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Greenhead Flies | What are Greenheads?

Greenhead Flies | What are Greenheads?
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Come mid-July in, the dreaded greenhead flies — commonly known as greenheads — descend upon the beaches of New England. Learn more about these hungry, bloodsucking flies that are fierce enough to destroy vacation plans in one swoop.

Greenhead flies, named for their large, bright green eyes, can be found in the coastal marshes of Eastern North America. Unfortunately for us, that means they love New England’s beaches.  Knowing about these pests can help you plan your next beach trip the safe way – away from the painful bites of greenhead flies.

Greenheads | What are greenhead flies?
Closeup photo of a greenhead horsefly. Greenhead flies | What are greenheads?

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.

Greenheads | What are greenhead flies?
Photo/Art by Bill Mayer
Beasts of the Northern Wild | Greenhead Flies

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 flies–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 greenhead flies 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 greenhead flies? 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.

Please Note: This information was accurate at the time of publication. When planning a trip, please confirm details by directly contacting any company or establishment you intend to visit.

Annie Graves


Annie Graves


Annie Graves is a regular contributor to Yankee. A New Hampshire native, she has been a writer and editor for over 25 years, while composing music and writing young adult novels. Find out more about Annie at
Updated Monday, July 15th, 2013

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10 Responses to Greenhead Flies | What are Greenheads?

  1. Kathy Woinson July 12, 2014 at 12:58 pm #

    Great article I just read as I had to retreat to indoors because of how vicious the greenheads are today. I thought that they arrived on the new moon the end of June & were gone by the full moon high tide in July, which is tonight! Guess maybe that’s not true, maybe it’s the full moon in August?? Sure is a miserable few weeks and they certainly are nasty bighters!! Very informative article though,

    • Arvo August 1, 2015 at 11:26 pm #

      Greenies are in season from the first full moon in July through the next full moon. This is an odd case wherein the Hebrew calendar, based on lunar cycles, always works — with greenhead season starting out on the 15th of the month of Tammuz and ending on the 15th of Av. If it is extremely hot weather I have seen them come out a few days early, but by that second full moon — 15th of Av — they are all done.

  2. Helen Rankin August 4, 2014 at 8:41 am #

    I go to Cape Cod and some days green flies make it unbearable on Nauset Beach. Then we have Plovers nesting resulting in the closure of the beaches. It’s maddening!!

    • Michelle August 6, 2014 at 11:29 am #

      Hi Helen… Do you know if the green heads are still bad right now? Michelle :)

  3. Laura F. August 26, 2014 at 11:29 pm #

    I live in South Jersey and the only thing that works for me 100% no greenheads is…when the wind blows from the East (off the ocean). This keeps them at bay, literally. Lol
    The absolute worst time to go to the beach between June-September is when the wind blows from the West (off the land).
    I believe you’ll be fine with little to no flys if it blows from other directions too. IF the wind changes from the West while your there, a few flys MAY appear but leave right when it changes again.
    Since I live close enough to the beach to drive down for a day trip, I just check my Weather App the day before and morning of to see which direction the wind is blowing. I guess for those of you who go to the beach for more than one day on vacation, this method won’t help you that much.
    In that case, I’ve heard from many people that Avon’s Skin So Soft works as a repellent…I think they even have a bug repellent that’s water resistant with SPF 30, and anti-itch relief.

  4. Elizabeth June 23, 2015 at 8:39 pm #

    Just read the article. I hate these flies more than anything! They ruin our summers here in Newbury, Ma. The island referenced above is not Pine Island, but Plum Island. The greenheads near our home are horrible, and they have started early this year. We usually don’t see them for another couple weeks. :(

    • Big Yaz September 21, 2015 at 9:34 pm #

      It’s Pine Island. Follow Pine Island Road off Route 1A.

  5. Mary Beth July 12, 2015 at 11:57 am #

    Another reason to get a pool.

  6. Rebecca Jay July 15, 2015 at 1:32 pm #

    Spectacular article!!
    I’ve never heard of greenheads.. Read about them in a book & googled it.
    I found this article there. At first, I was tempted to move on because I was just looking for more info on them..habitat, photos, etc.
    However, this article was so well written I had to keep reading..all 4pages!
    Nicely done, Ms. Annie Graves!!

  7. Kerry murphy July 22, 2015 at 2:33 pm #

    Living right next to a salt marsh with a pool,we are not able to use the pool the last two weeks in July each year due to these mini monsters. We actually go to the beach because they aren’t bad there. I wish these researchers could invent a safe repellent that works.

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