The San Bruno elfin (''Callophrys mossii bayensis'') is a U.S. federally listed

endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching, inv ...

subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...

that inhabits rocky outcrops and cliffs in coastal scrub on 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, ...

. It is

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

to this habitat in

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 ...

. Its patchy distribution reflects that of its host plant, broadleaf stonecrop (''Sedum spathulifolium'').

Life cycle

Adults of this

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 ...

emerge in February and March, when

nectar Nectar is a viscous, sugar-rich liquid produced by Plant, plants in glands called nectaries, either within the flowers with which it attracts pollination, pollinating animals, or by extrafloral nectaries, which provide a nutrient source to an ...

providing flowers open. After mating, the female locates host plants on which to deposit her eggs, which hatch within a week. The tiny

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 ...

e first feed on the plant's vegetative structures; however, when the

stonecrop ''Sedum'' is a large genus of flowering plants in the family Crassulaceae, members of which are commonly known as stonecrops. The genus has been described as containing up to 600 species, subsequently reduced to 400–500. They are leaf succulen ...

's flowers begin to open, the larvae migrate upward and feed on the flowers themselves. By June most have completed their larval development at which time they evacuate from the host plant to

pupate A pupa (; : pupae) is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their life cycle, the stages the ...

in ground litter. They lie dormant as pupae until the following spring, when the

life cycle Life cycle, life-cycle, or lifecycle may refer to: Science and academia *Biological life cycle, the sequence of life stages that an organism undergoes from conception to reproduction *Life-cycle hypothesis, in economics *Erikson's stages of psy ...

begins anew. The San Bruno elfin's life cycle holds an interesting aspect, common to many other lycaenids regarding a

symbiotic Symbiosis (Ancient Greek : living with, companionship < : together; and ''bíōsis'': living) is any type of a close and long-term biolo ...

interaction with

ant Ants are Eusociality, eusocial insects of the Family (biology), family Formicidae and, along with the related wasps and bees, belong to the Taxonomy (biology), order Hymenoptera. Ants evolved from Vespoidea, vespoid wasp ancestors in the Cre ...

s. Elfin larvae excrete a sweet liquid known as honeydew which attracts ants. In exchange for honeydew, the ants often provide protection from harm by

predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

s and

parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...

s, which are principal killers of foliage feeding insects.

Range and habitat

The San Bruno elfin is restricted to a few small

population Population is a set of humans or other organisms in a given region or area. Governments conduct a census to quantify the resident population size within a given jurisdiction. The term is also applied to non-human animals, microorganisms, and pl ...

s, the largest of which occurs on

San Bruno Mountain San Bruno Mountain is a fault block, fault-block Horst (geology), horst in northern San Mateo County, California. Rising to a quarter-mile high peak directly out of San Francisco Bay, it also includes a smaller ridge in San Francisco. Viewed f ...

. Most of these areas, akin to the distribution of the host plant, are scattered on rocky slopes and ledges, especially east facing (McClintock, 1968). One of these niches is in the vicinity of the old quarry. Its

habitat In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...

has been diminished in the past by

quarry A quarry is a type of open-pit mining, open-pit mine in which dimension stone, rock (geology), rock, construction aggregate, riprap, sand, gravel, or slate is excavated from the ground. The operation of quarries is regulated in some juri ...

ing,

off-road Off-roading is the act of driving or riding in a vehicle on unpaved surfaces such as sand, dirt, gravel, riverbeds, mud, snow, rocks, or other natural terrain. Off-roading ranges from casual drives with regular vehicles to competitive events w ...

recreational vehicles A recreational vehicle, often abbreviated as RV, is a motor vehicle or trailer that includes living quarters designed for accommodation. Types of RVs include motorhomes, campervans, coaches, caravans (also known as travel trailers and camp ...

, and urban development as land development pressure on the San Francisco Peninsula continues to fester. To protect the rare San Bruno elfin as well as the

Mission blue butterfly The Mission blue (''Icaricia icarioides missionensis'') is a blue or lycaenid butterfly subspecies native to the San Francisco Bay Area of the United States. The butterfly has been declared as endangered by the US federal government. It is a s ...

a unique habitat management plan has been implemented on

, in which the lower slopes were opened for development while the higher areas were converted to public ownership as critical habitat. This strategy arose as a compromise result of years of conflict between

land developer Land development is the alteration of landscape in any number of ways, such as: * Changing landforms from a natural or semi-natural state for a purpose such as agriculture or housing * Subdividing real estate into lots, typically for the purpo ...

s and conservationists regarding this unique piece of real estate, jointly prized for its outstanding habitat features and its economically valuable location. Current management on San Bruno Mountain and in other areas focuses on reduced

pesticide Pesticides are substances that are used to control pests. They include herbicides, insecticides, nematicides, fungicides, and many others (see table). The most common of these are herbicides, which account for approximately 50% of all p ...

use, careful recreation management, and vegetation management. Several areas from which populations had been previously

extirpated Local extinction, also extirpation, is the termination of a species (or other taxon) in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global extinctions. Local extinctions mark a chan ...

are also being targeted for

revegetation Revegetation is the process of replanting and rebuilding the soil of disturbed land. This may be a natural process produced by plant colonization and succession, manmade rewilding projects, accelerated process designed to repair damage to a la ...

and reintroduction of the butterfly. Another population of San Bruno elfin is known to be established in Montara, on coastal bluffs about 25 miles (40 kilometers) south of San Bruno Mountain (Alling, 1986). This colony is near the

Fitzgerald Marine Reserve Fitzgerald Marine Reserve is a marine reserve in California on the Pacific Ocean, located just north of Pillar Point Harbor and Mavericks in the San Mateo County community of Moss Beach. Moss Beach is located approximately south of San Franci ...

. A third colony is found near Rockaway Beach, California in Pacifica.

References

* Brown, R.M., "Larva and habitat of ''Callophrys fotis bayensis''" ''Journal of Research on the Lepidoptera'' 8: 49-50 (1969) * Curtis E. Alling, Michael Hogan, Lynn Alexander, et al., "Environmental Impact Report for the West Rockaway Beach Redevelopment Plan prepared for the city of Pacifica", Earth Metrics Incorporated, SCH #85127017, March, 1986 * Elizabeth McClintock and Walter Knight, ''A Flora of the San Bruno Mountains, San Mateo County, California'', Proceedings of the California Academy of Sciences, Fourth Series, Volume XXXII, no. 20, pp. 587–677, November 29, 1968 * Emmel, J.F. and C.D. Ferris, "The biology of ''Callophrys'' (''Incisalia'') ''fotis bayensis'' (Lycaenidae)" ''Journal of the Lepidopterists' Society'' 26 (4): 237-244 (1972) {{Taxonbar, from=Q7413488 Callophrys

San Bruno San Bruno () is a city in San Mateo County, California, United States, incorporated in 1914. The population was 43,908 at the 2020 United States census. The city is between South San Francisco and Millbrae, adjacent to San Francisco Internat ...

Endemic fauna of California

Natural history of San Mateo County, California

Fauna of the San Francisco Bay Area Critically endangered insects ESA endangered species Butterfly subspecies