Your Complete Guide to Different Flies

This article is part of our Fight the Flies Awareness Campaign brought to you by UltraShield.

Horse with lots of fly in face

A small but mighty creature, the fly comes in different varieties and species. You might not encounter tsetse flies (Glossina) outside of Africa, for example, but Trypanosoma, a disease agent transmitted by that notorious pest, inflicts neurological damage in other regions as well, thanks to horse flies (Tabanidae), known for their large size and painful bite, and stable flies (Stomoxys).

Stable Fly

The stable fly is a common pest with blood-feeding tendencies, he goes for horses’ lower legs, resulting in a lot of stomping (and loosened shoes, to boot). Pity the poor lame horse who cannot even manage a stomp to rid himself of this devil! This stomping and kicking can result in injury, leg wounds, or hoof damage.

Black Fly

The black fly or “buffalo gnat” (Simuliidae) is a nearly universal tormentor, as are the 800-plus species of Culicoides, otherwise known by rather innocuous-sounding nicknames like “midges,” “punkies” and “no-see-ums.” Though they’re tiny, all of these mini flies pack a wallop, carrying disease organisms, parasitic worms, and the potential for allergic dermatitis.

Black flies typically transmit Vesicular Stomatitis or VS. When the fly population starts to swell, the disease starts transmitting. The flies that carry the virus are often found around water—outbreaks seem to occur closer to rivers or other bodies of water. There’s some speculation that mosquitos may also carry the virus.

VS is a virus that can affect cattle, sheep, goats, and any number of animals—including humans. This year horses are the species most impacted; there’s also been one case of VS in cattle. While the disease can have an economic impact when cattle contract it, with horses the virus is generally only an inconvenience. Commonly confused with the importance of equine herpes virus, VS will cause your horse discomfort but rarely death.

Lesions can appear on a horse’s coronary bands, in the ears, mouth, nose, tongue, sheath, or udder. If your horse exhibits symptoms, don’t panic! This virus is merely an inconvenience to horse owners. Call your vet as soon as you notice lesions. If your horse does have VS, the entire barn will be under quarantine for two weeks.

Horn Flies, Warbles, and Bots, Oh My!

The blood-sucking horn fly (Haematobia irritans) infests the cooler regions of both northern and southern hemispheres but is generally only a nuisance to horses if they’re pastured near cattle. Then there are the warble fly (Hypodermatidae) and the bot fly (Gasterophilus intestinalis and G. hemorrhoidalis), which flourish in just about all climates. The bot fly has the audacity to lay its eggs right on a horse’s coat, generally on the legs. So, when a horse licks his legs, he ingests the eggs, after which they mature into larvae in the horse’s stomach lining.

Bot-fly larvae can wreak havoc in your horse’s stomach lining, causing significant swelling and ulceration. Large infestations can even lead to colic. The larvae originate as sticky little yellow eggs deposited on your horse’s legs and sides by the female bot fly (which resembles a bumblebee in action). The first hard frost of the season will kill off the flies, making it a great time to administer a dewormer effective against bot larvae. If you then take action to remove any remaining eggs from your horse’s haircoat, you’ll complete your protection plan.

In Your Face

Anywhere there are horses, you’ll also find the face fly (Musca autumnalis), which feeds on eye and mouth secretions, posing risks to the eyes. Then you have the house fly (M. domestica), which favors horse manure, facial secretions and wounds. If you’re “down under,” torturing duties fall to their continent-specific relative, the Australian bush fly.

[Teach Your Horse to Stand For Fly Spray]

Painful Biters

Last but not least is the vicious deer fly, of the genus Chrysops/ family Tabanidae, with its trademark banded wings. It’s the female of this species that is known for its stinging, cross-shaped incisions, which enable it to drink blood. Usually encountered in wooded or wet, low-lying areas, the deer fly is as much a scourge to cattle, wildlife and humans as it is to horses. In the same family is the horse fly. Horse flies are usually larger than their counterparts, and easy to spot. They are attracted to movement, especially dark, large objects. Their bites are painful, and they often lie in wait in wet or shady areas.

For such tiny creatures, flies wield an inordinate amount of power, often sending horses into stampedes or causing them to rear, kick out or stand in ponds for hours in order to escape them. Protect your horse from these pests by practicing good fly management, using an effective fly spray, and fly sheets or masks when necessary.

Find a fly spray that works with your climate and location, to protect your horse from flies. Photo courtesy of UltraShield.
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