Greenhead Horse Flies

Everything you ever wanted to know about greenhead flies

and were not afraid to ask!

They are setting the record straight on these misunderstood monsters of the marsh!

  • What ARE the little buggers, anyway?
    Meet Tabanvs nigrovittatus, otherwise known as the greenhead fly. This type of biting fly is light brown and can be easily identified by its bright green eyes.
Maximilian Paradiz from Merida, Mexico – Greenhead Horse-Fly
CC BY 2.0

Created: 18 June 2009

  • Where on earth did they come from?
    Greenhead flies reproduce in coastal marshes throughout the eastern United States, ranging from southern Canada to east Texas.

  • How much longer will they be here? When will they ever go away?

    Greenhead season varies from June through September, with fly numbers generally peaking from mid-July to early August.

  • Why are they biting me?
    Only female greenheads bite! They use blood as a source of protein to lay their eggs.
  • How do I ward them off? Is there any escape?
    Fear not, gentle reader. You can do many things to prevent becoming a greenhead’s next meal!

    • Stay covered – the surest way to eliminate a greenhead attack is to wear long sleeves, pants, and a hat. Throw a light layer over your bathing suit – the less skin you show them, the less opportunity they have to bite you!
    • Dry off after being in the water- the flies are attracted to salt water and sweat.
    • Wear light colors – female greenheads are attracted to dark colors. Greenhead traps are black for a reason!
    • Avoid strong-smelling sprays, perfumes, deodorants, and hair products – these odors can attract greenheads.
    • Close car windows -don’t let distracting greenheads cause an accident.
    • Time your visit – Greenheads are most active from 10 AM to dusk and their numbers peak from mid-July to early August.

  • Does bug repellant work against them?
    Some people report having moderate success with various bug sprays. But generally, if greenheads want to bite you, they’ll still bite you!
  • What are those black boxes lining the road approaching the refuge?
    They are greenhead traps. Greenheads are drawn to the underside of the box as they would be to the soft belly of an animal. They fly through a slit in the bottom and can’t orient themselves to fly out again.
  • Can’t we just kill them all? What good could they possibly be?
    The refuge does not use traps or controls on greenheads because they are part of the marsh ecosystem and a linia very integrated food chain. Large numbers of greenheads are a sign of a healthy salt marsh! Greenhead adults and larvae provide food for birds, crustaceans, anfish, while the predacious larvae eat other insect species and keep them in check. Both males and females also serve as pollinators when they feed on flower nectar. Though they are the scourge of eastern beachgoers, greenheads are here to stay!


This information is from the Parker River National Wildlife Refuge.


Enjoy this blog? Please spread the word :)