Hickory Hairstreak (Satyrium caryaevorum) (McDunnough, 1942)
Diagnosis: Similar in size to the other look-alike hairstreaks (wingspan: 22 to 28 mm), this butterfly can be difficult to identify. It has a greyish-brown underside with a darker coloured band outlined in white on both sides. The segments of the band are strongly offset and wider near the top. The blue spot is correspondingly longer compared to the neighbouring orange spot than in the other species.
Range: The main part of this butterfly's distribution is in two discontinuous areas in the northeastern U.S. It occurs in Canada only in southern Ontario and southern Quebec near the Ontario border.
Similar Species: The much more common Banded Hairstreak (S. calanus) is highly variable andsome forms are frequently confused with the Hickory Hairstreak. In the Banded Hairstreak the white-edged dark band on the hindwing underside is a series of dark rectangular spots margined mainly on the outside in white; the top-most spot in this band is similar in size and shape to the others, but is offset towards the base of the wings, much narrower than the partial second band near the middle of the wing; and the orange and black spot between the two tails (adjacent to the blue spot) is a reddish crescent above a black triangular spot and is as large as the black spot. In the Hickory Hairstreak the series of spots forming the dark band is progressively wider towards the top, so that the offset top spot is as wide as the partial second band and the black spot between the two tails has an orange line capping it that is much smaller than the spot. The two species differ significantly in genitalic structure. [compare images]
Early Stages: The larvae are yellow green (turning brown shortly before pupation), with two whitelines down the back and oblique yellowish marks on the sides. In Canada, they have been reared on Bitternut Hickory (Carya cordiformis), Butternut (Juglans cinerea), Red Oak (Quercus rubra), WhiteAsh (Fraxinus americana), and hawthorn (Crataegus sp.).
Abundance: This is usually considered a rare species throughout its range. However, in some years, it can be abundant and shows up in areas where it is not normally seen.
Flight Season: Adults fly from late June to early August in its limited Canadian range.
Habits: Usually associated with deciduous woodlands, it is easiest to find on milkweeds and White Sweet Clover alongside the woods.
Remarks: The year 1992 was a remarkable one for this species. In most of its Canadian range it was extremely abundant, far outnumbering all other hairstreaks combined. On one flowering Basswood tree near Tweed, Ontario, it was estimated that thousands of individuals were nectaring. When the tree was shaken, a cloud of Hickory Hairstreaks flew off. One swing of a net caught 29 individuals (Jack Holliday, News of the Lepidopterists' Society, March/April 1993).
© 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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