Adult: dark brown above, sometimes with an orange spot above the tail. The underside is pale brown. It is best distinguished from most similar hairstreaks by the row of white-rimmed rounded 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 mostly have only a small amount of orange.
[modified from Butterflies of Canada]
The lack of an orange cap on the blue spot on the hindwing underside means that the Edwards' Hairstreak is mostly likely to be confused with the Banded and Hickory Hairstreaks (S. calanus and S. caryaevorum). In both of these species the dark spots beneath are more sharply rectangular and mostly 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.
King Hairstreak (Satyrium kingi) is similar, but with a red cap on the large blue spot. It has a pattern more similar to that of Banded and Hickory Hairstreaks, and it mostly occurs further south than Edwards Hairstreak.
The Acadian Hairstreak (Sayrium acadicum) has smaller more nearly circular black spots mostly completely ringed in white, and is less brownish in overall coloring (distinctly gray). It has a red cap on the large blue "thecla spot" on the lower hind wing, and is associated with Willows (Salix species).
Larva: dark greenish-brown with pale oblique dashes
Northeastern and north-central North America
Dry woods, thickets, with oaks.
Adults fly from May to July in the south (one brood); late June into August in Canada.
Larvae feed on leaves of oak: especially Scrub Oak (Quercus ilicifolia) and Black Oak (Q. velutina); also White Oak (Q. alba) in southern Ontario, Red Oak (Q. rubra) in Quebec, and Bur Oak (Q. macrocarpa) in Manitoba.
Adults take nectar from a variety of flowers, especially milkweed (Asclepias spp.) and White Sweet Clover (Melilotus alba).
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.
[Butterflies of Canada]
plus description, distribution, similar species, biology, habitat, food plants, flight season (Butterflies of Canada, CBIF)