Wild Side: East Coast grasshoppers

H. v. brevipennis is a beautiful specimen, as far as grasshoppers go.

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As interesting as I find grasshoppers to be, I have to admit that as a group, these are not particularly colorful insects. In keeping with the benefits of staying hidden while perched on stems or the ground, most of our grasshoppers are drab creatures, often gray or brown and lacking strong patterns. A grasshopper’s fondest dream is to live its life unseen by anything larger than itself.

There are, however, exceptions, and the most garish of our grasshoppers ranks in my view as one of the Vineyard’s prettiest insects. It’s also one of our most puzzling.

Hesperotettix viridis is a species with a vast geographical range, spanning North America. Our regional subspecies, H. v. brevipennis, has no standardized common name and is found only on the East Coast, roughly from Massachusetts south to Georgia. It’s one of four subspecies recognized for H. viridis, and therein lie a lot of complications.

Here, at least, H. viridis presents no identification challenges. A striking insect about an inch long, our population is bright green with a purple stripe down the top of its thorax. Edges of its short wings and legs have purplish highlights, and there is a black-and-white patch on the side of the thorax. None of our other grasshoppers looks anything like this.

But Hesperotettix viridis as a whole is giving biologists conniptions. Indeed, the entire genus Hesperotettix, which is currently thought to have five species in addition to H. viridis, is a muddle. Forms that appear subtly distinct from each other overlap in distribution, and nobody knows how those forms are related. Do they interbreed a lot, a little, or not at all? If the answer is a little or not at all, what factors — food preference? seasonality? anatomy of the reproductive structures? — account for the separation?

Some subspecies of H. viridis (as biologists currently think of the species) look as much like other species in the genus as they do other forms within H. viridis. And our Eastern subspecies appears largely isolated (by the Appalachian Mountains) from the rest of Hesperotettix viridis. The whole genus is a mess, taxonomically speaking, and the situation illustrates the sort of basic knowledge about wildlife that biologists often lack.

As a curator of the website Bugguide.net laconically notes, “it seems likely that with further study, there may yet be some future reshuffling of names” within Hesperotettix. Some of the forms currently assigned to one species may be moved to another one. And some groups currently viewed as subspecies may prove, once we’ve learned more, to merit full species status. Our local race, H. viridis brevipennis, with its geographical isolation from the rest of this untidy taxonomic complex, appears to be one candidate for elevation to full species.

Although H. viridis brevipennis occurs along most of the East Coast, it seems to be uncommon and local wherever it occurs. Martha’s Vineyard and Massachusetts generally are no exceptions. On the Vineyard, I’ve only found this grasshopper in three widely separated locations: in West Tisbury along the Mill Brook, on a grassland remnant near Oyster Pond, and along a particular fire lane in the Eastern portion of Correllus State Forest.

At a couple of these locations, anyway, the species has been present for a decade or more. But its occurrence is limited to specific areas only an acre or two in size, with many more acres of seemingly identical, immediately adjacent habitat unoccupied. Why? I haven’t the faintest idea.

In mainland Massachusetts, as far as I can tell, there is only one known population, at Myles Standish State Forest in Plymouth. Significantly, Myles Standish and the Vineyard’s Hesperotettix sites are ecologically similar: Dominated by “sandplain” soils, all these locations support plants like little bluestem grass and scrub oak that flourish in lean, droughty settings. Never a common habitat, such sandplain grassland is quite rare now, with much of it having been lost to human development. From a conservation perspective, then, good sandplain sites are important, and Hesperotettix is an example of exactly the kind of dry grassland specialist that is at risk as the extent and quality of our sandplains dwindle.

All of this is complicated, and if you’ve managed to stick with me to this point in today’s column, thank you for your patience and persistence! The point is that this colorful grasshopper perfectly illustrates why Martha’s Vineyard matters so much to conservationists.

Requiring a rare and diminishing habitat type, geographically isolated from its closest relatives, and uncommon at best in its limited geographical range, H. viridis brevipennis (or whatever it really should be called!) is at risk of going extinct before we even know exactly what it is. The Vineyard hosts an elusive but apparently solid population of this grasshopper, with most of that population occurring on protected conservation land. Islanders have inherited, this is to say, responsibility for a significant piece of grasshopper biodiversity.