Reakirt's Blue
Hemiargus isola (Reakirt, 1866)

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Diagnosis: The upperside is violet blue, heavily suffused with brown in the female, with two or three black spots near the anal angle in both sexes. The underside is light grey with a row of large black, whiterimmed spots on the forewing and three or four black spots near the anal angle, each with a tiny iridescent centre. Wingspan: 16 to 23 mm.

Subspecies: The nominate subspecies is Mexican; the North American subspecies is alce.

Range: Resident only in Central America and the extreme southern U.S., isola migrates regularly throughout most of the U.S. almost to the Canadian border, and very rarely into the southern Prairies.

Similar Species: The Marine Blue (Leptotes marina). [compare images]

Early Stages: Eggs are laid singly on flower buds. Larvae eat flowers, fruits, and young leaves, and are often attended by ants. They eat a wide variety of herbaceous and shrubby Fabaceae, particularly mesquites (Prosopis spp.).

Abundance: Common in the south, this species becomes less common farther north.

Flight Season: Adults fly all year in the extreme south, with many generations, but they fly from June to October farther north.

Habits: Hemiargus isola is normally found in flowery fields, meadows, and roadsides.

Remarks: Despite its weak flight, it regularly migrates long distances and has been recorded several times in Canada. A male was taken by Ronald Hooper on Yellow Clover near Tantallon, Saskatchewan, on 6 July 1966. Klassen et al. (1989) state that two specimens taken in Manitoba in 1932 and 1933 are in the American Museum of Natural History, but no exact locations are recorded. The male from Manitoba illustrated in the plate was collected by David Parshall on 15 July 1973; it was also illustrated in Butterflies and Skippers of Ohio (Istner et al., 1992).

© 2002. This material is reproduced with permission from The Butterflies of Canada by Ross A. Layberry, Peter W. Hall, and J. Donald Lafontaine. University of Toronto Press; 1998. Specimen photos courtesy of John T. Fowler.

The Toronto Entomologists' Association thanks Agriculture and Agri-Food Canada for providing the content and computer code for this web page.