Greenwich Marsh, Cumberland County, NJ (Photo by Author)
The South Jersey marsh grass grows thick alongside the narrow, sandy road leading down to the Delaware Bay. It is mid-September. A man in a blue polo shirt pulls over, engine idling, to check his map and get his bearings. He rolls down the car window. The air is warm and soupy, filled with the ripe, fetid scent of decomposing fish.
Though far removed from the ocean, these brackish and freshwater marshes are influenced in a positive way by the daily ebb and flow of the tides. Like a beating heart, they nourish and maintain all life in the marsh, helping to restore nutrients and oxygen to this delicate ecosystem.
Two summers ago, things were not so different. A single, tall blade of switchgrass glistens in the sun, bending under the weight of something foreign coating its surface. A gelatinous mass of tiny eggs, about 500 in number, clings to the long, slender blade, biding its time until the unseen hand of nature triggers the next step. Suddenly, one egg hatches. A small larva emerges and falls to the moist soil below. Then another, and another. Like corn in a popper, the hatching continues and builds, until most of the small creatures are released. The muted cries of the newly born go unheard by the mother, who has long since departed after laying her batch of eggs many days before. She did her job, now her offspring must fend for themselves.
The first of the newborn larvae burrows into the soft, moist soil, rich in detritus and decaying matter. It is soon joined by its blind siblings, each one groping and burrowing for survival, in search of its first meal. Surprisingly, the abundance of decayed matter does not pique its appetite. Rather, its desire is for the living. It hungers for fresh meat!
Our first newborn sets out in search of what it needs. Foraging through the surface muck and wet vegetation it finally comes upon a small earthworm. It attacks! Viciously tearing into the worm’s flesh, it tenaciously clings to its prey as the worm seeks to disengage and wiggle free. At last, with its hunger satisfied, it lets go of the dying worm.
The newborn continues to feed and grow over the months that follow. Snails, worms, insect larvae, and other small invertebrates all enjoy a place on its menu. It does not discriminate or play favorites. Coming upon much younger and smaller larvae of its own kind, it does not hesitate. Its hunger must be placated, even to the point of cannibalism. There is no moral choice to make. The choice is survival, pure and simple.
With winter fast approaching, the larva continues to gorge. Plump and sated, it burrows deep into the mud to avoid the frost, hunkering down until late spring or summer of the following year. It is June when our firstborn emerges to enjoy another season of foraging and feasting. Many of its sisters and brothers from the brood are entering their next stage of metamorphic existence; but for our select one, the time isn’t quite right for this important transition. Its life of fossorial predation continues through the year, as it prepares to overwinter yet another cold season as a larva.
Now two years into its life, the time has finally come for our larva to enter the next stage of its existence. It is August of the current year. Coming to the surface, it seeks a warm, safe place in which to begin the process of transforming itself from larva to pupa. In this new, transcendent state of slumber, our chosen one is slowly reborn, emerging at last from its pupal case as a young adult female greenhead fly.
Our young adult greenhead fly, Tabanus nigrovittatus, looks out onto a previously unseen world through a pair of large compound eyes. Having among the largest eyes in the insect world, this is what gives the fly its characteristic “green head” appearance. Once her wings are dry, she instinctively takes flight into the deep blue summer sky. She now has a new mission and purpose in life that supplants all that went before: to mate and propagate her species by laying as many eggs over the course of her short adult lifespan as possible. This will mean laying one to two egg batches per week, each numbering up to 1,000 eggs, over the next three to four weeks. This is all the time nature has given her. Finding a male fly with which to mate is her first task. This is not difficult. The male flies are ready and waiting.
The first batch of eggs comes easily. As a new adult female fly, she had emerged from her pupa case with a built-in reserve of protein sufficient to guarantee a successful first batch, supplemented with a normal diet of nectar giving her the energy she needs to subsist. However, for the next and all subsequent batches, she would have to change her diet. In addition to nectar, she would need a good source of protein to guarantee the eggs’ proper development. For her next batch of eggs, then, she would choose to feed on the blood of an animal. Her preference: the blood of a warm-blooded animal: a horse, cow, deer…or man.
Our young tabanid greenhead—let’s call her “Tabby”—now ventures out beyond the boundary of her marsh home for the first time in pursuit of a warm meal of blood. An adjoining pasture provides a promising hunting ground. Her keen eyes are attracted by the movement of a large, dark object lumbering across the field. Zeroing in on the object, Tabby picks up the scent of carbon dioxide contained in the exhaled breath of her intended prey. This excites her all the more, driving and directing her toward her target. She is soon joined by scores of others of her kind, all bent on a similar mission.
Suddenly, one among them is snatched out of the air in mid-flight. Tabby looks on as the struggling fly is carried away in the clutches of a slightly larger flying intruder, a black insect with yellow markings on its abdomen. The struggling soon ends as the venom from the insect’s sting takes deadly effect. It is the horse guard wasp, patrolling the green pasture in search of greenheads to take back to its nest to feed its own hungry brood.
But Tabby manages to elude this flying predator and at last alights on the hind quarters of the large beast. She is about to make her mark when…swoosh…like a giant broom she and others are knocked aside by the swish of the giant beast’s tail. Persistent in her pursuit, she targets another, safer area: the soft, inner pink flesh of the large beast’s ears. Unlike other bloodsucking insects like mosquitoes, which are equipped with sharp, slender proboscides for surreptitiously puncturing the victim’s skin, our greenhead must take a more direct—call it primitive—approach to bloodletting. Her mouthparts, like tiny, serrated scimitars, tear and rip into the animal’s flesh, producing a flow of blood which she quickly laps up. The ear of the beast flicks nervously; the beast whinnies, then shakes its large shaggy head, but the fly is not so easily dissuaded. Maintaining her grip, she continues gorging herself on the warm, red, oozing liquid. Only when fully satisfied does she fly away, quickly distancing herself from her victim and retreating back into the safe damp domains of her marsh home.
The next egg batch follows within a few days of this meal. A bonus brood of 900 eggs! Nice job, Tabby! But there is no celebrating and precious little time for rest. In a day or two she is again in search of a meal of warm blood. This time she will lie in wait, allowing the meal to come to her.
It is a warm, sunny day in mid-September. She chooses a shady spot by the side of the marsh road leading to the bay. It is mid-afternoon. A large, dark object approaches from a distance down the road. Slowing down, it comes to rest by the side of the road not far from Tabby. Her senses are alerted by the warm abundance of carbon dioxide belching forth from the rear end of the now still object. A second object emerges from the first. This one has all the markings of a favored life form and a source of warm blood. The greenhead takes flight, quickly sizing up her prey. Approaching from behind, she targets a bare patch of warm, sweaty flesh at the nape of the neck, just above the blue polo shirt covering her prey. With surgical precision she alights and makes her strike. Unlike her first prey, this flesh is much softer, with little hair covering to impede her efforts. This time she goes deep, gouging out an especially large pocket of flesh from her victim. The blood oozes profusely, surprising even the fly. Urgently, she laps up the nourishment before her victim can react to the pain of the bite. She makes a quick escape, just as the heavy hand of her victim strikes back. It’s a clean getaway!
“Son-of-a-bitch!” the man in the blue polo shirt snapped as he slapped the back of his neck with his right hand. “One of those damn greenhead flies got me real good!”
Author’s Note:
The greenhead fly (Tabanus nigrovittatus) easily vies with the Jersey mosquito as the most pernicious of blood-sucking, disease carrying pests indigenous to South Jersey. Just ask any fisherman who has frequented the bays and inland waterways of this fertile region. With only minor modifications, this article was excerpted from my novel, Greenwich: The Final Project. The “greenhead” plays a pivotal role in the story. You might say it is the chief antagonist and nemesis of my main character, John Weston.