Miami Blue Butterfly

Hemiargus [Cyclargus] thomasi bethunebakeri


Miami Blue Butterfly

Photo by: Jaret C. Daniels, Ph.D.

The Miami blue (Hemiargus thomasi bethunebakeri) is a small, brightly colored butterfly endemic to Florida; additional subspecies occur in the Bahamas and Hispaniola. Ever-expanding urbanization and the associated loss of coastal habitat have all but eliminated the Miami Blue from the south Florida mainland. In recent years, this alarming trend of decline has continued in the Florida Keys. Once abundant and widespread, the butterfly has become considerably more rare and now only occurs in a single small, isolated colony site within the boundaries of Bahia Honda State Park on Bahia Honda Key in the Lower Florida Keys.


The Miami Blue (Hemiargus [Cyclargus] thomasi bethunebakeri) is a small, sexually dimorphic butterfly in the family Lycaenidae. Males are bright metallic blue dorsally. Females are primarily dark gray with blue scaling toward the wing bases and orange-capped black submarginal eyespots on each hindwing. Both sexes are gray below with a distinct wide white postmedian hindwing band and four black basal spots. Mature larvae are highly variable and range in color from light green to maroon. Pupae are black or green. The larvae are tended by ants in the genus Camponotus. The relationship is facultative.

Life History

The species is multi-brooded with a short winter diapause period. Within the Bahia Honda colony, females deposit the small pale green eggs on the new, terminal growth of nickerbean and feed exposed on the host. For historic populations utilizing balloon vine, females would deposit the eggs on the developing fruit. Upon hatching, the larvae would burrow into the balloon and feed inside until maturity.

Primarily a coastal species, the Miami blue inhabits tropical coastal hammocks, scrub and pine rocklands where it utilizes balloon vine (Cardiospermum corrindum, also possibly C. halicacabum) and yellow nickerbean (Caesalpinia bonduc) as the primary larval hosts.


Historically, little detailed and definitive information is available on the extent of the species' range within the state. However, most experts agree that it once commonly occurred from the southern mainland (approximately Hillsborough to Monroe counties) south to Key West. Over the last few decades, the species' overall distribution and numerical abundance has been significantly reduced. The butterfly now only occurs in a single small, isolated colony site within the boundaries of Bahia Honda State Park on Bahia Honda Key in the Lower Florida Keys.

Conservation Status

In November 2002, the Florida Fish and Wildlife Conservation (FWC) received a petition for emergency listing of the Miami blue as an endangered species. Owing to Miami blue's recent decline and extremely tenuous current situation, by executive order the FWC listed the species as endangered on an emergency basis. The emergency action was subsequently confirmed at a meeting of its Commissioners in January 2003.


Continued status surveys to identify and conserve additional remaining colonies will be essential to the species' survival.

Staff at the University of Florida's McGuire Center for Lepidoptera Research are conducting ongoing population monitoring and ecological research on this species. Additional studies pertaining to the life history and genetics of remaining populations are needed.

Captive Rearing

On December 20, 2002, the Florida Fish and Wildlife Conservation Commission issued a permit (amendment no. WX02525) authorizing the collection of up to 100 eggs for the purposes of initiating a captive colony of Miami blues at the University of Florida. The McGuire Center for Lepidoptera Research at the University of Florida is currently managing a captive propagation program.

Recovery Plan

Management Plan for the Miami Blue (257KB pdf).

For more information

  • McGuire Center for Lepidoptera Research, University of Florida: Jaret C. Daniels, Ph.D., Assistant Director for Research, Phone (352) 392-5894,
  • Florida Fish & Wildlife Conservation Commission: Ricardo Zambrano, Wildlife Biologist, Phone (561) 625-5122

References and Resources

  • Kimball, C.P. 1965. The Lepidoptera of Florida. An Annotated Checklist. Arthropods of Florida and neighboring land areas. Volume 1. Gainesville: Division of Plant Industry, Florida Department of Agriculture.
  • Lenczewski, B. 1980. Butterflies of Everglades National Park. National Park Service, South Florida Research Center, Homestead, Florida. Report T-588.
  • Minno, M.C. and T.C. Emmel.1993. Butterflies of the Florida Keys. Scientific Publishers, Gainesville.
  • Smith, D.S., L.D. Miller and J.Y. Miller. 1994. The Butterflies of the West Indies and South Florida. Oxford University Press, New York.
  • Miami Blue Final Biological Status Report (131KB pdf) Florida Fish and Wildlife Commission

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USFWS Candidate Species (Federal Register: 70(90): 24869-24934, 2005)

State Status

Florida Endangered Species.



Critical Habitat

None designated


This profile was prepared by the Xerces Society for the Butterfly Conservation Initiative.