As anyone who has visited Plum Island at the height of greenhead season in mid- to late July knows all too well: Greenheads bite.
The greenhead is a largish horsefly with iridescent green eyes, and when it bites, you know it. The greenhead feeds by using its sharp, serrated jaws to rip away a patch of skin to draw your blood. The bite leaves a nasty, itchy welt.
And they sometimes attack in swarms.
Greenheads aren’t unique to Plum Island, of course. You’ll find them at virtually any Northeast beach, including Salisbury and Hampton and sandy shores as far north as Maine and as far south as Cape Cod and New Jersey.
But where else are they written into the national anthem?
“I am a Plum Islander; Plum Island is my home/When greenhead flies fill the skies, no one walks alone,” goes one verse of the “Plum Island National Anthem.”
The humorous ditty was written 40 years ago or so, when Plum Islanders joked (or half-joked) about seceding from the mainland.
At the time, greenheads were far more numerous than today. They’re still a painful nuisance. On bad greenhead days, the Parker River National Wildlife Refuge posts warning signs at the entrance gate. Some visitors turn right around.
But the population of the biting flies has been greatly reduced by the invention — not long after the anthem was written — of the greenhead fly trap.
The trap is a large black wooden box atop four legs. Placed in the salt marshes where the flies breed, the traps take advantage of a greenhead weakness.
The flies are genetically wired to attack the dark underbelly of four-legged creatures, like cattle and horses, where they are harder for their prey to defend against. It’s why, if you’re sitting on the beach, they’ll go straight for the back of your legs.