What are Horse Flies?

Malcolm Tatum
Malcolm Tatum

Horse flies are a larger and somewhat noisy type of fly that is found in many places around the world. Sometimes known as a gadfly or March fly, the wider family of horse flies include over three thousand different varieties. In some parts of the world, these flies are known for pollinating various types of flora while in other places they are considered no more than a nuisance.

Horse flies are large, noisy, and often a nuisance for horses and their owners.
Horse flies are large, noisy, and often a nuisance for horses and their owners.

One of the more distinguishing features of this fly is the painful bite that is administered by some species. While it is true that many types of flying pests are capable of biting by puncturing the skin with a needle-like protrusion, horse flies are equipped with mandibles shaped with serrated edges. This makes it possible for the fly to actually rip into the skin and slice away a portion of the top layer of flesh. While horse flies tend to feed on the blood that wells up in the wound, they are also capable of slicing off a tiny section of skin and feeding on that severed portion as well.

Flies start out as maggots, like butterflies start out as caterpillars.
Flies start out as maggots, like butterflies start out as caterpillars.

As with many other insects, these flies tend to strike and then remove themselves from the site of the attack as quickly as possible. This helps to minimize the chances of the fly being caught and killed while feeding. The degree of pain caused by the bites is often enough to distract the victim long enough for the fly to feed and then fly away before any action can be taken.

Horse flies tend to thrive during warm weather. Eggs are usually laid in plants and other vegetation located in a climate that is somewhat moist and where the plants are located over soil with a high moisture content. As the eggs drop from the plants into the wet soil, they are able to feed on organisms found in the soil until the larvae are ready to emerge at pupation.

The easiest way to get rid of horse flies is to deal with the larvae, preventing them from developing into adulthood. However, this is often not possible or practical. While there are some designs for traps and other devices to control the population and activity of horse flies in a given area, protection from the painful bites is more commonly the focus.

One home remedy for warding off the flies is to combine some type of antiseptic mouthwash with a small amount of lemon-scented dish soap. Some recipes call for adding a small amount of lemon-scented ammonia to the concoction. This mixture can be placed in a spray bottle and used to liberally coat surround grass, hedges, plants, and wood or brick walls. However, this spray should never be applied directly to the skin. Using the concoction on the surrounding landscape is often enough to repel the flies and thus minimize or eliminate the chances of receiving a bite.

A horse fly trap is also sometimes helpful. Unlike many other types of traps, the design and function do not rely on luring the horse fly with the use of scent. Instead, some visual element attracts the attention of the flies and entices them to enter the trap. Once inside, the flies cannot escape and will eventually perish from a combination of the temperature inside the trap and a lack of nourishment.

Garbage is a common breeding ground for flies.
Garbage is a common breeding ground for flies.
Malcolm Tatum
Malcolm Tatum

After many years in the teleconferencing industry, Michael decided to embrace his passion for trivia, research, and writing by becoming a full-time freelance writer. Since then, he has contributed articles to a variety of print and online publications, including wiseGEEK, and his work has also appeared in poetry collections, devotional anthologies, and several newspapers. Malcolm’s other interests include collecting vinyl records, minor league baseball, and cycling.

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Discussion Comments


I have found that putting anything oily (I use mineral oil) on your skin keeps away horseflies, black flies, deer flies, and mosquitoes. Apply it like tanning lotion. In fact, tanning oil should work just as well. I theorize that the oil masks your skin and they can't find you.


Does anyone know how to kill horse flies for good? I have a couple of horses and the flies are terrible. I almost feel like we have a horse fly infestation. Any ideas would be helpful.


@ Highlighter- We have horseflies where I live and they can be quite the nuisance in spring and early summer. Our local horse flies bite very hard and they are about the size of a small roach. They are easy to spot though (gray with a little red), and they do not usually swarm.

When I encounter them I usually only come across one or two at a time. I find them most often in fields with tall grass or at the edge of the woods. They are the worst when the local farmers are harvesting the hay. The cutting of the grass seems to make the flies agitated, and they will often stray from the fields to the neighboring houses.


Closely related to horse flies are deer flies. I used to live in Vermont and deer flies are everywhere. They deliver a nasty bite that itches like crazy and leaves a big welt. They are persistent too, often biting until you kill them. They are undeterred by insect repellent and much faster than horseflies. The best method for killing them is to let them land on you and then swat them. I certainly do not miss deer flies.

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