The season for insect-watching never completely ends on Martha’s Vineyard. One can always hunt for and (and sometimes find) concealed, overwinter forms. Small pockets of winter activity can persist where sun exposure and shelter combine to produce a warm microclimate. And there are even some insects — actually, a surprising number — that have evolved life histories, putting active parts of their life cycles in the winter months. But let’s face it: Once we’ve had a couple of light frosts, we’re in the “season of frustration” for a bug-watcher. That’s why I have a mild obsession with finding insects still active long past their expiration dates, hardy (or lucky) individuals that defy the odds and survive well into winter.
A fine example occurs as a common breeding species in our Oak Bluffs yard: the red-legged grasshopper, Melanoplus femurrubrum. Surely the most numerous grasshopper species on Martha’s Vineyard, and arguably the most plentiful member of the whole order Orthoptera, this insect often successfully breeds in any open habitat rich in grasses and other herbaceous vegetation. You can find them in yards and pastures, on roadsides, in gardens, amid the little bluestem clumps of our native grasslands, even in small pockets of sedge and asters found in the middle of woodland.
In favorable habitat, red-legged grasshoppers reach astonishing density; sometimes eight or 10 can be found in a square meter of habitat. I expect this abundance stems in part from the generalist nature of this grasshopper, which appears to be able to eat and successfully digest nearly any type of vegetation. But it is also clear that this is simply one tough bug. In my yard, the first tiny red-legged grasshopper nymphs emerge from their eggs, buried shallowly in the soil by their ovipositing mother, around mid-July. Perhaps two millimeters long, they already resemble adults in structure and, to some extent, coloration. Mostly greenish in overall color (though this species is notorious for producing odd-looking color morphs), with rectangular black marks on the sides of their thoraxes, scores or hundreds of these tiny grasshoppers abruptly appear in our front yard meadow. They seem to hatch all at once, or anyway within a few days of one another. Over the next few weeks, it’s fun to watch these insects mature, passing quite rapidly through five more distinct stages of development, with molts of their exoskeletons punctuating the process. The rate of development varies, it seems, and therefore so does the date at which they reach maturity.
By mid-September, my complete annual crop of red-legged grasshoppers is happily feeding, basking, and mating amid the grasses and forbs. I occasionally find a female laying the eggs of next year’s generation, the tip of her abdomen working down into the sandy soil as if she’s drilling for oil. Their numbers gradually dwindle through the fall, mostly, I expect, as individuals fall prey to birds and praying mantises. And solitary wasps, like the great golden digger wasp, Sphex ichneumoneus, provision their nests with paralyzed grasshoppers. Abundance drops even more sharply with the first strong autumnal cold fronts in October. While exposure to temperatures in the upper 30s is not necessarily lethal to this species, it undoubtedly puts a hurtin’ on any individuals that are sick, parasitized, or malnourished. As the temperature drops further, so do my grasshopper numbers.
By Thanksgiving, the population is down to a dozen or so, and I start my game of watching for the final sighting of this generation. As they senesce, these grasshoppers grow sluggish and begin to lose their coloration, darkening to a fairly uniform brown. But on clear days, sunlight warms the survivors enough so that they can move about and feed, thereby extending their lease on life. And whether through luck or good instinct, some individuals find congenial settings — in weeds against a south-facing piece of house foundation, among the grass at a south-facing angle in a fence — where conditions favor survival.
There’s no point searching for them on cold or cloudy days. But through December and into January, I keep looking when the sun is out. The species can be found reliably in our yard into mid-December, which is often when our first truly cold weather hits. Most years, a few linger to the end of the calendar year, and some years, I’ve found this species into mid-January.
Then one day, conditions are right, but I can’t find one. Biologically speaking, these holdouts are probably neither here nor there. If male, they’re unlikely to find a fertile female to mate with, and if female (and most of them are), they’ve laid what eggs they have to lay. These individuals have done their jobs, and just haven’t gotten around to dying. But there is something admirable about their hardiness and tenacity, shrugging off light freezes and a dearth of edible vegetation to persist long beyond their expected life span. The day when I can’t find one is always a little sad. But by that time, the days may already be lengthening, as the Island swings toward its next fertile summer and its next generation of Melanoplus femurrubrum.
