Tabanidae Family

Horsefly Facts

A pest to humans and animals alike, the notorious Horsefly is infamous for it unforgiving bite and thirst for mammal blood. However, while this pest shows no sign of extinction, there are a few things to know that may prove helpful in avoiding a bite and loss of blood. Although the horsefly has a general family name – Tabanidae­ – it is difficult to distinguish past that point, as there are several varieties (almost 5,000) of the horsefly all over the world. The only places they do not inhabit are the most extreme north and south latitudes where temperatures are too cold for them to thrive. In the United States alone there are over 20 varieties of the Horsefly (Dove). Despite the differences, each variance has similar characteristics and habits.

The most distinguishing trait of the Horsefly is the eyes; they will be larger than a normal horsefly and be exceedingly colorful (generally a green). The wings, depending on the specific species, will be a solid color (black or clear). Generally the fly will be about 1 inch long (though it can range between ¾ and 1 ¼ inches). The female is always considered the most dangerous as they must feed on blood in order to reproduce; the male does not drink blood at any time.

Horsefly Habitat

One of the most vital things to remember about the Horsefly is its habitat; they are creatures of habit and enjoy certain climates and conditions. If these conditions are not met they are less likely to be a pest problem. From the larvae stage into adulthood, the fly has a preference for moist, humid areas and is attracted to warm water. Any small marshlands or swampy areas on private land should be drained to prevent further hatching and nests. Understandably, many wetlands and similar environments are not available for draining; this will require the use of insecticides for pest control.

In the US, Horseflies are the most prevalent during the summer as the females love wetlands, but also are attracted to warmth. Throughout the rest of the world the Horsefly is seen year round in areas like Africa and the Southeast Asia where there is constant warmth and humidity. These areas play host to more species of the Horsefly and are generally more susceptible to the diseases that the Horsefly can carry.

Horsefly Life Cycle

As mentioned above, the Horsefly females make their nests along the banks of rivers or marshy streams. The egg count ranges greatly depending on the type of Horsefly and area; batches can be anywhere from under 50 to over 1000. These counts are consistent with wetland sites and while some Horseflies have been known to breed in dry lands the egg numbers are much smaller.

Once hatched the larvae will fend for themselves in the mud or riverbank feeding on decay and organisms such as snails and worms.

Horsefly Food Source

As larvae, both male and female Horseflies will feed on other organism, but once they reach adulthood this similarity stops. Male Horseflies are not considered pests because they do not feed on mammals. Females, on the other hand, are a bit more treacherous. In order to lay eggs the female Horsefly requires blood in her diet. As reproduction is inbred into the fly, the female will go to great lengths to feed on human or other mammal blood. According to some reports, the female is also capable of feeding on birds or amphibians.

Horsefly Bites

You won’t have to wonder if a Horsefly has bitten you; you will just know. Depending on the species, the Horsefly will either rip the flesh or stick in a needle-like mouth to consume as much blood as possible. The female Horsefly is an “intermittent feeder,” meaning that the fly moves from host to host and does not become permanently latched like a tick, The Horsefly is a known carrier of diseases such as sleeping sickness and swamp fever.

Horseflies as Pests

Although small, these Horseflies pose a serious threat to livestock as well as humans. If a bite does turn to an allergic reaction it should be tended to immediately to reduce the risk on further infection. While an individual Horsefly may not take a significant amount of blood in one sitting; a swarm of constantly feeding Horseflies can result in up to 1 quart of blood lost each day.

Horsefly Control

  • One of the most suggested types on insecticide for Horseflies is a Permethrin-based spray. The only problem is that the flies are not exposed long enough to the insecticide to actually kill them and, therefore, the spray must be applied several times a day
    • Pay particular attention to hard to reach areas (abdomen). Although they may be a difficult reach for you, the flies will have no problem reaching them.
  • Other than insecticides, the only other options are preventative.
    • Keep your livestock in barns during the day and let them out to graze during the night when the Horseflies are not prevalent.
  • Humans should wear insect repellent and possibly even mesh clothing if they are going to be working in marsh areas. The protective clothing will detract the flies and prevent any bites and infections.