atos

I took refuge on Twin Peaks, my cold oblivion. 
Speyeria callippe extincta
San Francisco was my home. 
Cercyonis sthenele

I was highly prized by rich collectors. 
Lycaena magna
Someone stole my shade and made me fly into the sun. . . 
Plebejus icarioides

Butterflies of North America

Butterflies of California
(Public information from the U. S. G. S. website)

Silvery Blue (Glaucopsyche lygdamus [Doubleday])

Wing span:

7/8 - 1 1/4 inches (2.2 - 3.2 cm).


Upperside of male iridescent silvery blue with narrow dark borders; female darker blue with wide borders. Both sexes have white fringe. Underside gray-brown; both wings with row of white-ringed, round black spots. Subspecies xerces (Doubleday) and presudoxerces Emmel and Emmel have large white spots with or without black centers.

Life history:

Males patrol near the host plants for females. Eggs are laid singly on flower buds and young leaves of the host plants. Caterpillars feed on flowers, seed-pods, and young leaves and are tended by ants. Chrysalids hibernate.


One flight from March-June at low elevations, June-August at high elevations.

Caterpillar hosts:

Astragalus, Lotus, Lupinus, Melilotus, Oxytropis, Lathyrus, Vicia, and other species in the pea family.

Adult food:

Nectar from flowers including Asteraceae.


A variety of locations including open woods, coastal dunes, prairies, meadows, road edges, rocky moist woods, and brushy fields.


Central Alaska south to southern California, Baja California, Arizona, New Mexico, and western Kansas. Along northern United States east to Nova Scotia and south to Georgia.


Subspecies palosverdesensis is thought to be extinct. Its historic range and its hostplant Astragalus leucopsis in the Palos Verdes Hills in Los Angeles County, California is largely extirpated, but an additional population was discovered in nearby San Pedro. This subspecies has The Nature Conservancy rank of G1 - Critically imperiled globally because of extreme rarity (5 or fewer occurrences, or very few remaining individuals), or because of some factor of its biology making it especially vulnerable to extinction. (Critically endangered throughout its range). Subspecies xerces is GX - presumed extinct. Subspecies pseudoxerces is rank T2.

Management needs:

Conserve all remaining habitat for the Palos Verdes Blue. Investigate status and conservation needs of subspecies pseudoxerces.


Emmel, T. C. and J. F. Emmel. 1973. The butterflies of southern California. Natural History Museum of Los Angeles County, Los Angeles. 148 pages. 

Ferris, C. D. and F. M. Brown. 1981. Butterflies of the Rocky Mountain States. University of Oklahoma Press, Norman. 442 pages. 

Layberry, R. A. , P. W. Hall, and J. D. Lafontaine.   1998. The Butterflies of Canada. University of Toronto Press, Toronto. 282 pages, 32 color plates. 

Matthews, J. R. , editor. 1990. The official World Wildlife Fund guide to endangered species of North America, Vol. 2. Beacham Publishing, Inc. , Washington, D. C. 636 pages. 

New, T. R. , editor. 1993. Conservation Biology of Lycaenidae (Butterflies). International Union for Conservation of Nature and Natural Resources. Gland, Switzerland. 173 pages. 

Opler, P. A. 1999. A field guide to western butterflies. Houghton-Mifflin Co. , Boston, Mass. 540 pages, 44 color plates. 

Opler, P. A. and G. O. Krizek. 1984. Butterflies east of the Great Plains. Johns Hopkins University Press, Baltimore. 294 pages, 54 color plates. 

Opler, P. A. and V. Malikul. 1992. A field guide to eastern butterflies. Peterson field guide #4. Houghton-Mifflin Co. , Boston. 396 pages, 48 color plates. 

Scott, J. A. 1986. The butterflies of North America. Stanford University Press, Stanford, Calif. 583 pages, 64 color plates. 

Stanford, R. E. and P. A. Opler. 1993. Atlas of western USA butterflies including adjacent parts of Canada and Mexico. Denver and Fort Collins, CO.

California State and Regional References:

Brown, J. W. , Real, H. G. , and D. K. Faulkner. 1992. Butterflies of Baja California. Lepidoptera Research Foundation, Beverly Hills, Calif. 

Comstock, J. A. 1927. Butterflies of California. Privately published, Los Angeles, Calif. [Facsimile available from Entomological Reprint Specialists, Los Angeles, Calif. ]

Dameron, W. 1997. Searching for butterflies in southern California. Flutterby Press, Los Angeles, Calif. 

Emmel, T. C. Editor. 1998. Systematics of western North American butterflies. Mariposa Press, Gainesville, Florida. 

Emmel, T. C. and J. F. Emmel. 1973. The Butterflies of Southern California. Natural History Museum of Los Angeles County Science Series No. 26. 

Garth, J. S. and J. W. Tilden. 1986. California Butterflies. California Natural History Guide 51. University of California Press, Berkeley and Los Angeles. 

Langston, R. L. 1981. The Rhopalocera of Santa Cruz Island, California. Journal of Research on the Lepidoptera 18: 24-35. 

Miller, Scott E. 1985. Butterflies of the California Channel Islands. Journal of the Research on the Lepidoptera 23: 282-296. 

Opler, Paul A. 1999. Peterson Field Guide to Western Butterflies, revised edition. Houghton Mifflin Co. , Boston, Mass. 

Orsak, L. J. 1977. The Butterflies of Orange County, California. Museum of Systematic Biology, University of California, Irvine. 

Stanford, R. E. and P. A. Opler. 1993. Atlas of Western USA Butterflies. Privately published, Denver, Colo.

Steiner, J. 1990. Bay Area Butterflies: The Distribution and Natural History of San Francisco Region

Rhopalocera. Hayward, Calif. : Hayward State University, Masters Thesis.

Tilden, J. W. and A. C. Smith. 1986. A Field Guide to Western Butterflies. Houghton Mifflin Co. , Boston, Mass.

Tilden, J. W. 1965. Butterflies of the San Francisco Bay Region. California Natural History Guide 12. University of California Press, Berkeley and Los Angeles.


The Xerces Society and Its Pioneering Work on Conservation

The Xerces Society is an international nonprofit organization dedicated to public education concerning invertebrates and the carrying out of conservation projects important to invertebrates' critical role in endangered ecosystems worldwide. The Society was named for the Xerces Blue (Glaucopsyche xerces), the first butterfly of North America documented to have been driven to extinction by the activities of man. The Society aims not only at informing the public about the importance of invertebrates (one of the largest and most significant segments of the world's biota), but also at strengthening the basis of worldwide conservation policy through scientific knowledge.

The Society is presently headquartered at 4828 SE Hawthorne Blvd. , Portland, Oregon 97215-3252 (phone 505-232-6639, fax 503-233-6794).  

"Mysterious and little-known organisms live within reach of where you sit.  
Splendor awaits in minute proportions
. . . "

- E. O. Wilson

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