The horse fly is a terror that anyone who has ever experienced their bite will remember instantly. In this article, we talk about five interesting facts that many people may not know about this flying menace.

1. The Bite of Horse Flies Can Cause Disease in Humans

The primary concern from horse fly bites for humans is a post-bite infection. The horse fly’s mouth is a scissor-like apparatus. It is a precise tool that pierces the skin, spreads outwards severing capillaries. The result is an upwelling of blood. The saliva of the horse fly contains an anticoagulant. Once bitten the blood flow from a bite does not stop immediately. The female flies need a blood meal to finish their ovulation. Infect from a bite site is not specifically from the horse fly but from other bacteria, fungi, or virus.

In certain species of livestock, such as sheep, the bite from the horse fly can transfer Elaeophora schneideri, which is a nematode or arterial worm. The potential disease for livestock includes elaeophorosis commonly referred to as filarial dermatitis. In sheep, we call the disease sorehead. In elk, it can lead to blindness and is aptly named clear eye blindness. This is not a pleasant disease as symptoms include necrotic tissue in the muzzle region, including the ears tissue. Optic nerve damage can also occur as can severe problems with balance, even death.

For a small percentage of humans, the bite from the horse fly may lead to allergic disease as your body may react to the anticoagulant in the fly’s saliva.

Horse flies are no joke. Their bite is not only painful but dangerous, especially to livestock.

2. The Horse Fly Larva are Highly Aggressive Carnivores

To understand the horse fly larvae as a predator, consider that the that their mouth design allows them to grasp and tear at their prey. Not only are they not interested if their prey escapes, but they will eat “it” while it is still alive. In addition to being predacious, they are cannibalistic too. Targets include earthworms, other insect larvae, millipedes, and even small fish.

3. Many Species of Horse Fly are immune to Pesticides

We have tried many ways to eradicate horse flies and almost every one of those “ways” has failed. We killed off the weaker horseflies because we have done a poor job of using pesticides. What remains is pretty much horse flies that are immune to many pesticides. One type of control that works well is the Fly Cage — a horse fly trap. The trap uses all this predatory insect’s natural tendencies against it.

4. Horse Flies Hunt By Sight

Walk through a shady glen during horse fly season and it won’t take long for that stinging, painful bite to occur. The design of horse flies eyes allow them to detect and track movement. They wait in ambush for big mammals to wander along. Movement attracts them and big animals make easy targets. The flies do not have perfect vision as compared to many mammals, but they see movement just fine. They are also attracted to how we smell and carbon dioxide. As we breathe we emit carbon dioxide. That is one reason why the Fly Cage works so well. It mimics the movement of large animals, such as horses, elk, deer, and sheep. That movement draws the horse flies in where they become trapped and die.

5. Despite All the Terror, Horse Flies have Beautiful Eyes

Maybe a bit mesmerizing — those eyes, but they appear in beautiful shades of greens, ambers, and even red. They often have shapes in them in hues of purple and gold. As beautiful as their eyes are, they are not enough to make up for that horrible bite.

Do you have a fact about horse flies? If so, leave it in the comments below.