Myrtle's silverspot (''Speyeria zerene myrtleae'') is a medium-sized

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 brush foot family (

Nymphalidae The Nymphalidae are the largest family of butterflies, with more than 6,000 species distributed throughout most of the world. Belonging to the superfamily Papilionoidea, they are usually medium-sized to large butterflies. Most species ha ...

), an

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 ...

of the zerene fritillary. 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 ...

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 ...

, where it is known from only about four locations just north of the

San Francisco Bay Area The San Francisco Bay Area, commonly known as the Bay Area, is a List of regions of California, region of California surrounding and including San Francisco Bay, and anchored by the cities of Oakland, San Francisco, and San Jose, California, S ...

, including two at

Point Reyes National Seashore Point Reyes National Seashore is a park preserve located on the Point Reyes, Point Reyes Peninsula in Marin County, California. As a national seashore, it is maintained by the US United States National Park Service, National Park Service as an ...

.Habitat Assessment of Myrtle's Silverspot Butterfly at Point Reyes National Seashore
/ref> Its wingspan is approximately . The upper surfaces of the wings are golden brown with numerous black spots and lines. The undersides are brown, orange and tan with black lines and silver and black spots.

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 are dark colored with many sharp branching spines on their backs. Myrtle's silverspot is larger and paler than the closely related Behrens' silverspot (''Speyeria zerene behrensii''), which is now limited to the vicinity of

Point Arena Point Arena, formerly known as Punta Arena (Spanish for "Sandy Point") is a small coastal city in Mendocino County, California, United States. Point Arena is located west of Hopland, at an elevation of . The population was 460 at the 2020 cen ...

Mendocino County Mendocino County (; ''Mendocino'', Spanish language, Spanish for "of Antonio de Mendoza, Mendoza") is a County (United States), county located on the North Coast (California), North Coast of the U.S. state of California. As of the 2020 United S ...

.USFWS
Species Account: Myrtle's Silverspot Butterfly
/ref> Myrtle's silverspot is also closely related to the Oregon silverspot (''

Speyeria zerene hippolyta ''Speyeria zerene hippolyta'', the Oregon silverspot, is a threatened butterfly that is found in the U.S. states of California and Oregon. It is a subspecies of '' Speyeria zerene''. Taxonomy ''Speyeria zerene hippolyta'' was described by Ame ...

).'' The female lays a single brood of eggs in the dried herbage of violets, especially western dog violet (''Viola adunca''), the only known larval food plant. Upon hatching, the caterpillars wander a short distance and spin

silk Silk is a natural fiber, natural protein fiber, some forms of which can be weaving, woven into textiles. The protein fiber of silk is composed mainly of fibroin and is most commonly produced by certain insect larvae to form cocoon (silk), c ...

pads upon which they pass the winter. The larvae immediately seek out the food plant at the end of their

diapause In animal dormancy, diapause is the delay in development in response to regular and recurring periods of adverse environmental conditions.Tauber, M.J., Tauber, C.A., Masaki, S. (1986) ''Seasonal Adaptations of Insects''. Oxford University Press It ...

in the spring. After 7 to 10 weeks each larva

pupa 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 th ...

tes within a chamber of leaves it glued together with silk. Adults may emerge in about 2 weeks and can live for 3 weeks. The adult flight season may range from late June to early September. Adults feed on nectar from flowers including gumplants (''Grindelia'' spp.), yellow sand verbena (''Abronia latifolia''), coyote mints (''Monardella'' spp., especially '' M. undulata''),

bull thistle ''Cirsium vulgare'', commonly known as spear thistle, bull thistle, or common thistle, is a species of the Asteraceae genus ''Cirsium'', native throughout most of Europe (north to 66°N, locally 68°N), Western Asia (east to the Yenisei Valley) ...

(''Cirsium vulgare'') and seaside daisy (''Erigeron glaucus'').

Habitat

Myrtle's silverspot is found in

sand dune A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, flat ...

and coastal prairie habitat. Populations were formerly found in dunes and bluffs from

San Mateo County San Mateo County ( ), officially the County of San Mateo, is a county (United States), county located in the U.S. state of California. As of the 2020 United States census, the population was 764,442. Redwood City, California, Redwood City is th ...

north to the mouth of the Russian River in

Sonoma County Sonoma County ( ) is a county located in the U.S. state of California. As of the 2020 United States census, its population was 488,863. Its seat of government and largest city is Santa Rosa. Sonoma County comprises the Santa Rosa-Petaluma ...

. The populations south of the

Golden Gate The Golden Gate is a strait on the west coast of North America that connects San Francisco Bay to the Pacific Ocean. It is defined by the headlands of the San Francisco Peninsula and the Marin Peninsula, and, since 1937, has been spanned by ...

apparently have been

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 ...

by urban development. Four populations are known to inhabit coastal terrace prairie, coastal bluff scrub, and associated non-native grassland habitats in western

Marin Marin or Marín (Italian "sailor") may refer to: People * Marin (name), including a list of persons with the given name or Italian surname. * MaRin, in-game name of professional South Korean ''League of Legends'' player Jang Gyeong-hwan (born 19 ...

and southwestern Sonoma counties, including Point Reyes. Adult butterflies are typically found in areas that are sheltered from the wind, below elevation, and within of the coast.

Conservation

The butterfly was listed as an

endangered species 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 ...

in 1992. Habitat loss due to residential and commercial land development has extirpated these butterflies from parts of their range and may threaten some of the remaining populations. Maintaining larval and nectar plants is critical for conservation of these butterflies. Changes in natural fire patterns, introduction of

exotic plants An introduced species, alien species, exotic species, adventive species, immigrant species, foreign species, non-indigenous species, or non-native species is a species living outside its native distributional range, but which has arrived ther ...

, and successional changes in the plant community have reduced the availability of host plants. Either excessive or inadequate

grazing In agriculture, grazing is a method of animal husbandry whereby domestic livestock are allowed outdoors to free range (roam around) and consume wild vegetations in order to feed conversion ratio, convert the otherwise indigestible (by human diges ...

activity can result in plant communities unfavorable to the butterflies. Measures for habitat improvement may include eradication of invasive exotics such as iceplant (''

Mesembryanthemum ''Mesembryanthemum'' is a genus of flowering plants in the family Aizoaceae, indigenous to southern Africa. As with many members of that family, it is characterized by long-lasting flower heads. Flowers of ''Mesembryanthemum'' protect their game ...

'' spp.) and identifying appropriate grazing and/or burning regimes in grassland and scrub areas. These butterflies are highly prized by insect collectors, and are vulnerable due to their small population. Silverspot butterfly larvae are also extremely sensitive to

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 ...

Habitat

Conservation

References

Further reading