Hessel’s hairstreak – only recognized as distinct from the similar juniper hairstreak in 1950 – is poorly known from Delmarva. It is believed to be restricted to stands of Atlantic white-cedar, Chamaecyparis thyoides, which itself has a very narrow habitat requirement (coastal plain swamps in the Delmarva region), a tree practically decimated in the mid-Atlantic by logging, development, and swamp drainage. Even in its preferred habitat the hairstreak is seldom encountered; the little that is known about its ecology suggests that it descends in early morning and late afternoon to nectar (Vacciniums and Amelanchier in the spring brood, Clethra in the summer) and take minerals from damp sand and soil, spending the bulk of the day high in the canopy of the white-cedars (mature trees are quite tall, 20m-30m).
Dick Smith notes that Hessel’s hairstreak apparently has not been collected in Maryland since the species was described in 1950, and is assigned to the Maryland fauna only on the basis of a reference to a (now unknown) specimen collected in the early part of the 20th century and discovered in a collection after hesseli was described. But there are a few places where it is possible that Hessel’s hangs on, and the success of a number of reforestation efforts in the Salisbury area on the Eastern Shore and the Severn drainage on the Western Shore give hope that it can be confidently returned to the Maryland butterfly list. So a number of us are planning to make 2012 the Year of the Hessel’s Hairstreak.
To this end, we’ve been poring over photographs and specimen records up and down the East Coast – principally in the Carolinas, the NJ Pine Barrens, and various locations in New England – to figure out the likely habits and flight periods for Maryland hesseli. From what we’ve been able to deduce, it’s probably a fairly early species on the Eastern Shore – early April into May would be a pretty good guess, roughly the same as juniper hairstreak and some of the elfins in the same geographic area. The spring flight almost certainly is timed to peak bloom of various blueberries. The second brood is about two months later, late June into July, and likely coincides with peak bloom of Clethra and possibly buttonbush. In New Jersey, the summer flight is most often seen at field and roadside flowers near Atlantic white-cedar stands.
With the grateful assistance of colleagues at the Maryland Department of Natural Resources, The Nature Conservancy, and various other organizations, we’ve identified about a half-dozen “most likely” candidate locations to check out for Hessel’s hairstreak in 2012. Our principal push will be the last two weeks of April and the first two weeks of May.
This is somewhat more hopeful than hunting a needle in a haystack, but our search may not be successful. The white-cedar stands may be too junior, too scattered, or too embedded in other forest canopy to support the habitat that Hessel’s favors. Gypsy moth and mosquito spraying could have taken their tolls. But we’re nothing if not optimists.
We’ll post notices on LepLog a few days before each field trip (weather depending, of course) and encourage the participation of anyone who’s interested in joining us. Please email us at firstname.lastname@example.org with the subject line “Hessel’s hairstreak.”