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Lotis Blue Butterfly

Lotis Blue Butterfly

Lycaeides argyrognomon lotis

Status Endangered
Listed June 1, 1976
Family Lycaenidae (Gossamer-winged butterfly)
Description Small butterfly; males are violet-blue, females brown.
Habitat Wet meadows and sphagnum-willow bogs.
Host plant Coast trefoil.
Reproduction Females lay eggs during the adult flight season (mid-April to early June).
Threats Habitat destruction.
Range California


The lotis blue butterfly, Lycaeides argyrognomon lotis has a wingspan of 0.6-1.3 in (1.5-3.3 cm). The upper wing surfaces are a deep violet-blue in the male with a black border and fringe of white scales along the outer wing margins. In the female, the upper wing surface is brown, sometimes bluish-brown, with a wavy band of orange on both forewings and hindwings. The lotis blue is one of 12 subspecies of L. argyrognomon in North America.


The life history of the lotis blue butterfly is not well studied, but some information can be extrapolated from closely related species. The larval host plant is most likely the coast trefoil (Lotus formosissimus ). Females lay eggs on the host plants during the adult flight season from mid-April to early June, and newly hatched larvae begin feeding immediately on leaves, flowers, and seedpods. Larval dia-pause (the resting stage during larval development) is broken sometime during the following spring, and larvae complete their development four to six weeks later. The pupal stage probably lasts no more than a few weeks.


The lotis blue butterfly is found in wet meadows or poorly drained sphagnum-willow bogs, where soils are waterlogged and highly acidic. This habitat has a dense undergrowth of shrubs, including California huckleberry, western Labrador tea, salal, wax myrtle, California rose-bay, western hemlock, and Sitka spruce.


The lotis blue butterfly appears to be a naturally rare insect with low population densities. In the past, it was found at seven coastal localities in Mendocino, northern Sonoma, and possibly northern Marin Counties in California. A site near Point Arena (Mendocino County) has not been populated by the butterfly since the 1940s. The limited number of specimens in museum collections and limited field observations make any assessment of the historic range of this butterfly difficult.

Since 1977, the lotis blue butterfly has been found only at a single 5-acre (2-hectare) site north of the town of Mendocino. Between 1977 and 1981 only 16 adult specimens were seen in 42 days of field searching at the site. This may make the lotis blue the rarest butterfly in the continental United States. Natural factors and human intrusion may have played a role in the lotis blue's scarcity.


Because of its low numbers and limited distribution, the lotis blue butterfly is extremely vulnerable to further loss of habitat, and a number of potential threats exist, such as logging, peat mining, power line corridor maintenance, herbicide and pesticide application, and alterations of water regimes.

Fire suppression may affect distribution and abundance of the host plants. Drought during 1976 and 1977 caused the sphagnum bog to dry out, and no lotis blue butterflies were observed in 1977.

Conservation and Recovery

The only known population site is on private land. The U. S. Fish and Wildlife Service has attempted to negotiate a conservation agreement with the landowner to arrange maintenance of vegetation at the site to limit the use of pesticides and herbicides. If the extant population is ever deemed large enough, several adults may be removed to other breeding locations within the historic range. Captive breeding may also be considered.


U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121


Arnold, R. A. 1983. "Ecological Studies on Six Endangered Butterflies (Lepidoptera: Lycaenidae): Island Biogeography, Patch Dynamics, and the Design of Habitat Preserves." University of California Publications in Entomology 99: 1-161.

Arnold, R. A. 1981. "A Review of EndangeredSpecies Legislation in the USA, and Preliminary Research on Six Endangered California Butterflies." Beihefte zu den Veröffentlichungen fuer Naturschutz und Landschaftspflege in Baden-Württemburg 21: 79-96.

Arnold, R. A. 1978. "Survey and Status of Six Endangered Butterflies in California." Report. California Department of Fish and Game, Sacramento.

Tilden, J. W. 1965. Butterflies of the San Francisco Bay Region. University of California Press, Berkeley.

U. S. Fish and Wildlife Service. 1985. "Recovery Plan for the Lotis Blue Butterfly." U. S. Fish and Wildlife Service, Portland, Oregon.

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