Those Darn Greenhead Flies

Dated: 09/09/2016

Views: 3964

If you’ve been to coastal south Jersey, you know what I’m talking about here. They have huge iridescent green eyes, land soft, and bite hard. If the wind is out of the west for more than twenty-four hours, they can ruin the beach, and if you are out in your boat, they land in swarms with horrid intent.



These delightful creatures are known as the greenhead fly, the greenhead horse fly, the salt marsh green head, and maybe even the spawn of Satan. In more scientific terms, meaning Genus and Species, they are known as “Tabanus nigrovittatus” and were first classified by the French Entomologist, Justin Pierre Marie Macquart, in 1847. They are commonly found around the coastal marshes of the Eastern United States. Only the females bite and they do not discriminate between humans and animals as they seek a source of blood.


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The females live for three to four weeks and may lay up to 200 eggs per blood meal. The eggs are microscopic black dots and perpetuate the line of the host. When the flies are first born, they are actually vegetarians and feed primarily on nectar or honeydew, but once the female lays the first round of eggs, her entire behavior changes. She becomes extremely aggressive as she needs blood to produce another batch of eggs. The female bites by lacerating the host’s skin with her mandibles after a sensor has determined the source to be warm-blooded. Once the host’s skin is lacerated, the female salivates into the wound releasing an anticoagulant so the blood doesn’t clot. It’s this saliva, which is a foreign protein recognized by our body, that causes the pain as an alert.


The greenheads are strong flyers. If they can’t find a meal at the beach, they can fly for several miles inland until a good target is located. In a west wind, the greenheads fly across the bay, a distance measured in miles, to feast on locals and tourists without discrimination. Traps are set up in marshy areas – large black boxes that to the greenhead can resemble animals. The greenheads enter the trap from the bottom, and are unable to figure out how to fly down to escape. These traps have been known to capture upwards of a thousand green heads per hour.


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The good news is the greenhead fly is only a nuisance, as in the bites hurt, then swell, then itch, and so on. However, the greenhead does not carry AIDS, nor Lyme disease, nor Zika virus. It also plays an important role in the ecosystem as they are a food source for shorebirds and fish. The only protection is for one to wear light clothing, because unlike the mosquito, the greenhead can’t bite through fabric, and when you swat, swat hard, fast, and accurately – because if you miss, you’ve just become responsible for another round of eggs and another two hundred greenheads!


From your “Running Realtor” Andrew Gonzales…

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