As calendar years approach their ends, I always find myself reflecting back on what interesting species I found in the preceding months. But I also give some thought to ones that I didn’t see: species that are unexpectedly scarce, or missing altogether, on Martha’s Vineyard always raise the question of whether they’re actually absent or simply overlooked.
Some of the best examples of mysteriously missing species are found among the butterflies. The viceroy, for example, has a respectably long history on the Vineyard. And it’s not a species I’d expect to overlook: a famous mimic of the monarch butterfly, the viceroy is a good-size, bright orange insect, and it’s very much on my personal list of species to be alert for.
The history of this butterfly on the Vineyard dates back at least to 1917, and while it has apparently never been common here, the viceroy turned up with some regularity up to the middle of the 20th century. And off the Vineyard, it remains fairly common, with statewide distribution, including recent records on Cape Cod and even the Elizabeth Islands.
But on the Vineyard? You’d think it’d be easy to find, since the wetland edge habitats it prefers are not rare, and the host plants its larvae use — willows and aspens — are far from scarce. Yet I’ve seen viceroys exactly three times on the Island, most recently in 2004. The current scarcity of this butterfly makes me suspect that it now occurs here only as a vagrant from the mainland.
Yet that 2004 record, of a very fresh individual at Katama, does not suggest an individual that had made an arduous over-water journey before roosting gratefully on the first available dry land. I have this nagging feeling that viceroys persist here, breeding along some cove head or pond edge, and I’m just too stupid to find them.
More clear-cut is the case of the silver-bordered fritillary, a butterfly of damp woodland edges, ranging quite widely in search of nectar. It depends on violets for reproduction, and is said to be especially fond of lance-leaved violet, which is widespread and locally abundant here. Silver-bordered frits were “regularly present in suitable area,” according to a 1943 publication. And at present, they are fairly common virtually across Massachusetts, with recent records even as close as Falmouth.
So why can’t I find one? This is a butterfly I’ve never seen on Martha’s Vineyard, and as far as I can tell, the most recent Island records are well over a half-century old. At least in this case, the Vineyard is not alone. This fritillary, once common on Nantucket, appears to be extirpated there as well, and its numbers appear to be declining on Cape Cod. But I’ve yet to see a convincing explanation for this decline, and that makes me wonder if they’re truly as gone as they appear to be.
Then there is the case of the black dash, a wetland skipper. This small butterfly seems to be truly common nowhere in our region, though it has many populations in eastern Massachusetts, as close to the Vineyard as Plymouth County. Skippers are strong fliers, and some species have a reputation for vagrancy — but the black dash is not among them. So two 1942 records from a bog in West Tisbury strongly suggest a Vineyard breeding population, if perhaps small and localized.
Are black dashes still out there, in some up-Island swale or bog? You can’t prove it by me: I’ve looked for 25 years now, and come up empty. But wetlands can be hard to survey, often ringed in by dense shrubbery generously laced with poison ivy. And many of the most promising ones are hard to get permission to explore. But insects can often persist for surprisingly long times in small, isolated populations. So I keep hoping that one of these years, either I or another observer will happen to check the right bog on the right day and rediscover this species on the Vineyard.
Finally, there’s the dreamy duskywing. Sparsely but widely distributed across most of Massachusetts, this dark brown skipper shows a cluster of records in Plymouth County, mostly at Myles Standish State Forest. In 1943 it was considered “not rare” here, and three Vineyard specimens reportedly still exist in Yale Peabody Museum. They’re associated with aspens and poplars, and you’d think this species would be at least locally common here. Yet I find one only every few years, with my most recent sighting in 2016.
A more northerly butterfly than many, the dreamy duskywing may be retreating to higher latitudes and elevations in response to climate change. There seem to be few recent coastal records to our south. So this missing butterfly, at least, may be going unrecorded here due to a genuine regional decline, rather than my obtuseness as an observer.
A lifelong Red Sox fan, I find it natural to say “Wait till next year!” I’ll try again in 2023 to find all of these insects. If you find any of them yourself, please let me know.