Species Satyrium acadicum - Acadian Hairstreak - Hodges#4278

4278

Western populations are often segregated as subspecies montanensis, but this distinction has been debated. There is no obvious place to divide western from eastern populations (the distribution is broad and continuous), so it is difficult to decide at what point to stop calling them by one name and begin the other. Also, differences are difficult to quantify, and quoted distinctions do not seem to hold up to scrutiny (western specimens do not seem to be reliably separable from eastern based on any combination of characters). Western specimens do average paler in color, while northern (occasionally distinguished as subspecies watrini) seem to average smaller and darker, but not consistently so. Variation seems to be minor and perhaps clinal across the entire distribution of the species, or perhaps might be more related to environmental influence than genetic differences.

Medium sized hairstreak, with wingspan of about 30-32mm.

Gray underwings with small black spots circled in white. Several orange to red submarginal spots on hind wing and usually also on front wing, and a blue patch (= the so-called "thecla spot") near the tails and hind (anal) angle of the hind wing. The blue spot is capped with orange/red.

At western edge of range, may be confused with S. sylvanum and S. californicum. Both species are typically more brownish both above and below than S. acadicum, and both (especially S. sylvanum are more likely to have fulvous areas on the upper wings (S. acadicum is gray above with orange or fulvous patches usually faint, small and limited to the margin of the hind wing at most). These two species are only known to occur with or near S. acadicum at the east base of the Rocky Mountains where the Plains meet the mountains.

On the under side, S. sylvanum may be brownish gray to nearly white, but only rarely is it nearly the same gray as S. acadicum; the black spots tend to be less bold, and the orange near the outer margins is lacking from the front wings and reduced (often only present in one or two cells) on the hind wing. There is no orange capping the blue "thecla spot". The tails on S. sylvanum are sometimes reduced. S. sylvanum is associated with Willows in the Rockies and westward.

Like S. californicum is a western butterfly, primarily limited to mountain regions, and found west of the Great Plains. It is a more brownish butterfly both above and below, but otherwise quite similar. The orange or red coloring on the underside is usually less extensive, and black spots are usually somewhat less boldly pale-ringed and less contrasting. S. californicum is associated mostly with shrubby Rosaceae or Ceanothus, and not with Willows. [Though, it has been reported as associated with Willows in the Okanagan Basin in Washington and British Columbia.}

East from the Great Plains S. edwardsii is similar, but tends to be more brownish both above and below. It has most of the dark spots below lighter in color (not entirely black), larger, and generally somewhat more rectangular in shape. They tend to not be completely ringed with white, but rather only on two or three sides. The blue "thecla spot" on the hind wings is not prominently capped with orange/red. It is associated with Oaks (mostly Scrub Oaks).

Satyrium titus shares much of the same distribution, and can look similar, but it has no tails, tends to be more brownish, has the blue "thecla spot" missing (or very narrow and barely indicated) on the hind wing. The submarginal row of orange/red spots extend along the entire outer margin of the hind wing (and sometimes show through on the upper side too), and includes the enlarge orange cap of the bluish "thecla spot" (or where the blue spot would be if it were present). On the ventral front wing, the dark bar at the end of the discal cell is absent or very weak in S. titus. It is associated with Prunus species.

Northern half of the US and southernmost Canada, from the east coast to the east base of the Rockies.

Damp areas with Willows.

1 brood, flies early summer, June to early July.

Larval hosts include a variety of Willows (Salix species). Adults are avid visitors of a variety of flowers, with Milkweeds (Asclepias species) and Dogbanes (Apocynum species) particularly favored.

Generally considered to be uncommon, but can be quite abundant in some regions and in some years, always in close association with Willows. Adults rarely wonder far from their larval host Willows.

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