Acadian Hairstreak (Satyrium acadicum) (W.H. Edwards, 1862)
Diagnosis: This is a larger-than-average (wingspan: 24 to 32 mm) hairstreak. In the east it is the only hairstreak with a grey underside and a row of round black spots. It also has a row of submarginal orange spots and an orange cap over the blue spot on the hindwing. It has one long tail.
Subspecies: Specimens from the northern part of its range (watrini) tend to be slightly darker than normal acadicum, but the differences are too subtle and variable for subspecific recognition. Pale specimens from Waterton Lakes National Park in southwestern Alberta are subspecies montanensis.
Range: Satyrium acadicum is found from Nova Scotia and Prince Edward Island across southern Quebec and eastern Ontario as far north as Cobalt. From northwestern Ontario, it ranges across the southern Prairie Provinces to southwestern Alberta.
Similar Species: In the west it is most similar to the California Hairstreak (S. californicum) and the Sylvan Hairstreak (S. sylvinum), but its range does not overlap the ranges of these species in Canada. Faded specimens of Edwards' Hairstreak (S. edwardsii) in eastern Canada and Manitoba resemble the Acadian Hairstreak, but lack the grey ground colour and do not have an orange cap over the blue spot on the hindwing underside. [compare images]
Early Stages: The larva is green, with two white longitudinal lines and narrow, oblique, white to yellow dashes on the sides. It feeds on willow (Salix spp.).
Abundance: This is a widespread butterfly, but not usually found in great numbers. It does not appear to have as dramatic population fluctuations from year to year as do some of the other hairstreaks.
Flight Season: In Canada this hairstreak flies from late June to mid-August; it is most often seen in July.
Habits: The Acadian Hairstreak is almost always associated with willows. It is a butterfly of wet meadows, fields, and stream banks and is often found in roadside ditches perching on high grasses or sedges.
Remarks: The surest way to find the Acadian Hairstreak is to search milkweed plants in damp areas near willows. When occupied in nectaring on the flowers, it can be approached very closely. Because of its fondness for flowers, it is frequently caught by crab spiders hiding in flower heads.
© 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.
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