Blues: mission blue (Icaricia icarioides missionensis)

(Lepidoptera: Lycaenidae: Polyommatinae: Polyommatini)

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

Formerly relatively widespread on the San Francisco and Marin peninsulas of northern California, the mission blue is now restricted to only a few sites. Preservation of existing butterfly populations relies on many factors common to butterfly conservation programs: replanting of the hostplant, removal of introduced plants, and protection from excessive recreational use and development. Probably the most important single location is San Bruno Mountain (San Mateo County), where two thousand acres of habitat are being managed by the county department of Parks and Recreation. A habitat conservation plan was developed for rare butterflies, including the Mission Blue, that occur at San Bruno Mountain. Much of the habitat of the mission blue occupies private lands that are slated for housing developments in the City of Pacifica General Plan.

red list profile

conservation status

Xerces 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

The Twin Peak’s population was re-discovered in 2001. Distribution of populations at San Bruno Mountain appear stable based on annual monitoring done as part of the San Bruno Mountain Habitat Conservation Plan, although the monitoring was done in a way that makes it impossible to estimate abundance nor gauge trends over time.

The mission blue was listed as a Federal Endangered Species on June 1, 1976 (Federal Register: 41:22044).

Recovery Plan (ESA): Final plan (San Bruno Elfin and Mission Blue Butterflies Recovery Plan) approved, 10/10/84
Critical Habitat (ESA): Proposed, 2/8/77 (Federal Register 42:7972-7976)

The California Endangered Species Act does not allow listing of insects, so despite its precarious status, the mission 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

Photo by Larry Orsak.

Please contact the Xerces Society for information on how to obtain permission to use this photo.


The mission blue is a small butterfly in the family Lycaenidae (gossamer wings). Wingspan is about 1 to 1.5 inch. The dorsal wing surfaces of the male are iridescent blue and lavender with black margins fringed with long white hair-like scales. There are no spots on the upper surfaces of the wings. In males, the ventral surfaces of the wings are whitish with small circular gray spots in the submarginal areas and larger circular black spots located in post- median and submedian areas of the fore and hind wings. The body of the male is dark bluish brown. Females have dark brown dorsal wing surfaces marked with blue basal areas. The margins and wing fringe are similar to the male. Female ventral wings are stone gray with a dot pattern similar to the males.

Taxonomic status

Icaricia icarioides missionensis (Hovanitz), 1937. This subspecies has previously been assigned to a different genus, Plebejus.

life history

The adult flight season extends from late March to early July, depending on the location and microclimatic conditions. The adults feed on hairy false goldenaster (Heterotheca villosa), bluedicks (Dichelostemma capitatum), and seaside buckwheat (Eriogonum latifolium), and do not wander far from the three species of lupine that are the larval food plant. These species are silver lupine (Lupinus albifrons), summer lupine (L. formosus), and manycolored lupine (L. versicolor). Females lay eggs throughout the mating flight. The eggs are laid singly on leaves, stems, flowers, and seed pods of lupine species.

Eggs hatch 4-7 days after being deposited. Young larvae feed on the inner tissues of the host plant leaves. After feeding, the small second instar larvae enter diapause in the litter at the base of the host plant. Larvae emerge from diapause and resume feeding the following spring. The mechanisms that start and end diapause are unknown. Third and fourth instar larvae are tended by ants. These instars have well-developed glands that secrete a sugar- and protein-rich substance, commonly called honeydew, that entices ants into this tending behavior. Pupation occurs in the soil beneath the host plant. One generation of butterflies is produced each year.

Colonies are located at sites ranging from 690 to 1,180- foot elevation. Some colonies occur in the fog belt of the coastal range. Coastal chaparral and coastal grasslands dominate the vegetation type where colonies are found.


The mission blue was first collected in 1937 from the Mission District of San Francisco. Today a small colony survives on Twin Peaks, symbolic as the type locality for this butterfly. The majority of the remaining colonies are found on San Bruno Mountain, San Mateo County. Other colonies have been discovered in San Mateo County and the butterfly has also been collected from Fort Baker, Marin County.

threats and conservation needs

The biggest threat is the loss of existing habitat to development, particularly on San Bruno Mountain where parts of the area are already slated for development and there is constant pressure for more. Associated with this development is the increase in recreation that accompanies growing populations of human residents. Trampling of habitat is already a problem for the Twin Peaks site. Vegetation changes due to altered management and invasive plants also reduce the quality of remaining habitat. The Habitat Conservation Plan process is intended to limit pressure on important habitat by defining where development is suitable and ensuring habitat of adequate quality and area remains.

Most of the butterflies are on private land so some sort of landowner education as well as safe harbor agreements may be appropriate.

Surveys and monitoring of known colonies, using survey methodologies that provide both distribution and abundance data should continue. Searches for potential habitat within the historic range should be done. Studies evaluating changes to habitat due to development and recreation pressures would be valuable, as would studies evaluating the impacts of management actions.


Arnold, R. A. 1980. Ecological studies on six endangered butterflies (Lepidoptera: Lycaenidae); island biogeography, patch dynamics, and the design of habitat preserves. Berkeley, CA: University of California at Berkeley. Ph.D. dissertation.

________. 1983. Ecological studies of six endangered butterflies (Lepidoptera, Lycaenidae): island biography, patch dynamics, and design of habitat preserves. University of California Publications in Entomology 99:1-161.

Downey, J. C. 1957. Infraspecific variation and evolution in populations of Plebejus icarioides (Bdv.). Davis, CA: University of California at Davis. Ph.D. dissertation.

Longcore, T., C. S. Lam, and J. P. Wilson. 2004. Analysis of Butterfly Survey Data and Methodolgy from San Bruno Mountain Habitat Conservation Plan (1982-2000). 1. Status and Trends. University of Southern California GIS Research Laboratory and Center for Sustainable Cities, Los Angeles, CA. (Available on Urban Wildlands Group website Accessed 3/25/05.)

Orsak, L. J. 1982. The endangered Mission Blue butterfly of California—indicator of an imperiled natural ecosystem. Xerces Society Educational Leaflet 8. The Xerces Society, Portland, OR. (Text available on San Bruno Mountain Watch website Accessed 4/5/05.)

Thelander, C. (ed.). 1994. Life on the edge: a guide to California’s endangered natural resources. Santa Cruz, CA: BioSystem Books.

U.S. Fish and Wildlife Service. 1984. San Bruno Elfin and Mission Blue Butterflies Recovery Plan. Portland, Oregon.

additional resources

Recovery plan

U.S. Fish & Wildlife Service, Endangered Species Program; Mission Blue Butterfly (Accessed 4/5/05)

U.S. Fish & Wildlife Service, Sacramento Fish And Wildlife Office; Species account: Mission Blue Butterfly (Accessed 4/5/05)

NatureServe Explorer (Accessed 9/22/08)

University of California at Berkeley, Essig Museum of Entomology; California’s Endangered Insects: Callippe Silverspot Butterfly (Accessed 4/5/05)

Virginia Tech, Conservation Management Institute; Endangered Species Information System: Mission Blue Butterfly (Accessed 4/5/05)


Black, S. H., and D. M. Vaughan. 2005. Species Profile: Icaricia icarioides missionensis. 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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