Welcoming the red-banded hairstreak butterfly

As our climate warms, we record new species moving in.

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The red-banded hairstreak butterfly was documented, reportedly the first sighting on Martha's Vineyard, at Morning Glory Farm. — Matt Pelikan

Colorful, relatively easy to find and identify, butterflies have long been a favorite of collectors and field observers alike. Butterfly diversity is low enough (about 70 species have been documented on the Island) so that one can easily get a grip on it. Vineyard butterfly records exist dating back to the early years of the 20th century; an entire monograph on the moths and butterflies of the Massachusetts islands appeared in 1943.

The versatile Chilmark naturalist Allan Keith compiled existing information, plus decades of his own observations, into a checklist in the mid-1990s. Since my arrival here in 1997, I’ve built on Allan’s ongoing work with my own field observations and reports from dozens of other observers.

As a result, we have a fairly accurate picture of what butterflies occur here, and how that list has changed over the past century or so. A number of species, including some that were once quite common here, have gone unreported for decades despite ardent searching, and can be presumed gone. More cheerfully, new species have arrived, either as first-time vagrants or as colonizers establishing a lasting presence on the Island.

Regular Wild Side readers may recall columns I wrote describing an invasion of the Island, beginning in 2011, by a small, orange butterfly called the Sachem. (For example, “Flora on Martha’s Vineyard will adapt as climate changes,” on August 1, 2012.) Essentially a southern butterfly, and one prone to late-summer vagrancy, the Sachem as a breeding species is well suited to creep northward with a warming climate.

The first Island records, which were also the first for Massachusetts, came in 1995; a single male turned up at Quansoo in 2005; and then, in 2011, a major influx resulted in colonization of much of the Island.

For a few years, Sachems were common here: I recorded as many as 16 at once in my small yard alone. But that horrible winter of 2014–15 was not kind to the species: In 2015, I only found a single individual, making it clear that conditions for this warmth-loving insect to overwinter are still marginal here.

Sachems will surely become permanent residents soon, and are just the first of a number of butterflies we can expect to arrive here amid a warmer climate and milder (if sometimes more chaotic) winters. Another piece in this pattern, the red-banded hairstreak, has turned up, apparently for the first time ever on the Vineyard, at Morning Glory Farm, Edgartown, on Sept. 3.

Even more intriguingly, a second individual was photographed on a conservation property in West Tisbury a few days later. The habitat at this second location was classic breeding habitat for this butterfly, raising the possibility that a small colony may already exist, or, if not, that arrivals this year may initiate that process.

Rather dull except for its eponymous band, this butterfly is a tiny one, about the size of a penny when it perches with wings folded over its back. The underside of the wings, which are about all you ever see, are brownish or greenish gray, but a bold red stripe, edged on the rear in white, crosses the wings. In size, behavior, and overall coloration, a red-banded hairstreak superficially resembles a half-dozen other, more common relatives. But that red band is unique, and usually highly visible.

The red-banded hairstreak is a butterfly of shrubby, open areas — brushy fields, powerline cuts, woodland edges, and the like. The species has a strong but somewhat mysterious connection with winged sumac, a native shrub that is common here sometimes to the point of invasiveness. The butterfly’s caterpillars are generally thought to feed on decaying leaf litter on the ground. Some accounts suggest that the species lays its eggs preferentially on winged sumac, or that fallen sumac leaves are the detritus the caterpillars prefer to eat. In any case, the prevalence of this plant on the Vineyard indicates plenty of habitat for this butterfly.

Like all hairstreaks, the red-banded hairstreak is active and an absolute nectar hound, visiting all the classic nectar sources, both domesticated (like butterfly bush) and wild (like milkweeds, asters, and goldenrods). Rich in sugar and other nutrients, flower nectar fuels the hairstreak’s active lifestyle; by far the easiest way to find this or any other hairstreak is to search patches of good nectar-producing flowers.

In mainland Massachusetts, this hairstreak has been found with increasing regularity over the past decade or so, with most Bay State records (like the two recent Vineyard sightings) in the late summer or fall. Farther south, where the species is established, red-banded hairstreaks pass through two generations a year, with the first one active as adults in May and June. The red-banded hairstreak will probably have two flight periods here as well, since its establishment is surely just a matter of time.