The Hunt for Hessel's Hairstreak

A Wilbraham Butterfly Mystery

The Conservation Commission will hold a "Hunt for Hessel's" on May 22 at 2:00 p.m., beginning at the north trailhead of the McDonald Nature Preserve. The state documented this rare butterfly species in the White Cedar Swamp in 1960, but it hasn't been spotted here since then.

The butterfly enthusiast world was all aflutter in 1982 when Roger Pease discovered several Hessel's Hairstreaks in Wilbraham's largest swamp. His account of how he found them can be read in the Massachusetts Butterfly Club's journal Massachusetts Butterflies.

According to Pease, he took the specimens to the Yale Peabody Museum in New Haven, CT, but a search of the museum's online catalog fails to reveal any butterflies from Wilbraham: the only ones from Massachusetts were taken from Dover.

So I presume there is no official confirmation of Pease's find. Wouldn't it be something if one were found in this year's Hunt for Hessel's?

The first recorded capture of the Hessel's was in Milton, MA, in 1941, but this female wasn't attributed to the species until 1950, when the Hessel's Hairstreak was officially named after Sidney Hessel, who discovered subtle distinctions between the Hessel's and its sibling species Juniper Hairstreak.

The Hessel's is intimately associated with the Atlantic White Cedar tree, this butterfly's only larval food plant. But this tree is threatened by land clearing for development, according to the Massachusetts Division of Fisheries and Wildlife. Increased housing means not only felled White Cedars, but also more storm and fertilizer runoff and siltation, which contributes to nutrient enrichment in the soil. This is good for hardwoods, but deadly to the remaining White Cedars.