Horse Flies

Photo of a horse fly
Example of a Horse Fly
Combination of two photos; each photo is a closeup image of a Horse Fly
Horse Flies (additional examples)

Horse flies (genus Tabanus) are very pesky flies of not only humans, but also other mammals such as cattle, horses, dogs, etc.  This is due to the fact that the females of most species require a blood meal in order to reproduce effectively, if at all, and although some species are known to feed on birds or reptiles, the majority of them feed on mammalian blood.  The bite is often quite painful, resembling a bee sting for many people, and a lot of people react to the fly’s saliva, causing pain and itching at the site of the bite.  Significant allergic reactions can develop for some people.

Photo of a horse fly on a person's hand (biting or preparing to bite)
A horse fly biting or preparing to bite

Horse flies are very similar to deer flies, which share the same family (Tabanidae).  One way to tell them apart is to look at their overall size, and their wings.  Horse flies tend to be much larger (from three-quarters of an inch to an inch or more in length), with a stout body and a very large head with very large eyes, and their wings are usually clear whereas deer flies have dark bands across their wings.  Both horse flies and deer flies are abundant in damp, wooded and wetland environments, which provide the necessary habitat for their eggs and larvae.  Natural predators of horse flies and deer flies include such things as frogs, toads, spiders, wasps, hornets, dragonflies, and birds.

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