Are the Greenheads here yet? Are they bad this year? What are those black boxes we see in the Marsh? Why are those little guys so vicious?
Every year we here at
Parker River National Wildlife Refuge get hundreds of calls asking us about the infamous greenhead fly. Named for their giant green eyes, beach goers and birders alike often find them intolerable. They sneak up, they swarm, and ouch they bite, but they are really very important to our ecosystem.
The greenhead fly (Tabanus nigrovittatus) is a cousin to the black flies and horse flies that you might be more familiar with. Having hatched and developed quietly in the salt marshes they reach adulthood around mid July each year then, they emerge into marsh and beach habitats feeding until to early August. While adult greenheads only live those 3-4 weeks, the females make good work of consuming blood in that time to help with the production of anywhere from 300-6000 eggs a year. And they don’t do it gracefully like other blood sucking insects. Female greenheads tear out a chunk of skin and lap up the blood with their tongues.
Don’t want to be greenhead food? There are a few things you can do to help yourself. The first thing to know is that greenheads tend to swarm if you are in your car, or sitting on the beach. Some think this is because they are attracted to quadrupeds (animals with four legs). In other words, greenheads see your car (with it’s four tires) or you sitting close to the ground and confuse you with their favorite meals. Wearing dark colors also seems to draw them close, so don your light summer colors when heading out to green head territory. Keep your car windows closed because they will come inside. Greenheads don’t move very quickly when it is cooler, so if you are going for a walk, make it early in the day. After that we recommend that you fend off greenhead as you would any other biting or stinging insects. Stay away from sweet smelling perfumes and deodorants, where long sleeves and pants, put on bug spray, and don’t forget your hat.
Why don’t we just kill them you ask? Well, some people do. Those black boxes you see in marsh lands are actually green head traps. The green heads are drawn to them because they have four legs and are dark in color. (Like those quadrupeds we mentioned before.) They fly under them trying to bite their bellies, but the boxes are hollow inside (opening on the bottom.) When the greenheads fly in looking for a snack, most of them aren’t quite smart enough to get back out.
Here at the refuge we do not use green head boxes. While we are getting bitten too, we understand that those pesky flies play a very important role in our ecosystem. Many animals such as birds, crabs and even fish depend on them as an important source of food in the springtime. Without the greenheads many of these animals would be forced to look somewhere else for food and we would miss their presence even more than one might predict.
Mary R Carpenter
Park Ranger – Visitor Services Specialist
Parker River National Wildlife Refuge
