Wild Side : Crickets and katydids make a racket on Martha's Vineyard now
Photo by Matt Pelikan
Regular readers know that my current obsession is Orthoptera, the insect class that comprises grasshoppers, crickets, and katydids. Dramatically under-studied on the Vineyard, insects in this group are diverse, widespread, and common on the Island.
I've made some progress learning about them, having gotten acquainted with more than 30 species. But the thing I like most about these insects is what they contribute to the sonic landscape. Since I began listening in on the private songs and calls of these insects, I've realized just how ubiquitous they are on the Island. Just as songbirds do, Orthoptera add immense richness to my world, broadcasting messages that I'm gradually learning to decode.
Grasshoppers, perhaps the most familiar branch of Orthoptera, are actually not involved in the chorus. Though some grasshoppers do make noise, in most cases it is nothing more than the rattle of their wings as they fly. None of the grasshoppers that "stridulate" — call by scraping body parts together — have yet been recorded on the Island, so the insect noises we're hearing come almost entirely from crickets and katydids. Late summer presents the peak of diversity and activity for these insects.
Virtually anywhere on the Vineyard at this season, on warm nights and even during the day, you can hear at least one of these insects calling. If you listen carefully, you can usually sort out multiple species, sometimes a half-dozen more at once, since each series of buzzes, whirrs, chirps, or clicks is likely the signature of a different species. Many of our Orthoptera are true generalists as far has habitat goes; for a surprising number of species, for example, residential neighborhoods appear to work just fine.
Everybody is familiar with the "crick, crick, crick" call of what most people simply call a "cricket." Fully mature ones, nearly black in color, are fat creatures about an inch long. Females (as with many Orthoptera) sport a spike-like ovipositor (an organ for laying eggs) on the stern, which looks menacing but is harmless. Our six-month season for cricket calls conceals our diversity: the crickets that call in the spring and in the fall turn out to be different species (it is the fall field cricket that is calling now), and third species, the sand field cricket, has a very similar call and seems to be reasonably common on the Vineyard.
Then there are the ground crickets, of which the Island boasts at least three species. Pint-sized relatives of the field crickets, ground crickets are generally about half an inch long, and their calls resemble the calls of field crickets, only dramatically speeded up. The effect is kind of like the noise made by a squeaky pulley.
Even that, though, doesn't exhaust the cricket family. The Vineyard turns out to be well endowed with tree crickets, delicate, pale green creatures that bear little obvious resemblance to other crickets. Slender-bodied, females look almost worm-like, while males feature delicate, lacy wings. Depending on the species, tree crickets may call continuously or in punctuated bursts; generally, their calls have a soft quality, quite unlike the harsher buzzes or ticks that most katydids produce. As exotic as these insects seem, a couple of our tree crickets are common even in heavily developed areas of the Vineyard.
Even after two seasons of studying Orthoptera, I can't put a name to many of the calls I hear. But these are distinctive noises: the insects themselves use their calls to sort themselves out, making sure that females find a male to mate with of their own species. With sufficient stealth, patience, and a flashlight if it's night, you may be able to zero in on the sound of a calling Orthopteran in order to watch it sing. (I find that cupping my hands behind my years make a sort of directional antenna for insect calls, helping me locate the source of the sound.) These insects sing by rubbing their wing edges in a flurry; special teeth set up vibrations which the stiff wings themselves amplify.
The reason for this late-summer crescendo of song and activity is simple: it's mating season in the Orthoptera world. After maturing during the course of the summer, females seek a male to mate with and then lay fertilized eggs, depending on species, either in the soil or in the tissues of plants. Lying dormant over the winter, the eggs hatch in spring, yielding nymphs that are essentially tiny versions of adults. And the cycle repeats.
Adult Orthoptera generally can't tolerate freezing temperatures, and the progression of autumn will eventually bring an end to the stridulation chorus. But there are many weeks left to the season; in a typically year, many species sing well into October, and a few hardy ground crickets in our yard made it through the first week of December last year. So there is plenty of time to tune in on the stridulation chorus.