In our neck of the woods... Horseflies

This is the time of the year when giant horseflies are everywhere, looking for a blood meal. Seriously, these puppies are over an inch long, quite large for a fly. The males are nice, docile eaters of pollen and nectar from flowers, but the females are demons from the apocalypse.

You think I'm exaggerating? Then you haven't been chomped by an inch-long female horsefly. It hurts, and here's why: Mosquitoes drill a nice clean hole in your skin, then drink your blood through a straw—not very painful. Horseflies (and the smaller deer flies, for that matter) have mouthparts that act like a pair of serrated knives. They slide these back and forth, making a gash in your skin so they can slurp up the blood that comes out. They have anticoagulants in their saliva, which keeps the blood flowing.

On humans, though, the knife-sawing business is so painful that we usually curse, then swat at the fly while doing an awkward horsefly dance. Therefore, the fly doesn't have a chance to get much of a blood meal, so it continues buzzing around, hoping for another opportunity for a knife attack.

Now here's the real reason why I'm talking about horseflies today. Trish and I have noticed, as we drive our vehicles down the one-mile gravel road from our house to the nearest paved road, numerous horseflies attack our cars, chasing us and slamming into our windows and hoods, even when we are going twenty miles per hour. We got to wondering, why do horseflies do this, especially once they try to bite the car and presumably realize it will not provide any blood?

As it turns out, horseflies are irresistibly drawn to large, dark, moving objects (an evolutionary advantage for a critter that feeds on mammals). But it's more than that. Horseflies are attracted to polarized light when searching for animals to bite and for water (where they lay their eggs). Sunlight reflected off a car, particularly a dark-colored car, is polarized. When the car is moving, these factors together drive the horseflies crazy, and they will follow a car for miles as if possessed.

Horseflies are awesome, but they're also vicious.

Photo Credit:
- Horsefly - DepositPhotos