Greenheads | Learn about Greenhead Flies, the Beasts of the Northern Wild
The wild serenity of the salt marsh stretches from Maine to Florida. It is a world caught between worlds, a lovely transitional swath of emerald grass that snakes along the Atlantic coastline, occupying a territory somewhere between sea and solid ground.
This line of demarcation between solid and liquid is neither and both. The ground of the salt marsh is springy, like walking on a lumpy trampoline. Water oozes up through tufts of matted grass, potholes lurk beneath seemingly solid ground.
Who inhabits this spongy world? Apart from the occasional deer, there are turtles, assorted birds, mice, and, once in a while, a rabbit, a raccoon, or an otter, mostly just passing through. Which means it’s slim pickings for one small, hungry inhabitant, whose appetite revs into high gear ’round about mid-July.
Like ripening fruit at the moment of perfection, Tabanus nigrovittatus emerges from the salt marsh at summer’s midpoint. She has just laid her first batch of eggs. Two hundred or so microscopic dots, but who’s counting, because right now she’s out of her mind with hunger, and it’s time to get down to the business at hand. Her first blood meal. Ever. In her young adult life she’s never had a solid meal, subsisting mostly on nectar, preferring to wait until the whole egg-laying business is behind her. By doing so, she ensures that the precious bloodline will continue, that the next generation of greenhead horseflies–as she is more commonly known–will be born. But right now she’s paying the price. And there’s not a thing to eat.
A stone’s throw from the unearthly beauty of the salt marsh, some of the great New England beaches sprawl beside the Atlantic, baking in the sun: Crane Beach, in Ipswich; Plum Island, off the coast of northeastern Massachusetts; Hammonasset Beach, unfurling along the Connecticut side of Long Island Sound. A brilliant blue sky stretches overhead; a faint breeze ruffles the grasses. Perfect beach weather. A great day to fly. Her dazzling green eyes casting about, she makes a beeline for the water. The sand up ahead is swarming with warm, scantily clothed bodies, fairly bursting with reservoirs of succulent human blood.
“Greenheads,” says the blond boy barricaded in the entrance booth at Hammonasset Beach State Park. He slides open a window and points to a squashed bug taped to the side of the building. “They’re pretty bad today. You may want to think about it.”
Given the size and spread of the flattened insect, “pretty bad” seems like a PR understatement. The little torpedo is more than half as long as my thumb, and even mashed up it’s easy to imagine hordes of greenheads making for the beach like vacationers racing to claim their patch of sand. Like most beachgoers, tabanids prefer warm, sunny days, and it is, of course, an especially beautiful July morning, without even a hint of breeze. The sun is already fierce, the distant sand shimmers with promise, and the sea is as blue as the Aegean.
But a face-off with greenheads? Their size makes them fairly immune to bug repellent, and slathering on DEET isn’t a very appealing option. Do I want to spend a day swatting these things? I squint at this poster child for a bad day at the beach, weighing the pros and cons. In full knowledge that at this very moment, a similar scenario is playing out, up and down the East Coast. Cars backing up, just as I’m about to do, turning around and heading home. Or at the very least, somewhere far from the coastal salt marshes.
And that’s when I get curious.
What’s up with this bug? Clearly it’s a robust type of horsefly (the name is a tip-off), and it certainly outweighs its relative the deerfly, although both biters belong to the same fly family, Tabanidae. And “greenhead” obviously refers to its enormous green eyes, laced with bands of iridescent red or purple.
But above and beyond these physical characteristics, and the fact that greenheads will indiscriminately attack horses, cows, dogs, hogs, and deer, this fly is notorious mainly for one thing: the pain it inflicts in large numbers on beachgoers at the height of summer. Make that two things, because like The Terminator, this fly is relentless. It will not stop until someone pays the price.
Stories of encounters with greenheads have a dramatic quality usually reserved for plays written by one-name ancient Greeks. But the blunt truth is that these creatures can ruin a day, or days, at the beach.
Often during peak greenhead season–generally early or mid-July to mid-August–beaches will post warnings about fly conditions, like some weird variation on the surf report. At Crane Beach there’s another sign, too: No Refunds. But it’s not about singling out one beach or another; any gathering spot near a salt marsh–beach, restaurant, or home–is potentially vulnerable. Sometimes it’s just a matter of degree.
“All salt marshes on Cape Cod provide habitat for greenhead flies,” says Gabrielle Sakolsky, entomologist and assistant superintendent at the Cape Cod Mosquito Control Project. “Our largest marshes, adjacent to the large barrier beaches of Sandy Neck and Nauset, are the worst, because they have the largest amount of larval habitat. There are no immune spots.”
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