Blues: Palos Verdes blue (Glaucopsyche lygdamus palosverdesensis)

(Lepidoptera:Lycaenidae: Polyommatinae: Scolitantidini)

Profile prepared by Scott Hoffman Black and Mace Vaughan, The Xerces Society for Invertebrate Conservation

When it was listed as a federally endangered species in 1980, the Palos Verdes Blue was known from only three locations on the Palos Verdes Peninsula, a shrinking patch of coastal scrub community on the coast south of Los Angeles. By 1984, because of urban development and construction of the Hesse Park ballfield, the species was believed to have become extinct. In 1994, the butterfly was discovered at a site managed by the Department of Defense in south Los Angeles, renewing hopes for the survival of this species.

red list profile

conservation status

Xerces Society Red List Status: Critically Imperiled
Other Rankings:

Canada – Species at Risk Act: N/A
Canada – provincial status: N/A
Mexico: N/A
USA – Endangered Species Act: Endangered
USA – state status: None
NatureServe: G5T1
IUCN Red List: N/A

Since rediscovery in 1994 the number of adults each year has fluctuated between a low of 30 and a high near 300. Reintroduction of the butterfly to other restored sites is planned.

The Palos Verdes Blue was listed as a federal endangered species on 7/2/80 (Federal Register 45: 44939-44942). It currently does not have a recovery plan, but critical habitat was designated at the same time as it was listed.

Recovery Plan: None.

Critical Habitat: designated; Federal Register 45:44939-44942 (7/2/80).

The California Endangered Species Act does not allow listing of insects, so despite its precarious status, the Palos Verdes blue has no protection under state legislation. The California Department of Fish and Game includes this butterfly on its Special Animals list.

description and taxonomic status

The Palos Verdes Blue is in the family Lycaenidae (gossamer wings). It is a small butterfly with a wingspan between 25 and 30 mm. In the male, dorsal wing surfaces are colored a brilliant silvery-blue and outlined by narrow black borders. Dorsal wing surfaces of the female are brownish-gray in color, with a blue iridescence. In both sexes, the ventral wing surfaces are chalky gray in color, with several round spots highlighted by white rings.

Glaucopsyche lygdamus palosverdesensis E. M Perkins & J. Emmel, 1978.

life history

The Palos Verdes Blue is dependent on two known larval hostplants, Santa Barbara milkvetch (Astragalus trichopodus var. lonchus)—also known as locoweed—and common deerweed (Lotus scoparius). It has a single adult flight period extending from late January through mid-April. Eggs are normally laid in the flower heads of either deerweed or locoweed, where the caterpillars will feed. When the larvae are mature, they crawl into the leaf litter at or near the base of the food plant to find a place to pupate. They remain as pupae through the summer and winter, emerging as adult butterflies early the following spring.


The Palos Verdes Blue was thought to be restricted to the cool, fog-shrouded seaward side of the Palos Verdes Hills. Historically, its range extended over much of the Palos Verdes Peninsula, including the Department of Defense site where it was rediscovered.

threats and conservation needs

The Palos Verdes Peninsula is a small area of land hemmed in by the Pacific Ocean on three sides and Los Angeles on the fourth. It has been under increasing pressure of urban development, which has led to loss and degradation of the coast scrub habitat. Other factors causing the decline of this habitat, and the Palos Verdes Blue’s larval hostplant in particular, include weed control, off-road vehicle use, invasive non-native plants, and fire suppression.

The Defense Logistics Agency, Department of the Navy, The Urban Wildlands Group, Moorpark College, and Palos Verdes Peninsula Land Conservancy and various partners within the local community have restored habitat at a military fuel terminal located in an industrial area of the Palos Verdes Peninsula and at protected lands in the species range in preparation for reintroductions.

There is an active captive rearing program at the military base and at America’s Teaching Zoo at Moorpark College. In 2009, several thousand butterflies were in captivity with plans for releases into restored habitat on protected lands. Contact Dr. Travis Longcore (The Urban Wildlands Group; see contact details below) for more information.

A greater understanding of the impacts of recreation, weeds, and fire management on the butterfly’s habitat, especially on its larval hostplant, would be valuable.


Arnold, R. A. 1987. Decline of the endangered Palos Verdes Blue Butterfly in California. Biological Conservation 40(3):203-217.

Lipman, A., T. Longcore, R. Mattoni, and YinLan Zhang. 1999. Habitat Evaluation and Reintroduction Planning for the Endangered Palos Verdes Blue Butterfly. Report to California Fish and Game.(Accessed 9/22/08)

Longcore, T., R. Mattoni, A. Lipman, Z. Krenova, and C. Rich. 2002. Year 2002 Captive Rearing of Palos Verdes Blue Butterfly at Defense Fuel Support Point, San Pedro. The Urban Wildlands Group Defense Agency Agreement # N68711-02-LT-00010 17 pp. (Accessed 9/22/08)

Mattoni, R. 1995. Rediscovery of the endangered Palos Verdes blue butterfly, Glaucopsyche lygdamus palosverdesensis Perkins and Emmel (Lycaenidae). Journal of Research on the Lepidoptera 31(3-4):180-194. Available online (Accessed 4/13/05)

additional resources

U.S. Fish & Wildlife Service; Palos Verdes Blue Butterfly (Glaucopsyche lygdamus palosverdensis) 5-Year Review: Summary and Evaluation. March 2008.

NatureServe Explorer (Accessed 9/22/08)

University of California at Berkeley; Essig Museum of Entomology: California’s Endangered Insects, Palos Verdes Blue (Accessed 4/13/05)

Virginia Tech, Conservation Management Institute; Endangered Species Information System: Palos Verdes Blue Butterfly (Accessed 4/13/05)

San Diego State University, Soil Ecology and Research Group; Restoration Plan for the Proposed Palos Verdes Blue Management Area (Accessed 4/13/05)

The Urban Wildlands Group; Palos Verdes Blue Butterfly (Accessed 4/13/05)


Black, S. H., and D. M. Vaughan. 2005. Species Profile: Glaucopsyche lygdamus palosverdesensis. In Shepherd, M. D., D. M. Vaughan, and S. H. Black (Eds). Red List of Pollinator Insects of North America. CD-ROM Version 1 (May 2005). Portland, OR: The Xerces Society for Invertebrate Conservation.


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