Greenhead Fly
Tabanus nigrovittatus · Also known as: greenhead, salt marsh greenhead
July’s infamous beach-day biter. Big green-eyed horse flies emerge from Assateague salt marsh and hunt the ocean beach on calm, hot afternoons.
Quick facts
| Group | Mosquito / biting fly |
|---|---|
| Likelihood nearby | ★★★★☆ |
| Habitats | Salt marsh, Ocean beach, Dunes, Coastal bays, Assateague State Park, Assateague National Seashore, Inlet |
| Seasons (this coast) | summer |
How to recognize them
- Robust fly about bee-sized with bright green eyes (live) and dark patterned wings.
- Silent approach compared with buzzing house flies; painful bite when it lands on ankles and shoulders.
Biology notes
- Larvae develop in marsh substrate; adults are strong fliers that track movement and carbon dioxide.
- Females blood-feed for egg production; males nectar on flowers and are less bothersome.
Where to see them around Ocean City
- Ocean City and Assateague ocean beaches on hot July and August afternoons with little wind.
- Ferry landings and marsh-adjacent parking lots at high tide.
- Bay beaches when marsh breeze is calm.
When to look
- Peak July–August; mid-day sun and low wind are worst.
Viewing tips & etiquette
- Ocean breeze is free defense—sit upwind of the dunes when greenheads are reported.
- Light-colored clothing and repellents labeled for biting flies help; swatting alone rarely wins.
