El Segundo Blue Butterfly

Euphilotes battoides allyni

Description

The El Segundo blue butterfly is 0.8-1 in (20-25 mm) long. Males are bright blue above with black margins on their hindwings; females are dark brown above. Both sexes are light grayish below with black squares or spots and an orange band, bordered on both sides by a row of black dots. Formerly classified as Shijimiaeoides battoides allyni, this species is difficult to distinguish from other members of its genus.

Behavior

The El Segundo blue butterfly undergoes complete metamorphosis (egg, larva, pupa, and adult). The life span of this animal is about one year. Some pupae may remain in diapause for two or more years. The adults are active from mid-June to early September; the exact timing depending on the weather. The onset of flight is closely synchronized to the beginning of the flowering cycle of coast buckwheat, the food plant.

Upon emerging from their pupae, the female El Segundo blue butterflies fly to the flower heads of the food plant where they mate with males that constantly move from flower head to flower head. The females then immediately begin laying eggs. Laboratory data indicate females produce 15-20 eggs per day, but must continuously feed on nectar and pollen to maintain egg production. Although field data indicate females at the Chevron site in El Segundo live an average of four days in nature in captivity, females live two weeks and produce up to 120 eggs. Eggs hatch within three to five days. The discrepancy between longevity of adults in the field, 2.3-7.3 days and the laboratory, 16 day average, is most likely due to predation by crab and lynx spiders. These spiders were found at a frequency of about one per 200 flowerheads. One capture of a male El Segundo blue butterfly was observed during 15 person-hours of direct observations of flowerheads.

The larvae of the El Segundo blue butterfly undergo four instars before they pupate, a process that takes 18-25 days. The larvae maintain a symbiotic relationship with ants. The larvae develop glands and reversible tubes that produce a sweet secretion by the third instar, and are thereafter tended by various species of ants. The ants may protect the caterpillars from parasites and/or small predators. Mature larvae are highly polymorphic varying in color from almost pure white or pure dull yellow to strikingly marked individuals with a dull red-to-maroon background broken by a series of yellow or white dashes or chevrons. Larvae remain concealed within the flowerhead when feeding, the color pattern adding to their crypsis. The preferred part of the flowerhead are young seeds, which are consumed preferentially to other flowerparts. The latter are closely webbed together by the caterpillars giving the illusion of an intact flowerhead. One larva requires two or three flowerheads to complete development. By late September, the flowerheads have generally senesced and the larvae have pupated underground or in the leaf litter at the base of the food plants.

The egg population of the El Segundo blue butterfly is chiefly regulated by a parasitic wasp Trichogramma, which also attacks the eggs of the gray hairstreak butterfly and at least two species of micro-lepidopterous moths that also feed on buckwheat flowerheads.

Habitat

The El Segundo blue butterfly is only known from the El Segundo sand dunes. This habitat is a biologically sensitive and a unique environment, and is inhabited by a number of plant and animal species of special concern. The El Segundo sand dunes are the largest coastal sand dune system between the mouth of the Santa Maria River in Santa Barbara County and Ensenada in Mexico. The vegetation has been defined as the Sand verbena-beach bursage series in Sawyer and Keeler-Wolf. Native plants on the El Segundo sand dunes include coast buckwheat, dunes golden bush, dunes wall flower, dunes sun-cup, dunes burr-bush, and California croton.

It has an exclusive host relationship with wild buckwheat (Eriogonum parvifolium ), whose flowers provide a food source for the larvae and nectar for the adults. Habitat requirements for E. parvifolium include shifting, wind blown sand dunes. Plants supporting the highest concentration of larvae and adult butterflies are found in swales and on wind protected dune crests, which indicates that the slope and nature of the dunes are key environmental factors for the butterfly.

Distribution

Historically, this butterfly ranged throughout the El Segundo sand hills in Los Angeles County, California until as recently as several decades ago. Its habitat range has been reduced by development to two habitat patches in a 2-acre (0.81-hectare) preserve controlled by Chevron Oil near the Los Angeles airport. Prior to Chevron's agreeing to protect this area, it was greatly modified so that only a 500-foot wide corridor remained along the boundary of the dunes. However, wild buckwheat appears to be well-adapted to shifting sand dunes, and it and ice-plant restabilized in the remaining habitat. Because the wild buckwheat population is limited by the size of the habitat, the butterfly population is proportionately limited as well.

The El Segundo blue butterfly is now found only on remnants of the dune ecosystem, limited to a few acres of an oil refinery near El Segundo and to a larger area at the west end of the Los Angeles International Airport. Estimates of the number of individuals in these two ranges from 100-1,000 in any given year, equally divided with males and females. The population seems relatively stabile, but the limited number of hosts plants means that the butterfly population can never increase substantially within this restricted range.

Threats

All of the known populations of the El Segundo blue butterfly are under threat from various sources. Iceplant and other invasive exotic plants have degraded the sand dune habitat at the west side of the Ballona Wetlands. Non-native plants continue to invade the Airport Dunes. The small size and relatively low diversity of native plants threatens the butterfly at the Chevron reserve in El Segundo. Habitat destruction and invasive exotic plants pose a significant threat to the population at Malaga Cove.

The El Segundo dunes were undisturbed until the Spanish land grants development in the 1840s. Farming was then established on the coastal prairie to the east of the dunes, but generally started farther inland, probably because of agricultural unsuitability of the poorly drained sandstone soil near the backdune. The dunes themselves were undisturbed until the late 1880s when the cities from Redondo Beach to Venice were established, however, urban development was limited. Prior to that time, virtually the entire El Segundo dunes were in a pristine condition.

The city of Redondo Beach separated the main dunes from south Redondo Beach and the Malaga Cove extensions, and development of Venice eliminated the dunes north of the mouth of Ballona Creek. Conversion of the central part of the dunes was slower. Construction of the Chevron oil refinery in 1911 separated the dunes into two fragments. The southern fragment was gradually converted to homes starting at the beginning of the twentieth century and rapidly accelerated in the late 1940s. The natural habitat values in these areas were totally destroyed by the 1970s.

The Airport Dunes, the largest block of remaining natural habitat for the butterfly and other native species, was significantly reduced in quality and quantity between 1938 and 1992. However, the most substantive changes have taken place during the past 25 years. This has been as a result of the realignment of Pershing Drive, construction of Imperial Highway, moving sand to build a hill, and fragmentation and scraping of the coastal prairie. The habitat degradation resulted in extinction or extirpation of many native species and the invasion of the site by exotic plants and animals.

In 1928, the grid of streets on the Airport Dunes was constructed, but development was minimal following the 1929 stock market crash. Significant development did not take place until after the Second World War, with virtually the entire dunes built upon between 1946 and 1965. Nearly all of this area was privately owned. Construction of the Hyperion Sewage Treatment Plant and the Scattergood electrical plant in the 1940s, along with dense housing on the present Airport Dunes, reduced the northern fragment to about 80 acres of coastal sand dune habitat by 1960. The 1.6-acre (0.65-hectare) Chevron butterfly sanctuary site was isolated by residential development in the 1950s.

The most important events affecting the recent biological history of the Airport Dunes was the purchase and clearing of residences from nearly 200 acres between 1966 and 1972, which had resulted in the major contraction of native plants and animals in this area. A major adverse impact resulted from construction of the very high-frequency omni direction radio.

The Los Angeles Department of Airports currently is proposing to expand the Los Angeles International Airport (LAX). One alternative of the LAX 2015 Expansion Master Plan involves a physical intrusion onto the Dunes of graded areas associated with the end of a runway.

Of the 20 species of native terrestrial mammals recorded in 1938-40, most of which were present in 1975, only three are extant today. In their place are the introduced Norwegian rat, red fox, and opossum. Of 31 species of butterfly breeding on the site, seven have been extirpated. Of 18 species of reptiles and amphibians, seven have been extirpated and all five scrub dependent birds have disappeared from the Airport Dunes.

Ecosystem disturbance as a result of changes in the mammalian community has been profound as both rabbits and mice influence the differential reproductive efficiency of herbaceous plant species. The absence of mammalian foraging probably relaxed substantial pressure on seed banks, particularly European weeds. Loss of small mammals is linked to the introduction of the red fox, which themselves now have such limited food resources that they are driven to feeding on garbage, lizards, and even large insects.

During the late 1980s, off-road vehicles trespassed on the Airport Dunes, resulting in damage to El Segundo blue butterfly habitat and the native plant nursery. Areas containing sensitive cryptogamic crusts located on the backdunes at the Airport Dunes were badly damaged by human foot traffic in 1997. Cryptogamic crusts are formed in soils by blue green algae, lichens, mosses, fungi, and bacteria. They increase the ability of the soil to hold moisture, decrease its susceptibility to erosion, and apparently have higher levels of native versus exotic plant species.

Conservation and Recovery

The Los Angeles Airport has agreed to manage its dunes in cooperation with the Fish and Wildlife Service to benefit the El Segundo blue butterfly. The Chevron Corporation established a fenced sanctuary for the El Segundo blue butterfly on the grounds of its USA Refinery in 1983 and is currently managing the habitat for the butterfly's protection.

The Recovery Plan recommends the following steps:

1. Manage the habitat at the airport by removing exotic plants, implementing erosion control, establishing additional buckwheat populations, and controlling human access to the habitat.
2. Establish and protect a Dune Preserve Area at the airport, at a potential golf course habitat, and at the runway light area. Establishing these areas as suitable habitat includes removing exotic vegetation (the iceplant) and man-made structures and debris; planting native dune species; and introducing captive-bred blue butterflies.
3. Study the species life history and ecology to assess the loss from predation, parasitism, disease, and the effect of pollution created by the refinery, airport traffic, and use of herbicides and insecticides in the residential community; also study the propagation requirements and population genetics and incorporate that data into the recovery plan.

Contact

Regional Office of Endangered Species
U.S. Fish and Wildlife Service
911 NE 11th Avenue
Portland, Oregon 97232
http://pacific.fws.gov/

References

Arnold, R. A., and A. E. Goins. 1987. "Habitat Enhancement Techniques for the El Segundo Blue Butterfly: An Urban Endangered Species." In Adam and Leedy, eds., Integrating Man and Nature in the Metropolitan Environment. National Institute for Urban Wildlife, Columbia, Maryland.

U.S. Fish and Wildlife Service. 1978. "Sensitive Wildlife Information System-El Segundo Blue Butterfly." Report. U.S. Fish and Wildlife Service, Washington, D.C.

U.S. Fish and Wildlife Service. 1986. "Recovery Plan for the El Segundo Blue Butterfly." USFWS, Portland. 87pp.

U.S. Fish and Wildlife Service. 1998. "Recovery Plan for the El Segundo Blue Butterfly." USFWS, Portland. 78pp.