Mission blue butterfly

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Mission blue butterfly

Conservation status

Critically Imperiled (TNC)
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Lepidoptera
Family: Lycaenidae
Subfamily: Danainae
Genus: Icaricia
Species: I. icarioides
Subspecies: I. icarioides missionensis
Trinomial name
Icaricia icarioides missionensis
Hovanitz, 1937
Synonyms

Plebejus icarioides missionensis (Hovanitz, 1937)

The mission blue butterfly, Icaricia icarioides missionensis, is a blue or lycaenid butterfly subspecies that is native to the San Francisco Bay Area of the United States. The butterfly has been declared as endangered by the Federal Government. It is sometimes placed in the genus Plebejus.

Contents

[edit] Description

The brownish-colored female mission blue butterfly
The brownish-colored female mission blue butterfly
The iridescent blue male mission blue butterfly
The iridescent blue male mission blue butterfly

The endangered mission blue is about the size of a quarter (21–33 mm) with even smaller larvae which are very rarely seen. Its wingspan is around 1–1½ inches. The top wing, in mission blue males, is iridescent blue and lavender. The margins of the upper wing are black and sport "long, white, hair-like scales." The male butterfly also has small circular gray spots in the submargins on the ventral surface of the whitish ventral wing surface. In the post-median and submedian areas of the ventral surface black spots mark the upper and lower wing. The male body is a dark-blue/brown color.[1]

The female mission blue have a dark brown upper wing that are marked with blue basal areas. The margins of the wing fringe are very similar to those on the male of the species. The underside of the wing on the female butterfly are gray with a dot pattern that is, again similar to that on the male.[1]

The larvae will only feed on the leaves of the three host lupine plants (Lupinus albifrons, L. formosus, and L. variicolor) native to their habitat. The plants are necessary for survival for the mission blue. Thus, the butterfly's fate is closely tied to that of the three species of lupine as the plants provide food and shelter for the butterfly in its larval stage. The adult mission blue drinks the nectar of a variety of flowers, many in the sunflower family, using its long proboscis which extends from the underside of its head.[2]

In the 1983 study "Six Ecological Studies of Endangered Butterflies", R. A. Arnold found that about 35% of eggs collected in the field were being parasitized by an unknown encryrtid wasp. Other parasitic Hymenoptera have been taken from the eggs of various Icarioides species. As far as predator-prey relationships, rodents are probably the primary predator of both the larvae and pupae.[3]

[edit] Habitats

The mission blue depends on a very specific host plant called the lupine. As such, its habitat is restricted solely to the U.S. state of California. More specifically, it is limited to a range of five known areas where mission blue colonies have been confirmed. Those areas are subject to a range of conservation and habitat restoration action.

[edit] Range

I. i. missionensis is federally endangered and found in only a few locations. Its habitat is restricted to the San Francisco Bay Area, specifically five areas, the Twin Peaks area in San Francisco County, Fort Baker, a former military installation managed by the National Park Service (NPS), in Marin County, the San Bruno Mountain area in San Mateo County, the Marin Headlands, in Golden Gate National Recreation Area (another NPS entity) and Skyline Ridge, also in San Mateo County.[4] San Bruno Mountain hosts the largest population of mission blues, a butterfly that is commonly found around elevations of 700 feet. The coastal scrubland and grassland the mission blue requires is found only in and around the Golden Gate of San Francisco. The butterfly depends solely on three species of perennial lupine for its reproduction, the varied lupine, silver lupine and the Summer lupine. The mission blue requires the lupine to lay their eggs and nourish the larvae. Without these species, the mission blue cannot reporduce and thus cannot survive.[3] Thus, the mission blue's habitat parallels that of the lupine species.

Two of the areas inhabited by the mission blue are within the confines of the Golden Gate National Recreation Area. Golden Gate staff are working to ease the invasive species problem that has helped reduce the mission blue to the endangered species list. They work to remove non-native plants and replant the area with lupine seed along with continual monitoring of the butterfly and its host plant.[5]

Much of the area that the mission blue once inhabited has been destroyed. The coastal scrubland has seen unnatural human development in much of the region. The San Mateo County town of Brisbane lies in what may once have been the prime habitat for the butterfly. Near Brisbane, an industrial park and rock quarry have proved damaging to the mission blue habitat. Generally, the most negative impactor on Mission blue habitat is that of residential and industrial development. Aside from development, other human activities have negatively impacted the butterfly's habitat. Those activities include cultivation and grazing as well as the oft human assisted abundance of invasive exotic species. Some of the more impactful exotics include the European gorse and pompous grass.[3] In the Golden Gate Recreation Area, thoroughwort is a particular invasive species which is taking over habitat once occupied by the mission blue's lifeblood, the three species of lupine.[5] Of the threats facing the mission blue, habitat loss due to human intervention and exotic, invasive species are the two most critical.

Residential and industrial development continually threaten mission blue habitat, such as the 1997-2001 seismic retrofitting of the Golden Gate Bridge. Despite costing and additional US$1.2 million to comply to environmental standards the construction project still claimed about 1,500 square metres of butterfly habitat through "incidental take," an exception provided under California law. Through a type of habitat conservation popular since a 1983 amendment to the Endangered Species Act, the incidental take is offset by off-site mitigation and restoration. In this case, the San Francisco Highway and Transportation District in cooperation with the National Park Service funded a US$450,000 off-site restoration plan. The main aspect of this plan was to establish about 8 ha of mision blue habitat in the area of the bridge project.[6]

The mission blue butterfly was first collected in the Mission District of San Francisco in 1937. Today, there is a small colony on Twin Peaks; the species has also been found in Fort Baker, which is in Marin County. However, the majority of today's Mission blue colonies are found on San Bruno Mountain. Besides those on the mountain, other colonies have been found in San Mateo County. Those colonies have been located at elevations of 690–1,180 ft. Some colonies have been found in the "fog belt" of the coastal mountain range. The mission blue colonies in the area prefer coastal chaparral and coastal grasslands which are the predominate biomes where mission blues are found.[1]

[edit] Status

The mission blue butterfly was added to the Federal Endangered Species List in 1976, its protection falls under the jurisdiction of the federal Endangered Species Act.[4] While the state of California has enacted an Endangered Species Act, it is quite specific about what affords its protection. Sec. 2062 of the California Endangered Species Act, under definitions, declares, "Endangered species" means a native species or subspecies of a bird, mammal, fish, amphibian, reptile, or plant which is in serious danger of becoming extinct." There is no provision for a state endangered listing in California for any insect. The mission blue butterfly is not protected by state statute in California.[7]

[edit] Life cycle

Each year marks the birth of a new generation of mission blues, as only one generation exists per year. The butterfly lays its eggs on the leaves, buds and seed pods of L. albifrons, Lupinus formosus and Lupinus variicolor.[8] The eggs are usually laid on the dorsal side of new lupine leaves. Eggs generally hatch within six to ten days and the first and second instar larvae feed on the mesophyll of the lupine plants.[4] The caterpillars, extremely small, feed for a short time and then crawl to the plant base where they enter a dormant state, known as diapause, until the late winter or the following spring. Diapause usually begins about three weeks after eclosion and begins about the same time as the host plant shifts its energy to flower and seed production.[4] When the caterpillar comes out of its diapause and begins feeding, it occasionally sheds its skin to accommodate its growth.[8]

As the larvae feed and grow, native ants may gather and indicate the presence of larger mission blue larvae. The ants will often stand on the caterpillar and tap it with their antennae. In response, the caterpillar secretes honeydew. The ants eat honeydew and in return it is likely, through this symbiotic relationship, that the ants ward off predators. Once the caterpillar is fully grown, it leaves the larval stage and enters the pupal stage of development. The fully grown caterpillar forms a chrysalis after securing itself to a surface which is generally a lupine stem or leaf. They shed their outer skin, revealing their chrysalid. This stage lasts about ten days while the adult butterfly develops within the chrysalid. The butterfly can be sighted as early as late March in places like the summit of San Bruno Mountain or the Twin Peaks. They persist well into June when they will be seen perched on a lupine plant or feeding on coastal buckwheat flowers.[8] Day to day for the adult butterfly is mostly spent foraging for nectar, flying, mating and for the females, laying eggs. Nearly equal time is spent between perching, feeding and flying.[3] The adult mission blue lives approximately one week; during this time, the females lay the eggs on the host plant. The complete mission blue butterfly life cycle lasts one year.[4]

[edit] Host plants

The varied lupine, Lupinus variicolor
The varied lupine, Lupinus variicolor
The silver lupine, Lupinus albifrons
The silver lupine, Lupinus albifrons
The summer lupine, Lupinus formosus
The summer lupine, Lupinus formosus

See main article lupin.

The mission blue butterfly is entirely dependent upon three species in the genus Lupinus.

[edit] Lupinus albifrons

A lupine seedling at the site of a 2004 California wildfire
A lupine seedling at the site of a 2004 California wildfire

L. albifrons, or silver lupine, sometimes known as silver bush lupine, is one of the lupine species that acts as the host plant for the larvae and pupae of the mission blue butterfly. It is a small, round shrub, with a woody trunk. A deciduous perennial, the plant takes up about 2 ft (0.61 m) of space and can reach heights of 5 ft (1.5 m) It blooms a light blue to violet flower on 3–12 in stalks. The leaves are a silver color with a feathery texture. The silver lupine is found along the coasts of Oregon and California, as well as in dry and open meadows, prairies and forest clearings in those states. Lupinus albifrons is a legume and thus it has nitrogen-fixing nodules on its roots.[9]

The silver lupine has five different varieties, three of which occur only in California, the other two occur in both California and Oregon. The five varieties are: Lupinus albifrons var. albifrons, silver lupine, Lupinus albifrons var. collinus, silver lupine, Lupinus albifrons var. douglasii, Douglas' silver lupine, Lupinus albifrons var. eminens, silver lupine, and Lupinus albifrons var. flumineus, silver lupine.[10]

[edit] Lupinus formosus

L. formosus has been cited as a poisonous plant. Its common name is summer lupine. Because of its toxological status it faces eradication at the hands of cattle farmers as it has been implicated in crooked calf disease, though it is not endangered. This lupine, along with five others, is poisonous from the time it starts growth in the spring until the seed pods shatter in late summer or early fall. However, the younger the plant the more toxic it is.[11]

Summer lupine is one of three piperidine alkaloid containing plants that have poisonous effects on livestock. It, along with poison hemlock (Conium maculatum) and tree tobacco (Nicotiana glauca), induced "multiple congenital contractures (MCC) and palatoschisis in goat kids when their dams were gavaged with the plant during gestation." The skeletel abnormalities included fixed extension of the carpal, tarsal and fetlock joints, scoliosis, lordosis, torticollis and rib cage problems. The clinical signs of toxicity in sheep, cattle and pigs included, ataxia, incoordination, muscular weakness, prostration and death.[12]

The summer lupine is part of the Fabaceae family. It inhabits areas of dry slopes beneath pine trees, clay soils, grasslands, coniferous forests, and areas in the San Jacinto, Santa Rosa and San Gabriel Mountains. This lupine blooms from April to August.[13]

[edit] Lupinus variicolor

L. variicolor is known by several common names including varied lupine, manycolored lupine, Lindley's varied lupine and varicolored lupine. Its range is restricted to the northern coastal scrub and coastal prairie in the U.S. state of California. It thrives in elevations between 0 and 1,640 ft (500 m) Another member of the Fabaceae family, it is a shrub. L. variicolor is endemic and native to only the U.S. state of California where it occurs mostly along the northern coast, though it has been reported in Sutter County, California.[14]

[edit] Other information

[edit] Evolution

Main article: Butterfly evolution

The Theolinae evolved in a tropical climate while the Lycaenidae and Icaricia evolved in a temperate climate zone. The genus Icaricia comprises 12 species. They are, I. icarioides, I. evius, I. moroensis, I. missionensis, I. padalis, I. pheres, I. ardea, I. lycea, I. bucholzi, I. pembina, I. blackmorei, and I. montis.[3] The genus Icaricia was introduced in a 1944 paper by Vladimir Nabokov. The paper, Notes on the morphology of the genus Lycæides (Lycænidæ, Lepidoptera), was published in the Sep.-Dec. issue of Psyche—A Journal of Entomology and described two new genera, Icaricia and Plebulina.[15]

[edit] Taxonomy

Its trinomial name is Icaricia icarioides missionensis, however the species used to be classified as a subspecies in the genus Plebejus (Pelbius). The mission blue is classified as a subspecies of Boisduval's blue (formerly Plebejus (Plebius) icarioides, now Icaricia icarioides), the nomenclature for the mission blue as late as 2000 was Plebejus (Plebius) icarioides missionensis.[16] It is still a subspecies of Boisduval's blue.

[edit] Habitat conservation

Main article: Mission blue butterfly habitat conservation

The U.S. Fish and Wildlife Service (USFWS) has a number of habitat conservation programs in effect which includes lands traditionally inhabited by the mission blue butterfly. A recovery plan, drawn up by the U.S. Fish and Wildlife Service in 1984, outlined the need to protect mission blue habitat and to repair habitat damaged by urbanization, off highway vehicle traffic, and invasion by exotic, non-native plants.[3] An example of the type of work being done by governmental and citizen agencies can be found in the Marin Headlands at Golden Gate National Recreation Area. In addition, regular wildfires have opened new habitat conservation opportunities as well as damaging existing ones.

[edit] References

  1. ^ a b c Mission Blue Butterfly, Species Account, USFWS, Sacramento Office
  2. ^ Mission Blue Butterfly, Wildlife Field Guide, National Parks Labs
  3. ^ a b c d e f The Biogeography of the mission blue butterfly, San Francisco State University, Department of Geography, Autumn 2000
  4. ^ a b c d e Mission Blue Butterflies, Golden Gate National Parks Conservancy
  5. ^ a b Restoration after Solstice Fire Reduces Fuel and Improves Grassland Health (PDF), Golden Gate National Recreation Area. 
  6. ^ Giacomini, Mervin C. and Woelfel, John E. Golden Gate Update, Civil Engineering Magazine, Nov. 2000
  7. ^ California Endangered Species Act, CA Dept. of Fish and Game, Habitat Conservation Planning Branch
  8. ^ a b c Orsak, Larry J. Mission Blues, San Bruno Mountain Watch
  9. ^ The Biogeography of the silver bush lupine, San Francisco State University
  10. ^ Plant Profile, Silver Lupine, Natural Resources Conservation Service, U.S. Department of Agriculture
  11. ^ Lupine, Agricultural Research Service, U.S. Department of Agriculture
  12. ^ Abstract (multiple authors) "Congenital skeletal malformations and cleft palate induced in goats by ingestion of Lupinus, Conium and Nicotiana species", USDA/ARS/Poisonous Plant Research Laboratory, Logan, UT
  13. ^ Lupinus formosus, Calflora Database
  14. ^ Lupinus variicolor, Calflora Database
  15. ^ Excerpts from: Zimmer, Deiter E. A Guide to Nabokov's Butterflies and Moths, Penn State University Libraries
  16. ^ Family Lycaenidae, North American Butterfly Association

[edit] Further reading

[edit] Conservation

[edit] Legislation

[edit] Endangered Species Act

[edit] Other laws

[edit] Litigation

[edit] News/Media

[edit] Miscellaneous