Edwards' Hairstreak (Satyrium edwardsii) (Grote & Robinson, 1867)

Diagnosis: A relatively small, tailed hairstreak (wingspan: 19 to 31 mm), edwardsii is dark brown above, sometimes with an orange spot above the tail. The underside is pale brown. It is best distinguished from other similar hairstreaks by the band of white-rimmed circular spots on the undersides (in some specimens, this chain is reduced or absent). Another defining characteristic is the long orange mark along the inner margin of the hindwing underside. Similar species have only a small amount of orange.

Range: This is basically a butterfly of the eastern U.S. that ranges north into four Canadian provinces.There are a few colonies in southern Quebec (Eastern Townships, near Montreal, and at Luskville near Hull). It is widespread in southern Ontario and southern Manitoba and is found at four locations in southeastern Saskatchewan.

Specimen collection data

Similar Species: The lack of an orange cap on the blue spot on the hindwing underside means that the Edwards' Hairstreak is likely to be confused only with the Banded Hairstreak and Hickory Hairstreak (S. calanus and S. caryaevorum). In both of these species the dark spots beneath are rectangular and fused to form a band rather than being broken into rounded spots, and there is only a small amount of orange on the inner margin of the hindwing beneath. [compare images]

Early Stages: The larvae are dark greenish brown with pale oblique dashes, and feed on the buds and leaves of various oaks. They feed on Black Oak (Quercus velutina) and White Oak (Q. alba) in southern Ontario, Red Oak (Q. rubra) in Quebec, and Bur Oak (Q. macrocarpa) in Manitoba. Eggs are laid in crevices and wounds in the bark. First- and second-instar larvae feed during the day, older larvae only at night, spending the day in shelters built by ants at the base of the tree, where they are tended and protected by ants; they later pupate there (Webster and Nielsen, 1984).

Abundance: This species is considered to be fairly common in southern Ontario and Manitoba, but becomes quite local and rare at the extremes of its range, such as in the Ottawa area and in southern Quebec.

Flight Season: The adults fly from late June into August in Canada.

Habits: Adults are usually found near oak, the larval foodplant. They are attracted to a variety of flowers, especially milkweed and White Sweet Clover. Edwards' Hairstreak may have been overlooked in some areas because of its similarity to the more common Banded Hairstreak.

© 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.